Amino acid derivatives, VI [1]: Synthesis, antiviral, and antimicrobial evaluation of α-amino acid esters bearing a 1,2,3-triazolo[4,5-d] pyrimidinedione side chain

Article abstract of DOI:10.1007/s00706-007-0745-8

A series of peptide and dipeptide derivatives conjugated with a 1,2,3-triazolo[4,5-d]pyrimidinedione residue were synthesized. The new compounds were evaluated in vitro for cytotoxicity against HAV-27 and HSV-1 and showed moderate activity. The prepared compounds were tested for antimicrobial activity against four different bacterial species, and they displayed different degrees of antibacterial activities or inhibitory actions.

Full text of DOI:10.1007/s00706-007-0745-8

Monatshefte fu¨r Chemie 139, 61–68 (2008)
DOI 10.1007/s00706-007-0745-8
Printed in The Netherlands
Amino Acid Derivatives, VI [1]: Synthesis, Antiviral,
and Antimicrobial Evaluation of a-Amino Acid Esters Bearing
a 1,2,3-Triazolo[4,5-d]pyrimidinedione Side Chain
ꢀ
Adel A.-H. Abdel-Rahman
Department of Chemistry, Faculty of Science, Menoufia University, Shebin El-Koam, Egypt
Received June 18, 2007; accepted (revised) June 19, 2007; published online November 14, 2007
# Springer-Verlag 2007
Summary. A series of peptide and dipeptide derivatives con-
and due to the pharmacological properties of triazo-
jugated with a 1,2,3-triazolo[4,5-d]pyrimidinedione residue
were synthesized. The new compounds were evaluated in vitro
for cytotoxicity against HAV-27 and HSV-1 and showed mod-
erate activity. The prepared compounds were tested for an-
timicrobial activity against four different bacterial species, and
they displayed different degrees of antibacterial activities or
inhibitory actions.
lopyrimidines and amino acid derivatives we were
prompted to prepare new 1,2,3-triazolo[4,5-d]pyrim-
idinediones bearing amino acid derivatives as poten-
tial antiviral and antimicrobial candidates.
Results and Discussion
Keywords. Triazolopyrimidines; Amino acids; Dipeptides;
Antiviral activity; Antimicrobial activity.
Chemistry
The starting material 1-acetylhydrazine-4,6-dimeth-
yl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-5,7(4H,6H)-
dione (1) [25] was synthesized by refluxing
1-carbethoxymethyl-4,6-dimethyl-1H-[1,2,3]triazolo-
[4,5-d]pyrimidine-5,7(4H,6H)-dione [25, 26] with
hydrazine hydrate in ethanol. This hydrazide was
selected as a starting material for the coupling reac-
tion with the appropriate acylated amino acides, via
the azide-coupling method [27]. Thus, treatment of 1
at ꢁ5ꢂC in AcOH and 1 N HCl with NaNO2 afforded
the inseparable azide derivative. The yellow syrupy
azide compound was then treated, in situ, with the
appropriate amino acid methyl esters in ethyl acetate
containing Et3N at 0ꢂC to give, after neutralization,
the desired peptides 2–9 in 75–80% yields. The
structures of 2–9 were assigned from their 1H,
Introduction
Much attention has been paid to the synthesis of
various triazolopyrimidines due to their CNS de-
pressant [2], antibacterial [3–6], antimicrobial [7],
anti-inflammatory [8–11], antiallergy [12], and her-
bicidal activities [13–16]. On the other hand, a new
target for the development of anti-HIVand antitumor
therapies has been reported by the use, in vivo and
in vitro, of amino acid derived heterocycles. Such
compounds are the lysyl amide prodrug of 2-(4-
amino-3-methylphenyl)-5-fluorobenzothiazole [17],
amino acid derivatives of paclitaxel [18], cysteine-
modifying agents [19], and isoquinoline carboxylic
acid derivatives as building blocks for HIV protease
inhibitors [20]. In connection with our strategy in
synthesis of new ꢀ-amino acid derivatives [21–24]
1
13C NMR, and mass spectra. The H NMR spectra
showed a broad singlet at ꢁ ¼ 9.70–7.15 ppm corre-
sponding to NH. The two protons of N1–CH2
appeared as a singlet at ꢁ ¼ 5.57–5.43 ppm, while
ꢀ
Corresponding author. E-mail: adelnassar63@hotmail.com

62
A. A.-H. Abdel-Rahman
Scheme 1
Scheme 2

Amino Acid Derivatives, VI
63
OCH3 group appeared as a singlet at ꢁ ¼ 3.88–
3.63 ppm. The protons of the side chain were fully
analyzed as well as the remaining protons. The 13C
NMR spectra of 2–9 were fully analyzed (Experi-
mental section) (Scheme 1).
105 cells, compounds 9, 18, 23, and 24 revealed the
highest antiviral activity in this series of compounds
and compounds 7 and 17 revealed high activity at
10 ꢂg=10 cells using amantadine (C ) as a control.
Compounds 3, 6, 8, 14, 16, and 18–21 showed mod-
erate activity, while at concentration of 20 ꢂg=105
cells, compounds 2, 4, 5, 13, 15, and 22 revealed
little antiviral activity.
For the antiviral activity against Herpes Simplex
virus-1 (HSV-1) the results revealed that compounds
7–9 and 18–24 showed the highest effect on HSV-1
at concentration 10 ꢂg=105 cells, while compounds
2–6 and 13–17 showed moderate activity.
5
ꢀ
Treating of 2–4 with N2H4 ꢃ H2O in ethanol at re-
flux temperature afforded the corresponding hydra-
zides 10–12 in 96% yield. Treatment of 10–12 at
ꢁ5ꢂC in AcOH and 1 N HCl with NaNO2 afforded
the inseparable azide derivatives. The yellow syrupy
azide compounds were treated, as mentioned above,
with the appropriate amino acid methyl esters in
ethyl acetate containing Et3N at 0ꢂC to afford 13–
24 in 78–85% yields. The structures of the dipeptide
1
derivatives were confirmed by their H, 13C NMR,
Antimicrobial Activity
and mass spectra. Compound 21 was selected for the
1
1H and 13C NMR analysis. The H NMR spectrum
The newly synthesized compounds were tested for
their antimicrobial action [29, 30] against four dif-
ferent bacterial species namely, Pseudomonas sp.
(Gram negative bacterium), Bacillus subtilis (Gram
showed a broad signal at ꢁ ¼ 9.02 ppm, characterized
by D2O exchange as NH group. The multiplet at
ꢁ ¼ 4.61–4.50 ppm was identified as two CH groups,
while the two singlets at ꢁ ¼ 4.50 and 3.65 ppm were
attributed to N1–CH2 and OCH3. The multiplet at
ꢁ ¼ 2.50–2.22 ppm was identified as two CH2 and
SCH3. Finally, the doublet at ꢁ ¼ 1.39 ppm is corre-
sponding to CH3. The 13C NMR spectrum demon-
strated three higher field signals at ꢁ ¼ 176.0, 175.0,
and 163.0 ppm which were assigned to three C¼O
groups in the side chain, while the two C¼O groups
in the pyrimidine ring (C-7) and (C-5) were assigned
at 154.2 and 150.7. The resonances at ꢁ ¼ 152.2 and
111.9 ppm were assigned to the two fused carbons
(C-3a) and (C-7a). The methyl of the carboxylate
group and N1–CH2 were resonated at ꢁ ¼ 52.0 and
51.1 ppm. The two signals at ꢁ ¼ 49.9 and 45.7 ppm
were identified as two CH groups. The two methy-
lene groups, N4–CH3 and N6–CH3, were resonated
at ꢁ ¼ 31.0, 29.9, 29.3, and 27.7 ppm, while the low-
er field signals at ꢁ ¼ 17.7 and 14.7 ppm were
assigned as CH3 and SCH3 group (Scheme 2).
Table 1. Antimicrobial activity of the newly synthesized
compounds 2–9 and 13–24
Compd no. Pseudomonas Bacillus Bacillus Streptomyces
sp.
subtilis cereus
sp.
Amoxicillin
(Penicillin)
ꢁ
þþ þþþ
þ
2
3
4
5
6
7
8
9
13
14
15
16
17
18
19
20
21
22
23
24
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þ
þþþ þþþ
þþþþ þþþ
þþþ þþþ
þþ
þ
þ
þþ
þ
þ
þ
ꢁ
þ
þþþþ
þþ
þ
ꢁ
þþ
þ
þþþ þþþ
þ
þþ
þþ
þ
þþþþ þþþþ
þþþþ þþþþ
þþþþ þþþþ
þþþþ þþþþ
þþþþ þþþ
þþþþ þþþþ
þþþ þþþ
þþþ þþþ
þþþ þþþ
þþ
þþ
þþ
þ
þ
þ
Antiviral Activity
þ
þþ
þ
The plaque infectivity assay [28] was carried out to
test the prepared compounds for antiviral activity.
The test was performed to include three possibilities
for antiviral activity, virucidal effect, virus adsorp-
tion, and effect on virus replication for both HAV-27
and HSV-1.
þþ
þþ
þþ
þþ
þ
þ
ꢁ No antibacterial effect
þ Low antibacterial effect
þþ Moderate antibacterial effect
þþþ High antibacterial effect
þþþþ Complete antibacterial effect
For the antiviral activity against HAV-27 it was
noticed that, at both concentrations 10 and 20 ꢂg=

64
A. A.-H. Abdel-Rahman
tate, washed with 150cm3 NaHCO3 (3%), 150cm3 H2O, and
dried (Na2SO4). A solution of the appropriate amino acid
methyl ester hydrochloride (4.5mmol) in 100cm3 ethyl ace-
tate containing 1.0 cm3 Et3N was stirred at 0ꢂC for 20 min,
filtered, and the filtrate was added to the azide solution.
The mixture was kept at ꢁ5ꢂC for 12h, then at room temper-
ature for another 12h, followed by washing with 150 cm3
0.5 N HCl, 150 cm3 NaHCO3 (3%), 150cm3 H2O, and dried
(Na2SO4). The filtrate was evaporated under reduced pressure,
and the residue was purified by silica gel column chromatog-
raphy using petroleum ether:ethyl acetate ¼ 5:1 to afford 2–9
in 75–80% yields.
positive bacterium), Bacillus cereus (Gram positive
bacterium), and Streptomyces sp. (one of the impor-
tant actinomycetes). All the tested compounds ex-
hibited different degrees of antibacterial activities
or inhibitory actions. The most susceptible organ-
isms were the two Gram positive bacteria (Bacillus
subtilis and Bacillus cereus) followed by Strepto-
myces sp., while the lowest inhibitory effect was
encountered in the case of Pseudomonas sp. The
highest degrees of inhibition were recorded for com-
pounds 3, 7, and 14–19 followed by 2, 4, 9, and
20–22, while the lowest degree of inhibition was
recorded for the compounds 5, 6, 8, 13, 23, and 24
(Table 1). The results were compared to amoxicillin
(penicillin) as a reference drug.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-glycine methyl ester
(2, C11H14N6O5)
White foam (75%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 3.40
(s, N6–CH3), 3.60 (s, N4–CH3), 3.65 (s, OCH3), 4.15 (s, CH2),
5.50 (s, N1–CH2, 7.20 (br, s, NH) ppm; 13C NMR (DMSO-d6,
62.5MHz): ꢁ ¼ 27.8 (N6–CH3), 29.8 (N4–CH3), 51.9 (N1–
CH2), 52.0 (CH2), 53.5 (OCH3), 111.5 (C-7a), 150.5 (C-5),
152.9 (C-3a), 154.8 (C-7), 167.3 (C¼O), 172.9 (C¼O) ppm;
MS (MALDI, positive mode, Matrix: DHB): m=z (%) ¼ 333
(22) [Mþ Na]þ, 349 (45) [Mþ K]þ.
Conclusions
New ꢀ-amino acid derivatives bearing a 1,2,3-tria-
zolo[4,5-d]pyrimidine-5,7(4H,6H)-dione residue were
synthesized in order to increase the number of po-
tential compounds screened for antiviral and antimi-
crobial activity.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-alanine methyl ester (3,
C12H16N6O5)
White foam (76%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 1.48
(d, J ¼ 5.0 Hz, CH3), 3.44 (s, N6–CH3), 3.65 (s, N4–CH3),
3.88 (s, OCH3), 4.66 (q, J ¼ 5.0 Hz, CH), 5.48 (s, N1–CH2),
7.22 (br, s, NH) ppm; 13C NMR (DMSO-d6, 62.5MHz):
ꢁ ¼ 17.3 (CH3), 28.1 (N6–CH3), 29.5 (N4–CH3), 47.3 (CH),
52.5 (N1–CH2), 54.3 (OCH3), 111.7 (C-7a), 151.3 (C-5), 153.5
(C-3a), 154.5 (C-7), 167.7 (C¼O), 173.7 (C¼O) ppm; MS
(MALDI, positive mode, Matrix: DHB): m=z (%) ¼ 347 (33)
[Mþ Na]þ, 363 (51) [Mþ K]þ.
Experimental
General
Melting points were determined using a Kofler block instru-
ment. TLC was performed on plastic plates Silica Gel 60 F254
(E. Merck, layer thickness 0.2mm). NMR spectra were
recorded on a Bruker AC 250 FT NMR spectrometer at
250 MHz for 1H NMR and 62.9 MHz for 13C NMR with
TMS as an internal standard. MALDI-MS were measured with
a KRATOS Analytical Compact, using 2,5-dihydroxybenzoic
acid (DHB) as matrix. The (Mþ Na)þ and (Mþ K)þ ions
were peak-matched using ions derived from the 2,5-dihydroxy-
benzoic acid matrix. The microanalyses were performed at the
microanalytical unit, Tokyo University, Japan, and were found
to agree favorably with the calculated values. Viral screening
against HAV and HSV was conducted at the Environmental
Virology Lab., Department of Water Pollution Research,
National Research Centre, Cairo, Egypt. Antimicrobial activi-
ty of the synthesized compounds was conducted at the Botany
Department, Faculty of Science, Menoufia University, Shebin
El-Koam, Egypt.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-serine methyl ester
(4, C12H16N6O6)
1
White powder (79%); mp 180–181ꢂC; H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.36–3.40 (m, CH2) 3.45 (s, N6–CH3), 3.63 (s,
N4–CH3), 3.71 (s, OCH3), 4.45–4.50 (m, CH), 5.48 (s, N1–
CH2), 6.66 (br, s, OH), 7.15 (br, s, NH) ppm; 13C NMR
(DMSO-d6, 62.5MHz): ꢁ ¼ 28.3 (N6–CH3), 29.9 (N4–CH3),
52.8 (N1–CH2), 53.4 (OCH3), 54.7 (CH), 72.0 (OCH2), 112.1
(C-7a), 151.2 (C-5), 153.6 (C-3a), 155.3 (C-7), 167.6 (C¼O),
173.9 (C¼O) ppm; MS (MALDI, positive mode, Matrix:
DHB): m=z (%) ¼ 363 (34) [Mþ Na]þ, 379 (21) [Mþ K]þ.
General Procedure for the Preparation of 1,2,3-Triazolo[4,5-
d]pyrimidinedione Bearing Amino Acid Esters 2–9
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-valine methyl ester
(5, C14H20N6O5)
White foam (77%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 0.94
(dd, J ¼ 1.9, 7.2 Hz, 2CH3), 2.18–2.26 (m, CH), 3.41 (s, N6–
CH3), 3.57 (s, N4–CH3), 3.63 (s, OCH3), 4.32–4.40 (m, CH),
A solution of 1.0 g 1 (4mmol) in 30cm3 HOAc, 15 cm3 1 N
HCl, and 125 cm3 H2O was cooled in an ice-bath (ꢁ5ꢂC).
NaNO2 (4.35 g, 63mmol) in 15 cm3 cold H2O was added with
stirring. After stirring at ꢁ5ꢂC for 15min, the yellow syrup
was formed. The azide was taken in 150 cm3 cold ethyl ace-

Amino Acid Derivatives, VI
65
5.52 (s, N1–CH2), 8.44 (br, s, NH) ppm; 13C NMR (DMSO-d6,
62.5MHz): ꢁ ¼ 16.8 (CH3), 18.8 (CH3), 27.8 (N6–CH3), 29.8
(N4–CH3), 30.9 (CH), 51.8 (CH), 52.6 (N1–CH2), 57.5
(OCH3), 111.8 (C-7a), 150.8 (C-5), 152.4 (C-3a), 154.9 (C-
7), 167.9 (C¼O), 175.4 (C¼O) ppm; MS (MALDI, positive
mode, Matrix: DHB): m=z (%) ¼ 375 (40) [Mþ Na]þ, 391
(18) [Mþ K]þ.
29.6 (N4–CH3), 37.5 (CH2), 51.6 (N1–CH2), 52.6 (CH), 53.3
(OCH3), 111.8 (C-7a), 126.5 128.1, 128.9, 135.4 (Ph–C),
150.3 (C-5), 152.2 (C-3a), 154.0 (C-7), 167.6 (C¼O), 171.9
(C¼O) ppm; MS (MALDI, positive mode, Matrix: DHB): m=z
(%) ¼ 423 (20) [Mþ Na]þ, 439 (28) [Mþ K]þ.
General Procedure for the Preparation of the Hydrazides
10–12
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-leucine methyl ester
A mixture of 2–4 (10 mmol) and 1.25 g N2H4 ꢃ H2O (25 mmol)
in 30cm3 EtOH was heated under reflux for 3 h. The excess of
EtOH was removed under reduced pressure and the resulting
precipitate was filtered off and recrystallized from EtOH to
give 10–12 in 96% yields.
(6, C15H22N6O5)
White foam (78%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 0.89
(dd, J ¼ 1.9, 7.2 Hz, 2CH3), 1.44–1.70 (m, CH2, CH), 3.39 (s,
N6–CH3), 3.52 (s, N4–CH3), 3.64 (s, OCH3), 4.17–4.24 (m,
CH), 5.50 (s, N1–CH2), 8.17 (br, s, NH) ppm; 13C NMR
(DMSO-d6, 62.5 MHz): ꢁ ¼ 21.3 (2CH3), 24.6 (CH), 27.4
(N6–CH3), 29.2 (N4–CH3), 39.7 (CH2), 51.0 (CH), 52.9
(N1–CH2), 53.4 (OCH3), 112.3 (C-7a), 151.0 (C-5), 153.5
(C-3a), 155.3 (C-7), 168.8 (C¼O), 172.4 (C¼O) ppm; MS
(MALDI, positive mode, Matrix: DHB): m=z (%) ¼ 389 (32)
[Mþ Na]þ, 405 (15) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-glycine hydrazide
(10, C10H14N8O4)
1
White powder (96%); mp 250–252ꢂC; H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.49 (s, N6–CH3), 3.53 (s, CH2), 3.67 (s, N4–
CH3), 4.82 (br, s, NHNH2), 5.34 (s, N1–CH2), 7.51 (br, s, NH),
9.45 (br, s, NHNH2) ppm; 13C NMR (DMSO-d6, 62.5 MHz):
ꢁ ¼ 27.8 (N6–CH3), 29.9 (N4–CH3), 40.4 (CH2), 51.1 (N1–
CH2), 112.6 (C-7a), 151.6 (C-5), 153.1 (C-3a), 154.7 (C-7),
164.3 (C¼O), 169.5 (C¼O) ppm; MS (MALDI, positive
mode, Matrix: DHB): m=z (%) ¼ 333 (35) [Mþ Na]þ, 349
(52) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-methionine methyl ester
(7, C14H20N6O5S)
Pale yellow foam (75%); 1H NMR (DMSO-d6, 250 MHz):
ꢁ ¼ 2.18–2.51 (m, 2CH2, SCH3), 3.44 (s, N6–CH3), 3.62 (s,
N4–CH3), 3.67 (s, OCH3), 4.43–4.50 (m, CH), 5.43 (s, N1–
CH2), 8.11 (br, s, NH) ppm; 13C NMR (DMSO-d6, 62.5MHz):
ꢁ ¼ 14.6 (SCH3), 27.4 (N6–CH3), 29.4 (CH2), 29.7 (N4–CH3),
30.6 (CH2), 46.4 (CH), 52.7 (N1–CH2), 53.0 (OCH3), 111.2
(C-7a), 151.5 (C-5), 152.7 (C-3a), 154.3 (C-7), 171.1 (C¼O),
177.2 (C¼O) ppm; MS (MALDI, positive mode, Matrix:
DHB): m=z (%) ¼ 407 (15) [Mþ Na]þ, 423 (19) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-alanine hydrazide
(11, C11H16N8O4)
1
White powder (96%); mp 266–268ꢂC. H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 1.40 (d, J ¼ 5.0 Hz, CH3), 3.44 (s, N6–CH3),
3.64 (s, N4–CH3), 4.18 (q, J ¼ 5.0 Hz, CH), 4.77 (br, s,
NHNH2), 5.42 (s, N1–CH2), 7.49 (br, s, NH), 9.34 (br, s,
NHNH2) ppm; 13C NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 8.6
(CH3), 27.3 (N6–CH3), 129.7 (N4–CH3), 46.2 (CH), 51.5
(N1–CH2), 111.9 (C-7a), 151.2 (C-5), 153.0 (C-3a), 154.6
(C-7), 163.1 (C¼O), 170.0 (C¼O) ppm; MS (MALDI, posi-
tive mode, Matrix: DHB): m=z (%) ¼ 347 (30) [Mþ Na]þ,
363 (16) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-phenylglycine methyl ester
(8, C17H18N6O5)
1
White powder (79%); mp 211–213ꢂC; H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.48 (s, N6–CH3), 3.64 (s, N4–CH3), 3.75 (s,
OCH3), 5.57 (s, N1–CH2), 4.77 (s, CH), 7.20–7.27 (m, Ph–H),
7.33–7.44 (m, Ph–H), 9.10 (br, s, NH) ppm; 13C NMR
(DMSO-d6, 62.5 MHz): ꢁ ¼ 27.9 (N6–CH3), 29.6 (N4–CH3),
52.7 (N1–CH2), 53.5 (OCH3), 56.7 (CH), 111.9 (C-7a), 125.5,
129.9, 131.1, 137.7 (Ph–C), 151.7 (C-5), 152.4 (C-3a), 154.3
(C-7), 167.6 (C¼O), 173.0 (C¼O) ppm; MS (MALDI, posi-
tive mode, Matrix: DHB): m=z (%) ¼ 409 (23) [Mþ Na]þ,
425 (13) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-serine hydrazide
(12, C11H16N8O5)
1
White powder (96%); mp 279–281ꢂC. H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.41 (s, N6–CH3) 3.62 (s, N4–CH3), 3.70–3.88
(m, CH2), 4.30–4.42 (m, CH), 4.70 (br, s, NHNH2), 5.32 (s,
N1–CH2), 6.52 (br, s, OH), 7.31 (br, s, NH), 9.30 (br, s,
NHNH2) ppm; 13C NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 29.5
(N4–CH3), 50.3 (CH), 51.9 (N1–CH2), 61.6 (OCH2), 111.8
(C-7a), 151.0 (C-5), 152.7 (C-3a), 154.7 (C-7), 162.8 (C¼O),
169.0 (C¼O) ppm; MS (MALDI, positive mode, Matrix:
DHB): m=z (%) ¼ 363 (65) [Mþ Na]þ, 379 (43) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-phenylalanine methyl ester
(9, C18H20N6O5)
1
White powder (80%); mp 195–197ꢂC; H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.09–3.24 (m, CH2), 3.41 (s, N6–CH3), 3.62 (s,
N4–CH3), 3.69 (s, OCH3), 4.85 (m, CH), 5.53 (s, N1–CH2),
7.21–7.29 (m, Ph–H), 7.36–7.45 (m, Ph–H), 9.70 (br, s, NH)
ppm; 13C NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 27.5 (N6–CH3),
General Procedure for the Preparation of Dipeptides 13–24
A solution of 10–12 (0.80 mmol) in 6 cm3 HOAc, 3 cm3
1 N HCl, and 25 cm3 H2O was cooled in an ice-bath

66
A. A.-H. Abdel-Rahman
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
(ꢁ5ꢂC). NaNO2 (0.87 g, 12.60 mmol) in 3 cm3 cold H2O
was added with stirring. After stirring at ꢁ5ꢂC for
15 min, the yellow syrup was formed. The azide was taken
in 30 cm3 cold ethyl acetate, washed with 30 cm3 NaHCO3
(3%), 30 cm3 H2O, and dried (Na2SO4). A solution of
the appropriate amino acid methyl ester hydrochloride
(0.90 mmol) in 20 cm3 ethyl acetate containing 0.2 cm3
Et3N was stirred at 0ꢂC for 20 min, filtered, and the filtrate
was added to the azide solution. The mixture was kept at
ꢁ5ꢂC for 12 h, then at room temperature for another 12 h,
followed by washing with 30 cm3 0.5 N HCl, 30 cm3
NaHCO3 (3%), 30 cm3 H2O, and dried (Na2SO4). The fil-
trate was evaporated under reduced pressure, and the res-
idue was purified by silica gel column chromatography
using petroleum ether:ethylacetate¼ 5:1 to afford 13–24 in
78–85% yields.
5,7(4H,6H)-dione}acetyl L-glycyl-L-valine methyl ester
(16, C16H23N7O6)
White foam (84%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 0.95
(dd, J ¼ 1.9, 7.3 Hz, 2CH3), 2.22–2.28 (m, CH), 3.41 (s, N6–
CH3), 3.45 (s, OCH3), 3.66 (s, N4–CH3), 3.71 (s, CH2), 3.77
(s, CH2), 4.36–4.41 (m, CH), 5.47 (s, N1–CH2), 9.02 (br, s,
NH) ppm; 13C NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 17.1, 19.0
(2CH3) 27.7 (N6–CH3), 29.5 (N4–CH3), 32.7 (CH), 43.6
(CH2), 51.0 (N1–CH2), 51.4 (CH), 56.7 (OCH3), 112.7 (C-
7a), 150.7 (C-5), 152.8 (C-3a), 154.9 (C-7), 162.9 (C¼O),
168.5 (C¼O), 175.3 (C¼O) ppm; MS (MALDI, positive
mode, Matrix: DHB): m=z (%) ¼ 432 (40) [Mþ Na]þ, 448
(15) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-glycyl-L-leucine methyl ester
(17, C17H25N7O6)
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-glycyl-L-glycine methyl ester
(13, C13H17N7O6)
White foam (79%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 0.89
(dd, J ¼ 1.8, 7.3 Hz, 2CH3), 1.42–1.62 (m, CH2, CH), 3.45 (s,
N6–CH3), 3.59 (s, OCH3), 3.64 (s, N4–CH3), 3.70 (s, CH2),
3.72 (s, CH2), 4.16–4.23 (m, CH), 5.39 (s, N1–CH2), 9.32
(br, s, NH) ppm; 13C NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 21.9
(2CH3), 24.4 (CH), 27.6 (N6–CH3), 29.5 (N4–CH3), 39.6
(CH2), 49.4 (CH2), 50.9 (CH), 51.0 (N1–CH2), 52.0 (OCH3),
111.9 (C-7a), 150.9 (C-5), 152.7 (C-3a), 154.0 (C-7), 163.0
(C¼O), 169.1 (C¼O), 172.8 (C¼O) ppm; MS (MALDI, pos-
itive mode, Matrix: DHB): m=z (%) ¼ 446 (12) [Mþ Na]þ,
462 (17) [Mþ K]þ.
White foam (78%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼
3.40 (s, N6–CH3), 3.50 (s, OCH3), 3.60 (s, N4–CH3), 3.71
(s, CH2), 3.97 (s, CH2), 5.40 (s, N1–CH2), 8.62 (br, s,
NH) ppm; 13C NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 27.6 (N6–
CH3), 29.5 (N4–CH3), 41.7 (CH2), 42.9 (CH2), 51.1 (N1–
CH2), 53.4 (OCH3), 111.7 (C-7a), 150.2 (C-5), 152.3 (C-3a),
154.0 (C-7), 163.2 (C¼O), 170.0 (C¼O), 171.0 (C¼O) ppm;
MS (MALDI, positive mode, Matrix: DHB): m=z (%) ¼ 390
(43) [Mþ Na]þ, 406 (13) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-glycyl-L-alanine methyl ester
(14, C14H19N7O6)
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-glycyl-L-methionine methyl ester
(18, C16H23N7O6S)
White foam (79%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 1.35
(d, J ¼ 5.0 Hz, CH3), 3.44 (s, N6–CH3), 3.61 (s, N4–CH3),
3.71 (s, CH2), 3.80 (s, OCH3), 4.47 (q, J ¼ 5.0 Hz, CH),
5.38 (s, N1–CH2), 9.03 (br, s, NH) ppm; 13C NMR (DMSO-
d6, 62.5MHz): ꢁ ¼ 18.4 (CH3), 27.7 (N6–CH3), 29.8 (N4–
CH3), 45.6 (CH2), 48.0 (CH), 51.1 (N1–CH2), 52.6 (OCH3),
112.9 (C-7a), 150.4 (C-5), 152.8 (C-3a), 154.9 (C-7), 162.5
(C¼O), 168.8 (C¼O), 173.3 (C¼O) ppm; MS (MALDI, pos-
itive mode, Matrix: DHB): m=z (%) ¼ 404 (25) [Mþ Na]þ,
420 (11) [Mþ K]þ.
Yellow foam (78%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼
2.19–2.48 (m, SCH3, 2CH2), 3.42 (s, N6–CH3), 3.52 (s,
OCH3), 3.63 (s, N4–CH3), 3.77 (s, CH2), 4.40–4.48 (m,
CH), 5.41 (s, N1–CH2), 8.69 (br, s, NH) ppm; 13C NMR
(DMSO-d6, 62.5MHz): ꢁ ¼ 14.6 (SCH3), 27.9 (N6–CH3),
29.0 (CH2), 29.5 (N4–CH3), 30.6 (CH2), 43.4 (CH2), 46.5
(CH), 51.2 (N1–CH2), 53.2 (OCH3), 111.7 (C-7a), 150.2 (C-
5), 152.3 (C-3a), 154.0 (C-7), 163.2 (C¼O), 171.6 (C¼O),
175.0 (C¼O) ppm; MS (MALDI, positive mode, Matrix:
DHB): m=z (%) ¼ 464 (19) [Mþ Na]þ, 480 (11) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-glycyl-L-serine methyl ester
(15, C14H19N7O7)
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-alanyl-L-glycine methyl ester
(19, C14H19N7O6)
1
White powder (85%); mp 155–157ꢂC; H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.40 (s, N6–CH3), 3.45–3.51 (m, OCH2), 3.60
(s, N4–CH3), 3.68 (s, OCH3), 3.70 (s, CH2), 4.45–4.50 (m,
CH), 5.42 (s, N1–CH2), 6.50 (br, s, OH), 7.88 (br, s, NH)
ppm; 13C NMR (DMSO-d6, 62.5 MHz): ꢁ ¼ 27.7 (N6–CH3)
29.3 (N4–CH3), 41.7 (CH2), 43.7 (CH2), 51.3 (N1–CH2),
53.5 (OCH3), 54.5 (CH), 72.0 (OCH2), 111.6 (C-7a), 150.9
(C-5), 152.7 (C-3a), 154.8 (C-7), 162.6 (C¼O), 167.7
(C¼O), 174.0 (C¼O) ppm; MS (MALDI, positive mode,
Matrix: DHB): m=z (%) ¼ 420 (22) [M þ Na]þ, 436 (10)
[M þ K]þ.
White foam (79%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 1.39
(d, J ¼ 5.0 Hz, CH3), 3.46 (s, N6–CH3), 3.63 (s, N4–CH3),
3.72 (s, OCH3), 3.94 (s, CH2), 4.64 (q, J ¼ 5.1 Hz, CH),
5.40 (s, N1–CH2), 8.82 (br, s, NH) ppm; 13C NMR (DMSO-
d6, 62.5 MHz): ꢁ ¼ 17.6 (CH3), 27.6 (N6–CH3), 29.5 (N4–
CH3), 41.9 (CH2), 44.6 (CH), 51.5 (N1–CH2), 53.7 (OCH3),
111.6 (C-7a), 150.2 (C-5), 152.3 (C-3a), 154.0 (C-7), 163.0
(C¼O), 172.3 (C¼O), 173.7 (C¼O) ppm; MS (MALDI, pos-
itive mode, Matrix: DHB): m=z (%) ¼ 404 (21) [Mþ Na]þ,
420 (15) [Mþ K]þ.

Amino Acid Derivatives, VI
67
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-alanyl-L-serine methyl ester
(20, C15H21N7O7)
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-seryl-L-methionine methyl
ester (24, C17H25N7O7S)
White foam (80%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 1.39
(d, J ¼ 5.0 Hz, CH3), 3.42 (s, N6–CH3), 3.48–3.53 (m, CH2),
3.64 (s, N4–CH3), 3.69 (s, OCH3), 4.50–4.59 (m, 2CH),
5.39 (s, N1–CH2), 7.06 (br, s, OH), 8.12 (br, s, NH) ppm;
13C NMR (DMSO-d6, 62.5 MHz): ꢁ ¼ 17.5 (CH3), 27.5 (N6–
CH3), 29.9 (N4–CH3), 44.3 (CH), 51.7 (N1–CH2), 53.7
(OCH3), 58.2 (CH), 72.2 (OCH2), 111.5 (C-7a), 150.2 (C-5),
152.3 (C-3a), 154.0 (C-7), 163.0 (C¼O), 172.2 (C¼O), 173.0
(C¼O) ppm; MS (MALDI, positive mode, Matrix: DHB):
m=z (%) ¼ 434 (32) [M þ Na]þ, 450 (12) [Mþ K]þ.
Yellow foam (83%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼
2.23–2.50 (m, 2CH2, SCH3), 3.44 (s, N6–CH3), 3.60 (s,
OCH3), 3.67 (s, N4–CH3), 3.70–3.77 (m, CH2), 4.50–4.57
(m, 2CH), 5.36 (s, N1–CH2), 7.21 (br, s, OH), 8.33 (br,
s, NH) ppm; 13C NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 14.8
(SCH3), 27.8 (N6–CH3), 29.3 (CH2), 29.8 (N4–CH3), 30.9
(CH2), 48.4 (CH), 51.0 (CH), 51.8 (N1–CH2), 53.2 (OCH3),
61.3 (OCH2), 111.8 (C-7a), 150.7 (C-5), 152.6 (C-3a), 154.1
(C-7), 162.9 (C¼O), 174.1 (C¼O), 175.0 (C¼O) ppm; MS
(MALDI, positive mode, Matrix: DHB): m=z (%) ¼ 494 (15)
[Mþ Na]þ, 510 (8) [M þ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-alanyl-L-methionine methyl
ester (21, C17H25N7O6S)
References
Yellow foam (81%); 1H NMR (DMSO-d6, 250 MHz): ꢁ ¼ 1.39
(d, J ¼ 5.1 Hz, CH3), 2.22–2.50 (m, 2CH2, SCH3), 3.42 (s,
N6–CH3), 3.61 (s, N4–CH3), 3.65 (s, OCH3), 4.50–4.61 (m,
2CH), 5.40 (s, N1–CH2), 9.02 (br, s, NH) ppm; 13C NMR
(DMSO-d6, 62.5MHz): ꢁ ¼ 14.7 (SCH3), 17.7 (CH3), 27.7
(N6–CH3), 29.3 (CH2), 29.9 (N4–CH3), 31.0 (CH2), 45.7
(CH), 49.9 (CH), 51.1 (N1–CH2), 52.0 (OCH3), 111.9 (C-
7a), 150.7 (C-5), 152.2 (C-3a), 154.2 (C-7), 163.0 (C¼O),
175.0 (C¼O), 176.0 (C¼O) ppm; MS (MALDI, positive
mode, Matrix: DHB): m=z (%) ¼ 478 (16) [Mþ Na]þ, 494
(12) [Mþ K]þ.
[1] Part V: Ali OM, Abdel-Rahman AA-H (2007) Monatsh
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1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-seryl-L-glycine methyl ester
(22, C14H19N7O7)
1
White powder (82%); mp 167–169ꢂC. H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.45 (s, N6–CH3), 3.66 (s, N4–CH3), 3.68–
3.75 (m, OCH2, OCH3), 3.93 (s, CH2), 4.50–4.55 (m, CH),
5.34 (s, N1–CH2), 7.20 (br, s, OH), 8.69 (br, s, NH) ppm; 13
C
NMR (DMSO-d6, 62.5MHz): ꢁ ¼ 27.5 (N6–CH3), 29.7 (N4–
CH3), 41.9 (CH2), 49.9 (CH), 51.2 (N1–CH2), 53.3 (OCH3),
61.4 (OCH2), 112.2 (C-7a), 150.5 (C-5), 152.3 (C-3a), 154.0
(C-7), 162.7 (C¼O), 1710.8 (C¼O), 172.4 (C¼O) ppm; MS
(MALDI, positive mode, Matrix: DHB): m=z (%) ¼ 420 (18)
[Mþ Na]þ, 436 (11) [Mþ K]þ.
1-{4,6-Dimethyl-1H-[1,2,3]triazolo[4,5-d]pyrimidine-
5,7(4H,6H)-dione}acetyl L-seryl-L-serine methyl ester
(23, C15H21N7O8)
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White powder (85%); mp 180–182ꢂC; 1H NMR (DMSO-d6,
250 MHz): ꢁ ¼ 3.42 (s, N6–CH3), 3.51–3.55 (m, OCH2),
3.62 (s, N4–CH3), 3.66–3.77 (m, OCH2, OCH3), 4.48–
4.56 (m, 2CH), 5.36 (s, N1–CH2), 6.33 (br, s, 2OH), 8.60
(br, s, NH) ppm; 13C NMR (DMSO-d6, 62.5 MHz): ꢁ ¼ 27.8
(N6–CH3), 29.8 (N4–CH3), 49.7 (CH), 51.7 (N1–CH2), 53.9
(OCH3), 56.7 (CH), 61.3 (OCH2), 72.4 (OCH2), 111.9 (C-
7a), 150.7 (C-5), 152.9 (C-3a), 154.9 (C-7), 162.8 (C¼O),
172.2 (C¼O), 173.9 (C¼O) ppm; MS (MALDI, positive
mode, Matrix: DHB): m=z (%) ¼ 450 (20) [M þ Na]þ, 466
(13) [M þ K]þ.
[16] Chen W, Jin G (2003) Heteroatom Chem 14: 607
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68
A. A.-H. Abdel-Rahman: Amino Acid Derivatives, VI
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