Synthetic studies on novel benzimidazolopeptides with antimicrobial, cytotoxic and anthelmintic potential

European Journal of Medicinal Chemistry 42 (2007) 772e798

http://www.elsevier.com/locate/ejmech

Original article

Synthetic studies on novel benzimidazolopeptides with antimicrobial,

cytotoxic and anthelmintic potential

*

Rajiv Dahiya , Devender Pathak

Department of Pharmaceutical Chemistry, Rajiv Academy for Pharmacy, NH#2, DelhieMathura Bypass Road,

PO Chattikara, Mathura 281 001, Uttar Pradesh, India

Received 22 May 2006; received in revised form 30 November 2006; accepted 30 November 2006

Available online 15 December 2006

Abstract

Four substituted benzimidazolyl-benzoic/salicylic acids 5e8 were synthesized by interaction of 5,6-dimethyl-/6-nitrobenzimidazoles with

diazotized substituted/unsubstituted aminobenzoic acids in the presence of cupric chloride. The coupling of compounds 5e8 with different

amino acid ester hydrochlorides/dipeptide/tripeptide/tetrapeptide methyl esters afforded novel benzimidazolopeptide derivatives 5aef, 6aeh,

7aeg and 8aeg. The structures of all newly synthesized compounds were established on the basis of analytical, IR, ¹H NMR, ¹³C NMR

and mass spectral data. Selected peptide ester derivatives were further hydrolyzed by using lithium hydroxide (LiOH) to yield corresponding

acid derivatives 5b_aed_a, 6e_aeg_a, 7c_aee_aand 8e_aeg_a. All peptide derivatives were screened for their antimicrobial, anthelmintic and cytotoxic

activities. Almost all newly synthesized benzimidazolopeptides have shown moderate to good anthelmintic activity against all three earthworm

species and good antimicrobial activity against pathogenic fungal strains Candida albicans and Aspergillus niger, gram negative bacterial strains

Pseudomonas aeruginosa and Escherichia coli. Compounds 8g and 8g_apossessed signiﬁcant cytotoxic activity against Dalton’s lymphoma

ascites (DLA) and Ehrlich’s ascites carcinoma (EAC) cell lines.

Keywords: Benzimidazoles; 5-Aminosalicylic acid; p-Aminobenzoic acid; Peptides; Antimicrobial activity; Anthelmintic activity; Cytotoxicity

1. Introduction

indicating antimicrobial and molluscicidal [12], cytotoxicity

[13], prooxidant and antioxidant [14], anti-inﬂammatory and

analgesic [15] potential of substituted benzoic acid analogs,

in addition to inhibitory activity against aldose reductase,

inﬂuenza neuraminidase, 3a-hydroxysteroid dehydrogenase,

phosphodiesterase (4D), steroid 5a-reductase isozymes 1 and

2, homomeric kainate receptor, histamine H₁receptor and

estrone sulfatase [16e23].

Prompted from the chemotherapeutic importance of benz-

imidazoles and benzoic acid derivatives, these two vital moie-

ties were combined together into single nucleus by varying

the substitution pattern on both the moieties to yield 4-(5,6-di-

methyl-1H-benzo[d]imidazol-2-yl)-benzoic acid 5 and 4-(5,

6-dimethyl-1H-benzo[d]imidazol-2-yl)-3,5-diiodobenzoic acid

6, 2-hydroxy-5-(6-nitro-1H-benzo[d]imidazol-2-yl)-benzoic

acid 7 and 5-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-2-hy-

droxybenzoic acid 8.

In past decades, benzimidazole and its derivatives have

received much attention due to their chemotherapeutic value

in the development of novel anthelmintics and antimicrobial

agents [1e3]. Benzimidazole analogs also possessed other

pharmacological activities such as antiallergic [4], antimyco-

bacterial [5], inhibitory activity of human blood platelet aggre-

gation [6], antiviral [7], antiprotozoal and antimalarial [8],

anti-inﬂammatory, analgesic and kinase, DHFR inhibitory

activity [9,10], antitumoral and tracheal relaxant activity [11].

Moreover, the literature is enriched with several reports

* Corresponding author. Tel.: þ91 565 6531680, +91 9897417450 (mobile).

E-mail addresses: rajivdahiya77@rediffmail.com, rajivdahiya04@yahoo.

co.in (R. Dahiya).

doi:10.1016/j.ejmech.2006.11.015

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

773

In view of the reported activity of amino acid/peptide de-

rivatives of heterocyclic aromatic compounds [24e27] and

in continuation of our earlier work on synthesis of benz-

imidazole derivatives of amino acids and peptides [28,29],

an attempt was made towards the synthesis of four novel

series of benzimidazolopeptides, 4-(5,6-dimethyl-1H-ben-

zo[d]imidazol-2-yl)-benzoyl amino acid/peptides 5aef and

4-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-3,5-diiodobenzoyl

amino acid/peptides 6aeh, 2-hydroxy-5-(6-nitro-1H-benzo

[d]imidazol-2-yl)-benzoyl amino acid/peptides 7aeg and 5-

(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-2-hydroxybenzoyl

amino acid/peptides 8aeg, respectively. Selected peptide de-

rivatives were further hydrolyzed to get corresponding acid

derivatives 5b_aed_a, 6e_aeg_a, 7c_aee_aand 8e_aeg_a. Antimicro-

bial, anthelmintic and cytotoxic activity results of such

novel heterocyclic peptide derivatives are also discussed.

acid/peptide conjugates 7aeg and 8aeg, respectively. Further-

more, amino acid/peptide derivatives 5bed, 6eeg, 7cee and

8eeg were hydrolyzed by stirring with LiOH to yield corre-

sponding acid derivatives 5b_aed_a, 6e_aeg_a, 7c_aee_aand 8e_ae

g_a(Fig. 1). All the newly synthesized peptide derivatives

were characterized by spectral and elemental analyses

(Table 1).

3. Biological activity studies

All the newly synthesized peptide derivatives 5ae8g_awere

evaluated for their antibacterial, antifungal, anthelmintic and

cytotoxic activity. The antimicrobial activities are carried out

against four bacterial strains Bacillus subtilis (NCIM 2063),

Staphylococcus aureus (NCIM 2079), Pseudomonas aerugi-

nosa (NCIM 2034), Escherichia coli (NCIM 2065) according

to modiﬁed KirbyeBauer disc diffusion method [34] and four

fungal strains Candida albicans (MUCC 29), Microsporum au-

douinii (MUCC 545), Trichophyton mentagrophytes (MUCC

665), Aspergillus niger (MUCC 177) according to serial plate

dilution method [35]. Ciproﬂoxacin and griseofulvin were

used as standard drugs against bacterial and fungal strains at

10 mg mL^ꢀ1concentration. MIC values of test compounds

were determined by tube dilution technique [36]. The results

of antimicrobial activity are summarized in Table 2. The anthel-

mintic activity was carried out against the three earthworm spe-

cies Megascoplex konkanensis (ICARBC 211), Pontoscotex

corethruses (ICARBC 408) and Eudrilus sp. (ICARBC 042)

by Garg and Atal method [37] at concentration of 2 mg mL^ꢀ1

using mebendazole as standard drug. The results of anthelmintic

activity are tabulated in Table 3. The cytotoxic activity was car-

ried out against Dalton’s lymphoma ascites (DLA) cells and

Ehrlich’s ascites carcinoma (EAC) cells according to the

method of Kuttan et al. [38] using 5-ﬂuorouacil (5-FU) as stan-

dard drug and the results are presented in Table 4. Moreover,

various physicochemical parameters of selected synthesized

peptide derivatives were calculated using ACD ChemSketch

software and the results of such studies are presented in Table 5.

2. Chemistry

4-Amino-3,5-diiodobenzoic acid 1a was prepared according

to the literature procedure [30] in good yields by iodination of

p-aminobenzoic acid (PABA) using iodine monochloride.

Benzimidazole was nitrated using nitrating mixture by standard

procedure [31] to afford 6-nitrobenzimidazole 1b. Dipeptides

Boc-Leu-Gly-OMe 2a, Boc-His-Tyr-OMe 2b, Boc-Pro-nitro

(Arg)-OMe 2c, Boc-His-Pro-OMe 2d, Boc-Gly-Gly-OMe 2e,

Boc-Pro-Ala-OMe 2f, Boc-nitro(Arg)-Ala-OMe 2g, Boc-His-

His-OMe 2h and Boc-Leu-Ile-OMe 2i were prepared by cou-

pling Boc-amino acids with the respective amino acid methyl

ester hydrochlorides using dicyclohexylcarbodiimide (DCC)

as coupling agent and N-methylmorpholine (NMM) as base ac-

cording to Bodanzsky and Bodanzsky procedure [32] with suit-

able modiﬁcations [33]. The Boc group of all dipeptides was

removed by using triﬂuoroacetic acid (TFA) to obtain dipeptide

derivatives deprotected at the amino terminal 2a⁰ei⁰. Similarly,

tripeptides Boc-Pro-Pro-Phe-OMe 3a, Boc-Ala-Tyr-Gly-OMe

3b, Boc-Phe-Val-Pro-OMe 3c, Boc-Pro-Pro-Pro-OMe 3d,

Boc-Val-Phe-His-OMe 3e, Boc-Trp-Ala-Tyr-OMe 3f, Boc-Ala-

Val-Ala-OMe 3g and tetrapeptides Boc-Trp-Gly-Ile-Ala-OMe

4a, Boc-Gly-Ile-Gly-Thr-OMe 4b, Boc-His-Pro-Leu-Gly-

OMe 4c, Boc-Gly-Trp-Gly-His-OMe 4d were synthesized

by coupling Boc-dipeptides with respective amino acid methyl

ester hydrochlorides/dipeptide methyl esters in alkaline condi-

tions. On treatment with TFA, all tri and tetrapeptides afforded

tripeptide 3a⁰eg⁰and tetrapeptide 4a⁰ed⁰derivatives with free

amino group. Compound 5 and its diiododerivative 6 were pre-

pared by interaction of diazotized solution of PABA/1a with

5,6-dimethylbenzimidazole in the presence of aqueous cupric

chloride. Similarly, compounds 7 and 8 were synthesized by

stirring diazotized solution of 5-aminosalicylic acid with 1b

and 5,6-dimethylbenzimidazole, respectively. Finally, com-

pounds 5 and 6 were coupled with different amino acid methyl

ester hydrochlorides and dipeptide/tripeptide/tetrapeptide

methyl esters by using DCC/triethylamine (TEA) in THF to

get peptide derivatives 5aef and 6aeh, respectively. Similarly,

coupling of compounds 7 and 8 with different peptide methyl

esters in the presence of DCC/NMM in DMF afforded amino

4. Results and discussion

The newly synthesized compounds were analyzed for C, H

and N content and structures were conﬁrmed by IR, ¹H NMR,

¹³C NMR and mass spectral data. Results of elemental analy-

ses revealed the variation by a factor of ꢁ0.04 from calculated

values. Coupling reaction was accomplished and conﬁrmed by

appearance of bands of medium to strong intensity at 1663e

1627 cm^ꢀ1(amide I band, C]O str.) and 1536e1520 cm^ꢀ1

(amide II band, NeH def.) in IR spectra of all Boc-di/tri/tetra-

peptide methyl esters 2aei, 3aeg and 4aed. Deprotection at

amino terminal was indicated by disappearance of singlets at

t

1.55e1.50 ppm (for nine protons of butyl group) in ¹H

NMR spectra, peaks at 157.2e152.3, 80.9e79.7 and 27.5e

26.8 ppm (for carbonyl carbon of Boc group and a-, b-carbons

t

of butyl group of Boc) in ¹³C NMR spectra of compounds

2a⁰ei⁰, 3a⁰eg⁰and 4a⁰ed⁰.

774

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

COOH

OH

I

ICl

COOH

NH₂

COOH

NH₂

1a

I

0°C

NaNO₂, dil. HCl

0°C

NaNO₂, dil. HCl

R₁

COOH

OH

+

-

N⁺

Cl^-

COOH

N

Cl

N

R₂

N

HNO₃

N

H₂SO₄

N

H

N

H

NO₂

1b

H₃C

N

OR

Aq. CuCl₂

R₁

H₃C

N

H

N

H

H₃C

COOH

OH

R₃

N

COOH

N

R₄

N

H

5, 6

R₂

7, 8

H-X-OMe

DCC, TEA

H-X-OMe

R₁

DCC, NMM

N

H₃C

CO-X-OMe

R₃

N

CO-X-OMe

OH

N

H

N

H

R₄

R₂

5a-f, 6a-h

7a-g, 8a-g

LiOH

R₁

LiOH

CO-X-OH

OH

H₃C

R₃

N

CO-X-OH

N

H

N

H

R₄

R₂

5b_a-d_a, 6e_a-g_a

7c_a-e_a, 8e_a-g_a

R₁= R₂= H, I ; R₃= H, CH₃; R₄= NO₂, CH₃

X = Amino acids / Dipeptides / Tripeptides / Tetrapeptides

Fig. 1. Synthesis of amino acid and peptide derivatives of 4-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-benzoic acid 5, 4-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-

3,5-diiodobenzoic acid 6, 2-hydroxy-5-(6-nitro-1H-benzo[d]imidazol-2-yl)-benzoic acid 7 and 5-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-2-hydroxybenzoic

acid 8.

Presence of two aromatic rings in structures of compounds

5e8 was conﬁrmed by strong out-of-plane deformation bands

(CeH bending) at 886e820 cm^ꢀ1in their IR spectra. Moreover,

presence of NO₂group in compound 7 was indicated by appear-

ance of medium bands at 1540 and 1349 cm^ꢀ1(asymmetric and

symmetric NO₂stretching) in IR spectra whereas presence of

iodine atoms in compound 6 and its peptide derivatives was

indicated by appearance of bands of medium intensity at

602e588 cm^ꢀ1(CeI str.) in IR spectra.

as bases in THF and DMF, respectively. IR spectra of peptide

derivatives 5ae8g showed amide I and amide II bands at

1668e1622 cm^ꢀ1and 1548e1522 cm^ꢀ1, indicating formation

of peptide bonds and successfulness of coupling reaction. This

fact was further conﬁrmed by the appearance of broad singlets

at 9.98e6.25 ppm (for imino proton of COeNH moiety) in ¹H

NMR spectra and singlets at 175.3e163.6 ppm (for carbonyl

carbon of COeNH moiety) in ¹³C NMR spectra of compounds

5ae8g. Mass spectra of peptide ester derivatives showed mo-

lecular ion peaks along with isotopic peaks at m/z values, con-

sistent with their respective molecular formulas. All peptide

All peptide derivatives 5ae8g_awere synthesized in good

yields by utilizing DCC as coupling agent, TEA and NMM

Table 1

Characterization data of compounds 5ae6g_a

Compound

R₁

R₂

R₃

R₄

X

Mol. formula (mol. wt.)

M.p. (^ꢂC)

Yield (%)

R_Mvalue^a

Analysis, %found (calcd.)

C

H

N

5a

5b

5c

H

I

H

I

e

Pro

C

₂₂H₂₃N₃O₃(377)

C₂₃H₂₇N₇O₅(481)

₂₅H₃₀N₄O₄(450)

C₃₂H₃₂N₆O₅(580)

144e145

160e161

128e129

116e117

137e138

173e174

122e123

109e110

99e100

76

72

69

72

79

73

71

74

72

80

76

79

73

67

72

69

74

71

74

68

ꢀ0.7533 ꢁ 0.0207

ꢀ0.6585 ꢁ 0.0062

ꢀ0.8860 ꢁ 0.0113

ꢀ0.5247 ꢁ 0.0028

ꢀ0.0696 ꢁ 0.0127

ꢀ0.3075 ꢁ 0.0486

ꢀ0.3474 ꢁ 0.0085

ꢀ0.6886 ꢁ 0.0032

ꢀ0.3273 ꢁ 0.0118

ꢀ0.3888 ꢁ 0.0076

ꢀ0.3474 ꢁ 0.0110

ꢀ0.0173 ꢁ 0.0079

ꢀ0.5496 ꢁ 0.0047

ꢀ0.0521 ꢁ 0.0200

ꢀ0.2880 ꢁ 0.0059

ꢀ0.9079 ꢁ 0.0107

ꢀ0.4542 ꢁ 0.0476

ꢀ0.2126 ꢁ 0.0124

ꢀ0.1401 ꢁ 0.0092

ꢀ0.6585 ꢁ 0.0724

69.98 (70.01)

57.35 (57.37)

66.59 (66.65)

66.24 (66.19)

69.54 (69.55)

66.17 (66.18)

56.49 (56.52)

66.05 (66.04)

65.69 (65.71)

41.28 (41.28)

46.80 (46.82)

39.85 (39.83)

40.48 (40.50)

43.85 (43.88)

45.19 (45.22)

49.41 (49.39)

43.29 (43.27)

43.10 (43.10)

44.49 (44.52)

48.77 (48.80)

6.15 (6.14)

5.68 (5.65)

6.74 (6.71)

5.56 (5.55)

6.30 (6.32)

6.37 (6.41)

5.42 (5.39)

6.55 (6.47)

5.36 (5.34)

3.15 (3.16)

3.39 (3.37)

3.31 (3.34)

4.02 (3.88)

3.70 (3.68)

3.83 (3.79)

4.50 (4.49)

4.44 (4.45)

3.50 (3.48)

3.59 (3.61)

4.33 (4.33)

11.09 (11.13)

20.37 (20.36)

12.40 (12.44)

14.44 (14.47)

11.28 (11.26)

13.79 (13.85)

21.01 (20.97)

12.82 (12.84)

14.88 (14.83)

10.49 (10.46)

7.79 (7.80)

Nitro(Arg)

Leu-Gly

His-Tyr

C

5d

5e

Pro-Pro-Phe

Trp-Gly-Ile-Ala

Nitro(Arg)

Leu-Gly

C

₃₆H₃₉N₅O₅(621)

₃₉H₄₅N₇O₆(707)

5f

5b_a

5c_a

5d_a

6a

6b

6c

C₂₂H₂₅N₇O₅(467)

C₂₄H₂₈N₄O₄(436)

C₃₁H₃₀N₆O₅(566)

His-Tyr

His

C

₂₃H₂₁I₂N₅O₃(669)

218e219

262e263

201e202

225e226

197e198

282e283

254e255

259e261

188e189

269e270

210e211

I

Trp

Thr

C₂₈H₂₄I₂N₄O₃(718)

C₂₁H₂₁I₂N₃O₄(633)

I

6.65 (6.64)

6d

6e

I

Pro-(nitro)Arg

His-Pro

C

₂₈H₃₂I₂N₈O₆(830)

₂₈H₂₈I₂N₆O₄(766)

13.52 (13.49)

10.99 (10.97)

8.55 (8.51)

I

6f

I

Ala-Tyr-Gly

Phe-Val-Pro

Gly-Ile-Gly-Thr

His-Pro

C₃₁H₃₁I₂N₅O₆(823)

₃₆H₃₉I₂N₅O₅(875)

6g

6h

6e_a

6f_a

6g_a

I

C

7.98 (8.00)

9.70 (9.77)

I

C₃₁H₃₈I₂N₆O₇(860)

C₂₇H₂₆I₂N₆O₄(752)

C₃₀H₂₉I₂N₅O₆(809)

C₃₅H₃₇I₂N₅O₅(861)

I

11.21 (11.17)

8.66 (8.65)

8.12 (8.13)

I

Ala-Tyr-Gly

Phe-Val-Pro

I

Characterization data of compounds 7ae8g_a

7a

7b

7c

e

H

NO₂

CH₃

Nitro(Arg)

Trp

Gly-Gly

C₂₁H₂₂N₈O₈(514)

C₂₆H₂₁N₅O₆(499)

C₁₉H₁₇N₅O₇(427)

C₂₃H₂₃N₅O₇(481)

C₃₀H₃₂N₆O₈(604)

C₃₅H₃₆N₈O₈(696)

C₃₄H₃₉N₉O₉(717)

C₁₈H₁₅N₅O₇(413)

C₂₂H₂₁N₅O₇(467)

C₂₉H₃₀N₆O₈(590)

C₂₆H₂₅N₃O₄(443)

C₂₆H₃₂N₈O₇(568)

C₂₉H₃₀N₈O₅(570)

C₂₉H₃₈N₄O₅(522)

C₄₀H₄₀N₆O₇(716)

C₂₈H₃₅N₅O₆(537)

C₃₈H₃₉N₉O₇(733)

C₃₉H₃₈N₆O₇(702)

C₂₇H₃₃N₅O₆(523)

C₃₇H₃₇N₉O₇(719)

170e171

159e160

125e126

196e197

168e169

175e176

202e203

108e109

185e186

152e153

210e211

222e223

196e197

188e189

174e175

250e251

244e245

160e161

229e230

202e203

86

81

88

89

82

91

83

92

81

89

80

85

89

79

91

90

82

85

80

ꢀ0.1224 ꢁ 0.0118

ꢀ0.9542 ꢁ 0.0200

ꢀ0.4101 ꢁ 0.0037

ꢀ0.4771 ꢁ 0.0229

ꢀ0.1580 ꢁ 0.1104

ꢀ0.0871 ꢁ 0.0048

ꢀ0.2688 ꢁ 0.0102

ꢀ0.3679 ꢁ 0.0140

ꢀ0.4319 ꢁ 0.0083

ꢀ0.1760 ꢁ 0.0071

ꢀ0.1224 ꢁ 0.0221

ꢀ0.0347 ꢁ 0.0109

ꢀ0.8653 ꢁ 0.0063

ꢀ0.0871 ꢁ 0.0094

ꢀ0.1942 ꢁ 0.0173

ꢀ0.5247 ꢁ 0.0428

ꢀ0.1047 ꢁ 0.0221

ꢀ0.4102 ꢁ 0.0113

ꢀ0.2311 ꢁ 0.0038

ꢀ0.6886 ꢁ 0.0192

48.99 (49.03)

62.50 (62.52)

53.45 (53.40)

57.40 (57.38)

59.59 (59.60)

60.35 (60.34)

56.89 (56.90)

52.27 (52.30)

56.52 (56.53)

58.96 (58.98)

70.45 (70.41)

54.95 (54.92)

61.05 (61.04)

66.66 (66.64)

66.98 (67.03)

62.50 (62.55)

62.16 (62.20)

66.61 (66.65)

61.92 (61.94)

61.75 (61.74)

4.29 (4.31)

4.25 (4.24)

3.98 (4.01)

4.85 (4.82)

5.35 (5.33)

5.20 (5.21)

5.50 (5.48)

3.65 (3.66)

4.55 (4.53)

5.12 (5.12)

5.64 (5.68)

5.67 (5.67)

5.28 (5.30)

7.32 (7.33)

5.64 (5.62)

6.57 (6.56)

5.35 (5.36)

5.49 (5.45)

6.36 (6.35)

5.15 (5.18)

21.71 (21.78)

13.98 (14.02)

16.40 (16.39)

14.49 (14.55)

13.93 (13.90)

16.05 (16.08)

17.55 (17.56)

16.95 (16.94)

15.01 (14.98)

14.20 (14.23)

9.47 (9.47)

H

7d

7e

H

Pro-Ala

H

Pro-Pro-Pro

Val-Phe-His

His-Pro-Leu-Gly

Gly-Gly

7f

H

7g

7c_a

7d_a

7e_a

8a

8b

8c

H

Pro-Ala

Pro-Pro-Pro

Phe

H

CH₃

(Nitro)Arg-Ala

His-His

Leu-Ile

19.69 (19.71)

19.65 (19.64)

10.72 (10.72)

11.75 (11.72)

13.06 (13.03)

17.20 (17.18)

11.99 (11.96)

13.42 (13.38)

17.50 (17.51)

8d

8e

Trp-Ala-Tyr

Ala-Val-Ala

Gly-Trp-Gly-His

Trp-Ala-Tyr

Ala-Val-Ala

Gly-Trp-Gly-His

8f

8g

8e_a

8f_a

8g_a

a

R_M¼ log[(1/R_f) ꢀ 1]; data are given as mean ꢁ S.D. (n ¼ 3).

776

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

Table 2

Antimicrobial activity data

Compound

Diameter of zone of inhibition (mm)

Bacterial strains

Fungal strains

B. subtilis

S. aureus

P. aeruginosa

E. coli

C. albicans

M. audouinii

A. niger

T. mentagrophytes

5a

5b

13 (6)

14 (12.5)

10 (6)

14 (6)

13 (12.5)

14 (6)

15 (12.5)

13 (6)

16 (6)

20 (6)

17 (6)

14 (6)

15 (6)

16 (6)

15 (6)

16 (6)

17 (6)

13 (6)

12 (6)

9 (25)

13 (12.5)

14 (6)

13 (6)

14 (6)

9 (25)

13 (12.5)

14 (6)

15 (6)

13 (6)

15 (6)

13 (12.5)

13 (6)

12 (6)

16 (12.5)

14 (6)

e

11 (12.5)

9 (25)

22 (6)

23 (6)

20 (6)

19 (12.5)

20 (6)

25 (6)

23 (6)

23 (12.5)

24 (6)

25 (6)

23 (6)

27 (6)

24 (6)

20 (6)

22 (12.5)

22 (6)

27 (6)

23 (6)

24 (12.5)

19 (6)

20 (12.5)

22 (6)

28 (6)

27 (6)

24 (12.5)

24 (6)

22 (6)

28 (6)

24 (6)

22 (6)

21 (6)

20 (6)

21 (6)

19 (6)

23 (6)

22 (6)

21 (6)

24 (6)

e

17 (12.5)

14 (12.5)

15 (25)

16 (6)

15 (12.5)

18 (6)

16 (12.5)

16 (6)

19 (25)

17 (12.5)

19 (6)

17 (12.5)

18 (6)

19 (6)

23 (6)

16 (6)

15 (6)

16 (6)

13 (12.5)

25 (6)

16 (6)

17 (6)

15 (12.5)

20 (6)

18 (6)

22 (6)

24 (6)

19 (6)

20 (6)

18 (6)

22 (6)

24 (6)

17 (6)

19 (12.5)

20 (6)

19 (6)

17 (6)

18 (6)

17 (6)

18 (6)

19 (6)

20 (6)

e

9 (25)

8 (12.5)

10 (25)

8 (25)

17 (12.5)

15 (12.5)

16 (25)

13 (6)

12 (12.5)

12 (6)

13 (6)

9 (25)

14 (12.5)

14 (6)

16 (6)

12 (12.5)

12 (6)

10 (6)

12 (6)

13 (12.5)

12 (6)

9 (25)

13 (6)

15 (12.5)

13 (6)

15 (6)

17 (6)

15 (6)

17 (6)

17 (12.5)

13 (6)

15 (6)

16 (6)

17 (6)

17 (12.5)

15 (6)

10 (6)

15 (6)

13 (6)

14 (6)

15 (6)

16 (6)

e

5c

5d

9 (12.5)

10 (12.5)

8 (25)

16 (12.5)

14 (12.5)

19 (25)

5e

16 (25)

9 (25)

10 (6)

5f

5b_a

10 (12.5)

11 (25)

18 (12.5)

19 (12.5)

17 (12.5)

17 (25)

10 (12.5)

11 (25)

10 (25)

11 (25)

9 (12.5)

8 (25)

16 (12.5)

17 (25)

5c_a

5d_a

10 (12.5)

11 (12.5)

12 (12.5)

13 (12.5)

12 (12.5)

11 (12.5)

12 (12.5)

12 (25)

17 (12.5)

14 (12.5)

19 (25)

6a

6b

18 (12.5)

19 (12.5)

16 (12.5)

18 (12.5)

17 (12.5)

16 (25)

6c

6d

15 (12.5)

14 (25)

10 (25)

9 (25)

6e

13 (12.5)

15 (12.5)

14 (12.5)

18 (25)

6f

6g

9 (12.5)

10 (12.5)

9 (25)

6h

6e_a

12 (12.5)

13 (12.5)

13 (25)

17 (12.5)

18 (12.5)

18 (25)

10 (25)

11 (12.5)

13 (6)

14 (12.5)

15 (12.5)

18 (12.5)

16 (12.5)

17 (12.5)

16 (12.5)

17 (12.5)

19 (25)

6f_a

6g_a

7a

7b

10 (25)

15 (12.5)

16 (12.5)

18 (12.5)

17 (25)

12 (12.5)

9 (12.5)

9 (25)

10 (12.5)

13 (6)

12 (6)

7c

7d

7e

11 (12.5)

10 (12.5)

9 (12.5)

9 (25)

13 (6)

7f

7g

16 (12.5)

14 (12.5)

16 (12.5)

18 (12.5)

17 (25)

12 (12.5)

12 (6)

13 (6)

17 (12.5)

16 (12.5)

17 (12.5)

18 (12.5)

17 (12.5)

19 (25)

7c_a

7d_a

12 (6)

13 (6)

7e_a

8a

11 (12.5)

10 (12.5)

11 (12.5)

10 (12.5)

9 (25)

17 (12.5)

16 (12.5)

16 (25)

9 (25)

11 (6)

8b

8c

11 (6)

12 (6)

8d

8e

11 (12.5)

10 (6)

16 (12.5)

15 (12.5)

17 (12.5)

16 (12.5)

e

8f

8g

9 (12.5)

11 (12.5)

11 (25)

17 (12.5)

18 (12.5)

17 (25)

8e_a

8f_a

12 (12.5)

11 (6)

8g_a

10 (12.5)

e

18 (12.5)

e

Control

Ciproﬂoxacin

Griseofulvin

e

20 (6)

e

20 (12.5)

e

25 (6)

e

19 (12.5)

e

20 (6)

e

17 (6)

e

18 (12.5)

e

20 (6)

Values in bracket are MIC values (mg mL^ꢀ1).

ester derivatives showed easily distinguishable ReC^O^þion

peaks at M ꢀ 31 along with characteristic fragmentation pat-

tern after and before the carbonyl moiety in their respective

structures. Furthermore, [CH₃O^þ] and [CH₃OCO^þ] fragment

ion peaks appeared at m/z values 31 and 59 in mass spectra

of compounds 5ae8g. Peptide derivatives of compounds 5, 6

and 8 showed characteristic fragment ion peaks at m/z value

146 (5,6-dimethylbenzimidazole ion e [C₉H₁₀N₂]^þ) which

dissociated into [C₈H₉N]^þion by loss of HCN, appeared at

m/z value 119 which further dissociated into [C₈H₈N]^þion

by loss of hydrogen radical, appeared at m/z value 118. Similar

pattern of fragmentation appeared in case of amino acid/

peptide derivatives of compound 7, characteristic fragment

ion being 6-nitrobenzimidazole ion e [C₇H₅N₃O₂]^þ, which

dissociated into [C₆H₄N₂O₂]^þand [C₆H₃N₂O₂]^þions by loss

of HCN and hydrogen radical, appeared at m/z value 136

and 135, respectively.

Structures of hydrolyzed derivatives 5b_aed_a, 6e_aeg_a, 7c_ae

e_aand 8e_aeg_awere conﬁrmed by appearance of strong bands

at 1716e1705 cm^ꢀ1(C]O str. COOH) in IR spectra, broad

singlets at 9.72e9.80 ppm (for hydroxyl proton of COOH)

in ¹H NMR spectra and singlets at 182.2e173.2 ppm (for car-

bonyl carbon of COOH) in ¹³C NMR spectra. This fact was

further supported by disappearance of medium to strong bands

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

777

Table 3

Anthelmintic activity data

Compound

Earthworm species

M. konkanensis

P. corethruses

Eudrilus sp.

Mean paralyzing

time (min)^a

Mean death

time (min)^a

Mean paralyzing

time (min)^a

Mean death

time (min)^a

Mean paralyzing

time (min)^a

Mean death

time (min)^a

5a

5b

28.38 ꢁ 0.52

18.56 ꢁ 0.98

28.34 ꢁ 0.59

13.68 ꢁ 1.12

36.78 ꢁ 0.21

13.25 ꢁ 0.44

18.15 ꢁ 0.52

26.29 ꢁ 0.89

13.54 ꢁ 0.83

29.28 ꢁ 0.67

13.04 ꢁ 0.93

35.23 ꢁ 1.56

17.93 ꢁ 0.80

13.73 ꢁ 1.90

28.35 ꢁ 0.43

27.25 ꢁ 0.14

36.10 ꢁ 0.23

13.65 ꢁ 1.56

27.23 ꢁ 0.24

26.42 ꢁ 0.45

16.22 ꢁ 0.37

13.09 ꢁ 1.44

27.67 ꢁ 0.17

26.26 ꢁ 1.46

25.48 ꢁ 0.82

10.45 ꢁ 2.20

11.28 ꢁ 0.62

27.08 ꢁ 0.45

26.14 ꢁ 1.12

25.09 ꢁ 0.49

26.22 ꢁ 0.67

16.74 ꢁ 0.28

10.52 ꢁ 0.86

25.50 ꢁ 0.34

13.66 ꢁ 0.32

25.56 ꢁ 0.46

9.44 ꢁ 0.56

13.43 ꢁ 0.67

25.23 ꢁ 0.23

9.32 ꢁ 0.87

e

40.58 ꢁ 0.59

26.56 ꢁ 0.45

41.40 ꢁ 0.84

22.59 ꢁ 0.72

62.48 ꢁ 0.91

22.52 ꢁ 1.43

26.29 ꢁ 0.76

40.27 ꢁ 0.92

22.18 ꢁ 1.28

45.46 ꢁ 0.28

22.28 ꢁ 0.71

59.23 ꢁ 0.88

26.34 ꢁ 0.77

22.73 ꢁ 0.49

39.13 ꢁ 0.43

40.35 ꢁ 0.24

65.13 ꢁ 0.92

22.38 ꢁ 2.03

40.57 ꢁ 0.34

41.85 ꢁ 0.67

25.56 ꢁ 0.72

22.46 ꢁ 0.69

36.48 ꢁ 1.95

35.22 ꢁ 0.94

34.12 ꢁ 1.63

19.58 ꢁ 1.08

20.03 ꢁ 1.34

36.05 ꢁ 0.65

35.10 ꢁ 0.51

34.03 ꢁ 1.23

35.54 ꢁ 0.90

25.40 ꢁ 0.84

18.28 ꢁ 1.12

34.12 ꢁ 0.87

22.74 ꢁ 1.53

34.67 ꢁ 0.78

17.49 ꢁ 0.72

22.62 ꢁ 0.21

34.22 ꢁ 0.69

17.36 ꢁ 0.55

e

35.57 ꢁ 1.26

21.65 ꢁ 1.44

37.17 ꢁ 1.88

17.55 ꢁ 0.23

49.35 ꢁ 1.65

17.22 ꢁ 1.24

21.51 ꢁ 1.12

36.61 ꢁ 1.91

17.47 ꢁ 1.47

34.14 ꢁ 1.23

17.10 ꢁ 1.08

40.60 ꢁ 1.33

22.77 ꢁ 1.56

17.52 ꢁ 2.23

34.13 ꢁ 1.31

33.64 ꢁ 0.46

57.67 ꢁ 1.90

17.38 ꢁ 0.33

35.42 ꢁ 1.31

34.13 ꢁ 1.06

20.65 ꢁ 1.25

17.02 ꢁ 0.53

31.38 ꢁ 0.74

31.98 ꢁ 1.17

30.59 ꢁ 1.01

11.87 ꢁ 0.49

13.76 ꢁ 0.51

31.18 ꢁ 0.44

31.90 ꢁ 1.02

30.52 ꢁ 1.55

30.34 ꢁ 1.12

20.38 ꢁ 1.09

12.22 ꢁ 0.77

29.83 ꢁ 1.45

17.60 ꢁ 0.13

29.89 ꢁ 1.22

14.34 ꢁ 0.68

17.02 ꢁ 1.74

29.65 ꢁ 1.87

12.22 ꢁ 0.51

e

50.26 ꢁ 1.02

35.22 ꢁ 1.87

49.40 ꢁ 1.43

29.18 ꢁ 2.17

72.24 ꢁ 1.04

29.57 ꢁ 1.02

34.96 ꢁ 1.04

48.39 ꢁ 0.20

29.02 ꢁ 1.18

47.82 ꢁ 0.78

29.29 ꢁ 0.39

78.32 ꢁ 0.87

34.45 ꢁ 1.86

29.58 ꢁ 1.63

48.24 ꢁ 0.31

50.22 ꢁ 1.22

82.30 ꢁ 0.49

29.33 ꢁ 0.28

47.45 ꢁ 1.76

50.13 ꢁ 1.44

32.22 ꢁ 1.29

29.41 ꢁ 1.28

42.45 ꢁ 1.55

43.76 ꢁ 0.41

40.38 ꢁ 1.03

22.79 ꢁ 0.97

21.72 ꢁ 0.45

42.26 ꢁ 1.12

43.55 ꢁ 0.56

40.20 ꢁ 1.69

42.56 ꢁ 1.40

32.65 ꢁ 1.10

23.75 ꢁ 0.83

41.53 ꢁ 1.67

29.34 ꢁ 0.65

41.79 ꢁ 1.34

26.21 ꢁ 0.54

29.19 ꢁ 1.02

41.60 ꢁ 1.77

24.52 ꢁ 0.86

e

32.25 ꢁ 0.93

18.67 ꢁ 0.82

29.73 ꢁ 0.49

13.49 ꢁ 1.32

32.82 ꢁ 0.58

13.59 ꢁ 0.41

18.38 ꢁ 0.69

32.80 ꢁ 0.85

13.44 ꢁ 0.89

34.34 ꢁ 0.56

13.50 ꢁ 0.81

31.22 ꢁ 1.75

19.43 ꢁ 0.67

13.48 ꢁ 0.59

27.42 ꢁ 0.35

29.24 ꢁ 0.56

38.45 ꢁ 0.88

13.37 ꢁ 1.44

26.25 ꢁ 0.35

27.10 ꢁ 0.83

17.98 ꢁ 0.86

13.37 ꢁ 0.40

25.74 ꢁ 0.65

27.23 ꢁ 0.79

26.67 ꢁ 0.37

11.55 ꢁ 1.02

11.23 ꢁ 1.26

25.50 ꢁ 0.38

27.12 ꢁ 0.61

26.54 ꢁ 0.20

26.78 ꢁ 0.87

17.35 ꢁ 0.49

10.38 ꢁ 1.18

25.69 ꢁ 0.43

13.41 ꢁ 1.40

25.55 ꢁ 0.98

11.06 ꢁ 0.24

13.25 ꢁ 0.83

25.18 ꢁ 0.38

10.89 ꢁ 0.48

e

45.34 ꢁ 1.62

28.21 ꢁ 0.82

42.54 ꢁ 0.93

23.98 ꢁ 0.44

53.34 ꢁ 0.62

24.10 ꢁ 0.60

38.12 ꢁ 0.71

40.24 ꢁ 0.55

23.08 ꢁ 0.38

46.30 ꢁ 0.49

24.02 ꢁ 0.96

69.45 ꢁ 0.78

30.02 ꢁ 0.59

23.98 ꢁ 0.97

45.30 ꢁ 1.13

45.34 ꢁ 0.35

70.54 ꢁ 0.76

23.86 ꢁ 1.21

45.22 ꢁ 1.10

44.10 ꢁ 1.02

28.27 ꢁ 0.81

23.93 ꢁ 1.44

36.77 ꢁ 0.87

35.82 ꢁ 0.48

37.44 ꢁ 1.42

21.72 ꢁ 0.88

20.33 ꢁ 0.53

36.70 ꢁ 0.70

35.69 ꢁ 0.31

37.23 ꢁ 1.69

37.74 ꢁ 0.56

28.54 ꢁ 0.85

21.78 ꢁ 0.58

36.12 ꢁ 0.66

24.07 ꢁ 0.85

36.23 ꢁ 0.45

20.94 ꢁ 1.03

23.98 ꢁ 1.02

36.14 ꢁ 0.69

19.83 ꢁ 0.16

e

5c

5d

5e

5f

5b_a

5c_a

5d_a

6a

6b

6c

6d

6e

6f

6g

6h

6e_a

6f_a

6g_a

7a

7b

7c

7d

7e

7f

7g

7c_a

7d_a

7e_a

8a

8b

8c

8d

8e

8f

8g

8e_a

8f_a

8g_a

Control

Mebendazole

a

13.85 ꢁ 0.64

Data are given as mean ꢁ S.D. (n ¼ 3).

22.90 ꢁ 0.53

17.85 ꢁ 1.03

29.64 ꢁ 1.20

13.54 ꢁ 0.45

24.05 ꢁ 0.62

at 1755e1740 cm^ꢀ1(C]O str. ester) and 1273e1262 cm^ꢀ1

(CeO str. ester) in IR spectra and singlets at 170.4e

168.7 ppm (for carbonyl carbon of C(]O)OCH₃) in ¹³C

NMR spectra of compounds 5b_ae8g_a. All hydrolyzed peptide

derivatives showed peaks at M ꢀ 17 and M ꢀ 45 in their mass

spectra by loss of OH and COOH, respectively. Moreover,

[COOH^þ] fragment ion peak appeared at m/z value 45 in

mass spectra of compounds 5b_ae8g_aalong with characteristic

fragmentation pattern after and before the carbonyl moiety.

Comparison of antibacterial and antifungal screening data

suggested that hydrolyzed peptide derivatives 5b_aed_a, 6e_ae

g_aand 8e_aeg_aare slightly more potent antimicrobial agents

than their corresponding methyl ester derivatives except com-

pounds 7c_aee_awhich are almost as potent as compounds 7ce

e. All peptide derivatives exhibited maximum activity against

gram negative bacteria P. aeruginosa, E. coli and pathogenic

fungi C. albicans, A. niger whereas S. aureus and M. audouinii

are found to be least sensitive bacterial and fungal strains.

Compounds 6d, 6e_a, 7d, 7d_a, 7e and 7e_aare most active which

possessed 8e25% higher activity against P. aeruginosa and C.

albicans in comparison to standard drugs at 10 mg mL^ꢀ1in

DMF and DMSO, respectively. However, compounds 7a

and 8b possessed antifungal activity against A. niger, 5b_a

and 6b showed antibacterial activity against P. aeruginosa

778

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

Table 4

Cytotoxic activity data

Compound

Conc.

(mg mL^ꢀ1

DLA cells

EAC cells

)

b

Live cells

counted

No. of

dead cells

% Growth

inhibition^a

CTC₅₀

(mM)

Live cells

counted

No. of

dead cells

% Growth

inhibition^a

CTC₅₀

(mM)

5d_a

500

250

28

31

30

34

33

10

7

26.31

18.42

21.00

10.52

13.15

25

26

27

3

2

1

10.71

7.14

3.57

125

8

>883.39

84.34

62.5

31.25

4

5

6d

500

250

6

12

18

27

32

26

20

11

6

84.21

68.42

52.61

28.94

15.78

0

28

10

6

100.0

35.71

21.42

125

114

0

62.5

31.25

18

22

6e_a

7d_a

7e_a

7f

500

250

18

22

25

27

33

20

16

13

11

5

52.63

42.10

34.21

28.94

13.15

18

20

25

26

10

8

35.71

28.57

10.71

7.14

125

583.11

>1070.66

322.47

>718.39

>697.35

>877.19

15.32

3

>664.89

>1070.66

>847.46

>718.39

>697.35

>877.19

18.91

62.5

31.25

3

2

500

250

25

28

30

31

35

13

10

8

34.20

26.31

21.00

18.42

7.89

21

23

24

26

7

5

4

2

25.0

17.85

14.28

7.14

125

62.5

31.25

7

3

7.14

500

250

13

18

20

25

31

25

20

18

13

7

65.78

52.63

47.36

34.21

18.42

20

22

25

26

27

8

6

3

2

1

28.7

21.42

10.71

7.14

125

62.5

31.25

3.57

500

250

22

27

28

30

34

16

11

10

8

42.10

28.94

26.31

21.00

10.52

25

26

27

3

2

1

10.71

7.14

3.57

125

62.5

31.25

4

7g

500

250

23

26

29

32

36

15

12

9

39.47

31.57

23.68

15.78

5.26

20

22

25

26

27

8

6

3

2

1

28.7

21.42

10.71

7.14

125

62.5

31.25

6

2

3.57

8c

500

250

24

26

30

32

35

14

12

8

36.84

31.57

21.00

15.78

7.89

22

24

26

27

6

4

2

1

21.42

14.28

7.14

125

62.5

31.25

6

7.14

3.57

3

8g

62.5

0

5

38

33

21

17

10

100.0

86.84

55.26

44.73

26.32

0

8

28

20

15

10

2

100.0

71.42

53.57

35.71

7.14

31.25

15.63

7.81

17

21

28

13

18

26

3.91

8g_a

62.5

0

38

31

23

17

100.0

81.58

60.52

44.73

0

2

28

26

21

13

3

100.0

92.85

75.0

31.25

15.63

7.81

7

6.15

7

12.00

15

21

15

25

46.43

10.71

3.91

Control

500e62.5

31.25

15.63

7.81

38

0

e

28

0

e

3.91

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

779

Table 4 (continued)

Compound

Conc.

(mg mL^ꢀ1

DLA cells

EAC cells

)

b

Live cells

counted

No. of

dead cells

% Growth

inhibition^a

CTC₅₀

(mM)

Live cells

counted

No. of

dead cells

% Growth

inhibition^a

CTC₅₀

(mM)

Standard (5-FU)

62.5

0

38

28

25

16

100.0

73.68

65.79

42.11

0

28

17

9

100.0

60.71

32.14

17.86

31.25

15.63

7.81

10

13

22

37.36

11

19

23

90.55

3.91

5

a

% Growth inhibition ¼ 100 ꢀ [{(cell_totalꢀ cell_dead) ꢃ 100}/cell_total].

CTC₅₀¼ cytotoxic conc. inhibiting 50% of percentage growth.

b

and E. coli, 7b, 7g, 8c and 8g_aexhibited antifungal activity

against pathogenic C. albicans, 6c possessed antibacterial ac-

tivity against B. subtilis, equal to reference drugs ciproﬂoxacin

and griseofulvin, respectively.

e 37.36 and 90.55 mM (4.86 and 11.78 mg mL^ꢀ1)) whereas

compound 8g exhibited cytotoxicity comparable to standard

drug. Moreover, compound 6d exhibited moderate cytotoxicity

with CTC₅₀values 114 and 84.34 mM (94.63 and 70 mg mL^ꢀ1

,

All peptide derivatives 5ae8g showed moderate to good an-

thelmintic activity at 2 mg mL^ꢀ1in Tween 80 (0.5%) and dis-

tilled water. Comparison of anthelmintic activity data revealed

that hydrolyzed peptide derivatives 5b_ae8g_aare slightly more

active than their corresponding ester derivatives 5be8g. Com-

pounds 7f, 8c, 8g and 8g_aare most activewhich possessed higher

activity against M. konkanensis, P. corethruses and Eudrilus sp.

in comparison to standard drugs and compounds 5d, 5d_a, 5f, 6b,

6e, 6e_a, 7b, 7g and 8e showed anthelmintic activity comparable

to that of reference compounds.

respectively), against both cell lines.

Different steric and lipophilicity parameters for selected pep-

tide derivatives exhibiting signiﬁcant level of activity, were cal-

culated which are needed to describe the intermolecular forces

of drug receptor interaction as well as transport and distribution

of drugs in a quantitative manner. These physicochemical pa-

rameters are standard constant values for newly synthesized

compounds which would be helpful for further extension of

the present work to SAR and molecular modeling aspects.

Cytotoxic activity data revealed that compound 8g_apos-

sessed higher cytotoxic activity with CTC₅₀values 6.15 and

12 mM (4.42 and 8.63 mg mL^ꢀ1, respectively), against DLA

and EAC cell lines as compared to 5-ﬂuorouracil (CTC₅₀value

5. Conclusions

This study reports the successful synthesis of title com-

pounds via coupling reaction in good yields. For peptide

Table 5

Calculated physicochemical parameters for peptide derivatives

Compound

Molar

refractivity

(cm³)

Molar

volume

(cm³)

Parachor

(cm³)

Index of

refraction

Surface

tension

(dyne/cm)

Density

(g/cm³)

Polarizability

(10^ꢀ24cm³)

Partition

coefﬁcient

(log P)

5b

5b_a

5d

5d_a

5f

126.28 ꢁ 0.5^a

121.32 ꢁ 0.5

160.97 ꢁ 0.3

156.13 ꢁ 0.3

198.59 ꢁ 0.3

162.69 ꢁ 0.3

132.05 ꢁ 0.3

176.89 ꢁ 0.5

167.38 ꢁ 0.3

162.54 ꢁ 0.3

123.94 ꢁ 0.5

135.65 ꢁ 0.3

118.63 ꢁ 0.3

155.16 ꢁ 0.3

150.31 ꢁ 0.3

184.58 ꢁ 0.3

144.68 ꢁ 0.5

153.50 ꢁ 0.3

200.09 ꢁ 0.3

199.03 ꢁ 0.3

194.19 ꢁ 0.3

340.9 ꢁ 7.0

316.5 ꢁ 7.0

433.8 ꢁ 3.0

408.5 ꢁ 3.0

560.3 ꢁ 3.0

403.9 ꢁ 3.0

345.1 ꢁ 3.0

435.6 ꢁ 7.0

430.1 ꢁ 3.0

404.7 ꢁ 3.0

313.0 ꢁ 7.0

337.5 ꢁ 3.0

306.0 ꢁ 3.0

409.7 ꢁ 3.0

384.4 ꢁ 3.0

502.3 ꢁ 3.0

508.4 ꢁ 3.0

387.3 ꢁ 7.0

405.4 ꢁ 3.0

529.0 ꢁ 3.0

524.2 ꢁ 3.0

498.8 ꢁ 3.0

937.3 ꢁ 8.0

892.7 ꢁ 8.0

1230.9 ꢁ 4.0

1188.2 ꢁ 4.0

1532.5 ꢁ 4.0

1154.9 ꢁ 4.0

973.2 ꢁ 4.0

1240.9 ꢁ 8.0

1250.2 ꢁ 6.0

1206.8 ꢁ 6.0

926.3 ꢁ 8.0

998.9 ꢁ 4.0

923.9 ꢁ 6.0

1216.4 ꢁ 6.0

1173.0 ꢁ 6.0

1437.8 ꢁ 4.0

1481.4 ꢁ 6.0

1076.8 ꢁ 8.0

1184.6 ꢁ 4.0

1505.3 ꢁ 4.0

1519.5 ꢁ 4.0

1476.8 ꢁ 4.0

1.662 ꢁ 0.05

1.692 ꢁ 0.05

1.664 ꢁ 0.02

1.689 ꢁ 0.02

1.626 ꢁ 0.02

1.738 ꢁ 0.02

1.690 ꢁ 0.02

1.746 ꢁ 0.05

1.706 ꢁ 0.02

1.735 ꢁ 0.02

1.722 ꢁ 0.05

1.736 ꢁ 0.02

1.702 ꢁ 0.02

1.681 ꢁ 0.02

1.710 ꢁ 0.02

1.656 ꢁ 0.02

1.646 ꢁ 0.02

1.670 ꢁ 0.05

1.681 ꢁ 0.02

1.680 ꢁ 0.02

1.684 ꢁ 0.02

1.706 ꢁ 0.02

57.1 ꢁ 7.0

63.2 ꢁ 7.0

64.7 ꢁ 3.0

71.5 ꢁ 3.0

55.9 ꢁ 3.0

66.8 ꢁ 3.0

63.1 ꢁ 3.0

65.8 ꢁ 7.0

71.3 ꢁ 3.0

79.0 ꢁ 3.0

76.6 ꢁ 7.0

76.7 ꢁ 3.0

83.0 ꢁ 3.0

77.6 ꢁ 3.0

86.6 ꢁ 3.0

67.0 ꢁ 3.0

72.0 ꢁ 3.0

59.7 ꢁ 7.0

72.9 ꢁ 3.0

65.5 ꢁ 3.0

70.6 ꢁ 3.0

76.8 ꢁ 3.0

1.41 ꢁ 0.1

1.47 ꢁ 0.1

50.06 ꢁ 0.5

48.09 ꢁ 0.5

63.81 ꢁ 0.5

61.89 ꢁ 0.5

78.72 ꢁ 0.5

64.49 ꢁ 0.5

52.35 ꢁ 0.5

70.12 ꢁ 0.5

66.35 ꢁ 0.5

64.43 ꢁ 0.5

49.13 ꢁ 0.5

53.77 ꢁ 0.5

47.03 ꢁ 0.5

61.51 ꢁ 0.5

59.59 ꢁ 0.5

73.17 ꢁ 0.5

57.35 ꢁ 0.5

60.85 ꢁ 0.5

79.32 ꢁ 0.5

78.90 ꢁ 0.5

76.98 ꢁ 0.5

3.41 ꢁ 0.77

3.08 ꢁ 0.78

4.38 ꢁ 0.67

3.96 ꢁ 0.67

5.63 ꢁ 0.84

6.91 ꢁ 0.65

4.75 ꢁ 0.66

3.20 ꢁ 0.93

5.87 ꢁ 0.79

5.40 ꢁ 0.79

3.45 ꢁ 0.81

5.79 ꢁ 0.56

2.21 ꢁ 0.60

5.14 ꢁ 0.74

4.68 ꢁ 0.73

5.57 ꢁ 0.81

4.73 ꢁ 0.86

3.56 ꢁ 0.89

3.30 ꢁ 0.72

6.61 ꢁ 0.78

3.88 ꢁ 0.86

3.46 ꢁ 0.86

1.338 ꢁ 0.06

1.387 ꢁ 0.06

1.263 ꢁ 0.06

1.778 ꢁ 0.06

1.834 ꢁ 0.06

1.90 ꢁ 0.1

6b

6c

6d

6e

1.781 ꢁ 0.06

1.858 ꢁ 0.06

1.64 ꢁ 0.1

6e_a

7a

7b

7d_a

7e

1.479 ꢁ 0.06

1.527 ꢁ 0.06

1.475 ꢁ 0.06

1.536 ꢁ 0.06

1.386 ꢁ 0.06

1.411 ꢁ 0.06

1.46 ꢁ 0.1

7e_a

7f

7g

8b

8c

1.407 ꢁ 0.06

1.354 ꢁ 0.06

1.399 ꢁ 0.06

1.442 ꢁ 0.06

8e

8g

8g_a

a

Data are given as mean ꢁ S.D. (n ¼ 3).

780

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

coupling, method employing DCC/NMM in DMF solvent

proved to be better than DCC/TEA method utilizing THF as

solvent, providing 10% extra yields. DCC proved to be a good

coupling agent both economically and yieldwise. Synthesized

peptide derivatives showed moderate to good antimicrobial

activity against all tested microbial strains except S. aureus

and M. audouinii. Presence of iodine atoms in nucleus confers

greater antibacterial activity whereas derivatives having nitro

group in nucleus possessed more antifungal activity but

nitro group in amino acid chain has not much effect on activity.

Gram negative bacteria proved to be more sensitive in compar-

ison to gram positive bacteria towards peptide derivatives. The

results of anthelmintic studies indicated the good level of activ-

ity of synthetic peptide derivatives when compared to the

standard drug, mebendazole. Greater anthelmintic activity was

found in derivatives with histidine and tryptophan constituents

in their amino acid chain. Derivatives bearing salicylic acid

moiety in nucleus possessed better anthelmintic and antifungal

activity in comparison to compounds having benzoic acid

moiety. Hydrolyzed derivatives exhibited more antimicrobial

and anthelmintic activity in comparison to their corresponding

methyl ester derivatives. Among tested compounds, only 8g_a,

8g and 6d possessed signiﬁcant cytotoxicity against DLA and

EAC cell lines in comparison to standard drug.

6.1.1. General procedure for the preparation of Boc-di/tri/

tetrapeptide methyl esters (2ae4d)

Boc-di/tri/tetrapeptide methyl esters 2aei, 3aegand 4aedwere

prepared by coupling Boc-amino acids/dipeptides with the re-

spective ^L-amino acid methyl ester hydrochlorides/dipeptide

methyl esters using DCC, HOBt and NMM according to Bod-

anzsky and Bodanzsky procedure with suitable modiﬁcations.

To remove the Boc group, Boc-di/tri/tetrapeptide methyl ester

(0.01 mol) was dissolved in CHCl₃(15 mL) and treated with tri-

ﬂuoroacetic acid (2.28 g). The resulting solution was stirred at

RT for 1 h and washed with saturated NaHCO₃solution

(25 mL). The organic layer was dried over anhydrous Na₂SO₄

and concentrated under reduced pressure. The crude product

was puriﬁed by crystallization from CHCl₃and petroleum ether

(b.p. 40e60 ^ꢂC) to get pure di/tri/tetrapeptide methyl esters

2a⁰ei⁰, 3a⁰eg⁰and 4a⁰ed⁰which were utilized directly for cou-

pling with compounds 5e8.

6.1.1.1. Compound 3a. Yield: 77%; [a]_Dꢀ35.0^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3125 (NeH str.), 3042 (AreH str.),

2996e2988 (CeH str., cyclic CH₂), 2826 (CeH str., OCH₃),

1750 (C]O str. ester), 1663, 1640 (C]O str. amide), 1567,

1425 (skeletal bands), 1462 (CeH def. CH₂), 1389, 1370

t

1

(CeH def. butyl grp), 1270, 930, 770, 708, 692 cm^ꢀ1; H

NMR (300 MHz, CDCl₃): d 8.62 (br s, 1H, NH, amide), 7.10

(t, 1H, J ¼ 6.2 Hz, p-H, Phe), 6.97 (tt, 2H, J ¼ 7.2, 4.4 Hz,

m-H’s, Phe), 6.85 (dd, 2H, J ¼ 8.8, 4.1 Hz, o-H’s, Phe), 5.07e

5.02 (m, 1H, a-H, Phe), 4.26 (t, 1H, J ¼ 6.8 Hz, a-H, Pro²),

3.97 (t, 1H, J ¼ 6.85 Hz, a-H, Pro¹), 3.56 (s, 3H, OCH₃), 3.53

(t, 2H, J ¼ 7.2 Hz, d-H’s, Pro²), 3.21 (t, 2H, J ¼ 7.15 Hz,

d-H’s, Pro¹), 3.02 (d, 2H, J ¼ 5.6 Hz, b-H’s, Phe), 2.69e2.61

(m, 4H, b-H’s, Pro¹and Pro²), 1.96e1.87 (m, 4H, g-H’s, Pro¹

6. Experimental protocols

6.1. General chemistry

All the reactions requiring anhydrous conditions were

conducted in ﬂame dried apparatus. Melting points were deter-

mined by open capillary method and are uncorrected. ^L-Amino

acids, di-tert-butylpyrocarbonate (Boc₂O), dicyclohexylcarbo-

diimide (DCC), triﬂuoroacetic acid (TFA), hydroxybenztriazole

(HOBt), triethylamine (TEA) and N-methylmorpholine (NMM)

were obtained from Spectrochem Limited (Mumbai, India). IR

spectra were recorded on Shimadzu 8700 FTIR spectrophotom-

eter (Shimadzu, Japan) using a thin ﬁlm supported on KBr pel-

lets or utilizing deuterated chloroform. ¹H NMR and ¹³C NMR

spectra were recorded on Bruker AC NMR spectrometer

(300 MHz), (Brucker, USA) using CDCl₃as solvent and tetra-

methylsilane (TMS) as internal standard. The mass spectra

were recorded on JMS-DX 303 mass spectrometer (Jeol, Tokyo,

Japan) operating at 70 eV by electron spray ionization technique

(ESI MS)/fast atom bombardment technique (FAB MS). Optical

rotation of synthesized peptides was measured on automatic

polarimeter (Optics Tech, Ghaziabad, India) in a 2 dm tube at

25 ^ꢂC using sodium lamp and methanol as solvent. Elemental

analyses of all compounds were performed on Vario EL III

elemental analyzer (Elementar, Germany). Purity of all synthe-

sized compounds was checked by TLC on precoated silica gel G

plates (Kieselgel 0.25 mm, 60G F₂₅₄, Merck, Germany)

utilizing chloroform/methanol as developing solvent system in

different ratios (9:1/8:2/7:3 v/v) and brown spots were detected

on exposure to iodine vapours in a tightly closed chamber.

t

and Pro²), 1.50 (s, 9H, butyl grp); ¹³C NMR (300 MHz,

CDCl₃): d 170.2 (C]O, sec. amide), 168.8 (C]O, ester),

t

166.7 (C]O, tert. amide), 156.3 (C]O, Boc), 138.0 (g-C,

Phe), 129.2 (o-C’s, Phe), 127.7 (m-C’s, Phe), 125.1 ( p-C,

Phe), 80.4 (a-C, ^tBoc), 63.6, 57.3 (a-C’s, Pro¹and Pro²), 54.1

(a-C, Phe), 50.5 (OCH₃), 47.0, 46.4 (d-C’s, Pro²and Pro¹),

t

38.8, 31.9 (b-C’s, Phe and Pro¹), 29.4 (b-C’s, Boc), 27.0

(g-C, Pro¹), 26.5 (b-C, Pro²), 24.3 (g-C, Pro²); C₂₅H₃₅N₃O₆

(473): Calcd. C 63.41, H 7.45, N 8.87; Found: C 63.38, H

7.46, N 8.85.

6.1.1.2. Compound 3a⁰. Yield: 73%; [a]_Dꢀ14.2^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3498, 3395, 3128 (NeH str.), 3045

(AreH str.), 2997e2988 (CeH str., cyclic CH₂), 1752 (C]O

str. ester), 1662, 1637 (C]O str. amide), 1565, 1425 (skeletal

bands), 1460 (CeH def. CH₂), 1272 (CeO str. ester), 1155

(CeN str. sec. amine), 768, 709, 692 cm^ꢀ1

;

¹H NMR

(300 MHz, CDCl₃): d 8.60 (br s, 1H, NH, amide), 7.11 (t, 1H,

J ¼ 6.15 Hz, p-H, Phe), 6.99 (tt, 2H, J ¼ 7.2, 4.35 Hz, m-H’s,

Phe), 6.86 (dd, 2H, J ¼ 8.75, 4.15 Hz, o-H’s, Phe), 6.8 (br s,

1H, NH, Pro¹), 5.08e5.00 (m, 1H, a-H, Phe), 4.14 (t, 1H,

J ¼ 6.85 Hz, a-H, Pro²), 3.58 (t, 1H, J ¼ 6.85 Hz, a-H, Pro¹),

3.55 (s, 3H, OCH₃), 3.43 (t, 2H, J ¼ 7.15 Hz, d-H’s, Pro²),

2.98 (d, 2H, J ¼ 5.6 Hz, b-H’s, Phe), 2.75 (t, 2H, J ¼ 7.2 Hz,

d-H’s, Pro¹), 2.69e2.65 (m, 2H, b-H’s, Pro²), 1.95e1.84 (m,

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

781

4H, g-H’s, Pro²and b-H’s, Pro¹), 1.78e1.70 (m, 2H, g-H’s,

Pro¹); ¹³C NMR (300 MHz, CDCl₃): d 170.1 (C]O, sec.

amide), 169.2 (C]O, ester), 166.4 (C]O, tert. amide), 138.0

(g-C, Phe), 129.3 (o-C’s, Phe), 127.9 (m-C’s, Phe), 125.3

( p-C, Phe), 63.3, 57.8 (a-C’s, Pro¹and Pro²), 54.6 (a-C, Phe),

50.6 (OCH₃), 47.4, 46.1 (d-C’s, Pro²and Pro¹), 38.8, 31.6

(b-C’s, Phe and Pro¹), 25.2 (b-C, Pro²), 26.5, 23.7 (g-C’s,

Pro¹and Pro²); C₂₀H₂₇N₃O₄(373): Calcd. C 64.32, H 7.29, N

11.25; Found: C 64.29, H 7.30, N 11.27.

OCH₃), 3.15e2.92 (m, 4H, b-H’s, Phe and d-H’s, Pro),

2.09e1.96 (m, 5H, b-, g-H’s, Pro and b-H, Val), 1.54 (s,

t

9H, butyl grp), 1.04 (d, 6H, J ¼ 4.6 Hz, g-H’s, Val); ¹³C

NMR (300 MHz, CDCl₃): d 170.5 (C]O, sec. amide),

168.6 (C]O, ester), 165.8 (C]O, tert. amide), 152.4

t

(C]O, Boc), 137.7 (g-C, Phe), 132.3 (o-C’s, Phe), 129.0

t

(m-C’s, Phe), 128.8 ( p-C, Phe), 79.9 (a-C, Boc), 58.0 (a-C,

Pro), 55.9 (a-C, Phe), 53.8 (a-C, Val), 53.1 (OCH₃), 45.6

(d-C, Pro), 34.2 (b-C, Phe), 29.8 (b-C, Val), 29.2 (b-C’s,

^tBoc), 28.7 (b-C, Pro), 24.9 (g-C, Pro), 18.2 (g-C’s, Val);

C₂₅H₃₇N₃O₆(475): Calcd. C 63.14, H 7.84, N 8.84; Found:

C 63.15, H 7.82, N 8.84.

6.1.1.3. Compound 3b. Yield: 81%; [a]_Dꢀ7.8^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3135, 3128 (NeH str.), 3370 (OeH

str., Tyr), 3066, 3042 (AreH str.), 2960, 2925, 2919 (CeH

str. CH₃and CH₂), 1745 (C]O str. ester), 1638, 1627

(C]O str. amide), 1556, 1412 (skeletal bands), 1530 (NH

def. amide), 1463 (CeH def. CH₂), 1392, 1368, 1271, 929,

6.1.1.6. Compound 3c⁰. Yield: 70%; [a]_Dꢀ16.9^ꢂ(c 0.9,

MeOH); ¹H NMR (300 MHz, CDCl₃): d 7.25 (tt, 2H,

J ¼ 7.15, 4.4 Hz, m-H’s, Phe), 6.96 (t, 1H, J ¼ 6.2 Hz, p-H,

Phe), 6.90 (br s, 1H, NH, amide), 6.72 (dd, 2H, J ¼ 8.75,

4.15 Hz, o-H’s, Phe), 4.31 (t, 1H, J ¼ 5.8 Hz, a-H, Val), 3.61

(t, 1H, J ¼ 6.85 Hz, a-H, Pro), 3.62 (s, 3H, OCH₃), 3.60e3.57

(m, 1H, a-H, Phe), 3.11 (t, 2H, J ¼ 7.15 Hz, d-H, Pro), 2.76

(d, 2H, J ¼ 5.65 Hz, b-H’s, Phe), 2.10e1.94 (m, 5H, b- and

g-H’s, Pro and b-H, Val), 1.82 (2H, br s, NH₂), 1.05 (d, 6H,

J ¼ 4.55 Hz, g-H’s, Val); ¹³C NMR (300 MHz, CDCl₃):

d 170.2 (C]O, sec. amide), 168.8 (C]O, ester), 165.4

(C]O, tert. amide), 138.2 (g-C, Phe), 131.8 (o-C’s, Phe),

129.7 (m-C’s, Phe), 128.4 ( p-C, Phe), 58.3 (a-C, Pro), 56.2

(a-C, Phe), 54.3 (a-C, Val), 53.5 (OCH₃), 45.6 (d-C, Pro),

34.8 (b-C, Phe), 30.6 (b-C, Val), 28.7 (b-C, Pro), 24.5 (g-C,

Pro), 17.8 (g-C’s, Val); C₂₀H₂₉N₃O₄(375): Calcd. C 63.98, H

7.78, N 11.19; Found: C 64.00, H 7.75, N 11.21.

1

828, 690 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.12 (br s,

1H, NH, amide), 7.11 (br s, 1H, NH, amide), 6.99e6.89 (m,

4H, o- and m-H’s, Tyr), 6.62 (br s, 1H, NH, amide), 5.95 (br

s, 1H, OH, Tyr), 4.58e4.52 (m, 1H, a-H, Tyr), 4.39e4.32

(m, 1H, a-H, Ala), 4.03 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly),

3.65 (s, 3H, OCH₃), 2.78 (d, 2H, J ¼ 5.45 Hz, b-H’s, Tyr),

t

1.59 (d, 3H, J ¼ 5.85 Hz, b-H’s, Ala), 1.54 (s, 9H, butyl

grp); ¹³C NMR (300 MHz, CDCl₃): d 170.8, 169.4 (C]O,

t

amide), 168.2 (C]O, ester), 156.9 (C]O, Boc), 152.7 ( p-

C, Tyr), 132.4 (g-C, Tyr), 130.6 (o-C’s, Tyr), 128.3 (m-C’s,

t

Tyr), 79.8 (a-C, Boc), 53.6 (a-C, Ala), 52.1 (a-C, Tyr), 50.4

(OCH₃), 41.8 (CH₂, Gly), 37.3 (b-C, Tyr), 29.4 (b-C’s,

^tBoc), 19.5 (b-C, Ala); C₂₀H₂₉N₃O₇(423): Calcd. C 56.73,

H 6.90, N 9.92; Found: C 56.69, H 6.94, N 9.90.

6.1.1.4. Compound 3b⁰. Yield: 76%; [a]_Dꢀ44.6^ꢂ(c 0.9,

6.1.1.7. Compound 3d. Yield: 82%; [a]_Dþ8.2^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 2997e2985 (CeH str., cyclic CH₂),

2826 (CeH str., OCH₃), 1750 (C]O str. ester), 1663, 1658

1

MeOH); H NMR (300 MHz, CDCl₃): d 8.28 (br s, 1H, NH,

amide), 7.00e6.88 (m, 4H, o- and m-H’s, Tyr), 6.50 (br s,

1H, NH, amide), 4.88e4.83 (m, 1H, a-H, Tyr), 4.02 (d, 2H,

J ¼ 5.1 Hz, CH₂, Gly), 3.63 (s, 3H, OCH₃), 3.55e3.49 (m,

1H, a-H, Ala), 2.97 (br s, 3H, NH₂and OH), 2.76 (d, 2H,

J ¼ 5.5 Hz, b-H’s, Tyr), 1.11 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala);

¹³C NMR (300 MHz, CDCl₃): d 170.8, 169.6 (C]O, amide),

168.5 (C]O, ester), 153.2 ( p-C, Tyr), 132.2 (g-C, Tyr), 130.4

(o-C’s, Tyr), 126.6 (m-C’s, Tyr), 53.2 (a-C, Ala), 52.6 (a-C,

Tyr), 50.1 (OCH₃), 41.3 (CH₂, Gly), 37.6 (b-C, Tyr), 18.9

(b-C, Ala); C₁₅H₂₁N₃O₅(323): Calcd. C 55.72, H 6.55, N

13.00; Found: C 55.75, H 6.52, N 12.97.

t

(C]O str. tert. amide), 1389, 1370 (CeH def. butyl grp),

1

1271, 929 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 4.35 (t, 1H,

J ¼ 6.8 Hz, a-H, Pro²), 4.27e4.16 (m, 2H, a-H’s, Pro¹and

Pro³), 3.72 (t, 2H, J ¼ 7.2 Hz, d-H’s, Pro³), 3.62 (s, 3H,

OCH₃), 3.53 (t, 2H, J ¼ 7.15 Hz, d-H’s, Pro²), 3.23 (t, 2H,

J ¼ 7.2 Hz, d-H’s, Pro¹), 2.70e2.55 (m, 4H, b-H’s, Pro¹and

Pro²), 2.07e1.88 (m, 8H, b- and g-H’s, Pro³and g-H’s,

Pro¹and Pro²), 1.50 (s, 9H, ^tbutyl grp); ¹³C NMR

(300 MHz, CDCl₃): d 170.4, 168.3 (C]O, amide), 166.5

t

(C]O, ester), 157.2 (C]O, Boc), 80.9 (a-C, Boc), 62.7,

58.8, 55.2 (a-C’s, Pro^1e3), 53.7 (OCH₃), 46.9, 45.7 (d-C’s,

Pro^1,2), 41.1 (d-C, Pro³), 32.0, 29.7, 28.8 (b-C’s, Pro^1e3),

27.4 (b-C’s, ^tBoc), 24.5, 23.2, 22.7 (g-C’s, Pro^1e3);

C₂₁H₃₃N₃O₆(423): Calcd. C 59.56, H 7.85, N 9.92; Found:

C 59.55, H 7.85, N 9.96.

6.1.1.5. Compound 3c. Yield: 86%; [a]_Dꢀ9.3^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3129, 3118 (NeH str.), 3062 (AreH

str.), 2995, 2992 (CeH str. cyclic CH₂), 2962, 2926 (CeH

str. CH₃and CH₂), 1748 (C]O str. ester), 1658, 1629

(C]O str. amide), 1554, 1420 (skeletal bands), 1390, 1369

t

(CeH def. butyl grp), 1385, 1363 (CeH def. isopropyl

grp), 1268, 931, 923, 766, 707, 694 cm^ꢀ1

6.1.1.8. Compound 3d⁰. Yield: 76%; [a]_Dþ16.7^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3502, 3398 (NeH str.), 2998e2985

(CeH str., cyclic CH₂), 2828 (CeH str., OCH₃), 1748

(C]O str. ester), 1660, 1657 (C]O str. tert. amide), 1270

;

(CeO str. ester), 1159 (CeN str. sec. amine) cm^ꢀ^{1 1}H

NMR (300 MHz, CDCl₃): d 6.80 (br s, 1H, NH, amide),

4.28e4.18 (m, 2H, a-H’s, Pro²and Pro³), 3.73 (t, 2H,

;

¹H NMR

(300 MHz, CDCl₃): d 7.62 (br s, 1H, NH, amide), 7.50 (tt,

2H, J ¼ 7.2, 4.35 Hz, m-H’s, Phe), 6.91 (t, 1H, J ¼ 6.15 Hz,

p-H, Phe), 6.84 (dd, 2H, J ¼ 8.8, 4.15 Hz, o-H’s, Phe), 6.57

(br s, 1H, NH, amide), 4.46e4.41 (m, 2H, a-H’s, Phe and

Val), 3.62 (t, 1H, J ¼ 6.85 Hz, a-H, Pro), 3.63 (s, 3H,

782

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

J ¼ 7.1 Hz, d-H’s, Pro³), 3.63 (s, 3H, OCH₃), 3.57 (t, 1H,

J ¼ 6.85 Hz, a-H, Pro¹), 3.43 (t, 2H, J ¼ 7.15 Hz, d-H’s,

Pro²), 2.80e2.65 (m, 4H, d-H’s, Pro¹and b-H’s, Pro²),

2.07e1.84 (m, 8H, b-H’s, Pro¹and Pro³and g-H’s, Pro²and

Pro³), 1.77e1.68 (m, 2H, g-H’s, Pro¹); ¹³C NMR (300 MHz,

CDCl₃): d 169.9, 168.2 (C]O, tert. amide), 166.8 (C]O,

ester), 62.2, 59.1, 55.3 (a-C’s, Pro^1e3), 53.4 (OCH₃), 47.2,

45.5 (d-C’s, Pro^1,2), 41.7 (d-C, Pro³), 31.6, 29.5, 28.2 (b-C’s,

Pro^1e3), 25.0, 23.4, 22.8 (g-C’s, Pro^1e3); C₁₆H₂₅N₃O₄(323):

Calcd. C 59.43, H 7.79, N 12.99; Found: C 59.45, H 7.82, N

13.00.

37.9, 30.1 (b-C, Phe and Val), 23.1 (b-C, His), 18.3 (g-C’s,

Val); C₂₁H₂₉N₅O₄(415): Calcd. C 60.71, H 7.03, N 16.86;

Found: C 60.72, H 6.99, N 16.88.

6.1.1.11. Compound 3f. Yield: 86%; [a]_Dꢀ74.6^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3492, 3124 (NeH str.), 3358 (OeH

str. Tyr), 3032, 3023 (AreH str.), 2966, 2925, 2922 (CeH

str. CH₃and CH₂), 1752 (C]O str. ester), 1642, 1635

(C]O str. amide), 1546, 1422 (skeletal bands), 1530, 1528

t

(NH def. amide), 1390, 1373 (CeH def. butyl grp), 1271,

929, 828, 742, 698 cm^{ꢀ1 1}H NMR (300 MHz, CDCl₃):

;

d 8.75 (br s, 1H, NH, amide), 7.45 (br s, 2H, NH, Indole

and OH, Tyr), 7.27e7.09 (m, 4H, deh-H’s, Indole), 6.90

(dd, 2H, J ¼ 8.5, 5.2 Hz, o-H’s, Tyr), 6.79 (dd, 2H, J ¼ 8.6,

4.9 Hz, m-H’s, Tyr), 6.76 (br s, 1H, NH, amide), 6.58 (br s,

1H, NH, amide), 6.23 (d, 1H, J ¼ 7.85 Hz, b-H, Indole),

4.84e4.77 (m, 1H, a-H, Trp), 4.46e4.37 (m, 1H, a-H,

Ala), 3.96e3.89 (m, 1H, a-H, Tyr), 3.55 (s, 3H, OCH₃),

6.1.1.9. Compound 3e. Yield: 85%; [a]_Dꢀ41.5^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3489, 3129 (NeH str.), 3052, 3040

(AreH str.), 2920, 2851 (CeH str. CH₂), 1750 (C]O str. es-

ter), 1642, 1638 (C]O str. amide), 1568, 1425 (skeletal

t

bands), 1392, 1370 (CeH def. butyl grp), 1383, 1362 (CeH

def. isopropyl grp), 1269, 930, 922, 884, 768, 707,

1

t

696 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 9.12 (br s, 1H,

3.15e2.96 (m, 4H, b-H’s, Tyr and Trp), 1.54 (s, 9H, butyl

grp), 1.50 (d, 3H, J ¼ 5.85 Hz, b-H’s, Ala); ¹³C NMR

NH, amide), 7.74 (d, 1H, J ¼ 8.0 Hz, b-H, Imz), 7.60 (s,

1H, d-H, Imz), 7.56 (br s, 1H, NH, amide), 7.16 (tt, 2H,

J ¼ 7.2, 4.3 Hz, m-H’s, Phe), 6.99 (t, 1H, J ¼ 6.2 Hz, p-H,

Phe), 6.94 (br s, 1H, NH, amide), 6.81 (dd, 2H, J ¼ 8.8,

4.15 Hz, o-H’s, Phe), 6.44 (br s, 1H, NH, amide), 4.38e

4.33 (m, 1H, a-H, Phe), 4.20e4.16 (m, 1H, a-H, Val),

4.14e4.09 (m, 1H, a-H, His), 3.55 (s, 3H, OCH₃), 3.03e

2.86 (m, 4H, b-H’s, Phe and His), 1.87e1.76 (m, 1H, b-H,

(300 MHz, CDCl₃): d 175.8, 172.2 (C]O, amide), 168.8

t

(C]O, ester), 154.3 ( p-C, Tyr), 152.3 (C]O, Boc), 138.8

0

(C₂, Indole), 129.7 (o-C’s, Tyr), 128.5 (m-C’s, Tyr), 126.1

0

(C₃, Indole), 124.3 (C₂, Indole), 121.7, 120.4, 118.3 (C_4e6

,

Indole), 116.2 (g-C, Tyr), 113.7 (C₇, Indole), 108.9 (C₃, In-

t

dole), 79.7 (a-C, Boc), 65.3 (a-C, Trp), 55.4 (a-C, Tyr),

54.1 (a-C, Ala), 52.6 (OCH₃), 38.9 (b-C, Tyr), 28.8 (b-C,

Trp), 27.2 (b-C’s, ^tBoc), 18.9 (b-C, Ala); C₂₉H₃₆N₄O₇

(552): Calcd. C 63.03, H 6.57, N 10.14; Found: C 62.99, H

6.60, N 10.15.

t

Val), 1.54 (s, 9H, butyl grp), 1.05 (d, 6H, J ¼ 4.55 Hz,

g-H’s, Val); ¹³C NMR (300 MHz, CDCl₃): d 172.8 (C]O, es-

t

ter), 171.1, 169.2 (C]O, amide), 156.7 (C]O, Boc), 142.8

(C₂, Imz), 135.6 (g-C, Phe), 130.4 (o-C’s, Phe), 128.8 (m-

C’s, Phe), 127.2 ( p-C, Phe), 124.8 (C₄, Imz), 115.5 (C₅,

6.1.1.12. Compound 3f⁰. Yield: 80%; [a]_Dꢀ115.7^ꢂ(c 0.9,

t

Imz), 79.7 (a-C, Boc), 60.6, 53.9, 51.4 (a-C’s, Val, His and

Phe), 50.3 (OCH₃), 38.2, 29.6 (b-C, Phe and Val), 27.5 (b-

1

MeOH); H NMR (300 MHz, CDCl₃): d 7.60 (br s, 1H, NH,

amide), 7.28e7.17 (m, 4H, deh-H’s, Indole), 6.94 (d, 1H,

J ¼ 7.8 Hz, b-H, Indole), 6.90 (dd, 2H, J ¼ 8.55, 5.2 Hz,

o-H’s, Tyr), 6.80 (br s, 1H, NH, amide), 6.78 (dd, 2H,

J ¼ 8.6, 4.95 Hz, m-H’s, Tyr), 4.60 (br s, 4H, NH, Indole

and NH₂, OH), 4.52e4.47 (m, 1H, a-H, Ala), 4.17e4.13 (m,

1H, a-H, Trp), 3.94 (t, 1H, J ¼ 8.0 Hz, a-H, Tyr), 3.54 (s,

3H, OCH₃), 3.07e2.95 (m, 4H, b-H’s, Tyr and Trp), 1.49 (d,

3H, J ¼ 5.9 Hz, b-H’s, Ala); ¹³C NMR (300 MHz, CDCl₃):

d 174.9, 172.8 (C]O, amide), 169.2 (C]O, ester), 154.1

t

C’s, Boc), 22.8 (b-C, His), 18.2 (g-C’s, Val); C₂₆H₃₇N₅O₆

(515): Calcd. C 60.57, H 7.23, N 13.58; Found: C 60.55, H

7.26, N 13.59.

6.1.1.10. Compound 3e⁰. Yield: 75%; [a]_Dꢀ32.8^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3504, 3395 (NeH str.), 3049, 3042

(AreH str.), 2922, 2850 (CeH str. CH₂), 1747 (C]O str. ester),

1640, 1637 (C]O str. amide), 1611 (NeH def. amine), 1565,

1428 (skeletal bands), 1381, 1363 (CeH def. isopropyl grp),

0

( p-C, Tyr), 138.2 (C₂, Indole), 129.8 (o-C’s, Tyr), 127.8

1268, 1233, 924, 887, 765, 704, 698 cm^ꢀ1

;

¹H NMR

(m-C’s, Tyr), 126.8 (C₃, Indole), 124.9 (C₂, Indole), 122.0,

0

(300 MHz, CDCl₃): d 7.75 (d, 1H, J ¼ 7.95 Hz, b-H, Imz),

7.59 (s, 1H, d-H, Imz), 7.55 (br s, 1H, NH, amide), 7.18 (tt,

2H, J ¼ 7.15, 4.35 Hz, m-H’s, Phe), 6.99 (t, 1H, J ¼ 6.15 Hz,

p-H, Phe), 6.93 (br s, 1H, NH, amide), 6.83 (dd, 2H, J ¼ 8.8,

4.2 Hz, o-H’s, Phe), 5.95 (br s, 3H, NH, Imz and NH₂, Val),

4.36e4.30 (m, 1H, a-H, Phe), 4.15e4.08 (m, 1H, a-H, His),

3.54 (s, 3H, OCH₃), 3.52e3.49 (m, 1H, a-H, Val), 3.05e2.90

(m, 4H, b-H’s, Phe and His), 1.76e1.66 (m, 1H, b-H, Val),

1.00 (d, 6H, J ¼ 4.55 Hz, g-H’s, Val); ¹³C NMR (300 MHz,

CDCl₃): d 173.1 (C]O, ester), 170.9, 169.0 (C]O, amide),

143.1 (C₂, Imz), 135.3 (g-C, Phe), 129.8 (o-C’s, Phe), 128.3

(m-C’s, Phe), 127.1 ( p-C, Phe), 125.0 (C₄, Imz), 115.2 (C₅,

Imz), 61.2, 53.0, 51.5 (a-C’s, Val, His and Phe), 50.0 (OCH₃),

119.8, 118.5 (C_4e6, Indole), 115.7 (g-C, Tyr), 113.0 (C₇, In-

dole), 109.3 (C₃, Indole), 64.6 (a-C, Trp), 56.0 (a-C, Tyr),

54.6 (a-C, Ala), 52.9 (OCH₃), 38.5 (b-C, Tyr), 29.4 (b-C,

Trp), 18.0 (b-C, Ala); C₂₄H₂₈N₄O₅(452): Calcd. C 63.70, H

6.24, N 12.38; Found: C 63.68, H 6.25, N 12.40.

6.1.1.13. Compound 3g. Yield: 85%; [a]_Dþ17.0^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3127, 3123 (NeH str.), 2962, 2958,

2874 (CeH str. CH₃), 1750 (C]O str. ester), 1640, 1636

(C]O str. amide), 1533, 1525 (NH def. amide), 1393, 1372

t

1

(CeH def. butyl grp), 1385, 1362, 1267, 932, 923 cm^ꢀ1; H

NMR (300 MHz, CDCl₃): d 7.90 (br s, 1H, NH, amide),

6.81 (br s, 1H, NH, amide), 6.53 (br s, 1H, NH, amide),

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

783

4.46 (t, 1H, J ¼ 5.75 Hz, a-H, Val), 4.25e4.17 (m, 1H, a-H,

Ala¹), 3.60 (s, 3H, OCH₃), 3.54e3.43 (m, 1H, a-H, Ala²),

2.10e1.95 (m, 1H, b-H, Val), 1.58 (d, 3H, J ¼ 5.9 Hz,

b-H’s, Ala¹), 1.55 (s, 9H, ^tbutyl grp), 1.30 (d, 3H,

J ¼ 5.85 Hz, b-H’s, Ala²), 1.04 (d, 6H, J ¼ 4.6 Hz, g-H’s,

Val); ¹³C NMR (300 MHz, CDCl₃): d 176.4 (C]O, amide),

173.2 (C]O, ester), 169.2 (C]O, amide), 152.5 (C]O,

str. CH₃and CH₂), 1747 (C]O str. ester), 1643, 1629

(C]O str. amide), 1615 (NeH def. amine), 1540, 1424

(skeletal bands), 1523 (NH def. amide), 1269, 1235, 1154,

1

745, 695 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 7.60 (br s,

1H, NH, amide), 7.32e7.06 (m, 4H, deh-H’s, Indole),

7.03 (br s, 1H, NH, amide), 6.95 (d, 1H, J ¼ 5.65 Hz, b-H,

Indole), 6.69 (br s, 1H, NH, amide), 4.22 (t, 1H,

J ¼ 8.55 Hz, a-H, Ile), 4.18 (br s, 3H, NH₂, Trp and NH, In-

dole), 4.16e4.10 (m, 1H, a-H, Trp), 4.06 (d, 2H,

J ¼ 5.15 Hz, CH₂, Gly), 3.81e3.70 (m, 1H, a-H, Ala), 3.62

(s, 3H, OCH₃), 3.00 (d, 2H, J ¼ 5.65 Hz, b-H’s, Trp),

2.10e1.96 (m, 1H, b-H, Ile), 1.69e1.56 (m, 2H, g-H’s,

Ile), 1.30 (d, 3H, J ¼ 5.85 Hz, b-H’s, Ala), 1.03e0.95 (m,

6H, g⁰- and d-H’s, Ile); ¹³C NMR (300 MHz, CDCl₃):

d 174.7 (C]O, ester), 172.2, 169.9, 165.7 (C]O, amide),

t

^tBoc), 80.2 (a-C, Boc), 60.5 (a-C, Ala¹), 53.3 (a-C, Val),

50.2 (OCH₃), 47.5 (a-C, Ala²), 28.4 (b-C, Val), 26.8 (b-C’s,

^tBoc), 21.4 (b-C, Ala¹), 18.5 (g-C’s, Val), 17.6 (b-C, Ala²);

C₁₇H₃₁N₃O₆(373): Calcd. C 54.68, H 8.37, N 11.25; Found:

C 54.71, H 8.37, N 11.21.

6.1.1.14. Compound 3g⁰. Yield: 81%; [a]_Dþ10.2^ꢂ(c 0.9,

MeOH); ¹H NMR (300 MHz, CDCl₃): d 7.78 (br s, 1H, NH, am-

ide), 6.82 (br s, 1H, NH, amide), 4.43 (t, 1H, J ¼ 6.85 Hz, a-H,

Val), 3.59 (s, 3H, OCH₃), 3.53e3.44 (m, 1H, a-H, Ala²), 3.29e

3.22 (m, 1H, a-H, Ala¹), 2.11e1.97 (m, 1H, b-H, Val), 1.49 (br

s, 2H, NH₂, Ala¹), 1.29 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala²), 1.13 (d,

3H, J ¼ 5.85 Hz, b-H’s, Ala¹), 1.05 (d, 6H, J ¼ 4.55 Hz, g-H’s,

Val); ¹³C NMR (300 MHz, CDCl₃): d 173.0 (C]O, ester),

170.8, 169.1 (C]O, amide), 55.9 (a-C, Val), 52.4 (a-C,

Ala¹), 50.1 (OCH₃), 48.5 (a-C, Ala²), 28.4 (b-C, Val), 21.5

(b-C, Ala²), 18.4 (g-C’s, Val), 17.7 (b-C, Ala¹); C₁₂H₂₃N₃O₄

(273): Calcd. C 52.73, H 8.48, N 15.37; Found: C 52.75, H

8.47, N 15.40.

0

138.5, 128.3 (C_{2 ,3}, Indole), 124.6 (C₂, Indole), 122.2,

119.4, 118.1, 112.3 (C_4e7, Indole), 107.1 (C₃, Indole),

61.8, 50.3 (a-C’s, Trp and Ile), 49.8 (OCH₃), 47.5 (a-C,

Ala), 41.3 (CH₂, Gly), 36.2, 30.3 (b-C’s, Ile and Trp), 23.0

(g-C, Ile), 17.7 (b-C, Ala), 13.0 (g⁰-C, Ile), 10.1 (d-C, Ile);

C₂₃H₃₃N₅O₅(459): Calcd. C 60.11, H 7.24, N 15.24; Found:

C 60.12, H 7.20, N 15.25.

6.1.1.17. Compound 4b. Yield: 88%; [a]_Dꢀ54.6^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3332 (OeH str.), 3133, 3129 (NeH

str.), 2960, 2872, 2850 (CeH str. CH₃and CH₂), 1753

(C]O str. ester), 1645, 1643 (C]O str. amide), 1535, 1532

(NH def. amide), 1457 (CeH def. CH₂), 1422, 1329 (OeH

6.1.1.15. Compound 4a. Yield: 78%; [a]_Dꢀ21.6^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3492, 3128, 3124 (NeH str.), 3064

(AreH str.), 2965e2938, 2866e2848 (CeH str. CH₃and

CH₂), 1752 (C]O str. ester), 1640, 1628 (C]O str. amide),

t

def.), 1391, 1370 (CeH def. butyl grp), 1269, 1091, 929,

1

662 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.90 (br s, 1H,

NH, amide), 7.72 (br s, 1H, NH, amide), 6.50 (br s, 1H,

NH, amide), 6.24 (br s, 1H, NH, amide), 4.62e4.54 (m, 1H,

b-H, Thr), 4.23 (t, 1H, J ¼ 8.6 Hz, a-H, Ile), 3.81 (d, 2H,

J ¼ 5.15 Hz, CH₂, Gly²), 3.77 (t, 1H, J ¼ 3.9 Hz, a-H, Thr),

3.62 (s, 3H, OCH₃), 3.51 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly¹),

3.26 (br s, 1H, OH, Thr), 1.60e1.56 (m, 2H, g-H’s, Ile),

1542, 1426 (skeletal bands), 1525, 1520 (NH def. amide),

t

1395, 1371 (CeH def. butyl grp), 1271, 930, 748, 698 cm^ꢀ1

;

¹H NMR (300 MHz, CDCl₃): d 8.95 (br s, 1H, NH, Indole),

7.94 (br s, 1H, NH, amide), 7.25e7.02 (m, 4H, deh-H’s,

Indole), 7.09 (br s, 1H, NH, amide), 6.68 (br s, 1H, NH, amide),

6.57 (br s, 1H, NH, amide), 6.21 (d, 1H, J ¼ 7.8 Hz, b-H,

Indole), 4.84e4.80 (m, 1H, a-H, Trp), 4.21 (t, 1H, J ¼ 8.6 Hz,

a-H, Ile), 4.10 (d, 2H, J ¼ 5.1 Hz, CH₂, Gly), 3.76 (t, 1H,

J ¼ 4.1 Hz, a-H, Ala), 3.60 (s, 3H, OCH₃), 3.43 (d, 2H,

J ¼ 5.7 Hz, b-H’s, Trp), 2.07e1.95 (m, 1H, b-H, Ile), 1.68e

t

1.54 (s, 9H, butyl grp), 1.53e1.49 (m, 1H, b-H, Ile), 1.31

(d, 3H, J ¼ 4.9 Hz, g-H’s, Thr), 1.01e0.94 (m, 6H, g⁰- and

d-H’s, Ile); ¹³C NMR (300 MHz, CDCl₃): d 177.6, 174.5

(C]O, amide), 171.7 (C]O, ester), 165.8 (C]O, amide),

t

154.5 (C]O, Boc), 79.5 (a-C, Boc), 68.8 (b-C, Thr), 58.1,

55.3 (a-C’s, Thr and Ile), 50.5 (OCH₃), 48.3, 44.2 (CH₂,

t

1.57 (m, 2H, g-H’s, Ile), 1.55 (s, 9H, butyl grp), 1.29 (d, 3H,

t

J ¼ 5.85 Hz, b-H’s, Ala), 1.03 (d, 3H, J ¼ 5.9 Hz, g⁰-H’s, Ile),

Gly²and Gly¹), 36.8 (b-C, Ile), 28.3 (b-C’s, Boc), 27.6,

0.97 (t, 3H, J ¼ 7.7 Hz, d-H’s, Ile); ¹³C NMR (300 MHz,

20.0 (g-C’s, Ile and Thr), 13.7 (g⁰-C, Ile), 9.9 (d-C, Ile);

C₂₀H₃₆N₄O₈(460): Calcd. C 52.16, H 7.88, N 12.17; Found:

C 52.20, H 7.90, N 12.15.

CDCl₃): d 175.2 (C]O, ester), 171.8, 170.7, 165.9 (C]O,

0

t

amide), 154.6 (C]O, Boc), 138.0 (C₂, Indole), 127.5 (C₃, In-

dole), 124.2 (C₂, Indole), 121.7, 119.5, 117.3, 112.7 (C_4e7, In-

0

t

dole), 106.9 (C₃, Indole), 80.2 (a-C, Boc), 65.4, 50.5 (a-C’s,

6.1.1.18. Compound 4b⁰. Yield: 70%; [a]_Dꢀ2.9^ꢂ(c 0.9,

MeOH); ¹H NMR (300 MHz, CDCl₃): d 8.89 (br s, 1H,

NH, amide), 7.46 (br s, 1H, NH, amide), 6.23 (br s, 1H,

NH, amide), 4.66e4.54 (m, 2H, b-H, Thr and a-H, Ile),

3.82 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly²), 3.78 (t, 1H,

J ¼ 3.95 Hz, a-H, Thr), 3.63 (s, 3H, OCH₃), 3.61 (d, 2H,

J ¼ 5.15 Hz, CH₂, Gly¹), 3.56 (br s, 3H, OH, Thr and NH₂),

1.59e1.35 (m, 3H, b- and g-H’s, Ile), 1.32 (d, 3H,

J ¼ 4.95 Hz, g-H’s, Thr), 1.00e0.93 (m, 6H, g⁰- and d-H’s,

Ile); ¹³C NMR (300 MHz, CDCl₃): d 176.9 (C]O, amide),

Trp and Ile), 49.8 (OCH₃), 47.6 (a-C, Ala), 40.7 (CH₂, Gly),

t

35.9, 30.0 (b-C’s, Ile and Trp), 27.4 (b-C’s, Boc), 22.7 (g-C,

Ile), 17.7 (b-C, Ala), 13.2 (g⁰-C, Ile), 10.9 (d-C, Ile);

C₂₈H₄₁N₅O₇(559): Calcd. C 60.09, H 7.38, N 12.51; Found:

C 60.10, H 7.41, N 12.50.

6.1.1.16. Compound 4a⁰. Yield: 72%; [a]_Dꢀ4.3^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3502e3496, 3403, 3129e3122 (Ne

H str.), 3068 (AreH str.), 2966e2938, 2865e2849 (CeH

784

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

171.6 (C]O, ester), 169.9, 167.8 (C]O, amide), 68.5

(b-C, Thr), 58.0, 56.2 (a-C’s, Thr and Ile), 51.2 (OCH₃),

46.8, 44.3 (CH₂, Gly²and Gly¹), 37.0 (b-C, Ile), 27.5, 19.8

(g-C’s, Ile and Thr), 13.5 (g⁰-C, Ile), 9.8 (d-C, Ile);

C₁₅H₂₈N₄O₆(360): Calcd. C 49.99, H 7.83, N 15.55; Found:

C 50.00, H 7.85, N 15.56.

C₂₀H₃₂N₆O₅(436): Calcd. C 55.03, H 7.39, N 19.25; Found:

C 55.01, H 7.40, N 19.25.

6.1.1.21. Compound 4d. Yield: 87%; [a]_Dþ1.2^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3490, 3486, 3125 (NeH str.), 3066,

3045 (AreH str.), 2928, 2925, 2850 (CeH str. CH₂), 2826

(CeH str, OCH₃), 1747 (C]O str. ester), 1633, 1628 (C]O

str. amide), 1543, 1421 (skeletal bands), 1530, 1524 (NH def.

amide), 1392, 1369 (CeH def. ^tbutyl grp), 1270 (CeO str. es-

6.1.1.19. Compound 4c. Yield: 84%; [a]_Dþ43.0^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3480, 3124, 3120 (NeH str.), 3055

(AreH str.), 2997, 2994 (CeH str., cyclic CH₂), 2926, 2920,

2854 (CeH str. CH₂), 1749 (C]O str. ester), 1660, 1643

(C]O str. amide), 1562, 1424 (skeletal bands), 1536 (NH def.

1

ter), 928, 867, 738, 696 cm^ꢀ1; H NMR (300 MHz, CDCl₃):

d 9.05 (br s, 2H, NH’s, Indole and Imz), 8.46 (br s, 1H, NH, am-

ide), 8.26 (br s, 1H, NH, amide), 7.75 (d, 1H, J ¼ 7.95 Hz, b-H,

Imz), 7.60 (s, 1H, d-H, Imz), 7.25 (d, 1H, J ¼ 7.85 Hz, b-H, In-

dole), 7.22e7.08 (m, 4H, deh-H’s, Indole), 6.32 (br s, 1H, NH,

amide), 6.23 (br s, 1H, NH, amide), 4.70e4.63 (m, 1H, a-H,

Trp), 4.16e4.10 (m, 1H, a-H, His), 3.82 (d, 2H, J ¼ 5.15 Hz,

CH₂, Gly²), 3.72 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly¹), 3.54 (s, 3H,

OCH₃), 3.21e3.09 (m, 4H, b-H’s, Trp and His), 1.55 (s, 9H,

^tbutyl grp); ¹³C NMR (300 MHz, CDCl₃): d 178.2 (C]O, am-

t

amide), 1395, 1371 (CeH def. butyl grp), 1386, 1365 (CeH

1

def. isopropyl grp), 1268, 929, 921, 886, 699 cm^ꢀ1; H NMR

(300 MHz, CDCl₃): d 9.10 (br s, 1H, NH, Imz), 8.95 (br s, 1H,

NH, amide), 7.89 (d, 1H, J ¼ 7.95 Hz, b-H, Imz), 7.15 (br s,

1H, NH, amide), 6.46 (br s, 1H, NH, amide), 6.44 (s, 1H, d-H,

Imz), 4.80e4.75 (m, 1H, a-H, His), 4.59e4.54 (m, 1H, a-H,

Leu), 4.46 (t, 1H, J ¼ 6.9 Hz, a-H, Pro), 4.02 (d, 2H,

J ¼ 5.1 Hz, CH₂, Gly), 3.69 (t, 2H, J ¼ 7.15 Hz, d-H’s, Pro),

3.65 (s, 3H, OCH₃), 3.09 (d, 2H, J ¼ 5.9 Hz, b-H’s, His), 2.70e

2.65 (m, 2H, b-H’s, Pro), 1.96e1.88 (m, 2H, g-H’s, Pro), 1.82

(t, 2H, J ¼ 7.95 Hz, b-H’s, Leu), 1.54 (s, 9H, ^tbutyl grp), 1.52e

1.44 (m, 1H, g-H, Leu), 0.98 (d, 6H, J ¼ 6.2 Hz,

d-H’s, Leu); ¹³C NMR (300 MHz, CDCl₃): d 172.5 (C]O, tert.

amide), 171.2, 169.6 (C]O, sec. amide), 168.1 (C]O, ester),

ide), 172.3 (C]O, ester), 170.7 (C]O, amide), 168.8 (C]O,

0

t

amide), 156.6 (C]O, Boc), 142.3 (C₂, Imz), 136.1 (C₂, In-

0

dole), 129.3 (C₃, Indole), 126.8 (C₄, Imz), 122.6 (C₂, Indole),

120.8, 119.7, 118.8 (C_4e6, Indole), 114.5 (C₅, Imz), 113.1

t

(C₃, Indole), 110.9 (C₇, Indole), 79.5 (a-C, Boc), 55.6 (a-C,

Trp), 51.9 (a-C, His), 50.2 (OCH₃), 48.3 (CH₂, Gly²), 43.2

t

(CH₂, Gly¹), 32.8 (b-C, Trp), 27.5 (b-C’s, Boc), 24.2 (b-C,

t

154.6 (C]O, Boc), 142.3, 120.2, 112.5 (C_2,4,5, Imz), 79.9

(a-C, ^tBoc), 65.7, 56.2 (a-C’s, His and Pro), 52.4 (OCH₃), 49.3

(a-C, Leu), 47.2 (d-C, Pro), 44.6 (b-C, Leu), 39.5 (CH₂, Gly),

His); C₂₇H₃₅N₇O₇(569): Calcd. C 56.93, H 6.19, N 17.21;

Found: C 56.95, H 6.17, N 17.20.

t

28.5 (b-C’s, Boc), 26.5, 25.2 (b- and g-C’s, Pro), 23.9

6.1.1.22. Compound 4d⁰. Yield: 76%; [a]_Dþ18.0^ꢂ(c 0.9,

1

MeOH); H NMR (300 MHz, CDCl₃): d 8.34 (br s, 1H, NH,

(g-C, Leu), 23.3 (b-C, His), 21.1 (d-C’s, Leu); C₂₅H₄₀N₆O₇

(536): Calcd. C 55.96, H 7.51, N 15.66; Found: C 55.99, H

7.52, N 15.65.

amide), 8.25 (br s, 1H, NH, amide), 7.74 (d, 1H, J ¼ 8.0 Hz,

b-H, Imz), 7.59 (s, 1H, d-H, Imz), 7.26 (d, 1H, J ¼ 7.8 Hz,

b-H, Indole), 7.23e7.11 (m, 4H, deh-H’s, Indole), 6.30 (br

s, 1H, NH, amide), 4.79 (br s, 4H, NH’s, Indole, Imz and

NH₂), 4.75e4.71 (m, 1H, a-H, Trp), 4.17e4.12 (m, 1H, a-

H, His), 3.81 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly²), 3.62 (t, 2H,

J ¼ 6.6 Hz, CH₂, Gly¹), 3.55 (s, 3H, OCH₃), 3.20e3.11 (m,

4H, b-H’s, Trp and His); ¹³C NMR (300 MHz, CDCl₃):

d 178.0 (C]O, amide), 172.8 (C]O, ester), 170.0, 169.1

6.1.1.20. Compound 4c⁰. Yield: 72%; [a]_Dþ19.8^ꢂ(c 0.9,

MeOH); IR (CHCl₃): n 3503, 3395, 3122 (NeH str.), 3058

(AreH str.), 2996, 2992 (CeH str., cyclic CH₂), 2925, 2920,

2855 (CeH str. CH₂), 1748 (C]O str. ester), 1662, 1642

(C]O str. amide), 1613 (NeH def. amine), 1560, 1424 (skel-

etal bands), 1534 (NH def. amide), 1384, 1362 (CeH def. iso-

propyl grp), 1272, 1232, 920, 885, 700 cm^ꢀ1

;

¹H NMR

(C]O, amide), 141.8 (C₂, Imz), 136.6 (C₂, Indole), 128.9

0

(C₃, Indole), 127.0 (C₄, Imz), 122.8 (C₂, Indole), 121.2,

0

(300 MHz, CDCl₃): d 8.98 (br s, 1H, NH, amide), 7.84 (d,

1H, J ¼ 7.95 Hz, b-H, Imz), 7.50 (s, 1H, d-H, Imz), 6.52 (br

s, 1H, NH, amide), 4.84e4.69 (m, 1H, a-H, Leu), 4.55 (br s,

3H, NH, Imz and NH₂, His), 4.32 (t, 1H, J ¼ 6.85 Hz, a-H,

Pro), 4.16e4.11 (m, 1H, a-H, His), 4.03 (d, 2H,

J ¼ 5.15 Hz, CH₂, Gly), 3.63 (s, 3H, OCH₃), 3.57 (t, 2H,

J ¼ 7.15 Hz, d-H’s, Pro), 2.95 (d, 2H, J ¼ 5.85 Hz, b-H’s,

His), 2.69e2.64 (m, 2H, b-H’s, Pro), 1.97e1.87 (m, 2H,

g-H’s, Pro), 1.74 (t, 2H, J ¼ 7.9 Hz, b-H’s, Leu), 1.51e1.40

(m, 1H, g-H, Leu), 0.99 (d, 6H, J ¼ 6.15 Hz, d-H’s, Leu);

¹³C NMR (300 MHz, CDCl₃): d 171.1, 170.8 (C]O, sec.

amide), 170.3 (C]O, tert. amide), 168.3 (C]O, ester),

142.8, 121.7, 111.9 (C_2,4,5, Imz), 57.6, 54.7 (a-C’s, Pro and

His), 51.8 (OCH₃), 49.3 (a-C, Leu), 47.8 (d-C, Pro), 44.1

(b-C, Leu), 40.6 (CH₂, Gly), 26.5, 26.0 (b-C’s Pro and His),

24.2, 23.8 (g-C’s, Pro and Leu), 21.6 (d-C’s, Leu);

119.6, 119.0 (C_4e6, Indole), 114.7 (C₅, Imz), 111.3 (C₃, In-

dole), 110.0 (C₇, Indole), 51.8, 50.0 (a-C’s, His and Trp),

49.6 (OCH₃), 48.0, 42.9 (CH₂, Gly²and Gly¹), 33.1, 23.7

(b-C’s, Trp and His); C₂₂H₂₇N₇O₅(469): Calcd. C 56.28, H

5.80, N 20.88; Found: C 56.25, H 5.76, N 20.90.

6.1.2. General method for the synthesis of 4-(5,6-dimethyl-

1H-benzo[d]imidazol-2-yl)-benzoic acid (5)/4-(5,6-dimethyl-

1H-benzo[d]imidazol-2-yl)-3,5-diiodobenzoic acid (6)/2-hyd-

roxy-5-(6-nitro-1H-benzo[d]imidazol-2-yl)-benzoic acid (7)/5-

(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-2-hydroxybenzoic

acid (8)

A mixture of PABA (6.9 g), dilute hydrochloric acid (15%,

30 mL) and water (45 mL) was heated to get a clear solution.

After cooling to 0 ^ꢂC, the solution was diazotized by the

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

785

1

addition of sodium nitrite solution (30%, 12 mL). To the

ﬁltrate of diazotized salt solution, 5,6-dimethylbenzimidazole

(7.3 g) and aqueous cupric chloride solution (1.3 g in 5 mL

water) were added with stirring followed by slow addition of

water (25 mL), maintaining the temperature between 5 and

10 ^ꢂC. Stirring was continued for 6 h and ﬁnally reaction mix-

ture was kept overnight in the refrigerator. The separated solid

was collected by ﬁltration and washed with cold water. The

crude product was recrystallized from acetone to get the title

compound 6. Similarly, reaction of diazotized 4-amino-3,

5-diiodobenzoic acid 1a (19.4 g) with 5,6-dimethylbenzimida-

zole (7.3 g), 5-aminosalicylic acid (7.7 g) with 6-nitrobenzimi-

dazole 1b (8.2 g), 5-aminosalicylic acid (7.7 g) with 5,

6-dimethylbenzimidazole (7.3 g) in aqueous CuCl₂afforded

compounds 7, 8 and 9, repectively.

697 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 10.6 (br s, 3H,

NH, BzImz and OH’s, Ar(OH)COOH), 8.86 (s, 1H, z-H, Ar

(OH)COOH), 8.80 (d, 1H, J ¼ 7.5 Hz, d-H, Ar(OH)COOH),

8.43 (s, 1H, h-H, BzImz), 8.02 (d, 1H, J ¼ 7.8 Hz, 3-H,

BzImz), 7.66 (d, 1H, J ¼ 7.6 Hz, d-H, BzImz), 6.80 (d, 1H,

J ¼ 7.15 Hz, g-H, Ar(OH)COOH); ¹³C NMR (300 MHz,

CDCl₃): d 175.0 (C]O, COOH), 164.4 (C₂, Ar(OH)COOH),

0

152.6 (C₂, BzImz), 141.0 (C₂, BzImz), 139.1 (C₃, BzImz),

142.2 (C₆, BzImz), 135.0 (C₆, Ar(OH)COOH), 130.2 (C₄, Ar

(OH)COOH), 122.2 (C₅, Ar(OH)COOH), 121.5 (C₅, BzImz),

117.3 (C₄, BzImz), 118.8 (C₃, Ar(OH)COOH), 111.5 (C₁, Ar

(OH)COOH), 108.4 (C₇, BzImz); C₁₄H₉N₃O₅(299): Calcd. C

56.19, H 3.03, N 14.04; Found: C 56.22, H 3.00, N 14.06.

6.1.2.4. Compound 8. Yield: 79%; m.p. 166e167 ^ꢂC; IR

(KBr): n 3488 (NeH str.), 3362 (OeH str. AreOH), 3295e

2502 (OeH str. COOH), 3066, 3025 (AreH str.), 2962, 2959,

2870 (CeH str. CH₃), 1693 (C]O str. COOH), 1580, 1433

(skeletal bands), 1408 (OeH def. COOH), 1196, 871, 823,

698 cm^ꢀ1; ¹H NMR (300 MHz, CDCl₃): d 10.5 (br s, 3H, NH,

BzImz and OH’s, Ar(OH)COOH), 8.87 (s, 1H, z-H, Ar(OH)-

COOH), 8.81 (d, 1H, J ¼ 7.55 Hz, d-H, Ar(OH)COOH), 7.31

(ss, 2H, d- and h-H’s, BzImz), 6.81 (d, 1H, J ¼ 7.2 Hz, g-H,

Ar(OH)COOH), 2.26 (ss, 6H, 3- and z-CH₃, BzImz); ¹³C

NMR (300 MHz, CDCl₃): d 175.4 (C]O, COOH), 164.5 (C₂,

6.1.2.1. Compound 5. Yield: 83%; m.p. 152e153 ^ꢂC; IR

(KBr): n 3480 (NeH str.), 3290e2508 (OeH str. COOH),

3062, 3055 (AreH str.), 2960, 2874 (CeH str. CH₃), 1692

(C]O str. COOH), 1554, 1423 (skeletal bands), 1407 (OeH

def. COOH), 1372 (CeH def. CH₃), 873, 828 (CeH def. rings)

cm^ꢀ1; ¹H NMR (300 MHz, CDCl₃): d 9.84 (br s, 2H, NH, BzImz

and OH, COOH), 8.40 (dd, 2H, J ¼ 8.95, 6.7 Hz, m-H’s,

AreCOOH), 8.06 (dd, 2H, J ¼ 8.9, 6.55 Hz, o-H’s, Ar

eCOOH), 7.29 (singlet overlapped over singlet (ss), 2H,

d- and h-H’s, BzImz), 2.27 (ss, 6H, 3- and z-CH₃, BzImz);

¹³C NMR (300 MHz, CDCl₃): d 168.4 (C]O, COOH), 152.1

0

Ar(OH)COOH), 153.2 (C₂, BzImz), 140.1 (C₂, BzImz), 138.5

0

(C₃, BzImz), 135.6 (C₆, Ar(OH)COOH), 133.9, 131.5 (C_5,6

,

0

(C₂, BzImz), 140.2 (C₂, BzImz), 137.7 (C₃, BzImz), 134.2

(C₅, BzImz), 132.4 (C₄, AreCOOH), 131.8 (C₆, BzImz), 131.2

(o-C’s, AreCOOH), 130.5 (C₁, AreCOOH), 127.6 (m-C’s,

AreCOOH), 124.2 (C₄, BzImz), 115.8 (C₇, BzImz), 20.3

(5-CH₃, BzImz), 18.8 (6-CH₃, BzImz); C₁₆H₁₄N₂O₂(266):

Calcd. C 72.17, H 5.30, N 10.52; Found: C 72.19, H 5.33,

N 10.50.

BzImz), 130.4 (C₄, Ar(OH)COOH), 127.2 (C₄, BzImz), 123.1

(C₅, Ar(OH)COOH), 119.2 (C₃, Ar(OH)COOH), 114.0 (C₇,

BzImz), 111.3 (C₁, Ar(OH)COOH), 20.3 (5-CH₃, BzImz),

18.9 (6-CH₃, BzImz); C₁₆H₁₄N₂O₃(282): Calcd. C 68.08, H

5.00, N 9.92; Found: C 68.05, H 4.96, N 9.90.

6.1.3. General method for the synthesis of amino acid/peptide

derivatives of 4-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-

benzoic acid (5)/4-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-

3,5-diiodobenzoic acid (6)

6.1.2.2. Compound 6. Yield: 78%; m.p. 179e180 ^ꢂC; IR

(KBr): n 3483 (NeH str.), 3294e2511 (OeH str. COOH),

3064, 3059 (AreH str.), 2963, 2875 (CeH str. CH₃), 1693

(C]O str. COOH), 1553, 1421 (skeletal bands), 1405 (OeH

def. COOH), 1369 (CeH def. CH₃), 875, 869 (CeH def.

Amino acid methyl ester hydrochloride/di/tri/tetrapeptide

methyl ester (0.01 mol) was dissolved in THF (75 mL). To

this, TEA (2.9 mL) was added at 0 ^ꢂC and the reaction mixture

was stirred for 15 min. Compound 5/6 (26.6/51.8 g, 0.01 mol)

in THF (75 mL) and DCC (2.1 g) were added to the above

mixture with stirring. After 36 h, the reaction mixture was ﬁl-

tered and the residue was washed with THF (30 mL). Then,

ﬁltrate was washed with 5% NaHCO₃and saturated NaCl so-

lutions (25 mL). The organic layer was dried over anhydrous

Na₂SO₄, ﬁltered and evaporated in vacuum. The crude product

was recrystallized from a mixture of chloroform and n-hexane

followed by cooling at 0 ^ꢂC.

rings), 591 (CeI str.) cm^ꢀ1; H NMR (300 MHz, CDCl₃):

1

d 9.85 (br s, 2H, NH, BzImz and OH, COOH), 8.12 (ss, 2H,

o-H’s, AreCOOH), 7.25 (ss, 2H, d- and h-H’s, BzImz), 2.26

(ss, 6H, 3- and z-CH₃, BzImz); ¹³C NMR (300 MHz,

CDCl₃): d 168.5 (C]O, COOH), 152.4 (C₂, BzImz), 140.0

(C₂, BzImz), 137.3 (C₃, BzImz), 136.6 (m-C’s, Are

COOH), 133.9 (C₅, BzImz), 133.0 (C₄, AreCOOH), 131.5

(C₆, BzImz), 130.8 (C₁, AreCOOH), 123.7 (C₄, BzImz),

116.0 (C₇, BzImz), 109.5 (o-C’s, AreCOOH), 20.2 (5-CH₃,

BzImz), 18.9 (6-CH₃, BzImz); C₁₆H₁₂I₂N₂O₂(518): Calcd.

C 37.09, H 2.33, N 5.41; Found: C 37.10, H 2.33, N 5.40.

0

6.1.3.1. Compound 5a. [a]_Dꢀ77.0^ꢂ(c 0.1, MeOH); IR (KBr):

n 3488 (NeH str.), 3065, 3052 (AreH str.), 2998, 2995 (CeH

str, cyclic CH₂), 2962, 2872 (CeH str. CH₃), 1748 (C]O str.

ester), 1660 (C]O str. tert. amide), 1558, 1425 (skeletal

;

bands), 1269, 876, 832 (CeH def. rings) cm^ꢀ^{1 1}H NMR

(300 MHz, CDCl₃): d 8.90 (br s, 1H, NH, BzImz), 8.40 (dd,

2H, J ¼ 9.0, 6.75 Hz, m-H’s, AreCO), 8.05 (dd, 2H, J ¼ 8.9,

6.1.2.3. Compound 7. Yield: 75%; m.p. 141e142 ^ꢂC; IR

(KBr): n 3490 (NeH str.), 3365 (OeH str. AreOH), 3296e

2502 (OeH str. COOH), 3065, 3028 (AreH str.), 1695

(C]O str. COOH), 1582, 1433 (skeletal bands), 1540, 1349

(NO₂str.), 1409 (OeH def. COOH), 1198, 869, 834, 825,

786

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

6.55 Hz, o-H’s, AreCO), 7.32 (s, 1H, d-H, BzImz), 7.29 (s,

1H, h-H, BzImz), 4.14 (t, 1H, J ¼ 6.85 Hz, a-H, Pro), 3.68

(t, 2H, J ¼ 7.2 Hz, d-H, Pro), 3.62 (s, 3H, OCH₃), 2.27 (s,

3H, 3-CH₃, BzImz), 2.25 (s, 3H, z-CH₃, BzImz), 2.23e2.14

(m, 2H, g-H’s, Pro), 2.06e1.98 (m, 2H, b-H’s, Pro); ¹³C

NMR (300 MHz, CDCl₃): d 174.6 (C]O, AreCO), 170.5

AreCO), 133.7 (C₅, BzImz), 132.6 (C₆, BzImz), 132.4 (C₄,

AreCO), 131.6 (o-C’s, AreCO), 128.3 (m-C’s, AreCO),

125.6 (C₄, BzImz), 114.0 (C₇, BzImz), 54.5 (a-C, Leu), 48.3

(OCH₃), 44.6 (b-C, Leu), 40.6 (CH₂, Gly), 25.2 (g-C, Leu),

21.7 (d-C’s, Leu), 19.9 (5-CH₃, BzImz), 19.0 (6-CH₃, BzImz);

MS (m/z, %): 451 (2.6), 450 (M^þ, 8.2), 435 (7.8), 419 (15.5),

391 (100), 362 (20.2), 334 (14.8), 249 (10.2), 221 (27.1), 146

(21.4), 119 (10.2), 118 (8.8), 59 (19.2), 57 (18.4), 51 (9.8), 43

(15.5), 39 (6.3), 31 (8.6), 30 (10.7), 15 (8.3).

0

(C]O, ester), 152.5 (C₂, BzImz), 139.7 (C₂, BzImz), 136.9

0

(C₃, BzImz), 133.4 (C₁, AreCO), 132.9 (C₅, BzImz), 132.5

(C₄, AreCO), 132.0 (C₆, BzImz), 130.8 (o-C’s, AreCO),

128.2 (m-C’s, AreCO), 124.9 (C₄, BzImz), 116.1 (C₇, BzImz),

63.5 (a-C, Pro), 52.4 (OCH₃), 46.2 (d-C, Pro), 28.0 (b-C, Pro),

25.8 (g-C, Pro), 20.4 (5-CH₃, BzImz), 19.1 (6-CH₃, BzImz);

MS (m/z, %): 379 (2.6), 378 (3.1), 377 (M^þ, 5.8), 362 (7.5),

346 (16.2), 318 (9.9), 249 (21.5), 221 (100), 146 (30.5), 119

(10.3), 118 (8.9), 59 (18.6), 51 (10.8), 42 (10.7), 39 (9.3),

31 (12.5), 15 (5.2).

6.1.3.4. Compound 5d. [a]_Dþ15.6^ꢂ(c 0.1, MeOH); IR (KBr):

n 3492, 3489, 3120 (NeH str.), 3373 (OeH str., Tyr), 3069,

3042, 3035 (AreH str.), 2958, 2919 (CeH str. CH₃and

CH₂), 1742 (C]O str. ester), 1633, 1625 (C]O str. amide),

1556, 1424, 1419 (skeletal bands), 1530, 1527 (NH def.

amide), 1462 (CeH def. CH₂), 1272, 882, 879, 837, 831,

1

698 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 9.38 (br s, 1H,

6.1.3.2. Compound 5b. [a]_Dꢀ59.5^ꢂ(c 0.1, MeOH); IR (KBr):

n 3494, 3332, 3122 (NeH str.), 3068, 3049 (AreH str.), 2959,

2926, 2919 (CeH str. CH₃and CH₂), 2825 (CeH str., OCH₃),

1752 (C]O str. ester), 1630 (C]O str. sec. amide), 1546,

1418 (skeletal bands), 1535 (NH def. amide), 1372 (NO₂

str.), 1269 (CeO str. ester), 1160 (CeN str. sec. amine),

NH, amide), 8.28e8.22 (m, 4H, o- and m-H’s, AreCO),

7.98 (br s, 3H, NH’s and OH), 7.65 (s, 1H, d-H, Imz), 7.35

(d, 1H, J ¼ 7.95 Hz, b-H, Imz), 7.31 (s, 1H, d-H, BzImz),

7.28 (s, 1H, h-H, BzImz), 6.95 (br s, 1H, NH, amide), 6.90

(dd, 2H, J ¼ 8.55, 5.25 Hz, o-H’s, Tyr), 6.78 (dd, 2H,

J ¼ 8.6, 4.9 Hz, m-H’s, Tyr), 5.01 (q, 1H, J ¼ 9.0 Hz, a-H,

His), 3.92 (q, 1H, J ¼ 7.9 Hz, a-H, Tyr), 3.54 (s, 3H,

OCH₃), 3.05e2.74 (m, 4H, b-H’s, Tyr and His), 2.26 (s, 3H,

3-CH₃, BzImz), 2.24 (s, 3H, z-CH₃, BzImz); ¹³C NMR

(300 MHz, CDCl₃): d 170.8 (C]O, amide), 170.1 (C]O, es-

ter), 166.3 (C]O, AreCO), 154.1 (CeOH, Tyr), 152.2 (C₂,

875, 833, 698 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃): d 8.43

;

(dd, 2H, J ¼ 8.9, 6.75 Hz, m-H’s, AreCO), 8.06 (dd, 2H,

J ¼ 8.95, 6.5 Hz, o-H’s, AreCO), 7.52 (br s, 1H, NH, amide),

7.31 (s, 1H, d-H, BzImz), 7.29 (s, 1H, h-H, BzImz), 7.20 (br s,

4H, NH’s, BzImz and guanidino grp), 4.36 (q, 1H, J ¼ 9.4 Hz,

a-H, Arg), 3.84 (q, 2H, J ¼ 7.0 Hz, d-H’s, Arg), 3.64 (s, 3H,

OCH₃), 2.26 (s, 3H, 3-CH₃, BzImz), 2.24 (s, 3H, z-CH₃,

BzImz), 2.03e1.60 (m, 4H, b- and g-H’s, Arg); ¹³C NMR

(300 MHz, CDCl₃): d 171.8 (C]O, ester), 167.4 (C]O,

AreCO), 160.5 (C]NH, Arg), 152.9 (C₂, BzImz), 138.9

0

BzImz), 141.7 (C₂, Imz), 139.6 (C₂, BzImz), 137.3 (C₃,

BzImz), 136.4 (C₁, AreCO), 134.0 (C₅, BzImz), 132.5 (C₆,

BzImz), 131.0 (C₄, AreCO), 132.7 (o-C’s, AreCO), 128.9

(o-C’s, Tyr), 128.5 (m-C’s, Tyr), 128.0 (m-C’s, AreCO),

126.0 (C₄, BzImz), 123.2 (C₄, Imz), 118.5 (g-C, Tyr), 115.3

(C₅, Imz), 113.9 (C₇, BzImz), 59.8, 52.5 (a-C, His and Tyr),

51.0 (OCH₃), 38.8 (b-C, Tyr), 20.4 (5-CH₃, BzImz), 18.9

(6-CH₃, BzImz), 16.1 (b-C, His); MS (m/z, %): 558 (M^þ,

4.8), 565 (19.3), 549 (8.7), 521 (22.4), 415 (8.4), 386 (34.8),

358 (12.4), 249 (46.7), 221 (100), 145 (29.3), 118 (12.2),

117 (8.9), 107 (11.5), 93 (19.5), 81 (13.3), 77 (4.6), 67

(9.4), 59 (18.1), 51 (8.2), 39 (6.7), 31 (10.5), 15 (6.8).

0

(C₂, BzImz), 137.4 (C₃, BzImz), 134.7 (C₁, AreCO), 133.5

(C₅, BzImz), 133.0 (C₄, AreCO), 130.8 (C₆, BzImz), 130.1

(o-C’s, AreCO), 127.9 (m-C’s, AreCO), 124.4 (C₄, BzImz),

115.0 (C₇, BzImz), 53.9 (a-C, Arg), 50.6 (OCH₃), 40.0 (d-C,

Arg), 27.9 (b-C, Arg), 24.3 (g-C, Arg), 19.5 (5-CH₃, BzImz),

18.3 (6-CH₃, BzImz).

6.1.3.3. Compound 5c. [a]_Dꢀ9.7^ꢂ(c 0.1, MeOH); IR (KBr): n

3489, 3332, 3126 (NeH str.), 3069, 3036 (AreH str.), 2960,

2925, 2917 (CeH str. CH₃and CH₂), 1746 (C]O str. ester),

1630, 1626 (C]O str. sec. amide), 1552, 1423 (skeletal

bands), 1531 (NH def. amide), 1386, 1370 (CeH def.

6.1.3.5. Compound 5e. [a]_Dꢀ7.3^ꢂ(c 0.1, MeOH); IR (KBr): n

3493, 3125 (NeH str.), 3064, 3045, 3033 (AreH str.), 2996,

2993, 2989 (CeH str. cyclic CH₂), 2963, 2958, 2919 (CeH

str. CH₃and CH₂), 1747 (C]O str. ester), 1668, 1660, 1626

(C]O str. tert. and sec. amide), 1554, 1548, 1420 (skeletal

bands), 1528 (NH def. amide), 1268 (CeO str. ester), 877,

1

CH(CH₃)₂), 1270, 879, 835, 695 cm^ꢀ1; H NMR (300 MHz,

CDCl₃): d 8.87 (br s, 1H, NH, BzImz), 8.28 (dd, 2H,

J ¼ 8.9, 6.75 Hz, o-H’s, AreCO), 8.24 (dd, 2H, J ¼ 8.9,

6.55 Hz, m-H’s, AreCO), 7.75 (br s, 1H, NH, amide), 7.30

(s, 1H, d-H, BzImz), 7.28 (s, 1H, h-H, BzImz), 6.52 (br s,

1H, NH, amide), 4.41 (q, 1H, J ¼ 6.7 Hz, a-H, Leu), 4.02

(d, 2H, J ¼ 5.1 Hz, CH₂, Gly), 3.64 (s, 3H, OCH₃), 2.27 (s,

3H, 3-CH₃, BzImz), 2.24 (s, 3H, z-CH₃, BzImz), 1.76e1.41

(m, 3H, b- and g-H’s, Leu), 1.02 (d, 6H, J ¼ 6.2 Hz, d-H’s,

Leu); ¹³C NMR (300 MHz, CDCl₃): d 171.0 (C]O, amide),

168.1 (C]O, ester), 166.2 (C]O, AreCO), 153.1 (C₂,

835, 768, 712, 692 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃):

;

d 8.89 (br s, 1H, NH, BzImz), 8.62 (br s, 1H, NH, amide),

8.25e8.13 (m, 4H, o- and m-H’s, AreCO), 7.33 (s, 1H, d-H,

BzImz), 7.28 (s, 1H, h-H, BzImz), 7.11 (t, 1H, J ¼ 6.25 Hz,

p-H, Phe), 6.98 (tt, 2H, J ¼ 6.75, 4.45 Hz, m-H’s, Phe), 6.85

(dd, 2H, J ¼ 8.8, 4.15 Hz, o-H’s, Phe), 5.04 (q, 1H,

J ¼ 5.5 Hz, a-H, Phe), 4.45e4.39 (m, 2H, a-H’s, Pro¹and

Pro²), 3.68 (t, 2H, J ¼ 7.15 Hz, d-H’s, Pro²), 3.57 (t, 2H,

J ¼ 7.2 Hz, d-H’s, Pro¹), 3.53 (s, 3H, OCH₃), 3.02 (d, 2H,

J ¼ 5.6 Hz, b-H’s, Phe), 2.70e2.63 (m, 4H, b-H’s, Pro¹and

0

BzImz), 140.2 (C₂, BzImz), 138.0 (C₃, BzImz), 135.9 (C₁,

0

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

787

Pro²), 2.28 (s, 3H, 3-CH₃, BzImz), 2.26 (s, 3H, z-CH₃, BzImz),

2.02e1.87 (m, 4H, g-H’s, Pro¹and Pro²); ¹³C NMR

(300 MHz, CDCl₃): d 173.0 (C]O, AreCO), 170.2 (C]O,

sec. amide), 169.8 (C]O, ester), 164.6 (C]O, tert. amide),

0

153.0 (C₂, BzImz), 140.2 (C₂, BzImz), 138.0 (g-C, Phe),

0

136.7 (C₃, BzImz), 135.2 (C₄, AreCO), 134.7 (C₁,

AreCO), 133.9 (C₅, BzImz), 131.4 (C₆, BzImz), 132.3

(o-C’s, AreCO), 129.0 (o-C’s, Phe), 128.5 (m-C’s, Phe),

127.6 (m-C’s, AreCO), 126.3 ( p-C, Phe), 124.1 (C₄, BzImz),

114.8 (C₇, BzImz), 59.2, 55.0, 53.7 (a-C’s, Pro¹, Pro²and

Phe), 50.6 (OCH₃), 47.3, 42.7 (d-C’s, Pro¹and Pro²), 38.0

(b-C, Phe), 33.4, 28.5 (b- and g-C’s, Pro¹), 25.4, 23.1

(b- and g-C’s, Pro²), 20.1 (5-CH₃, BzImz), 19.2 (6-CH₃,

BzImz).

¹H NMR (300 MHz, CDCl₃): d 8.98 (br s, 2H, NH’s, BzImz

and Imz), 8.39 (ss, 2H, o-H’s, AreCO), 7.92 (br s, 1H, NH,

amide), 7.75 (d, 1H, J ¼ 8.0 Hz, b-H, Imz), 7.59 (s, 1H,

d-H, Imz), 7.26 (ss, 2H, d- and h-H, BzImz), 4.84 (q, 1H,

J ¼ 9.0 Hz, a-H, His), 3.54 (s, 3H, OCH₃), 2.99 (d, 2H,

J ¼ 5.9 Hz, b-H’s, His), 2.26 (ss, 6H, 3- and z-CH₃, BzImz);

¹³C NMR (300 MHz, CDCl₃): d 175.3 (C]O, ester), 170.5

(C]O, AreCO), 156.4 (C₂, BzImz), 145.8 (C₁, AreCO),

0

141.9 (C₂, Imz), 139.2 (C₂, BzImz), 136.4 (m-C’s, AreCO),

0

135.0 (C₄, AreCO), 134.3 (C₃, BzImz), 133.5 (C₅, BzImz),

132.2 (C₆, BzImz), 126.3 (C₄, Imz), 122.6 (C₄, BzImz),

114.5 (C₅, Imz), 111.7 (C₇, BzImz), 103.5 (o-C’s, AreCO),

52.2 (a-C, His), 49.6 (OCH₃), 21.2 (b-C, His), 20.4 (5-CH₃,

BzImz), 19.0 (6-CH₃, BzImz); MS (m/z, %): 670 (2.2), 669

(M^þ, 6.2), 654 (10.6), 638 (19.2), 610 (8.6), 501 (100), 473

(25.8), 329 (4.8), 203 (6.2), 146 (22.3), 127 (5.5), 119

(10.8), 118 (9.4), 81 (12.5), 67 (9.2), 59 (16.5), 31 (12.8),

30 (8.3), 15 (5.2).

6.1.3.6. Compound 5f. [a]_Dꢀ11.8^ꢂ(c 0.1, MeOH); IR (KBr):

n 3495, 3488, 3127 (NeH str.), 3066, 3028 (AreH str.), 2964e

2937, 2868e2849 (CeH str. CH₃and CH₂), 1745 (C]O str.

ester), 1638, 1625 (C]O str. sec. amide), 1549, 1544, 1425

(skeletal bands), 1526, 1522 (NH def. amide), 1270, 885,

6.1.3.8. Compound 6b. [a]_Dꢀ20.5^ꢂ(c 0.1, MeOH); IR (KBr):

n 3479, 3475, 3122 (NeH str.), 3066, 3059, 3031 (AreH str.),

2957, 2926 (CeH str. CH₃and CH₂), 2829 (CeH str. OCH₃),

1742 (C]O str. ester), 1640 (C]O str. amide), 1558, 1551,

1425, 1419 (skeletal bands), 1539 (NH def. amide), 1464

1

832, 745, 697 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 9.35 (br

s, 1H, NH, amide), 8.92 (br s, 2H, NH’s, BzImz and Indole),

8.29e8.23 (m, 4H, o- and m-H’s, AreCO), 8.22 (br s, 1H,

NH, amide), 7.31 (s, 1H, d-H, BzImz), 7.29 (s, 1H, h-H,

BzImz), 7.25 (d, 1H, J ¼ 7.85 Hz, b-H, Indole), 7.23e7.10

(m, 4H, deh-H’s, Indole), 7.07 (br s, 1H, NH, amide), 6.68

(br s, 1H, NH, amide), 4.75e4.68 (m, 1H, a-H, Trp), 4.08

(t, 1H, J ¼ 8.6 Hz, a-H, Ile), 3.83 (d, 2H, J ¼ 5.15 Hz, CH₂,

Gly), 3.81e3.72 (m, 1H, a-H, Ala), 3.59 (s, 3H, OCH₃), 3.20

(d, 2H, J ¼ 5.65 Hz, b-H’s, Trp), 2.27 (s, 3H, 3-CH₃, BzImz),

2.26 (s, 3H, z-CH₃, BzImz), 1.57e1.32 (m, 3H, b- and

g-H’s, Ile), 1.28 (d, 3H, J ¼ 5.85 Hz, b-H’s, Ala), 1.01e0.94

(m, 6H, g⁰- and d-H’s, Ile); ¹³C NMR (300 MHz, CDCl₃):

d 170.1 (C]O, ester), 169.8 (C]O, amide), 167.4 (C]O,

AreCO), 165.9 (C]O, amide), 163.6 (C]O, amide), 152.7

1

(CeH def. CH₂), 1267, 885, 876, 770, 705, 593 cm^ꢀ1; H

NMR (300 MHz, CDCl₃): d 8.94 (br s, 2H, NH’s, BzImz

and Imz), 8.37 (ss, 2H, o-H’s, AreCO), 7.93 (br s, 1H, NH,

amide), 7.51 (d, 1H, J ¼ 7.8 Hz, b-H, Indole), 7.26 (ss, 2H,

d- and h-H, BzImz), 7.16e7.02 (m, 4H, deh-H’s, Indole),

4.95e4.87 (m, 1H, a-H, Trp), 3.55 (s, 3H, OCH₃), 3.26 (d,

2H, J ¼ 5.7 Hz, b-H’s, Trp), 2.26 (ss, 6H, 3- and z-CH₃,

BzImz); ¹³C NMR (300 MHz, CDCl₃): d 169.8 (C]O, ester),

168.4 (C]O, AreCO), 156.3 (C₂, BzImz), 144.7 (C₄, Ar

0

eCO), 139.6 (C₂, BzImz), 136.5 (o-C’s, AreCO), 135.4

0

(C₂, Indole), 134.7 (C₁, AreCO), 134.1 (C₃, BzImz), 133.5

0

(C₂, BzImz), 139.5 (C₂, BzImz), 137.2 (C₃, BzImz), 136.4

0

(C₅, BzImz), 132.4 (C₆, BzImz), 128.2 (C₃, Indole), 122.8

0

(C₂, Indole), 134.8 (C₄, AreCO), 133.2 (C₅, BzImz), 131.3

(C₆, BzImz), 129.4 (m-C’s, AreCO), 129.1 (C₁, AreCO),

0

127.2 (o-C’s, AreCO), 126.1 (C₃, Indole), 124.2 (C₄, BzImz),

(C₂, Indole), 121.9 (C₄, BzImz), 119.8, 118.9, 118.1, 114.7

(C_3e6, Indole), 112.7 (C₇, BzImz), 110.2 (C₇, Indole), 104.5

(m-C’s, AreCO), 55.6 (a-C, Trp), 49.3 (OCH₃), 19.7, 19.2

(5,6-CH₃, BzImz), 16.8 (b-C, Trp).

122.5 (C₂, Indole), 120.6, 119.2, 118.3 (C_4e6, Indole), 114.8

(C₇, BzImz), 111.9 (C₃, Indole), 109.6 (C₇, Indole), 59.1

(a-C, Trp), 52.5 (a-C, Ile), 49.2 (OCH₃), 47.5 (a-C, Ala),

40.6 (CH₂, Gly), 34.5, 26.4 (b- and g-C’s, Ile), 22.5 (b-C,

Trp), 20.2, 19.1 (5,6-CH₃, BzImz), 17.7 (b-C, Ala), 14.3 (g⁰-

C, Ile), 9.7 (d-C, Ile); MS (m/z, %): 709 (4.2), 708 (3.2), 707

(M^þ, 6.2), 692 (11.8), 676 (19.5), 605 (15.5), 577 (9.2), 492

(28.4), 464 (100), 435 (19.2), 407 (7.3), 249 (11.6), 221

(30.2), 146 (22.5), 130 (9.5), 119 (11.8), 118 (9.4), 116 (7.7),

59 (20.2), 51 (7.9), 43 (15.1), 39 (5.5), 31 (9.6), 30 (12.3), 29

(4.8), 15 (8.2).

6.1.3.9. Compound 6c. [a]_Dꢀ96.4^ꢂ(c 0.1, MeOH); IR

(KBr): n 3480, 3128 (NeH str.), 3065, 3030 (AreH str.),

2957, 2870 (CeH str. CH₃), 1740 (C]O str. ester), 1641

(C]O str. amide), 1562, 1420, 1418 (skeletal bands),

1538 (NH def. amide), 1422, 1329 (OeH def.), 1269,

1093, 883, 875, 660, 602 cm^ꢀ1

;

¹H NMR (300 MHz,

CDCl₃): d 8.36 (ss, 2H, o-H’s, AreCO), 7.47 (br s, 1H,

NH, amide), 7.26 (ss, 2H, d- and h-H, BzImz), 6.10 (br

s, 2H, NH, BzImz and OH, Thr), 4.62e4.53 (m, 1H, b-H,

Thr), 4.49 (t, 1H, J ¼ 3.95 Hz, a-H, Thr), 3.62 (s, 3H,

OCH₃), 2.28 (ss, 6H, 3- and z-CH₃, BzImz), 1.34 (d, 3H,

J ¼ 4.9 Hz, g-H’s, Thr); ¹³C NMR (300 MHz, CDCl₃):

d 173.6 (C]O, ester), 168.7 (C]O, AreCO), 156.4 (C₂,

0

BzImz), 143.8 (C₁, AreCO), 140.0 (C₂, BzImz), 138.5

0

(m-C’s, AreCO), 137.2 (C₄, AreCO), 135.0 (C₃, BzImz),

133.9 (C₅, BzImz), 132.4 (C₆, BzImz), 122.5 (C₄, BzImz),

6.1.3.7. Compound 6a. [a]_Dꢀ38.5^ꢂ(c 0.1, MeOH); IR (KBr):

n 3482, 3479, 3125 (NeH str.), 3069, 3062 (AreH str.), 2955,

2923 (CeH str. CH₃and CH₂), 1745 (C]O str. ester), 1642

(C]O str. amide), 1559, 1422, 1416 (skeletal bands), 1545

(NH def. amide), 1466 (CeH def. CH₂), 1270 (CeO str. es-

ter), 882, 878, 872 (CeH def. ring), 588 (CeI str.) cm^ꢀ1

;

788

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

112.7 (C₇, BzImz), 104.2 (o-C’s, AreCO), 68.4 (b-C, Thr),

57.9 (a-C, Thr), 52.1 (OCH₃), 20.2 (g-C, Thr), 19.7 (5-CH₃,

BzImz), 19.1 (6-CH₃, BzImz); MS (m/z, %): 635 (2.1), 634

(3.5), 633 (M^þ, 4.6), 618 (11.5), 602 (18.9), 574 (12.6), 501

(25.1), 473 (100), 329 (5.9), 203 (6.7), 146 (20.2), 127

(8.2), 119 (6.8), 118 (12.4), 59 (14.6), 45 (7.2), 31 (11.9),

17 (1.4), 15 (5.5).

45.5 (d-C, Pro), 29.6 (b-C, Pro), 24.8 (g-C, Pro), 19.9, 19.2

(5,6-CH₃, BzImz), 16.9 (b-C, His).

6.1.3.12. Compound 6f. [a]_Dꢀ76.8^ꢂ(c 0.1, MeOH); IR

(KBr): n 3490, 3130 (NeH str.), 3372 (OeH str., Tyr),

3065, 3045, 3033 (AreH str.), 2962, 2955, 2917 (CeH str.

CH₃and CH₂), 1748 (C]O str. ester), 1631, 1622 (C]O

str. amide), 1558, 1425, 1417 (skeletal bands), 1532, 1527

(NH def. amide), 1465 (CeH def. CH₂), 1268, 881, 872,

6.1.3.10. Compound 6d. [a]_Dþ26.5^ꢂ(c 0.1, MeOH); IR (KBr):

n 3490, 3125 (NeH str.), 3069, 3053 (AreH str.), 2997, 2992

(CeH str. cyclic CH₂), 2960, 2925, 2917 (CeH str. CH₃and

CH₂), 1750 (C]O str. ester), 1659, 1623 (C]O str. tert. and

sec. amide), 1548, 1420 (skeletal bands), 1533 (NH def. amide),

1370 (NO₂str.), 1268, 1159, 884, 873, 698, 596 cm^ꢀ1; ¹H NMR

(300 MHz, CDCl₃): d 8.62 (br s, 1H, NH, amide), 8.44 (ss, 2H,

o-H’s, AreCO), 7.26 (ss, 2H, d- and h-H’s, BzImz), 7.22 (br s,

4H, NH’s, guanidino group and BzImz), 4.80e4.75 (m, 1H,

a-H, Arg), 4.31e4.28 (m, 1H, a-H, Pro), 3.87e3.82 (m, 2H,

d-H’s, Arg), 3.65 (s, 3H, OCH₃), 3.45e3.41 (m, 2H, d-H’s,

Pro), 2.69e2.64 (m, 2H, b-H’s, Pro), 2.27 (s, 3H, 3-CH₃,

BzImz), 2.26 (s, 3H, z-CH₃, BzImz), 2.02e1.60 (m, 6H,

b- and g-H’s, Arg and g-H’s, Pro); ¹³C NMR (300 MHz,

CDCl₃): d 170.4 (C]O, ester), 169.7 (C]O, amide), 165.6

(C]O, AreCO), 160.2 (C]NH), 155.4 (C₂, BzImz), 143.5

825, 690, 590 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃): d 9.96

;

(br s, 1H, NH, amide), 9.32 (br s, 1H, NH, amide), 8.45

(ss, 2H, o-H’s, AreCO), 7.42 (br s, 2H, NH, BzImz and

OH, Tyr), 7.26 (ss, 2H, d- and h-H, BzImz), 7.12 (br s, 1H,

NH, amide), 7.01e6.88 (m, 4H, o- and m-H’s, Tyr), 4.33

(q, 1H, J ¼ 8.0 Hz, a-H, Tyr), 4.28e4.23 (m, 1H, a-H, Ala),

4.03 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly), 3.65 (s, 3H, OCH₃),

2.88 (d, 2H, J ¼ 5.5 Hz, b-H’s, Tyr), 2.27 (ss, 6H, 3- and

z-CH₃, BzImz), 1.51 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala); ¹³C

NMR (300 MHz, CDCl₃): d 170.1 (C]O, ester), 168.5

(C]O, amide), 166.8 (C]O, amide), 163.9 (C]O, Are

CO), 156.3 (C₂, BzImz), 153.5 (CeOH, Tyr), 144.7 (C₄,

0

AreCO), 138.8 (o-C’s, AreCO), 137.5 (C₂, BzImz), 136.1

0

(C₁, AreCO), 134.9 (C₃, BzImz), 133.6 (C₅, BzImz), 132.4

(C₆, BzImz), 130.6 (o-C’s, Tyr), 128.8 (m-C’s, Tyr), 126.5

(g-C, Tyr), 122.2 (C₄, BzImz), 115.7 (C₇, BzImz), 105.8

(m-C’s, AreCO), 53.4 (OCH₃), 50.5 (a-C, Ala), 47.5 (a-C,

Tyr), 41.6 (CH₂, Gly), 36.3 (b-C, Tyr), 20.4, 18.8 (5,6-CH₃,

BzImz), 17.4 (b-C, Ala); MS (m/z, %): 824 (2.2), 823 (M^þ,

6.2), 808 (10.2), 792 (17.4), 764 (12.4), 735 (38.2), 707

(14.9), 572 (100), 544 (10.5), 501 (16.4), 473 (26.5), 329

(12.9), 203 (5.3), 146 (15.1), 127 (8.7), 119 (9.9), 118

(12.5), 107 (11.2), 93 (3.8), 59 (14.5), 31 (14.8), 30 (4.4),

15 (2.5).

0

(C₄, AreCO), 139.2 (o-C’s, AreCO), 136.6 (C₂, BzImz),

0

134.5 (C₁, AreCO), 134.1 (C₃, BzImz), 133.8 (C₅, BzImz),

130.2 (C₆, BzImz), 122.7 (C₄, BzImz), 113.7 (C₇, BzImz),

104.3 (m-C’s, AreCO), 58.2 (a-C, Pro), 51.7 (OCH₃), 48.4

(a-C, Arg), 43.5, 40.4 (d-C’s, Pro and Arg), 29.8, 27.7 (b-C’s,

Pro and Arg), 24.2, 22.3 (g-C’s, Arg and Pro), 19.3, 18.9

(5,6-CH₃, BzImz); MS (m/z, %): 830 (M^þ, 6.8), 815 (11.2),

799 (24.4), 771 (14.8), 598 (100), 571 (14.7), 501 (19.6), 473

(29.4), 329 (8.9), 203 (6.2), 146 (16.2), 127 (6.6), 119 (6.9),

118 (11.3), 59 (14.2), 46 (3.7), 42 (5.5), 31 (10.2), 30 (4.9),

15 (3.7).

6.1.3.13. Compound 6g. [a]_Dꢀ19.9^ꢂ(c 0.1, MeOH); IR

(KBr): n 3470, 3116 (NeH str.), 3071, 3052 (AreH str.),

2997, 2992 (CeH str. cyclic CH₂), 2961, 2924 (CeH str.

CH₃and CH₂), 1752 (C]O str. ester), 1659, 1628 (C]O

str. amide), 1556, 1422, 1417 (skeletal bands), 1462 (CeH

def. CH₂), 1385, 1369 (CeH def. isopropyl grp), 1269, 883,

6.1.3.11. Compound 6e. [a]_Dþ6.0^ꢂ(c 0.1, MeOH); IR (KBr):

n 3479, 3475, 3122 (NeH str.), 3078, 3055 (AreH str.), 2996,

2990 (CeH str. cyclic CH₂), 2957, 2922 (CeH str. CH₃and

CH₂), 1744 (C]O str. ester), 1655, 1626 (C]O str. amide),

1557, 1420, 1414 (skeletal bands), 1463 (CeH def. CH₂),

870, 765, 705, 595 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃):

;

1271, 886, 876, 870, 595 cm^ꢀ1

;

¹H NMR (300 MHz,

d 9.38 (br s, 1H, NH, amide), 8.90 (br s, 1H, NH, BzImz),

8.46 (ss, 2H, o-H’s, AreCO), 7.84 (br s, 1H, NH, amide),

7.26 (ss, 2H, d- and h-H, BzImz), 7.19 (tt, 2H, J ¼ 7.15,

4.4 Hz, m-H’s, Phe), 7.00 (t, 1H, J ¼ 6.2 Hz, p-H, Phe),

6.83 (dd, 2H, J ¼ 8.75, 4.15 Hz, o-H’s, Phe), 4.53 (q, 1H,

J ¼ 5.55 Hz, a-H, Phe), 4.18 (t, 1H, J ¼ 5.85 Hz, a-H, Val),

3.66 (t, 1H, J ¼ 6.85 Hz, a-H, Pro), 3.62 (s, OCH₃), 3.11

(t, 2H, J ¼ 7.2 Hz, d-H’s, Pro), 2.79 (d, 2H, J ¼ 5.65 Hz,

b-H’s, Phe), 2.27 (ss, 6H, 3- and z-CH₃, BzImz), 2.07e1.96

(m, 5H, b- and g-H’s, Pro and b-H, Val), 1.04 (d, 6H,

J ¼ 4.55 Hz, g-H’s, Val); ¹³C NMR (300 MHz, CDCl₃):

d 169.7 (C]O, ester), 166.9 (C]O, amide), 166.3 (C]O,

amide), 165.5 (C]O, AreCO), 157.2 (C₂, BzImz), 145.2

(C₄, AreCO), 140.8 (C₁, Phe), 138.9 (o-C’s, AreCO),

CDCl₃): d 8.97 (br s, 2H, NH’s, BzImz and Imz), 8.86 (br s,

1H, NH, amide), 8.52 (ss, 2H, o-H’s, AreCO), 7.68 (d, 1H,

J ¼ 7.95 Hz, b-H, Imz), 7.50 (s, 1H, d-H, Imz), 7.25 (ss, 2H,

d- and h-H, BzImz), 4.87 (q, 1H, J ¼ 9.0 Hz, a-H, His),

3.92 (t, 1H, J ¼ 6.85 Hz, a-H, Pro), 3.62 (s, 3H, OCH₃),

3.39 (t, 2H, J ¼ 7.2 Hz, d-H’s, Pro), 2.95 (d, 2H,

J ¼ 5.85 Hz, b-H’s, His), 2.28 (ss, 6H, 3- and z-CH₃, BzImz),

2.07e1.95 (m, 4H, b- and g-H’s, Pro); ¹³C NMR (300 MHz,

CDCl₃): d 173.7 (C]O, ester), 169.0 (C]O, AreCO),

164.3 (C]O, tert. amide), 155.7 (C₂, BzImz), 143.2 (C₁,

0

AreCO), 140.4 (C₂, Imz), 139.0 (C₂, BzImz), 136.4 (m-C’s,

0

AreCO), 135.6 (C₃, BzImz), 134.2 (C₄, AreCO), 133.9

(C₅, BzImz), 132.7 (C₆, BzImz), 129.0 (C₄, Imz), 121.9 (C₄,

BzImz), 117.2 (C₅, Imz), 111.8 (C₇, BzImz), 103.5 (o-C’s,

AreCO), 58.9 (a-C, Pro), 56.7 (a-C, His), 53.6 (OCH₃),

0

136.8 (C₂, BzImz), 136.1 (C₁, AreCO), 134.5 (C₃, BzImz),

133.3 (C₅, BzImz), 131.5 (C₆, BzImz), 130.4 (o-C’s, Phe),

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

789

128.6 (m-C’s, Phe), 127.2 ( p-H, Phe), 122.0 (C₄, BzImz),

113.7 (C₇, BzImz), 104.7 (m-C’s, AreCO), 59.1 (a-C, Pro),

54.7 (a-C, Phe), 53.4 (OCH₃), 52.1 (a-C, Val), 45.6

(d-C, Pro), 38.1 (b-C, Phe), 30.5 (b-C, Val), 28.8, 24.7

(b- and g-C, Pro), 20.3, 19.1 (5,6-CH₃, BzImz), 18.4

(g-C’s, Val).

by evaporation in vacuum. Crude product was crystallized

from a mixture of ethyl acetate and petroleum ether.

6.1.4.1. Compound 7a. [a]_Dꢀ86.2^ꢂ(c 0.1, MeOH); IR (KBr):

n 3496, 3115 (NeH str.), 3368 (OeH str., AreCO), 3069,

3032 (AreH str.), 2925, 2918, 2850 (CeH str. CH₂), 2822

(CeH str., OCH₃), 1750 (C]O str. ester), 1638 (C]O str.

sec. amide), 1585, 1435 (skeletal bands), 1542, 1350 (NO₂

str.), 1538 (NH def. amide), 1267, 1202, 1160, 871, 840,

6.1.3.14. Compound 6h. [a]_Dꢀ113.8^ꢂ(c 0.1, MeOH); IR

(KBr): n 3490, 3135 (NeH str.), 3074, 3036 (AreH str.),

2962, 2955, 2873 (CeH str. CH₃), 1755 (C]O str. ester),

1647, 1642 (C]O str. amide), 1566, 1426, 1417 (skeletal

bands), 1538, 1535 (NH def. amide), 1459 (CeH def. CH₂),

1

829, 695 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.75 (s, 1H,

z-H, AreCO), 8.59 (d, 1H, J ¼ 7.45 Hz, d-H, AreCO), 8.43

(s, 1H, h-H, BzImz), 8.03 (d, 1H, J ¼ 7.75 Hz, 3-H, BzImz),

7.67 (d, 1H, J ¼ 7.65 Hz, d-H, BzImz), 7.52 (d, 1H, J ¼

7.2 Hz, g-H, AreCO), 6.62 (br s, 5H, NH’s, BzImz, guanidino

grp and OH, AreCO), 6.52 (br s, 1H, NH, amide), 4.36 (q, 1H,

J ¼ 9.45 Hz, a-H, Arg), 3.84 (q, 2H, J ¼ 6.95 Hz, d-H, Arg),

3.65 (s, 3H, OCH₃), 2.01e1.60 (m, 4H, b- and g-H’s, Arg);

¹³C NMR (300 MHz, CDCl₃): d 173.2 (C]O, amide), 170.3

(C]O, ester), 160.6 (C]NH), 156.2 (C₂, AreCO), 153.2

1420, 1332 (OeH def.), 1267, 1089, 879, 871, 658, 597 cm^ꢀ1

;

¹H NMR (300 MHz, CDCl₃): d 9.25 (br s, 1H, NH, amide),

8.49 (ss, 2H, o-H’s, AreCO), 8.45 (br s, 1H, NH, amide), 7.25

(ss, 2H, d- and h-H, BzImz), 6.67 (br s, 1H, NH, amide), 6.25

(br s, 1H, NH, amide), 6.09 (br s, 2H, NH, BzImz and OH,

Thr), 4.65e4.56 (m, 1H, b-H, Thr), 4.09 (t, 1H, J ¼ 8.6 Hz,

a-H, Ile), 3.94 (d, 2H, J ¼ 5.1 Hz, CH₂, Gly¹), 3.92 (d, 2H,

J ¼ 5.1 Hz, CH₂, Gly²), 3.78 (t, 1H, J ¼ 3.95 Hz, a-H, Thr),

3.60 (s, 3H, OCH₃), 2.25 (ss, 6H, 3- and z-CH₃, BzImz),

2.10e2.02 (m, 1H, b-H, Ile), 1.67e1.52 (m, 2H, g-H’s, Ile),

1.32 (d, 3H, J ¼ 4.95 Hz, g-H’s, Thr), 1.02 (d, 3H, J ¼ 5.9 Hz,

g⁰-H’s, Ile), 0.96 (t, 3H, J ¼ 7.75 Hz, d-H’s, Ile); ¹³C NMR

(300 MHz, CDCl₃): d 176.0 (C]O, amide), 172.2 (C]O,

ester), 171.2, 169.8 (C]O, amide), 167.1 (C]O, AreCO),

156.1 (C₂, BzImz), 143.7 (C₁, AreCO), 138.6 (m-C’s,

0

(C₂, BzImz), 145.1 (C₃, BzImz), 142.3 (C₆, BzImz), 139.2

0

(C₂, BzImz), 134.8 (C₄, AreCO), 128.6 (C₆, AreCO),

124.5 (C₁, AreCO), 121.1 (C₅, AreCO), 119.5 (C₅, BzImz),

118.4 (C₄, BzImz), 116.2 (C₃, AreCO), 110.4 (C₇, BzImz),

54.2 (a-C, Arg), 50.7 (OCH₃), 39.7 (d-C, Arg), 27.8 (b-C,

Arg), 24.2 (g-C, Arg); MS (m/z, %): 515 (2.2), 514 (M^þ,

4.8), 499 (12.6), 483 (19.2), 455 (16.1), 282 (100), 254

(25.7), 163 (15.8), 145 (19.4), 136 (11.6), 135 (26.2), 131

(18.9), 117 (16.6), 103 (7.3), 66 (10.3), 65 (12.2), 59 (16.6),

46 (5.4), 31 (10.9), 17 (2.3), 15 (1.4).

0

AreCO), 137.8 (C₂, BzImz), 136.8 (C₄, AreCO), 134.6 (C₃,

BzImz), 133.9 (C₅, BzImz), 132.1 (C₆, BzImz), 121.9 (C₄,

BzImz), 113.0 (C₇, BzImz), 102.7 (o-C’s, AreCO), 67.8 (b-C,

Thr), 58.1 (a-C, Thr), 53.0 (OCH₃), 48.9 (a-C, Ile), 46.3, 42.4

(CH₂, Gly²and Gly¹), 33.9 (b-C, Ile), 28.4 (g-C, Ile), 20.4

(g-C, Thr), 19.8, 18.9 (5,6-CH₃, BzImz), 15.1 (g⁰-C, Ile), 10.2

(d-C, Ile); MS (m/z, %): 862 (2.4), 861 (3.1), 860 (M^þ, 6.4),

845 (11.8), 829 (19.7), 801 (7.3), 728 (30.5), 700 (12.5), 671

(100), 643 (17.3), 558 (32.2), 530 (10.7), 501 (28.3), 473

(21.3), 329 (11.5), 203 (6.8), 146 (26.3), 127 (12.2), 119

(12.4), 118 (8.5), 59 (17.4), 57 (8.6), 31 (11.3), 30 (15.8), 29

(6.1), 15 (3.2).

6.1.4.2. Compound 7b. [a]_Dꢀ68.3^ꢂ(c 0.1, MeOH); IR (KBr): n

3496, 3489, 3115 (NeH str.), 3366 (OeH str., AreCO), 3066,

3048, 3035 (AreH str.), 2923, 2852 (CeH str. CH₂), 2826 (Ce

H str., OCH₃), 1745 (C]O str. ester), 1642 (C]O str. sec. am-

ide), 1588, 1430, 1422 (skeletal bands), 1548 (NH def. amide),

1539, 1352 (NO₂str.), 1273, 1197, 870, 844, 827, 758,

1

697 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.76 (s, 1H, z-H,

AreCO), 8.58 (d, 1H, J ¼ 7.45 Hz, d-H, AreCO), 8.45 (s, 1H,

h-H, BzImz), 8.02 (d, 1H, J ¼ 7.75 Hz, 3-H, BzImz), 7.67 (d,

1H, J ¼ 7.6 Hz, d-H, BzImz), 7.52 (d, 1H, J ¼ 7.8 Hz, b-H, In-

dole), 7.35 (br s, 3H, NH’s, BzImz, Indole and OH, AreCO),

7.16e6.97 (m, 5H, deh-H’s, Indole and g-H, AreCO), 6.50

(br s, 1H, NH, amide), 4.93 (q, 1H, J ¼ 6.1 Hz, a-H, Trp), 3.56

(s, 3H, OCH₃), 3.21 (d, 2H, J ¼ 5.65 Hz, b-H’s, Trp); ¹³C NMR

(300 MHz, CDCl₃): d 174.7 (C]O, AreCO), 169.6 (C]O, es-

6.1.4. General method for the synthesis of amino acid/peptide

derivatives of 2-hydroxy-5-(6-nitro-1H-benzo[d]imidazol-2-

yl)-benzoic acid (7)/5-(5,6-dimethyl-1H-benzo[d]imidazol-

2-yl)-2-hydroxybenzoic acid (8)

0

ter), 156.4 (C₂, AreCO), 153.3 (C₂, BzImz), 144.2 (C₃, BzImz),

To a mixture of ^L-amino acid methyl ester hydrochloride/di/

tri/tetrapeptide methyl ester (0.01 mol) in DMF (50 mL),

NMM (2.3 mL) was added at 0 ^ꢂC with stirring. Compound

7/8 (29.9/28.2 g, 0.01 mol) in DMF (50 mL) and DCC

(2.1 g) were added to the above mixture and stirring was

done for 24 h. After 24 h, the reaction mixture was ﬁltered.

To the ﬁltrate, water is added in equal proportions and aqueous

layer was washed with ether (150 mL) in three proportions.

The organic layer was separated and dried over anhydrous

Na₂SO₄, ﬁltered and evaporated in vacuum. The product

obtained was dissolved in chloroform, washed with 10%

HCl, saturated NaHCO₃solution and water (25 mL) followed

0

142.0 (C₆, BzImz), 139.1 (C₂, BzImz), 135.9 (C₂, Indole), 134.6

0

(C₄, AreCO), 129.4 (C₃, Indole), 128.2 (C₆, AreCO), 122.6 (C₂,

Indole), 121.8 (C₆, Indole), 121.0 (C₁, AreCO), 119.9 (C₅, Are

CO), 119.2 (C₅, Indole), 118.6 (C₅, BzImz), 118.4 (C₄, BzImz),

118.0 (C₄, Indole), 116.6 (C₃, AreCO), 111.2 (C₇, Indole),

109.5 (C₃, Indole), 107.9 (C₇, BzImz), 55.5 (a-C, Trp), 49.3

(OCH₃), 28.3 (b-C, Trp).

6.1.4.3. Compound 7c. [a]_Dꢀ7.2^ꢂ(c 0.1, MeOH); IR (KBr): n

3492, 3127, 3112 (NeH str.), 3362 (OeH str., AreCO), 3066,

3028 (AreH str.), 2922, 2852, 2845 (CeH str. CH₂), 2825

790

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

(CeH str., OCH₃), 1747 (C]O str. ester), 1644, 1636 (C]O

str. sec. amide), 1589, 1432 (skeletal bands), 1544 (NH def.

amide), 1539, 1348 (NO₂str.), 1262, 1198, 872, 840, 828,

BzImz), 7.05 (br s, 2H, NH, BzImz and OH, AreCO), 7.00

(d, 1H, J ¼ 7.2 Hz, g-H, AreCO), 4.41 (t, 1H, J ¼ 6.8 Hz,

a-H, Pro¹), 4.23e4.18 (m, 2H, a-H’s, Pro²and Pro³), 3.73

(t, 2H, J ¼ 7.15 Hz, d-H’s, Pro³), 3.65 (t, 2H, J ¼ 5.85 Hz,

d-H’s, Pro²), 3.61 (s, OCH₃), 3.52 (t, 2H, J ¼ 7.2 Hz, d-H’s,

Pro¹), 2.79e2.68 (m, 4H, b-H’s, Pro^1,2), 2.08e1.88 (m, 8H,

b-H’s, Pro³and g-H’s, Pro^1e3); ¹³C NMR (300 MHz,

CDCl₃): d 171.4 (C]O, amide), 168.7 (C]O, ester), 168.2

(C]O, amide), 166.2 (C]O, AreCO), 157.7 (C₂, AreCO),

1

692 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.95 (s, 1H, z-H,

AreCO), 8.66 (br s, 1H, NH, amide), 8.59 (d, 1H,

J ¼ 7.45 Hz, d-H, AreCO), 8.42 (s, 1H, h-H, BzImz), 8.14

(br s, 1H, NH, amide), 8.02 (d, 1H, J ¼ 7.75 Hz, 3-H, BzImz),

7.66 (d, 1H, J ¼ 7.6 Hz, d-H, BzImz), 7.01 (d, 1H,

J ¼ 7.15 Hz, g-H, AreCO), 6.58 (br s, 2H, NH, BzImz and

OH, AreCO), 4.02 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly²), 3.91 (d,

2H, J ¼ 5.15 Hz, CH₂, Gly¹), 3.50 (s, OCH₃); ¹³C NMR

(300 MHz, CDCl₃): d 170.1 (C]O, ester), 168.5 (C]O,

amide), 166.6 (C]O, AreCO), 157.4 (C₂, AreCO), 153.2

0

153.3 (C₂, BzImz), 144.5 (C₃, BzImz), 141.2 (C₆, BzImz),

0

138.4 (C₂, BzImz), 135.9 (C₄, AreCO), 127.5 (C₆, Are

CO), 124.2 (C₁, AreCO), 121.4 (C₅, AreCO), 119.6 (C₅,

BzImz), 118.7 (C₄, BzImz), 116.1 (C₃, AreCO), 109.7 (C₇,

BzImz), 59.4, 57.6, 55.2 (a-C’s, Pro^1e3), 53.7 (OCH₃), 46.7,

44.5, 43.1 (d-C’s, Pro^1e3), 30.6, 29.4, 28.1 (b-C’s, Pro^1e3),

27.3, 24.5, 23.2 (g-C’s, Pro^1e3); MS (m/z, %): 604 (M^þ,

8.8), 589 (11.1), 573 (20.2), 545 (13.7), 476 (19.2), 448

(14.3), 379 (100), 351 (16.3), 282 (51.1), 254 (17.4), 163

(17.1), 136 (12.6), 135 (27.7), 66 (11.3), 65 (14.2), 59

(19.7), 46 (9.3), 42 (29.7), 31 (10.5), 17 (2.5), 15 (1.7).

0

(C₂, BzImz), 144.3 (C₃, BzImz), 141.2 (C₆, BzImz), 139.1

0

(C₂, BzImz), 136.8 (C₄, AreCO), 127.7 (C₆, AreCO),

124.5 (C₁, AreCO), 121.3 (C₅, AreCO), 119.6 (C₅, BzImz),

118.5 (C₄, BzImz), 116.4 (C₃, AreCO), 109.2 (C₇, BzImz),

53.4 (OCH₃), 40.4, 40.1 (CH₂, Gly¹and Gly²); MS (m/z,

%): 428 (1.2), 427 (M^þ, 5.6), 412 (12.2), 396 (18.7), 368

(14.8), 339 (100), 311 (9.7), 282 (54.8), 254 (20.4), 163

(19.3), 136 (10.4), 135 (25.7), 66 (9.8), 65 (10.8), 59 (14.5),

46 (7.3), 31 (11.5), 17 (1.8), 15 (0.8).

6.1.4.6. Compound 7f. [a]_Dꢀ34.2^ꢂ(c 0.1, MeOH); IR (KBr):

n 3492, 3488, 3132 (NeH str.), 3358 (OeH str, AreCO),

3055, 3042, 3110 (AreH str.), 2922, 2852 (CeH str. CH₂),

1754 (C]O str. ester), 1644, 1640 (C]O str. amide), 1567,

1560, 1267, 1426, 1420 (skeletal bands), 1539, 1351 (NO₂

str.), 1389, 1367 (CeH def. isopropyl grp), 1268, 1205, 869,

6.1.4.4. Compound 7d. [a]_Dꢀ16.2^ꢂ(c 0.1, MeOH); IR (KBr):

n 3488, 3138 (NeH str.), 3359 (OeH str., AreCO), 3060,

3053 (AreH str.), 2996, 2990 (CeH str., cyclic CH₂), 2959,

2871 (CeH str. CH₃), 2824 (CeH str., OCH₃), 1748 (C]O

str. ester), 1662, 1639 (C]O str. amide), 1566, 1424 (skeletal

bands), 1543 (NH def. amide), 1538, 1348 (NO₂str.), 1262,

845, 840, 829, 765, 709, 690 cm^ꢀ^{1 1}H NMR (300 MHz,

;

CDCl₃): d 8.95 (s, 1H, z-H, AreCO), 8.58 (d, 1H,

J ¼ 7.45 Hz, d-H, AreCO), 8.41 (s, 1H, h-H, BzImz), 8.02

(d, 1H, J ¼ 7.8 Hz, 3-H, BzImz), 7.94 (br s, 1H, NH, amide),

7.85 (br s, 1H, NH, amide), 7.74 (d, 1H, J ¼ 8.0 Hz, b-H, Imz),

7.66 (d, 1H, J ¼ 7.6 Hz, d-H, BzImz), 7.60 (s, 1H, d-H, Imz),

7.39 (br s, 3H, NH’s, BzImz, Imz and OH, AreCO), 7.20e

7.14 (m, 2H, m-H’s, Phe), 7.00 (t, 1H, J ¼ 6.15 Hz, p-H,

Phe), 6.95 (br s, 1H, NH, amide), 6.91 (d, 1H, J ¼ 7.2 Hz,

g-H, AreCO), 6.84 (dd, 2H, J ¼ 8.8, 4.15 Hz, o-H’s, Phe),

4.33 (t, 1H, J ¼ 5.85 Hz, a-H, Val), 4.21 (q, 1H,

J ¼ 5.45 Hz, a-H, Phe), 4.10 (q, 1H, J ¼ 9.0 Hz, a-H, His),

3.54 (s, 3H, OCH₃), 3.03e2.89 (m, 4H, b-H’s, Phe and His),

1.60e1.46 (m, 1H, b-H, Val), 0.97 (d, 6H, J ¼ 4.6 Hz,

g-H’s, Val); ¹³C NMR (300 MHz, CDCl₃): d 175.1 (C]O,

ester), 171.2, 169.6 (C]O, amide), 166.8 (C]O, AreCO),

1204, 870, 842, 826, 696 cm^ꢀ1

;

¹H NMR (300 MHz,

CDCl₃): d 8.90 (s, 1H, z-H, AreCO), 8.59 (d, 1H,

J ¼ 7.5 Hz, d-H, AreCO), 8.57 (br s, 1H, NH, amide), 8.42

(s, 1H, h-H, BzImz), 8.03 (d, 1H, J ¼ 7.8 Hz, 3-H, BzImz),

7.67 (d, 1H, J ¼ 7.65 Hz, d-H, BzImz), 7.05 (br s, 2H, NH,

BzImz and OH, AreCO), 7.00 (d, 1H, J ¼ 7.2 Hz, g-H, Are

CO), 4.92e3.85 (m, 1H, a-H, Ala), 4.09 (t, 1H, J ¼ 6.85 Hz,

a-H, Pro), 3.59 (s, 3H, OCH₃), 3.43 (t, 2H, J ¼ 7.15 Hz, d-

H’s, Pro), 2.76e2.69 (m, 2H, b-H’s, Pro), 2.02e1.95 (m,

2H, g-H’s, Pro), 1.28 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala); ¹³C

NMR (300 MHz, CDCl₃): d 175.9 (C]O, ester), 172.0

(C]O, amide), 167.2 (C]O, AreCO), 157.3 (C₂, AreCO),

0

153.0 (C₂, BzImz), 146.1 (C₆, BzImz), 144.9 (C₃, BzImz),

0

139.3 (C₂, BzImz), 135.7 (C₄, AreCO), 127.1 (C₆, Are

0

156.8 (C₂, AreCO), 153.2 (C₂, BzImz), 145.2 (C₃, BzImz),

0

141.2 (C₆, BzImz), 139.8 (C₂, Imz), 139.2 (C₂, BzImz),

CO), 124.6 (C₁, AreCO), 121.4 (C₅, AreCO), 120.5 (C₄,

BzImz), 118.3 (C₅, BzImz), 118.7 (C₃, AreCO), 109.2 (C₇,

BzImz), 64.3 (a-C, Pro), 51.1 (OCH₃), 46.4 (a-C, Ala), 43.1

(d-C, Pro), 31.0 (g-C, Pro), 28.1, 17.8 (b-C’s, Pro and Ala).

135.9 (C₄, AreCO), 133.2 (g-C, Phe), 130.3 (o-C’s, Phe),

128.0 (m-C’s, Phe), 127.7 ( p-C, Phe), 126.8 (C₄, Imz), 125.8

(C₆, AreCO), 124.3 (C₁, AreCO), 122.0 (C₅, AreCO),

119.7 (C₄, BzImz), 118.5 (C₅, BzImz), 117.5 (C₃, AreCO),

113.4 (C₅, Imz), 108.6 (C₇, BzImz), 57.7 (a-C, Val), 53.0

(a-C, His), 50.8 (a-C, Phe), 49.6 (OCH₃), 38.5 (b-C, Phe),

28.5 (b-C, Val), 23.2 (b-C, His), 18.6 (g-C’s, Val).

6.1.4.5. Compound 7e. [a]_Dꢀ5.0^ꢂ(c 0.1, MeOH); IR (KBr): n

3492 (NeH str.), 3361 (OeH str, AreCO), 3059, 3045 (AreH

str.), 2998e2989 (CeH str., cyclic CH₂), 2827 (CeH str.,

OCH₃), 1751 (C]O str. ester), 1662, 1659 (C]O str. tert. am-

ide), 1569, 1428 (skeletal bands), 1540, 1350 (NO₂str.), 1272,

1202, 871, 828, 698 cm^ꢀ1

;

¹H NMR (300 MHz, CDCl₃):

6.1.4.7. Compound 7g. [a]_Dþ33.3^ꢂ(c 0.1, MeOH); IR (KBr):

n 3489, 3483, 3130 (NeH str.), 3359 (OeH str., AreCO),

3052, 3115 (AreH str.), 2998, 2992 (CeH str., cyclic CH₂),

2924, 2919, 2850 (CeH str. CH₂), 1747 (C]O str. ester),

d 8.90 (s, 1H, z-H, AreCO), 8.59 (d, 1H, J ¼ 7.15 Hz, d-H,

AreCO), 8.41 (s, 1H, h-H, BzImz), 8.03 (d, 1H,

J ¼ 7.75 Hz, 3-H, BzImz), 7.67 (d, 1H, J ¼ 7.65 Hz, d-H,

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

791

1662, 1640, 1636 (C]O str. amide), 1565, 1427, 1422

(skeletal bands), 1549 (NH def. amide), 1544, 1347 (NO₂

str.), 1390, 1365 (CeH def. isopropyl grp), 1266, 1201, 870,

AreCO), 114.0 (C₇, BzImz), 57.4 (a-C, Phe), 52.5 (OCH₃),

38.8 (b-C, Phe), 20.4, 18.8 (5,6-CH₃, BzImz); MS (m/z, %):

444 (2.1), 443 (M^þ, 8.2), 428 (11.5), 412 (18.8), 384 (10.2),

265 (100), 237 (14.8), 146 (33.5), 119 (11.5), 118 (12.8), 91

(17.3), 77 (4.5), 66 (9.5), 65 (19.9), 59 (16.4), 31 (14.1), 17

(8.8), 15 (6.2).

845, 839, 827, 696 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃):

;

d 8.96 (br s, 1H, NH, amide), 8.93 (s, 1H, z-H, AreCO),

8.60 (d, 1H, J ¼ 7.45 Hz, d-H, AreCO), 8.42 (s, 1H, h-H,

BzImz), 8.02 (d, 1H, J ¼ 7.75 Hz, 3-H, BzImz), 7.86 (br s,

1H, NH, amide), 7.69 (d, 1H, J ¼ 7.95 Hz, b-H, Imz), 7.66

(d, 1H, J ¼ 7.6 Hz, d-H, BzImz), 7.50 (s, 1H, d-H, Imz),

7.40 (br s, 3H, NH’s, BzImz, Imz and OH, AreCO), 7.02

(d, 1H, J ¼ 7.2 Hz, g-H, AreCO), 6.52 (br s, 1H, NH, amide),

4.84e4.78 (m, 1H, a-H, Leu), 4.70e4.63 (m, 1H, a-H, His),

4.03 (d, 2H, J ¼ 5.1 Hz, CH₂, Gly), 3.90 (t, 1H, J ¼ 6.8 Hz,

a-H, Pro), 3.64 (s, 3H, OCH₃), 3.33 (t, 2H, J ¼ 7.2 Hz,

d-H’s, Pro), 2.94 (d, 2H, J ¼ 5.85 Hz, b-H’s, His), 2.77e

2.72 (m, 2H, b-H’s, Pro), 1.97e1.86 (m, 2H, g-H’s, Pro),

1.73 (t, 2H, J ¼ 7.95 Hz, b-H’s, Leu), 1.51e1.40 (m, 1H,

g-H, Leu), 1.00 (d, 6H, J ¼ 6.15 Hz, d-H’s, Leu); ¹³C NMR

(300 MHz, CDCl₃): d 174.8, 171.6 (C]O, amide), 169.5

(C]O, ester), 168.7 (C]O, amide), 167.6 (C]O, AreCO),

6.1.4.9. Compound 8b. [a]_Dꢀ36.3^ꢂ(c 0.1, MeOH); IR (KBr):

n 3490, 3124, 3117 (NeH str.), 3359 (OeH str., AreCO),

3060, 3033 (AreH str.), 2962, 2925, 2919 (CeH str. CH₃

and CH₂), 2823 (CeH str., OCH₃), 1750 (C]O str. ester),

1640, 1637 (C]O str. amide), 1540, 1412 (skeletal bands),

1530 (NH def. amide), 1468, 1445, 1372, 1272, 1198, 1158,

1

875, 828, 695 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.92 (s,

1H, z-H, AreCO), 8.59 (d, 1H, J ¼ 7.5 Hz, d-H, AreCO),

7.98 (br s, 1H, NH, amide), 7.32 (s, 1H, d-H, BzImz), 7.30

(s, 1H, h-H, BzImz), 7.11 (br s, 1H, NH, amide), 7.01 (d,

1H, J ¼ 7.2 Hz, g-H, AreCO), 6.62 (br s, 5H, NH’s, BzImz,

guanidino grp and OH, ArCO), 4.63 (q, 1H, J ¼ 9.45 Hz,

a-H, Arg), 3.90 (q, 2H, J ¼ 7.0 Hz, d-H’s, Arg), 3.80e3.71

(m, 1H, a-H, Ala), 3.60 (s, 3H, OCH₃), 2.27 (s, 3H, 3-CH₃,

BzImz), 2.25 (s, 3H, z-CH₃, BzImz), 2.18e1.74 (m, 4H,

b- and g-H’s, Arg), 1.30 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala);

¹³C NMR (300 MHz, CDCl₃): d 175.7 (C]O, ester), 172.0

(C]O, amide), 170.9 (C]O, AreCO), 159.6 (C]NH),

0

156.2 (C₂, AreCO), 152.4 (C₂, BzImz), 144.8 (C₃, BzImz),

0

142.2 (C₆, BzImz), 139.8 (C₂, Imz), 138.2 (C₂, BzImz),

136.6 (C₄, AreCO), 128.4 (C₄, Imz), 124.6 (C₆, AreCO),

122.8 (C₁, AreCO), 120.3 (C₅, AreCO), 119.2 (C₅, BzImz),

118.5 (C₄, BzImz), 116.6 (C₃, AreCO), 115.8 (C₅, Imz),

107.2 (C₇, BzImz), 59.1 (a-C, His), 56.5 (a-C, Pro), 51.4

(OCH₃), 47.2 (d-C, Pro), 45.3 (a-C, Leu), 41.7 (CH₂, Gly),

38.4 (b-C, Leu), 27.5, 25.6 (b-C’s, Pro and His), 24.2, 22.8

(g-C’s, Pro and Leu), 20.9 (d-C’s, Leu); MS (m/z, %): 719

(1.2), 718 (2.5), 717 (M^þ, 7.3), 702 (11.8), 686 (19.6), 658

(13.7), 629 (16.7), 601 (19.5), 516 (37.2), 488 (14.9), 419

(100), 391 (17.9), 282 (48.9), 254 (15.8), 163 (14.1), 136

(10.5), 135 (26.2), 81 (14.7), 67 (9.2), 66 (14.2), 65 (14.9),

59 (19.2), 57 (29.5), 46 (9.9), 43 (11.7), 42 (29.2), 31

(10.5), 30 (16.6), 29 (11.5), 17 (2.8), 15 (1.1).

0

156.8 (C₂, AreCO), 153.0 (C₂, BzImz), 139.9 (C₂, BzImz),

0

137.1 (C₃, BzImz), 135.6 (C₄, AreCO), 133.8, 132.4 (C₅

and C₆, BzImz), 128.1 (C₄, BzImz), 125.3 (C₆, AreCO),

124.5 (C₁, AreCO), 122.0 (C₅, AreCO), 118.4 (C₃,

AreCO), 113.7 (C₇, BzImz), 52.7 (a-C, Arg), 51.0 (OCH₃),

47.6 (a-C, Ala), 38.5 (d-C, Arg), 27.8 (b-C, Arg), 24.4 (g-C,

Arg), 20.1, 19.1 (5,6-CH₃, BzImz), 17.8 (b-C, Ala).

6.1.4.10. Compound 8c. [a]_Dꢀ13.4^ꢂ(c 0.1, MeOH); IR

(KBr): n 3498, 3494, 3125 (NeH str.), 3362 (OeH str., Ar

eCO), 3062, 3035, 3022 (AreH str.), 2960, 2924, 2916 (Ce

H str. CH₃and CH₂), 1753 (C]O str. ester), 1642, 1635

(C]O str. amide), 1544, 1426, 1420 (skeletal bands), 1534

(NH def. amide), 1465, 1447, 1270, 1195, 879, 872, 869,

6.1.4.8. Compound 8a. [a]_Dꢀ44.0^ꢂ(c 0.1, MeOH); IR (KBr):

n 3492, 3120 (NeH str.), 3355 (OeH str., AreCO), 3066,

3042, 3030 (AreH str.), 2964, 2958, 2917 (CeH str. CH₃

and CH₂), 1748 (C]O str. ester), 1640 (C]O str. sec. amide),

1544, 1416 (skeletal bands), 1532 (NH def. amide), 1398,

1

824, 695 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.93 (s, 1H,

z-H, AreCO), 8.59 (d, 1H, J ¼ 7.6 Hz, d-H, AreCO), 7.98

(br s, 1H, NH, amide), 7.82 (br s, 4H, NH’s, BzImz, Imz’s

and OH, AreCO), 7.74 (d, 1H, J ¼ 7.95 Hz, b-H, Imz²),

7.65 (s, 1H, d-H, Imz¹), 7.60 (s, 1H, d-H, Imz²), 7.37 (d,

1H, J ¼ 8.0 Hz, b-H, Imz¹), 7.31 (s, 1H, d-H, BzImz), 7.30

(s, 1H, h-H, BzImz), 7.01 (d, 1H, J ¼ 7.15 Hz, g-H, Ar

eCO), 6.93 (br s, 1H, NH, amide), 5.01 (q, 1H, J ¼ 8.95 Hz,

a-H, His¹), 4.13 (q, 1H, J ¼ 9.0 Hz, a-H, His²), 3.55 (s, 3H,

OCH₃), 3.07e2.76 (m, 4H, b-H’s, His), 2.27 (s, 3H, 3-CH₃,

BzImz), 2.26 (s, 3H, z-CH₃, BzImz); ¹³C NMR (300 MHz,

CDCl₃): d 175.3 (C]O, amide), 170.2 (C]O, ester), 168.8

(C]O, AreCO), 158.2 (C₂, AreCO), 153.1 (C₂, BzImz),

1268, 1196, 879, 825, 752, 705, 696 cm^ꢀ1

;

¹H NMR

(300 MHz, CDCl₃): d 8.75 (s, 1H, z-H, AreCO), 8.60 (d,

1H, J ¼ 7.55 Hz, d-H, AreCO), 7.31 (s, 1H, d-H, BzImz),

7.30 (s, 1H, h-H, BzImz), 7.11 (t, 1H, J ¼ 6.15 Hz, p-H,

Phe), 7.01e6.96 (m, 3H, g-H, AreCO and m-H’s, Phe),

7.85 (dd, 2H, J ¼ 8.75, 4.1 Hz, o-H’s, Phe), 6.58 (br s, 2H,

NH, BzImz and OH, AreCO), 6.50 (br s, 1H, NH, amide),

4.66 (q, 1H, J ¼ 5.55 Hz, a-H, Phe), 3.56 (s, 3H, OCH₃),

2.97 (d, 2H, J ¼ 5.6 Hz, b-H’s, Phe), 2.27 (s, 3H, 3-CH₃,

BzImz), 2.26 (s, 3H, z-CH₃, BzImz); ¹³C NMR (300 MHz,

CDCl₃): d 172.8 (C]O, AreCO), 170.4 (C]O, ester),

157.6 (C₂, AreCO), 152.2 (C₂, BzImz), 140.3 (C₂, BzImz),

0

138.4 (C₁, Phe), 137.2 (C₃, BzImz), 135.8 (C₄, AreCO),

142.7 (C₂, Imz^1,2), 138.9, 136.2 (C_{2 ,3}, BzImz), 135.8 (C₄,

AreCO), 134.2, 132.8 (C_5,6, BzImz), 126.9, 125.6 (C₄,

Imz^1,2), 124.1 (C₄, BzImz), 122.9 (C₆, AreCO), 121.8 (C₅,

AreCO), 120.2 (C₁, AreCO), 118.4 (C₃, AreCO), 116.3,

114.6 (C₅, Imz^1,2), 111.8 (C₇, BzImz), 62.7, 52.8 (a-C,

0

134.1, 132.5 (C₅and C₆, BzImz), 128.9, 128.1, 126.8 (o-,

m- and p-C’s, Phe), 126.2 (C₄, BzImz), 124.9 (C₆, AreCO),

123.2 (C₁, AreCO), 120.7 (C₅, AreCO), 117.2 (C₃,

792

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

His^1,2), 49.1 (OCH₃), 25.8, 23.3 (b-C, His^1,2), 20.3, 18.7 (5,6-

CH₃, BzImz); MS (m/z, %): 572 (3.2), 571 (1.3), 570 (M^þ,

4.6), 555 (11.5), 539 (18.2), 511 (10.7), 402 (100), 374

(21.3), 265 (32.6), 237 (15.3), 146 (30.9), 119 (10.5), 118

(11.6), 81 (20.3), 67 (12.5), 66 (10.4), 65 (17.7), 59 (15.9),

31 (10.7), 17 (7.8), 15 (5.5).

0

Tyr), 152.7 (C₂, BzImz), 138.8, 137.0 (C_{2 ,3}, BzImz), 136.3

0

(C₂, Indole), 135.5 (C₄, AreCO), 133.7, 132.5 (C_5,6, BzImz),

0

129.8, 128.4 (o- and m-C’s, Tyr), 127.2 (C₃, Indole), 126.0

(C₄, BzImz), 124.8 (C₆, AreCO), 122.5 (C₂, Indole), 122.1

(C₅, AreCO), 121.5 (C₁, AreCO), 120.8, 119.0 (C_5,6, Indole),

118.4 (C₃, AreCO), 117.8 (C₄, Indole), 117.0 (g-C, Tyr),

113.9 (C₇, BzImz), 111.2 (C₇, Indole), 109.3 (C₃, Indole),

62.6 (a-C, Trp), 56.5 (a-C, Ala), 54.5 (a-C, Tyr), 52.6

(OCH₃), 37.9 (b-C, Tyr), 30.3 (b-C, Trp), 20.2, 19.0 (5,6-

CH₃, BzImz), 16.9 (b-C, Ala); MS (m/z, %): 717 (3.2), 716

(M^þ, 8.2), 701 (10.5), 685 (19.6), 657 (13.1), 522 (17.8),

494 (17.4), 451 (100), 423 (20.8), 265 (30.6), 237 (13.8),

146 (28.7), 130 (12.9), 119 (10.7), 118 (14.9), 116 (18.4),

107 (6.9), 93 (16.3), 66 (13.2), 65 (16.2), 59 (13.6), 31

(11.2), 17 (7.3), 15 (6.2).

6.1.4.11. Compound 8d. [a]_Dꢀ7.5^ꢂ(c 0.1, MeOH); IR (KBr):

n 3496, 3116 (NeH str.), 3358 (OeH str., AreCO), 3061,

3034 (AreH str.), 2963, 2925, 2919 (CeH str. CH₃and

CH₂), 1744 (C]O str. ester), 1640, 1632 (C]O str. amide),

1540, 1425, 1422 (skeletal bands), 1536, 1466, 1445, 1387,

1

1365, 1273, 1198, 875, 830, 697 cm^ꢀ1; H NMR (300 MHz,

CDCl₃): d 8.98 (s, 1H, z-H, AreCO), 8.60 (d, 1H,

J ¼ 7.6 Hz, d-H, AreCO), 7.60 (br s, 1H, NH, amide), 7.31

(s, 1H, d-H, BzImz), 7.29 (s, 1H, h-H, BzImz), 7.01 (d, 1H,

J ¼ 7.2 Hz, g-H, AreCO), 6.78 (br s, 1H, NH, amide), 6.58

(br s, 2H, NH, BzImz and OH, ArCO), 4.39 (q, 1H,

J ¼ 6.7 Hz, a-H, Leu), 3.83 (t, 1H, J ¼ 8.65 Hz, a-H, Ile),

3.51 (s, 3H, OCH₃), 2.26 (s, 3H, 3-CH₃, BzImz), 2.24

(s, 3H, z-CH₃, BzImz), 2.06e1.96 (m, 1H, b-H, Ile), 1.75

(t, 2H, J ¼ 7.95 Hz, b-H’s, Leu), 1.67e1.62 (m, 2H, g-H’s,

Ile), 1.51e1.46 (m, 1H, g-H, Leu), 0.99 (d, 6H, J ¼ 6.25 Hz,

d-H’s, Leu), 0.93 (t, 3H, J ¼ 7.75 Hz, d-H’s, Ile), 0.88 (d,

3H, J ¼ 5.9 Hz, g⁰-H’s, Ile); ¹³C NMR (300 MHz, CDCl₃):

d 174.9 (C]O, ester), 170.2 (C]O, amide), 168.7 (C]O,

AreCO), 156.2 (C₂, AreCO), 153.2 (C₂, BzImz), 140.3

6.1.4.13. Compound 8f. [a]_Dþ41.8^ꢂ(c 0.1, MeOH); IR

(KBr): n 3490, 3130, 3122 (NeH str.), 3362 (OeH str.

ArCO), 3062, 3032 (AreH str.), 2964, 2959, 2876 (CeH str.

CH₃), 1748 (C]O str. ester), 1642, 1631 (C]O str. amide),

1541, 1420 (skeletal bands), 1535, 1527 (NH def. amide),

1449, 1392, 1362, 1271, 1196, 878, 828, 699 cm^ꢀ^{1 1}H

;

NMR (300 MHz, CDCl₃): d 9.32 (br s, 1H, NH, amide),

8.92 (s, 1H, z-H, AreCO), 8.59 (d, 1H, J ¼ 7.55 Hz, d-H,

AreCO), 7.96 (br s, 1H, NH, amide), 7.31 (s, 1H, d-H,

BzImz), 7.30 (s, 1H, h-H, BzImz), 7.02 (d, 1H, J ¼ 7.25 Hz,

g-H, AreCO), 6.82 (br s, 1H, NH, amide), 6.57 (br s, 2H,

NH, BzImz and OH, AreCO), 4.53e4.44 (m, 1H, a-H,

Ala¹), 3.96 (t, 1H, J ¼ 5.85 Hz, a-H, Val), 3.60 (s, 3H,

OCH₃), 3.53e3.44 (m, 1H, a-H, Ala²), 2.27 (s, 3H, 3-CH₃,

BzImz), 2.26 (s, 3H, z-CH₃, BzImz), 1.58e1.45 (m, 1H, b-

H, Val), 1.29 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala²), 1.23 (d, 3H,

J ¼ 5.85 Hz, b-H’s, Ala¹), 0.97 (d, 6H, J ¼ 4.55 Hz, g-H’s,

Val); ¹³C NMR (300 MHz, CDCl₃): d 171.5, 169.1 (C]O,

amide), 170.2 (C]O, ester), 165.4 (C]O, AreCO), 156.1

0

(C₂, BzImz), 137.3 (C₃, BzImz), 135.5 (C₄, AreCO),

133.9, 132.6 (C₅and C₆, BzImz), 128.9 (C₄, BzImz), 124.6

(C₆, AreCO), 123.6 (C₁, AreCO), 121.8 (C₅, AreCO),

118.1 (C₃, AreCO), 114.0 (C₇, BzImz), 58.5 (a-C, Ile), 53.4

(OCH₃), 51.4 (a-C, Leu), 40.6 (b-C, Ile), 36.4 (b-C, Leu),

24.7 (g-C, Ile), 24.0 (g-C, Leu), 22.5 (d-C’s, Leu), 19.8,

19.0 (5,6-CH₃, BzImz), 15.2 (g⁰-C, Ile), 9.9 (d-C, Ile).

6.1.4.12. Compound 8e. [a]_Dþ10.2^ꢂ(c 0.1, MeOH); IR

(KBr): n 3497, 3493, 3121 (NeH str.), 3360, 3357 (OeH

str., AreCO and Tyr), 3067, 3034, 3020 (AreH str.), 2964,

2928, 2923 (CeH str. CH₃and CH₂), 1748 (C]O str. ester),

1640, 1633 (C]O str. amide), 1544, 1424, 1418 (skeletal

bands), 1532, 1528 (NH def. amide), 1466, 1449, 1269,

(C₂, AreCO), 152.2 (C₂, BzImz), 140.7, 137.1 (C_{2 ,3}, BzImz),

135.9 (C₄, AreCO), 134.1, 132.5 (C_5,6, BzImz), 129.2 (C₄,

BzImz), 125.5 (C₆, AreCO), 123.7 (C₁, AreCO), 122.0 (C₅,

AreCO), 119.4 (C₃, AreCO), 113.8 (C₇, BzImz), 58.5 (a-C,

Ala¹), 52.4 (a-C, Val), 50.1 (OCH₃), 47.5 (a-C, Ala²), 28.3

(b-C, Val), 20.2, 19.2 (5,6-CH₃, BzImz), 18.8 (b-C, Ala¹),

18.1 (g-C’s, Val), 17.5 (b-C, Ala²).

0

1

1198, 875, 824, 818, 738, 697 cm^ꢀ1; H NMR (300 MHz,

CDCl₃): d 8.94 (s, 1H, z-H, AreCO), 8.58 (d, 1H,

J ¼ 7.55 Hz, d-H, AreCO), 8.15 (br s, 1H, NH, amide), 7.98

(br s, 1H, NH, amide), 7.32 (s, 1H, d-H, BzImz), 7.30

(s, 1H, h-H, BzImz), 7.25 (d, 1H, J ¼ 7.8 Hz, b-H, Indole),

7.22e7.08 (m, 4H, deh-H’s, Indole), 7.03 (d, 1H,

J ¼ 7.2 Hz, g-H, AreCO), 6.99 (br s, 4H, NH’s, BzImz, Indole

and OH’s, AreCO, Tyr), 6.92e6.77 (m, 4H, o- and m-H’s,

Tyr), 6.80 (br s, 1H, NH, amide), 4.94 (q, 1H, J ¼ 6.15 Hz,

a-H, Trp), 4.32e4.27 (m, 1H, a-H, Ala), 3.93 (q, 1H,

J ¼ 7.95 Hz, a-H, Tyr), 3.55 (s, 3H, OCH₃), 3.21 (d, 2H,

J ¼ 5.65 Hz, b-H’s, Trp), 2.82 (d, 2H, J ¼ 5.5 Hz, b-H’s,

Tyr), 2.27 (s, 3H, 3-CH₃, BzImz), 2.25 (s, 3H, z-CH₃, BzImz),

1.49 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala); ¹³C NMR (300 MHz,

CDCl₃): d 175.3, 172.7 (C]O, amide), 169.9 (C]O, ester),

166.2 (C]O, AreCO), 157.4 (C₂, AreCO), 153.9 ( p-C,

6.1.4.14. Compound 8g. [a]_Dꢀ1.8^ꢂ(c 0.1, MeOH); IR (KBr):

n 3492, 3488, 3124 (NeH str.), 3359 (OeH str. ArCO), 3065,

3046, 3033 (AreH str.), 2958, 2925, 2850 (CeH str. CH₃and

CH₂), 2824 (CeH str., OCH₃), 1744 (C]O str. ester), 1630,

1628 (C]O str. amide), 1545, 1419 (skeletal bands), 1532

(NH def. amide), 1448, 1267, 1197, 878, 872, 824, 739,

1

695 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 9.49 (br s, 1H,

NH, amide), 8.96 (s, 1H, z-H, AreCO), 8.59 (d, 1H,

J ¼ 7.6 Hz, d-H, AreCO), 8.25 (br s, 1H, NH, amide), 8.10

(br s, 1H, NH, amide), 7.80 (br s, 4H, NH’s, BzImz, Indole,

Imz and OH, AreCO), 7.74 (d, 1H, J ¼ 7.95 Hz, b-H, Imz),

7.60 (s, 1H, d-H, Imz), 7.31 (s, 1H, d-H, BzImz), 7.28 (s,

1H, h-H, BzImz), 7.24 (d, 1H, J ¼ 7.8 Hz, b-H, Indole),

7.21e7.07 (m, 4H, deh-H’s, Indole), 7.01 (d, 1H,

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

793

0

J ¼ 7.2 Hz, g-H, AreCO), 6.32 (br s, 1H, NH, amide), 4.24 (q,

1H, J ¼ 6.1 Hz, a-H, Trp), 4.15 (q, 1H, J ¼ 9.0 Hz, a-H, His),

3.93 (d, 2H, J ¼ 5.1 Hz, CH₂, Gly¹), 3.82 (d, 2H, J ¼ 5.1 Hz,

CH₂, Gly²), 3.54 (s, 3H, OCH₃), 3.22 (d, 2H, J ¼ 5.65 Hz,

b-H’s, Trp), 3.07 (d, 2H, J ¼ 5.9 Hz, b-H’s, His), 2.26 (s,

3H, 3-CH₃, BzImz), 2.24 (s, 3H, z-CH₃, BzImz); ¹³C NMR

(300 MHz, CDCl₃): d 176.5 (C]O, ester), 174.3, 169.4,

167.1 (C]O, amide), 166.7 (C]O, AreCO), 156.7 (C₂,

AreCO), 153.2 (C₂, BzImz), 142.0 (C₂, Imz), 138.7, 137.0

(C₃, BzImz), 135.4 (C₄, AreCO), 133.8 (C₅, BzImz), 132.6

(C₆, BzImz), 131.4 (C₁, AreCO), 130.2 (m-C’s, AreCO),

128.1 (o-C’s, AreCO), 125.2 (C₄, BzImz), 115.9 (C₇, BzImz),

54.1 (a-C, Arg), 39.3 (d-C, Arg), 27.8 (b-C, Arg), 24.0 (g-C,

Arg), 19.2, 18.5 (5,6-CH₃, BzImz); MS (m/z, %): 467 (M^þ,

5.9), 450 (4.5), 422 (15.2), 249 (18.5), 221 (100), 146

(27.5), 119 (10.9), 118 (10.2), 60 (24.8), 51 (10.5), 45

(11.2), 39 (9.7), 30 (16.5), 15 (7.8).

6.1.5.2. Compound 5c_a. [a]_Dꢀ65.3^ꢂ(c 0.3, MeOH); IR

(KBr): n 3495, 3336, 3125 (NeH str.), 3295e2525 (OeH

str. COOH), 3067, 3037 (AreH str.), 2964, 2927, 2915 (Ce

H str. CH₃and CH₂), 1708 (C]O str. COOH), 1633, 1625

(C]O str. sec. amide), 1553, 1428 (skeletal bands), 1530

(NH def. amide), 1406 (CeOH def. COOH), 1389, 1368

0

(C_{2 ,3}, BzImz), 135.8 (C₂, Indole), 135.8 (C₄, AreCO),

0

133.8, 132.6 (C_5,6, BzImz), 127.0 (C₃, Indole), 126.8 (C₄,

0

Imz), 126.2 (C₄, BzImz), 124.7 (C₆, AreCO), 124.0 (C₁,

AreCO), 122.5 (C₂, Indole), 121.8 (C₅, AreCO), 120.2,

119.6, 118.6 (C_4e6, Indole), 118.0 (C₃, AreCO), 114.5 (C₅,

Imz), 113.8 (C₇, BzImz), 110.9 (C₇, Indole), 109.2 (C₃,

Indole), 56.9 (a-C, Trp), 51.6 (a-C, His), 50.3 (OCH₃), 46.3

(CH₂, Gly²), 41.0 (CH₂, Gly¹), 29.3 (b-C, Trp), 20.1 (b-C,

His), 19.9, 18.9 (5,6-CH₃, BzImz); MS (m/z, %): 735 (2.4),

734 (1.6), 733 (M^þ,6.7), 718 (10.2), 702 (18.6), 674 (12.3),

565 (17.3), 537 (16.7), 508 (100), 480 (22.4), 322 (15.8),

294 (20.4), 265 (35.2), 237 (15.6), 146 (25.9), 130 (13.4),

119 (11.3), 118 (14.4), 116 (18.9), 81 (16.1), 67 (10.7), 66

(14.8), 65 (18.1), 59 (11.6), 31 (10.7), 17 (6.8), 15 (5.1).

(CeH def. CH(CH₃)₂), 880, 833, 697 cm^ꢀ1

;

¹H NMR

(300 MHz, CDCl₃): d 10.3 (br s, 2H, NH, BzImz and OH,

COOH), 8.31e8.22 (m, 4H, o- and m-H’s, AreCO), 7.79 (br

s, 1H, NH, amide), 7.70 (br s, 1H, NH, amide), 7.31 (s, 1H,

d-H, BzImz), 7.29 (s, 1H, h-H, BzImz), 5.16 (q, 1H,

J ¼ 6.75 Hz, a-H, Leu), 4.17 (d, 2H, J ¼ 5.1 Hz, CH₂, Gly),

2.26 (s, 3H, 3-CH₃, BzImz), 2.25 (s, 3H, z-CH₃, BzImz),

1.81e1.40 (m, 3H, b- and g-H’s, Leu), 1.00 (d, 6H,

J ¼ 6.15 Hz, d-H’s, Leu); ¹³C NMR (300 MHz, CDCl₃):

d 178.2 (C]O, COOH), 170.6 (C]O, amide), 166.1

6.1.5. General methodfor the hydrolysisofamino acid/peptide

derivatives of 4-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-

benzoic acid (5)/4-(5,6-dimethyl-1H-benzo[d]imidazol-2-yl)-

3,5-diiodobenzoic acid (6)/2-hydroxy-5-(6-nitro-1H-benzo

[d]imidazol-2-yl)-benzoic acid (7)/5-(5,6-dimethyl-1H-benzo

[d]imidazol-2-yl)-2-hydroxybenzoic acid (8)

To a solution of the amino acid/peptide methyl esters

(0.01 mol) in THF:H₂O (1:1, 36 mL), LiOH (0.36 g) was

added at 0 ^ꢂC. The mixture was stirred at RT for 1 h and

then acidiﬁed to pH 3.5 with 1 N H₂SO₄. The aqueous layer

was extracted with Et₂O (3 ꢃ 25 mL). The combined organic

extracts were dried over anhydrous Na₂SO₄and concentrated

under reduced pressure. The crude products were crystallized

from methanol and ether to get hydrolyzed peptide derivatives

5b_aed_a, 6e_aeg_a, 7c_aee_aand 8e_aeg_a.

0

(C]O, AreCO), 152.8 (C₂, BzImz), 139.8, 137.6 (C_{2 ,3}

0

,

BzImz), 134.4 (C₄, AreCO), 133.6, 132.5 (C_5,6, BzImz),

131.7 (C₁, AreCO), 130.8, 127.1 (m- and o-C’s, AreCO),

125.2 (C₄, BzImz), 114.2 (C₇, BzImz), 55.6, 45.1 (a- and

b-C’s, Leu), 41.8 (CH₂, Gly), 24.7 (g-C, Leu), 21.7 (d-C’s,

Leu), 19.5, 18.8 (5,6-CH₃, BzImz).

6.1.5.3. Compound 5d_a. [a]_Dꢀ90.0^ꢂ(c 0.3, MeOH); IR

(KBr): n 3495, 3122 (NeH str.), 3375 (OeH str., Tyr),

3290e2495 (OeH str. COOH), 3048, 3033 (AreH str.),

2959, 2923 (CeH str. CH₃and CH₂), 1705 (C]O str.

COOH), 1636, 1622 (C]O str. amide), 1555, 1425, 1420

(skeletal bands), 1535, 1528 (NH def. amide), 1410, 880,

878, 835, 830, 694 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃):

;

d 9.37 (br s, 1H, NH, amide), 8.98 (br s, 4H, NH’s, Imz

and BzImz and OH’s, Tyr and COOH), 8.29e8.20 (m, 4H,

o- and m-H’s, AreCO), 7.66 (s, 1H, d-H, Imz), 7.38 (d, 1H,

J ¼ 7.95 Hz, b-H, Imz), 7.31 (s, 1H, d-H, BzImz), 7.30 (s,

1H, h-H, BzImz), 7.24 (br s, 1H, NH, amide), 7.18 (dd,

2H, J ¼ 8.5, 5.15 Hz, o-H’s, Tyr), 6.76 (dd, 2H, J ¼ 8.55,

4.9 Hz, m-H’s, Tyr), 5.78 (q, 1H, J ¼ 9.0 Hz, a-H, His),

4.18 (q, 1H, J ¼ 8.0 Hz, a-H, Tyr), 3.12e2.73 (m, 4H,

b-H’s, Tyr and His), 2.27 (s, 3H, 3-CH₃, BzImz), 2.26 (s,

3H, z-CH₃, BzImz); ¹³C NMR (300 MHz, CDCl₃): d 173.2

(C]O, COOH), 170.5 (C]O, amide), 167.8 (C]O,

AreCO), 154.7 (CeOH, Tyr), 152.4 (C₂, BzImz), 142.2

6.1.5.1. Compound 5b_a. [a]_Dꢀ20.2^ꢂ(c 0.3, MeOH); IR

(KBr): n 3495, 3338, 3125 (NeH str.), 3283e2490 (OeH

str. COOH), 3069, 3052 (AreH str.), 2960, 2928, 2916 (Ce

H str. CH₃and CH₂), 1710 (C]O str. COOH), 1635 (C]O

str. sec. amide), 1544, 1418 (skeletal bands), 1531 (NH def.

amide), 1411 (CeOH def. COOH), 1375 (NO₂str.), 1164

(CeN str. sec. amine), 876, 835, 695 cm^ꢀ1

;

¹H NMR

(300 MHz, CDCl₃): d 8.65 (br s, 1H, NH, amide), 8.41 (dd,

2H, J ¼ 9.0, 6.65 Hz, m-H’s, AreCO), 8.20 (br s, 5H, NH’s,

BzImz, guanidino grp and OH, COOH), 8.02 (dd, 2H,

J ¼ 8.9, 6.55 Hz, o-H’s, AreCO), 7.31 (s, 1H, d-H, BzImz),

7.30 (s, 1H, h-H, BzImz), 4.40 (q, 1H, J ¼ 9.35 Hz, a-H,

Arg), 3.84 (q, 2H, J ¼ 6.95 Hz, d-H’s, Arg), 2.27 (s, 3H, 3-

CH₃, BzImz), 2.25 (s, 3H, z-CH₃, BzImz), 2.04e1.59 (m,

4H, b- and g-H’s, Arg); ¹³C NMR (300 MHz, CDCl₃):

d 182.2 (C]O, COOH), 167.5 (C]O, AreCO), 159.8

0

(C₂, Imz), 138.5, 136.8 (C_{2 ,3}, BzImz), 135.1 (C₄, AreCO),

133.7, 132.2 (C_5,6, BzImz), 131.5 (m-C’s, AreCO), 130.1

(C₁, AreCO), 128.6, 128.5 (o- and m-C’s, Tyr), 126.2

(o-C’s, AreCO), 125.0, 123.6 (C₄, BzImz and Imz), 118.2

(g-C, Tyr), 115.3 (C₅, Imz), 112.8 (C₇, BzImz), 58.7, 52.9

(a-C’s, His and Tyr), 37.3 (b-C, Tyr), 20.2, 19.1 (5,6-CH₃,

0

(C]NH), 152.2 (C₂, BzImz), 139.6 (C₂, BzImz), 137.8

794

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

BzImz), 16.7 (b-C, His); MS (m/z, %): 566 (M^þ, 8.5), 549

(5.3), 521 (22.4), 415 (9.8), 386 (30.8), 358 (11.7), 249

(42.7), 221 (100), 146 (22.6), 119 (12.8), 118 (8.4), 107

(12.6), 93 (21.6), 81 (14.6), 67 (12.8), 51 (8.6), 45 (10.7),

39 (7.6), 30 (15.9), 15 (4.7).

AreCO), 52.4 (a-C, Ala), 48.8 (a-C, Tyr), 42.0 (CH₂,

Gly), 37.1 (b-C, Tyr), 20.1, 18.6 (5,6-CH₃, BzImz), 17.9

(b-C, Ala).

6.1.5.6. Compound 6g_a. [a]_Dꢀ37.0^ꢂ(c 0.3, MeOH); IR

(KBr): n 3477, 3120 (NeH str.), 3290e2515 (OeH str.

COOH), 3066, 3050 (AreH str.), 2998, 2995 (CeH str. cyclic

CH₂), 2962, 2925 (CeH str. CH₃and CH₂), 1712 (C]O str.

COOH), 1656, 1629 (C]O str. amide), 1558, 1425, 1420

(skeletal bands), 1460 (CeH def. CH₂), 1408, 1388, 1372,

6.1.5.4. Compound 6e_a. [a]_Dꢀ31.0^ꢂ(c 0.3, MeOH); IR

(KBr): n 3480, 3470 (NeH str.), 3285e2505 (OeH str.

COOH), 3069, 3052 (AreH str.), 2997, 2990 (CeH str. cyclic

CH₂), 2958, 2920 (CeH str. CH₃and CH₂), 1710 (C]O str.

COOH), 1652, 1626 (C]O str. amide), 1558, 1424, 1416

(skeletal bands), 1467 (CeH def. CH₂), 1405, 888, 875,

1

882, 872, 768, 708, 592 cm^ꢀ1; H NMR (300 MHz, CDCl₃):

d 9.72 (br s, 2H, NH, OH, BzImz and COOH), 9.35 (br s,

1H, NH, amide), 8.45 (ss, 2H, o-H’s, AreCO), 7.82 (br s,

1H, NH, amide), 7.28 (ss, 2H, d- and h-H, BzImz), 7.17 (tt,

2H, J ¼ 6.15, 4.35 Hz, m-H’s, Phe), 7.01 (t, 1H, J ¼ 6.15 Hz,

p-H, Phe), 6.84 (dd, 2H, J ¼ 8.8, 4.15 Hz, o-H’s, Phe), 4.90

(t, 1H, J ¼ 5.85 Hz, a-H, Val), 4.37 (q, 1H, J ¼ 5.5 Hz, a-H,

Phe), 3.78 (t, 1H, J ¼ 6.85 Hz, a-H, Pro), 3.14 (t, 2H,

J ¼ 7.2 Hz, d-H, Pro), 2.76 (d, 2H, J ¼ 5.6 Hz, b-H’s, Phe),

2.26 (ss, 6H, 3- and z-CH₃, BzImz), 2.08e1.95 (m, 4H,

b- and g-H’s, Pro), 1.57e1.44 (m, 1H, b-H, Val), 0.97 (d,

6H, J ¼ 4.6 Hz, g-H’s, Val); ¹³C NMR (300 MHz, CDCl₃):

d 178.2 (C]O, COOH), 168.5 (C]O, amide), 166.9

(C]O, tert. amide), 165.6 (C]O, AreCO), 156.9 (C₂,

BzImz), 144.6 (C₁, AreCO), 139.9 (g-C, Phe), 138.7 (m-

1

868, 597 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 9.50 (br s,

3H, NH’s, BzImz, Imz and OH, COOH), 8.89 (br s, 1H,

NH, amide), 8.45 (ss, 2H, o-H’s, AreCO), 7.69 (d, 1H,

J ¼ 7.95 Hz, b-H, Imz), 7.49 (s, 1H, d-H, Imz), 7.26 (ss, 2H,

d- and h-H, BzImz), 5.85 (q, 1H, J ¼ 8.95 Hz, a-H, His),

4.11 (t, 1H, J ¼ 6.85 Hz, a-H, Pro), 3.38 (t, 2H, J ¼ 7.2 Hz,

d-H’s, Pro), 2.94 (d, 2H, J ¼ 5.85 Hz, b-H’s, His), 2.27 (ss,

6H, 3- and z-CH₃, BzImz), 2.06e1.97 (m, 4H, b- and g-H’s,

Pro); ¹³C NMR (300 MHz, CDCl₃): d 177.2 (C]O, COOH),

168.2 (C]O, AreCO), 163.5 (C]O, amide), 155.2 (C₂,

0

BzImz), 142.6 (C₄, AreCO), 140.3 (C₂, Imz), 138.7 (C₂,

0

BzImz), 136.2 (o-C’s, AreCO), 135.1 (C₃, BzImz), 134.3

(C₁, AreCO), 133.7 (C₅, BzImz), 132.4 (C₆, BzImz), 128.3

(C₄, Imz), 122.6 (C₄, BzImz), 116.5 (C₅, Imz), 112.4 (C₇,

BzImz), 104.6 (m-C’s, AreCO), 60.4 (a-C, Pro), 57.3 (a-C,

His), 46.2 (d-C, Pro), 30.1 (b-C, Pro), 24.0 (g-C, Pro), 20.1,

19.5 (5,6-CH₃, BzImz), 16.8 (b-C, His); MS (m/z, %): 752

(M^þ, 2.8), 735 (8.7), 707 (16.2), 638 (24.5), 610 (11.6), 501

(100), 473 (19.6), 329 (14.2), 203 (8.2), 146 (25.7), 127

(10.3), 119 (11.5), 118 (12.2), 81 (9.4), 67 (8.8), 45 (10.5),

42 (9.2), 15 (4.6).

0

C’s, AreCO), 136.4 (C₂, BzImz), 137.0 (C₄, AreCO),

0

134.9 (C₃, BzImz), 133.7 (C₅, BzImz), 131.8 (C₆, BzImz),

130.1 (o-C’s, Phe), 128.2 (m-C’s, Phe), 126.4 ( p-C, Phe),

122.5 (C₄, BzImz), 114.4 (C₇, BzImz), 103.2 (o-C’s,

AreCO), 61.0 (a-C, Pro), 54.3 (a-C, Phe), 52.6 (a-C, Val),

45.5 (d-C, Pro), 37.9 (b-C, Phe), 30.0 (b-C, Val), 28.3, 23.4

(b- and g-C’s, Pro), 19.8, 18.9 (5,6-CH₃, BzImz), 17.9

(g-C’s, Val); MS (m/z, %): 861 (M^þ, 5.4), 844 (7.8), 816

(11.7), 747 (20.1), 719 (10.3), 648 (100), 620 (11.4), 501

(26.7), 473 (18.8), 329 (14.3), 203 (7.8), 146 (23.7), 127

(11.4), 119 (10.2), 118 (12.9), 91 (15.4), 77 (6.5), 65 (8.9),

45 (8.1), 43 (7.2), 29 (11.5), 15 (2.6).

6.1.5.5. Compound 6f_a. [a]_Dꢀ6.4^ꢂ(c 0.3, MeOH); IR (KBr):

n 3488, 3125 (NeH str.), 3369 (OeH str., Tyr), 3295e2520

(OeH str. COOH), 3068, 3044, 3030 (AreH str.), 2960,

2956, 2915 (CeH str. CH₃and CH₂), 1708 (C]O str.

COOH), 1636, 1624 (C]O str. amide), 1559, 1422, 1418

(skeletal bands), 1530, 1526 (NH def. amide), 1462 (CeH

6.1.5.7. Compound 7c_a. [a]_Dꢀ14.8^ꢂ(c 0.3, MeOH); IR

(KBr): n 3488, 3115 (NeH str.), 3359 (OeH str., Are

CO), 3295e2510 (OeH str. COOH), 3062, 3025 (AreH

str.), 2920, 2848 (CeH str. CH₂), 1715 (C]O str.

COOH), 1642, 1632 (C]O str. amide), 1587, 1430 (skeletal

bands), 1548, 1539, 1410, 1348, 1196, 871, 842, 827,

def. CH₂), 1403, 1269, 883, 870, 823, 692, 596 cm^ꢀ^{1 1}H

;

NMR (300 MHz, CDCl₃): d 9.98 (br s, 1H, NH, amide),

9.34 (br s, 1H, NH, amide), 8.82 (br s, 3H, NH, OH’s, BzImz

and Tyr, COOH), 8.46 (ss, 2H, o-H’s, AreCO), 7.67 (br s, 1H,

NH, amide), 7.27 (ss, 2H, d- and h-H, BzImz), 6.99 (dd, 2H,

J ¼ 8.65, 4.95 Hz, m-H’s, Tyr), 6.90 (dd, 2H, J ¼ 8.5, 5.2 Hz,

o-H’s, Tyr), 4.87 (q, 1H, J ¼ 8.0 Hz, a-H, Tyr), 4.80e4.72 (m,

1H, a-H, Ala), 4.18 (d, 2H, J ¼ 5.1 Hz, CH₂, Gly), 2.79 (d,

2H, J ¼ 5.5 Hz, b-H’s, Tyr), 2.26 (ss, 6H, 3- and z-CH₃,

BzImz), 1.25 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala); ¹³C NMR

(300 MHz, CDCl₃): d 177.2 (C]O, COOH), 168.3 (C]O,

amide), 167.2 (C]O, amide), 162.0 (C]O, AreCO), 155.9

(C₂, BzImz), 153.2 (CeOH, Tyr), 142.8 (C₁, AreCO),

1

697 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.96 (s, 1H, z-

H, AreCO), 8.59 (d, 1H, J ¼ 7.45 Hz, d-H, AreCO), 8.40

(s, 1H, h-H, BzImz), 8.25 (br s, 3H, NH, BzImz and

OH’s, AreCO, COOH), 8.13 (br s, 1H, NH, amide), 8.10

(br s, 1H, NH, amide), 8.03 (d, 1H, J ¼ 7.8 Hz, 3-H,

BzImz), 7.66 (d, 1H, J ¼ 7.6 Hz, d-H, BzImz), 7.01 (d,

1H, J ¼ 7.2 Hz, g-H, AreCO), 4.17 (d, 2H, J ¼ 5.1 Hz,

CH₂, Gly²), 3.89 (d, 2H, J ¼ 5.1 Hz, CH₂, Gly¹); ¹³C

NMR (300 MHz, CDCl₃): d 179.2 (C]O, COOH), 168.2

(C]O, amide), 166.7 (C]O, AreCO), 156.8 (C₂, Are

0

138.2 (m-C’s, AreCO), 137.8 (C₂, BzImz), 135.9 (C₄,

0

AreCO), 134.4 (C₃, BzImz), 133.8 (C₅, BzImz), 131.6 (C₆,

0

CO), 153.2 (C₂, BzImz), 143.1 (C₃, BzImz), 141.0 (C₆,

0

BzImz), 139.2 (C₂, BzImz), 135.6 (C₄, AreCO), 127.0

(C₆, AreCO), 123.9 (C₁, AreCO), 120.7 (C₅, AreCO),

BzImz), 129.5 (o-C’s, Tyr), 127.8 (g-C, Tyr), 125.1 (m-C’s,

Tyr), 121.7 (C₄, BzImz), 114.9 (C₇, BzImz), 104.4 (o-C’s,

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

795

119.2 (C₄, BzImz), 118.8 (C₅, BzImz), 116.2 (C₃, AreCO),

108.7 (C₇, BzImz), 40.7, 39.8 (CH₂, Gly¹and Gly²).

(12.9), 379 (100), 351 (14.8), 282 (49.7), 254 (16.8), 163

(16.5), 136 (11.5), 135 (26.9), 66 (10.6), 65 (15.8), 46

(10.3), 45 (11.8), 42 (18.1), 17 (1.8).

6.1.5.8. Compound 7d_a. [a]_Dꢀ69.1^ꢂ(c 0.3, MeOH); IR

(KBr): n 3494, 3130 (NeH str.), 3357 (OeH str., AreCO),

3290e2515 (OeH str. COOH), 3057, 3052 (AreH str.),

2995, 2989 (CeH str., cyclic CH₂), 2958, 2872 (CeH str.

CH₃), 1716 (C]O str. COOH), 1660, 1636 (C]O str. amide),

1568, 1426 (skeletal bands), 1544, 1495, 1414, 1347, 1201,

6.1.5.10. Compound 8e_a. [a]_Dꢀ54.9^ꢂ(c 0.3, MeOH); IR

(KBr): n 3495, 3492, 3124 (NeH str.), 3362, 3355 (OeH

str., AreCO and Tyr), 3282e2518 (OeH str. COOH), 3065,

3033, 3023 (AreH str.), 2965, 2926, 2922 (CeH str. CH₃

and CH₂), 1712 (C]O str. COOH), 1645, 1632 (C]O str.

amide), 1546, 1425, 1416 (skeletal bands), 1533, 1526 (NH

def. amide), 1465, 1446, 1407, 1196, 876, 822, 819, 739,

870, 843, 828, 697 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃):

;

d 9.30 (br s, 1H, NH, amide), 8.91 (s, 1H, z-H, AreCO),

8.70 (br s, 3H, NH, BzImz and OH’s, AreCO, COOH), 8.60

(d, 1H, J ¼ 7.2 Hz, d-H, AreCO), 8.42 (s, 1H, h-H, BzImz),

8.02 (d, 1H, J ¼ 7.75 Hz, 3-H, BzImz), 7.65 (d, 1H,

J ¼ 7.6 Hz, d-H, BzImz), 7.00 (d, 1H, J ¼ 7.15 Hz, g-H,

AreCO), 4.86e4.77 (m, 1H, a-H, Ala), 4.10 (t, 1H,

J ¼ 6.85 Hz, a-H, Pro), 3.50 (t, 2H, J ¼ 7.2 Hz, d-H’s, Pro),

2.69e2.64 (m, 2H, b-H’s, Pro), 2.04e1.93 (m, 2H, g-H’s,

Pro), 1.34 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala); ¹³C NMR

(300 MHz, CDCl₃): d 177.4 (C]O, COOH), 170.2 (C]O,

amide), 165.4 (C]O, AreCO), 156.9 (C₂, AreCO), 153.2

1

697 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.95 (s, 1H, z-H,

AreCO), 8.59 (d, 1H, J ¼ 7.55 Hz, d-H, AreCO), 8.14 (br

s, 1H, NH, amide), 8.03 (br s, 5H, NH’s, BzImz, Indole and

OH’s, AreCO, Tyr, COOH), 7.97 (br s, 1H, NH, amide),

7.53 (br s, 1H, NH, amide), 7.31 (s, 1H, d-H, BzImz), 7.30

(s, 1H, h-H, BzImz), 7.25 (d, 1H, J ¼ 7.8 Hz, b-H, Indole),

7.23e7.07 (m, 6H, deh-H’s, Indole and o-H’s, Tyr), 7.02

(d, 1H, J ¼ 7.25 Hz, g-H, AreCO), 6.76 (dd, 2H,

J ¼ 8.6 Hz, m-H’s, Tyr), 4.94 (q, 1H, J ¼ 6.15 Hz, a-H, Trp),

4.79e4.72 (m, 1H, a-H, Ala), 4.16 (q, 1H, J ¼ 8.0 Hz, a-H,

Tyr), 3.23e2.95 (m, 4H, b-H’s, Trp and Tyr), 2.27 (s, 3H,

3-CH₃, BzImz), 2.26 (s, 3H, z-CH₃, BzImz), 1.50 (d, 3H,

J ¼ 5.85 Hz, b-H’s, Ala); ¹³C NMR (300 MHz, CDCl₃):

d 173.4 (C]O, COOH), 172.0, 169.2 (C]O, amide), 167.8

(C]O, AreCO), 158.0 (C₂, AreCO), 154.6 ( p-C, Tyr),

0

(C₂, BzImz), 144.6 (C₃, BzImz), 141.1 (C₆, BzImz), 140.0

0

(C₂, BzImz), 135.8 (C₄, AreCO), 125.4 (C₆, AreCO),

123.9 (C₁, AreCO), 120.5 (C₅, AreCO), 119.6 (C₅, BzImz),

118.4 (C₄, BzImz), 116.2 (C₃, AreCO), 110.7 (C₇, BzImz),

62.4 (a-C, Pro), 45.2 (a-C, Ala), 42.5 (d-C, Pro), 30.4 (g-C,

Pro), 26.3, 17.6 (b-C’s, Pro and Ala); MS (m/z, %): 467

(M^þ, 5.9), 450 (9.4), 422 (16.6), 379 (100), 351 (19.6), 282

(44.8), 254 (19.3), 163 (15.2), 136 (11.8), 135 (25.3), 66

(9.9), 65 (16.5), 46 (11.6), 45 (10.4), 42 (19.5), 17 (2.1).

0

153.2 (C₂, BzImz), 139.7, 137.2 (C_{2 ,3}, BzImz), 136.0 (C₂,

0

Indole), 134.7 (C₄, AreCO), 133.9, 132.4 (C_5,6, BzImz),

0

129.5, 128.1 (o- and m-C’s, Tyr), 127.3 (C₃, Indole), 126.2

(C₄, BzImz), 124.6 (C₆, AreCO), 122.7 (C₂, Indole), 121.9

(C₅, AreCO), 121.2 (C₁, AreCO), 120.6, 119.2 (C_5,6, Indole),

118.6 (C₃, AreCO), 118.0 (C₄, Indole), 116.5 (g-C, Tyr),

114.1 (C₇, BzImz), 111.2 (C₇, Indole), 109.5 (C₃, Indole),

62.5 (a-C, Trp), 57.3 (a-C, Ala), 51.1 (a-C, Tyr), 36.3 (b-C,

Tyr), 30.5 (b-C, Trp), 20.4, 18.9 (5,6-CH₃, BzImz), 17.8

(b-C, Ala).

6.1.5.9. Compound 7e_a. [a]_Dꢀ50.0^ꢂ(c 0.3, MeOH); IR

(KBr): n 3489 (NeH str.), 3360 (OeH str., AreCO), 3294e

2512 (OeH str. COOH), 3055, 3042 (AreH str.), 2997e

2989 (CeH str., cyclic CH₂), 1709 (C]O str. COOH),

1660, 1654 (C]O str. tert. amide), 1565, 1432 (skeletal

bands), 1542, 1492, 1410, 1350, 1203, 869, 843, 826,

1

696 cm^ꢀ1; H NMR (300 MHz, CDCl₃): d 8.91 (s, 1H, z-H,

6.1.5.11. Compound 8f_a. [a]_Dꢀ1.7^ꢂ(c 0.3, MeOH); IR

(KBr): n 3495, 3136, 3120 (NeH str.), 3361 (OeH str.

ArCO), 3295e2510 (OeH str. COOH), 3058, 3030 (AreH

str.), 2962, 2958, 2877 (CeH str. CH₃), 1715 (C]O str.

COOH), 1645, 1629 (C]O str. amide), 1540, 1422 (skeletal

bands), 1536 (NH def. amide), 1452, 1406, 1390, 1361,

AreCO), 8.60 (d, 1H, J ¼ 7.5 Hz, d-H, AreCO), 8.42 (s,

1H, h-H, BzImz), 8.20 (br s, 3H, NH, BzImz and OH’s,

AreCO, COOH), 8.00 (d, 1H, J ¼ 7.75 Hz, 3-H, BzImz),

7.65 (d, 1H, J ¼ 7.6 Hz, d-H, BzImz), 6.99 (d, 1H,

J ¼ 7.2 Hz, g-H, AreCO), 4.40 (t, 1H, J ¼ 6.8 Hz, a-H,

Pro³), 4.20 (t, 1H, J ¼ 6.85 Hz, a-H, Pro¹), 4.04 (t, 1H,

J ¼ 6.85 Hz, a-H, Pro²), 3.77e3.63 (m, 4H, d-H’s, Pro^2,3),

3.43 (t, 2H, J ¼ 7.15 Hz, d-H’s, Pro¹), 2.78e2.71 (m, 4H,

b-H’s, Pro^1,2), 2.06e1.87 (m, 8H, b-H’s, Pro³and g-H’s,

Pro^1e3); ¹³C NMR (300 MHz, CDCl₃): d 178.7 (C]O,

COOH), 170.2 (C]O, AreCO), 166.8, 161.9 (C]O, tert.

1198, 880, 826, 694 cm^ꢀ^{1 1}H NMR (300 MHz, CDCl₃):

;

d 9.33 (br s, 1H, NH, amide), 8.91 (s, 1H, z-H, AreCO),

8.60 (d, 1H, J ¼ 7.55 Hz, d-H, AreCO), 8.38 (br s, 3H, NH,

BzImz and OH’s, ArCO, COOH), 8.32 (br s, 1H, NH, amide),

7.31 (s, 1H, d-H, BzImz), 7.29 (s, 1H, h-H, BzImz), 7.04 (d,

1H, J ¼ 7.2 Hz, g-H, AreCO), 7.01 (br s, 1H, NH, amide),

5.02 (t, 1H, J ¼ 5.8 Hz, a-H, Val), 4.47e4.40 (m, 1H, a-H,

Ala¹), 3.45e3.39 (m, 1H, a-H, Ala²), 2.27 (s, 3H, 3-CH₃,

BzImz), 2.24 (s, 3H, z-CH₃, BzImz), 1.58e1.53 (m, 1H,

b-H, Val), 1.49 (d, 3H, J ¼ 5.9 Hz, b-H’s, Ala¹), 1.35 (d,

3H, J ¼ 5.9 Hz, b-H’s, Ala²), 0.97 (d, 6H, J ¼ 4.6 Hz, g-H’s,

Val); ¹³C NMR (300 MHz, CDCl₃): d 178.3 (C]O, COOH),

168.7, 167.5 (C]O, amide), 164.6 (C]O, AreCO), 156.0

0

amide), 157.0 (C₂, AreCO), 153.0 (C₂, BzImz), 143.6 (C₃,

0

BzImz), 141.0 (C₆, BzImz), 139.6 (C₂, BzImz), 135.7 (C₄,

AreCO), 127.6 (C₆, AreCO), 124.0 (C₁, AreCO), 119.9

(C₅, AreCO), 119.2 (C₅, BzImz), 118.9 (C₄, BzImz), 116.7

(C₃, AreCO), 110.2 (C₇, BzImz), 59.2, 58.6, 56.0 (a-C’s,

Pro^1e3), 46.4, 44.2, 42.9 (d-C’s, Pro^1e3), 29.7, 29.2, 27.8

(b-C’s, Pro^1e3), 28.4, 24.0, 23.5 (g-C’s, Pro^1e3); MS (m/z,

%): 590 (M^þ, 6.8), 573 (9.3), 545 (15.8), 476 (48.7), 448

0

(C₂, AreCO), 153.2 (C₂, BzImz), 142.6, 140.1 (C_{3 ,2}, BzImz),

796

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

135.6 (C₄, AreCO), 133.8, 132.3 (C_5,6, BzImz), 127.9 (C₄,

BzImz), 125.5 (C₆, AreCO), 124.0 (C₁, AreCO), 121.8 (C₅,

AreCO), 118.5 (C₃, AreCO), 114.3 (C₇, BzImz), 58.9 (a-C,

Val), 55.0 (a-C, Ala¹), 47.8 (a-C, Ala²), 28.5 (b-C, Val),

20.0, 19.3 (5,6-CH₃, BzImz), 18.5 (g-C’s, Val), 18.2 (b-C,

Ala¹), 17.6 (b-C, Ala²); MS (m/z, %): 523 (M^þ,4.5), 506

(8.3), 478 (13.4), 435 (28.2), 407 (15.5), 336 (100), 308

(20.4), 265 (31.5), 237 (11.8), 146 (21.4), 119 (11.1), 118

(15.3), 66 (11.3), 65 (15.9), 45 (10.4), 43 (12.7), 29 (8.8),

17 (4.5), 15 (5.2).

compounds were dissolved separately to prepare a stock

solution of 1 mg mL^ꢀ1using DMF. Stock solution was asep-

tically transferred and suitably diluted with sterile broth

medium to have seven different concentrations of each test

compound ranging from 200 to 3.1 mg mL^ꢀ1in different test

tubes. All the tubes were inoculated with one loopful of one

of the test bacteria. The process was repeated with different

test bacteria and different samples. Tubes inoculated with bac-

terial cultures were incubated at 37 ^ꢂC for 18 h and the pres-

ence/absence of growth of the bacteria was observed. From

these results, MIC of each test compound was determined

against each test bacterium. A spore suspension in sterile dis-

tilled water was prepared from ﬁve-days-old culture of the test

bacteria growing on nutrient broth media. About 20 mL of the

growth medium was transferred into sterilized petri plates and

inoculated with 1.5 mL of the spore suspension (spore concen-

tration e 6 ꢃ 10⁴spores mL^ꢀ1). Filter paper disks of 6 mm

diameter and 2 mm thickness were sterilized by autoclaving

at 121 ^ꢂC (15 psig) for 15 min. Each petri plate was divided

into ﬁve equal portions along the diameter to place one disc.

Three discs of test sample were placed on three portions

together with one disc with reference drug ciproﬂoxacin and

a disk impregnated with the solvent (DMF) as negative con-

trol. Test sample and reference drugs were tested at the con-

centration of 10 mg mL^ꢀ1. The petri plates inoculated with

bacterial cultures were incubated at 37 ^ꢂC for 18 h. Diameters

of the zones of inhibition (mm) were measured and the aver-

age diameters for test sample were calculated in triplicate

sets. The diameters obtained for the test sample were com-

pared with that produced by the standard drug ciproﬂoxacin.

The results of antibacterial studies are presented in Table 2.

6.1.5.12. Compound 8g_a. [a]_Dꢀ17.4^ꢂ(c 0.3, MeOH); IR

(KBr): n 3490, 3486, 3128 (NeH str.), 3352 (OeH str.

ArCO), 3290e2515 (OeH str. COOH), 3066, 3042, 3035

(AreH str.), 2960, 2926, 2852 (CeH str. CH₃and CH₂),

1716 (C]O str. COOH), 1633 (C]O str. amide), 1540,

1415 (skeletal bands), 1535 (NH def. amide), 1446, 1402,

1

1198, 877, 873, 825, 741, 690 cm^ꢀ1; H NMR (300 MHz,

CDCl₃): d 8.95 (s, 1H, z-H, AreCO), 8.65 (br s, 5H, NH’s,

BzImz, Indole, Imz and OH’s, AreCO, COOH), 8.58 (d,

1H, J ¼ 7.55 Hz, d-H, AreCO), 8.26 (br s, 1H, NH, amide),

8.14 (br s, 1H, NH, amide), 8.03 (d, 1H, J ¼ 7.95 Hz, b-H,

Imz), 7.75 (br s, 1H, NH, amide), 7.65 (s, 1H, d-H, Imz),

7.31 (s, 1H, d-H, BzImz), 7.30 (s, 1H, h-H, BzImz), 7.25 (d,

1H, J ¼ 7.85 Hz, b-H, Indole), 7.23e7.06 (m, 4H, deh-H’s,

Indole), 7.02 (d, 1H, J ¼ 7.2 Hz, g-H, AreCO), 6.57 (br s,

1H, NH, amide), 4.44 (q, 1H, J ¼ 6.1 Hz, a-H, Trp), 4.38 (q,

1H, J ¼ 8.95 Hz, a-H, His), 3.95 (d, 2H, J ¼ 5.15 Hz, CH₂,

Gly¹), 3.80 (d, 2H, J ¼ 5.15 Hz, CH₂, Gly²), 3.21e2.96 (m,

4H, b-H’s, Trp and His), 2.27 (s, 3H, 3-CH₃, BzImz), 2.26

(s, 3H, z-CH₃, BzImz); ¹³C NMR (300 MHz, CDCl₃):

d 176.5 (C]O, COOH), 174.6, 170.7, 167.5 (C]O, amide),

165.3 (C]O, AreCO), 158.4 (C₂, AreCO), 153.2 (C₂,

6.2.2. Antifungal studies

0

BzImz), 140.1 (C₂, Imz), 138.9, 137.2 (C_{2 ,3}, BzImz), 136.1

Serial plate dilution method was used in the present study

for the evaluation of antifungal activity against diamorphic

fungal strain C. albicans and three other fungal strains, includ-

ing A. niger and two cutaneous fungal strains M. audouinii and

T. mentagrophytes. MIC values of test compounds were deter-

mined by employing the same technique as used for antibacte-

rial studies using DMSO instead of DMF and tubes inoculated

with fungal cultures were incubated at 37 ^ꢂC for 48 h. After

incubation, the presence/absence of growth of the fungi was

observed and MIC of test compounds was determined against

each test fungus. A spore suspension in normal saline was

prepared from culture of the test fungi on sabouraud’s broth

media. After transferring growth medium, petri plates were in-

oculated with spore suspension. After drying, wells were made

using an agar punch and test samples, reference drug and neg-

ative control (DMSO) were placed in labeled wells in each

Petri plate. Test samples and reference drug, griseofulvin,

were tested at 10 mg mL^ꢀ1concentration. The petri plates in-

oculated with fungal cultures were incubated at 37 ^ꢂC for

48 h. Antifungal activity was determined by measuring the di-

ameter of the inhibition zone for triplicate sets. Activity of

each compound was compared with griseofulvin as standard

drug. The results of antifungal studies are given in Table 2

along with the results of antibacterial studies.

0

(C₂, Indole), 135.6 (C₄, AreCO), 133.9, 132.5 (C_5,6, BzImz),

0

129.3 (C₄, Imz), 127.2 (C₃, Indole), 126.1 (C₄, BzImz), 124.9

(C₆, AreCO), 124.0 (C₁, AreCO), 122.3 (C₂, Indole), 121.5

(C₅, AreCO), 120.2, 119.5, 118.4 (C_4e6, Indole), 117.5 (C₃,

AreCO), 116.1 (C₅, Imz), 114.0 (C₇, BzImz), 111.2 (C₇,

Indole), 109.5 (C₃, Indole), 56.5 (a-C, Trp), 51.1 (a-C, His),

46.5 (CH₂, Gly²), 41.3 (CH₂, Gly¹), 30.2 (b-C, Trp), 20.4

(b-C, His), 19.5, 18.7 (5,6-CH₃, BzImz); MS (m/z, %): 719

(M^þ,6.7), 702 (9.3), 674 (14.7), 565 (100), 537 (14.3), 508

(27.4), 480 (20.3), 322 (14.4), 294 (20.2), 265 (31.5), 237

(14.8), 146 (23.6), 130 (12.8), 119 (11.8), 118 (14.1), 116

(18.3), 81 (17.5), 67 (10.3), 66 (14.2), 65 (18.5), 45 (9.8),

30 (7.9), 17 (6.1), 15 (5.3).

6.2. Biological experimental section

6.2.1. Antibacterial studies

The synthesized peptide derivatives were screened for their

antibacterial activity against two gram positive bacterial

strains B. subtilis, S. aureus and two gram negative bacterial

strains P. aeruginosa, E. coli by using modiﬁed KirbyeBauer

disc diffusion method. MIC values of test compounds were

determined by tube dilution technique. All the synthesized

R. Dahiya, D. Pathak / European Journal of Medicinal Chemistry 42 (2007) 772e798

797

6.2.3. Anthelmintic studies

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ruses and Eudrilus sp. by Garg and Atal method at 2 mg mL^ꢀ1

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rating synthesized compounds (100 mg) with Tween 80 (0.5%)

and distilled water and the resulting mixtures were stirred

using a mechanical stirrer for 30 min. The suspensions were

diluted to contain 0.2% w/v of the test samples. Suspension

of reference drug, mebendazole, was prepared with the same

concentration in a similar way. Three sets of ﬁve earthworms

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test sample and reference drug at RT. Another set of ﬁve earth-

worms was kept as control in 50 mL suspension of distilled

water and Tween 80 (0.5%). The paralyzing and death times

were noted and their mean was calculated for triplicate sets.

The death time was ascertained by placing the earthworms

in warm water (50 ^ꢂC) which stimulated the movement, if

the worm was alive. The results of anthelmintic studies are

tabulated in Table 3.

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Article Doi

Synthetic studies on novel benzimidazolopeptides with antimicrobial, cytotoxic and anthelmintic potential

DOI: 10.1016/j.ejmech.2006.11.015

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