Synthesis of antimicrobial N-phthaloyl-alanyl-derived amidophosphates and triazoles

Article abstract of DOI:10.1515/znb-2009-0911

N-Phthaloyl-alanylazide reacts smoothly with trialkyl phosphites producing the corresponding α- aminophosphates. With dialkyl hydrogenphosphonates in the presence of benzoyl peroxide, amidophosphates were the isolated products whereas the oxoaziridin-1-yl

Full text of DOI:10.1515/znb-2009-0911

Synthesis of Antimicrobial N-Phthaloyl-alanyl-derived Amidophosphates
and Triazoles
Wafaa M. Abdou, Neven A. Ganoub, and Eman Sabry
Chemical Industries Division, National Research Centre, Elbohouth St. D-12622, Dokki, Cairo,
Egypt
Reprint requests to Professor Wafaa M. Abdou. E-mail: wabdou@intouch.com
Z. Naturforsch. 2009, 64b, 1057 – 1064; received February 28, 2009 / revised April 18, 2009
Dedicated to Professor Richard Neidlein on the occasion of his 77th birthday
N-Phthaloyl-alanylazide reacts smoothly with trialkyl phosphites producing the corresponding α-
aminophosphates. With dialkyl hydrogenphosphonates in the presence of benzoyl peroxide, ami-
dophosphates were the isolated products whereas the oxoaziridin-1-yl-phosphonic diamide was pref-
erentially provided from the reaction of the azide with tris(dimethylamino)phosphine. The azide was
also allowed to react with α-keto-, α-ethoxycarbonyl- and α-cyanomethylenetriphenylphosphorane
to give the corresponding linear disubstituted 1,2,3-triazoles. Screening results of antibiotic potency
for the products were discussed in terms of structure-activity relationship (SAR), and an attempt was
made to define the structural features for lead compounds.
Key words: α-Aminophosphates, Amidophosphates, Disubstituted 1,2,3-Triazoles,
N-Phthaloyl-alanylazide
Introduction
Results and Discussion
Reaction of N-phthaloyl-alanylazide (1) with trialkyl
phosphites 2a – c
Phthalimides constitute a class of compounds which
has attracted considerable attention in heterocyclic
chemistry [1, 2]. In effect, phthalimide derivatives have
In the presence of an excess of trimethyl phosphite
demonstrated significant and potential biological ac- (2a), the reaction with azide 1 led to the formation of
tivities in agricultural [3, 4] and in medicinal chem- the substituted imidoylphosphate 6a in 72 % yield. Ob-
istry [5, 6]. With the aim to develop expanded appli- viously, the mechanism of condensation of the azide
cations of phthalimides, very recently [7] we elabo- 1 with 2a involved the formation of the Staudinger
rated an efficient one-pot procedure for the synthe- phosphoranimine intermediate 4a that arose from the
sis of α- and β-phosphono-substituted phthalimides denitrogenation of the initially formed triazenylidene
with antibiotic activity. The method was based on the phosphorane 3a [8, 9]. Subsequent ring closure fol-
reaction of phosphorus(III) reagents with 2-methoxy- lowed by ring opening [10], and rearrangement (tau-
and 2-anilino-isoindole-1,3 (2H)-dione. In our contin- tomeric conversion) [8] through alkyl group shift led
uing development of phosphono-substituted phthalim- to the phosphate product 6a (Scheme 1). The com-
ides for application purposes, we now apply trivalent position and the structure of 6a – c are based on the
and pentavalent phosphorus reagents to 2-(1,3-dioxo- recorded elemental analyses, molecular weight deter-
1,3-dihydro-2H-isoindol-2-yl)propionylazide (1, also minations (MS), and spectroscopic data [11, 12]. Com-
known as N-phthaloyl-alanylazide). Trialkyl phos- pound 6a showed a 31P NMR chemical shift around
phites 2a – c, dialkyl hydrogenphosphonates 12a – c δ = 3.8 ppm, which indicates the presence of a P–O
and tris(dimethylamino)phosphine (16) were the ap- linkage in the molecule, and readily eliminates a struc-
plied phosphorus(III) reagents whereas triphenylalkyl- ture like 7 for which a signal at δ ≈ 11 – 16 ppm for
idenephosphoranes 18 and 20a, b were the phospho- P=N (or P–N) would be expected. The IR spectrum
rus(V) reagents. The reactions studied and the products of 6a revealed the absence of the stretching vibration
obtained are depicted in Schemes 1 – 6.
bands at 1708 and 2200 cm−1 related to the carbonyl
c
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W. M. Abdou et al. · Antimicrobial N-Phthaloyl-alanyl-derived Amidophosphates and Triazoles
Scheme 1.
OP
C
CH3
CH
1
P(O Pr)
i
N
6c
+
5c
N
F
3
2c
9
HOH
O
OH
P(O Pr)
CH3O P(O Pr)
i
2
CH3
CH
O
C
i
3
−
PrOH
i
NH
F
N
C
C
NH2
N
F
11
10
Scheme 2.
and the azido group, respectively, present in the IR carbonate, gave the expected N,N-dialkylated product
spectrum of the azide 1, and showed strong absorption 8 in 80 % yield.
bands at 1580 assigned to the imide (C=N) stretch-
In a similar way, the reaction product of 1 with tri-
ethyl phosphite (2b) was assigned the analogous struc-
ture 6b (74 % yield). Conversely, treatment of 1 with
triisopropyl phosphite (2c) afforded a mixture of the
expected analog 6c together with the vinyl phosphate
11 (Scheme 2). This behavior is not unexpected since
the bulky isopropyl group would impede the Arbusov
reaction. It appears that a partial hydrolysis at the stage
of the dipolar intermediate 9 has occurred to give the
final product 6c along with 11 via the intermediate 10.
It is known that lengthening or branching the alkyl rad-
ing, and at 1778 and 1728 cm−1 assigned to a cou-
1
pled C=O vibration of cyclic imides. In the H NMR
spectrum (CDCl3) of 6a the exocyclic methine pro-
ton, present in the spectrum of 1 at δ = 4.78 ppm (q),
was displayed at δ = 5.17 (dq) ppm. The deshield-
ing is clearly due to the phosphorus entity. Although
the physical and spectroscopic data indicated that 6
existed in the imino form, the stable amino structure
6A clearly could not be overlooked. Treatment of 6a
with methyl iodide in acetone, containing potassium
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W. M. Abdou et al. · Antimicrobial N-Phthaloyl-alanyl-derived Amidophosphates and Triazoles
1059
CH3
O
C
F N CH
N3
(Me2N)3P
+
1
16
CH
3O
N
CH
F
C
N
N
N
P(NMe2)3
O
O
17
F
=
Scheme 3.
Scheme 4.
icals in trialkyl phosphites results in reduction of their
migration aptitude [13].
O
CH3
CH
O
C
Ph3P CHCOPh
+
N
N3
Reactions of 1 with dialkyl hydrogenphosphonates
12a – c
1
O
18
CH3
O
C
The behavior of 1 toward 12a – c was studied next,
and the products obtained were those depicted in
Scheme 3. However, the reaction between 1 and 12
proceeded only when a catalytic amount of benzoyl
peroxide (13) was present in the medium [15, 16] to
yield the respective amido-phosphates 14a – c along
with the known [14] phthaloyl-DL-α-alanylamide (15)
(Scheme 3). The reaction products 14a – c were ob-
tained as colorless crystals in ∼ 62 % yield. Satisfac-
tory elemental analyses and molecular weight deter-
minations (MS) confirmed structure 14. 31P NMR sig-
nals of 14a – c were found at δ = ∼ 14 ppm [17]. The
1H NMR spectrum (CDCl3) of 14b showed among
others the NH proton at δ = 6.32 ppm.
Ph
CH3Cl /
C
H
F N
N
−
Ph3PO
N
N
19
Scheme 5.
Reaction of 1 with Tris(dimethylamino)phosphine (16)
Scheme 6.
Addition of an excess of tris(dimethylamino)phos-
phine (16) in dry tetrahydrofuran to the carbonyl azide
1 in dry THF at 20 ◦C led to the precipitation of the tri-
azenylidene-phosphorane17 (88% yield). A 31P NMR
signal was observed at δ = 40.3 ppm. Correct elemen-
tal analysis and expected 1H, 13C NMR data also con-
firmed the assigned structure (Scheme 4).
form for 36 h to furnish the 1,5-disubstituted 1,2,3-
triazole 19 in moderate 42 % yield via 1,3-cycloaddi-
tion [18– 20]. Triphenylphosphine oxide was also iso-
lated from the reaction medium. However, when the
reaction was carried out in dimethylformamide (DMF)
solution, and the mixture was heated in a microwave
oven for 20 min, product 19 was obtained in 90 %
yield (Scheme 5). The triazole structure 19 was de-
duced from analytical and spectroscopic data.
Reactions of N-phthaloyl-alanylazide (1) with alkyl-
idenephosphoranes
The reaction of α-ethoxycarbonyl- (20a) and α-
The present study was extended to investigate cyanomethylenetriphenylphosphorane (20b), however,
the application of P(V) reagents namely, alkylidene- did not proceed in this way, but gave the triazoles 22a
phosphoranes, to the azide 1, in order to prepare as yet or 22b in quantitative yields (Scheme 6). Conceiv-
unknown 1-(N-phthaloyl-alanyl)-1,2,3-triazoles.Thus, ably an addition of the ylides 20a, 20b to the termi-
the reaction of 1 with benzoylmethylenetriphenyl- nal nitrogen of the azide takes place (Staudinger reac-
phosphorane (18) was carried out in boiling chloro- tion), followed by an aza-Wittig reaction to give the
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W. M. Abdou et al. · Antimicrobial N-Phthaloyl-alanyl-derived Amidophosphates and Triazoles
Table 1. Antibacterial activity data of 6a – c, 14a, b, 19 and Table 2. Antifungal activity data of compounds 6a – c, 14a,
22a, b.
b, 19 and 22a, b.
Compound S. aureus
E. coli
P. aeruginosa K. pneumoniae
Comp.
A. niger
C. albicans A. fumigatus P. marneffei
6a
22a (5.85)b 27 (5.85) 20 (5.85)
23 (5.85)
21 (5.85)
–
6a
25a (5.85)b 23 (5.85)
22 (5.85)
25 (6.25)
23 (8.8)
25 (5.85)
26 (5.85)
–
22 (5.85)
25
19 (8.8)
22 (5.85)
28 (5.85)
–
6b
18 (5.85)
–
27 (5.85) 23 (5.85)
15 (12.5) 20 (12.5)
25 (5.85) 20 (5.85)
26 (5.85) 24 (5.85)
6b
22 (8.4)
20 (5.85)
27 (5.85)
28 (5.85)
18 (12.5)
9 (22)
21 (6.25)
21 (6.25)
23 (5.85)
25 (5.85)
12 (25)
6c
6c
14a
14b
19
21 (5.85)
22 (5.85)
19 (8.25)
12 (12.5)
14 (12.5)
25 (5.85)
22 (5.85)
9 (25)
14a
14b
19
18 (25)
13 (25)
22a
22b
15 (12.5) 12 (25)
14 (12.5) 12 (12.5)
28 (5.85) 24 (5.85)
19 (8.5)
13 (12)
25 (5.85)
22a
22b
14 (13)
–
–
10 (22)
18 (8.8)
21 (5.85)
20 (5.85)
10 (12.5)
22 (5.85)
Standardc 22 (5.85)
Standardc 25 (5.85)
23 (5.85)
a Indicates the diameter of zone of inhibition; b minimum inhibitory
concentration values (MIC, µg mL−1), c Amoxicillin is used as stan-
dard.
Indicates the diameter of zone of inhibition; minimum inhibitory
concentration values (MIC, µg mL−1); c Fluconazole is used as stan-
dard.
a
b
4,5-disubstituded triazoles 22a, b via the intermediates and linear disubstituted vic-triazoles that may comple-
21a, b, and extrusion of TPPO. ment those existing in the literature. This sequence in-
Formulas 22a and 22b are consistent with analytical cluded a number of α-amino-phosphate, amidophos-
and spectroscopic data. It is noteworthy that the posi- phate and triazenylphosphine derivatives from the re-
tion of the N-H hydrogen atom in the N-unsubstituted actions of the carbonyl azide 1 with different types of
triazoles such as structure 22 has been the subject of a P(III) reagents. In the second part, disubstituted tria-
contradictory discussion [21] (Scheme 6).
zole derivatives were obtained from the reactions of
1 with phosphorus ylides. The latter reactions fit into
the general class of concerted 1,3-dipolar reactions of
azides to dipolarophiles [18– 20]. Furthermore, the an-
timicrobial screening studies revealed that compounds
with a phosphorus moiety (phosphate, phosphazane,
or phosphoryl diamide) showed excellent activity. Fi-
nally, the results of the present investigation reflect the
versatility of the phosphorus reagents and of the azido
group as well.
Pharmacological screening
Antibacterial activity
A selection of the newly prepared compounds were
screened for their antibacterial activity against Es-
cherichia coli, Staphylococus aureus, Pseudomonas
aeruginosa, and Klebsiella pneumoniae (recultured)
bacterial strains by the disc diffusion method [22, 23].
The antibacterial screening data shown in Table 1 indi-
cate that compounds 6a, 6b, 14a, and 14b exhibit good
antibacterial activity against all tested bacterial strains
almost equivalent to that of the standard drug Amoxi-
cilline.
Experimental Section
General remarks
Melting points were measured on an Electrothermal melt-
ing point apparatus. The IR spectra were recorded on a
Antifungal activity
Perkin Elmer 317 Grating IR spectrophotometer, using KBr
Selected compounds were screened for their anti- pellets. The H and 13C NMR spectra were measured on a
1
Jeol E.C.A. 500 MHz instrument using SiMe4 as internal
standard. The 31P NMR spectra were recorded with the same
instrument, relative to external H3PO4 (85 %). The mass
spectra were performed on a Jeol JMS-A X 500 spectrom-
eter. Elemental analyses were carried out at the Microanaly-
sis Laboratory, Cairo University, Cairo, Egypt. All reactions
were performed under argon. The appropriate precautions
in handling moisture-sensitive compounds were considered.
Solvents were dried by standard techniques. TLC: Merck
0.2 mm silica gel 60 F154 aluminum plates. Column chro-
matography (CC): silica gel (silica gel 60 mesh, particle size
0.2 – 0.5 mm; E. Merck, Darmstadt). The substrate 2-(1,3-
dioxo-1,3-dihydro-2H-isoindol-2-yl)propionyl-azide (1) was
fungal activity against Aspergillus niger, Candida al-
bicans, Aspergillus fumigatus, and Pencillium marnef-
fei (recultured) by the agar diffusion method [23]. The
diameter of zone of inhibition and minimum inhibitory
concentration values are given in Table 2. The results
revealed that compounds 6a, 14a and 14b show signifi-
cant antifungal activity. Other tested compounds, how-
ever, showed moderate activity as compared to that of
the standard drug Fluconazole.
Summary and Conclusion
To summarize, we have reported an efficient access
to a series of phthalimidoyl-phosphorus derivatives prepared according to the reported method [24].
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General procedure for the reaction of 1 with trialkyl
phosphites 2a – c
(1Z)-2-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-iso-
propylpropanimidoyl diisopropyl phosphate (6c)
Yellow crystals. Yield: 400 mg, 36 %. M. p. 161 – 162 ◦C
(from MeCN). – IR (film): ν = 1774, 1724 (C(1,3)=O),
1575 (C=N), 1262 (P=◦O), 1088 (P-O-C) cm−1. – 1H NMR
(500 MHz, CDCl3, 25 C, TMS): δ = 0.96 (d, J = 7.2 Hz,
A
mixture of N-phthaloyl-alanylazide (1) (0.7 g,
2.87 mmol) and a trialkyl phosphite 2a – c (4 mL) was heated
at 100 ◦C, in absence of a solvent for ≈ 15 h (TLC). The ex-
cess of the phosphite was removed under vacuum, and then
the residue was washed several times with light petroleum
(40 – 60 ◦C), and crystallized from the proper solvent to give
compounds 6a, 6b or 6c and 11, respectively.
4
6 H, iso-(H3C)2-C-N), 1.28, 1.13 (2 × dd, J = 6.6 Hz, J=
5.7 Hz, 12 H, iso-(H3C)2-COP), 1.57 (d, J = 6.8 Hz, 3 H,
H3C-C), 3.87 (sept, J = 7.2 Hz, 1 H, HC-N), 4.12 (d sept,
3J = 13.2 Hz, 2 2 H, HCOP), 4.94 (dq, J = 6.6 Hz, 1 H,
HC-Me), 7.76, 7.88 (2 × d, J = 4.4 Hz, 4 H, H-Ar). –
13C NMR (500 MHz, CDCl3, TMS): δ = 15.8 (CH3C),
23.7 (CH3C-N), 24.5 (CH3COP), 42.6 (d, 3J = 14.8 Hz,
CH-Me), 43.5 (CHN), 72.3 (d, 2J = 26.8 Hz, CHOP), 124.2,
133.4, 135.7 (all C-Ph), 165.8 (C(1,3)=O), 170.4 (d, 2J =
16.8 Hz, C=N). – 31P NMR (500 MHz, CDCl3, H3PO4): δ
= 4.3 ppm. – MS (EI, 70 eV): m/z (%) = 425 (48) [M+1]+,
366 (13), 323 (10), 281 (34), 257 (100), 174 (28), 147
(33), 111 (24), 104 (14), 76 (15). – C20H29N2O6P (424.4):
calcd. C 56.6, H 6.8, N 6.6, P 7.3; found C 56.7, H 6.9,
N 6.5, P 7.2.
(1Z)-2-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-methyl-
propanimidoyl dimethyl phosphate (6a)
Straw-yellow prisms. Yield: 700 mg (72 %). M. p. 153 –
155 ◦C (from acetone/ether). – IR (film): ν = 1778,
1728 (C(1,3)=O), 1580 (C=N), 1256 (P=O), 1044 (P-O-
C) cm−1. – 1H NMR (500 MHz, CDCl3, 25 ◦C, TMS): δ =
1.55 (d, J = 6.8 Hz, 3 H, C-Me), 3.18 (s, 3 H, N-Me), 3.79 (d,
3J = 12.4 Hz, 6 H, POMe), 5.17 (m dq, 1 H, HCMe), 7.76,
7.88 (2×d, J = 4.4 Hz, 4 H, H-Ph). – 13C NMR (500 MHz,
CDCl3, TMS): δ = 14.6 (Me-C), 41.6 (d, 3J = 10.5 Hz,
2
CHMe), 42.4 (NMe), 54.3 (d, J = 12.8 Hz, MeOP), 124.3,
134.6, 135.3 (all C-Ph), 165.5 (C(1,3)=O), 174.6 (d, 2J =
18.4 Hz, C=N). – 31P NMR (500 MHz, CDCl3, H3PO4): δ =
3.8 ppm. – MS (EI, 70 eV): m/z (%) = 340 (22) [M]+, 325
(9), 310 (31), 295 (44), 280 (100), 185 (30), 171 (83), 146
(80), 110 (54), 104 (41), 77 (56). – C14H17N2O6P (340.3):
calcd. C 49.4, H 5.0, N 8.2, P 9.1; found C 49.5, H 4.9, N 8.1,
P 9.2.
(1E)-1-Amino-2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-
prop-1-en-1-yl diisopropyl phosphate (11)
Yellow crystals. Yield: 360 mg (33 %). M. p. 161 – 162 ◦C
(from MeCN). – IR (film): ν = 3355 – 3173 (NH2), 1782,
1730 (C(1,3)=O), 1613 (C=C), 1228 (P=O, bonded), 1080
(P-O-C) cm−1. – 1H NMR (500 MHz, CDCl3, 25 ◦C, TMS):
δ = 1.28, 1.34 (2 × dd, J = 6.6 Hz, 4J = 5.5 Hz, 12 H,
3
iso-(H3C)2-COP), 2.37 (s, 3 H, H3C-C), 4.42 (d-sept, J =
(1Z)-2-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)-N-ethyl-
propanimidoyl diethyl phosphate (6b)
12.9 Hz, 2 H, HCOP), 6.13, 6.34 (br 2s, 2 × 1H, H2N),
7.76, 7.88 (2 × d, J = 4.4 Hz, 4 H, H-Ar). – 13C NMR
(500 MHz, CDCl3, TMS): δ = 22.7 (CH3C=), 24.8 (iso-
Straw-yellow needles. Yield: 810 mg, 74 %. M. p. 135 –
137 ◦C (from CH2Cl2). – IR (film): ν = 1782, 1720
(C(1,3)=O), 1587 (C=N), 1265 (P=O), ◦1100 (P-O-C)
cm−1. – 1H NMR (500 MHz, CDCl3, 25 C, TMS): δ =
0.88 (t, J = 6.6 Hz, 3 H, H3C-CN), 1.22 (dt, J = 6.6 Hz,
4J = 4.8 Hz, 6 H, H3C-COP), 1.57 (d, J = 6.8 Hz, 3 H, H3C-
3
(CH3)2COP), 72.7 (d, 2J = 28.6 Hz, HCOP), 100.4 (d, J =
12.6 Hz, C(Me)=C), 125.6, 130.4, 133.2 (all C-Ar), 165.8
(C(1,3)=O), 182.4 (d, 2J = 28.6 Hz, =COP). – 31P NMR
(500 MHz, CDCl3, H3PO4): δ = 4.3 ppm. – MS (EI,
70 eV): m/z (%) = 381 (17) [M–1]+, 380 (20) [M–2]+,
366 (19), 323 (21), 281 (43), 257 (100), 174 (58), 147
(33), 111 (20), 104 (34), 76 (42). – C17H23N2O6P (382.4):
calcd. C 53.4, H 6.0, N 7.3, P 8.1; found C 53.5, H 6.1,
N 7.2, P 8.0.
3
C), 3.65 (q, J = 6.6 Hz, H2CN), 4.08 (dq, J = 6.6 Hz, J =
5.2 Hz, 4 H, H2COP), 5.17 (dq, J = 6.8 Hz, 4J = 4.2 Hz,
1 H, HCMe), 7.68, 7.78 (2 × d, J = 7.4 Hz, 4 H, H-Ar). –
13C NMR (500 MHz, CDCl3, TMS): δ = 15.5 (CH3CN),
15.8 (CH3CH), 16.3 (CH3COP), 38.4 (CH2N), 42.6 (d, 3J =
8.4 Hz, CH-Me), 64.7 (d, 2J = 16.8 Hz, CH2OP), 124.2,
133.4, 135.7 (all C-Ar), 166.5 (C(1,3)=O), 173.4 (d, 2J =
18.5 Hz, C=N). – 31P NMR (500 MHz, CDCl3, H3PO4):
Methylation of the phosphate 6a
A mixture of the phosphate 6a (0.5 g, 1.47 mmol), methyl
δ = −2.4 ppm. – MS (EI, 70 eV): m/z (%) = 382 (9) [M]+, iodide (3.0 mL), and anhyd. K2CO3 (2 g) in dry acetone
338 (18), 309 (31), 280 (100), 185 (16), 174 (96), 146 (90), (50 mL) was refluxed for 2 h and then filtered while hot. After
110 (52), 104 (28), 77 (54). – C17H23N2O6P (382.4): calcd. evaporation of the volatile materials in vacuum, the residue
C 53.4, H 6.0, N 7.3, P 8.1; found C 53.3, H 6.1, N 7.2, P 8.2. was triturated with light petroleum ether, and then allowed
Compounds 6c and 11 were fractionally crystallized from to cool in an ice-chest. The solid obtained was recrystallized
the reaction of 1 with 2c:
from aqueous ethanol to give 8.
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(1E)-1(Dimethylamino)-2-(1,3-dioxo-1,3-dihydro-2H-
Diethyl [2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-
isoindol-2-yl)prop-1-en-1-yl dimethyl phosphate (8)
propanoyl]amidophosphate (14b)
Colorless needles. Yield: 720 mg (62 %). M. p. 155 –
157 ◦C (from CH2Cl2). – IR (film): ν = 3280 (NH),
1780, 1730 (C(1,3)=O), 1700 (C=O, amide), 1224 (P=O,
bonded), 1077 (POC)◦, 970 (N-P) cm−1. – 1H NMR
(500 MHz, CDCl3, 25 C, TMS): δ = 1.22 (dt, J = 6.6 Hz,
4J = 4.8 Hz, 6 H, H3C-COP), 1.57 (d, J = 6.8 Hz, 3 H,
Colorless needles. Yield: 416 mg (80 %). M. p. 118 –
120 ◦C. – IR (film): ν = 1778, 1728 (C(1,3)=O), 1622
(C=C, exocyclic), 1268 (P=O), 1050 (P-O-C) cm−1. –
◦
1H NMR (500 MHz, CDCl3, 25 C, TMS): δ = 1.57 (s,
3 H, H3CC), 2.98, 3.01 (2 × s, 2 × 3 H, (H3C)2N), 3.85
(d, 3J = 12.5 Hz, 6 H, H3COP), 7.77, 7.90 (2 × d, J =
4.4 Hz, 4 H, H-Ar). – 13C NMR (500 MHz, CDCl3, TMS):
δ = 12.3 (CH3C), 41.6, 41.8 (N(CH3)2), 54.3 (d, 2J =
8.3 Hz, CH3OP), 93.8 (d, 3J = 10.3 Hz, C-Me), 124.3,
131.6, 133.3 (all C-Ar), 162.5 (C(1,3)=O), 166.2 (d, 2J =
28.3 Hz, =COP). – 31P NMR (500 MHz, CDCl3, H3PO4):
δ = 4.8 ppm. – MS (EI, 70 eV): m/z (%) = 354 (15) [M]+, 325
(21), 310 (23), 295 (46), 280 (100), 185 (29), 171 (81), 146
(82), 116 (54), 104 (40), 77 (52). – C15H19N2O6P (354.3):
calcd. C 50.8, H 5.4, N 7.9, P 8.7; found C 50.7, H 5.5,
N 7.8, P 8.8.
3
H3C-C), 4.08 (dq, J = 6.6 Hz, J = 5.2 Hz, 4 H, H2COP),
4
5.17 (dq, J = 6.8 Hz, J = 4.2 Hz, 1 H, HC-Me), 6.32 (br,
1 H, HN), 7.68, 7.78 (2 × d, J = 7.4 Hz, 4 H, H-Ar). –
13C NMR (500 MHz, CDCl3, TMS): δ = 15.6 (CH3COP),
17.8 (CH3C), 54.3 (CH-Me), 60.6 (d, 2J = 16.8 Hz, CH2OP),
123.8, 133.4, 134.7 (all C-Ar), 164.5 (d, 2J = 24.2 Hz, C=O,
amide), 166.7 (C(1,3)=O). – 31P NMR (500 MHz, CDCl3,
H3PO4): δ = 14.6 ppm. – MS (EI, 70 eV): m/z (%) = 353 (10)
[M–1]+, 339 (15), 311 (11), 202 (42), 174 (100), 146 (58),
110 (37), 104 (55), 77 (43). – C15H19N2O6P (354.3): calcd.
C 50.8, H 5.4, N 7.9, P 8.7; found C 50.7, H 5.5, N 7.8, P 8.8.
General procedure for the reaction of 1 with dialkyl hydro-
genphosphonates 12a – c
Diisopropyl [2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-
propanoyl]amidophosphate (14c)
Colorless crystals. Yield: 800 mg (64 %). M. p. 176 –
178 ◦C (from EtOH). – IR (film): ν = 3342 (NH), 1782, 1728
(C(1,3)=O), 1705 (C=O, amide), 1235 (P=O, bonded),
1105 (POC), 974 (N-P) cm−1. – 1H NMR (500 MHz, CDCl3,
25 ◦C, TMS): δ = 0.98, 1.14 (2 × dd, J = 6.6 Hz, 4J =
5.4 Hz, 12 H, iso-(H3C)2-COP), 1.57 (d, J = 6.8 Hz, 3 H,
H3C-C), 4.12 (d-sept, J = 6.6 Hz, 3J = 8.9 Hz, 2 H, HCOP),
4.94 (q, J = 6.6 Hz, 1 H, HC-Me), 6.24 (br, 1 H, HN),
7.67, 7.78 (2 × d, J = 4.4 Hz, 4 H, H-Ar). – 13C NMR
(500 MHz, CDCl3, TMS): δ = 12.8 (CH3COP), 17.8 (CH3-
C), 54.7 (CH-Me), 69.8 (d, 2J = 11.8 Hz, CHOP), 123.2,
A mixture of 1 (0.8 g, 3.28 mmol) and 6 mmol of dimethyl
(12a), diethyl (12b) or diisopropyl phosphonate (12c) was
refluxed in benzene (20 mL) containing a catalytic amount
of benzoyl peroxide (13) for ≈ 4 h (TLC). After cooling,
the colorless material that precipitated was collected, crys-
tallized, and identified as phthaloyl-DL-α-alanylamide (15,
12 %).◦M. p. 214 – 216 ◦C (from ethanol) (lit. [14]: 214 –
215.5 C). The filtrate was evaporated under reduced pres-
sure, and then the residue was crystallized from the proper
solvent to give the corresponding amidophosphates 14a, 14b
or 14c.
2
133.4, 135.7 (all C-Ar), 164.5 (d, J = 22.2, C=O, amide),
166.4 (C(1,3)=O ). – 31P NMR (500 MHz, CDCl3, H3PO4):
δ = 14.3 ppm. – MS (EI, 70 eV): m/z (%) = 381 (22) [M–
1]+, 367 (18), 334 (36), 306 (18), 263 (14), 202 (48), 174
(100), 146 (55), 110 (23), 104 (44), 77 (43). – C17H23N2O6P
(382.4): calcd. C 53.4, H 6.0, N 7.3, P 8.1; found C 53.3,
H 6.1, N 7.2, P 8.2.
Dimethyl [2-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)-
propanoyl]amidophosphate (14a)
Colorless crystals. Yield: 620 mg (58 %). M. p. 164 –
167 ◦C (from acetone). – IR (film): ν = 3320 (NH),
1777, 1732 (C(1,3)=O), 1708 (C=O, amide), 1232 (P=O,
bonded), 1048 (POC)◦, 978 (N-P) cm−1. – 1H NMR
(500 MHz, CDCl3, 25 C, TMS): δ = 1.55 (d, J = 6.8 Hz,
3 H, H3C-C), 3.79 (d, 3J = 12.4 Hz, 6 H, H3COP), 5.17 (q,
J = 6.8 Hz, 1 H, HCMe), 6.28 (br, 1 H, HN), 7.76, 7.88 (2×d,
J = 4.4 Hz, 4 H, H-Ar). – 13C NMR (500 MHz, CDCl3,
TMS): δ = 17.6 (CH3-C), 52.3 (d, 2J = 21.0 Hz, CH3OP),
54.3 (d, 3J = 12.3 Hz, CH-C), 123.7, 134.5, 135.3 (all C-Ar),
Reaction of 1 with tris(dimethylamino)phosphine (16)
Trisaminophosphine 16 (6 mL, 4.5 mmol) in super-dry
tetrahydrofuran (THF) (5 mL) was added dropwise to the
carbonyl azide 1 (0.5 g, 2.1 mmol) in THF (5 mL), and the
reaction mixture was stirred at r. t. for ≈ 10 h (TLC). After
cooling, the precipitated material was collected and dried to
give compound 17.
2
164.5 (d, J = 10.8 Hz, C=O, amide), 168.4 (C(1,3)=O). –
31P NMR (500 MHz, CDCl3, H3PO4): δ = 14.3 ppm. – MS
(EI, 70 eV): m/z (%) = 325 (18) [M–1]+, 311 (31), 281 (44),
202 (68), 174 (100), 146 (80), 110 (54), 104 (49) 77 (33). –
C13H15N2O6P (326.2): calcd. C 47.8, H 4.6, N 8.6, P 9.5;
found C 47.7, H 4.7, N 8.7, P 9.4.
3-[2-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)propanoyl]-
2-triazenylidene-tris-(dimethylamino)phosphorane (17)
Pale yellow material (stable for ca. two weeks in a refrig-
◦
erator). Yield: (88 %). M. p. 208 – 211 C. – IR (film): ν =
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W. M. Abdou et al. · Antimicrobial N-Phthaloyl-alanyl-derived Amidophosphates and Triazoles
1063
1774, 1730 (C(1,3)=O), 1696 (C=O), 1355 (P=N), 1335, 3452 (NH), 1754, 1720 (C(1,3)=O), 1718 (C=O, ester),
860 [P(N(Me2)3] cm−1. – 1H NMR (500 MHz, CDCl3, 1182 (triazole) cm−1. – 1H NMR (500 MHz, CDCl3, 25 ◦C,
◦
25 C, TMS): δ = 1.55 (d, J = 4.8 Hz, 3 H, H3C-C), 2.45, TMS): δ = 1.23 (t, J = 7.4 Hz, 3 H, H3CCO), 1.83 (d, J =
2.63 (2d, J =10.8 Hz, 18 H, (H3C)2N-P), 5.98 (q, J = 4.8 Hz, 6.6 Hz, 3 H, H3CC), 3.34 (q, J = 7.4 Hz, 2 H, H2CO),
1 H, HC-C), 7.77, 7.85 (2d, J = 4.8 Hz, 4 H, H-Ar). – 6.14 (q, J = 6.6 Hz, 1 H, HC-C), 7.86, 7.95 (2 × d, J =
13C NMR (500 MHz, CDCl3, TMS): δ = 16.8 (CH3-C), 37.4 4.8 Hz, 4 H, H-Ar), 8.48 (s, 1H, HN). – 13C NMR (500 MHz,
(d, 2J = 30.6 Hz, {(CH3)2N}3P], 44.4 (C-Me), 124.3, 130.4, CDCl3, TMS): δ = 13.4 (CH3C), 14.6 (CH3CO), 46.8 (CH-
134.7 (all C-Ar), 150,4, 166.4 (C(1,3)=O), 179.8 (C=O). – Me), 60.7 (CH2O), 125.4, 134.4, 135.7 (all C-Ar), 138.2
31P NMR (500 MHz, CDCl3, H3PO4): δ = 40.3 ppm. – (C(4), triazole), 151.1 (C(5)-triazole), 163.8 (C=O), 164.2
MS (EI, 70 eV): m/z (%) = 407 (15) [M]+, 392 (25) [M– (C(1,3)=O). – MS (EI, 70 eV): m/z (%) = 314 (10) [M]+,
Me]+, 379 (56) [M–N2 or M–CO]+, 191 (36) [C6H18N5P]+, 313 (13), 299 (13), 285 (18), 270 (36), 242 (100), 146 (76),
173 (100) [M–C8H21N6OP]+, 146 (82) [M–C9H22N6OP]+, 116 (54), 104 (40), 77 (46). – C15H14N4O4 (314.3): calcd.
116 (35), 104 (23), 77 (56). – C17H26N7O3P (407.4): calcd. C 57.3, H 4.5, N 17.8; found C 57.4, H 4.4, N 17.8.
C 50.1, H 6.4, N 24.1, P 7.6; found C 50.2, H 6.3, N 24.2,
P 7.5.
5-[1-(1,3-Dioxo-1,3-dihydro-2H-isoindol-2-yl)ethyl]-2H-
1,2,3-triazole-4-carbonitrile (22b)
Reaction of 1 with alkylidenephosphoranes
Eluent: n-hexane/AcOEt (1 : 1, v/v). Yield: 740 mg
(85 %). M. p. 193 – 195 C (from MeCN). – IR (film): ν =
Azide 1 (0.8 g, 3.28 mmol) and benzoylmethylenetriphen-
ylphosphorane (18) (1.3 g, 3.5 mmol) in dry chloroform
(20 mL) were boiled under reflux for 36 h. After remov-
ing the solvent, the residue was chromatographed on silica
gel to afford the triazole 19 (42 %). Next, the azide 1 (0.8 g,
3.28 mmol) and 3.5 mmol of benzoyl- (18), ethoxycarbonyl-
(20a) or cyanomethylenetriphenylphosphorane (20b) in dry
dimethylformamide (DMF) (8 mL) in a Pyrex glass beaker
were heated under microwave irradiation for 20 – 25 min. Af-
ter the completion of the reaction (TLC analysis), the volatile
materials were evaporated under reduced pressure to dryness.
The resulting residue was chromatographed on silica gel (n-
hexane/AcOEt) to give the triazoles 19, 22a and 22b, respec-
tively. Triphenylphosphine oxide was also isolated from the
above four reactions, eluent: n-hexane/AcOEt (2 : 3, v/v).
◦
3452 (NH), 2218 (CN), 1756, 1732 (C(1,3)=O),◦1186 (tri-
1
azole) cm−1. – H NMR (500 MHz, CDCl3, 25 C, TMS):
δ = 1.82 (d, J = 6.6 Hz, 3 H, H3C-C), 5.24 (q, J = 6.6 Hz,
1 H, HCMe), 7.98, 8.08 (2 ×d, J = 4.8 Hz, 4 H, H-Ar), 8.67
(s, 1H, HN). – 13C NMR (500 MHz, CDCl3, TMS): δ = 14.7
(CH3CH), 46.8 (CH-Me), 108.7 (C-CN), 124.3 (CN), 124.3,
131.4, 133.7, 134.6 (all C-Ar), 137.2 (C(5), triazole), 166.2
(C(1,3)=O). – MS (EI, 70 eV): m/z (%) = 267 (36) [M]+,
266 (32), 251 (29), 241 (31), 225 (45), 147 (100), 146 (88),
116 (68), 104 (36), 77 (25). – C13H9N5O2 (267.2): calcd.
C 58.4, H 3.4, N 26.2; found C 58.3, H 3.5, N 26.1.
Antibacterial assay
2-[1-Methyl-2-oxo-2-(5-phenyl-1H-1,2,3-triazol-1-yl)ethyl]-
1H-isoindol-1,3(2H)-dione (19)
The prepared compounds were screened for their activity
against four bacterial strains by the disc diffusion method.
A standard inoculum (1 – 2 × 107 c. f. u. mL 0.5 McFarland
standards) was introduced on to the surface of sterile agar
plates, and a sterile glass spreader was used for even dis-
tribution of the inoculum. The discs measuring 8.32 mm in
diameter were prepared from Whatman no. 1 filter paper and
sterilized by dry heat at 140 ◦C for 1 h. The sterile disc previ-
ously soaked in a known concentration of the test compounds
were placed in nutrient agar medium. Solvent and growth
controls were kept. The plates were inverted and incubated
Eluent: n-hexane/AcOEt (1 : 1, v/v). Yield: 1.0 g (90 %).
M. p. 200 – 202 ◦C (from CHCl3). – IR (film): ν = 1782, 1732
(C(1,3)=O), 1705 (C=O, amide), 1180 (triazole) cm−1. –
1H NMR (500 MHz, CDCl3, 25 ◦C, TMS): δ = 1.83 (d, J =
6.6 Hz, 3 H, H3C-C), 5.83 (q, J = 6.6 Hz, 1 H, HC-C), 6.18
(s, 1H, C(4)H-triazole), 7.51 – 7.88, 8.05 – 8.29 (2 ×m, 9 H,
H-Ar, H-Ph). – 13C NMR (500 MHz, CDCl3, TMS): δ =
17.9 (CH3CH), 56.8 (CH-Me), 122.3, 123.6, 124.3, 125.4,
131.4, 133.7, 134.3, 134.6 (all C-Ar, C-Ph), 137.2 (C(4), tri-
azole), 163.8 (C=O), 166.2 (C(1,3)=O). – MS (EI, 70 eV):
m/z (%) = 346 (18) [M]+, 345 (14), 331 (33), 318 (26), 303
(41), 146 (48), 116 (84), 104 (52), 77 (36). – C19H14N4O3
(346.3): calcd. C 65.9, H 4.1, N 16.1; found C 65.8, H 4.2,
N 16.0.
◦
for 24 h at 37 C. The inhibition zones were measured and
compared with the controls. The minimum inhibitory con-
centration (MIC) was determined by the broth dilution tech-
nique. The nutrient broth, which contained a logarithmic se-
rially twofold diluted amount of test compound and controls
were inoculated with approximately 5 × 105 c. f. u. mL of ac-
tively dividing bacteria cells. The cultures were incubated
Ethyl 5-[1-(1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)ethyl]-
2H-1,2,3-triazole-4-carboxylate (22a)
◦
for 24 h at 37 C, and the growth was monitored visually
Eluent: n-hexane/AcOEt (1 : 1, v/v). Yield: 900 mg and spectrophotometrically. The lowest concentration (high-
◦
(88 %). M. p. 168 – 170 C (from CH2Cl2). – IR (film): ν = est dilution) required to arrest the growth of bacteria was re-
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1064
W. M. Abdou et al. · Antimicrobial N-Phthaloyl-alanyl-derived Amidophosphates and Triazoles
garded as minimum inhibitory concentration (MIC). Amoxi- each Petri dish. Excess of suspension was decanted, and ◦the
cillin was used as the standard drug.
plates were dried by placing them in an incubator at 37 C.
Using an agar punch, wells were made, and each well was
labeled. A control was also prepared in four wells and main-
tained at 37 ◦C for 3 – 4 days. The inhibition zone diameters
Antifungal assay
The prepared compounds were screened for their activ- were measured and compared with those of the controls. The
ity against four fungal strains strains by the agar diffusion nutrient broth, which contained logarithmic serially twofold
method. Sabbouraud agar media were prepared by dissolv- diluted amounts of the tested compound and control were in-
ing 1 g peptone, 4 g D-glucose, and 2 g agar in 100 mL dis- oculated with approximately 1.6 – 6 × 104 c. f. u. mL of the
tilled water, and adjusting the pH to 5.7 using buffer. Normal activity fungal strains. The cultures were incubated for 48 h
saline was used to make a suspension of spores of the fungal at 35 ◦C, and the growth was monitored visually. The lowest
strain for lawning. A loopful of a particular fungal strain was concentration (highest dilution) required to arrest the growth
transferred to 3 mL saline to get a suspension of the corre- of fungus was regarded as the minimum inhibitory concen-
sponding species. 20 mL of the agar medium was poured into tration (MIC). Fluconazol was used as the standard drug.
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Unauthenticated
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