Synthesis of carba-β-D- and L-idopyranosides by rearrangement of unsaturated sugars

Article abstract of DOI:10.1016/S0957-4166(99)00479-6

The triisobutylaluminium- (TIBAL) and titanium(IV)-promoted conversions of 6-deoxyhex-5-enopyranosides into highly functionalised cyclohexane derivatives provide intermediates for the synthesis of enantiomerically pure carba-sugars. The preparation of enantiomerically pure methyl carba-β-D-idopyranoside 1, methyl carba-β-L-idopyranoside 2 and 5'a-carbadisaccharide 3 is reported. Copyright (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0957-4166(99)00479-6

TETRAHEDRON:
ASYMMETRY
Pergamon
Tetrahedron: Asymmetry 11 (2000) 283–294
Synthesis of carba-β-D- and L-idopyranosides by rearrangement
of unsaturated sugars
Matthieu Sollogoub, Alan James Pearce, Alexandre Hérault and Pierre Sinaÿ ∗
École Normale Supérieure, Département de Chimie, associé au CNRS, 24 rue Lhomond, 75231 Paris Cedex 05, France
Received 21 October 1999; accepted 28 October 1999
Abstract
The triisobutylaluminium- (TIBAL) and titanium(IV)-promoted conversions of 6-deoxyhex-5-enopyranosides
into highly functionalised cyclohexane derivatives provide intermediates for the synthesis of enantiomerically
pure carba-sugars. The preparation of enantiomerically pure methyl carba-β-D-idopyranoside 1, methyl carba-
β-L-idopyranoside 2 and 50a-carbadisaccharide 3 is reported. © 2000 Elsevier Science Ltd. All rights reserved.
1. Introduction
Complex oligosaccharides are currently emerging as promising therapeutic agents.1–4 A possible
drawback of such drugs is their vulnerability towards in vivo degradation by glycosidases and this
has prompted the search for non-hydrolysable oligosaccharide mimetics. Carba-sugars5 are carbocyclic
sugar mimetics in which the endocyclic oxygen atom of the sugar is replaced by a methylene group.
As a consequence of this substitution, carba-sugars are hydrolytically stable analogues of their parent
sugars and are of interest as tools for the elucidation of the (spatial) role of sugar hydroxyl groups
in biological systems.6 Furthermore, it is possible to substitute the pyranoid-ring oxygen of one sugar
in an oligosaccharide with a methylene group, whilst retaining significant biological activity.7 Carba-
oligosaccharides as mimetics of biologically important systems are, therefore, attractive synthetic targets.
It is now well recognised that idose residues (as L-iduronic acid) play a crucial role in determining the
biological activity of glycosaminoglycans.8 The critical importance of L-iduronic acid in the antithrombin
III binding sequence of heparin9–11 and FGF-2 binding of heparan sulfate12 has been specifically
demonstrated. This has prompted us to explore the synthesis of carba-idopyranosyl derivatives in general.
Ogawa has reported the synthesis of racemic carba-β-idopyranose13,14 based on cyclohexane deriva-
tives from the Diels–Alder cycloaddition of furan and acrylic acid. Paulsen reported the synthesis of
carba-α- and β-L-idopyranoses by anionic cyclisation of acyclic carbohydrates using an intramolecular
∗
Corresponding author. Fax: +33 1 44 32 33 97; e-mail: pierre.sinay@ens.fr
0957-4166/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0957-4166(99)00479-6
tetasy 3115

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Horner–Emmons olefination.15 A protected carba-β-D-idopyranose was obtained as a minor diastereomer
by radical cyclisation of an acyclic carbohydrate.16 Perhaps the most elegant syntheses of carba-β-
L-idopyranose were provided by Ferrier17 and Barton;18 the direct rearrangement of 6-deoxyhex-5-
enopyranoses into enantiomerically pure cyclohexanones (the so-called Ferrier-II reaction19) was fol-
lowed by homologation to give the protected carba-sugars. This homologation strategy, coupled with our
recent developments in the triisobutylaluminium- (TIBAL)20–22 and titanium(IV)23-promoted conversion
of carbohydrates into carbocycles24 has led us to a novel and versatile synthesis of enantiomerically pure
carba-idopyranosides. This paper reports: (i) the synthesis of both enantiomers of partially protected
carba-β-D- 1 and L-idopyranosides 2 from D-glucose; and (ii) the synthesis of 50a-carbadisaccharide 3
from D-maltose.
The synthesis of methyl carba-β-D-idopyranoside 1 requires carbocyclisation of unsaturated C-
glycoside 4, followed by unmasking of the carboxylic acid and reduction (Scheme 1). Synthesis of methyl
carba-β-L-idopyranoside 2 requires carbocyclisation of the 6-deoxyhex-5-enopyranoside 5 followed by
stereoselective introduction of the hydroxymethyl group at C-5; synthesis of the 50a-carbadisaccharide 3
would follow an analogous strategy (Scheme 2).
Scheme 1.
Scheme 2.

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285
2. Results and discussion
2.1. Synthesis of methyl carba-β-D-idopyranoside 1
Synthesis of the unsaturated C-glycoside 4 required the introduction of furan at C-1 of D-
glucopyranose which was conveniently achieved by simple glycosylation of furan with 1,6-di-O-acetyl-
2,3,4-tri-O-benzyl-D-glucopyranose 625 in the presence of TMSOTf26 to give the α-C-glycoside 7 in
71% yield. Standard deacetylation of 7 and iodination using Garegg’s conditions27 gave iodide 9 which
underwent elimination with sodium hydride in DMF to afford the alkene 4 (58% yield from 7). We
recently reported that C-glycosides of 6-deoxyhex-5-enopyranoses undergo smooth TIBAL-mediated
carbocyclisation provided that the aglycon is sufficiently electron-donating in nature.22 Furan is known
to stabilise α-carbocations28 and we, therefore, anticipated that alkene 4 would undergo TIBAL-induced
rearrangement. Indeed, when 4 was treated with TIBAL, the desired cyclohexane 10 was obtained as the
major product in 83% yield (Scheme 3).
Scheme 3. (i) Furan, 4 Å molecular sieves, TMSOTf, CH3CN, −40°C→−20°C; (ii) MeONa, MeOH, rt, 2 h; (iii) I2, PPh3,
imidazole, toluene, 70°C, 30 min; (iv) NaH, DMF, rt, 2 h; (v) TIBAL, toluene, 50°C, 30 min
Methylation of alcohol 10 with methyl iodide in DMF containing sodium hydride gave the methyl
ether 11 (96% yield). Oxidative cleavage of the furan 11 with ozone revealed the masked carboxylic acid
which was immediately methylated to give the fully protected methyl carba-β-D-iduronate 12 in 62%
yield. This, therefore, constitutes a new synthetic approach to the synthesis of carba-sugar analogues of
iduronic acid. Reduction of the ester 12 with lithium aluminium hydride then gave methyl carba-β-D-
idopyranoside 13 in 76% yield (Scheme 4).†
2.2. Synthesis of methyl carba-β-L-idopyranoside 2
The ketone 14 was obtained in excellent yield by the Ti(IV)-promoted non-reductive rearrangement
of the readily available 6-deoxyhex-5-enopyranoside 5 as previously reported.23 Standard synthetic
strategies18 for one-carbon homologation of ketone 14 using Wittig reagents were unsuccessful due to
preferential elimination of the methoxy group. However, exocyclic alkene 15 was obtained in 73% yield
†
1
Hydrogenolysis of a small quantity of 13 afforded methyl carba-β-D-idoside 1 which showed identical H and 13C NMR
spectra to its enantiomer 2.

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Scheme 4. (i) MeI, NaH, DMF, rt, 1 h; (ii) O3, CH2Cl2, MeOH, −78°C, 15 min; then KHCO3, MeI, DMF, rt, 5 h; (iii) LiAlH4,
Et2O, rt, 4 h; (iv) H2, Pd/C, MeOH, rt, 2 h
by methylenation of ketone 14 with the Tebbe reagent.29 Hydroboration of alkene 15 with BH3·THF
occurred from the less hindered β-face and after oxidative work-up with NaOH/H2O2 gave the protected
methyl carba-β-L-idopyranoside 16 in 60% yield. Finally, debenzylation of 16 by hydrogenation over
Pd/C afforded methyl carba-β-L-idopyranoside 2 in 75% yield (Scheme 5).
Scheme 5. (i) Cl3TiOiPr, CH2Cl2, −78°C, 15 min (see Ref. 23); (ii) Tebbe reagent, toluene, THF, pyr., −45°C→rt; (iii)
BH3·THF, THF, rt, 1 h; then NaOH, H2O2, 0°C→rt, 1 h; (iv) H2, Pd/C, MeOH, rt, 2 h
2.3. Synthesis of 50a-carbadisaccharide 3
The key intermediate ketone 17 was obtained from methyl 2,3,6-tri-O-benzyl-4-O-(2,3,4-tri-O-benzyl-
6-deoxy-α-D-xylo-hex-5-enopyranosyl)-α-D-glucopyranoside 18 by TIBAL-promoted reductive re-
arrangement and oxidation with pyridinium chlorochromate (PCC) as previously reported.21
Methylenation of ketone 17 with the Tebbe reagent gave the exocyclic alkene 19 in 56% yield,
which underwent hydroboration with BH3·THF and subsequent oxidation with NaOH/H2O2 to give
the protected 50a-carbadisaccharide 3 in 48% isolated yield (Scheme 6). Analysis of vicinal coupling

M. Sollogoub et al. / Tetrahedron: Asymmetry 11 (2000) 283–294
287
constants in the 1H NMR spectra for 50a-carbadisaccharide 3 indicated that the carba-β-L-idopyranosyl
ring adopted a 1C4-conformation [all trans-diaxial couplings were observed for H50a(ax): J1 ,5 a(ax) 11.3
0
0
0
0
0
0
and J5 ,5 a(ax)=J5 a(ax),5 a(eq) 12.0 Hz].
Scheme 6. (i) TIBAL, toluene, 50°C, 4 h; then PCC, DCM (see Ref. 21); (iii) Tebbe reagent, THF, pyr., −45°C→rt; (iv)
BH3·THF, THF, rt; then NaOH, H2O2, 0°C→rt
3. Conclusions
The synthesis of methyl carba-β-D-idopyranoside 1 from D-glucose highlights the use of furan as:
(i) a suitable aglycon donor for the TIBAL-promoted rearrangement of alkene 4; and (ii) a masked
carboxylic acid. The synthetic strategy (Schemes 3 and 4) conveniently avoids the use of the more
expensive L-glucose (following the synthetic strategy illustrated in Scheme 5, used for the enantiomeric
D-idopyranoside 2).
Preparation of carba-L-idopyranose 2 from D-glucose demonstrates the use of titanium(IV)-promoted
conversion of carbohydrates into carbocycles.
This work establishes a new methodology for the synthesis of carba-sugar analogues of iduronic acid
(12 is a fully protected methyl carba-β-D-iduronate and 16 is a presursor of carba-L-iduronic acid).
This preparation of 3 completes the synthesis of a 50a-carbadisaccharide using the direct TIBAL-
promoted rearrangement of unsaturated disaccharide 18 as the key step. We are currently exploring
the application of this methodology to the direct synthesis of carba-oligosaccharides as mimetics of
biologically active heparin fragments.

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4. Experimental
4.1. General
Melting points were recorded on a Büchi 510 apparatus and are uncorrected. Optical rotations
were measured on a Perkin–Elmer 241 digital polarimeter with a path length of 1 dm. Mass spectra
were recorded on a Nermag R10-10 spectrometer, using chemical ionisation with ammonia. Elemental
analyses were performed by the Service d’Analyse de l’Université Pierre et Marie Curie, 75252 Paris
Cedex 05, France. NMR spectra were recorded on a Bruker AM-400 (400 and 100.6 MHz, for 1H and
1
13C, respectively) or a Bruker AC-250 (250 and 63 MHz, for H and 13C, respectively) using TMS as
internal standard. TLC was performed on silica gel 60 F254 (Merck) and developed by charring with conc.
H2SO4. Flash column chromatography was performed using silica gel 60 (230–400 mesh, Merck).
4.2. 2-(6-O-Acetyl-2,3,4-O-benzyl-α-D-glucopyranosyl)furan 7
1,6-O-Acetyl-2,3,4-O-benzyl-α,β-D-glucopyranose 625 (1.5 g, 2.81 mmol) was dissolved in anhy-
drous acetonitrile (20 mL) containing 4 Å molecular sieves (3 g) and furan (0.65 mL, 8.43 mmol) at
room temp. under argon. After stirring for 1 h, the mixture was cooled to −40°C and TMSOTf (0.69
mL, 3.37 mmol) was added dropwise. The mixture was then allowed to warm to −20°C when TLC
(AcOEt:cyclohexane, 3:7) indicated completion of the reaction. Triethylamine (1 mL) was added and
the mixture was warmed to room temp. and filtered (Celite®). DCM (250 mL) was added and then
washed with water (2×50 mL). The solvent was removed in vacuo to afford a residue which was
purified by flash chromatography (AcOEt:cyclohexane, 1:9) to give 2-(6-O-acetyl-2,3,4-O-benzyl-α-D-
glucopyranosyl)furan 7 (1.08 g, 71%) as a colourless solid: mp 107°C (Et2O/pentane); [α]20 +66 (c 1.0,
D
CHCl3); δH (250 MHz, CDCl3) 7.39 (d, 1H, JA,B=1.8 Hz, H-A), 7.34–7.13 (m, 15H, H arom.), 6.47
(d, 1H, JC,B=3.3 Hz, H-C), 6.28 (dd, 1H, H-B), 5.04 (d, 1H, J1,2=6.4 Hz, H-1), 4.98 (d, 1H, J=10.7
Hz, -CHPh), 4.82 (d, 1H, J=10.7 Hz, -CHPh), 4.79 (d, 1H, J=10.7 Hz, -CHPh), 4.60 (d, 1H, J=11.7 Hz,
-CHPh), 4.54 (d, 1H, J=11.7 Hz, -CHPh), 4.49 (d, 1H, J=10.7 Hz, -CHPh), 4.23–4.09 (m, 3H, H-3, H-6a,
H-6b), 3.87 (dd, 1H, J2,3=9.6 Hz, H-2), 3.60–3.52 (m, 1H, H-5), 3.49 (t, 1H, J4,5=10.1 Hz, H-4), 1.95 (s,
3H, Ac); δC (63 MHz, CDCl3) 170.7 (Ac), 150.3 (C-D), 142.9 (C-A), 138.6, 137.9, 137.8 (3×s, C-arom.
quat.), 128.5–127.7 (15×d, Ph), 111.9 (C-C), 110.2 (C-B), 82.8 (C-3), 79.4 (C-2), 77.6 (C-5), 75.6, 75.1,
72.9 (3×t, CHPh), 71.6 (C-4), 70.0 (C-1), 63.3 (C-6), 20.9 (CH3); m/z 560 (M+NH4)+; found: C, 72.90;
H, 6.28; C33H34O7 requires: C, 73.04; H, 6.31%.
4.3. 2-(2,3,4-O-Benzyl-α-D-glucopyranosyl)furan 8
A catalytic amount of sodium (20 mg) was added to a solution of 7 (765 mg, 1.41 mmol) in methanol
(20 mL). After stirring at room temp. for 2 h, the solution was neutralised with IR 120 resin and
filtered. The solvent was removed in vacuo and the residue was purified by flash chromatography
(AcOEt:cyclohexane, 3:7) to afford 2-(2,3,4-O-benzyl-α-D-glucopyranosyl)furan 8 (640 mg, 91%) as
20
D
a colourless oil: [α] +66 (c 1.2, CHCl3); δH (250 MHz, CDCl3) 7.38 (d, 1H, JA,B=1.5 Hz, H-A),
7.32–7.13 (m, 15H, H arom.), 6.47 (d, 1H, JC,B=3.2 Hz, H-C), 6.28 (dd, 1H, H-B), 5.04 (d, 1H, J1,2=6.5
Hz, H-1), 4.96 (d, 1H, J=10.9 Hz, -CHPh), 4.82 (d, 1H, J=10.8 Hz, -CHPh), 4.79 (d, 1H, J=11.1 Hz,
-CHPh), 4.60 (d, 1H, J=11.7 Hz, -CHPh), 4.58 (d, 1H, J=10.9 Hz, -CHPh), 4.56 (d, 1H, J=11.7 Hz,
-CHPh), 4.18 (t, 1H, J3,4=9.4 Hz, J3,2=9.4 Hz, H-3), 3.84 (dd, 1H, H-2), 3.75–3.52 (m, 2H, H-6a H-6b),
3.52 (t, 1H, J4,5=9.3 Hz, H-4), 3.39 (dt, 1H, J5,6=3.3 Hz, H-5), 1.67 (s, 1H, OH); δC (63 MHz, CDCl3)

M. Sollogoub et al. / Tetrahedron: Asymmetry 11 (2000) 283–294
289
150.3 (C-D), 142.7 (C-A), 138.6, 137.9, 137.8 (3×s, C-arom. quat.), 128.3–127.5 (15×d, Ph), 111.5 (C-
C), 110.0 (C-B), 82.5 (C-3), 79.4 (C-2), 77.7 (C-5), 75.4, 75.0, 73.5 (3×t, CHPh), 72.8 (C-4), 69.8 (C-1),
62.0 (C-6); m/z 518 (M+NH4)+; found: C, 74.32; H, 6.49; C31H32O6 requires: C, 74.38; H, 6.44%.
4.4. 2-(2,3,4-O-Benzyl-6-deoxy-6-iodo-α-D-glucopyranosyl)furan 9
Imidazole (0.21 g, 3.07 mmol), triphenylphosphine (0.40 g, 1.53 mmol) and iodine (0.29 g, 1.13 mmol)
were added to a solution of alcohol 8 (512 mg, 1.02 mmol) in anhydrous toluene (5 mL) at room temp.
under argon. After stirring at 70°C for 30 min, TLC (AcOEt:cyclohexane, 1:2) indicated completion of
the reaction. The reaction mixture was cooled to room temp. and saturated sodium thiosulfate (5 mL) was
added. After stirring for 5 min, AcOEt (25 mL) was added and the organic layer was then washed with
water (15 mL), dried (MgSO4), filtered and the solvent was removed in vacuo. The residue was purified
by flash chromatography (AcOEt:cyclohexane, 8:92) to afford 2-(2,3,4-O-benzyl-6-deoxy-6-iodo-α-D-
glucopyranosyl)furan 9 (556 mg, 89%) as a colourless oil which was used immediately: δH (250 MHz,
CDCl3) 7.38 (d, 1H, JA,B=1.7 Hz, H-A), 7.29–7.11 (m, 15H, H arom.), 6.47 (d, 1H, JC,B=3.2 Hz, H-C),
6.28 (dd, 1H, H-B), 5.08 (d, 1H, J1,2=6.5 Hz, H-1), 4.96 (d, 1H, J=10.9 Hz, -CHPh), 4.90 (d, 1H, J=10.8
Hz, -CHPh), 4.77 (d, 1H, J=10.8 Hz, -CHPh), 4.69 (d, 1H, J=10.7 Hz, -CHPh), 4.59 (d, 1H, J=11.7 Hz,
-CHPh), 4.51 (d, 1H, J=11.7 Hz, -CHPh), 4.22 (t, 1H, J3,4=J3,2=9.1 Hz, H-3), 3.86 (dd, 1H, H-2), 3.42
(t, 1H, J4,5=9.1 Hz, H-4), 3.33 (d, 2H, J6,5=3.5 Hz, H-6), 3.05 (dt, 1H, H-5); δC (63 MHz, CDCl3) 150.5
(C-D), 142.9 (C-A), 138.6, 138.1, 137.9 (3×s, C-arom. quat.), 128.5–127.7 (15×d, Ph), 111.8 (C-C),
110.2 (C-B), 82.4 (C-3), 81.7 (C-2), 79.6 (C-5), 75.6, 75.5, 73.0 (3×t, CHPh), 71.4 (C-4), 69.9 (C-1), 8.9
(C-6); m/z 628 (M+NH4)+.
4.5. 2-(2,3,4-Tri-O-benzyl-6-deoxy-α-D-xylo-hex-5-enopyranosyl)furan 4
Sodium hydride (350 mg, 8.7 mmol, 60% in mineral oil) was added to a vigorously stirred solution of
iodide 9 (533 mg, 0.87 mmol) in anhydrous DMF (5 mL) at room temp. After 2 h, TLC (toluene:AcOEt,
98:2) indicated completion of the reaction. The reaction mixture was cooled to 0°C and methanol (30 mL)
was added dropwise. The solvent was removed in vacuo and the residue was partitioned between DCM
(50 mL) and water (50 mL). The aqueous layer was extracted with DCM (2×50 mL) and the combined
extracts were washed with brine (50 mL), dried (MgSO4), filtered and the solvent was removed in vacuo.
The residue was purified by flash chromatography (toluene:AcOEt, 9:1) to afford 2-(2,3,4-tri-O-benzyl-
20
D
6-deoxy-α-D-xylo-hex-5-enopyranosyl)furan 4 (302 mg, 72%), as a colourless oil: [α] −42 (c 1.3,
CHCl3); δH (250 MHz, CDCl3) 7.34–7.13 (m, 16H, H arom.+H-A), 6.39 (d, 1H, JC,B=3.4 Hz, H-C),
6.28 (dd, 1H, JB,A=1.8 Hz, H-B), 5.12 (d, 1H, J1,2=4.8 Hz, H-1), 4.72 (d, 1H, J=11.4 Hz, -CHPh), 4.69
(s, 2H, -CH2Ph), 4.64 (d, 1H, J=11.9 Hz, -CHPh), 4.61 (s, 1H, H-6a), 4.55 (s, 1H, H-6b), 4.54 (d, 1H,
J=10.8 Hz, -CHPh), 4.49 (d, 1H, J=10.8 Hz, -CHPh), 4.01–3.82 (m, 3H, H-2, H-3, H-4); δC (63 MHz,
CDCl3) 154.5 (C-5), 142.3–110.0 (22C arom.), 94.2 (C-6), 81.0, 78.9, 78.2, 74.4, 73.7, 72.6, 71.9; m/z
500 (M+NH4)+; found: C, 77.08; H, 6.36; C31H30O5 requires: C, 77.15; H, 6.27%.
4.6. 2-[1D-(1,2,4,5/3)-2,3,4-Tri-O-benzyl-2,3,4,5-tetrahydroxy-cyclohexyl]furan 10
TIBAL (2.1 mL, 2.1 mmol, 1 M in toluene) was added to a stirred solution of 4 (200 mg, 0.41 mmol) in
anhydrous toluene (2 mL) at room temp. under argon. The mixture was heated at 50°C for 30 min, when
TLC (AcOEt:cyclohexane, 3:7) indicated completion of the reaction. The mixture was cooled to room
temp. and water (5 mL) was added dropwise over 15 min. AcOEt (5 mL) was added and the aqueous

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M. Sollogoub et al. / Tetrahedron: Asymmetry 11 (2000) 283–294
layer was extracted with AcOEt (2×10 mL). Combined extracts were dried (MgSO4), filtered and the
solvent was removed in vacuo. The residue was purified by flash chromatography (cyclohexane:AcOEt,
9:1) to afford 2-[1D-(1,2,4,5/3)-2,3,4-tri-O-benzyl-2,3,4,5-tetrahydroxy-cyclohexyl]furan 10 (167 mg,
20
D
83%), as a colourless oil: [α] −7 (c 0.3, CHCl3); δH (250 MHz, CDCl3) 7.32–6.99 (m, 16H, arom.
H+H-A), 6.24 (dd, 1H, JB,A=1.8 Hz, JC,B=3.2 Hz, H-B), 6.24 (d, 1H, H-C), 4.57 (d, 1H, J=11.6 Hz,
-CHPh), 4.44 (d, 1H, J=12.0 Hz, -CHPh), 4.36 (d, 1H, J=11.5 Hz, -CHPh), 4.35 (d, 1H, J=12.0 Hz,
-CHPh), 4.15 (d, 1H, J=12.0 Hz, -CHPh), 4.08 (d, 1H, J=12.0 Hz, -CHPh), 3.90 (dddd, 1H, J5,6a=12.0
Hz, J5,OH=10.6 Hz, J6b,5=3.8 Hz, J5,4=2.7 Hz, H-5), 3.83–3.72 (m, 2H, H-2 H-3), 3.45 (br s, 1H, H-4),
3.18 (br d, 1H, J1,6a=12.0 Hz, H-1), 2.39 (d, 1H, OH), 2.20 (q, 1H, J6a,6b=12.0 Hz, H-6b), 1.84 (dt, 1H,
J1,6a=3.9 Hz, H-6a); δC (63 MHz, CDCl3) 155.8 (C-D), 140.3 (C-A), 138.2, 137.8, 137.7 (3×s, C-arom.
quat.), 128.3–127.7 (15×d, Ph), 110.2, 105.8 (C-C, C-B), 73.7, 72.4, 72.3, 72.3, 67.6, 35.5, 26.7; m/z
1
502 (M+NH4)+, 485 (M+H)+; found: C, 75.75; H, 6.72; C31H32O5·3 H2O requires: C, 75.75; H, 6.90%.
4.7. 2-[1D-(1,2,4,5/3)-2,3,4-Tri-O-benzyl-5-O-methyl-2,3,4,5-tetrahydroxy-cyclohexyl] furan 11
Sodium hydride (17 mg, 0.42 mmol, 60% in mineral oil) was added to a vigorously stirred solution of
10 (101 mg, 0.21 mmol) and iodomethane (20 µL, 0.31 mmol) in anhydrous DMF (1 mL) at room temp.
After 1 h, TLC (cyclohexane:AcOEt, 7:3) indicated completion of the reaction and methanol (5 mL) was
added dropwise. The mixture was partitioned between Et2O (10 mL) and water (10 mL). The aqueous
layer was extracted with Et2O (3×10 mL) and the combined extracts dried (MgSO4), filtered and the
solvent was removed in vacuo. The residue was purified by flash chromatography (AcOEt:cyclohexane,
1:9), to afford 2-[1D-(1,2,4,5/3)-2,3,4-tri-O-benzyl-5-O-methyl-2,3,4,5-tetrahydroxy-cyclohexylfuran 11
20
D
(100 mg, 96%), as a colourless oil: [α] −12 (c 0.8, CHCl3); δH (400 MHz, CDCl3) 7.92–7.26 (m, 16H,
arom. H+H-A), 6.37 (dd, 1H, JB,A=1.8 Hz, JC,B=3.2 Hz, H-B), 6.23 (d, 1H, H-C), 4.74 (s, 1H, -CHPh),
4.68 (d, 1H, J=12.3 Hz, -CHPh), 4.65 (d, 1H, J=12.3 Hz, -CHPh), 4.55 (d, 1H, J=11.5 Hz, -CHPh),
4.47 (d, 1H, J=11.6 Hz, -CHPh), 4.29 (s, 1H, -CHPh), 3.93 (t, 1H, J3,2=J2,4=3.8 Hz, H-3), 3.87–3.82
(m, 2H, H-2 H-4), 3.62 (dt, 1H, J5,6a=10.7 Hz, J5,4=J5,6b=3.5 Hz, H-5), 3.34 (s, 3H, OMe), 3.28 (dt, 1H,
J1,6a=11.7 Hz, J1,2=J1,6b=3.3 Hz, H-1), 2.49 (q, 1H, J6a,6b=11.7 Hz, H-6a), 1.94–1.86 (m, 1H, H-6b); δC
(100 MHz, CDCl3) 156.0 (C-D), 140.3 (C-A), 138.8, 138.6, 138.0 (3×s, C-arom. quat.), 129.7–127.0
(15×d, Ph), 110.4, 106.0 (C-C, C-B), 77.8, 72.8, 72.3, 72.0, 56.3, 36.2, 23.1; m/z 499 (M+H)+; found: C,
77.03; H, 6.92; C32H34O5 requires: C, 77.08; H, 6.87%.
4.8. Methyl (carba-5a methyl 2,3,4-tri-O-benzyl-β-D-idopyranosyl)uronate 12
Ozone gas was bubbled through a solution of furan 11 (92 mg, 0.18 mmol) in MeOH (3 mL) and
CH2Cl2 (6 mL) at −78°C until the solution remained blue in colour. Oxygen was then bubbled through
the solution for 1 min and then DMS (50 µL) was added. The solution was allowed to warm to room
temp. and the solvent was removed in vacuo. The residue was dissolved in DMF (3 mL), and MeI
(59 µL, 0.95 mmol) and KHCO3 (111 mg, 1.11 mmol) were added. After stirring for 5 h at room
temp., TLC (cyclohexane:AcOEt, 7:3) indicated completion of the reaction. The solvent was removed
in vacuo and the residue was partitioned between CH2Cl2 (5 mL) and water (5 mL). The organic layer
was dried (MgSO4), filtered and the solvent was removed in vacuo. The residue was purified by flash
chromatography (AcOEt:cyclohexane, 15:85), to afford methyl (carba-5a methyl 2,3,4-tri-O-benzyl-β-
20
D
D-idopyranosyl)uronate 12 (56 mg, 62%), as a colourless oil: [α] −14 (c 0.5, CHCl3); δH (400 MHz,
CDCl3) 7.40–7.26 (m, 15H, H arom.), 4.73 (d, 1H, J=12.3 Hz, -CHPh), 4.63 (d, 1H, J=12.3 Hz, -CHPh),
4.62 (d, 1H, J=12.0 Hz, -CHPh), 4.58 (d, 1H, J=11.7 Hz, -CHPh), 4.55 (d, 1H, J=11.7 Hz, -CHPh), 4.48

M. Sollogoub et al. / Tetrahedron: Asymmetry 11 (2000) 283–294
291
(d, 1H, J=12.0 Hz, -CHPh), 3.99 (br s, 1H, H-3), 3.88 (br s, 1H, H-2), 3.74 (br s, 1H, H-4), 3.69 (s, 3H,
OMe), 3.50 (dt, 1H, J5,6a=10.3 Hz, J5,4=J5,6b=3.3 Hz, H-5), 3.37 (s, 3H, OMe), 2.84 (dt, 1H, J1,6a=10.8
Hz, J1,2=J1,6b=3.8 Hz, H-1), 2.49 (td, 1H, J6a,6b=12.3 Hz, H-6a), 1.94–1.86 (m, 1H, H-6b); δC (100 MHz,
CDCl3) 173.0 (CO2Me), 138.8, 138.4, 138.0 (3×s, C-arom. quat.), 128.4–127.3 (15×d, Ph), 77.6 (C-5),
76.3 (C-2), 73.1, 72.8, 72.3 (3×t, CH2Ph), 56.6, 51.6 (2×OMe), 42.5 (C-1), 26.9 (C-6); m/z 491 (M+H)+;
found: C, 77.03; H, 6.92; C30H34O6 requires: C, 77.08; H, 6.87%.
4.9. Carba-5a methyl 2,3,4-tri-O-benzyl-β-D-idopyranoside 13
LiAlH4 (4 mg, 0.1 mmol) was added to a solution of ester 12 (18 mg, 0.04 mmol) in Et2O (1 mL)
at 0°C. After stirring at room temp. for 4 h, TLC (cyclohexane:AcOEt, 7:3) indicated completion of the
reaction. The mixture was cooled to 0°C and quenched by the dropwise addition of water (5 mL). The
aqueous layer was extracted with AcOEt (3×20 mL), washed with brine (2×10 mL) and the combined
extracts were dried (MgSO4), filtered and the solvent was removed in vacuo. The residue was purified
by flash chromatography (AcOEt:cyclohexane, 3:7), to afford carba-5a methyl 2,3,4-tri-O-benzyl-β-D-
20
D
idopyranoside 13 (13 mg, 76%), as a colourless oil: [α] −3 (c 0.3, CHCl3); δH (400 MHz, CDCl3)
7.41–7.30 (m, 15H, H arom.), 4.83 (d, 1H, J=11.0 Hz, -CHPh), 4.77 (d, 1H, J=11.5 Hz, -CHPh), 4.76 (d,
1H, J=11.0 Hz, -CHPh), 4.74 (s, 2H, -CH2Ph), 4.61 (d, 1H, J=11.6 Hz, -CHPh), 4.06 (t, 1H, J3,2=J3,4=7.5
Hz, H-3), 3.99 (ddd, 1H, J6a,6b=11.6 Hz, J=7.0 Hz, J=3.5 Hz, H-6a), 3.69 (ddd, 1H, J=8.3 Hz, J=4.1 Hz,
H-6b), 3.66 (dd, 1H, J4,5=5.2 Hz, H-4), 3.58 (dt, 1H, J1,5aa=5.8 Hz, J1,5ab=J1,2=2.9 Hz, H-1), 3.53 (dd,
1H, H-2), 3.44 (s, 3H, OMe), 2.30–2.23 (m, 1H, H-5), 2.07 (dt, 1H, J5aa,5ab=14.4 Hz, J1,5aa=J5,5aa=5.8
Hz, H-5aa), 1.47 (ddd, 1H, J5,5ab=4.9 Hz, H-5ab); δC (100 MHz, CDCl3) 138.7, 138.6, 138.2 (3×s, C-
arom. quat.), 128.4–127.6 (15×d, Ph), 77.3, 74.9, 73.0, 72.9, 64.5, 57.5, 38.9, 26.0; m/z 480 (M+NH4)+;
found: C, 75.30; H, 7.22; C29H34O5 requires: C, 75.29; H, 7.41%.
4.10. Carba-5a methyl 2,3,4-tri-O-benzyl-6-deoxy-α-D-xylo-hex-5-enopyranoside 15
Pyridine (25 µL) and then Tebbe reagent29 (5 mL, 5 mmol, 1.0 M in toluene) [prepared from titanocene
dichloride (6.2 g, 24.9 mmol) and trimethylaluminium (26 mL, 52 mmol, 2.0 M in toluene)] were added
to a solution of ketone 1423 (750 mg, 1.68 mmol) in anhydrous toluene (3.5 mL) and THF (1.5 mL) at
−45°C under argon. After stirring for 1 h at −45°C, 1 h at 0°C and finally, 30 min at room temp., TLC
(cyclohexane:AcOEt, 5:1) indicated completion of the reaction. The reaction mixture was cooled to 0°C
and aqueous sodium hydroxide (1 mL, 15%) was cautiously added dropwise. The mixture was warmed
to room temp. and diluted with CH2Cl2 (100 mL). After stirring for 15 min the mixture was filtered
through Celite® and MgSO4 washing with CH2Cl2 (2×50 mL). The solvent was removed in vacuo and
the residue was purified by flash chromatography (AcOEt:cyclohexane, 1:6) to afford carba-5a methyl
2,3,4-tri-O-benzyl-6-deoxy-α-D-xylo-hex-5-enopyranoside 15 (545 mg, 73%), as a white solid: mp 84°C
20
D
(Et2O/pentane); [α] −45 (c 1.0, CHCl3); δH (400 MHz, CDCl3) 7.90–7.43 (m, 15H, H arom.), 5.33
(d, 1H, J6a,6b=1.4 Hz, H-6a), 4.99 (d, 1H, H-6b), 4.90 (s, 2H, -CH2Ph), 4.81 (d, 1H, J=12.2 Hz, -CHPh),
4.79 (d, 1H, J=12.1 Hz, -CHPh), 4.76 (d, 1H, J=12.5 Hz, -CHPh), 4.75 (d, 1H, J=11.5 Hz, -CHPh),
3.91–3.89 (m, 2H, H-3, H-4), 3.63 (ddd, 1H, J1,5aa=4.2 Hz, J1,5ab=2.0 Hz, J1,2=3.0 Hz, H-1), 3.55 (dd,
1H, J2,3=9.0 Hz, H-2), 3.42 (s, 3H, OMe), 2.71 (dd, 1H, J5aa,5ab=14.2 Hz, H-5aa), 1.96 (dd, 1H, H-5ab);
δC (100 MHz, CDCl3) 140.7 (C-5), 139.0, 138.6 (3×s, C-arom. quat.), 128.3–127.4 (15×d, Ph), 110.9
(C-6), 83.3, 82.9 (C-3,C-4), 82.2 (C-2), 76.0 (C-1), 75.7, 73.6, 72.7 (3×t, CH2Ph), 56.7 (CH3); m/z 462
(M+NH4)+, 445 (M+H)+; found: C, 78.28; H, 7.28; C29H32O4 requires: C, 78.34; H, 7.25%.

292
M. Sollogoub et al. / Tetrahedron: Asymmetry 11 (2000) 283–294
4.11. Carba-5a methyl 2,3,4-tri-O-benzyl-β-L-idopyranoside 16
BH3·THF (0.45 mL, 0.45 mmol, 1.0 M in THF) was added to a solution of 15 (100 mg, 0.22
mmol) in anhydrous THF (1 mL) at room temp. under argon. After 1 h, TLC (cyclohexane:AcOEt,
3:1) indicated completion of the reaction. Ethanol (1.5 mL), NaOH (0.4 mL, 3 M) and aqueous hydrogen
peroxide (0.3 mL, 30%) were added and the mixture was stirred for 1 h at room temp., when TLC
(cyclohexane:AcOEt, 3:1) indicated complete oxidation. The reaction mixture was poured into ice-water
(10 mL) and stirred for 5 min. The aqueous layer was extracted with CH2Cl2 (3×15 mL) and the
combined extracts were dried (MgSO4), filtered and the solvent was removed in vacuo. The residue
was purified by flash chromatography (AcOEt:cyclohexane, 3:7) to afford carba-5a methyl 2,3,4-tri-O-
benzyl-β-L-idopyranoside 16 (62 mg, 60%), as a colourless oil: [α]20 +4 (c 0.6, CHCl3); δH (400 MHz,
D
CDCl3) 7.41–7.30 (m, 15H, H arom.), 4.83 (d, 1H, J=11.0 Hz, -CHPh), 4.77 (d, 1H, J=11.5 Hz, -CHPh),
4.76 (d, 1H, J=11.0 Hz, -CHPh), 4.74 (s, 2H, -CH2Ph), 4.61 (d, 1H, J=11.6 Hz, -CHPh), 4.06 (t, 1H,
J3,2=J3,4=7.5 Hz, H-3), 3.99 (ddd, 1H, J6a,6b=11.6 Hz, J=7.0 Hz, J=3.5 Hz, H-6a), 3.69 (ddd, 1H, J=8.3
Hz, J=4.1 Hz, H-6b), 3.66 (dd, 1H, J4,5=5.2 Hz, H-4), 3.58 (dt, 1H, J1,5aa=5.8 Hz, J1,5ab=J1,2=2.9 Hz,
H-1), 3.53 (dd, 1H, H-2), 3.44 (s, 3H, OMe), 2.30–2.23 (m, 1H, H-5), 2.07 (dt, 1H, J5aa,5ab=14.4 Hz,
J1,5aa=J5,5aa=5.8 Hz, H-5aa), 1.47 (ddd, 1H, J5,5ab=4.9 Hz, H-5ab); δC (100 MHz, CDCl3) 138.7, 138.6,
138.2 (3×s, C-arom. quat.), 128.4–127.6 (15×d, Ph), 77.3, 74.9, 73.0, 72.9, 64.5, 57.5, 38.9, 26.0; m/z
480 (M+NH4)+; found: C, 78.21; H, 7.51; C29H34O5 requires: C, 75.29; H, 7.41%.
4.12. Carba-5a methyl β-L-idopyranoside 2
10% Pd/C (10 mg) was added to a solution of 16 (126 mg, 27 mmol) in methanol (10 mL). After stirring
for 2 h at room temp. under hydrogen (1.5 atm), TLC (AcOEt:iPrOH:H2O, 3:3:1) indicated completion
of the reaction. The mixture was filtered (Celite®) and the solvent was removed in vacuo. The residue
was purified by flash chromatography (CH2Cl2:MeOH, 9:1) to afford carba-5a methyl β-L-idopyranoside
20
D
2 (39 mg, 75%), as a colourless oil: [α] +8.0 (c 2.0, MeOH); δH (400 MHz, CD3OD) 4.17–4.12 (m,
1H, H-2 H-3), 3.97 (dd, 1H, J3,4=5.1 Hz, J4,5=2.8 Hz, H-4), 3.92 (dd, 1H, J6a,6b=10.2 Hz, J6a,5=7.1 Hz,
H-6a), 3.73 (dd, 1H, J5,6b=6.6 Hz, H-6b), 3.76–3.71 (m, 1H, H-1), 3.57 (s, 3H, OMe), 2.26–2.18 (m, 1H,
H-5), 1.87–1.82 (m, 2H, H-5a); δC (100 MHz, CD3OD) 79.3 (C-1), 72.7 (C-4), 72.5 (C-2+C-3), 64.8
(C-6), 56.7 (OMe), 40.0 (C-5), 24.3 (C-5a); m/z 210 (M+NH4)+, 193 (M+H)+; found: C, 49.62; H, 8.68;
C8H16O5 requires: C, 49.99; H, 8.39%.
4.13. Methyl 2,3,6-tri-O-benzyl-4-O-(carba-5a 2,3,4-tri-O-benzyl-6-deoxy-α-D-xylo-hex-5-enopyran-
osyl)-α-D-glucopyranoside 19
Pyridine (31 µL) and then Tebbe reagent29 (0.19 mL, 0.19 mmol, 1.0 M in toluene) were added to a
stirred solution of methyl 2,3,6-tri-O-benzyl-4-O-[1D-(1,2,4/3)-2,3,4-tri-O-benzyl-1,2,3,4-tetrahydroxy-
cyclohex-5-onyl]-α-D-glucopyranoside 1721 (83 mg, 0.1 mmol) in anhydrous THF (3 mL) at −45°C
under argon. The reaction mixture was warmed to room temp. over 15 min and after a further 1 h,
TLC (cyclohexane:AcOEt, 4:1) indicated remaining starting material (Rf 0.2) and formation of product
(Rf 0.35). The reaction mixture was cooled to −15°C and aqueous sodium hydroxide (0.5 mL, 3 M)
was cautiously added dropwise. The mixture was warmed to room temp. and filtered through Celite®
washing with Et2O (10 mL) and water (10 mL). The aqueous layer was extracted with Et2O (3×15
mL) and AcOEt (15 mL) and then the combined extracts were dried (MgSO4), filtered and the solvent
was removed in vacuo. The residue was purified by flash chromatography (eluent gradient, 15–20%

M. Sollogoub et al. / Tetrahedron: Asymmetry 11 (2000) 283–294
293
AcOEt in cyclohexane) to afford methyl 2,3,6-tri-O-benzyl-4-O-(carba-5a 2,3,4-tri-O-benzyl-6-deoxy-
α-D-xylo-hex-5-enopyranosyl)-α-D-glucopyranoside 19 (46 mg, 56%; 77% based on recovered 17), as a
colourless oil: [α]20 +1.2 (c 1.0, CHCl3); δH (400 MHz, CDCl3) 7.38–7.25 (m, 30H, H arom.), 5.21 (br
D
s, 1H, H-60a), 5.04 (d, 1H, J=11.4 Hz, -CHPh), 4.97 (br s, 1H, H-60b), 4.79–4.62 (m, 10H, 9×-CHPh,
0
0
H-1), 4.60 (d, 1H, J=12.0 Hz, -CHPh), 4.56 (d, 1H, J=12.2 Hz, -CHPh), 4.46 (dt, 1H, J1 ,5 aa=5.8 Hz,
J1 ,2 =J1 ,5 ab=2.8 Hz, H-10), 4.00 (t, 1H, J2,3=J3,4=9.0 Hz, H-3), 3.85 (ddd, 1H, J4,5=9.8 Hz, J5,6b=5.0
Hz, J5,6a=2.0 Hz, H-5), 3.80–3.79 (m, 2H, H-30, H-40), 3.72 (dd, 1H, H-4), 3.70 (dd, 1H, H-6a), 3.65
(dd, 1H, J6a,6b=10.6 Hz, H-6b), 3.60 (dd, 1H, J1,2=3.5 Hz, H-2), 3.59–3.56 (br m, 1H, H-20), 3.44 (s,
0
0
0
0
3H, OMe), 2.83 (br dd, 1H, J5 aa,5 ab=14.3 Hz, H-50aa), 2.02 (br d, 1H, H-50ab); δC (100 MHz, CDCl3)
141.1 (C-50), 138.8, 138.7, 138.7, 138.6, 138.2, 138.0 (6×s, C-arom. quat.), 128.5–127.1 (30×d, Ph),
112.9 (C-60), 97.6 (C-1), 82.2 (C-3), 81.9, 81.3 (C-30, C-40), 80.8 (C-20), 80.4 (C-2), 74.6 (C-10), 74.5,
74.4, 73.3, 73.3, 72.8, 72.7 (6×t, CH2Ph), 72.6 (C-4), 69.8 (C-5), 69.7 (C-6), 55.1 (Me), 32.3 (C-50a);
0
0
+
m/z 894.5 (M+NH4 , 100%); found: C, 77.02; H, 7.27; C56H60O9 requires: C, 76.68; H, 6.90%. Further
elution afforded recovered 17 (23 mg).
4.14. Methyl 2,3,6-tri-O-benzyl-4-O-(carba-5a methyl 2,3,4-tri-O-benzyl-β-L-idopyranosyl)-α-D-
glucopyranoside 3
BH3·THF (0.11 mL, 0.11 mmol, 1.0 M in THF) was added to a solution of 19 (47 mg, 0.054 mmol)
in anhydrous THF (2 mL) at 0°C under argon and immediately warmed to room temp. After 1 h, TLC
(cyclohexane:AcOEt, 4:1) indicated loss of starting material (Rf 0.4) and formation of product (Rf 0.1).
Ethanol (0.4 mL) was added dropwise, followed by NaOH (0.1 mL, 3 M) and aqueous hydrogen peroxide
(0.07 mL, 30%) and the mixture was stirred for 2 h at room temp., when TLC (cyclohexane:AcOEt, 3:1)
indicated loss of starting material (Rf 0.25) and formation of a major product (Rf 0.3). Ice-water (10
mL) was added and the aqueous layer was extracted with CH2Cl2 (3×30 mL) and the combined extracts
were dried (MgSO4), filtered and the solvent was removed in vacuo. The residue was purified by flash
chromatography (eluent gradient, 25–30% AcOEt in cyclohexane) to afford methyl 2,3,6-tri-O-benzyl-
4-O-(carba-5a methyl 2,3,4-tri-O-benzyl-β-L-idopyranosyl)-α-D-glucopyranoside 3 (23 mg, 48%), as a
20
D
colourless oil: [α] +33.3 (c 0.9, CHCl3); δH (400 MHz, CDCl3) 7.37–7.21 (m, 30H, H arom.), 4.99
(d, 1H, J=10.9 Hz, -CHPh), 4.80–4.68 (m, 4H, 4×-CHPh), 4.67 (d, 1H, J1,2=3.7 Hz, H-1), 4.64–4.58 (m,
4H, 4×-CHPh), 4.28 (dt, 1H, J1 ,5 a(ax)=11.3 Hz, J1 ,2 =J1 ,5 a(eq)=3.5 Hz, H-10), 4.22 (d, 1H, J=11.7 Hz,
-CHPh), 4.21 (d, 1H, J=12.7 Hz, -CHPh), 4.06 (d, 1H, J=12.6 Hz, -CHPh), 3.93 (t, 1H, J2,3=J3,4=9.0
0
0
0
0
0
0
0
0
0
0
0
Hz, H-3), 3.87 (br t, 1H, J1 ,2 =J2 ,3 =3.5 Hz, H-2 ), 3.80 (dd, 1H, J6a,6b=10.3 Hz, J5,6a=3.0 Hz, H-6a),
3.77–3.71 (m, 4H, H-30, H-4, H-5, H-6b), 3.58 (dd, 1H, H-2), 3.53–3.50 (m, 3H, H-40, H-60a, H-60b),
3.46 (s, 3H, OMe), 1.97 (ddd, 1H, J5 ,5 a(ax)=J5 a(ax),5 a(eq) 12.0 Hz, H-50a(ax)), 1.90–1.83 (m, 1H, H-50),
0
0
0
0
1.73 (ddd, 1H, J5 ,5 a(eq)=3.5 Hz, H-50a(eq)); δC (100 MHz, CDCl3) 139.2, 138.6, 138.1, 138.0, 137.9,
137.9 (6×s, C-arom. quat.), 128.4–127.2 (30×d, Ph), 98.0 (C-1), 82.7 (C-3), 79.9 (C-2), 78.1 (C-10),
76.9 (C-20), 76.0 (C-40), 75.4 (t, CH2Ph), 74.1 (C-4), 73.4 (t, CH2Ph), 73.3 (C-30), 73.25, 73.2, 71.7,
71.1 (4×t, CH2Ph), 70.0 (C-5), 68.7 (C-6), 64.9 (C-60), 55.3 (Me), 37.8 (C-50), 23.1 (C-50a); m/z 912.4
0
0
+
(M+NH4 , 100%), 482.4 (22%); found: C, 75.00; H, 7.34; C56H62O10 requires: C, 75.14; H, 6.98%.
Acknowledgements
We wish to thank the European Community for a TMR Marie Curie Research Training Grant (No.
ERBFMBICT983225) to A.J.P.

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