Conversion of D-xylose to protected D-lyxose derivatives and to D-lyxose, via the corresponding 1,2-anhydride

Article abstract of DOI:10.1016/S0008-6215(99)00164-0

Acid hydrolysis of 3,5-di-O-benzyl-1,2-O-cyclohexylidene-α-D-xylofuranose gave the corresponding lactol, which was subsequently converted to the 3,5-di-O-benzyl-2-O-mesyl-D-xylofuranose. This compound readily reacted with sodium methoxide, sodium benzylate or sodium hydroxide (presumably via the corresponding 1,2-anhydride) to give the protected D-lyxofuranosides. These compounds were finally converted to methyl α-D-lyxopyranoside or to D-lyxose. Copyright (C) 1999 Elsevier Science Ltd.

Full text of DOI:10.1016/S0008-6215(99)00164-0

www.elsevier.nl/locate/carres
Carbohydrate Research 321 (1999) 110–115
Note
Conversion of
D-xylose to protected
D-lyxose derivatives
and to -lyxose, via the corresponding 1,2-anhydride
D
a
b
Velimir Popsavin a,*, Sanja Grabezˇ , Biljana Stojanovic´ , Mirjana Popsavin a,
b
a
Vjera Pejanovic´ , Dusˇan Miljkovic´
a Institute of Chemistry, Faculty of Sciences, Uni6ersity of No6i Sad, Trg D. Obrado6ic´a 3,
YU-21000 No6i Sad, Yugosla6ia
b ICN Yugosla6ia Institute, 29 No6embra 111, YU-11000 Belgrade, Yugosla6ia
Received 26 March 1999; accepted 17 June 1999
Abstract
Acid hydrolysis of 3,5-di-O-benzyl-1,2-O-cyclohexylidene-a-
was subsequently converted to the 3,5-di-O-benzyl-2-O-mesyl-
sodium methoxide, sodium benzylate or sodium hydroxide (presumably via the corresponding 1,2-anhydride) to give
the protected -lyxofuranosides. These compounds were finally converted to methyl a- -lyxopyranoside or to
-lyxose. © 1999 Elsevier Science Ltd. All rights reserved.
D
-xylofuranose gave the corresponding lactol, which
D
-xylofuranose. This compound readily reacted with
D
D
D
Keywords: 1,2-Anhydro sugar;
D-Lyxose; D-Lyxosides, protected; Mutarotation; D-Xylofuranose, protected
quent opening of the 1,2-anhydro ring with an
appropriate alkoxide anion leads to the corre-
sponding glycopyranoside. This methodology
has been used earlier for the preparation of
1. Introduction
Remarkable progress has been made in the
synthesis of O-glycosides by regioselective nu-
cleophilic ring opening of 1,2-anhydrohexo-
pyranose derivatives with various alcohols
[1,2], aryloxy anions [3] or with suitably pro-
tected monosaccharides [2–4]. Conversely, a
possibility of using 1,2-anhydroaldopentose
derivatives as intermediates in the synthesis of
certain pentopyranosides has been recognized
[5] but not extensively exploited. 1,2-Anhydro
pentoses are usually prepared in situ by in-
tramolecular displacement of leaving groups
at C-1 (or C-2) with free C-2 (or C-1) hy-
droxyl group, under basic conditions. Subse-
methyl b-
2-O-mesyl-
ide [5]. Now the use of similar reaction condi-
tions for the preparation of certain -lyxof-
uranosides from suitably protected 2-O-mesyl-
-xylose derivative has been studied. The
preparation of the 2-O-mesyl- -xylofuranose
derivative 4 was first attempted.
D
-ribopyranoside by treatment of
D
-arabinose with sodium methox-
D
D
D
* Corresponding author. Fax: +381-21-54-065.
E-mail address: vpops@eunet.yu (V. Popsavin)
0008-6215/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(99)00164-0

V. Popsa6in et al. / Carbohydrate Research 321 (1999) 110–115
111
Table 1
13C NMR data for 6, 7 and 11 (in D2O) and comparison with Ref. [10]
Compound
C-1
C-2
C-3
C-4
C-5
CH3O
Reference
6
109.1
109.2
102.3
102.0
94.9
94.9
95.1
77.0
77.0
70.4
70.4
70.8
71.0
70.9
70.9
72.0
72.2
71.9
71.6
71.3
71.4
73.5
73.5
81.4
81.4
67.5
67.7
68.4
68.4
67.3
67.4
61.1
61.5
63.9
63.3
63.9
63.9
65.1
65.0
56.9
56.9
55.2
55.9
This work
[10]
This work
[10]
This work
[10]
This work
[10]
7
a-11
b-11
95.0
responding 1,2-anhydro derivative as an
intermediate2. The subsequent step could in-
volve a nucleophilic attack of the methoxide
ion at C-1 to give 5 as the main reaction
product. Apart from the isolated product 5,
the reaction mixture contained a small
amount of a more polar component. Although
this material was chromatographically homo-
geneous in different solvent systems, it ap-
peared to be a mixture of several products,
with the most prominent one presumably be-
1,2 - O - Cyclohexylidene - a -
(1), readily available from
D
- xylofuranose
D
-xylose [6], reacted
with benzyl chloride in the presence of pow-
dered potassium hydroxide (Me2SO, 60 °C) to
afford the corresponding 3,5-di-O-benzyl
derivative 2 in 71% yield. The cyclohexylidene
group was removed from 2 by hydrolysis with
aqueous acetic acid to give the crystalline
lactol 3 in 71% yield. The product was mainly
the a anomer since a chloroform solution
mutarotated to a less positive equilibrium
value (see Section 2). Treatment of 3 with
ing the methyl 3,5-di-O-benzyl-b- -lyxofuran-
D
oside, as indicated by NMR spectral data [lH
4.79 (d, J1,2 1.7 Hz, H-1), 3.39 (s, OCH3); lC
109.50 (C-1), 55.59 (OCH3)]. Compound 5
was further debenzylated (H2ꢀPd/C) to the
mesyl
chloride
and
triethylamine
in
dichloromethane gave the desired 2-O-mesyl
derivative 4 accompanied by at least an equal
amount of a less-polar component (pre-
sumably [7] the corresponding glycosyl chlo-
known [9] methyl a- -lyxofuranoside (6).
D
Moreover, acid-catalysed methanolysis of 6
ride),
as
estimated
by
TLC
(1:1
(HCl, MeOH) afforded the known [11] methyl
hexane–EtOAc). Treatment of the mixture
with an excess of silica gel in dichloromethane
converted, almost completely, the less-polar
component to the crystalline 2-O-mesyl
derivative 4. In contrast to the lactol 3, com-
pound 4 was not observed to mutarotate in
chloroform solution1.
a-
-lyxopyranoside (7) in 90% yield. The 13C
D
NMR spectral data (Table 1), as well as the
physical constants of both products 6 and 7,
were in reasonable agreement with those al-
ready reported in the literature [9–11]. Com-
pound 7 represents a convenient starting
material for the preparation of 1,2,3,5-tetra-
Reaction of 3,5-di-O-benzyl-2-O-methane-
O-acetyl-4-thio- -ribofuranose and the corre-
L
sulfonyl-
methoxide gave the methyl 3,5-di-O-benzyl-a-
-lyxofuranoside (5) in 57% yield. A possible
D
-xylofuranose (4) with sodium
sponding nucleoside analogs [11].
D
mechanism for this transformation pre-
sumably involves initial formation of the cor-
1
1 According to H NMR spectral data, it appeared to be an
1:4 mixture of a and b anomer, as established by integration
of the corresponding proton signals [l 5.27 (d, J1,2 1.5 Hz,
H-1b) and 5.59 (l, J1,2 4.1 Hz, H-1a)]. The initial 1:4 a–b
anomeric ratio (recorded immediately after dissolution of the
sample) remains unchanged after storing the solution at room
temperature for 3 days. Similarly to compound 4, the 2-O-
mesyl-
days.
D
-arabinose derivative [8] shows no mutarotation in 2
2 All attempts to isolate the 1,2-anhydro intermediate failed
due to its instability and/or high reactivity.

112
V. Popsa6in et al. / Carbohydrate Research 321 (1999) 110–115
were identical to those already recorded for
Treatment of 3,5-di-O-benzyl-2-O-methane-
sulfonyl- -xylofuranose (4) with sodium ben-
the sample prepared by C-2 epimerization of
D
4.
zylate afforded a 5:1 mixture of two anomeric
benzyl lyxofuranosides in a 46% combined
yield. The major product was the a anomer 8,
as indicated by its highly positive optical rota-
tion {[h]D +112.9° (c 1.02)}. This was addi-
Catalytic hydrogenolysis of the lactol 10
13
over Pd/C gave
D
-lyxose (11), with C NMR
spectral data (Table 1), as well as the physical
constants in good agreement with those al-
ready reported in the literature [10,13]. The
sequence 2“4“10“11 then affords a con-
1
tionally confirmed by H NMR spectroscopy
since the anomeric signal [l 5.13 (s, 1 H, H-1)]
showed no vicinal coupling with H-2 [l 4.20
(dd, J2,OH 10.2, J2,3 4.8 Hz)]. The minor
product was the b anomer 9, as indicated by a
less positive optical rotation {[h]D +82.1° (c
1.43)}, as well as by a significant vicinal cou-
pling between H-1 and H-2 (J1,2 4.7 Hz),
compatible with a cis relationship of these
protons. The stereochemistry of the minor
product 9 was additionally confirmed by an
NOE experiment. Upon irradiation of the
multiplet at lH 4.08 (dd, 1 H, H-3), a signifi-
cant enhancement of the anomeric proton sig-
nal was observed. This confirmed a spatial
vicinity of H-1 and H-3 in 9 and consequently,
a b configuration at the anomeric position.
Both protected lyxofuranosides 8 and 9 repre-
sent suitable building blocks for the prepara-
tion of oligosaccharides containing the
venient and novel synthesis of
-xylose.
D
-lyxose from
D
2. Experimental
General methods.—Melting points were de-
termined on a Bu¨chi SMP 20 apparatus and
were not corrected. Optical rotations were
measured on a Perkin–Elmer 141 MC polar-
imeter. NMR spectra were recorded on a
Bruker AC 250 E instrument and chemical
shifts are expressed in ppm downfield from
Me4Si. Chemical ionization mass spectra were
recorded on a Finnigan-MAT 8230 mass spec-
trometer with isobutane as a reagent gas. TLC
was performed on DC Alufolien Kieselgel 60
(1“2)-O-glycosidic bond, with
the reducing end.
D
-lyxose at
F254 (E. Merck). Column chromatography was
carried out using Kieselgel 60 (under 0.063
mm; E. Merck). Flash column chromatogra-
phy was performed using ICN silica 32-63. All
organic extracts were dried with anhyd
Na2SO4. Organic solutions were concentrated
in a rotary evaporator under diminished pres-
sure at a bath temperature below 35 °C.
Moreover, it has also been shown that
sodium hydroxide could be used for the direct
C-2 epimerization of the 2-O-mesyl-
derivative 4 to the corresponding
D
-xylo
-lyxo
D
derivative 10. This surprisingly clean and
smooth transformation was carried out with
an equimolar amount of the base in aqueous
N,N-dimethylformamide, whereupon syrupy
3,5-Di-O-benzyl-1,2-O-cyclohexylidene-h-
D
-
-
xylofuranose (2).—1,2-O-cyclohexylidene-a-
D
3,5-di-O-benzyl- -lyxofuranose (10) was ob-
D
xylofuranose [6] (1; 9.34 g, 40.61 mmol) was
dissolved in Me2SO (60 mL), and then pow-
dered KOH (10 g, 178.22 mmol) and benzyl
chloride (43 mL, 373.65 mmol) were added.
The reaction mixture was stirred for 1 h at
60 °C, then poured into cold water (200 mL)
and extracted with CH2Cl2 (3×100 mL). The
extracts were washed with water (3×50 mL),
dried and concentrated to a yellow syrup.
Crystallisation from MeOH afforded pure 2
(11.79 g, 71%) as white needles: mp 89–91 °C;
tained in 75% yield. No products of hydrolysis
or elimination of the C-2 sulfonyloxy group
could be detected in the reaction mixture.
Conversely, treatment of 2-O-tosyl-
D
-xylose
-lyxose
with aqueous sodium hydroxide gave
D
contaminated with small amounts of
D
-xylose,
D
-arabinose and 2-
D
-threo-pentos-2-ulose [12].
The structure of 10 was confirmed by NMR
and MS data, as well as by its independent
preparation from methyl lyxoside 5. Hydroly-
sis of 5 in boiling aqueous acetic acid fur-
1
[h]D −39° (c 0.1, CHCl3); H NMR (CDCl3):
1
nished the lactol 10 in 70% yield. The H and
l 7.41–7.25 (m, 10 H, 2 Ph), 5.96 (d, 1 H,
H-1), 4.61 (d, 1 H, J1,2 3.8 Hz, H-2), 4.64 and
13C NMR spectral data of 10 thus obtained

V. Popsa6in et al. / Carbohydrate Research 321 (1999) 110–115
113
g) at room temperature (rt) overnight. The
mixture was filtered and the precipitate
washed with EtOAc. The filtrates were evapo-
rated, and the residue was submitted to flash-
chromatography (2:1 hexane–EtOAc) to
furnish pure product 4 (1.3 g, 62%): mp 104–
105 °C (CH2Cl2–hexane); [h]D +3.5° (c 0.88,
4.58 (2 d, each 2 H, Jgem 12 Hz, 2 PhCH2),
4.23 (td, 1 H, H-4), 4.01 (d, 1 H, J3,4 3.2 Hz,
H-3), 3.81 (dd, 1 H, J4,5b 6.1 Hz, H-5b), 3.75
(dd, 1 H, J5a,5b 9.8, J4,5a 6.1 Hz, H-5a), 1.77–
1.34 (m, 10 H, cyclohexylidene residue); 13C
NMR (CDCl3): l 138.03 and 137.61 (aro-
matic), 128.40, 128.34, 127.77, 127.62, 127.50,
112.37 (quaternary C from cyclohexylidene
residue), 104.61 (C-1), 81.91 (C-2), 81.86 (C-
3), 79.13 (C-4), 73.51 and 71.97 (2 PhCH2),
67.52 (C-5), 36.43 (5 CH2 from cyclohexyli-
dene residue), 35.80, 24.87, 23.85, 23.57;
CIMS: m/z 411 [M+H]+. Anal. Calcd for
C25H30O5: C, 73.14; H, 7.31. Found: C, 73.28;
H, 7.42.
1
CHCl3); H NMR (CDCl3): l 7.36–7.28 (m,
10 H, 2 Ph), 5.59 (d, H-1a), 5.27 (d, H-1b),
5.06 (dd, J1,2 1.5 Hz, H-2b), 5.00 (t, J1,2 4.1,
J2,3 4.2 Hz, H-2a), 4.82–4.54 (m, 4 H, 2
PhCH2), 4.48 (m, J3,4 6.1 Hz, H-4a), 4.37 (m,
H-3a and H-4b), 4.31 (dd, J2,3 3.5, J3,4 6.1 Hz,
H-3b), 4.23 (d, exchangeable with D2O, 1 H,
J1,OH 11.9 Hz, OH), 3.80–3.60 (m, 2 H, a
anomer: J4,5 5.7, Jgem 11 Hz, b anomer: J4,5
3.8, Jgem 10.1 Hz, 2 H-5), 3.05 (s, 3 H,
CH3SO2); 13C NMR (CDCl3): l 137.70 and
136.99 (aromatic), 136.64, 128.39, 128.34,
128.20, 128.04, 127.88, 127.80, 127.63, 127.51,
127.38, 100.34 (C-1b), 94.20 (C-1a), 86.35 (C-
2b), 81.74 (C-2a), 80.41 (C-3b), 80.09 (C-3a),
79.25 (C-4b), 76.08 (C-4a), 73.27 and 72.68 (2
PhCH2 from b anomer), 73.54 and 72.59 (2
PhCH2 from a anomer), 68.43 (C-5a), 68.11
(C-5b), 38.22 (CH3SO2 from a anomer), 38.14
(CH3SO2 from b anomer); CIMS: m/z 409
[M+H]+, 391 [MꢀOH]+. Anal. Calcd for
C20H24O7S: C, 58.50; H, 5.70; S, 7.88. Found:
C, 58.81, H, 5.92; S, 7.85.
3,5-Di-O-benzyl- -xylofuranose (3).—A so-
D
lution of 2 (2.76 g, 6.73 mmol) in aq 70%
AcOH (80 mL) was stirred at reflux tempera-
ture for 8 h, then concentrated and co-evapo-
rated with toluene. The syrupy residue was
purified by flash chromatography (7:3
toluene–EtOAc) to give pure 3 (1.59 g, 71%):
mp 70–71 °C (toluene–hexane); [h]D
+
1
20.8°“ +14.7° (24 h) (c 1.15, CHCl3); H
NMR (CDCl3): l 7.40–7.25 (m, 10 H, 2 Ph),
5.48 and 5.18 (s and d, 1 H, H-1b and H-1a),
4.72–4.40 (m, 5 H, 2 PhCH2 and H-4), 4.23
and 4.14 (dd and d, 1 H, a anomer: J1,2 4.3
Hz, H-2a, and H-2b), 3.99 (m, 1 H, a anomer:
J2,3 2.8, J3,4 5 Hz, b anomer: J2,3 2.2 Hz, H-3),
3.78 and 3.69 (2 d, 2 H, a anomer: J4,5 5.2 Hz,
b anomer: J4,5 5.1 Hz, 2 H-5), 3.50 (bs, ex-
Methyl 3,5-di-O-benzyl-h- -lyxofuranoside
D
(5).—To a solution of 4 (0.5135 g, 1.26 mmol)
in dry benzene (5 mL) and MeOH (2 mL) was
added NaOMe (0.3 g, 5.56 mmol) and the
mixture was stirred for 3 days at ambient
temperature. The solution was diluted with
ether (20 mL), washed successively with aq
10% NH4Cl (3×10 mL) and water (10 mL),
dried and evaporated. Flash chromatography
(7:2 hexane–EtOAc) of the residue gave oily 5
(0.2478 g, 57%): [h]D +58.2° (c 0.12, CHCl3);
1H NMR (CDCl3): l 7.40–7.17 (m, 10 H, 2
Ph), 4.89 (s, 1 H, H-1), 4.64 (2 d, 2 H, Jgem
11.8 Hz, PhCH2), 4.62 (2 d, 2 H, Jgem 11.4 Hz,
PhCH2), 4.45 (bs, exchangeable with D2O, 1
H, OH), 4.44 (dd, 1 H, H-3), 4.33 (dt, 1 H, J3,4
8 Hz, H-4), 4.08 (d, 1 H, J2,3 4.8 Hz, H-2),
3.71 (dd, 1 H, J4,5b 3.1 Hz, H-5b), 3.64 (dd, 1
H, J4,5a 2.4, J5a,5b 10.5 Hz, H-5a), 3.37 (s, 3 H,
OCH3); 13C NMR (CDCl3): l 137.61 and
137.11 (aromatic), 127.28, 128.27, 127.76,
13
changeable with D2O, 2 H, 2 OH); C NMR
(CDCl3): l 137.72–127.45 (aromatic), 103.24
(C-1b), 95.99 (C-1a), 83.39 (C-3a), 82.69 (C-
3b), 79.80 (C-4b), 78.87 (C-2b), 77.24 (C-4a),
75.26 (C-2a), 73.50 and 73.37 (4 PhCH2),
72.49, 71.78, 69.00 (C-5a); CIMS: m/z 331
[M+H]+, 313 [MꢀOH]+. Anal. Calcd for
C19H22O5: C, 69.31; H, 6.66. Found: C, 69.11;
H, 6.98.
3,5 - Di - O - benzyl - 2 - O-methanesulfonyl - -
D
xylofuranose (4).—To a stirred and cooled
solution (−10 °C) of 3 (1.7 g, 5.15 mmol) in
dry CH2Cl2 (30 mL) was added Et3N (2 mL,
8.44 mmol) and mesyl chloride (0.9 mL, 11.64
mmol). Stirring was continued for 1.5 h and
the mixture was diluted with CH2Cl2 (30 mL),
washed successively with cold water, aq 10%
HCl, satd aq NaHCO3 and brine. The organic
solution was dried and stirred with silica gel (6

114
V. Popsa6in et al. / Carbohydrate Research 321 (1999) 110–115
M solution, 3.0 mmol), and the resulting mix-
ture was stirred for 20 h at rt. The mixture
was then poured into satd aq NH4Cl (15 mL)
and extracted with EtOAc (3×10 mL). The
extract was dried and evaporated, and the
remaining benzyl alcohol was removed by dis-
tillation in high vacuum (oil pump). Column
chromatography (19:1 toluene–EtOAc) of the
residue (0.8958 g) furnished the pure a anomer
8 (0.2439 g, 38.6%) as a colourless syrup: [h]D
127.69, 108.31 (C-1), 77.51 (C-3), 77.27 (C-4),
73.73 and 72.36 (2 PhCH2), 71.95 (C-2), 67.78
(C-5), 54.89 (OCH3); CIMS: m/z 345 [M+
H]+, 313 [MꢀOCH3]+, 295 [MꢀOCH3ꢀH2O]+.
Methyl h- -lyxofuranoside (6).—Com-
D
pound 5 (0.65 g, 1.89 mmol) was hydro-
genated over 10% PdꢀC (0.61 g) in EtOH (15
mL) at rt for 2 h. The mixture was filtered and
the catalyst was washed successively with 2:1
EtOH–EtOAc (75 mL) and EtOH (25 mL).
The filtrate and washings were combined and
concentrated. Flash chromatography (9:1
CHCl3–MeOH) of the residue yielded pure 6
(0.17 g, 55%): mp 95–96 °C (EtOAc), lit.
97.5–98.5 °C [9]; [h]D +111° (c 0.1, MeOH),
lit. +128° (c 1, MeOH) [9]; 1H NMR
(Me2SO-d6): l 5.20 (d, exchangeable with
D2O, 1 H, 2-OH), 4.89 (t, exchangeable with
D2O, 1 H, 5-OH), 4.83 (d, exchangeable with
D2O, 1 H, 3-OH), 4.65 (d, 1 H, H-1), 4.02 (m,
after addition of D2O t, 1 H, H-3), 3.91 (m, 1
H, J3,4 4.6 Hz, H-4), 3.80 (m, after addition of
D2O dd, 1 H, J1,2 2.9, J2,3 4.7, J2,OH 7 Hz,
H-2), 3.56 (m, after addition of D2O dd, 1 H,
J4,5b 4.6 Hz, H-5b), 3.45 (m, after addition of
D2O dd, 1 H, J4,5a 5.6, J5a,5b 11.5 Hz, H-5a),
3.23 (s, 3 H, OCH3). For 13C NMR data see
Table 1. CIMS: m/z 165 [M+H]+, 133
[MꢀOCH3]+.
1
+112.9° (c 1.02, CHCl3); H NMR (CDCl3):
l 7.44–7.32 (m, 15 H, 3 Ph), 5.13 (s, 1 H,
H-1), 4.81–4.48 (m, 7 H, 3 CH2Ph and H-3),
4.41 (m, 2 H, J3,4 6 Hz, OH and H-4), 4.20
(dd, 1 H, J2,OH 10.2, J2,3 4.8 Hz, H-2), 3.74
(dd, 1 H, J4,5b 3.2 Hz, H-5b), 3.66 (dd, 1 H,
J4,5a 2.4, J5a,5b 10.5 Hz, H-5a); 13C NMR
(CDCl3): l 137.71 and 137.60 (aromatic),
137.15, 128.34, 127.83, 127.81, 127.76, 127.72,
127.65, 106.49 (C-1), 77.79 (C-3), 77.51 (C-4),
72.08 (C-2), 73.81 and 72.44 (3 CH2Ph), 69.15,
67.82 (C-5). CIMS: m/z 421 [M+1]+, 313
[MꢀOBn]+. Further elution with 4:1 toluene–
EtOAc gave the pure b anomer 9 (0.0466 g;
7.4%) as a colourless syrup: [h]D +82.1° (c
1
1.43, CHCl3); H NMR (CDCl3): l 7.45–7.25
(m, 15 H, 3 Ph), 5.25 (d, 1 H, H-1), 4.96–4.54
(m, 6 H, 3 PhCH2), 4.51 (m, 1 H, H-4), 4.31
(m, 1 H, J1,2 4.7 Hz, H-2), 4.08 (dd, 1 H, J2,3
4.1, J3,4 6 Hz, H-3), 3.80 (dd, 1 H, J4,5b 4.3 Hz,
H-5b), 3.72 (dd, 1 H, J5a,5b 10.6, J4,5a 6.7 Hz,
H-5a), 2.86 (d, exchangeable with D2O, 1 H,
J2,OH 7.6 Hz, OH); 13C NMR (CDCl3): l
138.13 and 137.88 (aromatic), 137.07, 128.43,
128.29, 128.28, 128.02, 127.92, 127.68, 127.58,
127.51, 127.45, 99.86 (C-1), 83.55 (C-3), 77.49
(C-4), 77.04 (C-2), 73.80 and 71.38 (3 PhCH2),
69.88, 68.99 (C-5). CIMS: m/z 421 [M+1]+,
313 [MꢀOBn]+.
Methyl h- -lyxopyranoside (7).—Com-
D
pound 6 (0.0928 g, 0.56 mmol) was refluxed
for 30 min with 2% methanolic hydrogen chlo-
ride (2 mL). The mixture was diluted with
MeOH (4 mL), then neutralised [Amberlyte
IRA 45 resin (OH form)], filtered and evapo-
rated. Flash chromatography (6:1 CHCl3–
MeOH) of the residue gave pure 7 (0.084 g,
90%) as a white solid. Recrystallised from
EtOAc, 7 had mp 104–105 °C, lit. 108–109 °C
[11]; [h]D +56.5° (c 0.6, H2O), lit. +52° (c
3,5-Di-O-benzyl- -lyxofuranose (10).—(a)
D
The 2-O-mesyl derivative 4 (0.3317 g, 0.80
mmol) was dissolved in N,N-dimethylfor-
mamide (3 mL), and 0.1 M aq NaOH (8 ml)
was added slowly at rt during 1 h, whereupon
the solution became alkaline to phenolph-
thalein. The mixture was stirred at rt for an
additional 0.5 h, then neutralized with glacial
AcOH and concentrated by co-distillation
with toluene. The syrupy residue was purified
by flash column chromatography (4:1
toluene–EtOAc) to afford syrupy 10 (0.1995
g, 75%) as a 1:1 mixture of anomers.
1
0.6, H2O) [11]; H NMR (Me2SO-d6): l 4.80
and 4.77 (3 d, exchangeable with D2O, each 1
H, 3 OH), 4.65, 4.41 (d, 1 H, J1,2 Hz, H-1),
3.36–3.60 (m, 4 H, H-2, H-3, H-4, H-5b), 3.24
13
(s, 3 H, OCH3), 3.20 (m, 1 H, H-5a). For C
NMR data see Table 1. CIMS: m/z 165 [M+
H]+, 133 [MꢀOCH3]+.
Benzyl 3,5-di-O-benzyl-h- (8) and i- -lyxo-
D
furanoside (9).—To a solution of 4 (0.6142 g,
1.5 mmol) in dry benzene (10 mL) was added
a solution of NaOBn in BnOH (15 mL of 0.2

V. Popsa6in et al. / Carbohydrate Research 321 (1999) 110–115
115
Acknowledgements
(b) A solution of 5 (0.2082 g, 0.61 mmol) in
70% aq AcOH (10 mL) was stirred at reflux
temperature for 8 h, then concentrated and
co-evaporated with toluene. The syrupy
residue (0.1894 g) was purified by flash chro-
matography (1:1 hexane–EtOAc) to give pure
10 (0.1408 g, 70%) as a colourless syrup: [h]D
This work was supported by a research
grant from the Ministry of Science and Tech-
nology of the Republic of Serbia. The authors
thank Dr P. Radivojsˇa (Center of Chemistry,
ICTM, Belgrade), for the measurements of
optical rotation, and Mr D. Djokovic´ (Faculty
of Chemistry, University of Belgrade), for
recording the mass spectral data.
1
+24.6° (c 1.32, CHCl3); H NMR (CDCl3+
D2O): l 7.42–7.28 (m, 20 H, 4 Ph), 5.34 (s, 1
H, H-1a), 5.17 (d, 1H, H-1b), 4.81–4.47 (m, 9
H, H-3 and 4 PhCH2), 4.42 (dt, 1 H, J3,4 7.9
Hz, H-4a), 4.20 (m, 2 H, H-3a and H-4b),
4.10 (d, 1 H, J2,3 4.7 Hz, H-2a), 4.05 (t, 1 H,
J1,2 3.9, J2,3 4.6 Hz, H-2b), 3.75–3.57 (m, 4 H,
a anomer: J4,5 2.7 Hz, b anomer: J4,5 4.2 Hz, 2
H-5a and 2 H-5b); 13C NMR (CDCl3): l
137.65–127.81 (aromatic), 102.14 (C-1a),
96.82 (C-1b), 77.77 and 77.55 (C-3b and C-
4b), 77.44 (C-3a), 73.80 (PhCH2), 73.34 (C-
4a), 72.73 (PhCH2), 72.55 (C-2a), 70.09
(C-2b), 68.57 (C-5b), 67.91 (C-5a); CIMS: m/z
331 [M+H]+, 313 [MꢀOH]+.
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D
-Lyxose (11).—Compound 10 (0.3506 g,
1.06 mmol) was hydrogenated over 10% PdꢀC
(0.2348 g) in EtOH (15 mL) at rt for 18 h. The
mixture was filtered and the catalyst was
washed with EtOH. The filtrate and
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with cooled EtOH (+4 °C) gave pure
D-
lyxose (11): mp 104–105 °C, lit. 106–107 °C
[13]; [h]D −13.6° (c 1.5, H2O), lit. −14°
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Table 1.
.