Synthesis of 5-hydroxy-2-(β-D-ribofuranosyl)pyran-4-one from a pyranulose glycoside

Article abstract of DOI:10.1016/S0008-6215(99)00098-1

The synthesis of 5-hydroxy-2-(β-D-ribofuranosyl)pyran-4-one (9) is described. Treatment of pyranulose glycoside with bromine in carbon tetrachloride afforded brompyranulose glycoside in 90% yield. The reaction of (6S)- and (6R)-4-bromo-6-hydroxy-6-(2,3,5-

Full text of DOI:10.1016/S0008-6215(99)00098-1

www.elsevier.nl/locate/carres
Carbohydrate Research 318 (1999) 180–185
Note
Synthesis of 5-hydroxy-2-(b-
D
-ribofuranosyl)pyran-4-one
from a pyranulose glycoside
Shigeyuki Kanazawa, Souhei Mizuno, Rie Yamauchi, Natsu Nishimura,
Isamu Maeba *
Faculty of Pharmacy, Meijo Uni6ersity, Tempaku, Nagoya 468, Japan
Received 23 February 1999; accepted 16 April 1999
Abstract
The synthesis of 5-hydroxy-2-(b-
with bromine in carbon tetrachloride afforded brompyranulose glycoside in 90% yield. The reaction of (6S)- and
(6R)-4-bromo-6-hydroxy-6-(2,3,5-tri-O-benzoyl-b- -ribofuranosyl)-6H-pyran-3-one (2) in acidic media was exam-
ined with the following results: the reaction of 2 with trifluoroacetic acid (TFA) in dioxane afforded a mixture of
5-hydroxy-2-(2,3,5-tri-O-benzoyl-b- -ribofuranosyl)pyran-4-one (3) and its furan derivative 5-hydroxy-2-{5-(benzoy-
loxy)methyl]furan-2-yl}pyran-4-one (4), but the use of hydrochloric acid formed the bromofurfural, 3-bromo-5-
(2,3,5-tri-O-benzoyl-b- -ribofuranosyl)-2-furancarboxyaldehyde only. Acetylation of a mixture (3 and 4) with acetic
anhydride facilitated product separation to give the corresponding acetates 5-acetoxy-2-(2,3,5-tri-O-benzoyl-b- -ribo-
furanosyl)pyran-4-one (5) and 5-acetoxy-2-{5-[(benzoyloxy)methyl]furan-2-yl}pyran-4-one (6). Treatment of 5 with
hydrazine afforded 3-hydroxymethyl-6-(b- -ribofuranosyl)-1H-pyridazin-4-one in 43% yield. Debenzoylation of 5
D
-ribofuranosyl)pyran-4-one (9) is described. Treatment of pyranulose glycoside
D
D
D
D
D
with aq ammonia gave 9 in 50% yield. © 1999 Elsevier Science Ltd. All rights reserved.
Keywords: Synthesis; Pyranulose glycoside; Pyran-4-one; Pyridazin-4-one; C-Nucleoside
1. Introduction
The pyran-4-one and benzopyran-4-one
groups of naturally occurring compounds
have aroused considerable interest due to their
biological activities [1]. Phenoxan [2] and au-
reothin [3] are recently isolated natural prod-
ucts that have been shown to have anti-HIV
activity.
* Corresponding author. Tel.: +81-52-832-1781; fax: +
81-52-834-8090.
E-mail address: maeba@meijo-u.ac.jp (I. Maeba)
Hudecova and co-workers [4,5] have syn-
thesized 5-hydroxy-2-azidomethylpyran-4-one
0008-6215/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved.
PII: S0008-6215(99)00098-1

S. Kanazawa et al. / Carbohydrate Research 318 (1999) 180–185
181
and 5-benzoyloxy-2-thiocyanatomethylpyran-
4-one as potential antitumor agents. These
findings prompted us to synthesize the 5-hydr-
oxypyran-4-one glycoside (9). Two methods
[6] have been reported for the synthesis of
pyran-4-ones from pyran-3-one derivatives
based on epoxidation to 6-alkoxypyran-3-one
and subsequent hydrolysis in mild acid. At-
tempted epoxidation of a 6-alkoxypyran-3-one
glycoside [7] under a variety of conditions,
however, proved unsuccessful, leading to
degradation of the starting material. Then,
bromination of the pyranulose glycoside 1,
resulted from elimination of two benzoyloxy
groups. Separation of 3 and 4 was found to be
impractical owing to slow elimination of the
2,3-dibenzoyloxy groups on the sugar moiety
during chromatography on silica gel. Treat-
ment of the mixture of 3 and 4 with acetic
anhydride afforded the acetates 5 and 6 that
could be easily separated by preparative thin-
layer chromatography (PTLC). Structural de-
termination of 3 was made via MS and NMR
1
experiments. The H NMR spectrum of 3
showed two singlets at l 6.67 and 7.63 that
are characteristic of the pyran-4-one moiety.
When 2 was treated with hydrochloric acid in
acetonitrile, it did not afford pyran-4-one 3
but instead gave bromofurfural 7 in 17% yield.
We think that the formation of 7 proceeds
through the formation of the ring-opened in-
termediate g-diketone 2%, which subsequently
undergoes ring closure to the five-membered
aldehyde (Scheme 1).
It is worth noting that hydrazinolysis reac-
tions of the g-pyrone derivatives were found
to give a mixture of derivatives of pyrida-
zine and pyrazoles and not, as might have
been expected, N-aminopyridines [9]. Reac-
tion of the pyrone 5 with anhydrous hydrazine
in N,N-dimethylformamide gave 3-hydrox-
6-hydroxy-6-(2,3,5-tri-O-benzoyl-b- -ribo-
D
furanosyl)pyran-3[2H,6H]-one [8], followed by
an in situ acid-(catalyzed) hydrolysis, was
examined.
Bromination of pyranulose glycoside 1 with
bromine and carbon tetrachloride at room
temperature afforded pyranulose 2 as a mix-
ture of diastereomers in 90% yield. These iso-
mers could not be separated, but the mixture
was purified by column chromatography, and
the product mixture was entirely satisfactory
for the next step. Treatment of bromo com-
pound 2 with trifluoroacetic acid (TFA) in
dioxane at room temperature for 6 days af-
forded two products, 5-hydroxy-2-(2,3,5-tri-
O-benzoyl-b-
D
-ribofuranosyl)pyran-4-one (3,
ymethyl-6-(b-
D
-ribofuranosyl)-1H-pyridazin-
48%), and the furan derivative 4 (8%), which
4-one (8) in 43% yield. However, the pyrazole
Scheme 1. Reagents and conditions: (a) Br2/CCl4, rt, 30 min; (b) TFA/dioxane, rt, 6 days; (c) HCl/MeCN, 60 °C, 8 h.

182
S. Kanazawa et al. / Carbohydrate Research 318 (1999) 180–185
Scheme 2. Reagents and conditions: (a) NH2NH2/DMF, rt, 2 days; (b) aq. NH3/MeOH, room temperature, 1 day.
coated with a 0.25-mm layer of Silica Gel
GF254 (E. Merck). The compounds were de-
tected by UV light (254 nm).
derivative was not obtained. Structural assign-
ment of 8 was supported by the 13C NMR
spectrum, which exhibited the signal of the
amide carbonyl carbon at l 172 ppm. Re-
moval of the sugar protecting groups in com-
pound 5 was readily accomplished with
(6S)- and (6R)-4-Bromo-6-hydroxy-6-(2,3,-
5-tri-O-benzoyl-i- -ribofuranosyl)-6H-pyran-
D
3-one (2).—To a solution of 1 [8] (515.2 mg,
0.9233 mmol) in CCl4 (10 mL) at 0 °C was
added CCl4 (1 mL) containing 0.1 mL of
bromine. The mixture was stirred at room
temperatuer (rt) for 30 min, and excess
bromine was decomposed by sodium thiosul-
fate. The reaction mixture was poured into
ice-water, neutralized with satd aq NaHCO3
and then extracted with CHCl3 (3×10 mL).
The extracts were combined, washed with wa-
ter, dried over MgSO4, and concentrated to
dryness. The residue was chromatographed on
a column of silica gel with CHCl3 as eluent to
give 529.4 mg (90%) of 2 as a pale-yellow
aqueous ammonia to afford 5-hydroxy-2-(b- -
D
ribofuranosyl)pyran-4-one (9) in 50% yield.
We assigned the anomeric configuration of
compounds 8 and 9 based on the difference in
the chemical shifts of the two methyl signals
of the corresponding 2,3-O-isopropylidene
1
derivatives 10 and 11. The H NMR chemical
shift differential value (Dl) of the methyl
groups (0.19 and 0.22) is indicative of b stere-
ochemistry in accordance with Imbach’s rule
[10] (B0.15 and \0.15 ppm for the a and b
anomers, respectively). This indicates that the
b-ribofuranoside configuration has been pre-
served during the reaction sequence (Scheme
2).
1
foam; H NMR (CDCl3): l 4.03, 4.14 (each d,
each 0.5 H, J2a,2b =16.8 Hz, H-2a), 4.39, 4.40
(each d, each 0.5 H, J1%,2%=5.7 and 6.7 Hz,
H-1%), 4.51, 4.77 (each d, each 0.5 H, J2a,2b
=
16.8 Hz, H-2b), 4.49–4.93 (m, 3 H, H-4%, 5%),
5.48 (dd, 0.5 H, J2%,3%=J3%,4%=6.4 Hz, H-3%),
5.71–5.83 (m, 1.5 H, H-2%, 3%), 7.32–8.10 (m,
16 H, Ph, H-5); 13C NMR (CDCl3): l 62.0,
63.1 (C-5%), 66.4, 66.8 (C-2), 71.7, 71.9, 72.0,
72.6, 79.0, 79.7, 86.1, 87.3 (C-1%, 2%, 3%, 4%),
94.6, 95.2 (C-6), 123.3, 124.5 (C-4), 128.3–
134.1 (Ph), 145.4, 146.2 (C-5), 165.2, 165.3,
165.4, 166.0, 166.7, 167.1 (CꢀO), 186.7, 186.8
(C-3). Anal. Calcd for C31H25BrO10·H2O: C,
56.81; H, 4.15. Found: C, 56.76; H, 4.09.
2. Experimental
Fast-atom bombardment MS spectra
(FABMS) were run on a JMS-HX 110 spec-
1
13
trometer. H and C NMR spectra were mea-
sured with a JNM-A-400 or an A-600 (JEOL)
spectrometer, with tetramethylsilane as an in-
ternal standard. UV spectra were recorded
with a Shimazu UV-3100PC spectrophotome-
ter. Specific rotations were measured with a
JASCO DIP-370 polarimeter (10-cm cell). Ele-
mental analyses were carried out by the micro-
analysis service of the University of Meijo.
Analytical TLC was performed on glass plates
5-Hydroxy-2-(2,3,5-tri-O-benzoyl-i- -ribo-
D
furanosyl)pyran-4-one (3) and 5-hydroxy-2-{5-
[(benzoyloxy)methyl]furan - 2 - yl}pyran - 4 - one
(4).—To a solution of 2 (106.2 mg, 0.1667

S. Kanazawa et al. / Carbohydrate Research 318 (1999) 180–185
183
washed with water, dried over MgSO4, and
concentrated in vacuo to a syrup. This syrup
was separated by PTLC with 3:1 EtOAc–
CHCl3 as eluent.
mmol) in dioxane (3 mL) at 0 °C was added
TFA (2 mL). The mixture was stirred at rt for
6 days, and then the reaction mixture was
poured into ice-water, neutralized with satd aq
NaHCO3 and extracted with CHCl3 (3×10
mL). The extracts were combined, washed
with water, and dried over MgSO4. The ex-
tracts, on evaporation of the solvent, afforded
a brownish oil that was separated by PTLC
with 99:1 CHCl3–MeOH as eluent.
Compound 5. Yield 55.5 mg (34%); Rf 0.70;
1
colorless foam; H NMR (CDCl3): l 2.32 (s, 3
H, CH3), 4.59 (dd, 1 H, J5%a,5%b=12.1, J4%,5%a
=
4.0 Hz, H-5%a), 4.72–4.76 (m, 1 H, H-4%), 4.84
(dd, 1 H, J5%a,5%b=12.1, J4%,5%b=3.3 Hz, H-5%b),
5.03 (d, 1 H, J1%,2%=5.5 Hz, H-1%), 5.78 (dd, 1
H, J2%,3%=J3%,4%=5.5 Hz, H-3%), 5.88 (dd, 1 H,
J1%,2%=J2%,3%=5.5 Hz, H-2%), 6.67 (s, 1 H, H-5),
7.69 (s, 1 H, H-2), 7.36–8.11 (m, 15 H, Ph);
13C NMR (CDCl3): l 20.4 (CH3), 63.4 (C-5%),
72.3, 73.9, 79.7, 80.7 (C-1%, 2%, 3%, 4%), 115.5
(C-5), 128.4–133.5 (Ph, C-4), 141.3 (C-3),
147.9 (C-2), 163.1 (C-6), 165.1, 165.3, 166.1,
167.6 (CꢀO), 172.2 (C-4). FABMS (nitroben-
zyl alcohol as matrix): Calcd for C33H27O11;
599.1553 [MH]. Found: m/z 599.1554 [MH]+.
Anal. Calcd for C33H26O11·0.7H2O: C, 64.92;
H, 4.51. Found: C, 64.86; H, 4.52.
Compound 3. Yield 43.9 mg (48%); color-
1
less foam; H NMR (CDCl3): l 4.59 (dd, 1 H,
J5%a,5%b=12.1, J4%,5%a=3.7 Hz, H-5%a), 4.73–4.76
(m, 1 H, H-4%), 4.87 (dd, 1 H, J5%a,5%b=12.1,
4%,5%b=3.3 Hz, H-5%b), 5.04 (d, 1 H, J1%,2%=5.5
J
Hz, H-1%), 5.79 (t, 1 H, J2%,3%=J3%,4%=5.5 Hz,
H-3%), 5.88 (dd, 1 H, J1%,2%=J2%,3%=5.5 Hz,
H-2%), 6.70 (s, 1 H, H-5), 7.37–8.13 (m, 16 H,
Ph, H-2); 13C NMR (CDCl3): l 63.3 (C-5%),
72.2, 74.0, 79.9, 80.6 (C-1%, 2%, 3%, 4%), 111.4
(C-5), 128.3–133.7 (Ph), 138.2 (C-3), 145.9
(C-2), 163.5 (C-6), 165.0, 165.2, 166.0 (CꢀO),
173.8 (C-4). FABMS (nitrobenzyl alcohol as
matrix): Calcd for C31H25O10: 557.1448 [MH].
Found: m/z 557.1429 [MH]+.
Compound 6. Yield 6.1 mg (6%); Rf 0.55;
1
colorless foam; H NMR (CDCl3): l 2.34 (s, 3
H, CH3), 5.35 (s, 2 H, CH2), 6.65 (d, 1 H,
J3,4=3.3 Hz, furan H-4), 6.84 (s, 1 H, H-5),
6.95 (d, 1 H, J3,4=3.3 Hz, furan H-3), 7.88 (s,
Compound 4. Yield 3.9 mg (8%); colorless
foam; 1H NMR (CDCl3): l 5.36 (s, 2 H, CH2),
6.65 (d, 1 H, J3,4=3.7 Hz, furan H-4), 6.85 (s,
1 H, H-5), 6.95 (d, 1 H, J3,4 =3.7 Hz, furan
H-3), 7.84 (s, 1 H, H-2), 7.43–8.07 (m, 5 H,
Ph); 13C NMR (CDCl3): l 58.1 (CH2), 106.3
(C-5), 113.1, 116.1 (furan C-3, 4), 128.4–133.5
(Ph), 145.7, 146.1, 152.8, 155.7 (C-3, 6, and
furan C-2, 5), 166.0 (CꢀO), 173.6 (C-4).
FABMS (nitrobenzyl alcohol as matrix):
Calcd for C17H13O6: 313.0712 [MH]. Found:
m/z 313.0721 [MH]+.
13
1 H, H-2), 7.43–8.07 (m, 5 H, Ph); C NMR
(CDCl3): l 20.4 (CH3), 58.0 (CH2), 110.2 (C-
5), 113.1, 113.4 (furan C-3, 4), 128.4–133.3
(Ph), 145.5, 146.9, 153.1, 155.1 (C-3, 6, and
furan C-2, 5), 166.0, 167.8 (CꢀO), 172.3 (C-4).
FABMS (nitrobenzyl alcohol as matrix):
Calcd for C19H15O7; 355.0818 [MH]. Found:
m/z 355.0823 [MH]+.
3-Bromo-5-(2,3,5-tri-O-benzoyl-i-
D
-ribo-
furanosyl)-2-furancarboxyaldehyde
(7).—A
solution of 2 (134.0 mg, 0.2104 mmol) in
CH3CN (10 mL) containing five drops of conc
HCl was allowed to stir at 60 °C for 8 h. The
reaction mixture was neutralized with satd aq
NaHCO3 and extracted with CHCl3 (3×10
mL). The extracts were combined, washed
with water, dried over MgSO4, and the solvent
was evaporated in vacuo to give a syrup. This
syrup was purified by PTLC with 99:1
CHCl3–MeOH as eluent. This afforded 22.3
5-Acetoxy-2-(2,3,5-tri-O-benzoyl-i- -ribo-
D
furanosyl)pyran-4-one (5) and 5-acetoxy-2-{5-
(benzoyloxy)methyl]furan-2-yl}pyran-4-one
(6).—To a solution of 2 (172.4 mg, 0.2706
mmol) in dioxane (3 mL) at 0 °C was added
TFA (2 mL). The mixture was stirred at rt for
6 days, and the reaction mixture was concen-
trated. To the residue was added acetic anhy-
dride (5 mL) containing one drop of
anhydrous pyridine, and the mixture was
stirred at rt for 2 h. The reaction mixture was
poured into ice-water, then neutralized with
satd aq NaHCO3 and extracted with CHCl3
(3×10 mL). The extracts were combined,
1
mg (17%) of 7 as a foam; H NMR (CDCl3):
l 4.60 (dd, 1 H, J5%a,5%b=12.5, J4%,5%a=3.8 Hz,
H-5%a), 4.71–4.74 (m, 1 H, H-4%), 4.83 (dd, 1
H, J5%a,5%b=12.5, J4%,5%b=3.1 Hz, H-5%b), 5.32
(d, 1 H, J1%,2%=5.3 Hz, H-1%), 5.83 (t, 1 H,

184
S. Kanazawa et al. / Carbohydrate Research 318 (1999) 180–185
1 H, J1%,2%=5.1 Hz, H-1%), 6.65 (s, 1 H, H-5),
7.93 (s, 1 H, H-2); 13C NMR (CD3OD): l
63.0 (C-5%), 72.7, 76.7, 82.6, 86.3 (C-1%, 2%, 3%,
4%), 111.7 (C-5), 141.3 (C-3), 147.6 (C-2),
168.6 (C-6), 176.7 (C-4). HREIMS Calcd for
C10H12O7: 244.0583. Found: m/z 244.0570.
3-Hydroxymethyl-6-(2,3-O-isopropylidene-
J2%,3%=J3%,4%=5.3 Hz, H-3%), 5.89 (dd, 1 H,
J1%,2%=J2%,3%=5.3 Hz, H-2%), 6.63 (s, 1 H, H-
4), 7.36–8.11 (m, 15 H, Ph), 9.65 (s, 1 H,
CHO); 13C NMR (CDCl3): l 63.4 (C-5%),
72.2, 74.5, 77.2, 80.4 (C-1%, 2%, 3%, 4%), 112.8
(C-3), 115.0 (C-4), 128.5–134.0 (Ph), 148.2
(C-5), 156.7 (C-2), 165.1, 165.3, 166.2 (CꢀO),
i- -ribofuranosyl)-1H-pyridazin-4-one
D
176.2 (CHO). FABMS (nitrobenzyl alcohol
79
(10).—To a solution of deprotected C-nu-
cleoside 8 (47.1 mg, 0.1826 mmol) in acetone
(5 mL) was added PTSA (10 mg), and the
mixture was stirred at rt for 5 h. The reac-
tion mixture was neutralized with satd aq
NaHCO3, and the solvent was evaporated.
The residue was purified by PTLC with 93:7
CHCl3–MeOH as eluent. This afforded 9.5
mg (18%) of 10 as a foam; 1H NMR
(CD3COCD3): l 1.33, 1.55 (each s, each 3
H, CH3), 3.82 (dd, 1 H, J5%a,5%b=11.7,
as
matrix):
24
Calcd
for
C31H BrO9,
24
81
C31H BrO9; 619.0604, 621.0589 [MH].
Found: m/z 619.0586, 621.0565 [MH]+.
3 - Hydroxymethyl - 6 - (i- -ribofuranosyl)-
D
1H-pyridazin-4-one (8).—To a solution of 5
(29.5 mg, 0.04933 mmol) in DMF (0.5 mL)
at 0 °C was added DMF (0.5 mL) contain-
ing one drop of anhydrous hydrazine. The
mixture was stirred at rt for 24 h, and the
reaction mixture was concentrated. The
residue was purified by PTLC with 4:1
CHCl3–MeOH as eluent. This afforded 5.5
mg (44%) of 8 as a foam: umax (MeOH) 270
nm (log m 3.8); [h]D −7.26° (c 0.9, MeOH);
1H NMR (CD3OD): l 3.73 (dd, 1 H,
J
J
4%,5%a=2.9 Hz, H-5%a), 3.89 (dd, 1 H,
5%a,5%b=11.7, J4%,5%b=2.9 Hz, H-5%b), 4.31
(dd, 1 H, J3%,4%=J4%,5%=2.9 Hz, H-4%), 4.51 (s,
2 H, CH2), 4.80 (dd, 1 H, J1%,2%= 4.4, J2%,3%
=
J
5%a,5%b=12.1, J4%,5%a=3.3 Hz, H-5%a), 3.86 (dd,
6.0 Hz, H-2%), 4.88 (d, 1 H, J1%,2%=4.4 Hz,
H-1%), 4.91 (dd, 1 H, J2%,3%=6.0, J3%,4%=4.4
Hz, H-3%), 6.29 (s, 1 H, H-5); FABMS (ni-
trobenzyl alcohol as matrix): Calcd for
C31H25N2O6; 299.1243 [MH]. Found: m/z
299.1254 [MH]+.
1 H, J5%a,5%b=12.1, J4%,5%b=3.3 Hz, H-5%b),
4.02 (dd, 1 H, J1%,2%=6.2, J2%,3%=5.5 Hz, H-
2%), 4.04–4.07 (m, 1 H, H-4%), 4.12 (dd, 1 H,
J3%,4%=4.1, J2%,3%=5.5 Hz, H-3%), 4.64 (s, 2 H,
CH2), 4.71 (d, 1 H, J1%,2%=6.2 Hz, H-1%),
6.52 (s, 1 H, H-5); 13C NMR (CD3OD): l
60.8, 62.6 (CH2), 72.5, 78.4, 81.1, 87.3 (C-1%,
2%, 3%, 4%), 112.5 (C-5), 156.1, 158.5 (C-3, 6),
172.4 (C-4). FABMS (nitrobenzyl alcohol as
matrix): Calcd for C10H15N2O6; 259.0930
[MH]. Found: m/z 259.0937 [MH]+.
5-Hydroxy-2-(2,3-O-isopropylidene-i- -
D
ribofuranosyl)pyran-4-one (11).—This com-
pound was prepared from 9 as described
above for 10; foam, 32%; 1H NMR
(CD3COCD3): l 1.33, 1.52 (each s, each 3
H, CH3), 3.65–3.72 (m, 2 H, H-5%), 4.16–
4.19 (m, 1 H, H-4%), 4.70 (d, 1 H, J1%,2%=3.9
5-Hydroxy-2-(i- -ribofuranosyl)pyran-4-
D
one (9).—To a solution of 5 (39.5 mg, 0.066
mmol) in MeOH (1 mL) was added 28% aq
NH4OH (0.2 mL) at rt for 1 day, and the
reaction mixture was concentrated. The
residue was purified by PTLC with 4:1
CHCl3–MeOH as eluent. This afforded 8.1
mg (50%) of 9 as a foam; umax (MeOH) 220
and 271 nm (log m 3.8 and 3.5); [h]D −13.1°
Hz, H-1%), 4.78 (dd, 1 H, J1%,2%=3.9, J2%,3%
=
4.4 Hz, H-2%), 4.82 (dd, 1 H, J2%,3%=4.4,
J3%,4%=6.2 Hz, H-3%), 6.52 (s, 1 H, H-5), 7.99
(s, 1 H, H-2); FABMS (nitrobenzyl alcohol
as matrix): Calcd for C13H17O7; 285.0974
[MH]. Found: m/z 285.0980 [MH]+.
1
(c 0.8, MeOH); H NMR (CD3OD): l 3.66
Acknowledgements
(dd, 1 H, J5%a,5%b=12.1, J4%,5%a=4.8 Hz, H-
5%a), 3.76 (dd, 1 H, J5%a,5%b=12.1, J4%,5%b=3.3
Hz, H-5%b), 3.96–3.99 (m, 1 H, H-4%), 4.03
(dd, 1 H, J2%,3%=J3%,4%=5.1 Hz, H-3%), 4.14
(dd, 1 H, J1%,2%=J2%,3%=5.1 Hz, H-2%), 4.57 (d,
This work was partly supported by the
Ministry of Education Science, Sports and
Culture of Japan (High-Tech Research Cen-
ter Project).

S. Kanazawa et al. / Carbohydrate Research 318 (1999) 180–185
185
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