482
L. Marmuse et al. / Tetrahedron: Asymmetry 16 (2005) 477–485
Chromatography of the resulting residue (CH2Cl2–
MeOH, 12:1) gave the title compound (1.39 g, 85%);
½aꢂ = +30.7 (c 1.1, CHCl3); dH (CDCl3): 0.02 (6H, s,
chromatography (CH2Cl2–ethyl acetate, 1:0–95:5) gave
the title compound (936 mg, 70%) as white foam;
½aꢂ = +77 (c 1.0, CHCl3); dH (CDCl3): 3.73 (3H, s,
25
D
25
D
OMe), 3.80–3.88 (3H, m, H-4b, H-5a/b, H-6), 4.04–
SiMe2), 0.87 (9H, s, t-Bu), 3.29–4.18 (12H, m, H-2 to
H-6), 3.70 (3H, s, OMe), 4.65 (1H, d, J1,2 7.7 Hz, H-
1a), 4.99 (1H, d, J1,2 3.5 Hz, H-1b), 5.42 (1H, s, CH–
Ph), 6.70 (2H, d, JAB 9.1 Hz, C6H4–OMe), 6.98 (2H,
d, JAB 9.1 Hz, C6H4–OMe), 7.25–7.48 (5H, m, Ar); dC
(CDCl3): ꢀ5.4, ꢀ5.3 (Me2CSiCMe3) 18.2 (Me2CSiCMe3),
25.8 (Me2CSit-Bu), 55.4 (OMe), 62.5, 63.6 (C-6a, C-6b),
68.7, 70.8, 73.2, 73.4, 75.5, 76.1, 80.52, 80.7 (C-2a,b
to C-5a,b), 101.6 (C-1a), 101.8 (CH–Ph), 102.1 (C-1b),
114.3–137.8 (Ar), 151.2, 155.2 (Ar quat. from C6H4–
OMe); m/z (CI) 668.4 (45% [M+NH3]), 544.3 (100,
[Mꢀ124.1]), (ES) (Found: [M+NH4]+, 668.3101.
C32H50O12SiN requires 668.3097).
4.14 (3H, m, H-5a/b, 2 · H-6), 4.46 (1H, dd, J5,6
0
4.7 Hz, J6,6 10.1 Hz, H-6), 4.53 (1H, t, J3,4 ꢁ J4,5
9.3 Hz, H-4a), 5.19–5.23 (2H, m, H-1a, H-2b), 5.49
(1H, dd, J1,2 7.8 Hz, J2,3 9.5 Hz, H-2a), 5.53 (1H, s,
CH–Ph), 5.67 (1H, d, J1,2 4.2 Hz, H-1b), 5.75 (1H, t,
J2,3, J3,4 9.5 Hz, H-3a), 5.92 (1H, t, J2,3 ꢁ J3,4 9.5 Hz,
H-3b), 6.77 (2H, d, JAB 9.1 Hz, C6H4–OMe), 6.89 (2H,
d, JAB 9.1 Hz, C6H4–OMe), 7.25–7.86 (25H, m, Ar);
dC (CDCl3): 55.5 (OMe), 61.5, 63.8 (C-6a, C-6b), 68.5,
69.4, 71.2 (2), 72.2, 74.9, 75.0, 78.9 (C-2a,b to C-5a,b),
97.1 (C-1b), 100.2 (C-1a), 101.4 (CH–Ph), 114.6–136.8
(Ar), 151.0, 155.7 (Ar quat. from C6H4–OMe), 165.0,
165.3, 165.6, 165.7 (C@O); m/z (ES) 975.4 (100%,
[M+Na+]), (ES) (Found: [M+NH4]+, 970.3286
C54H52O16N requires 970.3281).
4.5. p-Methoxyphenyl 2,3-di-O-benzoyl-6-O-tert-butyl-
dimethylsilyl-4-O-(2,3-di-O-benzoyl-4,6-O-benzylidene-
a-D-glucopyranosyl)-b-D-glucopyranoside, 5
4.7. Methyl (2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl)-
(1!4)-(2,3,6-tri-O-acetyl-a-D-glucopyranosyl)-(1!4)-1-
thio-2,3,6-tri-O-acetyl-a,b-D-glucopyranoside 8
Silylated benzylidene maltoside 4 (1.40 g, 2.15 mmol)
was dissolved in dry pyridine (20 mL), cooled on an
ice bath and benzoyl chloride (2 mL, 17.2 mmol) was
added. After 2 days the mixture was diluted with
DCM (200 mL), washed successively with 1 M HCl
(3 · 60 mL) and saturated NaHCO3 solution
(3 · 60 mL) and dried over MgSO4. Concentration in
vacuo gave a residue which was subjected to column
chromatography (toluene–ethyl acetate, 10:1) and crys-
tallised from ethanol to give small crystals of the title
Maltotriose undecaacetate 7 was prepared according to
the procedure described by Wolfrom and Thompson.17
Acetic anhydride (20 mL) and NaOAc (2 g) were heated
to reflux and maltotriose (2.05 g, 4.06 mmol) was care-
fully added and the mixture was refluxed for a further
hour. The reaction mixture was cooled and the solvent
was co-evaporated with toluene. The resulting residue
was dissolved in CH2Cl2 (150 mL) and successively
washed with H2O (3 · 50 mL), saturated NaHCO3 solu-
tion (3 · 50 mL) and H2O (3 · 50 mL) and dried over
MgSO4. This material was used directly in the next step
without characterisation. The title compound was pre-
pared according to the procedure described by Kartha
and Field.18 Crude maltotriose undecaacetate 7 (3.71 g,
3.83 mmol) was dissolved in dry CH2Cl2 (40 mL), di-
methyldisulfide (190 lL, 2.10 mmol) and hexamethyldi-
silane (430 lL, 2.10 mmol) were added, followed by I2
(970 mg, 3.83 mmol). The mixture was stirred at room
temperature for 5 h, diluted with CH2Cl2 (200 mL),
washed with NaS2O3 solution (3 · 70 mL) and H2O
(2 · 80 mL) and dried over MgSO4. Concentration in va-
cuo and column chromatography (toluene–ethyl acetate,
9:1–1:1) gave the title compound as a white foam (3.50 g,
86%); a:b ca. 1:1.5; dH (CDCl3): 4.26 (d, J1,2 10.9 Hz, H-
1ab), 5.28 (d, J1,2 3.9 Hz, H-1b or H-1c), 5.41 (d, J1,2
4.1 Hz, H-1b or H-1c), 5.43 (d, J1,2 5.5 Hz, H-1aa); dC
(CDCl3): 11.3, 12.3 (SMe, a/b), 82.5 (2, C-1aa, C-1ab),
95.6, 95.8 (C-1b, C-1c).
compound (1.72 g, 75%); mp 176–178 ꢁC (ethanol);
25
½aꢂ = +60.1 (c 1.0, CHCl3); dH (CDCl3): 0.12 (3H, s,
D
SiMe2), 0.16 (3H, s, SiMe2), 0.96 (9H, s, t-Bu), 3.73–
3.87 (6H, m, OMe, H-4b, H-5b, H-6a), 4.11–4.15 (3H,
m, H-5a, H-6b, H-60b ), 4.39–4.45 (2H, m, H-4a, H-
60a), 5.15 (1H, d, J1,2 7.7 Hz, H-1a), 5.19 (1H, dd, J1,2
3.9 Hz, J2,3 9.9 Hz, H-2b), 5.46 (1H, dd, J1,2J2,3
9.4 Hz, H-2a), 5.52 (1H, s, CH-Ph), 5.64 (1H, d, J1,2
H-1b), 5.72 (1H, t, J2,3, J3,4 9.4 Hz H-3a), 5.92 (1H, t,
J2,3, J3,4 9.9 Hz, H-3b), 6.75 (2H, d, JAB 8.9 Hz,
C6H4–OMe), 6.92 (2H, d, JAB 8.9 Hz, C6H4–OMe),
7.24–7.85 (25H, m, Ar); dC (CDCl3): ꢀ5.05, ꢀ5.0
(Me2CSit-Bu), 18.5 (Me2CSit-Bu), 26.0 (Me2CSit-Bu),
55.5 (OMe), 62.2, 63.8 (C-6a, C-6b), 68.6, 69.3, 71.4,
71.5, 72.1, 75.1, 75.5, 79.2 (C-2a,b to C-5a,b), 96.7 (C-
1b), 100.3 (C-1a), 101.6 (CH–Ph), 114.4–136.8 (Ar),
151.2, 155.2 (Ar quat. from C6H4–OMe), 164.9, 165.2,
165.4, 165.5 (C@O); m/z (ES) 1089.6 [M+Na]+.
4.6. p-Methoxyphenyl 2,3-di-O-benzoyl-4-O-(2,3-di-O-
benzoyl-4,6-O-benzylidene-a-D-glucopyranosyl)-b-D-
glucopyranoside, 6
4.8. Methyl a-D-glucopyranosyl-(1!4)-glucopyranosyl-
(1!4)-1-thio-a,b-D-glucopyranoside, 9
To a solution of fully protected silyl maltoside 5 (1.5 g,
1.40 mmol) in dry THF (10 mL) was added dropwise
Bu4NF (2.8 mmol, 2.8 mL of a 1 M solution in THF).
The mixture was stirred at room temperature for 1 h
and the solvent was removed in vacuo. The resulting res-
idue was dissolved in DCM (100 mL), washed with H2O
(30 mL), saturated NaHCO3 solution (3 · 30 mL) and
H2O (3 · 30 mL). Concentration in vacuo and column
Fully acetylated methyl thiomaltotrioside 8 (3.43 g,
3.37 mmol) was dissolved in dry MeOH (30 mL) con-
taining a catalytic amount of sodium methoxide and
the mixture was stirred at room temperature until the
reaction was complete, as judged by TLC. Amberlite
IR-120 (H+) ion exchange resin was added to neutralise
the mixture, followed by concentration in vacuo to give