Methyl 3,5-di-O-benzyl-2-O-methylsulfonyl-6-O-triphenyl-
methyl-3-C-vinyl-ꢁ-D-allofuranoside 13
2.14 (1H, t, J 7.7 Hz, 8-OH); δC (75 MHz; CDCl3; Me4Si) 144.0
(Ph), 138.0, 137.2 (Bn), 129.0, 128.8, 128.7, 128.4, 128.1, 127.8,
127.7, 127.6, 127.3, 127.1 (Bn, Ph), 104.1 (C-1), 86.7 (Ph3C),
85.7 (C-3), 84.6 (C-2), 82.9 (C-7), 77.1 (C-5), 74.6 (C-4), 71.6
(Bn), 68.0 (Bn), 62.4 (C-6, C-8), 57.5 (OCH3); m/z (FAB) 681
(M ϩ Na).
(556 mg, 31%); δH (300 MHz; CDCl3; Me4Si) 7.48–7.44 (6H, m,
Ph), 7.33–7.20 (19H, m, Bn, Ph), 5.91 (1H, dd, J 17.6, 11.2 Hz,
H-7), 5.34 (1H, d, J 17.6 Hz, H-8), 5.28 (1H, d, J 11.2 Hz, H-8),
5.03 (1H, d, J 4.8 Hz, H-1), 4.99 (1H, d, J 4.8 Hz, H-2), 4.73
(1H, d, J 12.0 Hz, Bn), 4.68 (1H, d, J 11.5 Hz, Bn), 4.62 (1H, d,
J 12.0 Hz, Bn), 4.57 (1H, d, J 7.3 Hz, H-4), 4.42 (1H, d, J 11.5
Hz, Bn), 3.62 (1H, m, H-5), 3.45 (1H, m, H-6), 3.43 (3H, s,
OCH3), 3.31 (1H, dd, J 10.2, 5.1 Hz, H-6), 2.99 (3H, s,
SO2CH3); δC (75 MHz; CDCl3; Me4Si) 144.1 (Ph), 139.1, 138.3
(Bn), 135.7 (C-7), 128.9, 128.8, 128.3, 128.2, 127.8, 127.7, 127.5,
127.3, 127.2, 127.0 (Bn, Ph), 117.8 (C-8), 100.6 (C-1), 86.7
(Ph3C), 83.1, 81.2, 79.5 (C-2, C-3, C-4), 77.9 (C-5), 71.9 (Bn),
67.2 (Bn), 62.8 (C-6), 55.7 (OCH3), 39.0 (SO2CH3); m/z (FAB)
743 (M ϩ Na).
Preparation of (1R,2R,4R,5S,7R)-1-benzyloxy-2-(1(R)-benzyl-
oxy-2-triphenylmethoxy)ethyl-4-methoxy-7-methylsulfonyloxy-
methyl-3,6-dioxabicyclo[3.2.0]heptane 16
To a stirred solution of 15 (131 mg, 0.199 mmol) in anhydrous
pyridine (1.0 cm3) at 0 ЊC was added dropwise methane
sulfonylchloride (0.04 cm3, 0.5 mmol). The reaction mixture
was stirred at room temperature for 1 h, quenched with ice-cold
water (15 cm3) and extracted with dichloromethane (3 × 15 cm3).
The combined extracts were washed with a saturated aqueous
solution of NaHCO3 (20 cm3) and then dried (MgSO4). The
solvent was removed by distillation under reduced pressure
and the residue purified by chromatography over silica with
dichloromethane–methanol (99 : 1) as eluent to give the
product as an oil (124 mg, 85%); δH (300 MHz; CDCl3; Me4Si)
7.50–7.47 (6H, m, Ph), 7.34–7.23 (19H, m, Bn), 4.97 (1H, dd,
J 6.9, 4.0 Hz, H-7), 4.92 (1H, d, J 2.8 Hz, H-2), 4.75 (1H, d,
J 2.8 Hz, H-1), 4.71 (1H, d, J 11.3 Hz, Bn), 4.59 (1H, d, J 11.3
Hz, Bn), 4.56 (1H, m, H-8), 4.53 (1H, d, J 11.6 Hz, Bn), 4.42
(1H, d, J 11.6 Hz, Bn), 4.41 (1H, d, J 7.2 Hz, H-4), 4.37 (1H, dd,
J 11.6, 4.0 Hz, H-8), 3.96 (1H, m, H-5), 3.60 (1H, dd, J 10.4, 2.5
Hz, H-6), 3.48 (3H, s, OCH3), 3.40 (1H, dd, J 10.4, 4.2 Hz,
H-6), 2.80 (3H, s, SO2CH3); δC (75 MHz; CDCl3; Me4Si) 143.9
(Ph), 137.9, 137.0 (Bn), 128.9, 128.8, 128.6, 128.5, 128.1, 127.9,
127.8, 127.6, 127.2, 127.2 (Bn, Ph), 103.9 (C-1), 86.8 (Ph3C),
85.1 (C-3), 84.8 (C-2), 81.0 (C-7), 77.1 (C-5), 74.4 (C-4), 71.7
(Bn), 69.3 (C-8), 67.9 (Bn), 62.3 (C-6), 57.6 (OCH3), 37.3
(SO2CH3); m/z (FAB) 759 (M ϩ Na).
Preparation of methyl 3,5-di-O-benzyl-3-C-(1(R),2-dihydroxy-
ethyl)-2-O-methylsulfonyl-6-O-triphenylmethyl-ꢀ-D-allofurano-
side 14
To a solution of 12 (596 mg, 0.827 mmol) in tert-butanol
(9.2 cm3) was added water (0.50 cm3) pyridine (0.46 cm3),
N-methylmorpholine-N-oxide (673 mg, 5.80 mmol) and a 2.5
w/w-% solution of osmium tetroxide in tert-butanol (0.046
cm3). The solution was stirred under reflux at 76 ЊC for 12 h and
quenched at room temperature with a 20% aqueous solution of
Na2S2O5 (3.4 cm3). The mixture was diluted with water (30 cm3)
and extracted with dichloromethane (2 × 100 cm3). The com-
bined extracts were washed with a saturated aqueous solution
of NaHCO3 (75 cm3) and then dried (MgSO4). The solvent was
removed by distillation under reduced pressure and the residue
purified by chromatography over silica with dichloromethane–
methanol (99 : 1) as eluent to give the product as a clear oil (482
mg, 77%) which was used without further purification in the
next step; δH (300 MHz; CDCl3; Me4Si) (major isomer) 7.52–
7.42 (6H, m, Ph), 7.33–7.21 (19H, m, Bn, Ph), 5.27 (1H, d, J 3.3
Hz, H-2), 5.08 (1H, d, J 3.3 Hz, H-1), 4.73–4.64 (4H, m, Bn,
H-4), 4.31 (1H, d, J 10.5 Hz, Bn), 4.05 (1H, m, H-7), 3.97 (1H,
m, H-5), 3.78 (1H, dd, J 11.8, 5.4 Hz, H-8), 3.62–3.57 (2H, m,
H-6, H-8), 3.37 (1H, dd, J 10.4, 3.8 Hz, H-6), 3.20 (3H, s,
OCH3), 3.03 (3H, s, SO2CH3); δC (75 MHz; CDCl3; Me4Si)
(major isomer) 143.91 (Ph), 138.0, 137.5 (Bn), 128.9, 128.7,
128.6, 128.6, 128.4, 128.1, 128.0, 127.9, 127.6, 127.2, 127.1 (Bn,
Ph), 107.4 (C-1), 87.0, 86.6 (Ph3C, C-3), 83.9, 81.5 (C-2, C-4),
77.5 (C-5), 71.5, 71.4 (Bn, C-7), 67.7 (Bn), 63.2, 61.2 (C-6, C-8),
56.4 (OCH3), 38.4 (SO2CH3); m/z (PDMS) 777 (M ϩ Na).
Preparation of (1R,2R,4R,5S,7R)-1-benzyloxy-2-(1(R)-benzy-
loxy-2-hydroxy)ethyl-7-hydroxymethyl-4-methoxy-3,6-dioxa-
bicyclo[3.2.0]heptane 17
A solution of 15 (90 mg, 0.137 mmol) in anhydrous diethyl
ether (0.37 cm3) was stirred at 0 ЊC, formic acid (0.30 cm3) was
added, and the mixture was stirred at 0 ЊC for 1 h. The reaction
mixture was quenched with water (5 cm3) and neutralised
with NaHCO3. The mixture was extracted with diethyl ether
(2 × 10 cm3) and the combined extracts were dried (MgSO4).
The solvent was removed by distillation under reduced pressure
and the residue was purified by chromatography over silica with
dichloromethane–methanol (97 : 3) as eluent to give the
product as a clear oil (19 mg, 33%); δH (300 MHz; CDCl3;
Me4Si) 7.35–7.26 (10H, m, Bn), 4.95 (1H, d, J 2.8 Hz, H-2), 4.82
(1H, d, J 2.8 Hz, H-1), 4.79 (1H, m, H-7), 4.68 (1H, d, J 11.2
Hz, Bn), 4.64 (1H, d, J 11.2 Hz, Bn), 4.57 (1H, d, J 11.4 Hz,
Bn), 4.52 (1H, d, J 11.4 Hz, Bn), 4.30 (1H, d, J 8.5 Hz, H-4),
4.03 (1H, m, H-6), 3.86–3.39 (4H, m, H-5, H-6, H-8), 3.58 (3H,
s, OCH3); δC (75 MHz; CDCl3; Me4Si) 137.6, 136.9 (Bn), 128.7,
128.6, 128.6, 128.3, 128.1, 128.0, 128.0, 127.9, 127.7, 127.7 (Bn),
104.3 (C-1), 85.6 (C-3), 83.9 (C-2), 83.0 (C-7), 77.6 (C-5), 74.2
(C-4), 71.9 (Bn), 68.4 (Bn), 62.3 (C-8), 61.0 (C-6), 57.8 (OCH3);
m/z (FAB) 439 (M ϩ Na).
Preparation of (1R,2R,4R,5S,7R)-1-benzyloxy-2-(1(R)-benzy-
loxy-2-triphenylmethoxy)ethyl-7-hydroxymethyl-4-methoxy-3,6-
dioxabicyclo[3.2.0]heptane 15
A solution of 14 (458 mg, 0.608 mmol) in anhydrous DMF
(1.0 cm3) was stirred at 0 ЊC and a 60% oily dispersion of NaH
(38 mg, 0.91 mmol) was added. The reaction mixture was
stirred at room temperature for 2 days, and then quenched with
a saturated aqueous solution of NaHCO3 (20 cm3) and
extracted with dichloromethane (2 × 50 cm3). The combined
extracts were dried (MgSO4) and the solvent was removed by
distillation under reduced pressure. The residue was purified by
chromatography over silica with dichloromethane–methanol
(99 : 1) as eluent to give the product as a clear oil (325 mg, 80%)
(Found: C, 75.20; H, 6.46. C42H42O7, 0.5H2O requires C, 75.54;
H, 6.49%); δH (300 MHz; CDCl3; Me4Si) 7.55–7.48 (6H, m, Ph),
7.35–7.23 (19H, m, Bn), 4.92 (1H, d, J 2.8 Hz, H-2), 4.76 (1H,
d, J 2.8 Hz, H-1), 4.74 (1H, m, H-7), 4.71 (1H, d, J 11.1 Hz,
Bn), 4.63 (1H, d, J 11.1 Hz, Bn), 4.54 (1H, d, J 11.4 Hz, Bn),
4.44 (1H, d, J 8.8 Hz, H-4), 4.40 (1H, d, J 11.4 Hz, Bn), 3.99
(1H, m, H-5), 3.79–3.84 (2H, m, H-8), 3.63 (1H, dd, J 10.4, 2.4
Hz, H-6), 3.47 (3H, s, OCH3), 3.41(1H, dd, J 10.4, 4.2 Hz, H-6),
Preparation of 1,2-O-isopropylidene-3,5,6-tri-O-benzyl-3-C-
vinyl-ꢁ-D-allofuranose 18
A 60% oily dispersion of NaH (869 mg, 21.73 mmol) was
suspended in anhydrous DMF (6 cm3) and the suspension was
stirred at 0 ЊC. A solution of 5 (1.015 g, 4.12 mmol) in
anhydrous DMF (7 cm3) was added dropwise over 30 min. The
mixture was stirred at 50 ЊC for 1 h and then cooled to 0 ЊC.
Benzyl bromide (2.45 cm3, 20.63 mmol) was added dropwise
and the reaction mixture was stirred at room temperature for
20 h. The solvent was removed by distillation under reduced
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 7 3 8 – 3 7 4 8
3743