Acid-catalyzed dehydrative cyclization of 4-(D-galacto-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole. Synthesis and anomeric configuration of D-lyxo-C-nucleoside analogs

Article abstract of DOI:10.1016/S0008-6215(00)00251-2

Dehydration of 4-(D-galacto-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole with 20% methanolic sulfuric acid afforded the anomeric pairs of nucleosides, 4-(α-D-lyxopyranosyl)-2-phenyl-2H-1,2,3-triazole (major component) and its β-anomer, as well as 4-(α-D-lyxo

Full text of DOI:10.1016/S0008-6215(00)00251-2

www.elsevier.nl/locate/carres
Carbohydrate Research 330 (2001) 53–63
Acid-catalyzed dehydrative cyclization of
-galacto-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole.
Synthesis and anomeric configuration of
4-(
D
D-lyxo-C-nucleoside analogs
Mohammed A.E. Sallam,a,* Somaya M.E. Abdel Megid,a Leroy B. Townsendb
aDepartment of Chemistry, Faculty of Science, Alexandria Uni6ersity, Alexandria, Egypt
bDepartment of Medicinal Chemistry, School of Pharmacy, Uni6ersity of Michigan, Ann Arbor, MI 48109, USA
Received 29 June 2000; accepted 11 August 2000
Abstract
Dehydration of 4-(
the anomeric pairs of nucleosides, 4-(a-
b-anomer, as well as 4-(a- -lyxofuranosyl)-2H-1,2,3-triazole and its b-anomer. The four anomeric C-nucleosides
D
-galacto-pentitol-1-yl)-2-phenyl-2H-1,2,3-triazole with 20% methanolic sulfuric acid afforded
D
-lyxopyranosyl)-2-phenyl-2H-1,2,3-triazole (major component) and its
D
were separated by chromatography, and their structure and anomeric configuration were determined by periodate
oxidation, acylation, and NMR spectroscopy as well as mass spectrometry. The anomeric assignment from optical
rotation was not in agreement with final structure assignment and represented a violation of the Hudson isorotation
rules. NOE studies and X-ray diffraction measurements confirmed the anomeric configuration. © 2001 Elsevier
Science Ltd. All rights reserved.
Keywords: 2-Phenyl-2H-1,2,3-triazoles; a- and b-
tion
D
-Lyxopyranosyl-a- and b-D-lyxofuranosyl-C-nucleosides; Anomeric configura-
1. Introduction
has no effect on the stereoselectivity of this
process.2,8
We have been interested lately in the syn-
thesis of heterocyclic C-nucleoside analogs by
the dehydrative cyclization of heterocyclic
polyhydroxyalkyl analogs. Acid-catalyzed de-
hydration of tetritol-1-yl heterocyclic analogs
having four carbon atoms in the polyhydroxy-
alkyl chain1–8 is stereoselective with the for-
mation of a preponderant isomer having a
trans arrangement of the base moiety and a
2%-OH group. The change of the base moiety
The dehydrative cyclization of pentitol-1-yl
heterocyclic analogs having five carbon atoms
in the polyhydroxyalkyl chain is less stereose-
lective.
epimeric 4-
Acid-catalyzed
dehydration
of
D
-gluco- and 4-
D
-manno-hept-2-
ulose phenylosazones gave a mixture of pyra-
nosyl and furanosyl analogs.9 The products
were isolated by chromatography, and their
structure and anomeric configuration were de-
termined by spectral measurements. In a pre-
vious report,10 the acid-catalyzed dehydration
of
subsequent reflux with copper sulfate afforded
the anomeric 4-(a- and b- -lyxopyranosyl)-2-
D-galacto-2-heptulose phenylosazone and
* Corresponding author. Tel.: +203-481-2110; fax: +203-
391-1794.
D
0008-6215/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(00)00251-2

54
M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
phenyl-2H-1,2,3-triazole-C-nucleosides (2 and
4) which were separated from the reaction
mixture by fractional recrystallization in lower
yield. Their structure and anomeric configura-
tion were erroneously assigned as anomeric
lyxofuranosides.
syrupy mixture and was partially separated by
filtration. The mother liquor was chro-
matographed on an ion-exchange resin (OH−)
form, with gradient elution with aqueous
methanol. The pyranosyl anomer 2, followed
by 4-(b- -lyxopyranosyl)-2-phenyl-2H-1,2,3-
D
triazole (4), were eluted first from the column
with 60% aqueous methanol. These were fol-
lowed by the furanosyl anomeric pair, 4-(a- -
D
2. Results and discussion
lyxofuranosyl)-2-phenyl-2H-1,2,3-triazole (3),
and its anomer, 4-(b- -lyxofuranosyl)-2-
phenyl-2H-1,2,3-triazole (5). The byproduct
-lyxofuranosyl)-2-phenyl-
D
In the present work, 4-( -galacto-pentitol-
D
1-yl)-2-phenyl-2H-1,2,3-triazole (1), which is
more stable in acid medium than the precur-
sor phenylosazone — a property that makes
it more suitable for dehydrative cycliza-
tion — was subjected to acid-catalyzed dehy-
drative cyclization, giving better yield (40%
total yield) of anomeric pyranosyl and fura-
4-(5%-O-methyl-a-
D
2H-1,2,3-triazole (11) was finally eluted from
the column with 90% aqueous methanol.
Periodate oxidation of 2 and 4 consumed
two moles of oxidant in accord with the pyran-
1
osyl ring structure. The H NMR spectrum of
2 (Table 1) showed a triplet at l 4.99 of two
protons intensity corresponding to two over-
lapped hydroxyls and a doublet at l 4.69 that
disappeared by deuteration, corresponding to
three secondary hydroxyl groups. This sup-
ports the pyranosyl ring structure for 2. The
1H NMR spectrum of 4 (Table 1), showed
three doublets at l 4.87, 4.83, and 4.71, which
disappeared by deuteration corresponding to
three secondary hydroxyl groups, likewise in
accord with the pyranosyl ring structure.
Having the two pyranosyl anomers 2 and 4
nosyl
D-lyxo-C-nucleoside analogs. The dehy-
drative cyclization of 1 was effected by
refluxing with 20% methanolic sulfuric acid
solution with monitoring the reaction by TLC.
The 4-(a- -lyxopyranosyl)-2-phenyl-2H-1,2,3-
D
triazole (2) (Scheme 1) was obtained as the
predominant isomer that crystallized from the
1
on hand, their anomeric assignments from H
NMR spectral results were not in agreement
with their optical rotation properties. The spe-
cific rotation at the sodium
D
-line for com-
pound 2 showed lower specific rotation
([h]D +4.3°) than compound 4 ([h]D +52.3°)
suggesting the b- configuration for 2 and the
D
a- configuration for 4, according to the Hud-
D
son isorotation rules.11 However, this was not
1
in agreement with their H NMR spectral
measurements. Compound 2 showed the
anomeric proton as a doublet at l 4.62 having
coupling constant J1%,2% 9.7 Hz in accord12–14
with a diaxial orientation of H-1% and H-2% of
an a-
-1C4 conformation. On the other hand,
D
compound 4 showed the anomeric proton as a
singlet at l 4.69. This low J1%,2% coupling con-
stant value is in accord with the axial equato-
rial orientation of H-1% and H-2% of an b-
-4C1
D
conformation (Fig. 1). This was confirmed by
the large coupling constant value J3%,4% 10.2 Hz
for its acetyl derivative 8 (Table 1).
Scheme 1.

Table 1
1H NMR chemical shifts a (l) and first-order coupling constants (Hz) for compounds 2–12
Compd
Glycosyl part
2-Phenyl-2H-1,2,3-triazole
Phenyl group
H-1%
H-2%
H-3%
H-4%
H-5%
H-5%%
OH
OAc
Ip
H-5
o-
m-
p-
2 b
4.62d
J1%2% 9.7
3.98dd
J2%,3% 2.8
3.79m c
3.61t
J4%,5% 3.8
3.79m c
3.56d
J5%,5%% 10.8
4.99t
2%-OH,
3%-OH
4.69d
J 7.3
5.2d
J 7.3
4.95d
J 4.2
4.58t
J 5.5
4.87d
J 5.6
4.83d
J 5.7
4.71d
J 5.0
5.09d
4.99d
4.89t
8.03s
7.77d
J 8.0
7.55dd
J 7.7,
J 8.1
7.40t
3 b
4.83d
J1%2%
8.1
4.32dd
J2%,3% 4.1
4.16m
3.85
4.16m
3.71m
3.68dd
J4%,5% 4.6
J5%,5%% 11.5
3.54dd
J4%,5%% 5.8
8.12s
7.96s
7.99t
7.55t
7.41t
7.39t
4 b
4.69s
3.85
3.44dd
J4%,5% 3.3
J5%,5%% 9.3
3.15t
J4%,5% 10.7
7.95d
7.54t
J 8.1
/
5 b
6 d
7 f
5.07
J1%2% 5.4
4.18t
J2%,3% 4.3
4.33dd
J3%,4% 6.2
3.97m
5.00m e
4.65m
3.66dd
3.58dd
J4%,5%% 5.0
8.00s
7.81s
7.82s
7.75s
7.88s
7.81s
8.03s
7.99dd
8.04d
7.56t
7.40t
7.36t
7.36t
7.32t
7.37m
7.33t
J4%,5% 4.1
J5%,5%% 11.6
4.03dd
5.00m e
5.88dd
J 3.0
5.50m
5.73m
3.92dd
2.07s
2.15s
2.16s
2.16s
2.08s
2.07s
2.01s
2.02s
2.06s
2.13s
2.12s
1.95s
7.46t
J4%,5% 2.1
J4%,5%% 2.3
J5%,5%% 12.9
4.31m
5.28d
J1%,2% 8.1
5.73m
4.31m
8.05dd
7.47dd
3
8 f
4.95s
5.75d
J2%,3% 2.3
5.22dd
J3%,4% 10.2
5.35m
(sextet)
4.33dd
3.47t
7.96d
J 8.4
7.44t
J 7.5
J4%,5% 5.6
J5%,5%% 11.2
4.41s
)
9 f
5.52d
J1%,2% 5.4
5.72m
5.72m
4.50m
4.34d
8.00t
J 7.9
7.50dd
7.45t
J4%,5% 2.9
J5%,5%% 7.8
3.94m
J4%,5% 3.4
J5%,5%% 13.0
3.67m–3.82m
5
10 f
11 b
5.13d
J1%,2% 8.3
4.55dd
J2%,3% 4.2
4.44t
J3%,4% 3.6
4.18dd
4.06dd
1.485
1.474
(Dd 0.011)
8.04m
4.56d
J1%,2% 7.4
3.67m–3.82m
3.67m–3.82m
3.67m–3.82m
3.67m–3.82m
5.07d
J 4.6
(OCH3)
3.23s
8.00d
J 7.8
7.56t
J 7.8
7.56t
J 7.6
5.04d
J 4.0
exchanged
11 d
12 f
4.73d
J1%,2% 3.2
4.75d
4.07t
4.28d
J 1.6
5.30dd
J3%,4% 1.4
4.12m
5.13m
3.66m
4.06m
3.66m
(OCH3)
3.37s
2.09s
7.89s
7.86s
8.00d
J 8.3
8.03d
J 7.9
7.47t
7.46t
7.34t
7.33t
J2%,3% 2.3
4.03dd
J2%,3% 4.9
(OCH3)
3.41s
J1%,2% 5.2
1.96s
a Values for d for the sugar protons are obtained after the addition of CD3CO2D and assigned by 1H decoupling experiments.
b In DMSO-d6 at 500 MHz.
c Overlap between H-3% and H-5%.
d In CDCl3 at 270 MHz.
e Overlap between H-1% and H-4%.
f In CDCl3 at 500 MHz.

56
M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
means for anomeric assignment, especially as
the two anomers were available.
The chemical shift of the anomeric proton
of 4 having a cis arrangement of H-1% and
H-2% was shown more downfield (l 4.69) than
that for 2 (l 4.62), in accord9,12–14 with the b
configuration of 4 and a configuration of 2.
However, the acetyl derivative 8 showed, in
contrast, the anomeric proton more upfield (l
4.95) than that of 6 (l 5.00, overlapped with
H-4%) (Table 1). This small chemical shift dif-
ference between compounds 4 and 2 and 8
and 6 cannot be used safely for anomeric
assignment of this class of compounds on the
basis of the chemical shift criteria.
1
4
Fig. 1. C4(
D) and C1(D) conformations for compounds 2, 4,
6, and 8.
Compound 2 was isolated by Peres et al.15
as a sole C-nucleoside reaction product fol-
lowing our route of acid-catalyzed dehydrative
Regarding the 13C NMR chemical shift data
(Table 2), the anomeric configuration of C-
glycopyranosides can be assigned16–19 by com-
parison of the 13C NMR chemical shifts for
C-1% and C-5% when the two anomers are avail-
able. The g-gauche effect20 predicts that C-1%
and C-5% of a-glycopyranoside anomers will be
shielded with respect to the corresponding car-
bons of b anomers. Compound 2 showed the
anomeric carbon upfield (l 70.2) than that of
cyclization of
zone and subsequent treatment with copper
-lyxopyranosyl
D
-galacto-heptulose phenylosa-
sulfate. It was given the a-
D
1
configuration on the basis of H NMR spec-
tral data and periodate oxidation. The contra-
diction of the rotation results of 2 and 4 with
their coupling constant J1%,2% values demanded
1
the need of other H NMR criteria and other
Table 2
13C NMR chemical shifts (l) for compounds 2–5, 7, 9, 11, and 12
Compound Glycosyl part
2-Phenyl-1,2,3-triazole
Phenyl group
OAc
C-1%
C-2%
C-3%
C-4%
C-5%
CO
CH3
C-4
C-5
C-o
C-m
C-p
C-a
2 a
3 a
4 a
5 a
7 c
70.2 b 67.6
75.3 72.0
74.6 b 70.3
70.2 b 69.6
67.0
60.3
66.2
139.2
139.2
139.3
139.3
135.2
134.8
135.6
136.8
118.2
118.3
118.3
118.2
129.7
129.7
129.8
129.8
127.5
127.6
127.6
127.5
149.5
150.2
148.9
148.7
72.5 80.9
74.6 b 71.2
80.9
74.2
75.1
71.4
72.4 d 71.8 d 60.2
75.3
76.6
62.6
170.6
169.6
169.5
170.7
169.5
169.2
20.80
20.51
20.48
20.8
139.6
139.6
134.2
119.0
129.4
127.8
146.7
9 c
74.2
71.8 d 72.3 d 76.1 d 62.9
20.4 b
20.4 b
134.2
135.2
135.5
118.7
118.3
119.6
129.3
129.7
130.0
127.8
127.7
128.3
145.6
148.1
147.0
11 a
12 c
87.0
85.9
78.0 d 76.7 d 76.1 d 73.2
79.0 d 76.6 d 76.5 d 73.0
(OCH3) 139.1
56.7
171.10
170.30
21.6
21.4
140.4
(OCH3)
58.4
a In DMSO-d6 at 125.7 MHz.
b Overlapped.
c In CDCl3 at 125.7 MHz.
d Interchangeable, uncertain.

M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
57
tation rules, which should be used with care
for anomeric assignment for C-nucleosides as
the optical rotation may be affected with vari-
ation of base moieties.
4 (l 74.6), in accord with the a configuration
of 2 and b configuration of 4. However, the
C-5% resonance of 2 was not in accord with the
g-gauche effect and was shifted more
downfield (l 67.0) than that of 4 (l 66.2).
Nuclear Overhauser effect (NOE) measure-
ments are considered a more reliable tool for
anomeric assignment,21,22 and the results of
NOE studies were in support of the anomeric
configuration of C-glycosides.16,17,23–28 For C-
glycopyranosides the carbons bonded to the
ring oxygen (C-1%, C-5%) place the respective
hydrogens at close proximity on the same face
The b-
D
-lyxofuranosyl anomer 5 was eluted
from the column with 60% aqueous methanol
before the a- -lyxofuranosyl anomer 3 and in
D
lower yield. Periodate oxidation of 3 and 5
consumed one mole of oxidant, in accord with
1
the furanosyl ring structure. The H NMR
spectrum of 3 and 5 (Table 1) showed two
doublets corresponding to two secondary hy-
droxyl groups and one triplet corresponding
to a primary hydroxyl group, all exchangeable
by deuteration, which is in support of the
furanosyl ring structure.
of the pyranose ring. For b- -glycopyranosyl
D
analogs, irradiation of H-1% gives rise to an
NOE effect at H-5%. Irradiation of H-1% for the
acetyl derivative 8 gave rise to 5.7% enhance-
ment of the upfield apparent triplet at l 3.47
corresponding to the geminal axial proton
H-5%% (trans to H-4%). No enhancement was
observed at the lowfield equatorial proton H-
5% (cis to H-4%). Similarly, irradiation of H-5%%
gave rise to 11% enhancement of the anomeric
proton H-1%. This indicates that H-1% and H-5%%
are on the same face of the pyranosyl ring for
The anomeric proton H-1% for 3 was shown
as a doublet at l 4.83 having a coupling
constant J1%,2% 8.1 Hz. Likewise its acetyl
derivative 7 showed the same coupling con-
stant value for the anomeric proton H-1%. Its
O-isopropylidene derivative 10 did not show
the expected decrease in the coupling constant
value due to puckering of the furanosyl ring
having trans arrangement of H-1% and H-2%. In
addition, the difference (Dl) between the
chemical shift of the methyl signals of the
2,2-dimethyldioxolane ring (0.011) is excep-
tionally low for a anomers (50.10).29 This
makes the Dl criterion inapplicable for
anomeric assignment. However, nuclear Over-
hauser effect (NOE) studies on the acetyl
derivative 7 showed upon irradiation at H-1%
enhancement (1.1%) of the multiplet corre-
sponding to the geminal protons H-5%, H-5%%.
Similarly, irradiation of the H-5%, H-5%% multi-
plet resulted in (1.4%) enhancement of (H-1%).
These results indicate the presence of H-1% and
the CH2OH group on the same face of the
compound 8 in a b-
D
configuration with the
4
predominance of the C1( ) conformation.
D
Irradiation of the anomeric proton for com-
pound 2 showed enhancement (5.2%) of the
multiplet at l 3.79 corresponding to the over-
lapped two protons, H-3% and the axial gemi-
nal proton H-5% (cis to H-4%). This axial
geminal proton H-5% showed an unexpected
downfield shift than the equatorial geminal
proton H-5%% (l 3.56) due to the 1,3-syn inter-
action between H-5% and 3%-OH (Fig. 1). No
enhancement was observed at the upfield dou-
blet (l 3.56) corresponding to the shielded
equatorial geminal proton H-5%% (trans to H-
4%). Similarly, irradiation at the multiplet at l
3.79 (H-3%, H-5%), gave 10.6% enhancement of
the anomeric proton (H-1%). This indicates the
presence of H-1% and H-5% on the same face of
furanosyl ring, i.e., the a-
D
configuration. In
addition, the X-ray crystallographic data for 3
(Fig. 2) showed a trans arrangement of H-1%,
H-2% and H-1%, H-4% that unequivocally assigns
the structure and anomeric configuration of 3
the pyranose ring for 2, i.e., an a- configura-
D
as the a- -lyxofuranosyl configuration. There-
D
1
tion with the predominance of the C4( ) con-
D
fore, the large coupling constant (J1%,2% 8.1–8.3
Hz) for compounds 3, 7 and 10 is an excep-
tion to the common coupling constant crite-
rion for anomeric assignment. But, the X-ray
result is an unequivocal and overriding proof
formation. These NOE spectral results
confirmed the anomeric configuration of 2 as
the a-
D
configuration and 4 as the b-
D
configuration, despite the lower specific rota-
tion for 2; ([h]D +4.3° than 4; [h]D 52.3°). This
represents an exception to the Hudson isoro-
for the a-
D
configuration. Further, the bulky
anomeric triazole base moiety should prefer-

58
M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
Fig. 2. ORTEP drawing showing the atom numbering for 4-(a-
D
-lyxofuranosyl)-2-phenyl-2H-1,2,3-triazole (3).
tion rules.11 This represents an additional
exception for the Hudson rotation rules at the
furanosyl anomers.
entially occupy a pseudo-equatorial position,
and this would explain the larger than usual
J1%,2% coupling constant value.
The
D-lyxopyranosyl anomers 2 and 4 were
The anomeric configuration of the lyxofuran-
osyl anomer 5, could not be obtained from the
observed coupling constant value J1%,2% 5.4 Hz.
However, having the two isomers 3 and 5 on
hand, the chemical shift of the anomeric pro-
ton for 3 having a trans arrangement of H-1%
and H-2% showed the anomeric proton more
upfield (l 4.83) than that of 5 (l 5.07), sug-
gesting the cis arrangement of H-1% and H-2%
isolated from the acid-catalyzed dehydrative
cyclization of 1 as the thermodynamic prod-
ucts. Analogous pyranosyl anomers were iso-
lated from the dehydrative cyclization of their
D
-galacto-pentahydroxypentyl
heterocyclic
precursors.30–33 However, analogous kinetic
D
-
lyxofuranosyl products similar to compounds
3 and 5, have not been isolated before as far
as we know from the dehydration of pentahy-
droxypentyl heterocyclic analogs having the
for 5, i.e., the b- -lyxofuranosyl configura-
D
tion. The same correlation was observed for
the acetyl derivatives 7 and 9 (H-1% for 9 was
shown as a doublet at l 5.52 and that for 7 at
l 5.28 suggesting a cis arrangement of H-1%
and H-2% for 9 and trans arrangement for 7).
The b configuration of 5 was confirmed from
the nuclear Overhauser effect of its acetyl
derivative 9. Irradiation of H-1% showed en-
hancement (2.6%) at H-4% (H-2%, H-3% were
overlapped and showed 8.8% enhancement).
Similarly, irradiation at H-4% showed enhance-
ment (3.4%) at H-1%. This indicated the pres-
ence of H-1% and H-4% at the same face of the
D-galacto configuration. Compounds 2 and 3
were obtained from 1 with inversion at C-1%,
whereas 4 and 5 were obtained without inver-
sion. The low yield of 5 has been explained by
its formation through a transition state30 that
is destabilized by steric repulsions34 between
adjacent cis groups.
Periodate oxidation of the byproduct 11
(Scheme 2) consumed one mole of oxidant in
furanosyl ring, i.e., the b-
D
configuration for
9.
The specific rotation for the a anomer 3 was
lower than that for 5 ([h]D in methanol; 3,
[h]D+39.3°; 5, [h]D+72.7°), which is oppo-
site to that predicted by the Hudson isorota-
Scheme 2.

M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
59
Table 3
primary hydroxyl group of 1 in the strongly
acidic methanolic sulfuric acid solution, giving
the intermediate 6-O-methyl derivative ‘A’
(Scheme 2). Subsequent cyclization of ‘A’
through the sterically favored direction gives
the a anomer 11.
X-ray structure determination of compound
3.—The structure and anomeric configuration
of 3 was supported by crystallographic data.
The numbering scheme and overall conforma-
tion of crystals of 3 are shown in Fig. 2.
Single crystals of 3 were grown from a
water–methanol solution and mounted on a
Syntex P21 diffractometer. Lattice parameters
were determined from a least-squares refine-
ment of 15 reflection settings obtained from
an automatic centering routine.
Intensity data were obtained using Mo Ka
radiation monochromatized from a graphite
crystal whose diffraction vector was parallel to
the diffraction vector of the sample. In the
subsequent refinement the function ꢀ w(ꢁFoꢁ−
ꢁFcꢁ)35 was minimized where ꢁioꢁ and ꢁFcꢁ are the
observed and calculated structure factor am-
plitudes. The agreement indicates i=ꢀꢁꢁFo2ꢁ−1/2
ꢁicꢁꢁ/ꢀꢁFoꢁ and Rw=[ꢀ i(ꢁFoꢁ−ꢁFcꢁ)2/ꢀiꢁFoꢁ ]
were used to evaluate the results. The atomic
scattering factors are from the International
Tables for X-ray Crystallography.35
Computations were carried out on an Am-
dahl 5860 computer. The structure was solved
using the direct-methods program MLTTAN78
by Peter Main. Computer programs used dur-
ing the structural analysis were from the
SHELX program package by George Sheldrick,
Institute fu¨r Anorganische Chemie der Uni-
versita¨t Gottingen, Germany. Other programs
used included ORTEP, a thermal ellipsoidal
drawing program by C.K. Johnson.
Summary of crystal data parameters and results for com-
pound 3
Temperature (K)
Space group
294
P21
,
a (A)
4.749(2)
10.572(2)
13.141(5)
645.4(4)
277.3
,
b (A)
,
c (A)
3
,
V (A )
Molecular weight
Z
2
Dcalcd (g/mL)
1.430
0.034×0.280×0.221
Crystal dimensions (mm)
Absorption coefficient (1/cm
1.01)
Scan range (°)
Mo Ka1 −0.8 to Mo
Ka2 +0.9
0.8
Background time ratio
2q (°)
Data collected
Data \3|(I)
Final R
Final Rw
Residual (e/A )
Goodness-of-fit
50
1452
1652
0.051
0.040
0.24
3
,
0.50
1
accord with the furanose ring structure. Its H
NMR spectrum in Me2SO-d6, showed two
doublets at l 5.07 and 5.04 that were ex-
changeable after deuteration, corresponding
to two secondary hydroxyl groups. The
methoxyl group signal was shown at l 3.23, in
accord with 5%-O-methyl furanosyl ring struc-
ture. The observed signal for the anomeric
proton was solvent dependent. In Me2SO-d6, it
was shown as a doublet at l 4.56 having
coupling constant J1%,2% 7.4 Hz. However, in
CDCl3 it was shown as a doublet at l 4.73
having coupling constant J1%,2% 3.2 Hz. The
latter may suggest a trans arrangement of H-1%
and H-2%, i.e., the a-
D
configuration. This
difference in the coupling constant values in
Me2SO-d6 and CDCl3 may be explained by a
change in the conformation of the 5%-O-
methyl furanosyl ring in the two different
solvents. Its acetyl derivative 12 showed the
anomeric proton as a doublet at l 4.75 having
a coupling constant J1%,2% 5.2 Hz that cannot
support the anomeric configuration. Com-
pound 11 may be obtained by 5%-methylation
of the major lyxofuranosyl anomer 3, having
Table 3 lists the crystal data. It contains a
summary of data collection, conditions, and
the least-squares refinement results using an-
isotropic thermal parameters for all non-
hydrogen atoms. Hydrogens were located by
difference Fourier methods and refined with
fixed Ueq values (isotropic temperature fac-
tors) of 0.05. The data were corrected for
absorption. Table 4 shows the fractional
atomic coordinates and final positional
parameters with estimated standard devia-
tions. Anisotropic thermal parameters with
the a-
D
configuration. The formation of 11
can be also explained by methylation of the

60
M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
their estimated standard deviations, bond dis-
tances, and angles are available as supplemen-
tary material, as well as listings of observed
and calculated structure factor amplitudes.
was unequivocally confirmed by the X-ray
crystallography of 3. The b- -lyxofuranosyl
D
configuration for 5 was assigned by compar-
ing the chemical shift values of the anomeric
protons for 3 and 5 and was confirmed by
NOE of the acetyl derivative 9. The furanosyl
anomeric pair 3 and 5 were obtained from the
dehydration of 1 as kinetic products with the
preponderance of the a-furanosyl anomer 3.
Compounds 2 and 3 were obtained from 1
with inversion of the configuration at C-1%,
whereas 4 and 5 were obtained without
inversion.
3. Conclusions
The anomeric configuration of the pyra-
nosyl C-nucleoside anomers 2 and 4 were
determined from their J1%,2% coupling constant
values. Compound 2 was assigned the a-
D
-lyxo-
) conforma-
tion. Compound 4 was given the b- -lyxo-
pyranosyl configuration and 4C1(
) con-
1
pyranosyl configuration and C4(
D
The assignment of the anomeric configura-
tion for the pyranosyl and furanosyl anomers
from their NMR spectral data was not in
agreement with their optical rotation data,
which represents a violation of the Hudson
isorotation rules. The later should be used
with care for C-nucleosides and should be
supported by more than one method for
anomeric assignment.
D
D
1
13
formation. The anomeric H and C chemical
shift values supported this assignment. This
was confirmed by the NOE measurements for
compound 2 and the acetyl derivative 8. The
pyranosyl anomers 2 and 4 are formed from
the acid-catalyzed dehydration of 1 as thermo-
dynamic products with the preponderance of
the a-pyranosyl anomer 2.
The anomeric configuration of the furanosyl
anomers 3 and 5 could not be assigned from
their J1%,2% coupling constant values. The NOE
of the acetyl derivative 7 was in accord with
4. Experimental
General.—Melting points were determined
with a Fisher–Johns instrument. Evapora-
tions were performed under diminished pres-
sure below 60 °C. Thin-layer chromatography
(TLC) was conducted on Silica Gel (Kieselgel
G, Merck) with solvent A (3:1 benzene–
EtOH), B (10:1 CHCl3–MeOH), C (2.5:3
EtOAc–hexane), D (3:1 EtOAc–hexane), or E
(5:1 toluene–EtOH). Compounds were de-
tected under short UV light at 254 nm. IR
spectra were recorded with a Perkin–Elmer
Lambda 48 instrument. Optical rotations and
ORD measurements were obtained at 209
2 °C with a Perkin–Elmer 241 Polarimeter 10
the a- -lyxofuranosyl configuration, which
D
Table 4
Fractional atomic coordinates
Atom
x
y
z
Ueq
O-1
C-2
C-3
O-4
C-5
O-6
C-7
O-8
0.2157(8)
0.191(18)
0.266(18)
0.237(18)
0.108(18)
0.402(18)
0.438(18)
0.385(18)
0.485(18)
0.261(18)
0.182(18)
0.057(18)
0.026(18)
0.131(18)
0.228(18)
0.140(18)
0.246(18)
0.253(18)
0.156(18)
0.051(18)
0.041(18)
0.0270(3)
−0.0546(4)
−0.1566(5)
−0.1876(5)
−0.0166(4)
−0.0322(4)
0.0991(4)
0.1622(3)
0.1243(4)
0.2064(4)
0.2349(5)
0.3148(4)
0.3330(3)
0.2697(3)
0.4194(4)
0.4321(5)
0.5177(5)
0.5891(5)
0.5732(5)
0.4897(5)
0.038
0.032
0.038
0.044
0.031
0.039
0.030
0.038
0.030
0.029
0.041
0.043
0.033
0.033
0.035
0.041
0.051
0.051
0.055
0.046
0.2940(13)
0.0997(15)
0.1331(16)
0.2816(13)
−0.0128(11)
0.4142(12)
0.3607(8)
0.2830(12)
0.4674(11)
0.4310(16)
0.6384(12)
0.7927(9)
0.6990(10)
1.0320(12)
1.1999(14)
1.4272(14)
1.4858(15)
1.3127(17)
1.0827(15)
1
C-9
cm, 1 mL microcell. H NMR spectra were
C-10
C-11
N-12
N-13
N-14
C-15
C-16
C-17
C-18
C-19
C-20
recorded with a General Electric 500 MHz,
Nicolet 470 MHz, Bruker WP 270 SY MHz,
and Bruker AM 500 MHz spectrometers using
tetramethylsilane as an internal standard. 13C
NMR spectra were recorded with the General
Electric 500 instrument at 125.0 MHz or the
Bruker 500 instrument at 125.7 MHz. Assign-
1
ment of peaks was verified by H–13C COSY
experiments. Chemical shifts in l ppm were
referenced to CDCl3 (77.7), Me2SO-d6 (39.50),

M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
61
of periodate was consumed (based on mol wt
194).
or tetramethylsilane Me4Si (TMS) as internal
standards. NOE experiments were obtained
using the standard Bruker NOEDIFF micro-
program. The anomeric protons were preirra-
diated for 15 scans at 35 dB attenuation of the
low power decoupler (:0.4 W). This was
altered every eight scans with off-resonance
irradiation for the spectra that were to be
subtracted. Mass spectra were recorded with a
Finnigan 4021 low-resolution EI–CI spec-
trometer at 70 eV. High-resolution mass spec-
tra were recorded with a VG analytical model
70-250 spectrometer. Combustion analyses
were performed in the Department of Chem-
istry, Cairo University, Cairo, Egypt and M-
H-W Laboratories, Phoenix, AZ, USA.
4-(2,3,4-Tri-O-acetyl-h- -lyxopyranosyl)-2-
D
phenyl-2H-1,2,3-triazole (6).—Compound 6
was prepared as described previously10 and
was identical with the authentic product by 1H
1
NMR spectroscopy. For H NMR spectral
data see Table 1.
4-(i- -Lyxopyranosyl)-2-phenyl-2H-1,2,3-
D
triazole (4).—Compound 4 was isolated from
the Dowex resin column chromatography of
the syrup obtained after the partial separation
of 2 and eluted with 60% aq MeOH after
elution of 2. Identical fractions were collected
and evaporated to dryness giving a precipitate;
yield 80 mg. The product was recrystallized as
colorless needles mp 203–204 °C (Lit10 mp
204 °C); [h]2D2+52.3° (c 0.52, MeOH); ORD
4-(h-
D
-Lyxopyranosyl)-2-phenyl-2H-1,2,3-
-galacto-
triazole (2).—A suspension of 4-(
D
(MeOH):
[ƒ]589 +144.9°,
[ƒ]578+152.9°;
pentitol)-1-yl-2H-1,2,3-triazole (1)36 (3 g), in
20% methanolic sulfuric acid (50 mL) (made
by adding one volume of concd H2SO4 to four
volumes of MeOH) was refluxed on a water
bath for 10 h. Complete dissolution was ob-
tained after 5 h, TLC indicated disappearance
of the starting material after 8 h. The soln was
diluted with water (20 mL), MeOH was evap-
orated under reduced pressure, and the soln
was continuously extracted with CHCl3. The
CHCl3 layer was separated, washed with
water, NaHCO3, and water, then dried over
anhyd sodium sulfate. The CHCl3 soln was
concd into a small volume, giving colorless
needles of 2 (yield 800 mg). The mother liquor
was evaporated to a syrup which was chro-
matographed on a column (2×46 cm) of
Dowex-1 X 8 (OH−) ion-exchange resin (200–
400 mesh) and eluted with 30, 60, and 90% aq
MeOH. Fractions (15 mL) at a rate of 1.5
mL/min were collected. The 60% aq MeOH
afforded a further crop of 2; 150 mg, total
yield of 2, 950 mg (34%). It was recrystallized
from MeOH–benzene as colorless needles mp
129–130 °C (Lit10 mp 130–131 °C). Rf 0.34
(A); [h]2D2+4.3° (c 2.4, MeOH); ORD
[ƒ]546+179.2°; [ƒ]436+357.9°; [ƒ]365+728.5°;
Rf 0.31 (A) (for H and 13C NMR data see
1
Tables 1 and 2); periodate consumption 1.98
mol equiv.
4 - (Tri - O - acetyl - i -
D
- lyxopyranosyl) - 2-
phenyl-2H-1,2,3-triazole (8).—Compound 8
was prepared as described previously.10 It
1
showed identical H NMR spectral measure-
1
ments. For H NMR spectral data see Table
1.
4-(h- -Lyxofuranosyl)-2-phenyl-2H-1,2,3-
D
triazole (3).—Compound 3 was separated
from the resin column by elution with 60% aq
MeOH after elution of 4; yield 280 mg, mp
138–140 °C; Rf 0.32 (E); [h]D +39.3° (c 1.08,
MeOH); ORD (MeOH): [ƒ]589+108.8°,
[ƒ]578+113.0°; [ƒ]5416+127.4°; [ƒ]436+206.4°;
13
[ƒ]365+308.3° (for H and C NMR data see
Tables 1 and 2); EIMS: m/z 278 (10, M+1),
277 (4, M), 260 (6, M−OH), 259 (38, M−
H2O), 200 (23, M−Ph), 188 (38, M−89), 187
(17, MH−PhN), 186 (7, M−PhN), 175 (18,
BCH2OH), 174 (100, BCHOH), 173 (8,
BCHO), 158 (20, BCH2), 92 (13, PhNH), 91
(36, PhN), and 77 (27, Ph); periodate con-
sumption 1.09 mol equiv (based on mol wt
277). Anal. Calcd for C13H15N3O4: C, 55.86;
H, 5.66; N, 15.19. Found: C, 56.30; H, 5.45;
N, 15.15.
(MeOH):
[ƒ]589+11.9°,
[ƒ]578+12.4°;
[ƒ]546 +14.7°; [ƒ]436 +30.5°; [ƒ]365+63.6°
1
(for H and 13C NMR see Tables 1 and 2);
periodate consumption 2.00 mol equiv (based
on mol wt 277). In a control experiment using
4-(2,3,4-Tri-O-acetyl-h- -lyxofuranosyl)-2-
D
phenyl-2H-1,2,3-triazole (7).—Compound 3
(38 mg) was dissolved in pyridine (1 mL) and
treated with Ac2O (1 mL), and the mixture
methyl h-
D
-mannopyranoside under the same
conditions for all compounds, 2.04 mol equiv

62
M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
[h]2D2+72.7° (c 1.08, MeOH); ORD (MeOH):
was kept for 24 h at rt. The mixture was
evaporated to dryness, and traces of pyridine
were removed by spin coevaporation with tol-
uene and CHCl3. The resulting syrup was
purified by chromatography on a short
column (1×10 cm) of silica gel and eluted
with solvent (C): colorless syrup; yield 40 mg;
[ƒ]589+201.0°, [ƒ]578+211.0°; [ƒ]546+244.6°;
KBr
[ƒ]436+472.0°; [ƒ]365 +950.0°;
w
3340
max
(OH), 1605 (CꢁN), and 1500, 750 (Ph) cm−1
(for H and 13C NMR data see Tables 1 and
1
2); EIMS: m/z: 278 (2, M+1), 277 (3, M),
200 (24, M−Ph), 188 (24, M−89), 187 (7,
MH−PhN), 175 (13, BCH2OH), 174 (100,
BCHOH), 173 (5, BCHO), 158 (10, BCH2), 92
(9, PhNH), 91 (34, PhN), and 77 (23, Ph);
periodate consumption 1.066 mol equiv. Anal.
Calcd for C13H15N3O4: C, 56.30; H, 5.45; N,
15.15. Found: C, 56.38; H, 5.63; N, 15.46.
1
Rf 0.81 (E) (for H and 13C NMR data see
Tables 1 and 2); EIMS: m/z 404 (0.2, M+1),
403 (0.1, M), 344 (4, M−OAc), 343 (17,
M−AcOH), 283 (3, M−2 AcOH), 242 (6,
M−2 OAcꢀAc), 241 (29, M−OAcꢀAcOHꢀ
Ac), 224 (66, M−2 AcOHꢀOAc), 188 (5,
BHCH2CHO), 187 (7, BCH2-CHO), 174 (13,
BCHOH), 173 (4, BCHO), 172 (9, BCO), 86
(19, M−BCHOAcꢀOAcꢀCH2CO), 84 (31,
M−BCH2OAcꢀAcOHꢀCH3CO), 77 (8, Ph),
and 43 (100, CH3CO); HRCIMS (isobutane):
Found 404.1453; Calcd for C19H22N3O7
404.1458.
4-(2,3,5-Tri-O-acetyl-i- -lyxofuranosyl)-2-
D
phenyl-2H-1,2,3-triazole (9).—Compound 5
(10 mg) was acetylated with a mixture 1:1 of
pyridine–Ac2O (2 mL) for 12 h at rt and
processed as described for 7 to give colorless
1
13
syrup Rf 0.73 (E) (for H and C NMR data
see Tables 1 and 2); EIMS: m/z 404 (2, M+
1), 403 (9, M), 343 (8, M−AcOH), 283 (3,
M−2 AcOH), 242 (7, M−2 OAcꢀAc), 241
(25, M−AcOHꢀOAcꢀAc), 224 (44, M−2
AcOHꢀOAc), 200 (8), 187 (7, BCH2CHO),
174 (20, BCHOH), 173 (5, BCHO), 91 (9,
PhN), 77 (8, Ph), and 43 (100, CH3CO);
HREIMS: Found 403.1392; Calcd for
C19H21N3O7 403.1379.
4-(2,3-O-Isopropylidene-h- -lyxofuranosyl)-
D
2-phenyl-2H-1,2,3-triazole (10).—Compound
3 (50 mg) was stirred in a soln of 2,2-
dimethoxypropane (5 mL) and a catalytic
amount of p-toluenesulfonic acid (4 mg) for 1
h at rt. TLC indicated the reaction to be
complete. The mixture was poured into satd
aq NaHCO3 solution and extracted with
CHCl3. The CHCl3 soln was dried over anhyd
magnesium sulfate. The organic extract was
filtered, evaporated to dryness, and the residue
was recrystallized from petroleum ether (40–
60 °C) to give colorless needles; yield 23 mg;
4 - (5 - O - Methyl - h -
phenyl-2H-1,2,3-triazole
D
- lyxofuranosyl) - 2-
(11).—Compound
11 was eluted from the resin column with 90%
MeOH and recrystallized from dilute MeOH;
yield 149 mg; mp 174–176 °C; Rf 0.42 (A);
1
mp 120–121 °C; Rf 0.37 (C) (for H and 13C
[h]2D2+74.3° (c 0.53, MeOH), w
3340 (OH),
KBr
max
1595 (CꢁN), and 1495, 740 (Ph) cm−1 (for H
and 13C NMR data see Tables 1 and 2);
EIMS: m/z 291 (1, M), 189 (19,
BHCH2CHOH), 188 (100, BCH2CHOH), 91
(12, PhN), and 77 (10, Ph); periodate con-
sumption 1.01 mol equiv. Anal. Calcd for
C14H17N3O4: C, 57.72; H, 5.88; N, 14.43.
Found: C, 57.62; H, 5.91; N, 14.33 (mol wt
291).
1
NMR data see Tables 1 and 2); EIMS: m/z
317 (5, M), 302 (5, M−CH3), 259 (4, M−
CH3COCH3), 200 (10, M−CH3COCH3−
CH2OHꢀH2O), 187 (26, BCH2CHO), 174 (15,
BCHOH), 173 (5, BCHO), 172 (4, BCO), 91
(23, PhN), 77 (24, Ph), and 43 (100, CH3CO);
HREIMS: Found [M+] 317.1376; Anal. Calcd
for C16H19N3O4 317.1376. Calcd for
C16H19N3O4: C, 60.56; H, 6.04; N, 13.24.
Found: C, 60.42; H, 6.09; N, 13.20.
4-(2,3-Di-O-acetyl-5-O-methyl-h- -lyxo-
D
4 - (i -
D
- Lyxofuranosyl) - 2 - phenyl - 2H-
furanosyl)-2-phenyl-2H-1,2,3-triazole (12).—
Compound 11 (10 mg) was acetylated with a
mixture 1:1 pyridine–Ac2O (2 mL) for 24 h at
rt. The mixture was processed as described for
1,2,3-triazole (5).—Compound 5 was eluted
by 60% aq MeOH from the resin column after
the separation of compounds 2, 4 and 3, re-
spectively. It was recrystallized from CHCl3–
petroleum ether (bp 60–80 °C) as colorless
needles; yield 10 mg; mp 86–87°; Rf 0.31 (E),
1
9 to give a colorless syrup; Rf 0.46 (C) (for H
and 13C NMR data see Tables 1 and 2); CIMS
(isobutane): 377 (4, MH2), 376 (17, MH), 345

M.A.E. Sallam et al. / Carbohydrate Research 330 (2001) 53–63
63
9. Sallam, M. A. E. J. Chem. Soc. 1982, 557–562, and
references cited therein.
(6, MH−OCH3), 344 (32, M−OCH3), 285
(18, M−OCH3−OAc), 284 (100, M−
OCH3−AcOH), 226 (17, M−OCH3−2
OAc), 188 (22, BCH2CHOH), 187 (22, BCH-
CHOH), 174 (4, BCHOH), and 77 (2, Ph);
EIMS: m/z 375 (1, M), 284 (1), 189 (13), 188
(100, BCH2CHOH), 187 (30), 77 (5, Ph), and
43 (48, CH3CO); HREIMS: Found: 376.1517;
Calcd for C18H22N3O6: 376.1509.
10. Sallam, M. A. E. Carbohydr. Res. 1980, 85, 93–105.
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5. Supplementary material
Full crystallographic details, excluding
structure features, have been deposited with
the Cambridge Crystallographic Data Centre,
position number CCDC 149569. These data
may be obtained upon request from The Di-
rector, CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK (Tel.: +44-1223-336408; fax:
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