Nucleosides 9: Design and synthesis of new 8-nitro and 8-amino xanthine nucleosides of expected biological activity

Article abstract of DOI:10.1080/15257770.2017.1395036

The coupling reaction of 1,3-dimethylxanthine (theophylline), 3-benzylxanthine and 3-benzyl-1-methylxanthine with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose afforded the corresponding protected nucleosides, respectively. Nitration of each of the theo

Full text of DOI:10.1080/15257770.2017.1395036

Nucleosides, Nucleotides and Nucleic Acids
ISSN: 1525-7770 (Print) 1532-2335 (Online) Journal homepage: http://www.tandfonline.com/loi/lncn20
Nucleosides 9: Design and synthesis of new 8-nitro
and 8-amino xanthine nucleosides of expected
biological activity
Mosselhi A. N. M. Mohamed, Laila M. B. Abu-Alola & Nada M. G. Aljaied
To cite this article: Mosselhi A. N. M. Mohamed, Laila M. B. Abu-Alola & Nada M. G. Aljaied
(2017) Nucleosides 9: Design and synthesis of new 8-nitro and 8-amino xanthine nucleosides of
expected biological activity, Nucleosides, Nucleotides and Nucleic Acids, 36:12, 745-756, DOI:
10.1080/15257770.2017.1395036
To link to this article: https://doi.org/10.1080/15257770.2017.1395036
Published online: 14 Dec 2017.
Submit your article to this journal
Article views: 4
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at
http://www.tandfonline.com/action/journalInformation?journalCode=lncn20
Download by: [University of New England]
Date: 20 December 2017, At: 22:33

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
, VOL. , NO. , –
https://doi.org/./..
Nucleosides : Design and synthesis of new -nitro and
-amino xanthine nucleosides of expected biological
activity
Mosselhi A. N. M. Mohameda,b, Laila M. B. Abu-Alolaa, and Nada M. G. Aljaieda
aDepartment of Chemistry, Faculty of Science, Taif University, Saudi Arabia, Taif, KSA; bDepartment of
Chemistry, Faculty of Science, Cairo University, Giza, Egypt
ABSTRACT
ARTICLE HISTORY
Received  May 
Accepted  October 
The coupling reaction of 1,3-dimethylxanthine (theophylline),
3-benzylxanthine and 3-benzyl-1-methylxanthine with 1-O-acetyl-
2,3,5-tri-O-benzoyl-β-D-ribofuranose afforded the corresponding
protected nucleosides, respectively. Nitration of each of the theo-
phylline and 3-benzy-1-methyllxanthine protected nucleosides
yielded the corresponding 8-nitronucleosides derivatives, which
were reduced to give the corresponding 8-aminonucleoside
derivatives.
KEYWORDS
Synthesis; nucleoside;
biological activity; xanthine;
ribofuranose; xanthine
nucleoside
Debenzoylation of protected nucleosides formed by using
methanolic sodium methoxide afforded the corresponding free
N-nucleosides, respectively. The structures of products have been
elucidated and reported and also some of the products were
screened for their antimicrobial activity. Some of tested products
showed moderate activity.
GRAPHICAL ABSTRACT
R2
R2
N
O
N
O
N
N
H
N
1) HMDS
O
N
N
1) NO2BF4 /AcOH
H2N
HO
R1
N
N
N R1
R1
OAc
O
N
O
BzO
BzO
2) Na2S2O6
N
R2
BzO
BzO
O
O
O
O
3) NaOMe / MeOH
HO
OH
OBz
OBz
4
8
1
3
2) MeONa/MeOH
Introduction
Nucleosides are originally glycosides applied to the pyrimidine or purine ribose
derivatives obtained by alkaline hydrolysis of ribonucleic acid (RNA) isolated from
yeast[2].
N-Heterocyclic nucleoside analogs[3] represent an important class of antivi-
ral and anticancer agents[4–8] with antimicrobial and cholinesterase inhibitory
CONTACT Mosselhi A.N. M. Mohamed
mosselhimohamed@yahoo.com
Science, Taif University, Taif-Al-Haweiah, P.O. Box: , , Kingdom of Saudi Arabia.
Department of Chemistry, Faculty of
©  Taylor & Francis Group, LLC

746
M. A. N. M. MOHAMED ET AL.
NH2
N
O
N
O
N
O
N
F
NH
NH
NH
O
N
O
O
O
HO
HO
HO
HO
O
O
O
O
S
N3
Zidovudine
Zalcitabine
Stavudine
Emtricitabine
NH2
O
N
N
N
N
NH
N
N
N
N
H
HO
HO
O
O
Abacavir
Didanosine
Figure . Structures of commonly used nucleoside drugs.
activities[9–13] and are commonly used to treat hepatitis B virus[14,15], hepatitis
C virus[16,17], herpes simplex[18,19], human immunodeficiency virus (HIV) and
neoplasms[20,21]. Zalcitabine (2ꢀ,3ꢀ-dideoxycytidine, ddc), Zidovudine (azidothymi-
dine, AZT), Emtricitabine (FTC), Stavudine (2ꢀ,3ꢀ-didehydro-2ꢀ,3ꢀ-didehydro-2ꢀ,3ꢀ-
dideoxythymidine, d4T), Didanosine (2ꢀ,3ꢀ-dideoxyinosine, ddI) and Abacavir
(Figure 1) are among the essential antiretroviral nucleoside analogue reverse tran-
scriptase inhibitors (NRTIs) that are used to treat HIV/Acquired Immune Defi-
ciency Syndrome (AIDS) infections[22]
.
Moreover, alkylxanthines are used as therapeutic agents acting, among other
ways, as stimulants of the nervous system[23,24]. The well-known caffeine, present
in coffee and tea and various soft beverages, is 1,3,7-trimethylxanthine. It is also
worth noticing that 2ꢀ-deoxyxanthosine has been used in the extension of the genetic
alphabet by purine pairing with a 2,4-diaminopyrimidine nucleoside, which has a
hydrogen bonding pattern complementary to 2ꢀ-deoxyxanthosine[25]
.
Xanthine and its nucleosides are involved in a variety of intracellular metabolic
pathways as substrates and/or intermediates of numerous enzymes or enzyme
systems. Xanthine for example, a substrate of both xanthine oxidase and
xanthine dehydrogenase, is an intermediate in the formation of urate, from
hypoxanthine[26]
.
For these biological and medicinal purposes and others it is important to develop
the field of the synthesis of nucleosides. As a part our research program dealing
with the chemistry of azoles and azines nucleosides[27–35], and in continuation of
this work, it was considered worthwhile to study the coupling reaction of xanthine

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
747
derivatives with l-O-acety1-2,3-5-tri-O-benzoyl-β-D-ribofuranose to obtain new
xanthine nucleosides and also to synthesize their 8-nitro and 8-aminoderivatives.
Furthermore, the biological activities of some selected new prepared nucleosides
were tested using some of microorganisms.
Results and discussion
The first required starting materials in Scheme 1, are theophylline (1,3-
dimethylxanthine) (1a), which was obtained commercially,1-methyl-3-
benzylxanthine (1b) and 3-benzylxanthine (1c), which were prepared by literature
methods[36, 39]. Ribosylation of each of 1a-c was carried out by the silylation method
according to Vorbruggen[37] by refluxing of 1a-c in hexamethyldisilazane (HMDS)
with ammonium sulfate as a catalyst and then stirring of the silylated product
(2a-c), respectively with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (3)
in dry 1,2-dichloroethane and trimethylsilane triflate; CF3SO2OSiMe3] at room
temperature for 48 hours. This method yielded the benzoylated nucleosides 4a-c, in
about 65% yields (see Scheme). The structures of the products 4a-c were established
and confirmed on the bases of their elemental analyses and spectral data (1H &
13C NMR and MS) (see Experimental), which were consistent with the structure
of nucleosides 4a-c. Thus, the spectral data for (4a) as a typical example, revealed
in its 1H NMR spectrum a doublet at δ = 6.5–6.6 assigned to the anomeric proton
of the ribose moiety with a coupling constant equal to 4.5 Hz that corresponds to a
diaxial orientation for the 1ꢀ- and 2ꢀ-H protons, i.e., the β-configuration[27–30]
.
13C NMR spectrum of 4a revealed the chemical shifts of C- ribose
moiety.
Deprotection of the nucleosides 4a-c was carried out by reaction of each of 4a-
c with methanolic sodium methoxide. Stirring at room temperature at 15 h (TLC),
yielded the corresponding free N-nucleoside 5a, which was reported in literature[38]
and 5b,c, which hitherto have not been reported in literature yet, respectively (see
Scheme). The 1H NMR of 5a showed the expected base moiety protons in addition
to the sugar moiety protons; however no signal for aromatic protons appeared.
Nitration of the protected nucleosides, 4a and 4b by using nitronium tetraflu-
oroborate (NO2BF4) afforded 8-nitro-7-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)
1,3-disubstituted-xanthine nucleosides (6a) and (6b), respectively (Scheme). The
structures of products 6a, and 6b were confirmed by spectral [1H NMR and
1
MS] data (see Experimental). The H NMR spectra of 6a and 6b showed no 8-
CH signal at δ 8.1 and their mass spectra revealed molecular peak ions (M+) at
m/z = 669 (33%) and 745 (20%), respectively. Reduction of 8-nitro-7-(2,3,5-tri-O-
benzoyl-β-D-ribofuranosyl)-1,3-disubstituted-xanthine nucleosides (6a) and (6b)
by using sodium dithionite at 90°C afforded 8-amino-7-(2,3,5-tri-O-benzoyl-β-D-
ribofuranosyl)-1,3-disubstituted xanthine nucleosides (7a) and (7b) (Scheme 1),
respectively. The structure of 7a and 7b were established by their elemental and
spectral analyses (see Experimental).

748
M. A. N. M. MOHAMED ET AL.
BzO
O
H
OAc
O
O
Si(CH3)3
N
HMDS/
R1
N
N
3
R1
N
BzO
OBz
N
O
(NH4)2SO4
N
R2
N
O
Triflate/ (CH2)2Cl2
N
R2
2
1
R2
N
R2
N
O
N
N
O
N
N R1
O2N
N R1
NO2BF4 /AcOH
N
O
BzO
BzO
O
O
BzO
O
OBz
4
BzO OBz
6
NaOMe / MeOH
Na2S2O6
R2
N
R2
N
O
N
H2N
O
N
N
N
R1
N
N R1
BzO
BzO
O
O
HO
O
O
7
OBz
HO
OH
5
NaOMe / MeOH
H2N
R2
N
R1
1,2, 4, 5
R2
O
N
N
R1
6,7, 8
R2
N
a
CH3
CH3
CH3
H
R1
HO
O
O
a
CH3
b
c
CH2Ph
CH2Ph
CH3
CH3
b
CH2Ph
HO
OH
8
Scheme . Synthesis of xanthine, -nitro and -aminoxanthine nucleoside derivatives.
Furthermore
the
reaction
of
8-amino-7-(2,3,5-tri-O-benzoyl-β-D-
ribofuranosyl)-1,3-disubstitutedxanthine nucleosides (7a) and (7b) with methano-
lic sodium methoxide at room temperature yielded the corresponding pure free
8-amino-7-(β-D-ribofuranosy1)-1,3-disubstitutedxanthine nucleosides (8a)[38]
and (8b), which hitherto have not been reported in literature, in 52% and 50%
yield, respectively (Scheme 1). The structures of 8a and 8b were confirmed also by
ꢀH NMR, where the deuterium exchangeable signal at δ 6.8 assigned to the amino
group was observed as well as by mass spectra, m/z = 327 (M+) for 8a and m/z =
403 (M+) for 8b.
Antimicrobial activity
Twelve products, namely 4a-c, 5a-c, 7a,b and 8a,b were evaluated for their antibac-
terial and antifungal activities against two bacteria species namely, Escherichia coli
EC, and Staphylococcus aureus SA as well as two fungal species, namely Aspergillus
flavus AF, and Candida albicans CA.

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
749
Table . Antibacterial and antifungal activities of some of the synthesized compounds.
Compound No.
(EC) G−
(SA) G+
(AF) Fungus
(CA) Fungus
Control: DMSO
Ampicillin Antibacterial agent
Amphotericin B Antifungal agent
.
+++
−
.
+++
−
.
−
.
−
++
.−
.−
.−
.−
.−
.−
.−
.−
.−
.−
.−
.−
++
.−
.−
++
.−
++
.−
.−
++
.−
.−
.−
.−
a
b
c
a
b
c
a
b
a
.−
.−
++
+
.−
.−
++
+
++
.−
.−
++
+
++
.−
.−
++
+
b
a
b
.−
++
.−
.−
++
.−
Inhibition Zone Diameter (IZD∗) (mm/mg Compound Tested)
∗IZD = – mm beyond control = + (low activity).
IZD = – mm beyond control = ++ (moderate activity).
IZD = – mm beyond control = +++ (high activity)
The antibacterial and antifungal activities were carried out in the Microbiology
Division of Microanalytical Center of Cairo university, using the diffusion plate
method[40,41] a bottomless cylinder containing a measured quantity (1mI, mg/mL)
of the sample is placed on (9 cm diameter) containing a solid bacterial medium
(nutrient agar broth) or fungal medium (Dox‘s medium) which has been heavily
seeded with the spore suspension of the test organism. After incubation (24 h for
bacteria and 5 days for fungi), the diameter of the clear zone of inhibition surround-
ing the sample is taken as measure of the inhibitory power of the sample against the
particular test organism.
Most of the compounds were tested in vitro against gram negative bacteria
[Escherichia coli (EC) and gram positive bacteria [Staphylococcus aureus (SA)] and
antifungal activity against Aspergillus flavus (AF) and Candida albicans (CA). The
reference antibiotics Ampicillin (antibacterial agent) and Amphotericin B (antifun-
gal agent) were used as references to evaluate the potency of the tested compounds
under the same condition. The test results are depicted in Table 1 on the following
basis:
The solvent used was dimethylsulfoxide and concentration of the sample in 100
µg/ml.
The test results revealed that the compounds, 4c, 5a, 5b, 6b, 7a and 8a exhibited
moderate activity against the two bacterial species and all compounds showed no
activity against all fungal species against aspergillus flavus (AF), while compounds,
4c, 5b and 6b showed also moderate activity against candida albicans (CA).
Experimental
All evaporations were carried out under reduced pressure at 60°C. TLC was carried
out on aluminum sheet silica gel 60 (Fluka) and detected by UV light. All melt-
ing points were measured on an electrothermal melting point apparatus and are

750
M. A. N. M. MOHAMED ET AL.
uncorrected. The 1H and 13C NMR spectra were recorded in deuterated chloroform
(CDCl3) or deuterated dimethyl sulphoxide (DMSO-d6) at 300 MHz on a Varian
Mercury VXR-300 NMR spectrometer (Cairo University), 600 MHz Bruker NMR
spectrometer (King Abdelaziz University). Chemical shifts were related to that of
the solvent. The infrared spectra were recorded in potassium bromide discs on a Pye
-Unicam, SP300 and Shimadzu, FT IR 8101 PC infrared spectrophotometers,Taif
University. Biological activity was carried out at the Microanalytical Center of Cairo
University, Cairo, Egypt. Mass spectra were recorded on a Shimadzu GC MS-QP
1000 EX mass spectrometer at 70 e.V. Elemental analyses were carried out at the
Microanalytical Center of Cairo University, Giza, Egypt.
Synthesis of 7-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl-N-substituted xanthine
nucleosides (4a-c)
General procedure
A mixture of each of theophylline (1,3-dimethylxanthine) (1a) or 1-methyl-3-
benzylxanthine (1b) or 3-benzylxanthine (1c) (10 mmol) and dry hexamethyl-
disilazane (20 ml) was heated under reflux for 24 h with a catalytic amount of
ammonium sulfate. After the solution cooled, it was evaporated to dryness under
anhydrous condition to give the corresponding silylated derivative (2), which was
dissolved in 15 ml of dry 1,2-dichloroethane. To this was added a solution of l-
O-acety1-2,3-5-tri-O-benzoyl-β-D-ribofuranose (3) (4.80 g, 9.8 mmol) dissolved
in dry 1,2-dichloroethane (15 ml), and the mixture was treated with trimethylsilyl
trifluoromethane sulfonate (2.00 ml, l0 mmol) as catalyst. After the solution had
been stirred for 48 h (TLC) at room temperature, and then diluted with chloro-
form (30 ml), washed with a saturated solution of aqueous sodium bicarbonate
(100 ml), water (3 × 20 ml) and dried over anhydrous sodium sulfate. Separa-
tion of the pure product was achieved to silica gel column chromatography with
chloroform and acetone (9:1) as eluent. On evaporation of the main fraction and
recrystallisation from n-hexane, 4a or 4b or 4c was obtained as a white crystals,
respectively.
4a: Yield 3.3 g, (52%); m.p. 92°C; 1H NMR (CDCl3, 300 MHz), δH: 3.30 (s, 3H,
1-CH3), 3.7 (s, 3H, 3-CH3), 4.7-4-9 (m, 3H, 4ꢀ H & 5ꢀ H), 6.0–6.6 ((m, 2H, 2ꢀ H &
3ꢀ H), 6.5–6.6 (d, 1H, 1ꢀ H, J1 , 2 = 4.5 Hz), 7.29–8.0 (m, 15 H, 3 Ph), 8.11 (s, 1H,
8-H);13C NMR (CDCl3, 75 MHz), δC: 29.0, 32.1, 62.1, 74.0, 77.0, 77.5, 77.9, 106.5,
128.7–133.1, 144.8, 151.2, 151.4, 154.9, 165.9, 166.4, 166.7; MS: m/z = 624 (10%).
Anal. calcd. for C33H28N4O9 (624.60); C, 63.46; H, 4.52; N, 8.97. Found: C, 63.20;
H, 4.40; N, 8.80%.
ꢀ
ꢀ
4b: Yield, 1.90 g (70%); m.p. 119–121°C; 1H NMR (CDCl3, 300 MHz), δH: 3.30
(s, 3H, 1-CH3), 4.62–4.80 (m, 3H, 4ꢀ H & 5ꢀ H), 5.20 (s, 2H, N3-CH2), 5.93–6.01 (m,
2H, 2ꢀ H & 3ꢀ H), 6.51–6.53 (d, 1H, 1ꢀ H, J1 , 2 = 4.5 Hz), 7.18–7. 90 (m, 20 H, 4 Ph),
8.1 (s, 1H, 8-H);13C NMR (CDCl3, 75 MHz), δC: 29.0, 59.0, 62.1, 74.0, 77.0, 77.5,
77.9, 106.5, 128.7–133.1, 144.8, 151.2, 151.4, 154.9, 165.5, 165.8, 166.2, 166.5; MS:
ꢀ
ꢀ

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
751
m/z = 700 (25%). Anal. calcd. for C39H32N4O9 (700.68) C, 66.85; H,4.60; N,8.00.
Found: C, 66.60, H, 4.70; N, 7.86%.
4c: Yield, 3.2 g (47%); m.p. 101°C; IR (KBr): v¯ = 3430 (NH), 1722, 1602 (CO);
1H NMR (CDCl3, 600 MHz), δH: 3.6–3.7 (d, 1H, J = 4.5, 4ꢀ-H), 4.62- 4.70 (m, 2H,
5ꢀ H), 5.6 (s, 2H, N3-CH2), 5.67 (m, 2H, 2ꢀ H & 3ꢀ H), 5.7–5.8 (d, 1H, 1ꢀ H, J1 ,2
=
ꢀ
ꢀ
4.59 Hz), 7.2–7. 90 (m, 20 H, 4 Ph), 8.00 (s, 1H, 8-H), 11.5 (s, 1H, NH);13C NMR
(CDCl3, 75 MHz), δC: 59.0, 64.18, 65.12, 71.7, 71.9, 72.4, 76.2, 76.7, 77.35, 79.6,
95.8, 100.5, 127.4.7–133.49, 165.3, 165.5; MS: m/z = 686 (45%). Anal. calcd. for
C38H30N4O9 (686.67). C, 66.47; H, 4.40; N, 8.16. Found: C, 66.50, H, 4.30, N, 8.10%.
Deprotection of 7-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-substitutedxanthine
nucleosides (4a-c): Synthesis of 7-(β-D-ribofuranosyl)-1,3-disubstitutedxanthine
nucleosides (5a-c)
General procedure
A mixture of each of protected nucleoside 4a-c (0.5 mmol) in absolute methanol
(10 ml) and sodium methoxide (27 mg, 0.5 mmol) was stirred at room temperature
for 24 h. Evaporation of the solvent under vacuum gave colorless solid, which was
dissolved in hot water and neutralized with acetic acid. The precipitate was filtered
and dried, which was TLC pure [TLC (chloroform/ ethyl acetate) (9:1)] to give 5a-c
respectively.
5a:Yield, 80 mg, (52%); m.p 195–197°C (lit. m.p. 190–1910C[36].1H NMR
(DMSO-d6, 300 MHz), δH: 3.35 (s, 3H, 1-CH3), 3.45 (s, 3H, 3-CH3), 3.58 (m,
2H, 5ꢀH), 3.85 (m,1H, 4ꢀ H), 4.10–4.26 (m, 2H, 2ꢀ H & 3ꢀ H), 5.1 (t, 1H, 5ꢀ-OH),
5.3 (d, J = 3.8 Hz,1H, 1ꢀ-H), 5.45 (d, J = 4 Hz,1H, 3ꢀ-OH), 6.1 (d, J = 3.8 Hz, 1H,
2ꢀ-OH), 8.00 (s, 1H, 8-H).13C NMR (DMSO-d6, 75 MHz), δ C: 29.1, 32.3, 61.0, 74.0,
76.5, 77.0, 77.2, 80.5, 84.1, 110.0, 144.5, 151.1, 151.8, 155.0; MS: m/z = 312 (50%).
Anal. calcd. for C12H16N4O6 (312.29), C, 46.15; H, 5.16; N, 17.94. Found: C, 46.00;
H, 5.10; N, 17.70%.
5b:Yield, 105 mg (54%); m.p. 213–214°C; 1H NMR (DMSO-d6, 300 MHz), δH:
3.35 (s, 3H, 1-CH3), 3.6 (m, 2H, 5ꢀ H), 3.9 (dd, J = 4 Hz, 1H, 4ꢀ H), 4.0–4.3 (m,
2H, 2ꢀ H & 3ꢀ H), 5.0 (t, 1H, 5ꢀ-OH), 5.17 (d, J = 4 Hz,1H, 1ꢀ-H), 5.5 (d, J =
4 Hz,1H, 3ꢀ-OH), 6.2 (d, J = 4 Hz, 1H, 2ꢀ-OH), 7.18–7. 80 (m, 5 H, Ph), 8.00 (s, 1H,
8-H).13C NMR (DMSO-d6, 75 MHz), δ C: 29.1, 58.6, 61.0, 80.1, 81.5, 81.7.0, 82.0,
109.0, 127.0–129.0, 144.5, 151.1, 151.8, 155.0; MS: m/z = 388 (20%). Anal. calcd.
for C18H20N4O6 (388.36) C, 55.67; H, 5.19; N, 14.43. Found: C, 55.47; H, 5.21; N,
14.25%.
5c: Yield, 230 mg (61%); m.p. 255°C; IR (KBr) v¯ = 3438 (NH); 1H NMR (DMSO-
d6, 300 MHz), δH: 3.6 (m, 2H, 5ꢀ,5ꢀꢀ-H), 3.9 (m, 1H, 4ꢀ H), 4.0–4.3 (m, 2H, 2ꢀ H &
3ꢀ H), 5.0 (t, 1H, 5ꢀ-OH), 5.15 (d, J = 4 Hz, 1ꢀ-H), 5.5 (m,3H, 3ꢀ-OH & N-CH2), 6.0
(d, J = 4 Hz, 1H, 2ꢀ-OH), 7.2–7. 80 (m, 5 H, Ph), 8.2 (s, 1H, 8-H), (s, 1H, NH); MS:
m/z = 374 (42%). Anal. calcd. for C17H18N4O6 (374.35) C, 54.54; H, 4.85; N, 14.97.
Found: C, 54.60; H, 5.10; N, 14.70%.

752
M. A. N. M. MOHAMED ET AL.
Nitration of 7-(2,3,5-tri-O-benzoyl – β- D- ribofuranosyl-1,3-disubstituted
xanthine nucleosides (4a,b): Synthesis of 8-nitro-7-(2,3,5-tri-O-benzoyl-β-D-
ribofuranosyl) substituted xanthine nucleosides (6a,b)
General procedure
To a solution of nitronium tetrafluoroborate (0.79 g, 6 mmol) in glacial acetic acid
(15 ml), was added 7-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl-1,3-disubstituted-
xanthine nucleosides (4a) 0r (4b) (5 mmol) with stirring. The mixture was heated
at 90° for 1 hour, then evaporated to dryness. The residue was treated with 0.5 N
sodium bicarbonate (40 ml) and finally extracted with chloroform (3 × 50ml). The
chloroform extract was dried over sodium sulfate and evaporated. The residue was
triturated with methanol (5 ml) and the solid formed was collected. Recrystalliza-
tion from methanol gave yellow crystals of 6a or 6b, respectively.
6a: Yield, 1.5 g (45%); m.p. 198°C; 1H NMR (CDCl3, 600 MHz), δH: 3.49 (s, 3H,
1-CH3), 3.66 (s, 3H, 3-CH3), 4.7–4-9 (m, 3H, 4ꢀ H & 5ꢀ H), 6.0–6.4 ((m, 2H, 2ꢀ H &
3ꢀ H), 6.5 (d, 1H, 1ꢀ H, J1 , 2 = 4.59 Hz), 7.26–8.05 (m, 15 H, 3 Ph); MS: m/z = 669
(33%). Anal. calcd. for C33H27N5O11 (669.59); C,59.19; H,4.06; N,10.46. Found: C,
58.80; H, 4.00; N, 10.20%.
ꢀ
ꢀ
6b: Yield, 1.5 g (43%); m.p. 116°C; 1H NMR (CDCl3, 600 MHz), δH: 3.4 (s, 3H,
1-CH3), 4.6-4-8 (m, 3H, 4ꢀ H & 5ꢀ H), 5.15 (s, 2H, N3-CH2), 6.0–6.2 (m, 2H, 2ꢀ H &
3ꢀ H), 6.5–6.6 (d, 1H, 1ꢀ H, J1 , 2 = 4.59 Hz), 7.15–7. 90 (m, 20 H, 4 Ph); MS: m/z =
745 (20%). Anal. calcd. for C39H31N5O11 (745.69), C, 62.82; H, 4.19; N, 9.39. Found:
C, 62.50, H, 4.00; N, 9.30%.
ꢀ
ꢀ
Reduction of 8-nitro-7-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-1,3-substituted
xanthine nucleosides (6a,b): Synthesis of 8-amino-7-(2,3,5-tri-O-benzoyl-β-D
-ribofuranosyl)-1,3-disubstitutedxanthine nucleosides (7a,b)
General procedure
A suspension of 8-nitro-7-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-1,3-disub-
stitutedxanthine nucleosides (6a) or (6b) (0.5 mmol) in H2O (10 ml) was treated at
90°C under stirring with sodium dithionite, Na2S2O4 (0.9 g) by gradual addition.
After stirring 1 h, the solution was cooled overnight. The solid formed was filtered
and dried to give buff-white crystals of product (7a) or (7b), respectively.
7a: Yield, 200 mg (60%); m.p 178°C; TLC [chloroform/ethanol (9:1)]; IR (KBr):
v¯ = 3435, 3121 (NH2), 1715, 1667 (CO) cm−1; 1H NMR (CDCl3, 600 MHz), δH:
3.3 (s, 3H, 1-CH3), 3.4 (s, 3H, 3-CH3), 4.5- 4.7 (m, 3H, 4ꢀ H & 5ꢀ H), 6.0–6.3 ((m,
2H, 2ꢀ H & 3ꢀ H), 6.5 (d, 1H, 1ꢀ H, J1 , 2 = 4.5 Hz), 6.69 (s, 2H, NH2), 7.2–8.1 (m,
15 H, 3 Ph); MS: m/z = 639 (30%). Anal. calcd. for C33H29N5O9 (639.61); C, 61.97;
H, 4.57; N, 10.95. Found: C, 61.70; H, 4.50, N, 10.80%.
ꢀ
ꢀ
7b: Yield, 70 mg (77%); m.p 146°C; TLC [chloroform/ethanol (9:1)]; IR (KBr):
v¯ = 3348, 3446, 3150 (NH2), 1706, 1642 (CO) cm−1 1H NMR (CDCl3, 600 MHz),
δH: 3.3 (s, 3H, 1-CH3), 4.5-4-7 (m, 3H, 4ꢀ H & 5ꢀ H), 5.2 (s, 2H, N-CH2), 6.0–6.3

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
753
((m, 2H, 2ꢀ H & 3ꢀ H), 6.5 (d, 1H, 1ꢀ H, J1 , 2 = 4.5 Hz), 6.7 (s, 2H, NH2), 7.2–8.1 (m,
15 H, 3 Ph); MS: m/z = 715 (15%). Anal. calcd. for C39H33N5O9 (715.71); C, 65.45;
H, 4.65; N, 9.79. Found: C, 65.30; H, 4.40, N, 10.00%.
ꢀ
ꢀ
Deprotection of 8-amino-7-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)-1,3-
disubstitutedxanthine nucleosides (7a,b): Synthesis of 8-amino-7-(β-D-
ribofuranosyl)-1,3-disubstitutedxanthine nucleosides (8a,b)
General procedure
A mixture of compound7a or 7b (1 mmol) in absolute methanol (10 ml) and sodium
methoxide (54 mg, 1 mmol) was stirred at room temperature for 24 h. Evaporation of
the solvent under vacuum gave colorless solid, which was dissolved in hot water and
neutralized with acetic acid. The precipitate formed was filtered and dried to give
8a or 8b, respectively, as pure colorless crystals [TLC (chloroform/ ethyl acetate)
(9:1)].
0
8a: Yield, 170 mg (52%); m.p 227–230°C (lit. m.p. 223–224 C[36]). IR (KBr):
v¯ = 3450 (OH), 3410, 3161 (NH2), 1705, 1645 (CO);1H NMR (DMSO-d6,
600 MHz), δH: 3.0 (s, 3H, 1-CH3), 3.25 (s, 3H, 3-CH3), 3.58 (m, 2H, 5ꢀH), 3.85
(m,1H, 4ꢀ H), 3.98–4.3 (m, 2H, 2ꢀ H & 3ꢀ H), 5.0–5.4 (m, 3H, 5ꢀ-OH, 2ꢀ- & 3ꢀ-OH),
5.8 (d, J = 7.2 Hz, 1H, 1ꢀ-H), 6.8 (s, 2H, NH2, exchangeable by D2O).13C NMR
(DMSO-d6, 150 MHz), δ C: 24.9, 26.7, 63.0, 64.0, 67.45, 69.0, 80.34, 104.4, 138,9,
146.4, 149.0, 152.29; MS: m/z = 327 (41%). Anal. calcd. For C12H17N5O6 (327.29);
C,44.04; H, 5.24; N, 21.40. Found: C, 44.10; H, 5.00, N, 21.10%.
8b:Yield, 200 mg (50%); m.p. 218°C; IR (KBr): v¯ = 3455 (OH), 3405, 3150 (NH2),
1710, 1635 (CO); 1H NMR (DMSO-d6, 600 MHz), δH: 3.1 (s, 3H, 1-CH3), 3.53 (m,
2H, 5ꢀH), 3.83 (m,1H, 4ꢀ H), 3.9–4.3 (m, 2H, 2ꢀ H & 3ꢀ H), 5.0–5.4 (m, 5H, N-CH2,
5ꢀ-OH, 2ꢀ- & 3ꢀ-OH), 5.8 (d, J = 7.2 Hz, 1H, 1ꢀ-H), 6.8 (s, 2H, NH2, exchangeable
by D2O), 7.3–7.5 (s, 5H, Ph);13C NMR (DMSO-d6, 150 MHz), δ C: 24.9, 26.7, 60.5,
63.0, 64.0, 67.45, 69.0, 80.34, 104.4, 138,9, 146.4, 149.0, 152.29 MS: m/z = 403 (20%).
Anal. calcd. for C18H21N5O6 (403.39); C, 53.59; H, 5.25; N, 17.36. Found: C, 53.30;
H, 5.00, N, 17.10%.
Antimicrobial assay
Cultures of two bacterial species namely, Escherichia coli EC, and Staphylococcus
aureus SA as well as well as two fungal species, namely Aspergillus flavus AF, and
Candida albicans CA were used to investigate the antimicrobial activity of twelve
products, namely 4a-c, 5a-c, 7a,b and 8a,b were evaluated for The antimicrobial
activity was assayed biologically using the diffusion plate technique. The latter tech-
nique was carried out by pouring a spore suspension of the fungal species (1cm3 of
sterile water contains approximately 108 conidia) or spreading bacterial suspension
over a solidified malt agar medium. The layer is allowed to set for 30 min. A solution
of the test compounds (1.0 g = cm3) in DMSO was placed onto sterile 5mm filter

754
M. A. N. M. MOHAMED ET AL.
paper discs and allowed to dry, then the discs were placed on the centre of the malt
agar plate and incubated at optimum incubation temperature 28 2°C. The bacte-
ricide Ampicillin and the fungicide Amphotericin B were used as standards under
the same conditions. Measurements were considered after 72 h for fungi and 24 h
for bacteria. The results are summarized in Table.
Funding
The authors thank King Abdulaziz City for Science and Technology (KACST), Kingdom of Saudi
Arabia (KSA) for the financial support under project number AT36-076.
References
[1] Break, L. M.; Mosselhi, M. A. N.; Elshafai, N. M. Nucleosides [8]: Ribosylation
of fused quinazolines: Synthesis of new [1,2,4]triazolo[5,1-b] and [1,2,4] triazino
[3,2-b] quinazoline Nucleosides of fluorescence interest. J. Chemistry. 2013, 2013, 1–11.
doi.org/10.1155/2013/612756.
[2] Watson, J. D.; Crick, F. H. A Structure for Deoxyribose Nucleic Acid. Nature 1953, 71,
737–738.
[3] Liang, C.; Ju, W.; Ding, S.; Sun, H.; Mao, G. Effective Synthesis of Nucleosides Utiliz-
ing O-Acetyl-Glycosyl Chlorides as Glycosyl Donors in the Absence of Catalyst: Mecha-
nism Revision and Application to Silyl-Hilbert-Johnson Reaction. Molecules 2017, 22, 84;
doi: 10.3390/molecules22010084.
[4] Crespan, E.; Garbelli, A.; Amoroso, A.; Maga, G. Exploiting the Nucleotide Substrate Speci-
ficity of Repair DNA Polymerases to Develop Novel Anticancer Agents. Molecules 2011, 16,
7994–8019. doi: 10.3390/molecules16097994
[5] Robak, T.; Korycka, A.; Lech-Maranda, E.; Robak, P. Current Status of Older and New
Purine Nucleoside Analogues in the Treatment of Lymphoproliferative Diseases. Molecules
2009, 14, 1183–1226. doi: 10.3390/molecules14031183
[6] Yu, Q.; Schwidom, D.; Exner, A.; Carlsen, P. Synthesis of Novel Homo-N-Nucleoside
Analogs Composed of a Homo-1,4-Dioxane Sugar Analog and Substituted 1,3,5-Triazine
Base Equivalents. Molecules 2008, 13, 3092–3106. doi: 10.3390/molecules13123092
[7] Yu, Q.; Carlsen, P. Enantioselective Synthesis of Homo-N-Nucleosides Containing a 1,4-
Dioxane Sugar Analog. Molecules 2008, 13, 2962–2974. doi: 10.3390/molecules13122962
[8] Lin, S. -K.; Rosemeyer, H. Perspectives in Nucleoside and Nucleic Acid Chemistry.
Molecules 2001, 6, 1030–1033. doi:10.3390/60300258
[9] Rachakonda, S.; Cartee, L. Challenges in Antimicrobial Drug Discovery and
the Potential of Nucleoside Antibiotics. Curr. Med. Chem. 2004, 11, 775–793.
doi: 10.2174/0929867043455774
[10] Vitali, L. A.; Petrelli, D.; Lambertucci, C.; Prenna, M.; Volpini, R.; Cristalli, G. In vitro
antibacterial activity of different adenosine analogues. J. Med. Microbiol. 2012, 61, 525–528.
doi:10.1099/jmm.0.038174-0
[11] Xavier, N. M.; Schwarz, S.; Vaz, P. D.; Csuk, R.; Rauter, A. P. Synthesis of Purine Nucleosides
from D-Glucuronic Acid Derivatives and Evaluation of Their Cholinesterase-Inhibitory
Activities. Eur. J. Org. Chem. 2014, 2014, 2770–2779. doi: 10.1002/ejoc.201301913
[12] Schwarz, S.; Csuk, R.; Rauter, A. P. Microwave-assisted synthesis of novel purine nucle-
osides as selective cholinesterase inhibitors. Org. Biomol. Chem. 2014, 12, 2446–2456.
doi: 10.1039/C4OB00142G

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
755
[13] Batista, D.; Schwarz, S.; Loesche, A.; Csuk, R.; Costa, P. J.; Oliveira, M. C.; Xavier, N.
M. Synthesis of glucopyranos-60-yl purine and pyrimidine isonucleosides as potential
cholinesterase inhibitors. Access to pyrimidine-linked pseudodisaccharides through Mit-
sunobu reaction. Pure Appl. Chem. 2016, 88, 363–379. doi: https://doi.org/10.1515/pac-
2016-0102
[14] Lin, T. S.; Luo, M. Z.; Liu, M. C.; Pai, S. B.; Dutschman, G. E.; Cheng, Y. C. Synthesis and bio-
logical evaluation of 20,30-dideoxy-L-pyrimidine nucleosides as potential antiviral agents
against human immunodeficiency virus (HIV) and hepatitis B virus (HBV). J. Med. Chem.
1994, 37, 798–803. doi: 10.1021/jm00032a013
[15] Ma, T.; Pai, S. B.; Zhu, Y. L.; Lin, J. S.; Shanmuganathan, K.; Du, J.; Wang, C.; Kim, H.;
Newton, M. G.; Cheng, Y. C. Structure-activity relationships of 1-(2-deoxy-2-fluoro-_-L-
arabino-furanosyl) pyrimidine nucleosides as anti-hepatitis B virus agents. J. Med. Chem.
1996, 39, 2835–2843. doi: 10.1021/jm960098l
[16] Suzich, J.; Tamura, J.; Palmer-Hill, F.; Warrener, P.; Grakoui, A.; Rice, C.; Feinstone, S.; Col-
lett, M. Hepatitis C virus NS3 protein polynucleotide-stimulated nucleoside triphosphatase
and comparison with the related pestivirus and flavivirus enzymes. J. Virol. 1993, 67, 6152–
6158. 0022–538X/93/106152-07$02.00/0
[17] Klumpp, K.; Lévêque, V.; Le Pogam, S.; Ma, H.; Jiang, W. R.; Kang, H.; Granycome, C.;
Singer, M.; Laxton, C.; Hang, J. Q. The novel nucleoside analog R1479 (40-azidocytidine)
is a potent inhibitor of NS5B-dependent RNA synthesis and hepatitis C virus replication in
cell culture. J. Biol. Chem. 2006, 281, 3793–3799. doi: 10.1074/jbc.M510195200
[18] Fyfe, J.; Keller, P.; Furman, P.; Miller, R.; Elion, G. Thymidine kinase from herpes
simplex virus phosphorylates the new antiviral compound, 9-(2-hydroxyethoxymethyl)
guanine. J. Biol. Chem. 1978, 253, 8721–8727. http://www.jbc.org/content/253/24/
8721.citation
[19] Smith, K. O.; Galloway, K. S.; Kennell, W. L.; Ogilvie, K. K.; Radatus, B. K. A new nucleoside
analog, 9-[[2-hydroxy-1-(hydroxymethyl)ethoxyl] methyl] guanine, highly active in vitro
against herpes simplex virus types 1 and 2. Antimicrob. Agents Chemother. 1982, 22, 55–61.
doi: 10.1128/AAC.22.1.55
[20] Vince, R.; Hua, M.; Brownell, J.; Daluge, S.; Lee, F.; Shannon, W. M.; Lavelle, G. C.; Qualls, J.;
Weislow, O. S.; Kiser, R. Potent and selective activity of a new carbocyclic nucleoside analog
(carbovir: NSC 614846) against human immunodeficiency virus in vitro. Biochem. Biophys.
Res. Commun. 1988, 156, 1046–1053. https://doi.org/10.1016/S0006-291X(88)80950-1
[21] Rabkin, C. AIDS and cancer in the era of highly active antiretroviral therapy (HAART). Eur.
J. Cancer 2001, 37, 1316–1319. http://doi.org/10.1016/S0959-8049(01)00104-6
[22] Mallal, S. A.; John, M.; Moore, C. B.; James, I. R.; McKinnon, E. J. Contribution of nucleoside
analogue reverse transcriptase inhibitors to subcutaneous fat wasting in patients with HIV
infection. Aids 2000, 14, 1309–1316. PMID: 10930144
[23] Fredholm, B. B. Methylxanthines; Springer: Berlin/Heidelberg, Germany, 2011; Volume 200.
[24] Monteiro, J. P.; Alves, M. G.; Oliveira, P. F.; Silva, B. M. Structure-bioactivity relationships
of methylxanthines: Trying to make sense of all the promises and the drawbacks. Molecules
2016, 21, 974. doi: 10.3390/molecules21080974
[25] Lutz, M. J.; Held, H. A.; Hottiger, M.; Hubscher, U.; Benner, S. A. Differential discrimina-
tion of DNA polymerases for variants of the non-standard nucleobase pair between xantho-
sine and 2,4-diaminopyrimidine, two components of an expanded genetic alphabet. Nucleic
Acids Res. 1996, 24, 1308–1313. PMCID: PMC145792
[26] Kulikowska, E.; Kierdaszuk, B.; Shugar, D. Xanthine, xanthosine and its nucleotides: solu-
tion structures of neutral and ionic forms, and relevance to substrate properties in vari-
ous enzyme systems and metabolic pathways. Acta Bichimica Polonica. 2004, 51, 493–531.
PMID: 15218545, doi: 035001493

756
M. A. N. M. MOHAMED ET AL.
[27] Mosselhi, M. A. N.; Neidlein, R. Nucleosides 5: Synthesis of Novel 1,2,4-Triazolo [4,3-
b]-1,2,4-triazole Nucleosides. Nucl, Nucl & Nucl. Acids. 2009, 28, 1095–1103. doi:
10.1080/1525777090336837
[28] Metwally, N. H.; Abdalla, M. A.; Mosselhi, M. A. N.; El-Desoky, E. A.: Nucleosides 6, Syn-
thesis and antimicrobial activity of some new N-glycosides of 2-thioxo-4-thiazolidinone
derivatives. Carbohydrate Res. 2010, 345, 1135–1141. doi: 10.1016/j.carres.2010.04.01.
[29] Mosselhi, M. A. N; Break, L. M. Nucleosides 7, Synthesis and structure of new derivatives
of pyrimidine N-nucleosides of potential biological interest. Nucl, Nucl & Nucl. Acids. 2011,
30, 681–695. doi: 10.1080/15257770.2011.59762.
[30] Break, L. M.; Mosselhi, M. A. N; Elshafai, N. M., Nucleosides [8]: Ribosylation of
fused quinazolines: Synthesis of new [1,2,4] triazolo [5, 1- b] and [1, 2, 4] triazino
[3, 2 -b] quinazoline Nucleosides of fluorescence interest. J. Chemistry 2013, 3, 1–11.
doi.org/10.1155/2013/612756
[31] Mosselhi, M. A. N; Darwish, E.; and Peseke, K. Synthesis and antimicrobial activity of new
imidazo- and pyrimido[2,1-f]theophyllines. Monatsh Chem (Chem. Monthly) 2008, 139,
825–834. doi: 10.1007/s00706-008-0854-z
[32] Break, L. M.; Shmiss, N. A. M. M., Mosselhi, M. A. N., Nucleosides 4: Synthesis of some new
S-Nucleoside Derivatives of 2- thioxo(2,4-dithioxo)-5,6,7,8-tetrahydrobenzo-thieno[2,3-
d]pyrimidin- 4-(3H) ones. Phosphorus, Sulfur & Silicon and The Related Elements 2010,
185, 1615–1622. doi: 10.1080/10426500903147159
[33] Mosselhi, M. A. N., Nucleoside 1: Ribosylation of 8-substituted theophylline derivatives.
Nucl, Nucl & Nucl. Acids 1993, 12, 431–439. doi:10.1080/07328319308021213
[34] Mosselhi, M. A. N., Nucleosides 2: Synthesis and Properties of 3,4-Diaryl-4,5-Dihydro-
1-(β-D-ribofuranosyl)-1,2,4-triazole-5-thiones. Nucl, Nucl & Nucl. Acids 1999, 12, 2043–
2049. doi: 10.1080/0732831990804486.
[35] Mosselhi, M. A. N.; Seliger, H., Nucleosides 3: Synthesis of Novel 1,3,4- Oxadiazole Nucle-
osides. J. Chem. Res.(S), 2001, 359–361. doi: https://doi.org/10.3184/030823401103170278
[36] Kramer, G. L.; Garst, J. E.; Mitchel, S. S.; Wells, J. N. Selective inhibition of cyclic nucleotide
phosphodiesterases by analogs of 1-methyl -3-isobutylxanthine. Biochemistry 1977, 16,
3316–3321. doi: 10.1021/bi00634a006
[37] Vorbruggen, H.; Krolikiewicz, K.; Bennua, B. Nucleoside syntheses, XXII: Nucleoside syn-
thesis with trimethylsilyl triflate and perchlorate as catalysts. Chem. Ber. 1981, 114, 1234–
1255. doi: 10.1002/cber.19811140404
[38] (a) Van Galen, P. J.; ljzerman, A. P.; Soudijn, W. Xanthine -7-Ribosides as Adenosine Recep-
tor Antagonists: Further Evidence for Adenosine’s Anti Mode of Binding. Nucl, Nucl & Nucl.
Acids 1990, 9, 275–291. doi:10.1080/07328319008045138 (b) Ozola, V.; Ramzaeva, N.; Mau-
rinsh, Y.; Lidaks, M. Synthesis of 8-substituted theophylline β;-D-ribofuranosides. Nucl,
Nucl & Nucl. Acids 1993, 12, 827–839. doi: 10.1080/07328319308018553.
[39] Hutzenlaub, W.; Pfeiderer, W. Simplified syntheses of 7-methyl- and 1,7-Dimethyl xanthine.
Liebigs Ann. Chem. 1979, 1847–1854. doi: 10.1002/jlac.197919791122
[40] Pfaller, M. A.; Burmeister, L.; Bartlett, M. A.; Rinaldi, Multicenter evaluation of four meth-
ods of yeast inoulum preparation. J. Clin. Microbiol. 1988, 26, 1437–1441. doi: PMC266638
[41] Matar, M. J.; Ostrosky-Zeichner, L.; Paetznick, V. L.; Rodriguez, J. R.; Chen, E.; Rex, J. H.
Correlation between E-test, disk diffusion and microdilution methods for antifungal sus-
ceptibility testing of fluconazole and voriconazole. Antimicrob. Agents Chemother 2003, 47,
1647–1651. doi: PMC153338