Reaction of sugar allyltins with aldehydes under high pressure

Article abstract of DOI:10.1016/j.tetasy.2004.04.020

High-pressure reactions of allyltin derivatives of furanoses with sugar aldehydes affords threo-homoallylic alcohols regardless of the configuration (Z or E) across the double bond of the starting allyltin. Reaction of methyl 2,3-di-O-benzyl-5,6,7-trideox

Full text of DOI:10.1016/j.tetasy.2004.04.020

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 15 (2004) 1719–1727
Reaction of sugar allyltins with aldehydes under high pressure
Sławomir Jarosz,a,* Katarzyna Szewczyk,a Anna Gaweł and Roman Luboradzkib
aInstitute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warszawa, Poland
bInstitute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44, 01-224 Warszawa, Poland
Received 17 March 2004; accepted 19 April 2004
Abstract—High-pressure reactions of allyltin derivatives of furanoses with sugar aldehydes affords threo-homoallylic alcohols
regardless of the configuration (Z or E) across the double bond of the starting allyltin. Reaction of methyl 2,3-di-O-benzyl-5,6,7-
trideoxy-7-(tri-n-butyl)stannyl-hept-5-(Z)-eno-b-D-ribofuranoside 13Z with 2,3:4,5-di-O-isopropylidene-D-arabinose 6 was highly
stereoselective and afforded only one threo-homoallylic alcohol 14, while the same process with E-organometallic 13E furnished
both threo-alcohols: 14 and 15 in the ratio 36:64. This result does not agree with the widely accepted six-membered (chair) transition
state, which predicts the threo-isomers for the reaction of the E-allyltin and erythro for the Z-isomers; however, this result may be
explained by a twisted six-membered transition state.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
suitable for such transformation; the pyranose deriva-
tives (e.g., 5) reacted readily with aldehydes providing
the products (e.g., 8) in high yields and with very high
diastereoselectivities.6 The use of other Lewis acids was
connected with the decomposition of sugar allyltins; this
process can be controlled thus providing useful chiral
synthons, E-dienoaldehydes (e.g., 7),7 as starting mate-
rials in stereocontrolled syntheses of carbobicyclic
derivatives such as 98 or 10.9
Higher carbon sugars are attractive targets with their
synthesis gaining considerable interest over the last
decade. A number of methods leading to such compli-
cated molecules have been developed.1 Over the past
several years, we have proposed a general methodology
for the preparation of higher carbon sugars by coupling
of two sugar sub-units.2 Precursor 3 can be readily
obtained from sugar phosphoranes3 1, phosphonates 4 2,
or vinyltin derivatives of monosaccharides5 4 (Fig. 1).
However, the furanose allyltin derivatives did not react
with the aldehydes in the same way as the pyranoses; in
the presence of BF3ÆOEt2 they underwent decomposition
prior to the reaction with the aldehyde.6 Acid catalysis
for the formation of compounds of type 12 should,
therefore, be avoided and other conditions have to be
evaluated to achieve this transformation (Fig. 3).
Other types of higher sugar precursors, homoallylic
alcohols flanked at both ends with sugar moieties (e.g., 8
in Fig. 2), have recently been prepared by us via a boron
trifluoride catalyzed addition of sugar allyltins to sugar
aldehydes (Fig. 2).6 Only the catalyst BF3ÆOEt2 was
O
O
PPh3
1. Sug'-CHO
Sug
SnBu3
Sug'-CHO
1
Sug
Sug
Sug'
or
2. [O]
O
O
P
4
OMe
OMe
3
functionalization
of the allylic bridge
Sug
higher carbon sugars
2
Figure 1. Methods for the preparation of higher carbon sugars using Wittig-type and stannyl methodology.
* Corresponding author. Tel.: +48-22-632-32-21; fax: +48-22-632-66-81; e-mail: sljar@icho.edu.pl
0957-4166/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.04.020

1720
S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
2. Results and discussion
SnBu3
OMe
6
2.1. Reaction of geometrical isomers (E and Z) of sugar
allyltins with aldehydes under high pressure
O
O
O
BnO
BnO
O
O
The reaction of allylstannanes with aldehydes is usually
catalyzed by Lewis acids.10 It can be performed suc-
cessfully at high temperature,11 high pressure,12 or under
radical conditions.13 The relative configurations of the
products (homoallylic alcohols) in the former two pro-
cesses (Dt, Dp) depend on the geometry of the double
bond of the starting allyltin. It is, however, independent
of the acid catalyzed process.
O
OBn
'Ara'
gluco, manno 'R'
6
BF3 . Et2O
5
LA
6
O
BnO
BnO
Ara
6
R
HO
OBn
The first two processes (Dt, Dp) proceed via a cyclic six-
membered transition state, in which the tin atom coor-
dinates to a carbonyl group. It is evident, therefore, that
both geometrical isomers must form different homoal-
lylic alcohols (Fig. 4-I). Reaction of organostannanes
with aldehydes catalyzed by a Lewis acid proceeds
through a different mechanism. The acidity of the tin
atom on the organostannanes is much lower than that of
any Lewis acid used, hence the carbonyl group is com-
plexed by a Lewis acid and not tin. The open-chain
model leading to the same erythro-isomer, regardless of
the configuration of starting allyltin, is, therefore, pre-
ferred10 (Fig. 4-II).
7
8
OBn
OBn
OBn
BnO
BnO
COR
OBn
R
O
9
10
Figure 2. Behavior of sugar allytins toward Lewis acids in (a) the
absence and (b) the presence of aldehydes.
We decided to study this process using furanose-derived
allyltins: Methyl 2,3-di-O-benzyl-5,6,7-trideoxy-7-(tri-n-
SnBu3
butyl)stannyl-hept-5-(E)- and 5-(Z)-eno-b-D-ribofur-
anosides, 13E, and 13Z, respectively.14 According to the
models presented in Figure 4, the Z-organometallic 13Z
should afford the erythro- and the 13E derivative furnish
the threo-isomers.
H
Ara-CHO 6
Ara
OH
BnO
O
O
BF3 .OEt2
O
O
O
BnO
O
12
11
The reaction of a readily available mixture of both
olefins, 13E/13Z (2:1), with 2,3:4,5-di-O-isopropylidene-
Figure 3.
(I)
(II)
O
O
+
SnBu3
R
R1
H
R
SnBu3
+
R1
H
E orZ
E orZ
∆p or∆t
Lewis acid
-
H
H
+
H
R1
A
O
R
SnBu3
SnBu3
O
O
R1
R1
SnBu3
H
R
R
H
H
E orZ
(E-stannane)
(Z-stannane)
OH
OH
OH
OH
R1
OH
R
R1
R
R
R1
threo
R1
R1
R
R
erythro
erythro
Figure 4. Stereochemical models for the reaction of allyltins with aldehydes under high-pressure I and catalyzed by Lewis acids II.

S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
1721
D
-arabinose 6 was conducted under high pressure and
elevated temperature for 7 days affording a mixture of
two homoallylic alcohols 14 and 15 (ratio: 58:42, overall
yield 93%), to which unexpectedly the threo-configura-
tions were assigned.ꢀ This observation raised a question
about the mechanism of this process, which according to
a widely accepted model (Fig. 4), should lead to ste-
reoisomers with different relative configurations. We
performed, therefore a high-pressure reaction of alde-
hyde 6 with pure geometrical isomers 13Z and 13E with
the results shown in Scheme 1.
SnBu3
5
OMe
5''
O
5'
i.
O
1
O
10
6
O
6
OBn
'Rib'
5
BnO
'Rib'
13Z
OH
O
14
SnBu3
O
Figure 5. ORTEP drawing of 15.
O
i.
6
14
+
O
'Rib'
13E
6
'Rib'
15
On the other hand, the absolute configuration of the
diols can be conveniently established by CD spectros-
copy; the sign of the Cotton effect of the complexes of
the diols with molybdenum tetraacetate allows precise
determination of the geometry of the stereogenic
centers;15;16 both adducts 14 and 15 were, therefore,
converted into the diols 21 and 24 (Scheme 2).
OH
14 : 15 = 36:64
O
Scheme 1. Reagents and conditions: (i) 13 kbar, 57 ꢁC, CH2Cl2, 7 days.
The 13Z-isomer upon reaction with aldehyde 6 afforded
only one stereoisomeric threo-homoallylic alcohol 14 in
97% yield. In the reaction of the 13E-isomer with 6, the
stereoselectivity was much lower with both threo-ad-
ducts 14 and 15 being formed in a 36:64 ratio (overall
yield 91%). Although the threo-product(s) was to be
expected from high pressure reactions of the E-isomers
according to mechanism of this process (Fig. 4-I), it is
hard to explain the formation of such a product with the
same relative stereochemistry from the Z-isomer under
these conditions, unless another mechanism is consid-
ered.
First the free hydroxyl group was blocked as an allyl
ether, because of its stability under a wide variety of
reaction conditions and the possibility of its selective
removal.17 Next both isopropylidene protecting func-
tions were removed by hydrolysis and the resulting tet-
raol subjected to periodate cleavage. Reduction of the
resulting aldehydes with sodium borohydride afforded
alcohols 20 and 23, respectively. The allyl block was
then removed under standard conditions providing diols
21 and 24. The CD spectra of the complexes of these
diols with dimolybdenum tetraacetate shown in Figure 6
clearly indicated at the C6 center an (S)-configuration
for 24 and an (R)-configuration for 21.16
2.2. Determination of the configurations of adducts
14 and 15
The configuration of both isomers 14 and 15 was
established by X-ray crystallography and chemical
correlations. Fortunately, isomer 15 (obtained in the
reaction of 13E with aldehyde 6) was crystalline; its
structure was determined by the X-ray method as shown
in Figure 5.
3. Stereochemical models for the reaction of sugar
allyltins with aldehydes under high pressure
The formation of threo-adducts 14 and 15 from
E-organometallic 13E can be explained using the cyclic
model for such a reaction as shown in Figure 4. The
formation of threo-adduct 14 from the Z-isomer is more
difficult to explain, since according to this cyclic model,
the Z-organometallics should provide the erythro-ad-
ducts. The possibility that the Z-isomer undergoes
isomerization to 13E prior to reaction with the aldehyde
should be also excluded, since 13E upon reaction with 6
gives threo-adducts with low stereoselectivity (14/
15 ¼ 36:64), while selectivity in reaction of 13Z is very
high (97% of only one stereoisomer 14). The cyclic
Having proven the configuration of isomer 15, it was
relatively easy to assign the structure of the product 14.
The geometry at the C5 center in 14 was easily deter-
mined when the stereogenic center at C6 was destroyed.
Oxidation of 14 with PCC gave ketone 16, while oxi-
dation of 15 gave the stereoisomer 17, thus proving
opposite configurations for both homoallylic alcohols at
the C5 atom (Scheme 2).
ꢀ
For determination of the configuration of 14 and 15 see Section 2.2.

1722
S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
2'
1'
O
BnO
O
iii.
6
'Ara'
6
10
OH
iv.
'Rib'
6
5
O
'Rib'
5
BnO
i.
5
H
OR
1
O
OR
O
O
16
20 R = All
21 R = H
MeO
14 R = H
ii.
18 R = All
i.
O
O
'Ara'
iii.
6
6
'Rib'
5
10
6
7
OH
O
'Rib'
5
'Rib'
5
O
OR
OR
O
17
23 R = All
24 R = H
X-Ray assignment (for R=H)
iv.
15 R = H
ii.
19 R = All
Scheme 2. Reagents and conditions: (i) PCC, (CH2Cl)2, 80 ꢁC (58% for 14 and 60% for 15); (ii) AllBr, NaH, DMF; (iii) (1) Hþ, THF/H2O; (2) NaIO4,
Et2O; (3) NaBH4, MeOH; (iv) Pd/C, p-TsOH, MeOH; (iv) Pd/C, p-TsOH, MeOH, 50 ꢁC.
A
A
O
OH
H
H
H
311.6, 0.68
'Ara'
H
0.8
0.4
O
HO
OH
R
'Rib'
'Rib'
SnBu3 'Rib'
A = Bu3SnSug
SnBu3
25-II
OH
24
'Ara'
25-I
0.0
OH
OH
-0.4
-0.8
-1.2
'Ara'
'Ara'
'Rib'
'Rib'
R
OH
21
'Rib'
OH
OH
15
or
25'
313.2, -0.85
OH
or
258
300
350
400
/ nm
450
450
550
'Ara'
'Ara'
'Rib'
25''
'Rib'
OH
OH
14
Figure 6. The CD spectra of the complexes of 21 and 24 with
Mo2(OAc)4.
Figure 7. Stereochemical open-chain models in the Yamamoto reac-
tion.
model, widely accepted for such processes does not
explain the results obtained in the reaction of 13 with 6
and has to be excluded.
alkoxy-aldehydes with allyltin derivatives is dependent
on the nature of the acid. The nonchelating BF3ÆOEt2
predominantly provided the syn (or erythro) adducts,
while TiCl4 afforded the anti (threo) homoallylic alco-
hols as the major products. To explain these results they
proposed an alternative open-chain model, in which the
carbonyl group and the allylstannane moiety are in
synclinal relation.18
Tetraorganostannanes are very weak Lewis acids, but
their acidity can be increased under high pressure. The
process studied by us could therefore be regarded as acid
catalyzed with the Lewis acid being a part of the reacting
molecules (Sug-SnBu3). In the open-chain, an antiperi-
planar model of the acid-catalyzed Yamamoto reaction
(25-I; Lewis acid ¼ second molecule of organostannane
13) adducts with the relative erythro-configuration is
expected.10 The high-pressure reaction of 13Z with 6,
however, afforded the threo-product 14 exclusively.
The exclusive formation of the threo-homoallylic alco-
hols in a high-pressure reaction of isomeric sugar allyl-
tins 13Z and 13E with aldehyde 6 may be explained by a
slightly modified model of Nishigaichi and Takuwa. In
this model one can postulate, that olefinic (allyltin) and
carbonyl fragments of both reacting molecules are syn-
clinal to each other, and this arrangement is stabilized
by complexation of the tin atom (present in the molecule
of 13) to the carbonyl oxygen atom.ꢁ The transition
This could result from another open-chain transition
state having an antiperiplanar arrangement of the car-
bonyl and allylstannane groups: 25-II; this is, however,
very unlikely due to severe steric repulsions between the
arabinose and ribose units (Fig. 7).
ꢁ
Although tetraorganostannanes are very weak Lewis acids (they do
not react with aldehydes without activation), their acidity increases
under high pressure.
Recently, Nishigaichi and Takuwa demonstrated that
the stereochemistry of an acid-catalyzed reaction of

S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
1723
SnBu3
SnBu3
BnO
BnO
BnO
O
H
O
H
BnO
O
O
MeO
MeO
O
O
R
R
O
O
26b
26a
Ryb
Ryb
5
5
(S)
(S)
5
5
Ara
Ara
(R)
(R)
Ara
Ara
(S)
(S)
Ryb
6
6
(R)
(R)
Ryb
6
6
OH
OH
OH
OH
15
14
O
O
O
O
H
O
R
H
H
BnO
H
BnO
R
H
H
BnO
BnO
MeO
O
O
MeO
SnBu3
O
SnBu3
27a
27b
Figure 8. Stereochemical models for the high-pressure reaction of isomeric allylstannanes 13Z and 13E with aldehyde 6.
states for the reaction of the E-oraganostannane 13E
with the aldehyde are represented by the drawings 26a
and 26b in Figure 8. Both of them should provide the
threo-adducts 14 and 15. Analysis of the models indi-
cates, that the steric interaction in these transition states
are comparable, and no significant differentiation be-
tween them should be expected. In fact, reaction of 13E
with 6 afforded 14 and 15 in the ratio 36:64.
or Z) in the allyltin derivative. The reaction of the
Z-organometallic with an aldehyde was highly stereo-
selective and furnished only one homoallylic alcohol,
while the reaction of the E-isomer provided both threo-
products with low selectivity.
5. Experimental
5.1. General
For the reaction of the 13Z-isomer, another two tran-
sition states can be drawn: 27a and 27b, both leading
either to 14 or 15. The unfavorable steric and Coulom-
bic repulsions are much lower in 27b than in 27a
meaning the former (leading to 14) should be highly
favored. This assumption is in full agreement with the
experimental observations; only one threo-stereoiso-
meric homoallylic alcohol 14 was formed in a high-
pressure reaction of 13Z with 6.
NMR spectra were recorded with a Bruker AM 500
spectrometer for solutions in CDCl3 (internal Me4Si)
unless otherwise stated. Most of the resonances were
assigned by COSY (1H–1H) and/or HETCOR, and
DEPT correlations. The 1H- and 13C-aromatic reso-
nances occurring at typical d values were omitted for
simplicity. The relative configurations of the protons
were determined by NOESY experiments. Mass spectra
were recorded with an AMD-604 [AMD Intectra
GmbH, Germany; [LSIMS (m-nitrobenzyl alcohol was
used as a matrix to which sodium acetate was added)]
mass spectrometers. Optical rotations were measured
with a JASCO DIP Digital Polarimeter for chloroform
solution (c ꢀ 1:5, unless otherwise stated) at room
temperature. CD Spectra were measured between 650
and 230 nm at room temperature with a Jasco J715
spectropolarimeter using DMSO solutions in cells of 0.2
path length (spectral band width 1 nm, sensitivity
10 ꢁ 10ꢂ6 or 20 ꢁ 10ꢂ6 DA unit/nm). Depending on the
4. Conclusion
The reaction of sugar allyltin derivatives of furanoses
can only be successfully achieved under high pressure
(13 kbar) and at elevated temperature. This process
proceeds not according to the widely accepted cyclic
chair transition state, but to a highly distorted model
with the synclinal arrangement of the carbonyl and vinyl
fragments. According to such model homoallylic alco-
hols, the relative threo-configurations are formed
regardless of the geometry across the double bond (E

1724
S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
S/N-ratio, the k-scan speed was 0.2 or 0.5 nm/s. For CD
measurements, the chiral diol (1–3 mg) was dissolved in
a solution of the stock [Mo2(OAc)4] complex (6–7 mg) in
DMSO (10 mL) so that the molar ratio of the stock
complex to the diol was about 1:0.3–1:0.7. As the true
concentrations of the individual optically active com-
plexes are not known, apparent De0 values are given,
calculated from the total ligand concentration and
assuming 100% complexation. [Mo2(OAc)4] and DMSO
(Uvasol) were commercially available from Fluka AG
and E. Merck, respectively, and used without further
purification.
{4 ꢁ s, 4 ꢁ 3H, [2 ꢁ C(CH3)]}; 13C NMR (125 MHz) d:
2 ꢁ 137.9 (2 ꢁ Cq benzyl), 133.7 (C-10), 118.9 (C-20), 110.2,
108.9 [2 ꢁ C(CH3)], 106.5 (C-1), 81.8 (C-8), 81.4 (C-3),
80.4 (C-4), 2 ꢁ 80.3 (C-2, C-7), 76.2 (C-9), 72.2, 72.0
(2 ꢁ CH2C6H5), 71.6 (C-9), 67.8 (C-10), 54.9 (OCH3),
53.2 (C-5), 26.9, 26.7, 26.3, 25.1 [2 ꢁ C(CH3)]. Anal.
Calcd for C33H44O9: C, 67.78; H, 7.58. Found: C, 67.64;
H 7.51.
5.2.2. Methyl 2,3-di-O-benzyl-5-deoxy-7,8:9,10-di-O-iso-
propylidene-(5S)-vinyl-b-
D
-ribo-D-gluco-deca-1,4-furano-
side 15. (ORTEP Fig. 6). ½aꢃ ¼ þ16:6; 1H NMR
Column chromatography was performed on silica gel
(Merck, 70–230 mesh). Organic solutions were dried
over anhydrous magnesium or sodium sulfate.
D
0
0
0
(200 MHz) d: 5.85 (ddd, 1H, J1 ;2a 10.1 Hz, J10;2b 17.0 Hz
H-10), 5.22 (d, 1H, H-2a0) 5.05 (d, 1H, H-2b0), 4.95 (s,
1H, H-1), 4.58 (m, 4H, 2 ꢁ CH2C6H5), 4.39 (dd, 1H, J3;4
7.1 Hz, J4;5 4.5 Hz, H-4), 4.18–3.72 (m, 7H, H-3, H-6, H-
7, H-8, H-9, H-10a, H-10b), 3.77 (d, 1H, J2;3 4.5 Hz, H-
2), 3.32 (s, 3H, OCH3), 2.52 (m, 1H, H-5), 2.47 (br s, 1H,
Methyl 2,3-di-O-benzyl-5,6,7-trideoxy-7-(tri-n-butyl)-
stannyl-hept-5-(E)- and 5-(Z)-eno-b-
(13E and 13Z, respectively) were prepared according to
Ref. 14. 2,3:4,5-Di-O-isopropylidene-
-arabinose19
was obtained by periodate cleavage of 3,4:5,6-di-O-iso-
D-ribofuranosides
OH), 1.39, 21.37, 1.33 {4 ꢁ s, 4 ꢁ 3H, [2 ꢁ C(CH3)]}; 13
C
D
6
NMR (125 MHz) d: 2 ꢁ 137.7 (2 ꢁ Cq benzyl), 134.3 (C-
10), 119.7 (C-20), 109.7, 109.5 [2 ꢁ C(CH3)], 105.9 (C-1),
81.4 (C-4), 80.4 (C-8), 79.2 and 79.0 (C-2, C-3), 78.4 (C-
7), 76.9 (C-9), 72.3, 72.2 (2 ꢁ CH2C6H5), 71.3 (C-6), 67.5
(C-10), 55.0 (OCH3), 49.5 (C-5), 27.5, 27.3, 26.6, 25.5
[2 ꢁ C(CH3)]. Anal. Calcd for C33H44O9: C, 67.78; H,
7.58. Found: C 67.80; H 7.49.
propylidene-
onolactone.
D D-gluc-
-glucitol, readily available20 from
5.2. High-pressure reaction of organostannanes 13E and
13Z with aldehyde 6
A solution of organostannane 13 (1 mmol) and aldehyde
6 (0.95 mmol) in methylene chloride (10 mL) was placed
in a piston–cylinder type apparatus21 and kept under
13 kbar hydrostatic pressure at 57 ꢁC for 7 days. After
this time the solvent was evaporated to dryness and the
residue chromatographed [first with hexane–diethyl
ether, 500:1 (to remove all impurities containing tin) and
hexane–ethyl acetate, 6:1] to afford pure isomers.
5.3. Crystal assignment for 15
Crystallographic data for the structure of 15 have been
deposited with the Cambridge Crystallographic Data
Centre as supplementary publication No CCDC 232692.
Diffraction data were collected at 100 K by using a
Kappa CCD diffractometer with graphite monochro-
mated Mo Ka radiation. Structure was solved by direct
methods (SHELXS-97) and refined on F2 by full-matrix
least-squares method (SHELXL-97). The structure con-
tains two symmetry independent molecules of 15 both
having the same absolute configuration and the water
molecule bind via hydrogen bonds to the one molecule
of 15. Water molecule was refined with occupancy 0.25.
Formula: 2C33H44O9Æ0.25H2O, monoclinic, space group
• Reaction of 13Z afforded 14 in 97% yield.
• Reaction of 13E afforded 14 (33%) and 15 (58%).
• Reaction of a 2:1 mixture 13E/13Z afforded 14 (54%)
and 15 (39%). When this process was stopped after
ca. 50% conversion (3 days) the proportion of 14/15
was 3:2 (1H NMR estimation; integration of the sig-
nal of OMe at d: 3.33 and 3.32 ppm for 14 and 15,
respectively) with the initial ratio of E:Z-isomeric tins
13 was preserved (d OMe ¼ 3.34 and 3.32 ppm for
the E and Z-isomers), which indicated that no Z to
E-isomerization took place during the high-pressure
reaction.
ꢀ
P21, a ¼ 9:04ꢁ70ð2Þ, b ¼ 23:9720ð7Þ, c ¼ 14:9150ð4Þ A,
3
ꢀ
b ¼ 98:646ð2Þ , V ¼ 3197:92ð15Þ A , Z ¼ 2, F ð000Þ ¼
1261, l(MoKa) ¼ 0.088 mmꢂ1, R1 ¼ 0:0652 [I > 2rðIÞ],
wR2 ¼ 0:1439 for all data.
5.2.1. Methyl 2,3-di-O-benzyl-5-deoxy-7,8:9,10-di-O-iso-
propylidene-(5R)-vinyl-b-
5.4. Oxidation of alcohols 14 and 15
D
-ribo-D-manno-deca-1,4-furan-
oside 14. ½aꢃ ¼ þ8:6; 1H NMR (for numbering see
To a solution of alcohol 14 or 15 (0.1 mmol) in ethylene
dichloride (2 mL), pyridinum chlorochromate (PCC,
43 mg, 0.2 mmol) was added and the heterogeneous
mixture stirred at 80 ꢁC until TLC (hexane–ethyl ace-
tate, 4:1) indicated disappearance of the starting mate-
rial and the formation of a new less polar product (2 h).
The mixture was cooled, diluted with methylene chloride
(2 mL), filtered through Celite, and the crude product
purified by column chromatography (hexane–ethyl ace-
tate, 4:1).
D
Scheme 2) d: 5.86 (m, 1H, J1 ;2a 9.7 Hz, H-10), 5.20 (m,
2H, H-2a0,H-2b0), 4.95 (d, 1H, J1;2 1.0 Hz, H-1), 4.62 and
4.54 (2 ꢁ d, 2 ꢁ 1H, JA;B 11.9 Hz, CH2C6H5), 4.33(m,
3H, H-4, CH2C6H5), 4.17 (dd, 1H, J10a;b 8.5 Hz, J9;10a
6.1 Hz, H-10a), 4.05 (m, 1H, H-9), 3.99 (m, 2H, H-6, H-
10b), 3.94 (dd, 1H, J2;3 4.7 Hz, J3;4 5.4 Hz, H-3), 3.85 (dd,
1H, H-2), 3.77 (dd, 1H, J7;8 9.0 Hz, J8;9 7.9 Hz H-8), 3.71
(dd, 1H, J6;7 8.8 Hz, H-7), 3.43 (br s, 1H, OH), 3.33 (s,
3H, OCH3), 2.53 (m, 1H, H-5), 1.44, 1.35, 1.33, 1.32
0
0

S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
1725
5.4.1. Methyl 2,3-di-O-benzyl-5-deoxy-7,8:9,10-di-O-iso-
propylidene-(5R)-vinyl-6-oxo-b- -ribo- -arabino-deca-1,
4-furanoside 16. Obtained from 14 in 58% yield from 14.
chromatography (hexane–ethyl acetate, 5:1). Yield:
89%; ½aꢃ ¼ ꢂ6:0; 1H NMR d: 5.90 (m, 1H, J2 ;3a
00
0
D
D
D
00
§
00 00
0
0
10.9 Hz, J2 ;3 17.2 Hz, H-2 ), 5.77 (ddd, 1H, J1 ;2a
½aꢃ ¼ ꢂ53:1; H NMR d: 5.71 (ddd, 1H, J1 ;2a 10.0 Hz,
10.3 Hz, J10;2b 17.2 Hz, J1 ;5 9.8 Hz, H-10), 5.27 (m, 1H,
1
0
0
0
0
D
J10;2b 17.1 Hz, H-10), 5.29 (dd, 1H, H-2b0), 5.21 (dd, 1H,
J3a00;3b 1.5 Hz, H-3b00), 5.20 (dd, 1H, J2a0;2b 2.2 Hz, H-
2a0), 5.18 (dd, 1H, H-2b0), 5.13 (m, 1H, H-3a00), 4.92 (d,
1H, J1;2 1.2 Hz, H-1), 4.63, 4.55 (2 ꢁ d, 2 ꢁ 1H, JA;B
12.1 Hz, CH2C6H5), 4.42, 4.39 (2 ꢁ d, 2 ꢁ 1H, JA;B
0
00
0
J2a0;2b 1.4 Hz, H-2a0), 4.87 (dd, 1H, J1;2 1.4 Hz, H-1), 4.62
0
(dd, 1H,J3;4 6.4 Hz, J4;5 10.0 Hz, H-4), 4.61, 4.54 (2 ꢁ d,
2 ꢁ 1H, JA;B 12.0 Hz, CH2C6H5), 4.55 (d, 1H, J7;8 6.0 Hz,
H-7), 4.42 (br s, 2H, CH2C6H5), 4.30 (dd, 1H, J8;9
6.3 Hz, H-8), 4.19 (ddd, 1H,J9;10b 5.6 Hz, H-9), 4.08 (dd,
1H, J9;10a 6.4 Hz,J10a;b 8.6 Hz, H-10a), 3.92 (dd, 1H, H-
00
00 00
12.0 Hz, CH2C6H5), 4.30 (dd, 1H, J1a00;1b 12.3 Hz, J1a ;2
5.2 Hz, H-1a00), 4.22 (m, 3H, H-4, H-8, H-9), 4.13 (dd,
1H, J1b ;200 6.0 Hz, H-1b00), 4.01 (dd, 1H, J10a;b 8.1 Hz,
00
0
10b), 3.89 (dd, 1H, J2;3 4.7 Hz, H-3), 3.82 (dd, 1H, J1 ;5
J9;10a 6.5 Hz, H-10a), 3.95 (dd, 1H, J9;10b 7.2 Hz, H-10b),
3.89 (dd, 1H, J3;4 5.4 Hz, H-3), 3.84 (dd, 1H, J5;6 1.4 Hz,
J6;7 9.0 Hz, H-6), 3.83 (dd, 1H, J2;3 4.7 Hz, H-2), 3.73
(dd, 1H, J7;8 6.0 Hz, H-7), 3.33 (s, 3H, OCH3), 2.46 (m,
1H, H-5), 1.42, 1.37, 1.36, 1.34 {4 ꢁ s, 4 ꢁ 3H,
[2 ꢁ C(CH3)]}; 13C NMR d: 137.8, 137.7 (2 ꢁ Cq benzyl),
134.6 (C-200), 133.9 (C-10), 119.1 (C-20), 116.9 (C-300),
109.6 and 109.3 [2 ꢁ C(CH3)], 106.6 (C-1), 81.9 (C-3),
80.2 and 80.0 (C-2, C-4, C-6, C-8), 77.8 (C-7), 76.2 (C-9),
74.0 (C-100), 72.3 and 72.2 (2 ꢁ CH2C6H5), 65.2 (C-10),
55.2 (OCH3), 53.3 (C-5), 27.7, 27.5, 26.3, 25.4
[2 ꢁ C(CH3)]; ESI (MeOH) m=z: 647.3221 [C36H48O9Na
(MþNaþ) requires: 647.3191].
9.7 Hz, H-5), 3.78 (dd, 1H, H-2), 3.32 (s, 3H, OCH3),
1.44, 1.41, 1.37, 1.34 {4 ꢁ s, 4 ꢁ 3H, [2 ꢁ C(CH3)]}; 13C
NMR d: 206.3 (C@O), 137.7, 137.6 (2 ꢁ Cq benzyl), 131.7
(C-10), 120.1 (C-20), 111.4, 109.8 [2 ꢁ C(CH3)], 106.6 (C-
1), 81.9 (C-7), 80.5 (C-3), 80.4 (C-4), 79.5 (C-2), 77.4 (C-
8), 76.5 (C-9), 72.2, 72.1 (2 ꢁ CH2C6H5), 66.5 (C-10),
59.7 (C-5), 55.6 (OCH3), 27.2, 26.4, 26.3, 25.2
[2 ꢁ C(CH3)]; m=z: 605.2701 [C33H42O9Na (MþNaþ)
requires: 605.2726].
5.4.2. Methyl 2,3-di-O-benzyl-5-deoxy-7,8:9,10-di-O-iso-
propylidene-(5S)-vinyl-6-oxo-b-
4-furanoside 17. Obtained from 15 in 60% yield.
D
-ribo- -arabino-deca-1,
D
1
0
0
½aꢃ ¼ þ32:2; H NMR d: 5.86 (ddd, 1H, J1 ;2a 10.0 Hz,
5.5.2. Methyl 6-O-allyl-2,3-di-O-benzyl-5-deoxy-7,8:9,
D
J10;2b 17.2 Hz, H-10), 5.23 (dd, 1H, J2a0;2b 1.5 Hz, H-2a0),
5.03 (dd, 1H, H-2b0), 4.86 (s, 1H, H-1), 4.62 and 4.59
(2 ꢁ d, 2 ꢁ 1H, JA;B 12.0 Hz, CH2C6H5), 4.58 (dd, 1H, H-
4), 4.56, 4.54 (2 ꢁ d, 2 ꢁ 1H, JA;B 11.8 Hz, CH2C6H5),
4.46 (d, 1H, H-7), 4.19 (dd, 1H, J7;8 6.6 Hz, H-8), 4.14
(ddd, 1H,J8;9 5.8 Hz, H-9), 4.06 (dd, 1H, J9;10a 6.3 Hz, H-
0
0
10-di-O-isopropylidene-(5S)-vinyl-b-
1,4-furanoside 19. Was obtained analogously from 15 in
D
-ribo- -gluco-deca-
D
79% yield. ½aꢃ ¼ þ12:3; 1H NMR d: 5.89 (m, 2H, H-10,
D
H-200), 5.21 (m, 1H, J200;3b 17.2 Hz, J100;3b 3.4 Hz, H-3b00),
00
00
5.15 (dd, 1H, J1 ;2a 10.3 Hz, J2a0;2b ¼ ꢂ2:1 Hz, H-2a0),
0
0
0
5.07 (dd, 1H, J10;2b 17.3 Hz, H-2b0), 5.06 (m, 1H, J2 ;3a
0
00
00
9.0 Hz, H-3a00), 4.89 (d, 1H, J1;2 0.7 Hz, H-1), 4.65, 4.59
(2 ꢁ d, 2 ꢁ 1H, JA;B 12.0 Hz, CH2C6H5), 4.55 and 4.43
(2 ꢁ d, 2 ꢁ 1H, JA;B 11.8 Hz, CH2C6H5), 4.37 (dd, 1H,
0
10a), 4.00 (dd, 1H, J3;4 7.1 Hz, H-3), 3.91 (dd, 1H, J1 ;5
9.9 Hz, J4;5 5.2 Hz, H-5), 3.89 (dd, 1H, J10a;10b 8.6 Hz,
J9;10b 6.2 Hz, H-10b), 3.78 (dd, 1H, J1;2 0.6 Hz, J2;3
4.6 Hz, H-2), 3.31 (s, 3H, OCH3), 1.43, 1.37, 1.34, 1.32
{4 ꢁ s, 4 ꢁ 3H, [2 ꢁ C(CH3)]}; 13C NMR d: 207.2
(C@O), 137.8, 137.7 (2 ꢁ Cq benzyl), 132.3 (C-10), 120.2
(C-20), 111.5, 109.8 [2 ꢁ C(CH3)], 106.3 (C-1), 82.0 (C-7),
80.2 (C-4), 80.4 (C-4), 79.5 (C-2), 78.8 (C-3), 78.1 (C-8),
76.4 (C-9), 72.2. 72.1 (2 ꢁ CH2C6H5), 66.5 (C-10), 55.8
(C-5), 55.3 (OCH3), 27.2, 26.4, 26.3, 25.2 [2 ꢁ C(CH3)];
m=z: 605.2707 [C33H42O9Na (MþNaþ) requires:
605.2726].
J
3;4 7.2 Hz, J4;5 4.8 Hz, H-4), 4.15 (dd, 1H, J6;7 4.6 Hz, J7;8
7.0 Hz, H-7), 4.12 (m, 3H, H-1a00, H-1b00, H-10b), 4.07
(m, 1H, H-9), 3.97 (dd, 1H, J2;3 4.8 Hz, H-3), 3.89 (dd,
1H, J9;10a 6.4 Hz, J10a;b 8.1 Hz, H-10a), 3.85 (dd, 1H, J8;9
7.3 Hz, H-8), 3.79 (dd, 1H, H-2), 3.59 (dd, 1H, J5;6
0
5.6 Hz, H-6), 3.33 (s, 3H, OCH3), 2.68 (ddd, 1H, J1 ;5
10.1 Hz, H-5), 1.41, 1.37, 1.35, 1.34 {4 ꢁ s, 4 ꢁ 3H,
[2 ꢁ C(CH3)]}; 13C NMR (125 MHz) d: 137.9 and 137.8
(2 ꢁ Cq benzyl), 135.3, 135.2 (C-10, C-200), 119.1 (C-20),
115.9 (C-300), 109.6, 109.2 [2 ꢁ C(CH3)], 106.0 (C-1), 81.1
(C-7), 81.0 (C-4), 79.7 (C-2), 79.3 (C-3), 78.9 (C-6), 78.2
(C-8), 77.0 (C-9), 73.3 (C-100), 72.3 and 72.2
(2 ꢁ CH2C6H5), 67.7 (C-10), 55.1 (OCH3), 49.5 (C-5),
27.3, 27.2, 26.4, 25.4 [2 ꢁ C(CH3)]; ESI (MeOH) m=z:
647.3213 [C36H48O9Na (MþNaþ) requires: 647.3191].
5.5. Conversion of adducts 14 and 15 into the diols 21 and
24
5.5.1. Methyl 6-O-allyl-2,3-di-O-benzyl-5-deoxy-7,8:9,
-ribo-D-manno-deca-
10-di-O-isopropylidene-(5R)-vinyl-b-
D
1,4-furanoside 18. To a solution of alcohol 14 (2 mmol)
in dry DMF (30 mL), sodium hydride (50% suspension
in mineral oil; 3 mmol) was added followed by a cata-
lytic amount of imidazole (20 mg), and the mixture
stirred for 30 min. Allyl bromide (0.26 mL, 3.0 mmol)
was then added dropwise and stirring prolonged for
another 30 min. Excess hydride was decomposed with
water (0.5 mL) and the mixture partitioned between
water (30 mL) and ether (100 mL). The organic phase
was separated, washed with water (15 mL), dried, and
concentrated and crude product 18 isolated by column
5.5.3. Methyl 6-O-allyl-2,3-di-O-benzyl-5-deoxy-5-vinyl-
D
b-
-ribo-L-threo-hept-1,4-furanoside 20. Compound 18
(360 mg, 0.57 mmol) was dissolved in a mixture of THF/
water (2:1, 25 mL) containing concentrated sulfuric acid
(0.25 mL) and boiled under reflux for 20 h. After cooling
to room temperature it was neutralized with triethyl
amine. To this solution of a tetraol, diethyl ether
§
Description bis (00) refers to the allylic blocking group.

1726
S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
0
0
0
(10 mL) was added followed by sodium periodate
(460 mg, 2.3 mmol), and the mixture stirred vigorously
for 30 min at rt. This was diluted with ether (30 mL), and
then washed with brine (15 mL) and water (15 mL).
Crude aldehyde was reduced with sodium borohydride
(40 mg, 0.086 mmol) under standard conditions. Chro-
matographic purification (hexane–ethyl acetate, 4:1–2:1)
afforded alcohol 20 in 70% overall yield (180 mg,
5.20 (dd, 1H, J1 ;2a 10.3 Hz, J2a0;2b 1.9 Hz, H-2a0), 5.15
(dd, 1H, J10;2b 17.2 Hz, H-2b0), 4.89 (s, 1H, H-1), 4.63,
0
4.56 (2 ꢁ d, 2 ꢁ 1H, JA;B 11.9 Hz, CH2C6H5), 4.45, 4.41
(2 ꢁ d, 2 ꢁ 1H, JA;B 11.3 Hz, CH2C6H5), 4.28 (dd, 1H, H-
4), 3.94 (dd, 1H,J3;4 7.0 Hz, H3), 3.89 (m, 1H, H-6), 3.82
(d, 1H, J2;3 4.6 Hz, H-2), 3.61 (m, 2H, H-7a, H-7b), 3.34
(s, 3H, OCH3), 2.77 (d, 1H, J6;OH 4.1 Hz, OH), 2.31
(ddd, 1H, J5;6 3.7 Hz, H-5), 2.03 (m, 1H, OH); 13C NMR
d: 137.6 and 137.3 (2 ꢁ Cq benzyl), 133.8 (C-10), 119.1 (C-
20), 105.4 (C-1), 81.3 (C-4), 80.1 (C-3), 79.4 (C-2), 72.4
(C-6), 72.35, 72.3 (2 ꢁ CH2C6H5), 65.1 (C-7), 55.5
(OCH3), 52.3 (C-5). m=z (ESI): 437.1958 C24H30O6Na
(MþNaþ) requires: 437.1935].
1
0.4 mmol). ½aꢃ ¼ ꢂ19:1; H NMR d: 5.94 (m, 1H, H-
D
200), 5.79 (ddd, 1H, H-10), 5.27 (m, 1H, J200;3b 17.2 Hz, H-
00
3b00), 5.15 (m, 1H, J2 ;3a 10.4 Hz, H-3a00), 5.13 (dd, 1H,
00
00
J1 ;2a 10.0 Hz, J2a0;2b 2.0 Hz, H-2a0), 5.08 (dd, 1H, J10;2b
0
0
0
0
17.2 Hz, H-2b0), 4.92 (d, 1H, J1;2 1.3 Hz, H-1), 4.63, 4.55
(2 ꢁ d, 2 ꢁ 1H, JA;B 12.0 Hz, CH2C6H5), 4.93 (s, 2H,
CH2C6H5), 4.33 (dd, 1H, J3;4 5.9 Hz, J4;5 10.3 Hz, H-4),
4.19 (m, 1H, J1a ;2 5.3 Hz, J1a00;3b 1.7 Hz, H-1a00), 4.14
5.5.6. Methyl 2,3-di-O-benzyl-5-deoxy-5-vinyl-b- -ribo-
D
00
00 00
0
00
00
(m, 1H, J1a00;1b 12.7 Hz, J1b ;200 6.0 Hz, J1b ;3a00 1.3 Hz, H-
1b00), 3.89 (dd, 1H, J2;3 4.8 Hz, H-3), 3.83 (dd, 1H, H-2),
3.82 (m, 1H, H-6), 3.65 (m, 1H, H-7a), 3.56 (m, 1H, H-
D
-threo-hept-1,4-furanoside 24. Obtained analogously
from 23 in 54% overall yield. ½aꢃ ¼ þ30:5; 1H NMR d:
D
5.79 (ddd, 1H, H10), 5.20 (dd, 1H, J1 ;2a 0.3 Hz, J2a0;2b
0
0
0
0
0
7b), 3.34 (s, 3H, OCH3), 2.16 (ddd, 1H, J5;6 2.9 Hz, J1 ;5
2.0 Hz, H-2a0), 4.97 (dd, 1H, J10;2b 17.3 Hz, H-2b0), 4.86
(s, 1H, H-1), 4.66, 4.59 (2 ꢁ d, 2 ꢁ 1H, JA;B 12.0 Hz,
CH2C6H5), 4.55, 4.38 (2 ꢁ d, 2 ꢁ 1H, JA;B 11.7 Hz,
CH2C6H5), 4.37 dd, 1H, J4;5 3.7 Hz, H-4), 3.96 (dd,
1H,J3;4 8.5 Hz, H-3), 3.91 (m, 1H, H-6), 3.78 (d, 1H, J2;3
4.5 Hz, H-2), 3.62 (m, 1H, H-7a), 3.55 (ddd, 1H, J6;7b
7.9 Hz, J7a;b 11.9 Hz, J7b;OH 4.0 Hz, H-7b), 3.32 (s, 3H,
OCH3), 2.91 (d, 1H, J6;OH 2.8 Hz, OH), 2.32 (ddd, 1H,
10.2 Hz, H-5), 1.83 (m, 1H, OH); 13C NMR d: 2 ꢁ 137.7
(2 ꢁ Cq benzyl), 135.2 (C-200), 134.6 (C-10), 118.2 (C-20),
116.8 (C-300), 106.7 (C-1), 81.5 (C-3), 80.3 (C-4), 80.1 (C-
2), 79.1 (C-6), 72.9 (C-100), 72.3, 72.1 (2 ꢁ CH2C6H5),
64.1 (C-7), 55.2 (OCH3), 53.9 (C-5); m=z (ESI): 477.2230
[C27H34O6Na (MþNaþ) requires: 477.2248]. Anal.
Calcd for C27H34O6: C, 71.34; H, 7.53. Found: C, 71.58;
H 7.60.
J5;6 3.9 Hz, J5;1 9.9 Hz, H-5), 2.08 (br s, 1H, OH); 13C
0
NMR d: 137.6, 137.4 (2 ꢁ Cq benzyl), 133.2 (C-10), 120.0
(C-20), 106.1 (C-1), 81.6 (C-4), 78.7 and 78.6 (C-2, C-3),
73.4 (C-6), 72.50, and 72.4 (2 ꢁ CH2C6H5), 64.4 (C-7),
55.2 (OCH3), 49.2 (C-5). m=z (ESI): 437.1948
C24H30O6Na (MþNaþ) requires: 437.1935].
5.5.4. Methyl 6-O-allyl-2,3-di-O-benzyl-5-deoxy-5-vinyl-
b-
D
-ribo-D-threo-hept-1,4-furanoside 23. Prepared anal-
1
ogously from 19 in 80% overall yield. ½aꢃ ¼ þ48:3; H
D
NMR d: 5.91 (m, 1H, H-200), 5.73 (ddd, 1H, H-10), 5.25
(m, 1H, J200;3b 17.2 Hz, J3a00;3b 1.6 Hz, H-3b00), 5.14 (m,
00
00
1H, J2 ;3a 0.3 Hz, H-3a00), 5.13 (dd, 1H, J1 ;2a 10.3 Hz,
00
00
0
0
J2a0;2b 2.0 Hz, H-2a0), 4.94 (dd, 1H, J10;2b 17.2 Hz, H-2b0),
4.83 (s, 1H, H-1), 4.66, 4.59 (2 ꢁ d, 2 ꢁ 1H, JA;B 12.1 Hz,
CH2C6H5), 4.56, 4.37 (2 ꢁ d, 2 ꢁ 1H, JA;B 11.9 Hz,
CH2C6H5), 4.39 (dd, 1H, J3;4 8.2 Hz, J4;5 3.3 Hz, H-4),
0
0
Acknowledgements
This work was supported by Grant 4 T09A 107 23 from
the State Committee for Scientific Research, which is
gratefully acknowledged.
4.12 (m, 1H, J1a00;1b 14.0 Hz, J1a ;2 5.5 Hz, H-1a00), 4.02
00
00 00
(m, 1H, J1b ;200 5.9 Hz, H-1b00), 3.91 (dd, 1H, J2;3 4.6 Hz,
H-3), 3.76 (d, 1H, H-2), 3.69 (m, 2H, H-7a, H-7b), 3.31
00
0
(s, 3H, OCH3), 2.51 (ddd, 1H, J5;6 5.3 Hz, J1 ;5 9.1 Hz, H-
5), 2.24 (m, 1H, OH); 13C NMR d: 137.8, 137.7
(2 ꢁ Cq benzyl), 135.1 (C-200), 134.3 (C-10), 119.3 (C-300),
116.8 (C-20), 106.1 (C-1), 81.0 (C-6), 79.0 (C-2), 79.0 (C-
4), 78.9 (C-3), 72.35, 72.3 (2CH2C6H5), 71.2 (C-100), 62.3
(C-7), 55.2 (OCH3), 48.1 (C-5). m=z (ESI): 477.2243
[C27H34O6Na (MþNaþ) requires: 477.2248].
References and notes
1. Gyorgydeak, Z.; Pelyvas, I. Monosaccharide Sugars:
Chemical Synthesis by Chain Elongation, Degradation and
Epimerization; Academic, 1998, this book covers the
literature up to 1997; For more recent papers, see, for
example: Marquis, Ch.; Picasso, S.; Vogel, P. Synthesis
1999, 1441; Blackwell, H. E.; O’Leary, D. J.; Chatterjee,
A. K.; Washenfelder, R. C.; Bussmann, D. A.; Grubbs,
R. H. J. Am. Chem. Soc 2000, 122, 58; Maria, E. J.;
da Silva, A. D.; Fourrey, J.-L. Eur. J. Org. Chem. 2000,
627; Joergensen, M.; Iversen, E. H.; Madsen, R. J. Org.
Chem. 2001, 66, 4625; Marco-Contelles, J.; Opazo, E.;
Arroyo, N. Tetrahedron 2001, 57, 4729; Gerber-Lemaire,
S.; Ainge, S. W.; Glanzmann, C.; Vogel, P.. Helv. Chim.
Acta 2002, 85, 417, and references cited therein.
5.5.5. Methyl 2,3-di-O-benzyl-5-deoxy-5-vinyl-b-
L
D
-ribo-
-threo-hept-1,4-furanoside 21. Allyl ether 20 (0.1 mmol)
was dissolved in a mixture of methanol/water (5/
0.5 mL), to which Pd/C (50 mg), and p-toluenesulfonic
acid were added and the mixture heated at 45–50 ꢁC for
2 h. This was then cooled to rt, diluted with methanol
(5 mL) and passed through Celite. The filtrate was
neutralized with Et3N, concentrated, and the residue
purified by column chromatography (hexane–ethyl ace-
tate 1:1–1:2) to afford diol 21 as an oil in 44% overall
2. Jarosz, S. J. Carbohydr. Chem. 2001, 20, 93.
3. Jarosz, S.; Mootoo, D. R.; Fraser-Reid, B. Carbohydr.
Res. 1986, 147, 59; Jarosz, S. Carbohydr. Res. 1988,
183, 201; Jarosz, S. Carbohydr. Res. 1992, 224, 73;
1
yield. ½aꢃ ¼ þ10:1; H NMR d: 5.82 (ddd, 1H, H-10),
D

S. Jarosz et al. / Tetrahedron: Asymmetry 15 (2004) 1719–1727
1727
ꢁ
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