O-Aryl α,β-d-ribofuranosides: Synthesis & highly efficient biocatalytic separation of anomers and evaluation of their Src kinase inhibitory activity

Article abstract of DOI:10.1016/j.bmc.2012.09.057

A series of peracetylated O-aryl α,β-d-ribofuranosides have been synthesized and an efficient biocatalytic methodology has been developed for the separation of their anomers which was otherwise almost impossible by column chromatographic or other techniques. The incubation of 2,3,5-tri-O-acetyl-1-O- aryl-α,β-d-ribofuranoside with Lipozyme TL IM immobilized on silica led to the selective deacetylation of only one acetoxy group, viz the C-5′-O-acetoxy group of the α-anomer over the other acetoxy groups derived from the two secondary hydroxyl groups present in the molecule and also over three acetoxy groups (derived from one primary and two secondary hydroxyls of the β-anomer). This methodology led to the easy synthesis of both, α- and β-anomers of O-aryl d-ribofuranosides. All the arylribofuranosides were screened for inhibition of Src kinase. 1-O-(3-Methoxyphenyl)-β-d-ribofuranoside exhibited the highest activity for inhibition of Src kinase (IC₅₀ = 95.0 μM).

Full text of DOI:10.1016/j.bmc.2012.09.057

Bioorganic & Medicinal Chemistry 20 (2012) 6821–6830
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
O-Aryl
a
,b-D-ribofuranosides: Synthesis & highly efficient biocatalytic
separation of anomers and evaluation of their Src kinase inhibitory activity
Raman K. Sharma a, Sukhdev Singh a, Rakesh Tiwari b, Deendayal Mandal b, Carl E. Olsen c,
a,
Virinder S. Parmar a, Keykavous Parang b, , Ashok K. Prasad
⇑
⇑
a Bioorganic Laboratory, Department of Chemistry, University of Delhi, Delhi 110 007, India
b Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, University of Rhode Island, 41 Lower College Road, Kingston, RI 02881, USA
c University of Copenhagen, Faculty of Life Sciences, Department of Natural Sciences, DK-1871 Frederiksberg C, Denmark
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 10 July 2012
Revised 26 September 2012
Accepted 27 September 2012
Available online 4 October 2012
A series of peracetylated O-aryl a,b-D-ribofuranosides have been synthesized and an efficient biocatalytic
methodology has been developed for the separation of their anomers which was otherwise almost
impossible by column chromatographic or other techniques. The incubation of 2,3,5-tri-O-acetyl-1-O-
aryl-
a,b-D
-ribofuranoside with LipozymeÒ TL IM immobilized on silica led to the selective deacetylation
of only one acetoxy group, viz the C-50-O-acetoxy group of the
a
-anomer over the other acetoxy groups
derived from the two secondary hydroxyl groups present in the molecule and also over three acetoxy
groups (derived from one primary and two secondary hydroxyls of the b-anomer). This methodology led
Keywords:
LipozymeÒ TL IM
to the easy synthesis of both,
were screened for inhibition of Src kinase. 1-O-(3-Methoxyphenyl)-b-
highest activity for inhibition of Src kinase (IC50 = 95.0 M).
a
- and b-anomers of O-aryl
D
-ribofuranosides. All the arylribofuranosides
Regio- and stereoselective deacetylation
Anomers
O-Aryl ribofuranosides
Anticancer activity
D-ribofuranoside exhibited the
l
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
essential for various physiological and pathogenic processes. These
glycans are formed by the action of carbohydrate-processing en-
zymes, such as glycosidases and glycosyltransferases, which
assemble and trim carbohydrates to produce bioactive glycans or
glycoconjugates.6 Glycosidases can be classified into a number of
subfamilies on the basis of structural similarity.7 Further, inhibi-
tors of glycosidases can be used as therapeutic agents for the treat-
ment of viral infections, diabetes and cancer.8 Because glycans
formed by the action of glycosidases are involved in a variety of
biological processes and exoglycosidases are frequently used as
tools for structural analysis of glycans, characterization of catalytic
activities of these glycosidases is of considerable importance.
One of the recent applications of O-arylribofuranosides is in the
detection assay of nucleoside hydrolases or nucleoside phospho-
rylases in microbial parasites, which have adverse effects on
human health and animal population. The O-arylribofuranosides
are used as chromogenic substrates, which on reaction with nucle-
oside hydrolases or nucleoside phosphorylases release phenolic
chromophore that can be detected spectrophotometrically and
thus provides an easy diagnostic method for the presence of en-
Acylated and partially acylated carbohydrates are key intermedi-
ates in the preparation of oligosaccharides, glycopeptides and mod-
ified nucleosides;1 in particular, sugar monoesters are important as
biodegradable surfactants.2 Moreover, modified nucleosides have
been found to be useful therapeutic agents in the treatment of
different diseases, such as viral diseases.3 The majority of these
nucleosides are modified natural b-analogues or oligonucleotides
assembled from b-nucleosides. On the contrary, the application of
unnatural
a-nucleosides as therapeutic agents has been limited
due to difficulty in their synthesis. Despite these limitations,
a
-nucleosides continueto be the subject of extreme interest because
of their unique properties in some specific applications.4
O-Glycosides have been used as antibiotic, antitumor,
antifungal, antihypertensive, antiviral and antidiabetic agents.5
Furthermore, they find applications as substrates for determining
the activity of glycosidases, a large subgroup of carbohydrate-
processing enzymes that hydrolytically cleave the glycosidic bond
within oligo- or polysaccharides or between a glycan and a non-
glycan moiety. Oligo/polysaccharides and glycoconjugates are
zymes.9 The O-aryl b-
D-ribofuranosides have been found to serve
as substrates for these enzymes; however most of the synthetic
methodologies reported for the preparation of these compounds
⇑
Corresponding authors. Tel.: +1 401 874 4471; fax: +1 401 874 5787 (K.P.);
tel.: +91 11 27662486 (A.K.P.).
lead to the formation of mixtures of
separation of O-aryl ,b- -ribofuranosides is almost impossible
by conventional chromatographic methods. In this article, we
a,b-anomers. The anomeric
a
D
E-mail addresses: kparang@uri.edu (K. Parang), ashokenzyme@yahoo.com
(A.K. Prasad).
0968-0896/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.bmc.2012.09.057

6822
R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
report the synthesis of O-aryl
efficient lipase-based separation of the
a
,b-
D
-ribofuranosides and a highly
- and b-anomers using
whether these compounds can be used as alternative scaffolds for
designing Src kinase inhibitors.
a
one of the acetoxy functions of peracetylated O-aryl
a-D-ribofur-
anoside as handle.
2. Results and discussion
2.1. Chemistry
Protein tyrosine kinases (PTKs) are enzymes responsible for the
phosphorylation of other proteins and can catalyze the transfer of
c-phosphate group of ATP to the protein phenolic groups (on Tyr).
PTKs play a central role in signal transduction pathways and are in-
volved in immune, endocrine, and nervous system physiology and
pathology. On the other hand, the abnormal phosphorylation by
the PTKs is believed to be important in the development of many
types of cancers.10–12 Src kinase is a member of a structurally
homologous group of non-receptor PTKs present in the cytoplasm,
known as the ‘Src family of kinases’.13 The Src family of PTKs is di-
vided into nine subfamilies, Src, Yes, Fyn, Frg, Lck, Lyn, Hck, Blk and
Frk based on catalytic domain sequence. Src kinases play crucial
roles in signal transduction pathways and regulating various cellu-
lar functions such as cell proliferation and cell differentiation.14 Src
kinase is a proto-oncogenic tyrosine kinase15 and has been impli-
cated in the genesis and progression of multiple types of human
cancer including colon, breast, lung and other cancers.16
The small-molecule inhibitors of this protein are under investiga-
tion as potential agents for the treatment of a variety of diseases.17,18
It is proposed that inhibitors of Src phosphorylation may impede
uncontrolled tumor cell growth, and thus function as novel
therapeutic agents for cancer. Specifically, Src activity is elevated
in breast, pancreatic, ovarian, esophageal, lung, gastric, colon, and
head-and-neck cancers.19–23 A number of planar heteroaromatic
small-molecule inhibitor templates have been exploited to identify
novel Src kinase inhibitors. To date, purine, pyrrolopyrimidine, pyr-
idopyrimidine, naphthyridone, quinazoline and quinoline-based
inhibitors have been reported.24–27 Most of these compounds are
ATP-binding site inhibitors. These N-heteroaromatics lack the car-
bohydrates and triphosphate groups (ribo-phosphate) present in
the ATP. Unfortunately, attempts to improve the biological profile
of the latter compounds have so far met with little success. Thus,
there is opportunity to identify other small-molecule inhibitors,
pharmacophore fragments, or scaffolds that can inhibit Src kinase
domain through interaction with ATP-binding site. X-ray studies
have revealed a deep, hydrophobic binding pocket near the ATP
binding site.24b O-Arylribofuranosides have a carbohydrate moiety
and an aryl group that can mimic ribose and adenine portions of
ATP, respectively, in binding to PTKs. Furthermore, these com-
pounds contain aromatic hydrophobic residues that may generate
hydrophobic interactions within the hydrophobic pocket of Src
ATP binding site. Thus, we screened O-arylribofuranosides for their
potential inhibitory potency against Src kinase to determine
The tetra-O-acetylated-
zymatically synthesized in two steps from
yields.28 The coupling of 1,2,3,5-tetra-O-acetyl-
a
,b-
D
-ribofuranosides 3 were chemoen-
-ribose in quantitative
,b- -ribofurano-
D
a
D
sides (3) with different phenols 4a–h was accomplished according
to the modified literature procedure29 using SnCl4 in acetonitrile at
ꢀ10 °C to afford a mixture of the corresponding peracetylated O-
aryl
a,b-D-ribofuranosides (5a & 6a, 5b & 6b, 5c & 6c, 5d & 6d,
5e & 6e, 5f & 6f, 5g & 6g and 5h & 6h) in different proportions in
64–75% yields (Scheme 1).
All attempts to separate
a- and b-anomers from anomeric mix-
tures of O-aryl- -ribofuranosides 5a & 6a, 5b & 6b, 5c & 6c, 5d &
D
6d, 5e & 6e, 5f & 6f, 5g & 6g and 5h & 6h by column chromatogra-
phy failed, possibly because of the similar nature and almost iden-
tical polarity of the two isomers. This led us to explore the
possibility of separation of the two anomers by selective deacety-
lation of acetoxy functions of one of the anomers using lipase-
mediated deacetylation reaction.30
Recently, Chien and Chern31 and Fernandez-Lorente et al.32a have
used native Candida rugosa lipase (CRL, Sigma), CRL immobilised on
octyl agarose, respectively, to catalyze regioselective deacetylation
at C-5 position of 1,2,3,5-tetra-O-acetyl-b-
D-ribofuranose to afford
1,2,3-tri-O-acetyl-b- -ribofuranose in 80% and 47% yields in
D
phosphate buffer-DMF and phosphate buffer, respectively. Inigo
et al.32b have studied Candida antarctica lipase B catalyzed deacety-
lation of 1-O-methyl-2,3,5-tri-O-acetyl-
1-O-methyl-2,3,5-tri-O-acetyl-b- -ribofuranoside, separately and
observed regioselective deacetylation in the former compound to
a-ribofuranoside and
D
afford 2,3-di-O-acetyl-a-D-ribofuranoside in 81% yield; selectivity
was not observed in b-diastereoisomer. Wengel co workers33a have
used wheat germ lipase in phosphate buffer for the separation of
a
,b-anomers of thymidine, albeit in low yields. There is only one
report of use of Pseudomonas cepacia lipase in organic solvent by Fer-
rero and Gotor33b for the separation of
,b-anomers of thymidine
a
derivatives from an industrial waste stream. Moreover, Gotor co
workers33c recently reported the concept of regioselective enzy-
matic acylation or hydrolysis process for the separtion of anomers
of
a,b-D-nucleosides. To the best of our knowledge, it is the first
report on the biocatalytic separation of anomeric mixtures of
O-arylglycosides.
AcO
AcO
AcO
O
O
O
O-R
OH
OAc
(iii)
(ii)
(i)
D-Ribose
R-OH (4a-h)
1
OAc OAc
OH OH
OAc OAc
Reaction time = 35-80 min
yield = 64-75 %
2
3
5a-h ( -anomer)
α
(α+β−anomers)
6a-h (β-anomer)
Reagents and conditions: (i) vinyl acetate, CAL-B, THF, 55 oC; (ii) Ac2O, pyridine, 28-30 oC;
(iii) R-OH, SnCl4, CH3CN, -10 o
C
g
h
Compds. 4-6
a
b
d
f
c
e
R
OMe
CH3
OMe
OH
CH3
Scheme 1. Synthesis of ab-O-arylnucleosides.

R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
6823
O
R
O
R
HO
AcO
O
O
6a-h and 7a-h
separately
AcO
O
O-R
Lipozyme TL IM
OH OH
8a-h (β-anomer)
OAc OAc
6a-h (β-anomer)
treated with
Sat. MeOH-NH3
28-30 o
C
DIPE, n-butanol
+
OAc OAc
5a-h (α-anomer)
+
40-42 o
C
HO
HO
O
O
6a-h ( -anomer)
β
O
R
O
R
OH OH
OAc OAc
9a-h ( -anomer)
7a-h ( -anomer)
α
α
Compds.
5 - 9
g
h
a
b
c
d
e
f
R
OMe
CH3
OMe
OH
CH3
Scheme 2. Lipase-catalyzed deacylation reaction: separation of anomeric mixtures.
with time and led to the formation of a mixture of compounds.
CRL and CAL-L(A) did not show any appreciable selectivity in
the deacetylation studies on anomeric mixture of O-aryl
Table 1
LipozymeÒ TL IM-catalyzed regio- and chemo selective deacetylation studies on
mixture of ab-anomers of peracetylated ribofuranosides in DIPE at 40–42 °C
D
-ribofuranosides.
In a typical reaction, the anomeric mixture of O-aryl-D-ribofur-
Anomeric
mixturesa
Ratio of
:b
anomers
Reaction
time (h)
Deacetylated and
recovered, unreacted
ribofuranosides
Yieldb
(isolated %)
a
anosides 5a and 6a (0.5 g, 1.36 mmol) was dissolved in DIPE
(20 mL) and incubated with LipozymeÒ TL IM (substrate-enzyme
ratio, 1:0.5, w/w) and n-butanol (0.05 mL) at 40–42 °C. The pro-
gress of the reaction was monitored on TLC. On completion of
the reaction, enzyme was filtered off and the solvent was removed
under reduced pressure. The residue was purified by column
chromatography to afford the deacetylated 2,3-di-O-acetyl-1-O-
5a & 6a
5b & 6b
5c & 6c
5d & 6d
5e & 6e
5f & 6f
1.0:0.9
12.5
10.0
11.5
10.5
12.0
14.0
11.5
48.0
7a
6a
95
98
1.0:3.8
1.0:3.3
1.0:4.1
1.0:3.6
1.0:8.8
1.0:3.2
1.0:2.9
7b
6b
87
95
7c
6c
95
97
(1-naphthyl)-
a-D-ribofuranoside (7a) in 95% yield together with
7d
6d
94
93
the unreacted, recovered 2,3,5-tri-O-acetyl-1-O-(1-naphthyl)-b-
D-ribofuranoside (6a) in 98% yield (Scheme 2, Table 1).
7e
6e
91
94
Similarly lipase-catalyzed deacetylation of mixtures of O-aryl
,b-D-ribofuranosides 5b & 6b, 5c & 6c, 5d & 6d, 5e & 6e, 5f & 6f,
a
7f
6f
89
93
5g & 6g and 5h & 6h led to the formation of deacetylated compounds
7b–h in high yields, along with the unreacted peracetylated
5g & 6g
5h & 6h
7g
6g
93
91
O-aryl-b-
cases the lipase selectively deacetylated the acetoxy function
involving primary hydroxyl group of minor -anomer of O-aryl
,b- -ribofuranosides, except in the case of 2,3,5-tri-O-acetyl-1-O-
(1-naphthyl)- ,b- -ribofuranosides (5a and 6a), where the amount
D-ribofuranosides 6b–h. It is interesting to note that in all
7h
6h
91
92
a
a
D
a
All these reactions did not yield any product when performed in the absence of
LipozymeÒ TL IM.
a
D
b
of the anomers in the mixture is almost same (Table 1). Complete
deacetylation of the enzymatically produced partially deacetylated
The yields reported are calculated by taking a- and b-anomers in the mixture as
100%.
O-aryl-
ylated O-aryl-b-
ammonia afforded O-aryl-
b- -ribofuranosides 8a–h in quantative yields (Scheme 2).
a
-
D
-ribofuranosides 7a–h and recovered, unreacted peracet-
-ribofuranosides 6a–h with saturated methanolic
-ribofuranosides 9a–h and O-aryl-
D
a-D
In our present work, four lipases, that is, Candida rugosa lipase
(CRL), Candida antarctica lipase-B immobilized on accurel [CAL-
L(A)], Candida antarctica lipase-B immobilized on polyacrylate
(Lewatit, CAL-B or Novozyme-435) and Thermomyces lanuginosus
lipase immobilized on silica (LipozymeÒ TL IM) were screened
for the regioselective deacetylation of acetoxy function of one ano-
mer over the other in different organic solvents, that is, THF, diox-
ane, acetonitrile, toluene, ethanol and diisopropyl ether (DIPE) at
different temperatures. It was observed that LipozymeÒ TL IM in
DIPE at 40–42 °C selectively and most efficiently deacetylates the
acetoxy moiety derived from the C-50 hydroxyl group of only the
D
2.2. Src kinase inhibitory activity
Synthesized b- and -O-arylribofuranosides 8a–h and 9a–h
a
were evaluated as Src kinase inhibitors. The results of Src kinase
inhibitory activity of these compounds are shown in Table 2. In
general the compounds showed weak to modest inhibitory
potency against Src kinase. Among all the compounds, 1-O-(3-
methoxyphenyl)-b-
exhibited an IC50 value of 95.0
D
-ribofuranoside 8f is the most active and
M. All other derivatives showed
l
a
-anomer over the other acetoxy moieties of O-aryl-
ribofuranosides. Although CAL-B, initially showed selectivity for
the deacetylation of C-50 acetoxy group of
-anomer, it started
deacetylation of acetoxy functional groups of the b-anomer as well
a,b-D-
weak Src kinase inhibition with IC50 values more than 100 lM.
Reported heteroaromatic compounds as Src kinase inhibitors24a
contain functional groups at appropriate positions for the hydrogen
a

6824
R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
H
bonding interactions with specific amino acid residues of Src
ATP-binding site.24b It appears that these critical bonding interac-
tions are not compensated by the presence of hydrophobic aro-
matic rings present in these compounds and/or the hydrophobic
interactions of the aromatic group with the hydrophobic pocket
of Src ATP binding site are modest. As expected the carbohydrate
moiety did not provide any additional improvement in the activity
of the compounds. The major interactions of ATP with the ATP-
binding site are generated through the adenine base contributions.
N
O
N
Cl
NH2
N
N
N
NH2
N
N
O
P
O
P
O
P
N
N
H
N
-O
O
O
O
N
O
H
N
O-
O-
O-
H3CO
OH OH
NHCH3
AMP-PNP
PP2
Staurosporine
In most cases a-anomers were less active than the corresponding
Figure 1. Chemical structure of Staurosporine, PP2 and AMP-PNP.
b-anomer. This is not surprising as ATP has a b-configuration, and
b-anomers can mimic the ATP core more efficiently. It is obvious that
further optimization of b-anomers with incorporation of appropriate
heteroaromatic groups capable of hydrogen bonding interactions is
required to generate more potent Src kinase inhibitors. Crystal struc-
ture of c-Src with a nonhydrolyzable ATP analog, AMP-PNP (Adeno-
In conclusion, a highly efficient regio- and stereoselective deacet-
ylation of 2,3,5-tri-O-acetyl-1-O-aryl-a,b-D-ribofuranosides was
achieved by using LipozymeÒ TL IM immobilized on silica.
Enzymatic deacetylation removed the acetyl moiety from the C-50
acetoxy group of
function of the b-anomer and the two acetoxy moieties present at
the C-20 and C-30 position of each of the
- and b-anomers of 2,3,5-
tri-O-acetyl-1-O-aryl- -ribofuranosides. This methodology enabled
a
-anomer versus the corresponding C-50 acetoxy
sine 50-[b,
c-imido]triphosphate, Fig. 1), showed critical hydrogen
bonding between the 4-amino group of adenine and Glu339.34 Simi-
larly, X-ray studies of Src kinases with phenylpyrazolopyrimidines,35
which resemble the purine core of ATP, have revealed that the 4-ami-
no group of the heteroaromatic group is hydrogen bonded to the side
chain of Thr338 as well as the carbonyl of Glu339. This hydrogen
bonding interactions contribute significantly to the potency of
phenylpyrazolopyrimidines as Src kinase inhibitors.
a
D
us to separate the anomeric mixtures of O-arylribofuranosides,
which were impossible to separate by normal chromatographic
techniques. In this process, simultaneous synthesis of both the
anomers, that is, natural b- and unnatural
a-anomers of O-aryl
D
-ribofuranosides was achieved. The enzymatic methodology devel-
oped herein may find wide applications in the separation of anomer-
ic mixtures of O-aryl glycosides, sugars, or nucleosides for the
research groups working in these areas. The synthesized compounds
were evaluated for the Src kinase inhibitory potency and were found
to be weak or modest inhibitors. The data indicate that designing
small molecules with modest inhibitory activity against Src kinase
Molecular modeling was utilized to examine how compounds
8c and 8f with modest inhibitory activities (IC50 = 95–125 lM)
would fit within the ATP-binding site of the enzyme when com-
pared with AMP-PNP (Fig. 2). The modeling studies indicated that
the orientation of aromatic groups in 8c and 8f is towards the
hydrophobic binding pocket versus that of adenine group in
AMP-PNP is slightly different (Fig 2a and b). While compound 8f
has an oxygen in methoxy group that may play a role as hydrogen
bond acceptor, the aromatic group in 8c is only capable of hydro-
phobic interactions deep in the hydrophobic binging pocket of
ATP-binding site and does not have any heteroatom in aryl of aryl-
ribofuranosides for generating hydrogen bonding ( Fig. 2b). The
compounds demonstrated only modest inhibitory potency possibly
because of mostly hydrophobic interactions and the absence of
hydrogen bonding between the base of the arylribofuranosides
and the ATP-binding site.
is possible by using b-anomer of O-aryl-D-ribofuranosides. The
compounds may have potential to be used in fragment-based
discovery of Src kinase inhibitors. Further optimization by incorpo-
rating essential functional groups on the aromatic rings may be
required to generate lead compounds with optimal Src inhibitory
potency.
Table 2
IC50 values of b- and a-O-arylribofuranosides as Src kinase inhibitors
Compounds
IC50 (l
M)c
Staurosporinea
0.3 0.0
2.8 0.0
1370.7
184.7
224.8
297.3
125.0
NAd
PP2b
8a
9a
8b
9b
8c
9c
8d
9d
8e
9e
8f
NDe
451.0
143.4
ND
95.0
9f
NA
8g
9g
8h
9h
483.9
NA
272.1
NA
a
Structure given in Figure 1.
1-(tert-Butyl)-3-(4-chlorophenyl)-1H-pyrazolo[3,4-d]pyrimidin-4-amine
b
(structure given in Fig. 1).
Figure 2. Comparison of structural complexes of Src kinase with different O-aryl b-
c
The concentration of the compound that inhibited enzyme activity by 50%.
No enzyme inhibitory activity was observed up to the concentration of 100
Not determined.
D-ribofuranosides. (a) 8f (green) and AMP-PNP (blue); (b) 8c (yellow) and AMP-PNP
d
lM.
(blue) based on molecular modeling. The compounds are rendered in stick styles.
They are the lowest energy conformers predicted for the compounds.
e

R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
6825
& 6g and 5h & 6h (1.5 mmol) was dissolved in diisopropyl ether
(25 mL) and incubated with LipozymeÒ TL IM (0.23–0.32 g, sub-
strate-enzyme ratio, approximately 1:0.5, w/w) and n-butanol
(0.05 mL) at 40–42 °C (Scheme 2). The progress of the reaction
was monitored by TLC.37 On completion, the reaction was stopped
by filtering off the enzyme and solvent evaporated to dryness un-
der reduced pressure to obtain the crude product. The crude prod-
uct thus obtained was purified by column chromatography to
afford the unreacted, recovered b-anomers 6a–h and the 50-O-
deacetylated compounds 7a–h in 91–98% and 87–95% yields,
respectively. All the unreacted, recovered peracetylated 1-O-aryl-
3. Experimental section
Melting points were determined on a Mettler FP 62 instrument or
in a sulfuric acid bath and are uncorrected. The IR spectra were re-
corded on a Perkin-Elmer model 2000 FT-IR spectrometer by making
KBr disc for solid samples and thin film for oils. The 1H and 13C NMR
spectra were recorded on a Bruker AC-300 Avance spectrometer at
300 and 75.5 MHz, respectively, using TMS as internal standard.
The chemical shift values are on d scale and the coupling constants
(J) are in Hz. Signals from OH groups in 1H NMR spectra recorded
in CDCl3 were verified by removing them by shaking the solution
with D2O. HR-ESI-TOF-MS analyses were carried out on a micro-
TOF-Q instrument from Bruker Daltonics, Bremen. Thermomyces
lanuginosus lipase immobilized on silica (LipozymeÒ TL IM), Candida
antarctica lipase B immobilized on accurel [CAL-L(A)] and Candida
antarctica lipase B immobilized on polyacrylate (lewatite, CAL-B or
Novozyme-435) were provided by Novozymes Inc. (Copenhagen,
Denmark), whereas Candida rugosa lipase (CRL) was purchased from
Sigma Chemical Co. (USA). All enzymes were used after storing in
vacuum over P2O5 for more than 24 h. Acetonitrile and diisopropyl
ether were distilled and kept over molecular sieves (4 Å) prior to
use. Analytical TLCs were performed on precoated Merck silica-gel
60F254 plates; the spots were detected either under UV light or by
charring with 4% alcoholic H2SO4. Silica gel (100–200 mesh) was
used for column chromatography.
b-
D-ribofuranosides 6a–h and enzymatically deacetylated 2,3-di-
O-acetyl-1-O-aryl-
a
-D
-ribofuranoside 7a–h were unambiguously
identified on the basis of their spectral data; the structure of the
known compound 6a was further confirmed on the basis of com-
parison of its spectral data with that reported in the literature.38
The details of the LipozymeÒ TL IM-catalyzed deacetylation reac-
tion are given in Table 1. All these reactions did not yield any prod-
uct when performed in the absence of LipozymeÒ TL IM.
3.2.1. 2,3,5-Tri-O-acetyl-1-O-(1-naphthyl)-b-D-ribofuranosides
(6a)
It was obtained as semisolid (0.28 g) in 98% yield. Rf = 0.82 (30%
ethyl acetate in petroleum ether, v/v); ½a D31
= ꢀ0.56° (c 0.25,
ꢂ
MeOH); IR (Nujol) mmax: 1746, 1577, 1402, 1238, 1093, 1021 and
779 cmꢀ1 1H NMR (300 MHz, CDCl3): d 1.74, 2.12 and 2.17 (9H,
;
3.1. General procedure for the synthesis of peracetylated 1-O-
aryl a,b-D-ribofuranosides (5a–h and 6a–h, Scheme 1)
3s, 3H each, 3 ꢁ COCH3), 4.06–4.09 (1H, m, C-5H ), 4.44–4.48
a
(2H, m, C-4H and C-5Hb), 5.66–5.70 (2H, m, C-2H and C-3H), 5.84
(1H, s, C-1H), 7.08–7.10, 7.34–7.39, 7.50–7.52, 7.79 and 8.18 (7H;
1H, m; 1H, m; 3H, m; 1H, br s and 1H, br s; aromatic protons);
13C NMR (75.5 MHz, CDCl3): d 20.80 and 21.01 (3 ꢁ COCH3),
63.66 (C-5), 71.52 (C-3), 75.52 (C-2), 79.74 (C-4), 103.80 (C-1),
108.88, 122.18, 122.59, 126.10, 126.92, 127.97, 134.90 and
152.16 (aromatic carbons), and 170.04 (3 ꢁ CO); HR-ESI-TOF-MS:
m/z 425.1214 ([M+Na]+), calcd for [C21H22O8+Na]+ 425.1207.
1,2,3,5-Tetra-O-acetylribofuranose 3 was chemoenzymatically
synthesized from
-ribose (1) in two steps in quantitative yields.28
D
Compound 3 (2.0 mmol) and the corresponding phenol (4a–h,
2.0 mmol) were mixed in dry acetonitrile (10 mL) and stirred under
nitrogen atmosphere at ꢀ10 °C. After 10 min, tin (IV) chloride (1 M
solution in DCM, 2.0 mmol) was added dropwise to the above solu-
tion under stirring. The progress of the reaction was monitored by
TLC. On completion, the reaction was stopped by pouring the reac-
tion mixture into bicarbonate solution. The reaction mixture was
passed through celite and the celite was thoroughly washed with
chloroform (3 ꢁ 50 mL). The chloroform solution was then washed
with water, dried and concentrated to afford the crude products as
viscous oils, which were purified by column chromatography to
3.3. 2,3,5-Tri-O-acetyl-1-O-(2-naphthyl)-b-D-ribofuranoside (6b)
It was obtained as crystalline solid (0.45 g) in 95% yield.
Rf = 0.78 (30% ethyl acetate in petroleum ether, v/v); mp 111–
112 °C; ½a 3D1
ꢂ
= ꢀ1.72° (c 0.25, MeOH); IR (Nujol)
mmax: 1743,
1599, 1371, 1245, 1047 and 779 cmꢀ1
;
1H NMR (300 MHz, CDCl3):
get the anomeric mixtures of the peracetylated 1-O-aryl a,b-D-ribo-
d 1.92, 2.11 and 2.17 (9H, 3s, 3H each, 3 ꢁ COCH3), 4.07–4.09 (1H,
furanosides (5a & 6a, 5b & 6b, 5c & 6c, 5d & 6d, 5e & 6e, 5f & 6f, 5g &
6g and 5h & 6h) in 64–75% yields by using ethyl acetate and petro-
leum ether as eluent (Scheme 1). The anomeric mixtures of 1-O-aryl
m, C-5H ), 4.41–4.46 (2H, m, C-4H and C-5Hb), 5.57–5.59 (2H, m,
a
C-2H and C-3H), 5.80 (1H, s, C-1H), 7.16–7.19, 7.37–7.40, 7.43–
7.45 and 7.73–7.79 (7H; 1H, m; 2H, m; 1H, m and 3H, m; aromatic
protons); 13C NMR (75.5 MHz, DMSO-d6): d 19.37 (3 ꢁ COCH3),
62.32 (C-5), 69.98 (C-3), 73.85 (C-2), 78.10 (C-4), 102.11 (C-1),
111.73, 117.50, 123.13, 125.26, 125.95, 126.41, 128.36, 128.53,
133.02 and 152.70 (aromatic carbons), and 168.35 & 169.32
(3 ꢁ CO); HR-ESI-TOF-MS: m/z 425.1213 ([M+Na]+), calcd for
[C21H22O8+Na]+ 425.1207.
D
-ribofuranosides were unambiguously identified on the basis of
their spectral data analysis and by comparison of chemical shift val-
ues of anomeric protons of - and b-anomers in the mixture with
those reported for pure 1-O-phenyl- -ribofuranoside and
1-O-phenyl-b-
-ribofuranoside.31,36 The ratio of anomers in the
a
a
-D
D
mixtures 5a & 6a, 5b & 6b, 5c & 6c, 5d & 6d, 5e & 6e, 5f & 6f, 5g &
6g and 5h & 6h were calculated based on the integration of corre-
sponding anomeric proton in the 1H NMR spectrum of the mixture
(Table 1). The spectral data of the anomeric mixtures are not given
here, instead spectral data of enzymatically deacetylated O-arylri-
bofuranosides (7a–h) and unreacted, recovered O-arylribofurano-
sides (6a–h) isolated on incubation of anomeric mixtures with
LipozymeÒ TL IM are given in the following section.
3.3.1. 2,3,5-Tri-O-acetyl-1-O-(4-biphenyl)-b-D-ribofuranoside
(6c)
It was obtained as semisolid (0.48 g) in 97% yield. Rf = 0.92 (30%
ethyl acetate in petroleum ether, v/v); ½a D31
= ꢀ1.56° (c 0.25,
ꢂ
MeOH); IR (Nujol)
mmax: 1747, 1604, 1375, 1237, 1045 and
760 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 1.96, 2.10 and 2.15
;
3.2. General procedure for the LipozymeÒ TL IM-catalyzed
deacetylation of peracetylated 1-O-aryl-
(5a–6a, 5b–6b, 5c–6c, 5d–6d, 5e–6e, 5f–6f, 5g–6g and 5h–6h)
(9H, 3s, 3H each, 3 ꢁ COCH3), 4.07–4.11 1H, m, C-5H , 4.43–4.47
a
a
,b-
D
-ribofuranosides
(2H, m, C-4H and C-5Hb), 5.51–5.55 (2H, m, C-2H and C-3H), 5.69
(1H, s, C-1H), 7.06–7.09, 7.31–7.33, 7.39–7.44 and 7.50–7.55 (9H;
2H, m; 1H, m; 2H, m and 4H, m; aromatic protons); 13C NMR
(75.5 MHz, CDCl3): d 20.91 and 20.96 (3 ꢁ COCH3), 63.90 (C-5),
71.58 (C-3), 75.44 (C-2), 79.69 (C-4), 103.76 (C-1), 117.10,
The anomeric mixture of peracetylated 1-O-aryl
anoside 5a & 6a, 5b & 6b, 5c & 6c, 5d & 6d, 5e & 6e, 5f & 6f, 5g
a,b-D-ribofur-

6826
R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
127.22, 127.32, 128.61, 129.13, 136.04, 140.95 and 156.09 (aro-
matic carbons), and 170.00, 170.09 & 170.95 (3 ꢁ CO); HR-ESI-
TOF-MS: m/z 451.1358 ([M+Na]+), calcd for [C23H24O8+Na]+
451.1363.
carbons), and 169.95, 170.08 & 170.97 (3 ꢁ CO); HR-ESI-TOF-MS:
m/z 405.1162 ([M+Na]+), calcd for [C18H22O9+Na]+ 405.1156.
3.3.6. 2,3,5-Tri-O-acetyl-1-O-(4-hydroxyphenyl)-b-D-ribofurano
side (6h)
3.3.2. 2,3,5-Tri-O-acetyl-1-O-(3-methylphenyl)-b-
D-ribofurano
It was obtained as crystalline solid (0.38 g) in 92% yield.
side (6d)
Rf = 0.85 (50% ethyl acetate in petroleum ether, v/v); mp 127–
It was obtained as semisolid (0.41 g) in 93% yield. Rf = 0.88 (30%
128 °C; ½a 3D1
ꢂ
= ꢀ0.4° (c 0.25, MeOH); IR (Nujol)
mmax: 3427, 1748,
ethyl acetate in petroleum ether, v/v); ½a D24
ꢂ
= ꢀ2.2° (c 0.1, MeOH);
1511, 1371, 1215, 1044 and 832 cmꢀ1 1H NMR (300 MHz,
;
IR (Nujol)
m
max: 1740, 1518, 1374, 1222, 1038 and 783 cmꢀ1
;
1H
DMSO-d6): d 1.97, 2.09 and 2.14 (9H, 3s, 3H each, 3 ꢁ COCH3),
NMR (300 MHz, CDCl3): d 1.95, 2.09 and 2.20 (9H, 3s, 3H each,
4.75 (1H, dd, J = 11.7 and 4.5 Hz, C-5H ), 4.36–4.50 (2H, m, C-4H
a
3 ꢁ COCH3), 2.31 (3H, s, ArCH3), 4.05–4.07 (1H, m, C-5H ), 4.40–
and C-5Hb), 5.46–5.53 (3H, m, C-1H, C-2H and C-3H), 5.66 (1H, s,
a
4.43 (2H, m, C-4H and C-5Hb), 5.47–5.52 (2H, m, C-2H and C-3H),
5.64 (1H, s, C-1H), 6.79–6.84 and 7.13–7.15 (4H; 3H, m and 1H,
m; aromatic protons); 13C NMR (75.5 MHz, CDCl3): d 16.20 and
17.08 (3 ꢁ COCH3 and ArCH3, 59.26 (C-5), 66.90 (C-3), 70.70 (C-
2), 74.81 (C-4), 98.91 (C-1), 109.01, 112.75, 118.97, 124.89,
135.26 and 151.81 (aromatic carbons), and 165.21 & 166.23
(3 ꢁ CO); HR-ESI-TOF-MS: m/z 389.1205 ([M+Na]+), calcd for
[C18H22O8+Na]+ 389.1207.
-OH), 6.72 and 6.86 (4H; 2d, 2H each, J = 8.0 Hz; aromatic protons);
13C NMR (75.5 MHz, DMSO-d6):
d 20.50, 20.57 and 20.65
(3 ꢁ COCH3, 63.54 (C-5), 71.14 (C-3), 74.97 (C-2), 79.00 (C-4),
104.16 (C-1), 115.97, 117.94, 150.02 and 151.31 (aromatic car-
bons), and 169.80, 169.87 & 170.97 (3 ꢁ CO); HR-ESI-TOF-MS: m/
z 391.0997 ([M+Na]+), calcd for [C17H20O9+Na]+ 391.1000.
3.3.7. 2,3-Di-O-acetyl-1-O-(1-naphthyl)-a-D-ribofuranoside (7a)
It was obtained as colorless oil (0.27 g) in 95% yield. Rf = 0.28
3.3.3. 2,3,5-Tri-O-acetyl-1-O-(4-methylphenyl)-b-
side (6e)
D
-ribofurano
(30% ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= +3.12° (c 0.25,
MeOH); IR (Nujol) mmax: 3471, 1745, 1599, 1371, 1232, 1042 and
It was obtained as semisolid (0.40 g) in 94% yield. Rf = 0.79 (30%
773 cmꢀ1 1H NMR (300 MHz, CDCl3): d 2.14 and 2.23 (6H, 2s, 3H
;
ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= ꢀ2.04° (c 0.25,
each, 2 ꢁ COCH3), 3.86 (2H, br s, C-5H +b), 4.37 (1H, d, J = 2.8 Hz,
a
MeOH); IR (Nujol)
m
max: 1746, 1510, 1377, 1218, 1036 and
C-4H), 5.23 (1H, dd, J = 6.8 and 4.3 Hz, C-2H), 5.47 (1H, dd, J = 6.8
and 2.7 Hz, C-3H), 6.13 (1H, d, J = 4.3 Hz, C-1H), 7.14, 7.36–7.41,
7.47–7.53, 7.80–7.83 and 8.24–8.27 (7H; 1H, d, J = 7.6 Hz; 1H, m;
3H, m; 1H, m and 1H, m; aromatic protons); 13C NMR (75.5 MHz,
CDCl3): d 21.45 and 21.83 (2 ꢁ COCH3), 63.20 (C-5), 71.39 (C-3),
72.59 (C-2), 84.78 (C-4), 99.99 (C-1), 109.93, 122.75, 123.04,
126.35, 126.79, 127.33, 127.62, 128.59, 135.56 and 153.22 (aro-
matic carbons), and 170.95 & 171.64 (2 ꢁ CO); HR-ESI-TOF-MS:
m/z 383.1098 ([M+Na]+), calcd for [C19H20O7+Na]+ 383.1101.
785 cmꢀ1 1H NMR (300 MHz, CDCl3): d 1.95, 2.09 and 2.14 (9H,
;
3s, 3H each, 3 ꢁ COCH3), 2.28 (3H, s, ArCH3), 4.06 (1H, dd, J = 11.2
and 4.2 Hz, C-5H ), 4.37–4.46 (2H, m, C-4H and C-5Hb), 5.47–
a
5.54 (2H, m, C-2H and C-3H), 5.60 (1H, s, C-1H), 6.88 and 7.07
(4H; 2d, 2H each, J = 8.4 Hz; aromatic protons); 13C NMR
(75.5 MHz, CDCl3): d 20.90 and 21.99 (3 ꢁ COCH3 and ArCH3),
63.95 (C-5), 71.60 (C-3), 75.40 (C-2), 79.48 (C-4), 103.92 (C-1),
116.74, 130.33, 132.29 and 154.45 (aromatic carbons), and
169.94, 170.07 & 170.97 (3 ꢁ CO); HR-ESI-TOF-MS: m/z 389.1208
([M+Na]+), calcd for [C18H22O8+Na]+ 389.1207.
3.3.8. 2,3-Di-O-acetyl-1-O-(2-naphthyl)-a-D-ribofuranoside (7b)
It was obtained as colorless oil (0.10 g) in 87% yield. Rf = 0.26
3.3.4. 2,3,5-Tri-O-acetyl-1-O-(3-methoxyphenyl)-b-
side (6f)
D
-ribofurano
(30% ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= +4.68° (c 0.25,
MeOH); IR (Nujol) mmax: 3471, 1743, 1599, 1371, 1245, 1047 and
It was obtained as semisolid (0.43 g) in 93% yield. Rf = 0.93 (30%
752 cmꢀ1 1H NMR (300 MHz, CDCl3): d 2.15 and 2.19 (6H, 2s, 3H
;
ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= ꢀ0.8° (c 0.25, MeOH);
each, 2 ꢁ COCH3), 3.80–3.86 (2H, m, C-5H +b), 4.35 (1H, t,
a
IR (Nujol)
m
max: 1751, 1603, 1370, 1234, 1045, 973 and 769 cmꢀ1
;
J = 3.2 Hz, C-4H), 5.19 (1H, dd, J = 7.1 and 4.5 Hz, C-2H), 5.40 (1H,
dd, J = 7.1 and 3.4 Hz, C-3H), 6.02 (1H, d, J = 4.5 Hz, C-1H), 7.21–
7.25, 7.36–7.44 and 7.73–7.78 (7H; 1H, m; 3H, m and 3H, m; aro-
matic protons); 13C NMR (75.5 MHz, DMSO-d6): d 20.94, 21.27
(2 ꢁ COCH3), 62.45 (C-5), 70.59 (C-3), 71.69 (C-2), 83.72 (C-4),
99.83 (C-1), 112.28, 119.83, 124.79, 126.84, 127.54, 128.03,
129.88, 130.28, 134.67 and 154.88 (aromatic carbons), and
1H NMR (300 MHz, DMSO-d6): d 1.90, 2.03 and 2.11 (9H, 3s, 3H
each, 3 ꢁ COCH3), 3.73 (3H, s, OCH3), 3.96–4.02 (1H, m, C-5H ),
a
4.33–4.40 (2H, m, C-4H and C-5Hb), 5.33–5.36 (2H, m, C-2H and
C-3H), 5.82 (1H, s, C-1H), 6.59–6.62 and 7.17–7.23 (4H; 3H, m
and 1H, m; aromatic protons); 13C NMR (75.5 MHz, DMSO-d6): d
20.26 and 20.34 (3 ꢁ COCH3, 55.12 OCH3, 62.98 Cꢀ5, 70.52 (C-3),
74.06 (C-2), 78.77 (C-4), 102.40 (C-1), 102.42, 108.07, 108.28,
129.99, 156.75 and 160.32 (aromatic carbons), and 169.38,
170.45
&
171.19 (2 ꢁ CO); HR-ESI-TOF-MS: m/z 383.1095
([M+Na]+), calcd for [C19H20O7+Na]+ 383.1101.
169.58
&
169.88 (3 ꢁ CO); HR-ESI-TOF-MS: m/z 405.1151
([M+Na]+), calcd for [C18H22O9+Na]+ 405.1156.
3.3.9. 2,3-Di-O-acetyl-1-O-(4-biphenyl)-a-D-ribofuranoside (7c)
It was obtained as colorless oil (0.13 g) in 95% yield. Rf = 0.43
3.3.5. 2,3,5-Tri-O-acetyl-1-O-(4-methoxyphenyl)-b-
side (6g)
D
-ribofurano
(20% ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= +6.24° (c 0.25,
MeOH); IR (Nujol) mmax: 3392, 1741, 1517, 1370, 1227, 1041 and
It was obtained as crystalline solid (0.40 g) in 91% yield.
763 cmꢀ1 1H NMR (300 MHz, CDCl3+DMSO-d6): d 2.09 and 2.13
;
Rf = 0.89 (30% ethyl acetate in petroleum ether, v/v); mp 77–
(6H, 2s, 3H each, 2 ꢁ COCH3), 3.62 (2H, m, C-5H +b), 4.23 (1H, br
a
78 °C; ½a 2D4
ꢂ
= ꢀ2.0° (c 0.1, MeOH); IR (Nujol)
m
max: 1748, 1520,
s, C-4H), 5.05 (1H, t, J = 5.4 Hz, –OH), 5.18 (1H, t, J = 4.9 Hz, C-
2H), 5.32 (1H, t, J = 2.4 Hz, C-3H), 5.93 (1H, d, J = 4.5 Hz, C-1H),
7.10–7.13, 7.30–7.32, 7.40–7.45 and 7.57–7.59 (9H; 2H, m; 1H,
m; 2H, m and 4H, m; aromatic protons); 13C NMR (75.5 MHz,
CDCl3+DMSO-d6): d 21.09 and 21.40 (2 ꢁ COCH3), 61.66 (C-5),
70.73 (C-3), 71.69 (C-2), 84.31 (C-4), 99.58 (C-1), 118.24, 127.11,
127.61, 128.51, 129.54, 135.19, 140.63 and 156.97 (aromatic car-
1380, 1222, 1018 and 786 cmꢀ1
;
1H NMR (300 MHz, CDCl3): d
1.97, 2.09 and 2.14 (9H, 3s, 3H each, 3 ꢁ COCH3), 3.77 (3H, s,
OCH3), 4.07 (1H, dd, J = 11.7 and 4.5 Hz, C-5H ), 4.38–4.46 (2H,
a
m, C-4H and C-5Hb), 5.46–5.54 (3H, m, C-1H, C-2H and C-3H),
6.81 and 6.94 (4H; 2d, 2H each, J = 8.5 Hz; aromatic protons); 13C
NMR (75.5 MHz, CDCl3): d 20.90, 20.95 and 21.02 (3 ꢁ COCH3,
55.99 (OCH3, 63.94 (C-5), 71.55 (C-3), 75.35 (C-2), 79.43 (C-4),
104.54 (C-1), 114.95, 118.17, 150.63 and 155.53 (aromatic
bons), and 170.10
&
170.61 (2 ꢁ CO); HR-ESI-TOF-MS: m/z
409.1259 ([M+Na]+), calcd for [C21H22O7+Na]+ 409.1258.

R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
6827
3.3.10. 2,3-Di-O-acetyl-1-O-(3-methylphenyl)-
anoside (7d)
a
-D-ribofur
169.48
&
169.97 (2 ꢁ CO); HR-ESI-TOF-MS: m/z 363.1036
([M+Na]+), calcd for [C16H20O8+Na]+ 363.1050.
It was obtained as colorless oil (0.09 g) in 94% yield. Rf = 0.34
(30% ethyl acetate in petroleum ether, v/v); ½a D24
ꢂ
= +8.7° (c 0.1,
max: 3418, 1746, 1510, 1377, 1218, 1036 and
3.3.14. 2,3-Di-O-acetyl-1-O-(4-hydroxyphenyl)-a-D-
ribofuranoside (7h)
MeOH); IR (Nujol)
m
785 cmꢀ1
;
1H NMR (300 MHz, DMSO-d6): d 2.06 and 2.10 (6H, 2s,
It was obtained as colorless oil (0.12 g) in 91% yield. Rf = 0.15
3H each, 2 ꢁ COCH3), 2.28 (3H, s, ArCH3), 3.55–3.58 (2H, m, C-
(50% ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= +4.5° (c 0.25,
5H +b), 4.17 (1H, dd, J = 6.3 and 3.0 Hz, C-4H), 5.07 (1H, t,
MeOH); IR (Nujol) mmax: 3435, 1742, 1510, 1374, 1225, 1044 and
a
J = 5.7 Hz, –OH), 5.13 (1H, dd, J = 6.8 and 4.8 Hz, C-2H), 5.27 (1H,
dd, J = 6.8 and 3.3 Hz, C-3H), 5.87 (1H, d, J = 4.8 Hz, C-1H), 6.81–
6.85 and 7.15–7.20 (4H; 3H, m and 1H, m; aromatic protons);
756 cmꢀ1 1H NMR (300 MHz, CDCl3): d 2.16 and 2.17 (6H, 2s, 3H
;
each, 2 ꢁ COCH3), 3.78–3.91 (2H, m, C-5H +b), 4.32–4.34 (1H, m,
a
C-4H), 5.08 (1H, dd, J = 7.2 and 3.0 Hz, C-2H), 5.30–5.33 (2H, m,
C-3H and –OH), 5.73 (1H, d, J = 4.5 Hz, C-1H), 6.73 and 6.89 (4H;
2d, 2H each, J = 8.6 Hz; aromatic protons); 13C NMR (75.5 MHz,
CDCl3): d 20.58 and 20.87 (2 ꢁ COCH3, 62.08 (C-5), 70.09 (C-3),
71.28 (C-2), 82.26 (C-4), 100.65 (C-1), 116.03, 119.44, 150.45 and
151.63 (aromatic carbons), and 170.34 & 170.95 (2 ꢁ CO); HR-
ESI-TOF-MS: m/z 349.0893 ([M+Na]+), calcd for [C15H18O8+Na]+
349.0894.
13C NMR (75.5 MHz, DMSO-d6):
d 20.25, 20.56 and 20.96
(2 ꢁ COCH3 and ArCH3, 60.74 Cꢀ5, 69.82 (C-3), 70.61 (C-2), 83.22
(C-4), 98.55 (C-1), 113.94, 117.63, 122.86, 129.18, 139.01 and
156.48 (aromatic carbons), and 169.45 & 169.96 (2 ꢁ CO); HR-
ESI-TOF-MS: m/z 347.1090 ([M+Na]+), calcd for [C16H20O7+Na]+
347.1101.
3.3.11. 2,3-Di-O-acetyl-1-O-(4-methylphenyl)-a-D-ribofurano
side (7e)
3.4. General procedure for the deacetylation of 6a–h and 7a–h:
Preparation of 1-O-aryl-b-D-ribofuranosides (8a–h) and 1-O-
It was obtained as colorless oil (0.10 g) in 91% yield. Rf = 0.31
(30% ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= +5.96° (c 0.25,
aryl- -ribofuranosides (9a–h)
a-D
MeOH); IR (Nujol) mmax: 3480, 1746, 1614, 1373, 1224, 1047 and
781 cmꢀ1 1H NMR (300 MHz, CDCl3): d 2.15 and 2.17 (6H, 2s, 3H
;
The peracetylated O-aryl b-
D-ribofuronosides 6a–h and the par-
tially acetylated O-aryl -ribofuranosides 7a–h (0.7 mmol) were
a
-D
each, COCH3), 2.30 (3H, s, ArCH3), 3.83–3.85 (2H, m, C-5H +b),
a
dissolved in methanol (10 mL) and saturated methanolic ammonia
solution (10 mL) was added (Scheme 2). The reaction mixture was
stirred for 6–8 h at room temperature to achieve the complete
deacetylation as indicated by TLC. The methanol was removed un-
der reduced pressure and the residue was subjected to column
chromatography over silica gel with chloroform in methanol as
4.31 (1H, d, J = 3.3 Hz, C-4H), 5.12 (1H, dd, J = 7.2 and 4.5 Hz, C-
2H), 5.33 (1H, dd, J = 7.2 and 3.6 Hz, C-3H), 5.84 (1H, d, J = 4.5 Hz,
C-1H), 6.95 and 7.09 (4H; 2d, 2H each, J = 8.5 Hz; aromatic pro-
tons); 13C NMR (75.5 MHz, CDCl3): d 21.49, 21.55 and 21.81
(2 ꢁ COCH3 and ArCH3), 63.05 (C-5), 71.03 (C-3), 72.14 (C-2),
83.87 (C-4), 100.74 (C-1), 118.58, 130.90, 154.18 and 164.47 (aro-
matic carbons), and 170.95 (2 ꢁ CO); HR-ESI-TOF-MS: m/z
347.1106 ([M+Na]+), calcd for [C16H20O7+Na]+ 347.1101.
eluent to afford the b- and a-O-arylribofuranosides 8a–h and 9a–
h in 88–94% and 85–92% yields, respectively. All the compounds,
that is, 8a–h and 9a–h were unambiguously identified on the basis
of their spectral data; the structures of known compounds 8a,9a
8g,39 8h9a and 9e40 were further confirmed on the basis of compar-
ison of their spectral data with those reported in the literature.
Only partial spectral data of 8a, 8g–h and 9e were reported in
the mentioned references and therefore we report here the com-
plete spectral data of these known compounds as well.
3.3.12. 2,3-Di-O-acetyl-1-O-(3-methoxyphenyl)-a-D-ribofurano
side (7f)
It was obtained as colorless oil (0.04 g) in 89% yield. Rf = 0.37
(30% ethyl acetate in petroleum ether, v/v); ½a D31
ꢂ
= +2.7° (c 0.25,
MeOH); IR (Nujol) mmax: 3487, 1744, 1491, 1372, 1243, 1044 and
770 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 2.06 and 2.11 (6H, 2s,
;
3H each, 2 ꢁ COCH3), 3.55–3.58 (2H, m, C-5H +b), 3.73 (3H, s,
a
3.4.1. 1-O-(1-Naphthyl)-b-D-ribofuranoside (8a)
OCH3), 4.19 (1H, dd, J = 6.2 and 3.3 Hz, C-4H), 5.06 (1H, t,
J = 5.7 Hz, –OH), 5.14 (1H, dd, J = 6.7 and 4.5 Hz, C-2H), 5.27 (1H,
dd, J = 6.7 and 3.3 Hz, C-3H), 5.89 (1H, d, J = 4.5 Hz, C-1H), 6.56–
6.63 and 7.18–7.23 (4H; 3H, m and 1H, m; aromatic protons);
13C NMR (75.5 MHz, DMSO-d6): d 20.26 and 20.56 (2 ꢁ COCH3,
55.13 OCH3 60.71 (C-5), 69.77 (C-3), 70.58 (C-2), 83.32 (C-4),
98.59 (C-1), 103.15, 107.83, 109.13, 129.95, 157.64 and 160.32
(aromatic carbons), and 169.45 & 169.97 (2 ꢁ CO); HR-ESI-TOF-
MS: m/z 363.1045 ([M+Na]+), calcd for [C16H20O8+Na]+ 363.1050.
It was obtained as white solid (0.18 g) in 91% yield. Rf = 0.40
(10% methanol in chloroform, v/v); mp 133–134 °C; ½a D31
ꢂ = ꢀ1.76°
(c 0.25, MeOH); IR (KBr)
mmax: 3311, 1581, 1462, 1398, 1264,
1137, 1048 and 764 cmꢀ1 1H NMR (300 MHz, CDCl3 + DMSO-d6):
;
d 3.58 (1H, dd, J = 11.7 and 3.6 Hz, C-5H ), 3.71 (1H, dd, J =11.7
a
and 4.8 Hz, C-5Hb), 4.05 (1H, t, J = 5.7 Hz, C-4H), 4.13 (1H, dd,
J = 9.5 and 5.6 Hz, C-3H), 4.35-4.38 (2H, m, C-2H and -OH), 4.71
and 5.03 (1H, d, J = 6.1 Hz and 1H, d, J = 3.8 Hz; 2 ꢁ -OH), 5.75
(1H, s, C-1H), 7.11–7.13, 7.34–7.39, 7.45–7.49, 7.78–7.80 and
8.14–8.16 (7H; 1H, m; 1H, m; 3H, m; 1H, m and 1H, m; aromatic
protons); 13C NMR (75.5 MHz, CDCl3 + DMSO-d6): d 63.09 (C-5),
71.04 (C-3), 75.41 (C-2), 85.06 (C-4), 105.76 (C-1), 108.14,
121.17, 121.85, 125.27, 125.90, 126.31, 127.40, 134.36 and
154.02 (aromatic carbons); HR-ESI-TOF-MS: m/z 299.0891
([M+Na]+), calcd for [C15H16O5+Na]+ 299.0890.
3.3.13. 2,3-Di-O-acetyl-1-O-(4-methoxyphenyl)-a-D-ribofurano
side (7g)
It was obtained as colorless oil (0.11 g) in 93% yield. Rf = 0.34
(30% ethyl acetate in petroleum ether, v/v); ½a D24
ꢂ
= +5.5° (c 0.1,
MeOH); IR (Nujol) mmax: 3428, 1738, 1518, 1372, 1236, 1050 and
730 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 2.05 and 2.10 (6H, 2s,
;
3H each, 2 ꢁ COCH3), 3.55–3.58 (2H, m, C-5H +b), 3.70 (3H, s,
3.4.2. 1-O-(2-Naphthyl)-b-D-ribofuranoside (8b)
a
OCH3), 4.18 (1H, dd, J = 6.4 and 3.3 Hz, C-4H), 5.04 (1H, t,
J = 5.7 Hz, –OH), 5.10 (1H, dd, J = 6.8 and 4.5 Hz, C-2H), 5.26 (1H,
dd, J = 6.8 and 3.3 Hz, C-3H), 5.73 (1H, d, J = 4.5 Hz, C-1H), 6.84–
6.89 and 6.93–6.98 (4H; 2 m, 2H each; aromatic protons); 13C
NMR (75.5 MHz, DMSO-d6): d 20.28 and 20.57 (2 ꢁ COCH3, 55.32
(OCH3, 60.74 (C-5), 69.75 (C-3), 70.65 (C-2), 83.07 (C-4), 99.73
(C-1), 114.51, 118.66, 150.33 and 154.63 (aromatic carbons), and
It was obtained as white solid (0.17 g) in 88% yield. Rf = 0.35
(10% methanol in chloroform, v/v); mp 132–134 °C; ½a D31
= ꢀ6.32°
ꢂ
(c 0.25, MeOH); IR (KBr)
mmax: 3452, 3368, 1626, 1599, 1468,
1389, 1255, 1180, 1027 and 746 cmꢀ1
;
1H NMR (300 MHz,
CDCl3 + DMSO-d6): d 3.46 (1H, br s, C-5H ), 3.63 1H, br s, C-5Hb),
a
4.01 (1H, br s, C-4H), 4.13 (2H, br s, C-2H and C-3H), 4.62, 5.00
and 5.32 (1H, br s; 1H, d, J = 4.6 Hz and 1H, br s; 3 ꢁ –OH), 5.63

6828
R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
(1H, s, C-1H), 7.15–7.17, 7.31–7.43 and 7.75–7.80 (7H; 1H, m; 3H,
and 3H, m; aromatic protons); 13C NMR (75.5 MHz,
carbons); HR-ESI-TOF-MS: m/z 279.0839 ([M+Na]+), calcd for
m
[C12H16O6+Na]+ 279.0839.
CDCl3 + DMSO-d6): d 63.59 (C-5), 71.42 (C-3), 75.54 (C-2), 85.44
(C-4), 106.06 (C-1), 110.53, 119.66, 124.50, 126.94, 127.48,
128.09, 129.61, 129.84, 134.74 and 155.16 (aromatic carbons);
HR-ESI-TOF-MS: m/z 299.0899 ([M+Na]+), calcd for [C15H16O5+Na]+
299.0890.
3.4.7. 1-O-(4-Methoxyphenyl)-b-D-ribofuranoside (8g)
It was obtained as white solid (0.16 g) in 92% yield. Rf = 0.47
(10% methanol in chloroform, v/v); mp 91–93 °C; ½a D24
= ꢀ4.9° (c
ꢂ
0.1, MeOH); IR (KBr) mmax: 3410, 3387, 1524, 1386, 1224, 1022
and 780 cmꢀ1 1H NMR (300 MHz, CDCl3 + DMSO-d6): d 3.32–3.36
;
3.4.3. 1-O-(4-Biphenyl)-b-
D
-ribofuranoside (8c)
(1H, m, C-5H ), 3.59–3.62 (1H, m, C-5Hb), 3.69 (3H, s, OCH3),
a
It was obtained as white solid (0.19 g) in 90% yield. Rf = 0.52
3.85–3.86 (1H, m, C-4H), 3.97 (2H, br s, C-2H and C-3H), 4.67,
4.97 and 5.25 (1H, t, J = 4.0 Hz; 1H, d, J = 5.7 Hz and 1H, d,
J = 4.0 Hz; 3 ꢁ –OH), 5.30 (1H, s, C-1H), 6.83 and 6.91 (4H; 2d, 2H
each, J = 9.0 Hz; aromatic protons); 13C NMR (75.5 MHz,
CDCl3 + DMSO-d6): d 54.56 (OCH3, 62.08 (C-5), 69.89 (C-3), 73.84
(C-2), 83.66 (C-4), 105.39 (C-1), 113.73, 116.95, 149.79 and
153.41 (aromatic carbons); HR-ESI-TOF-MS: m/z 279.0848
([M+Na]+), calcd for [C12H16O6+Na]+ 279.0839.
(10% methanol in chloroform, v/v); mp 122–124 °C; ½a D31
= ꢀ5.04°
ꢂ
(c 0.25, MeOH); IR (KBr)
mmax: 3345, 1604, 1486, 1235, 1114,
1058 and 769 cmꢀ1
;
1H NMR (300 MHz, CDCl3 + DMSO-d6): d
3.39–3.43 (1H, m, C-5H ), 3.58 (1H, dd, J = 10.4 and 4.5 Hz, C-
a
5Hb), 3.94 (1H, dd, J = 9.2 and 4.0 Hz, C-4H), 4.03–4.06 (2H, m, C-
2H and C-3H), 4.62, 4.96 and 5.27 (1H, t, J = 5.5 Hz; 1H, d,
J = 5.7 Hz and 1H, d, J = 4.0 Hz; 3 ꢁ –OH), 5.50 (1H, s, C-1H), 7.05–
7.07, 7.30–7.32, 7.39–7.44 and 7.54–7.59 (9H; 2H, m; 1H, m; 2H,
m and 4H, m; aromatic protons); 13C NMR (75.5 MHz, DMSO-d6):
d 63.65 (C-5), 71.49 (C-3), 75.57 (C-2), 85.51 (C-4), 106.18 (C-1),
117.47, 127.06, 127.52, 128.48, 129.55, 134.50, 140.71 and
157.09 (aromatic carbons); HR-ESI-TOF-MS: m/z 325.1034
([M+Na]+), calcd for [C17H18O5+Na]+ 325.1046.
3.4.8. 1-O-(4-Hydroxyphenyl)-b-D-ribofuranoside (8h)
It was obtained as white solid (0.16 g) in 92% yield. Rf = 0.25
(10% methanol in chloroform, v/v); mp 150–151 °C; ½a D31
= ꢀ1.7°
ꢂ
(c 0.25, MeOH); IR (KBr)
mmax: 3410, 3387, 1524, 1386, 1224,
1022 and 780 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 3.40 (1H, br
;
s, C-5H ), 3.51–3.54 (1H, m, C-5Hb), 3.70 (1H, br s, C-4H), 3.83–
a
3.4.4. 1-O-(3-Methylphenyl)-b-
D
-ribofuranoside (8d)
3.84 (2H, m, C-2H and C-3H), 4.66 and 4.94 (1H, t, J = 6.0 Hz and
1H, d, J = 5.7 Hz; 2 ꢁ aliphatic –OH), 5.30 (2H, br s, C-1H and ali-
phatic ꢀOH), 6.64 and 6.78 (4H; 2d, 2H each, J = 9.0 Hz; aromatic
protons), and 9.00 (1H, s, ArOH); 13C NMR (75.5 MHz,
CDCl3 + DMSO-d6): d 63.75 (C-5), 71.52 (C-3), 75.52 (C-2), 85.14
(C-4), 107.25 (C-1), 116.36, 118.55, 150.23 and 152.96 (aromatic
carbons); HR-ESI-TOF-MS: m/z 265.0688 ([M+Na]+), calcd for
[C11H14O6+Na]+ 265.0683.
It was obtained as white solid (0.15 g) in 91% yield. Rf = 0.45
(10% methanol in chloroform, v/v); mp 69–71 °C; ½a D24
= ꢀ4.2° (c
ꢂ
0.1, MeOH); IR (KBr) mmax: 3442, 3412, 1512, 1370, 1210, 1030
and 780 cmꢀ1 1H NMR (300 MHz, CDCl3 + DMSO-d6): d 2.29 (s,
;
3H, ArCH3), 3.60–3.64 (2H, m, C-5H +b), 3.97–3.98 (1H, m, C-4H),
a
4.07 (2H, m, C-2H and C-3H), 4.46, 4.87 and 5.15 (1H, d,
J = 5.3 Hz; 1H, d, J = 4.8 Hz and 1H, br s; 3 ꢁ –OH), 5.46 (s, 1H, C-
1H), 6.75–6.78 and 7.09–7.12 (4H; 3H, m and 1H, m; aromatic pro-
tons); 13C NMR (75.5 MHz, CDCl3 + DMSO-d6): d 21.92 (ArCH3,
63.67 (C-5), 71.47 (C-3), 75.60 (C-2), 85.30 (C-4), 106.03 (C-1),
113.90, 117.50, 122.93, 129.69, 139.59 and 157.40 (aromatic car-
bons); HR-ESI-TOF-MS: m/z 263.0895 ([M+Na]+), calcd for
[C12H16O5+Na]+ 263.0890.
3.4.9. 1-O-(1-Naphthyl)-a-D-ribofuranoside (9a)
It was obtained as white solid (0.17 g) in 87% yield. Rf = 0.38
(10% methanol in chloroform, v/v); mp 99–100 °C; ½a D31
ꢂ
= +3.04°
(c 0.25, MeOH); IR (KBr)
mmax: 3520, 3387, 3348, 1593, 1392,
;
1262, 1228, 1115, 1032 and 782 cmꢀ1 1H NMR (300 MHz,
DMSO-d6): d 3.67–3.69 (2H, m, C-5H +b), 4.22 1H, t, J = 2.9 Hz, C-
a
3.4.5. 1-O-(4-Methylphenyl)-b-
D
-ribofuranoside (8e)
4H), 4.27 (1H, t, J = 3.6 Hz, C-2H), 4.32–4.34 (1H, m, C-3H), 4.38–
4.44 and 4.70 (2H, m and 1H, d, J = 5.3 Hz; 3 ꢁ –OH), 5.80 (1H, d,
J = 4.1 Hz, C-1H), 7.20–7.22, 7.35–7.40, 7.45–7.51, 7.78–7.80 and
8.38 (7H; 1H, m; 1H, m; 3H, m; 1H, m and 1H, br s; aromatic pro-
tons); 13C NMR (75.5 MHz, CDCl3 + DMSO-d6): d 61.20 (C-5), 69.80
(C-3), 72.24 (C-2), 86.74 (C-4), 101.41 (C-1), 109.80, 121.57, 122.45,
125.22, 125.77, 126.20, 126.42, 127.27, 134.35 and 152.84 (aro-
matic carbons); HR-ESI-TOF-MS: m/z 299.0890 ([M+Na]+), calcd
for [C15H16O5+Na]+ 299.0890.
It was obtained as white solid (0.16 g) in 93% yield. Rf = 0.33
(10% methanol in chloroform, v/v); mp 78–80 °C; ½a D31
= ꢀ3.16° (c
ꢂ
0.25, MeOH); IR (KBr) mmax: 3430, 1610, 1509, 1218, 1130, 1051
and 784 cmꢀ1 1H NMR (300 MHz, CDCl3 + DMSO-d6): d 2.22 (3H,
;
s, Ar-CH3), 3.40 (1H, m, C-5H ), 3.51–3.55 (1H, m, C-5Hb), 3.87
a
(1H, br s, C-4H), 3.98 (2H, br s, C-2H and C-3H), 4.67, 5.00 and
5.29 (1H, br s; 1H, d, J = 3.5 Hz and 1H, br s; 3 ꢁ -OH), 5.37 (1H,
s, C-1H), 6.85 and 7.06 (4H; 2d, 2H each, J = 7.2 Hz; aromatic pro-
tons); 13C NMR (75.5 MHz, CDCl3 + DMSO-d6): d 20.96 (ArCH3),
63.70 (C-5), 71.52 (C-3), 75.47 (C-2), 85.33 (C-4), 106.35 (C-1),
117.11, 130.62, 131.18 and 155.37 (aromatic carbons); HR-ESI-
TOF-MS: m/z 263.0903 ([M+Na]+), calcd for [C12H16O5+Na]+ 263.
0890.
3.4.10. 1-O-(2-Naphthyl)-a-D-ribofuranoside (9b)
It was obtained as white solid (0.17 g) in 89% yield. Rf = 0.32 (10%
methanol in chloroform, v/v); mp 137–139 °C; ½a D31
ꢂ
= +8.20° (c 0.25,
MeOH); IR (KBr) mmax: 3452, 3368, 1626, 1599, 1468, 1389, 1255,
1180, 1027 and 746 cmꢀ1 1H NMR (300 MHz, CDCl3 + DMSO-d6):
;
3.4.6. 1-O-(3-Methoxyphenyl)-b-
D
-ribofuranoside (8f)
d 3.63 (2H, m, C-5H +b), 4.09–4.22 (3H, m, C-2H, C-3H and C-4H),
a
It was obtained as white solid (0.17 g) in 94% yield. Rf = 0.52
4.46 and 4.68–4.74 (1H, d, J = 9.0 Hz and 2H, m; 3 ꢁ –OH), 5.72
(1H, br s, C-1H), 7.27–7.47 and 7.72–7.78 (7H; 4H, m and 3H, m; aro-
matic protons); 13C NMR (75.5 MHz, CDCl3 + DMSO-d6): d 60.96 (C-
5), 68.67 (C-3), 70.93 (C-2), 85.61 (C-4), 99.96 (C-1), 109.88, 118.60,
122.88, 125.18, 125.80, 126.42, 128.01, 128.20, 133.10 and 154.00
(aromatic carbons); HR-ESI-TOF-MS: m/z 299.0880 ([M+Na]+), calcd
for [C15H16O5+Na]+ 299.0890.
(10% methanol in chloroform, v/v); mp 69–71 °C; ½a D31
= ꢀ1.1° (c
ꢂ
0.25, MeOH); IR (KBr) mmax: 3442, 3412, 1512, 1370, 1210, 1030
and 780 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 3.38–3.40 (1H, m,
;
C-5H ), 3.53–3.57 (1H, m, C-5Hb), 3.72 (1H, s, OCH3), 3.86–3.96
a
(3H, m, C-2H, C-3H and C-4H), 4.67, 4.99 and 5.29 (1H, t,
J = 5.1 Hz; 1H, d, J = 5.4 Hz and 1H, d, J = 3.6 Hz; 3 ꢁ –OH), 5.42
(1H, s, C-1H), 6.52–6.58 and 7.15–7.20 (4H; 3H, m and 1H, m; aro-
matic protons); 13C NMR (75.5 MHz, DMSO-d6): d 55.05 (OCH3,
62.76 (C-5), 70.58 (C-3), 74.59 (C-2), 84.55 (C-4), 102.45 (C-1),
105.26, 107.21, 108.37, 129.88, 157.79 and 160.30 (aromatic
3.4.11. 1-O-(4-Biphenyl)-a-D-ribofuranoside (9c)
It was obtained as white solid (0.19 g) in 89% yield. Rf = 0.51
(10% methanol in chloroform, v/v); mp 64–65 °C; ½a D31
ꢂ
= +3.48° (c

R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
6829
0.25, MeOH); IR (KBr)
m
max: 3349, 1604, 1486, 1236, 1114, 1032
3.4.16. 1-O-(4-Hydroxyphenyl)-a-D-ribofuranoside (9h)
and 769 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 3.52 (2H, m, C-
;
It was obtained as white solid (0.15 g) in 88% yield. Rf = 0.20
5H +b), 3.99–4.11 (3H, m, C-2H, C-3H and C-4H), 4.61–4.64 and
(10% methanol in chloroform, v/v); mp 79–80 °C; ½a D31
ꢂ
= +1.8° (c
a
4.78–4.86 (1H, m and 2H, m; 3 ꢁ –OH), 5.62 (1H, br s, C-1H),
7.13–7.15, 7.30–7.32, 7.40–7.44 and 7.55–7.57 (9H; 2H, m; 1H,
m; 2H, m and 4H, m; aromatic protons); 13C NMR (75.5 MHz,
DMSO-d6): d 62.47 (C-5), 70.19 (C-3), 72.42 (C-2), 87.09 (C-4),
101.40 (C-1), 118.04, 127.05, 127.49, 128.36, 129.53, 134.51,
140.76 and 157.61 (aromatic carbons); HR-ESI-TOF-MS: m/z
325.1035 ([M+Na]+), calcd for [C17H18O5+Na]+ 325.1046.
0.25, MeOH); IR (KBr) mmax: 3440, 3403, 1520, 1380, 1232, 1014,
and 791 cmꢀ1 1H NMR (300 MHz, DMSO-d6): d 3.46 (2H, br s, C-
;
5H +b), 3.89–3.96 (3H, m, C-2H, C-3H and C-4H), 4.56–4.59 and
a
4.79–4.84 (1H, m and 2H, m; 3 ꢁ aliphatic ꢀOH), 5.36 (1H, d,
J = 4.3 Hz, C-1H), 6.66 and 6.85 (4H; 2d, 2H each, J = 8.4 Hz; aro-
matic protons) and 9.02 (1H, s, ArOH); 13C NMR (75.5 MHz,
CDCl3 + DMSO-d6): d 63.63 (C-5), 71.31 (C-3), 73.48 (C-2), 87.82
(C-4), 103.69 (C-1), 117.44, 120.35, 151.83 and 154.15 (aromatic
carbons); HR-ESI-TOF-MS: m/z 265.0695 ([M+Na]+), calcd for
[C11H14O6+Na]+ 265.0683.
3.4.12. 1-O-(3-Methylphenyl)-a-D-ribofuranoside (9d)
It was obtained as white solid (0.15 g) in 92% yield. Rf = 0.44 (10%
methanol in chloroform, v/v); mp 113–114 °C; ½a D24
ꢂ
= +4.0° (c 0.1,
MeOH); IR (KBr)
;
m
max: 3452, 1511, 1379, 1218, 1032 and 783 cm
3.5. c-Src kinase activity assay
ꢀ1
1H NMR (300 MHz, CDCl3 + DMSO-d6): d 2.30 (s, 3H, ArCH3),
3.58 (2H, m, C-5H +b), 4.05–4.14 (3H, m, C-2H, C-3H and C-4H),
The effect of synthesized compounds on the activity of c-Src
kinase was determined by HTScan Src Kinase Assay Kit, catalogue
number 7776 from Cell Signaling Technology; according to manu-
facturer’s protocol. Streptavidin coated plates was purchased from
Pierce. In summary, the kinase reaction was started with the incu-
a
4.40 and 4.70–4.74 (1H, d, J = 9.1 Hz and 2H, m; 3 ꢁ –OH), 5.54
(1H, d, J = 4.4 Hz, C-1H), 6.77–6.79, 6.85–6.89 and 7.10–7.15 (4H;
1H, m; 2H, m and 1H, m; aromatic protons); 13C NMR (75.5 MHz,
CDCl3 + DMSO-d6): d 21.40 (ArCH3, 62.00 (C-5), 69.72 (C-3), 71.89
(C-2), 86.48 (C-4), 100.87 (C-1), 114.13, 117.76, 122.60, 129.04,
138.96 and 157.29 (aromatic carbons); HR-ESI-TOF-MS: m/z
263.0894 ([M+Na]+), calcd for [C12H16O5+Na]+ 263.0890.
bation of the 12.5
kinase in 1.25 mM DTT) with 12.5
(dissolved in 1% DMSO) for 5 min at room temperature. ATP/sub-
strate (25 L, 20 M/1.5 M) cocktail was added to the mixture.
lL of the reaction cocktail (0.5 ng/
lL of GST-Src
lL of prediluted compounds
l
l
l
3.4.13. 1-O-(4-Methylphenyl)-
a
-
D
-ribofuranoside (9e)
The biotinylated substrate (catalogue number 1366) contains the
residues surrounding tyrosine 160 (Tyr160) of signal transduction
protein with a sequence of EGIYDVP. The reaction mixture was
incubated for 30 min at room temperature. The kinase reaction
It was obtained as white solid (0.15 g) in 91% yield. Rf = 0.31
(10% methanol in chloroform, v/v); mp 103–105 °C; ½a D31
ꢂ
= +4.80°
(c 0.25, MeOH); IR (KBr)
mmax: 3475, 3392, 1612, 1513, 1461,
1236, 1142, 1055 and 729 cmꢀ1
;
1H NMR (300 MHz,
was stopped with the addition of 50
The reaction solution (25 L) was transferred into 96-well strepta-
vidin plates (Pierce, part number 15125), diluted with 75 L dou-
lL of 50 mM EDTA (pH 8.0).
CDCl3 + DMSO-d6): d 2.25 (3H, s, ArCH3), 3.54 (2H, m, C-5H +b),
l
a
3.98–4.10 (3H, m, C-2H, C-3H and C-4H), 4.47 and 4.71–4.77 (1H,
d, J = 9.0 Hz and 2H, m; 3 ꢁ ꢀOH), 5.49 (1H, d, J = 4.3 Hz, C-1H),
6.94 and 7.05 (4H; 2d, 2H each, J = 8.3 Hz; aromatic protons); 13C
NMR (75.5 MHz, CDCl3 + DMSO-d6): d 21.01 (ArCH3), 62.51 (C-5),
70.22 (C-3), 72.40 (C-2), 86.90 (C-4), 101.72 (C-1), 117.68,
130.30, 131.21 and 155.82 (aromatic carbons); HR-ESI-TOF-MS:
m/z 263.0882 ([M+Na]+), calcd for [C12H16O5+Na]+ 263.0890.
l
ble distilled water, and incubated at room temperature for
60 min. At the end of the incubation, the wells were washed three
times with 200
lL of 0.05% Tween-20 in PBS buffer (PBS/T). After
that to the each well was added 100
lL of phosphotyrosine anti-
body (P-Tyr-100) (1:1000 dilution in PBS/T with 1% BSA) and the
wells were incubated for another 60 min. After washing three
times with 0.05% Tween-20 in PBS/T, the wells were incubated
3.4.14. 1-O-(3-Methoxyphenyl)-
a-
D-ribofuranoside (9f)
with 100 lL secondary anti-mouse IgG antibody, which was HRP-
It was obtained as white semisolid (0.18 g) in 85% yield.
conjugated (1:500 dilution in PBS/T with 1% BSA) for next 30 min
at room temperature. The wells were washed five times with
Rf = 0.50 (10% methanol in chloroform, v/v); ½a D31
ꢂ
= +1.2° (c 0.25,
max: 3452, 1511, 1379, 1218, 1032 and 783 cm
MeOH); IR (KBr)
m
0.05% Tween-20 in PBS and then were incubated with 100
3,30,5,50-tetramethylbenzidine dihydrochloride (TMB) substrate
for 5 min. The reaction was stopped by adding 100 L/well of stop
lL of
ꢀ1
;
1H NMR (300 MHz, DMSO-d6): d 3.31 (2H, m, C-5H +b), 3.48
a
(3H, s, OCH3), 3.76–3.87 (3H, m, C-2H, C-3H and C-4H), 4.08 and
4.37 (1H, br s and 2H, br s; 3 ꢁ -OH), 5.28 (1H, d, J = 4.0 Hz, C-
1H), 6.24–6.27, 6.37–6.40 and 6.84–6.90 (4H; 1H, m; 2H, m and
1H, m; aromatic protons); 13C NMR (75.5 MHz, CDCl3 + DMSO-
d6): d 60.02 (OCH3), 66.94 (C-5), 74.64 (C-3), 76.82 (C-2), 91.42
(C-4), 105.83 (C-1), 108.28, 112.40, 114.08, 134.52 and 165.32
(aromatic carbons); HR-ESI-TOF-MS: m/z 279.0839 ([M+Na]+),
calcd for [C12H16O6+Na]+ 279.0839.
l
solution to each well and mixed well and read the absorbance at
450 nm using a microplate reader (Molecular devices, spectra
Max M2). IC50 values of the compounds were calculated using ORI-
GIN 6.0 (origin lab) software. IC50 is the concentration of the com-
pound that inhibited enzyme activity by 50%. All the experiments
were carried out triplicate.
3.6. Molecular modeling
3.4.15. 1-O-(4-Methoxyphenyl)-a-D-ribofuranoside (9g)
It was obtained as white solid (0.16 g) in 90% yield. Rf = 0.25
Simulations were performed with the Accelrys Discovery Studio
2.5 modeling package, with the CHARMm-based force field. Model
of compounds 8c and 8f bound to Src was constructed based on the
X-ray crystal structure of AMP-PNP, a nonhydrolyzable ATP analog,
bound to c-Src (2SRC) template from RCSB Protein Data Bank. For
the molecular modeling of 8c and 8f, after initial minimization of
the compounds, the coordinates and positions of the backbone
atoms of sugar groups were superimposed on the corresponding
atoms in AMP-PNP in complex with c-Src after which AMP-PNP
was deleted. For refinement, the compound-Src complex under-
went CHARMm minimization. All default parameters were used
in the minimization process.
(10% methanol in chloroform, v/v); mp 60–61 °C; ½a D24
ꢂ
= +6.1° (c
0.1, MeOH); IR (KBr) mmax: 3440, 3403, 1520, 1380, 1232, 1014
and 791 cmꢀ1 1H NMR (300 MHz, CDCl3 + DMSO-d6): d 3.56–3.58
;
(2H, m, C-5H +b), 3.73 (3H, s, OCH3), 4.00–4.09 (3H, m, C-2H, C-
a
3H and C-4H), 4.37–4.40 and 4.65–4.70 (1H, m and 2H, m; 3 ꢁ
–OH), 5.43 (1H, d, J = 4.3 Hz, C-1H), 6.79 and 7.00 (4H; 2d, 2H each,
J = 8.9 Hz; aromatic protons); 13C NMR (75.5 MHz, CDCl3 + DMSO-
d6): d 55.46 (OCH3, 62.07 (C-5), 69.79 (C-3), 71.92 (C-2), 86.28
(C-4), 102.07 (C-1), 114.30, 118.69, 151.08 and 154.71 (aromatic
carbons); HR-ESI-TOF-MS: m/z 279.0852 ([M+Na]+), calcd for
[C12H16O6+Na]+ 279.0839.

6830
R. K. Sharma et al. / Bioorg. Med. Chem. 20 (2012) 6821–6830
22. Brunton, V. G.; Avizienyte, E.; Fincham, V. J.; Serrels, B.; Metcalf, C. A., III;
Acknowledgments
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T.; Inigo, I.; Johnston, K.; Kamath, A.; Kan, D.; Klei, H.; Marathe, P.; Pang, S.;
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We acknowledge the financial support from the University of
Delhi (DU-DST Purse Grant to AKP and VSP), the Department of
Biotechnology (DBT, New Delhi under Indo-German DBT-BMBF
collaboration in Biotechnology to AKP and VSP) and the American
Cancer Society Grant # RSG-07-290-01-CDD (to KP). RKS and SS
thank DBT, New Delhi and UGC, New Delhi for the grant of Senior
Research Fellowships, respectively.
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