New N-(Purin-6-yl)-amino Acid and -Peptide Derivatives; Synthesis and Biological Screening

Article abstract of DOI:10.1039/a706292c

N-(Purin-6-yl)-amino acids and -peptides were synthesized from 9-(ρ-anisyl)-6-chloropurine; selected examples from the synthesized products were screened as antitumour and antiviral (HIV-1) agents.

Full text of DOI:10.1039/a706292c

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134 J. CHEM. RESEARCH (S), 1998
J. Chem. Research (S),
1998, 134±135$
New N-(Purin-6-yl)-amino Acid and -Peptide
Derivatives; Synthesis and Biological Screening$
Ahmed M. Shalaby, Wahid M. Basyouni and
Khairy A. M. El-Bayouki*
National Research Center, Dokki, Cairo, Egypt
N-(Purin-6-yl)-amino acids and -peptides were synthesized from 9-(p-anisyl)-6-chloropurine; selected examples from
the synthesized products were screened as antitumour and antiviral (HIV-1) agents.
The naturally occurring N-(purin-6-yl)amino acids1,2 are
ArH), 7.76 (d, 2 H, ArH), 8.05 (br, 1 H, NH, D2O-exchangeable),
8.28 (s, 1 H, 8-H), 8.52 (s, 1 H, 2-H); m/z 299 (M+).
important
intermediates
in
biochemical
processes.
N-[9-(p-Anisyl)purin-6-yl]-L-valine 3b (62%): mp 115±117 8C
(Found: C, 59.7; H, 5.7; N, 20.7. C17H19N5O3 requires C, 59.82;
Adenylsuccinic acid (9-ribosyl-6-aspartopurine-5'-monophos-
phate) is an intermediate product in the amination of
inosinic acid (IMP) to adenylic acid (AMP).2Also, synthetic
6- and 9-substituted purine derivatives have been previously
reported for their antitumour3,4 and antiviral5 activity, as
cardiovascular agents6 and for their use as hepadnaviride-
active antiviral agents.7
Therefore, the present work was aimed at synthesizing
new N-(purin-6-yl)-amino acid and -peptide derivatives
expected to have antitumour and antiviral activity.
1
H, 5.57; N, 20.53%); ꢀmax/cm 3293 (NH), 1718 (C1O); 1251
(CO2H); dH 1.02(t, 6 H, g-CH3), 2.32 (m, 1 H, b-CH), 3.84 (s, 3 H,
OCH3), 4.05 (m, 1 H, a-CH), 7.15 (d, 2 H, ArH), 7.53 (br, 1 H,
NH, D2O-exchangeable), 7.76 (d, 2 H, ArH), 8.28 (s, 1 H, 8-H),
8.55 (s, 1 H, 2-H); m/z 341 (M+).
N-[9-(p-Anisyl)purin-6-yl]-L-threonine 3c (67%): mp 207±209 8C
(Found: C, 56.1; H, 5.0; N, 20.3. C16H17N5O4 requires C, 55.98;
1
H, 4.96; N, 20.41%); ꢀmax/cm 3363 (NH), 1706 (C1O), 1252
(CO2H); dH 1.22 (d, 3 H, g-CH3), 3.84 (s, 3 H, OCH3), 4.35 (m, 1
H, b-CH); 4.75 (d, 1 H, a-CH); 5.56 (br, 1 H, OH, D2O-exchange-
able), 7.07 (br, 1 H, NH, D2O-exchangeable), 7.16 (d, 2 H, ArH),
7.77 (d, 2 H, ArH), 8.30 (s, 1 H, 8-H), 8.50 (s, 1 H, 2-H); m/z 343
(M+).
When 9-( p-anisyl)-6-chloropurine8 (1) was allowed to
react with the sodium salt of various amino acids under
re¯ux at pH 9±9.5, the corresponding N-[9-( p-anisyl)purin-
6-yl]amino acid derivatives 3a±h were a€ored (Scheme 1).
The structure of products 3a±h was elucidated by careful
study of their IR absorption spectra which showed ꢀNH and
N-[9-(p-Anisyl)purin-6-yl]-L-methionine 3d (71%): mp 147±149 8C
(Found: C, 54.5; H, 5.0; N, 19.0. C17H19N5O3S requires C, 54.69;
1
H, 5.09; N, 18.77%); ꢀmax/cm 3302 (NH), 1718 (C1O), 1249
(CO2H); dH 2.05 (s, 3 H, SCH3) 2.20 (m, 2 H, b-CH2), 2.60 (m, 2 H,
g-CH2), 3.85 (s, 3 H, OCH3), 4.40 (m, 1 H, a-CH), 7.10 (d, 2 H,
ArH), 7.75 (d, 2 H, ArH), 8.10 (br, 1 H, NH, D2O-exchangeable),
8.25 (s 1 H, 8-H), 8.52 (s, 1 H, 2-H); m/z 373 (M+).
1
ꢀC1O in the 3413±3281 and 1728±1706 cm regions respect-
ively, in addition to another band in the 1254±1242 cm
1
region for a CO2H group.9
N-[9-(p-Anisyl)purin-6-yl]-L-aspartic 3e (68%):, mp 197±199 8C
(Found: C, 54.0; H, 4.1; N, 19.5. C16H15N5O5 requires C, 53.78;
The N-[9-( p-anisyl)purin-6-yl]peptides 5a±c were syn-
thesized from reaction of 3c, e and f with the appropriate
amino acid ester hydrochloride.
1
H, 4.20; N, 19.61%); ꢀmax/cm 3383 (NH), 1710 (C1O); dH 2.93
Biological Screeening.Ð(1) Antitumour screening. Anti-
tumour activity screening of products 3a, b, d, and f and 5c
was carried out against 60 human tumour cell lines derived
from nine cancer types (leukaemia, non-small cell lung,
colon cancer, CNS cancer, melanoma, ovarian cancer, renal
cancer, prostate cancer and breast cancer) according to
a well known procedure.10,11 All the compounds tested
showed no signi®cant activity against the tested tumour cell
lines.
(2) Anti-HIV screening. The products 3a, b, d and f
and 5c were evaluated for in vitro anti-HIV-1 activity.
The procedure12 used for agents active against human
immunode®ciency virus (HIV) is designed to detect agents
acting at any stage of the virus reproductive cycle. The
tested compounds showed no signi®cant activity.
Experimental
N-(Purin-6-yl)amino Acids 3a±h: General Procedure.ÐThe amino
acid (9.60 mmol) and sodium carbonate (5.40 mmol) were dissolved
in water (10 ml), then adjusted to pH 9±9.5. The 6-chloropurine 1
(4.80 mmol) was added and then the mixture was stirred at 100 8C
for 6 h with control of pH. The reaction mixture was left overnight
at room temperature, then treated with formic acid (88%). The
solid product obtained was ®ltered o€, washed with water and
puri®ed using preparative silica gel TLC plates to give 3a±h.
N-[9-(p-Anisyl)purin-6-yl]glycine 3a (70%): mp 251±253 8C
(Found: C, 56.3; H, 4.2; N, 23.2. C14H13N5O3 requires C, 56.19;
1
H, 4.35; N, 23.41%); ꢀmax/cm 3413 (NH), 1718 (C1O), 1242
(COOH) dH 3.84 (s, 3 H, OCH3), 4.18 (s, 2 H, a-CH2), 7.14 (d, 2 H,
*To receive any correspondence.
$This is a Short Paper as de®ned in the Instructions for Authors,
Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there-
fore no corresponding material in J. Chem. Research (M).
Scheme 1

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J. CHEM. RESEARCH (S), 1998 135
Scheme 2
(d, 2 H, b-CH2), 3.84 (s, 3 H, OCH3), 5.14 (m, 1 H, a-CH), 7.15
(d, 2 H, ArH), 7.76 (d, 2 H, ArH), 7.96 (br, 1 H, NH, D2O-
exchangeable), 8.31 (s, 1 H, 8-H), 8.55 (s, 1 H, 2-H); m/z 357 (M+).
N-[9-(p-Anisyl)purin-6-yl]-L-phenylalanine 3f (69%): mp 122±
124 8C (Found: C, 64.8; H, 5.0, N, 18.1. C21H19N5O3 requires C,
ester), 1654 (C1O amide); dH (CDCl3) 2.67 (d, 6 H, 2 ÂNCH3),
3.10 (m, 2 H, b-CH2 asp.), 3.45 (m, 2 H, CH2 sar.), 3.70 (m, 2 H,
CH2 sar.), 3.86 (d, 6 H, 2Â OCH3), 4.20 (m, 1 H, a-CH asp.), 6.05
(br, 1 H, NH, D2O-exchangeable), 7.06 (d, 2 H, ArH), 7.50 (m, 3 H,
ArH, CONH), 8.60 (s, 1 H, 8-H), 8.80 (s, 1 H, 2-H).
1
64.78; H, 4.88; N, 17.99%); ꢀmax/cm 3281 (NH), 1716 (C1O),
N-[9-(p-Anisyl)purin-6-yl]-L-phenylalanyl-L-valine methyl ester 5c
(42%): mp 194±196 8C (Found: C, 64.7; H, 6.1; N, 17.0.
1251 (CO2H); dH 3.27 (d, 2 H, b-CH2), 3.83 (s, 3 H, OCH3), 4.95
(q, 1 H, a-CH), 7.00±7.40 (m, 7 H, Ph, ArH), 7.75 (d, 2 H, ArH),
7.85 (br, 1 H, NH, D2O-exchangeable), 8.24 (s, 1 H, 8-H), 8.85
(s, 1 H, 2-H); m/z 389 (M+).
1
C27H30N6O4 requires C, 64.54; H, 5.98; N, 16.73%); ꢀmax/cm 3326
(NH), 1738 (C1O ester), 1622 (C1O amide); dH 1.05 (m, 6 H,
2 ÂCH3), 2.20 (m, 1 H, b-CH val.), 3.30 (s, 2 H, CH2), 3.80 (d, 6 H,
2 ÂOCH3); 4.15 (m, 1 H, a-CH val.), 5.55 (d, 1 H, a-CH phe.), 5.80
(br, 1 H, NH, D2O-exchangeable), 7.00±7.90 (m, 10 H, Ph, ArH,
CONH), 8.70 (s, 1 H, 8-H), 8.80 (s, 1 H, 2-H); m/z 502 (M+).
Biological Screening.ÐThe biological activity screening was
carried out at the National Cancer Institute, Bethesda, Maryland,
USA.
N-[9-(p-Anisyl)purin-6-yl]-L-histidine 3 g (60%): mp 257±259 8C
(Found: C, 57.1; H, 4.6; N, 26.0. C18H17N7O3 requires C, 56.99;
1
H, 4.49; N, 25.86%); ꢀmax/cm 3380 (NH), 1728 (C1O), 1254
(CO2H); dH 3.80 (d, 2 H, b-CH2), 3.86 (s, 3 H, OCH3), 4.60
(m, 1 H, a-CH), 7.15 (d, 2 H, ArH), 7.67 (d, 2 H, ArH), 7.80 (d, 1
H, 4-H, his.), 8.10 (s, 1 H, 2-H, his.), 8.37 (s, 1 H, 8-H), 8.49 (s, 1
H, 2-H), 9.01 (br, 1 H, NH, D2O-exchangeable); m/z 379 (M+).
N-[9-(p-Anisyl)purin-6-yl]-L-proline 3 h (60%): mp 132±134 8C
(Found: C, 60.3; H, 5.0; N, 20.5. C17H17N5O3 requires C, 60.18; H,
Received, 28th August 1997; Accepted, 26th November 1997
Paper E/7/06292C
1
5.01; N, 20.65%); ꢀmax/cm 1728 (C1O), 1248 (CO2H); dH 2.05
(m, 2 H, g-CH2), 2.34 (m, 2 H, b-CH2), 3.78 (m, 1 H, d-CH2), 3.84
(s, 3 H, OCH3), 4.23 (m, 1 H, d-CH2), 4.68, 5.41 (2d, 1 H, a-CH),
7.15 (d, 2 H, ArH), 7.75 (d, 2 H, ArH), 8.29 (d, 1 H, 8-H), 8.51
(d, 1 H, 2-H); m/z 339 (M+).
References
1 A. Ballio, S. Barcellona and V. DiVittorio, Arch. Biochem.
Biophys., 1963, 101, 311.
N-(Purin-6-yl)peptides 5a±c: General Procedure.ÐTo
a stirred
cold (ice-bath) solution of 3c, e or f (5 mmol) and N-hydroxy-
succinimide (5 mmol) in THF (20 ml) dicyclohexylcarbodiimide
(DCC) (5 mmol) was added. Stirring was continued for 2 h at
0±5 8C. The N,N'-dicyclohexylurea which separated was removed by
®ltration and the solvent was evaporated in vacuo to give the active
esters 4.
2 C. E. Carter and L. H. Cohen, J. Am. Chem. Soc., 1955, 77,
499.
3 M. E. Olah and G. L. Stiles, Annu. Rev. Pharmacol. Toxicol.,
1995, 35, 581.
4 Kh. A. M. El-Bayouki, W. M. Basyouni, S. M. El-Din and A.
G. Habeeb, Arch. Pharm. Res., 1994, 17, 60.
To a stirred cold (ice-bath) solution of 4 (4 mmol) in THF
(20 ml), the desired amino acid ester hydrochloride (4 mmol) and
triethylamine (4 mmol) in tetrahydrofuran (20 ml) were added.
Stirring was continued for 4 h while cooling and the pH was
adjusted to 8±9. Stirring was continued at room temperature for a
further 3 h and then the mixture was ®ltered.
5 G. Kozulka, T. Krentsky, J. Rideout and C. Burns, Eur. Pat.,
286,425, 1988 (Chem. Abstr., 1989, 111, 23910w).
6 A. Matsuda, T. Yamaguchi, T. Azebriru and Y. Watanabe, Jpn.
Kokai Tokkyo Koho, JP 05 09,198, 1993 (Chem. Abstr., 1993,
118, 192193q).
7 M. S. Marcuccio, G. Holan, P. A. Coghlan, K. E. Jarvis, A. D.
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95 22,330, 1995 (Chem. Abstr., 1996, 124, 202289r).
8 Kh. A. M. El-Bayouki, A. S. El-Sayed and W. M. Basyouni,
Gazz. Chim. Ital., 1989, 119, 163.
N-[9-(p-Anisyl)purin-6-yl]-L-threonyl-L-valine methyl ester 5a
(46%): mp 159±161 8C (Found: C, 58.1; H, 6.3; N, 18.2.
1
C22H28N6O5 requires C, 57.89; H, 6.14; N, 18.42%); ꢀmax/cm 3327
(NH), 1741 (C1O ester), 1624 (C1O amide); dH (CDCl3) 0.70±
1.40 (m, 9 H, 3Â CH3), 1.90 (m, 1 H, b-CH val.), 3.80 (m, 1 H, b-
CH thr.); 3.85 (s, 6 H, 2Â OCH3), 4.20 (m, 1 H, a-CH thr.), 4.32
(m, 1 H, a-CH val.), 5.15 (br, 1 H, OH, D2O-exchangeable)), 6.15
(br, 1 H, NH, D2O-exchangeable); 7.05 (d, 2 H, ArH), 7.40±7.70
(m, 3 H, ArH, CONH), 8.55 (d, 1 H, 8-H), 8.85 (d, 1 H, 2-H).
N-[9-(p-Anisyl)purin-6-yl]-L-aspartylsarcosine methyl ester 5b
(40%): oil (Found: C, 54.5; H, 5.3; N, 18.8. C24H29N7O7 requires
C, 54.65; H, 5.50; N, 18.60%); ꢀmax/cm 1, 3320 (NH), 1684 (C1O
9 L. J. Bellamy, The Infra-red Spectra of Complex Molecules,
Wiley, New York, 1975, p. 275.
10 M. C. Alley, D. C. Scudiero, A. Monks, M. L. Hugsey, M. J.
Czerwinski, D. L. Fine, B. J. Abbott, J. C. Mayo, R. H.
Shoemaker and M. R. Boyd, Cancer Res., 1988, 48, 589.
11 M. R. Boyd, Principles and Practices of Oncology, 1989, 3, 1.
12 O. W. Weislow, R. Kiser, D. Fine, J. Bader, R. H. Shoemaker
and M. R. Boyd, J. Natl. Cancer Inst., 1989, 81, 577.