Regiochemistry of epoxide ring opening in methyl 2,3-anhydro-4-azido-4- deoxy-α- and β-L-lyxopyranosides

Article abstract of DOI:10.1016/j.carres.2005.06.006

Methyl 2,3-anhydro-4-O-methanesulfonyl-α-D-ribopyranoside (12) was prepared through a new six-step sequence starting from D-arabinose. Chemical behaviour of 12 was further studied under solvolytic conditions and in the presence of azide anion as a nucleophile. Factors governing the regiochemistry of epoxide ring opening are briefly discussed.

Full text of DOI:10.1016/j.carres.2005.06.006

Carbohydrate
RESEARCH
Carbohydrate Research 340 (2005) 1866–1871
Note
Regiochemistry of epoxide ring opening in methyl
2,3-anhydro-4-azido-4-deoxy-a- and b-L-lyxopyranosides
a
a
Velimir Popsavin,a, Goran Benedekovic, Mirjana Popsavin,
*
´
Bojana Sreco and Dejan Djokovic
a
b
´
´
a
´
Department of Chemistry, Faculty of Sciences, University of Novi Sad, Trg D. Obradovica 3, 21000 Novi Sad, Serbia and Montenegro
bFaculty of Chemistry, University of Belgrade, Studentski trg 16, PO Box 158, 11001 Belgrade, Serbia and Montenegro
Received 18 March 2005; received in revised form 31 May 2005; accepted 11 June 2005
Available online 1 July 2005
Abstract—Methyl 2,3-anhydro-4-O-methanesulfonyl-a-D-ribopyranoside (12) was prepared through a new six-step sequence start-
ing from D-arabinose. Chemical behaviour of 12 was further studied under solvolytic conditions and in the presence of azide anion
as a nucleophile. Factors governing the regiochemistry of epoxide ring opening are briefly discussed.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: 2,3-Anhydro-ribopyranosides; 2,3-Anhydro-lyxopyranosides; Epoxide ring opening; Regioselectivity; Azido sugars
The epoxide ring opening of anhydroglycosides as ver-
satile intermediates for reactions with a wide range of
nucleophiles is a well-established reaction. Factors lead-
ing to stereo- and regioselectivity in carbohydrate epox-
ide ring opening have been frequently investigated.1,2
Only few examples of nucleophilic ring opening reac-
tions in the series of 2,3-anhydrolyxopyranosides have
been reported,3 including our recent work directed to
the conversion of the epoxide 2 to the diazido derivative
3 (Scheme 1), which was used as a model compound in
the recent synthesis of (+)-oxybiotin.4 Thus, the nucleo-
philic displacement of the mesyloxy group in 1, with so-
dium azide in N,N-dimethylformamide at 140–145 ꢁC,
occurred with concomitant regioselective epoxide ring
opening in the intermediate 2 to afford the C-3 and C-
2 substituted sugars 3 and 4 in the ratio 13:1. In this
work, we chose to investigate the similar ring opening
reaction of methyl 2,3-anhydro-4-azido-4-deoxy-b-L-
lyxopyranoside (13, Scheme 2), in order to provide an
access to divergent intermediates suitable for prepara-
tion of both (+)-oxybiotin and/or the corresponding
diamino sugars of potential biological interest. The
preparation of the b-L-lyxopyranoside 13 was first
attempted starting from 3,4-O-isopropylidene-D-arabi-
nose5 (5).
Treatment of 5 with mesyl chloride and triethylamine
in dry dichloromethane gave the crystalline glycosyl
chloride 6 as the only reaction product. Although com-
pound 6 could be stored at ꢀ20 ꢁC for weeks without
change, it tended to decompose on prolonged standing
at room temperature. Hence, the intermediate 6 was
immediately treated with silver oxide in methanol to
afford the known6 a-D-arabinopyranoside 7 (51%) ac-
companied with a minor amount of the corresponding
b-anomer 8 (8%). Hydrolytic removal of the isopropy-
lidene protective group in 7 gave the expected diol 9
(88%). In this way, the intermediate 9 was prepared in
an overall yield of 39.5% calculated to the starting com-
pound 5. However, when the last three-step sequence
was carried out without purification of the intermediates
6 and 7, the desired product 9 was obtained in a consid-
erably higher overall yield (56% from 5). Treatment of 9
with sodium methoxide in boiling methanol gave the
known6 epoxide 11, which was subsequently converted
to the corresponding 4-O-mesyl derivative 12 by treat-
ment with mesyl chloride and triethylamine in dichloro-
methane (89% from 9).
*
Corresponding author. Tel.: +381 21 6350 122; fax: +381 21 454
065; e-mail: popsavin@ih.ns.ac.yu
0008-6215/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2005.06.006

V. Popsavin et al. / Carbohydrate Research 340 (2005) 1866–1871
1867
Scheme 1. Reagents and conditions: (a) NaN3, DMF, 140–145 ꢁC, 3.5 h, 51% of 3, 4% of 4.
Scheme 2. Reagents and conditions: (a) MsCl, Et3N, CH2Cl2, ꢀ10 ꢁC, 1 h for 5, 88% of 6, 1.5 h for 11, 93% of 12; (b) Ag2O, MeOH, 0 ꢁC, 0.5 h, then
rt, 20 h, 51% of 7, 8% of 8; (c) 9:1 TFA–H2O, rt, 0.5 h, 88%; (d) NaOMe, MeOH, 55–60 ꢁC, 1 h, 96%; (e) NaN3, DMF, 95 ꢁC, 1 h, 32% of 13, 16% of
14; (f) NaN3, DMF, 105 ꢁC, 21 h, 48% of 14, 8% of 15; (g) Me3SiN3, BF3ÆOEt2, CH2Cl2, rt, 23 h, 40% of 14, 8% of 15.
We further investigated the possibility of conversion
of the new methyl 2,3-anhydro-4-O-mesyl-a-D-ribopyr-
anoside (12) into the corresponding 4-azido-4-deoxy-b-
L-lyxopyranoside 13. However, the reaction of the a-
anomer 12, under the same conditions as for methyl
2,3-anhydro-4-O-mesyl-b-D-ribopyranoside,4 was not
so straightforward and afforded a mixture of several
products with the expected 4-azido derivative 13
(32%)ꢀ being a dominant component. A minor amount
of the 2,4-diazido derivative 14 (16%) was also isolated
from the reaction mixture, thus indicating that the
nucleophilic displacement of the mesyloxy group in 12
has occurred with concomitant regioselective epoxide
ring opening in the intermediate 13. Indeed, when the
last reaction was carried out at 105 ꢁC for 21 h, the
2,4-disubstituted product 14 was isolated in 48% yield
along with a minor quantity of the 3,4-diazido derivative
15 (15%). In the next step, we have focused on the ring
opening of epoxide 13 by Me3SiN3/BF3ÆOEt2. This re-
agent system sometimes gives a different regioselectivity
with respect to NaN3 in DMF, as observed recently in
the ring opening reaction of benzyl 2-acetamido-3,4-
anhydro-2,6-dideoxy-a-L-talopyranoside.7
However,
the reaction of 13 with Me3SiN3/BF3ÆOEt2, in CH2Cl2
(rt, 23 h), also afforded the 2,4-diazido sugar 14 as a
major product (40%), whereas its 3,4-regioisomer 15
was again isolated as a minor reaction product (8%).
Obviously, the epoxide ring opening in both 2 and 13
occurs according to Furst–Plattner rule, to afford pre-
¨
dominantly the trans-diaxial products 3 and 14. These
reactions show the same regiochemistry as the ring
opening in methyl 2,3-anhydro-4-azido-4-deoxy-pento-
pyranosides with sodium hydroxide earlier observed by
Dick and Jones.8 The major reaction products 3 and
ꢀ An attempted preparation of 13 via the triflic analogue of 12 failed,
since the corresponding triflic ester rapidly decomposes at room
temperature turning into a variety of products.

1868
V. Popsavin et al. / Carbohydrate Research 340 (2005) 1866–1871
Scheme 3. Regiochemistry of epoxide ring opening in a- (2) and b-anomer 13: (a) nucleophilic attack at C-2 from an axial direction; (b) axially
directed attack at C-3; (c) formation of trans-diaxial products followed by conformational interconversion.
14 might be formed via the chair-like transition states 3a
and 14a (Scheme 3) that are obviously more favourable
than 4b and 15a (that lead towards the minor regioisom-
ers 4 and 15), presumably due to the anomeric effect
caused by the equatorially oriented C-1 methoxy
groups.1b,9
J2,3 = 9.4 and J3,4 = 8.9 Hz. These values clearly prove
that H-1, H-2, H-3 and H-4 are all axially oriented,
and are consistent with the b-L-xylo configuration. The
major conformer of 14, compatible with the observed
1
vicinal couplings, is thus C4. The following coupling
constants were used to determine the stereochemistry
of the minor product in b-series (15): J1,2 = 3.6,
J2,3 = 10.0 and J3,4 = 3.5 Hz. The first two values clearly
prove that H-2 and H-3 are both axially oriented, and
that H-1 and H-2 are in an equatorial–axial relationship.
Finally, the coupling constant J3,4 = 3.5 Hz is consistent
with an axial–equatorial arrangement of H-3 and H-4.
This is possible only if 15 is of the b-L-arabino configu-
ration. The predominant conformer of 15, compatible
The stereochemistry of ring-opened products was
resolved by a careful examination of their 1H NMR
spectra, especially the coupling constants between the
relevant protons. To determine the stereochemistry of
the major product 3 in the a-series, the coupling con-
stants J1,2, J2,3 and J3,4 were used. J1,2 has a value of
7.2 Hz, suggesting a diaxial arrangement of H-l and
H-2. Both H-2 and H-3 are double doublets with vicinal
couplings of 7.2, 9.8 and 9.8, 3.8 Hz, respectively. Thus,
therefore, J2,3 is 9.8 Hz and J3,4 is 3.8 Hz. The first value
immediately leads to the conclusion that both H-2 and
H-3 are axially positioned and that H-3 and H-4 bear
an axial–equatorial relationship. All these observations
can be accounted for satisfactorily only when 3 is an
4
with the observed coupling constants, is thus C1. As
in the case of 3 and 4, positions of the anomeric proton
1
signals in the corresponding H NMR spectra addition-
ally proved that both the products 14 and 15 preferen-
1
4
tially occupy C4 and C1 conformations, respectively.
Namely, the anomeric proton of 14 appears in the spec-
trum at significantly higher field (d 4.14 ppm) with re-
spect to H-1 of 15 (d 4.78 ppm). These data are
consistent with an axial position of H-1 in 14, as well
as an equatorial orientation of H-1 in 15.
4
a-L-arabinopyranoside derivative in the C1 conforma-
tion. Likewise, in the minor product 4, the coupling
constants of significance are J1,2 = 3.5, J2,3 = 10.1 and
J3,4 = 8.9 Hz. Once again, these values clearly prove that
H-2, H-3 and H-4 are all axially oriented, and that H-1
and H-2 are in an equatorial–axial relationship. This is
possible only if 4 is of the a-L-xylo configuration. The
major conformer of 4, compatible with the observed
In summary, it has been confirmed that the regio-
chemistry of epoxide ring opening in methyl 2,3-anhy-
dro-4-azido-4-deoxy-a- and b-L-lyxopyranosides 2 and
13 with azide anion does depend upon their anomeric
configuration. Thus, the a-anomer 2 under solvolytic
conditions and in the presence of azide anion as a nucle-
ophile predominantly gave the C-3 substituted sugar 3,
the similar ring opening reaction of b-anomer 13 affor-
ded the C-2 substituted derivative 14 as the main reac-
tion product. In addition, both diazido derivatives 3
and 14 represent suitable intermediates for preparation
of the corresponding amino sugars of potential biologi-
cal importance, while the regioisomer 3 represents, a
1
coupling constants, is thus C4. The anomeric proton
signal in the spectrum of 4 is shifted downfield (d
4.78 ppm) with respect to the H-1 signal in the spectrum
of 3 (d 4.13 ppm). These data additionally prove that the
anomeric proton in 3 occupies an axial position, oppo-
site to the regioisomer 4 whose H-1 is equatorially
oriented.
1H NMR spectrum of the major product in b-series
(14) shows the following coupling constants: J1,2 = 7.5,

V. Popsavin et al. / Carbohydrate Research 340 (2005) 1866–1871
1869
postulated intermediate in an alternative approach to
(+)-oxybiotin, a biologically active analogue of natural
biotin.
1.1.1. Methyl 3,4-O-isopropylidene-2-O-methanesulfonyl-
a-D-arabinopyranoside (7). To a stirred and cooled
(ꢀ10 ꢁC) soln of 55 (1.15 g, 6.05 mmol) in a mixture of
dry CH2Cl2 (12 mL) and Et3N (2.53 mL, 18.15 mmol)
was added dropwise
a soln of MsCl (1.17 mL,
1. Experimental
15.12 mmol) in CH2Cl2 (3.5 mL). The mixture was
stirred for 1 h at ꢀ10 ꢁC, then diluted with CH2Cl2
(20 mL) and washed successively with cold (+4 ꢁC) aq
5% HCl (2 · 40 mL) and 1% NaHCO3 (20 mL). Organic
phase was dried and evaporated to a pale yellow solid.
Flash column chromatography (CH2Cl2) gave pure 6
(1.52 g, 88%). Recrystallization from CH2Cl2–hexane
1.1. General methods
Melting points were determined on a Buchi 510 appara-
¨
tus and were not corrected. Optical rotations were
measured on a Polamat A (Zeiss, Jena) polarimeter.
IR spectra were recorded with a Specord 75 IR spectro-
photometer. NMR spectra were recorded on a Bruker
AC 250 E instrument and chemical shifts are expressed
in ppm downfield from tetramethylsilane. The NMR
data are presented in Tables 1–3. Low resolution mass
spectra were recorded on Finnigan-MAT 8230 (CI)
and VGAutoSpec (FAB) mass spectrometers. High res-
olution mass spectra were taken on a Micromass LCT
KA111 spectrometer. TLC was performed on DC
Alufolien Kieselgel 60 F254 (E. Merck). Flash column
chromatography was performed using ICN silica 32–
63. All organic extracts were dried with anhydrous
Na2SO4. Organic solutions were concentrated in a ro-
tary evaporator under diminished pressure at a bath
temperature below 35 ꢁC.
gave colourless crystals, mp 130 ꢁC (decomposition),
23
½aŠ ꢀ202.9 (c 1.0, CHCl3), Rf 0.40 (CH2Cl2); lit.4
D
23
D
mp 129–131 ꢁC (decomposition), ½aŠ ꢀ205.3 (c 1.0,
CHCl3). To a stirred and cooled (0 ꢁC) soln of 6 (2.20 g,
7.67 mmol) in abs MeOH (20 mL) was added Ag2O
(1.90 g, 8.20 mmol). The suspension was stirred at 0 ꢁC
for 30 min, then allowed to warm to room temperature
and then stirred for the next 20 h. The reaction mixture
was diluted with EtOAc, filtered through a Celite pad
and evaporated. Flash column chromatography (1:1 ben-
zene–EtOAc) of the residue first gave pure b-anomer 8
(0.171 g, 8%), which upon crystallization from CH2Cl2–
23
D
hexane gave colourless needles, mp 138 ꢁC, ½aŠ ꢀ191.5
23
(c 0.5, CHCl3), Rf 0.29 (CH2Cl2); lit.6 mp 138–139 ꢁC,
½aŠ ꢀ187 (c 1.1, CHCl3). IR (KBr): mmax 1400–1370 (as.
D
Table 1. 1H NMR resonances in compounds 7–15 (in CDCl3)
Compound
Chemical shifts (ppm)
H-5a H-5b
3.79 (dd) 4.16 (dd)
3.93 (dd) 4.02 (d)
H-1
H-2
H-3
H-4
Other signals
7
4.24 (d)
4.85 (d)
4.45 (t)
4.60 (dd)
4.19 (t)
4.35 (dd)
4.26 (m)
4.28 (dd)
1.34 and 1.53 (CMe2), 3.10 (MeSO2), 3.47 (OMe)
1.37 and 1.58 (CMe2), 3.16 (MeSO2), 3.43 (OMe)
8
9a
10
11
12
13
14
15
4.46–4.57b 4.46–4.57b 3.87–4.01b 4.06 (br s) 3.71 (d)
3.87–4.01b 3.30 (MeSO2), 3.60 (OMe)
3.86b
3.06–3.67b 3.06–3.67b 2.67 (OH), 3.43 (OMe)
4.95 (d)
4.79 (d)
4.83 (d)
4.95 (d)
4.14 (d)
4.78 (d)
4.78 (dd)
3.06–3.67b 3.06–3.67b 4.04 (m)
3.55 (dd) 3.59 (dd) 5.03 (ddd) 3.62 (dd)
3.40–3.46b 3.40–3.46b 3.55–3.65b 3.55–3.65b 4.00 (dd)
3.29 (dd) 3.40 (ddd) 3.56 (ddd) 3.15 (dd) 4.01 (dd)
3.97 (ddd) 3.75–3.88b 3.75–3.88b 3.69 (dd)
4.06b
4.06b
3.75 (dd)
3.15 (MeSO2), 3.60 (OMe), 3.86b (OH), 4.06b (OH)
3.77 (dd)
3.10 (MeSO2), 3.44 (OMe)
3.47 (OMe)
3.56 (OMe)
3.75–3.88b 2.31 (OH), 3.46 (OMe)
a In D2O.
b Group of signals.
Table 2. 1H vicinal couplings in compounds 7–15 (in CDCl3)
Compound
Coupling constants (Hz)
4,5a 4,5b
3.1 2.5
2.5
<1
1,2
2,3
7.6
3,4
6.0
5a,5b
Other coupling constants
7
7.6
3.4
13.4
3.4
8
7.7
9.3
4.2
5.4
3.5
0
9a
10
11
12
13
14
15
1.9
13.0
12.6
3.6
3.4
2.8
2.8
7.5
3.6
<1
1.6
J4,OH = 8.7 Hz
1.7
6.0
1.7
9.8
2.0
5.3
10.8
12.4
11.8
12.7
9.4
10.0
8.9
3.5
10.7
2.3
J2,OH = 10.1 Hz
a In D2O.

1870
V. Popsavin et al. / Carbohydrate Research 340 (2005) 1866–1871
Table 3. 13C NMR data of compounds 7–15 (in CDCl3)
Compound
Chemical shifts (ppm)
C-1
C-2
C-3
C-4
C-5
OMe
Other signals
7
100.41
97.97
104.30
100.54
94.55
93.87
94.41
103.51
99.04
82.04
79.50
84.17
80.92
54.77b
54.83
51.13
66.08
68.59
76.37
73.08
73.01
72.12
53.28b
50.38
49.75
74.09
61.72b
73.40
73.92
71.53
69.08
64.59
72.16
53.81
60.84
60.18
62.71
58.21
69.10
65.37
60.36
56.55
58.99
63.76
60.20b
56.36
55.83
59.98
57.96
55.85
55.95
55.82
57.15
55.70
25.93 and 27.49 (CMe2), 38.91 (MeSO2), 110.69 (CMe2)
26.07 and 27.95 (CMe2), 38.57 (MeSO2), 109.67 (CMe2)
41.25 (MeSO2)
8
9a
10
11
12
13
14
15
40.43 (MeSO2)
38.72 (MeSO2)
a In D2O.
b Assignation might be reversed.
SO2), 1190 (sym. SO2). FAB MS: m/z 304 (M+ꢀH+Na),
283 (M++H), 251 (M+ꢀOMe). Pure a-anomer 7 (1.10 g,
51%), was then eluted, which crystallized from CH2Cl2–
(sym. SO2). FAB MS: m/z 265 (M++Na), 243
(M++H), 211 (M+ꢀOMe). Further elution gave pure 9
23
(3.57 g, 56%), which crystallized from EtOAc–hexane
as colourless needles, mp 115–116 ꢁC, ½aŠ ꢀ16.0 (c
hexane as colourless needless, mp 143–144 ꢁC,
D
23
½aŠ ꢀ34.0 (c 0.5, CHCl3), Rf 0.26 (CH2Cl2); lit.6 mp
0.5, H2O), Rf 0.25 (EtOAc); lit.6 mp 115–116 ꢁC,
D
23
144–145 ꢁC, ½aŠ ꢀ33.1 (c 0.5, CHCl3). IR (KBr): mmax
23
½aŠ ꢀ12.2 (c 0.4, MeOH). IR (KBr): mmax 3420 (OH),
D
D
1360 (as. SO2), 1200–1180 (sym. SO2). NOE-contact:
H-1 and H-3.
1360–1340 (as. SO2), 1190–1180 (sym. SO2).
1.1.3. Methyl 2,3-anhydro-a-D-ribopyranoside (11). To
a soln of 9 (2.94 g, 12.14 mmol) in anhydrous MeOH
(30 mL) was added 1 M NaOMe in MeOH (24.3 mL,
24.3 mmol). The mixture was stirred at 55–60 ꢁC for
1 h and then evaporated. Flash column chromatography
(Et2O) of the residue gave pure 11 (1.71 g, 96%) that
1.1.2. Methyl 2-O-methanesulfonyl-a-D-arabinopyrano-
side (9). Procedure A. A soln of 7 (0.96 g, 3.39 mmol)
in aq 90% TFA (10 mL) was stirred for 0.5 h at room
temperature. The mixture was evaporated by co-distilla-
tion with toluene (3 · 20 mL) to a yellow syrup. Flash
column chromatography (EtOAc) of the residue gave
pure 9 (0.724 g, 88%), which crystallized from EtOAc–
hexane.
crystallized from CH2Cl2–light petroleum in the form
23
D
of colourless silky crystals, mp 85 ꢁC, ½aŠ +148.9 (c 0.5,
23
CHCl3), Rf 0.26 (Et2O); lit.6 mp 83.5 ꢁC, ½aŠ +165.0
D
Procedure B. To a cooled (ꢀ10 ꢁC) and stirred soln of
5 (5.00 g, 26.29 mmol) in dry CH2Cl2 (50 mL) and dry
Et3N (14.38 mL, 103.17 mmol), was added a cooled
(ꢀ10 ꢁC) soln of MsCl (6.11 mL, 78.78 mmol) in dry
CH2Cl2 (12 mL). The mixture was stirred at ꢀ10 ꢁC
for 0.5 h, then diluted with CH2Cl2 (20 mL) and washed
successively with aq 5% HCl (2 · 100 mL) and 1% NaH-
CO3 (50 mL). The organic soln was dried and evapo-
rated, and the remaining crude 6 was dissolved in abs
MeOH (50 mL) and cooled to 0 ꢁC. To the soln was
added Ag2O (6.05 g, 26.11 mmol), the resulting suspen-
sion was stirred at 0 ꢁC for 0.5 h, and then at room tem-
perature for 1 h. The reaction mixture was diluted with
EtOAc, filtered through a Celite pad and evaporated to
a yellow syrup. The residue was dissolved in aq 90%
TFA (40 mL) and stirred for 0.5 h at room temperature.
The mixture was evaporated by co-distillation with tol-
uene (5 · 30 mL) to a yellow oil. Flash column chromato-
graphy (4:1 light petroleum–EtOAc) of the residue first
gave pure b-anomer 10 (0.212 g, 3%), which crystallized
(c 0.2, CHCl3). IR (KBr): mmax 3420–3350 (OH).
1.1.4. Methyl 2,3-anhydro-4-O-methanesulfonyl-a-D-ribo-
pyranoside (12). To a stirred and cooled soln (ꢀ10 ꢁC)
of 11 (0.82 g, 5.65 mmol) in dry CH2Cl2 (10 mL) was
added Et3N (1.55 mL, 11.12 mmol) and a cooled
(ꢀ10 ꢁC) soln of MsCl (0.53 mL, 6.83 mmol) in dry
CH2Cl2 (5 mL). Stirring was continued for 1.5 h at
ꢀ10 ꢁC and the mixture diluted with CH2Cl2 (10 mL),
washed successively with aq 5% HCl (2 · 25 mL) and
1% NaHCO3 (20 mL). The organic soln was dried and
evaporated to yellow syrup. Flash column chromatogra-
phy (3:2 light petroleum–EtOAc) of the residue gave
pure 12 (1.177 g, 93%) as a solid, which upon crystalliza-
tion from CH2Cl2–hexane gave colourless needles, mp
23
D
115 ꢁC, ½aŠ ¼ þ142.6 (c 0.5, CHCl3), Rf 0.39 (Et2O).
IR (KBr): mmax 1360 (as. SO2), 1190 (sym. SO2). FAB
MS: m/z 247 (M++Na), 225 (M++H). Anal. Calcd for
C7H12O6S: C, 37.49; H, 5.39; S, 14.30. Found: C,
37.57; H, 5.43; S, 14.10.
from a mixture of EtOAc–hexane in the form of colour-
23
D
less crystals, mp 88–90 ꢁC, ½aŠ ꢀ168 (c 0.8, CHCl3), Rf
1.1.5. Methyl 2,3-anhydro-4-azido-4-deoxy-b-L-lyxopyr-
anoside (13) and methyl 2,4-diazido-2,4-dideoxy-b-L-
xylopyranoside (14). To a soln of 12 (0.117 g,
0.52 mmol) in dry DMF (7 mL) was added NaN3
23
0.11 (Et2O); lit.6 mp 69–70 ꢁC, ½aŠ ꢀ153 (c 0.8, CHCl3);
D
23
D
lit.10 (for L-isomer) mp 86 ꢁC, ½aŠ +163 (c 1.0, CHCl3).
IR (KBr): mmax 3530–3350 (OH), 1370 (as. SO2), 1190

V. Popsavin et al. / Carbohydrate Research 340 (2005) 1866–1871
1871
23
D
(0.30 g, 4.62 mmol). The mixture was stirred at 95 ꢁC for
1 h, then evaporated and extracted with EtOAc (20 mL).
The organic phase was filtered, washed with water
(2 · 10 mL), dried and evaporated. The residue was
purified by flash chromatography (4:1 light petroleum–
mp 111–112 ꢁC, ½aŠ +217.0 (c 0.8, CHCl3), Rf 0.71
23
(Et2O); lit.12 (for D-isomer) mp 107–109 ꢁC,
½aŠ ꢀ220.0 (c 1.0, CHCl3). IR (KBr): mmax 3440 (OH),
D
2130–2100 (N3); CI MS: m/z 215 (M++H). Anal. Calcd
for C6H10N6O3: C, 33.65; H, 4.71; N, 39.40. Found: C,
33.64; H, 5.06; N, 39.54.
EtOAc) to give pure 13 (0.029 g, 32%) as a colourless
23
D
oil, ½aŠ +50.1 (c 0.9, CHCl3), Rf = 0.55 (CH2Cl2);
23
lit.11 (for D-isomer): ½aŠ ꢀ54 (c 0.4, CHCl3). IR (film):
D
mmax 2120 (N3). CI MS: m/z 215 (M++C4H10–N), 200
(M++C4H10ꢀHꢀN2), 172 (M++H). HR MS (ES+):
m/z 194.0545 (M++Na). Calcd for C6H9N3O3Na:
194.0542. Further elution of the column gave 14
Acknowledgements
This work was supported by a research grant from the
Ministry of Science and Environment Protection of the
Republic of Serbia (Grant No. 1896). The authors are
grateful to Mrs. T. Marinko-Covell (Department of
Chemistry, University of Leeds, UK) for recording the
mass spectra.
(0.065 g, 16%) that crystallized from CH2Cl2–hexane
23
D
as colourless crystals, mp 72–73 ꢁC, ½aŠ +13.5 (c 0.6,
23
CHCl3), Rf 0.26 (CH2Cl2); lit.12 (for D-isomer): mp 72–
73 ꢁC, ½aŠ ꢀ18.4 (c 1.0, CHCl3). IR (KBr): mmax 3290
D
(OH), 2150–2130 (N3). CI MS: m/z 215 (M++H). Anal.
Calcd for C6H10N6O3: C, 33.65; H, 4.71; N, 39.24.
Found: C, 33.74; H, 4.76; N, 39.48.
References
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