Benzyl 2,3,4,6-tetra-O-acetyl-ꢀ-D-glucopyranosyl-(1 4)-2,3,6-
tri-O-benzoyl-ꢀ-D-mannopyranosyl-(1 4)-2,3,6-tri-O-benzoyl-
ꢀ-D-mannopyranoside 14
74.24 and 74.28 (C-5 and -5Ј), 74.65 (C-4), 75.06 (C-4Ј), 80.16
(C-4Љ), 96.94 (C-1) 98.91 (C-1Ј), 101.90 (CHPh), 104.33 (C-1Љ),
128.56–136.81 (Ph) and 165.16–167.04 (C=0); ES-MS(ϩ)
data: m/z 1329.96 (100%, [M ϩ Na]ϩ) (expected m/z, 1329.40;
C74H66O22 requires M, 1306.40).
A mixture of 2,3,4,6-tetra-O-acetyl-α--glucopyranosyl tri-
chloroacetimidate 1327,28 (0.235 g, 0.477 mmol), the disacchar-
ide derivative 12 (0.360 g, 0.341 mmol) and freshly activated
molecular sieves 4 Å (powder, 1 g) in dry dichloromethane
(5 cm3) was stirred under argon for 30 min. TMS triflate
(0.02 cm3, 0.113 mmol) was then added and stirring was con-
tinued for a further 2 h. The reaction was quenched by addition
of N,N-diisopropylethylamine (3 drops), the solids were filtered
off using a Celite pad, and the solvent was removed under
Benzyl 3-O-benzoyl-4,6-O-benzylidene-ꢀ-D-glucopyranosyl-
(1 4)-2,3,6-tri-O-benzoyl-ꢀ-D-mannopyranosyl-(1 4)-2,3,6-
tri-O-benzoyl-ꢀ-D-mannopyranoside 17
A solution of benzoyl cyanide (0.011 g, 0.0849 mmol) in di-
chloromethane (0.3 cm3) was added to a cooled (Ϫ45 ЊC) and
stirred solution of the 2Љ,3Љ-diol 16 (0.111 g, 0.0849 mmol) in
acetonitrile (3 cm3) and dichloromethane (0.5 cm3) containing
Et3N (0.018 cm3, 0.127 mmol). The temperature was allowed to
rise slowly to Ϫ10 ЊC. After 1 h 10 min, when TLC (solvents A
and C) indicated the reaction was complete, the solution was
diluted with methanol (3 cm3) and cooling was discontinued.
After another 20 min, the mixture was concentrated and a fur-
ther portion of methanol (3 cm3) was evaporated off from the
reduced pressure. FCC [toluene–ethyl acetate, (9 : 1)
(8 : 2)]
of the residue produced the trisaccharide derivative 14 (0.224 g,
47%) as an amorphous solid; [α]D23 Ϫ108 (c 1, CHCl3); (Found:
C, 64.44; H, 5.02. C75H70O26 requires C, 64.93; H, 5.09%);
δH 1.69 and 1.70 (6 H, 2 × s, 2 × Ac), 1.88 (6 H, s, 2 × Ac), 3.13
(1 H, br d, 5Ј-H), 3.40–3.50 (2 H, m, 5Љ-H and 6Љ-Ha), 3.71 (1 H,
dd, J5Љ,6bЉ 4.2, J6aЉ,6bЉ 12.0, 6Љ-Hb), 3.79 (1 H, br dd, 5-H), 4.04–
4.18 (2 H, m, 6Ј-H2), 4.25 (1 H, t, J3Ј,4Ј = J4Ј,5Ј = 9.2, 4Ј-H), 4.46
(1 H, t, J3,4 = J4,5 = 9.4, 4-H), 4.49 (1 H, d, J1Љ,2Љ 7.8, 1Љ-H), 4.62
and 4.83 (2 H, AB q, J 12.2, CH2Ph), 4.65 (1 H, dd, J5,6a 3.5,
J6a,6b 11.9, 6-Ha), 4.72 (1 H, br s, 1-H), 4.73–4.87 (3 H, m, 2Љ-,
3Љ-H and 6-Hb), 4.93 (1 H, t, J3Љ,4Љ = J4Љ,5Љ = 9.3, 4Љ-H), 5.00 (1 H,
br s, 1Ј-H), 5.43 (1 H, dd, 3Ј-H), 5.53 (1 H, dd, 3-H), 5.75 (1 H,
br d, J2,3 2.7, 2-H), 5.85 (1 H, br d, J2Ј,3Ј 2.5, 2Ј-H) and 7.15–8.23
(35 H, m, 7 × Ph). Also isolated were the recovered disaccharide
12 (0.065 g, 18%) and the 4Ј-trimethylsilyl ether 15 (0.105 g,
27%), δH 0.01 (9 H, s, Me3Si), 3.55 (1 H, br dd, 5Ј-H), 3.97 (1 H,
br dd, J5,6a 3.7, 5-H), 4.18 (1 H, br d, J6aЈ,6bЈ 11.3, 6Ј-Ha), 4.39
(1 H, J5Ј,6bЈ 2.4, 6Ј-Hb), 4.49 (1 H, t, J3Ј,4Ј = J4Ј,5Ј = 9.4, 4Ј-H), 4.65
(1 H, t, J3,4 = J4Ј,5Ј = 9.3, 4-H), 4.78 and 5.00 (2 H, AB q, J 12.2,
CH2Ph), 4.83 (1 H, dd, J6a,6b 13.3, 6-Ha), 4.89 (1 H, br s, 1-H),
4.97 (1 H, m, 6-Hb), 5.16 (1 H, br s, 1Ј-H), 5.42 (1 H, dd, 3Ј-H),
5.68 (1 H, dd, 3-H), 5.92 (1 H, br d, J2,3 2.8, 2-H), 5.98 (1 H, br
d, J2Ј,3Ј 2.4, 2Ј-H) and 7.30–8.40 (35 H, m, 7 × Ph).
residue. FCC [toluene–ethyl acetate, (95 : 5)
(9 : 1)] of the
residue produced the trisaccharide heptabenzoate 17 (0.078 g,
65%) as an amorphous solid; [α]D23 Ϫ102 (c 1, CHCl3); δH 2.88
(1 H, d, J2Љ,OH 4.2, 2Љ-OH), 2.93 (1 H, t, J5Љ,6aЉ = J6aЉ,6bЉ = 9.9, 6Љ-
Ha), 3.17 (1 H, dd, J5Љ,6bЉ 3.3, 6Љ-Hb), 3.36–3.54 (4 H, m, 2Љ-,
4Љ-, 5Ј- and 5Љ-H), 3.71 (1 H, ddd, J5,6a 3.7, 5-H), 3.97 (1 H, t,
J3Ј,4Ј = J4Ј,5Ј = 9.5, 4Ј-H), 4.12 (1 H, br d, J6aЈ,6bЈ 11.3, 6Ј-Ha), 4.29
(1 H, dd, J5Ј,6bЈ 3.5, 6Ј-Hb), 4.33 (1 H, d, J1Љ,2Љ 7.2, 1Љ-H), 4.39
(1 H, t, J3,4 = J4,5 = 9.4, 4-H), 4.54–4.75 (2 H, AB q, J 12.4,
CH2Ph), 4.58 (1 H, dd, J6a,6b 12.2, 6-Ha), 4.64 (1 H, br s, 1-H),
4.73 (1 H, dd, J5,6b 1.9, 6-Hb), 4.89 (1 H, br s, 1Ј-H), 5.12 (1 H, s,
CHPh), 5.13 (1 H, t, J2Љ,3Љ = J3Љ,4Љ = 9.3, 3Љ-H), 5.37 (1 H, dd,
3Ј-H), 5.43 (1 H, dd, 3-H), 5.67 (1 H, br d, J2,3 3.3, 2-H), 5.71
(1 H, br d, J2Ј,3Ј 3.2, 2Ј-H) and 7.05–8.10 (45 H, m, 9 × Ph);
ES-MS(ϩ) data: m/z 1434.02 (100%, [M ϩ Na]ϩ) (expected m/z,
1433.43; C81H70O23 requires M, 1410.43);
Benzyl 2,3-di-O-benzoyl-4,6-O-benzylidene-ꢀ-D-mannopyrano-
syl-(1 4)-2,3,6-tri-O-benzoyl-ꢀ-D-mannopyranosyl-(1 4)-
2,3,6-tri-O-benzoyl-ꢀ-D-mannopyranoside 19
Benzyl 4,6-O-benzylidene-ꢀ-D-glucopyranosyl-(1 4)-2,3,6-tri-
O-benzoyl-ꢀ-D-mannopyranosyl-(1 4)-2,3,6-tri-O-benzoyl-ꢀ-D-
mannopyranoside 16
Triflic anhydride (0.036 cm3, 0.215 mmol) was added dropwise
to a cooled (0 ЊC) stirred solution of compound 17 (0.076 g,
0.054 mmol) in dichloromethane (5 cm3) containing pyridine
(0.044 cm3, 0.538 mmol). The reaction was monitored by TLC
(solvent A and B). After 1 h 15 min, a second portion of triflic
anhydride (0.009 cm3, 0.054 mmol) was added. After a further
20 min, the mixture was diluted with dichloromethane, washed
successively with ice-cold 0.1 mol dmϪ3 HCl, ice-cold saturated
aq. NaHCO3 and water, and dried by filtration through cotton
wool. The filtrate was concentrated and toluene was evaporated
off from the residue (the expected triflate 18). A solution of
tetrabutylammonium benzoate (0.059 g, 0.161 mmol; dried
beforehand by evaporation of anhydrous toluene) in toluene
(5 cm3) was added to the residue and the reaction mixture was
stirred under reflux. After 50 min, when TLC (solvent A) indi-
cated the completion, the mixture was diluted with dichloro-
methane, washed successively with saturated aq. NaHCO3 and
water, dried by filtration through cotton wool and concen-
A solution of HCl in methanol [prepared at 0 ЊC from acetyl
chloride (0.4 cm3) and methanol (10 cm3)] was added to a solu-
tion of compound 14 (0.21 g, 0.151 mmol) in dichloromethane
(3 cm3). The resulting solution was kept at room temperature
for 45 h [TLC (solvent D) then showed the formation of one
major product], concentrated, and toluene (3 × 7 cm3) was
evaporated off from the residue. The residue was dissolved in
acetonitrile (5 cm3), α,α-dimethoxytoluene (0.045 cm3, 0.302
mmol) and TsOHؒH2O (20 mg, 0.105 mmol) were added, and
the mixture was stirred at rt with monitoring the reaction pro-
gress by TLC (solvents C and D). After 3 h, a second portion of
α,α-dimethoxytoluene (0.023 cm3, 0.151 mmol) was added.
After a further 2 h, the reaction was quenched by addition of
Et3N (0.5 cm3) and the mixture was concentrated. FCC (solvent
C) of the residue gave the derivative 16 (0.12 g, 61% from com-
23
pound 14) as an amorphous solid; [α]D Ϫ102 (c 1, CHCl3);
δH 2.70 (2 H, m, 2 × OH), 2.90 (1 H, t, J5Љ,6aЉ = J6aЉ,6bЉ = 10.2, 6Љ-
Ha), 3.10–3.28 (3 H, m, 4Љ-, 5Ј- and 5Љ-H), 3.35–3.48 (3 H, m, 2Љ-,
3Љ-H and 6Љ-Hb), 3.70 (1 H, br dd, J5,6a 4.0, 5-H), 3.96 (1 H, t,
J3Ј,4Ј = J4Ј,5Ј = 9.5, 4Ј-H), 4.06 (1 H, br d, J6aЈ,6bЈ 11.7, 6Ј-Ha), 4.18
(1 H, d, J1Љ,2Љ 7.5, 1Љ-H), 4.36 (1 H, dd, J5Ј,6bЈ 3.4, 6Ј-Hb), 4.38
(1 H, t, J3,4 = J4,5 = 9.2, 4-H), 4.54 and 4.75 (2 H, AB q, J 12.3,
CH2Ph), 4.60 (1 H, dd, J6a,6b 12.3, H-6a), 4.64 (1 H, br s, 1-H),
4.70 (1 H, br d, H-6b), 4.90 (1 H, br s, 1Ј-H), 5.13 (1 H, s,
CHPh), 5.36 (1 H, dd, 3Ј-H), 5.43 (1 H, dd, 3-H), 5.67 (1 H, br
d, J2,3 2.8, 2-H), 5.72 (1 H, br d, J2Ј,3Ј 2.8, 2Ј-H) and 7.05–8.12
(40 H, m, 8 × Ph); δC 62.90 and 63.22 (C-6 and -6Ј), 66.45
(C-5Љ), 68.16 (C-6Љ), 70.42 (2 C, C-2 and CH2Ph), 70.63 (C-2Ј),
72.10 and 72.35 (C-3 and -3Ј), 73.51 (C-3Љ), 73.73 (C-2Љ),
trated. FCC (toluene
toluene–ethyl acetate, 95 : 5) of the
residue gave the mannotrioside derivative 19 (0.073 g, 88% from
23
the heptabenzoate 17) as an amorphous solid; [α]D Ϫ132
(c 1, CHCl3); (Found: C, 69.94; H, 5.17. C88H74O24 requires C,
69.74; H, 4.92%); δH 3.01 (1 H, dt, J5Љ,6bЉ 4.5, 5Љ-H), 3.14 (1 H, t,
J5Љ,6aЉ = J6aЉ,6bЉ = 9.9, 6Љ-Ha), 3.20 (1 H, br dd, J5Ј,6bЈ 2.6, 5Ј-H),
3.35 (1 H, dd, 6Љ-Hb), 3.68 (1 H, ddd, J5,6a 3.6, 5-H), 3.78 (1 H,
br d, J6aЈ,6bЈ 10.9, 6Ј-Ha), 3.85 (1 H, t, J3Љ,4Љ = J4Љ,5Љ = 9.9, 4Љ-H),
4.16 (1 H, t, J3Ј,4Ј = J4Ј,5Ј = 9.6, 4Ј-H), 4.26 (1 H, dd, 6Ј-Hb), 4.33
(1 H, t, J3,4 = J4,5 = 9.5, 4-H), 4.52 and 4.73 (2 H, AB q, J 12.3,
CH2Ph), 4.57 (1 H, dd, J6a,6b 12.0, 6-Ha), 4.63 (1 H, br s, 1Ј-H),
4.67 (1 H, br s, 1-H), 4.68 (1 H, dd, J5,6b 1.9, 6-Hb), 4.82 (1 H, br
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 6 2 3 – 6 2 8
627