Elmer 150 Fourier Transform spectrophotometer. Mass spectra
were recorded on VG Micromass 30F, ZAB 1F, Masslab20-250,
Micromass Platform 1 APCI, or Trio-1 GCMS (DB-5 column)
spectrometers, using desorption chemical ionization (NH3 DCI),
electron impact (EI), electron spray ionization (ESI), chemical
ionization (NH3 CI), atmospheric pressure chemical ionization
(APCI), and fast atom bombardment (FAB) techniques as stated.
Optical rotations were measured on a Perkin-Elmer 241 polarimeter
with a path length of 1 dm. Concentrations are given in g (100 ml)−1.
Microanalyses were performed by the microanalytical services of
the Inorganic Chemistry Laboratory, South Parks Road, Oxford.
Thin layer chromatography (t.l.c.) was carried out on Merck glass-
backed sheets, pre-coated with 60F254 silica. Plates were developed
using 0.2% w/v cerium(IV) sulfate and 5% ammonium molybdate
in 2 M sulfuric acid. Flash chromatography was carried out using
Sorbsil C60 40/60 silica. Solvents and available reagents were dried
and purified before use according to standard procedures; methanol
was distilled from magnesium methoxide, dichloromethane was
distilled from calcium hydride, pyridine was distilled from calcium
hydride and stored over potassium hydroxide, and tetrahydrofuran
was distilled from a solution of sodium benzophenone ketyl
immediately before use.
(2H, ABq, JAB 11.9 Hz, PhCH2), 4.61 (1H, d, J 11.0 Hz, PhCHH),
4.74 (1H, d, J 10.3 Hz, PhCHH), 4.83–4.92 (4H, m, 2 × PhCH2),
4.87 (1H, d, J1,2 9.4 Hz, H-1), 7.19–8.12 (25H, m, ArH).
Phenyl-2,3,4,6-tetra-O-benzyl-1-thio--D-glucopyranoside
Phenyl-1-thio--D-glucopyranoside33 (1.5 g, 5.52 mmol) was
dissolved in dimethylformamide (20 ml) under argon in a dry
flask and benzyl bromide (3.3 ml, 27.6 mmol) added. The reaction
mixture was cooled to 0 °C, sodium hydride (60% dispersion
in mineral oil, 795 mg, 33.1 mmol) added portionwise and the
reaction allowed to warm slowly to room temperature. After 18 h,
t.l.c. (ethyl acetate:petrol, 1:8) showed the formation of a single
product (Rf 0.3) and the absence of starting material (Rf 0). MeOH
(50 ml) was added and the reaction mixture stirred for 15 min, then
concentrated in vacuo. The residue was dissolved in ethyl acetate
(100 ml), washed with brine (3 × 100 ml) and the aqueous layer
re-extracted with ethyl acetate (100 ml). The combined aqueous
layers were dried (MgSO4), filtered and concentrated in vacuo.
The residue was purified by flash column chromatography (ethyl
acetate:petrol, 1:8) to afford phenyl-2,3,4,6-tetra-O-benzyl-1-thio-
-D-glucopyranoside (3.2 g, 92%) as a white crystalline solid, m.p.
90–91 °C (ethyl acetate/petrol) (lit.,34 91–92 °C); []D22 +0.5 (c, 1.0
in CHCl3) {lit.,35 []D20 +0.8 (c, 5.0 in CHCl3)}; H (400 MHz, CDCl3)
3.53–3.58 (1H, m, H-5), 3.55 (1H, at, J 9.2 Hz, H-2), 3.69 (1H, at,
H-3), 3.73–3.78 (2H, m, H-4, H-6), 3.83 (1H, dd, J5,6′ 10.9 Hz, J6,6′
1.9 Hz, H-6′), 4.58, 4.65 (2H, ABq, JAB 12.0 Hz, PhCH2), 4.63,
4.87 (2H, ABq, JAB 10.9 Hz, PhCH2), 4.71 (1H, d, J1,2 9.9 Hz, H-1),
4.77, 4.93 (2H, ABq, JAB 10.3 Hz, PhCH2), 4.89, 4.94 (2H, ABq, JAB
10.9 Hz, PhCH2), 7.22–7.65 (25H, m, ArH).
Phenyl-2,3,4,6-tetra-O-benzoyl-1-seleno--D-glucopyranoside
Diphenyl diselenide (227 mg, 0.71 mmol) was dissolved in
ethanol (50 ml) and sodium borohydride (110 mg, 2.89 mmol)
added portionwise. The solution was stirred for 15 min, at which
point 2,3,4,6,-tetra-O-benzoyl--D-glucopyranosyl iodide30 (2.5 g,
3.54 mmol) was added and the reaction left to stir. After 18 h, t.l.c.
(ethyl acetate:petrol, 1:2) indicated the formation of a single
product (Rf 0.4) and the absence of starting material (Rf 0.5). The
reaction mixture was diluted with ethyl acetate (100 ml), washed
with sodium thiosulfate (100 ml of a 10% aqueous solution) and
water (100 ml), dried (MgSO4), filtered and concentrated in vacuo.
The residue was purified by flash column chromatography (ethyl
acetate:petrol, 1:4) to afford phenyl-2,3,4,6-tetra-O-benzoyl-1-
seleno--D-glucopyranoside (1.82 g, 79%) as a white crystalline
solid, m.p. 170 °C (ethanol) (lit.,31 169.5–171 °C); []2D2 +21.4 (c,
1.0 in CHCl3) {lit.,31 []D25 +20.5 (c, 1.0 in CHCl3)}; H (400 MHz,
CDCl3) 4.13 (1H, ddd, J4,5 10.0 Hz, J5,6 6.0 Hz, J5,6′ 2.7 Hz, H-5),
4.50 (1H, dd, J6,6′ 12.1 Hz, H-6), 4.71 (1H, dd, H-6′), 5.08 (1H, d,
J1,2 10.2 Hz, H-1), 5.52 (1H, at, J 9.7 Hz, H-2), 5.64 (1H, at, H-4),
5.95 (1H, at, H-3), 7.14–8.07 (25H, m, ArH).
p-Tolyl-2,3,4,6-O-benzoyl-1-thio--D-glucopyranoside
p-Tolyl-1-thio-glucopyranoside36 (1.0 g, 3.50 mmol) was
dissolved in pyridine (50 ml) under argon in a flame-dried flask
and benzoyl chloride (3.3 ml, 28.0 mmol) added. The mixture
was stirred for 18 h, at which point t.l.c. (ethyl acetate:petrol,
1:3) indicated the formation of a major product (Rf 0.3) and the
absence of starting material (Rf 0). The reaction was diluted with
dichloromethane (100 ml) and washed with HCl (2 × 100 ml of a
0.1 M aqueous solution). The aqueous phase was re-extracted with
dichloromethane (100 ml) and the combined organic layers washed
with sodium hydrogen carbonate (2 × 100 ml of a saturated aqueous
solution), brine (100 ml), dried (MgSO4), filtered and concentrated
in vacuo to afford p-tolyl-2,3,4,6-O-benzoyl-1-thio--D-glucopy-
ranoside (2.2 g, 88%) as a white crystalline solid, m.p. 186–188
°C (ethanol) (lit.,14 186–188 °C); []D25 +21 (c, 1.0 in CHCl3) {lit.,14
[]2D0 +23 (c, 1.0 in CHCl3)}; H (400 MHz, CDCl3) 2.29 (3H, s,
PhCH3), 4.20 (1H, ddd, J4,5 9.8 Hz, J5,6 5.8 Hz, J5,6′ 2.8 Hz, H-5),
4.49 (1H, dd, J6,6′ 12.1 Hz, H-6), 4.71 (1H, dd, H-6′), 5.01 (1H,
d, J1,2 9.7 Hz, H-1), 5.48 (1H, at, J 9.7 Hz, H-2), 5.62 (1H, at,
J 9.8 Hz, H-4), 5.93 (1H, at, J 9.6 Hz, H-3), 6.95 (2H, d, J 8.0 Hz,
ArH), 7.26–7.63 (14H, m, ArH), 7.81 (2H, dd, J 1.1 Hz, J 8.3 Hz,
ArH), 7.91 (2H, dd, J 1.2 Hz, J 8.1 Hz,ArH), 8.00 (2H, dd, J 1.1 Hz,
J 8.1 Hz, ArH), 8.07 (2H, dd, J 1.0 Hz, J 8.1 Hz, ArH).
Phenyl-2,3,4,6-tetra-O-benzyl-1-seleno--D-glucopyranoside
Phenyl-2,3,4,6-tetra-O-benzoyl-1-seleno--D-glucopyranoside
(1.2 g, 1.63 mmol) was dissolved in methanol (20 ml) under argon
in a dry flask and a solution of sodium (114 mg, 9.35 mmol) in
methanol (20 ml) was added. After 5 h, t.l.c. (ethyl acetate:petrol,
1:4) showed the formation of a single product (Rf 0) and the absence
of starting material (Rf 0.3). The reaction mixture was neutralised
with ion exchange resin (Dowex 50), filtered and then concentrated
in vacuo. The residue was dissolved in dimethylformamide (60 ml),
the solution cooled to 0 °C and benzyl bromide (1.0 ml, 8.16 mmol)
added. Sodium hydride (60% dispersion in mineral oil, 390 mg,
9.75 mmol) was added portionwise and the reaction mixture
allowed to warm slowly to room temperature, with stirring. After
16 h, t.l.c. (ethyl acetate:petrol, 1:8) indicated the formation of a
major product (Rf 0.3) and the absence of starting material (Rf 0). The
reaction mixture was diluted with ethyl acetate (100 ml) and washed
with brine (3 × 100 ml). The organic phase was dried (MgSO4),
filtered and concentrated in vacuo. The residue was purified by
flash column chromatography (ethyl acetate:petrol, 1:8) to afford
phenyl-2,3,4,6-tetra-O-benzyl-1-seleno--D-glucopyranoside
(1.0 g, 89%) as a white crystalline solid, m.p. 78–79 °C (ethanol)
(lit.,32 79 °C); []2D2 −12.8 (c, 1.0 in CHCl3) {lit.,32 []2D2 +11 (c, 1.0 in
CH2Cl2)}; H (400 MHz, CDCl3) 3.48–3.51 (1H, m, H-5), 3.54 (1H,
at, J 9.7 Hz, H-6), 3.65–3.73 (2H, m, H-3, H-4), 3.75 (1H, dd, J5,6
4.5 Hz, J6,6′ 10.9 Hz H-6), 3.81 (1H, dd, J5,6′2.1 Hz, H-6′), 4.55, 4.63
p-Tolyl-2,3,4,6-O-benzyl-1-thio--D-glucopyranoside
p-Tolyl-1-thio-glucopyranoside36 (750 g, 3.50 mmol) was dissolved
in dimethylformamide (20 ml) under argon in a dry flask and benzyl
bromide (1.6 ml, 13.1 mmol) added. The mixture was cooled to
0 °C and sodium hydride (60% dispersion in mineral oil) (630 mg,
15.7 mmol) added portionwise. The reaction mixture was stirred
for 3 d, at which point t.l.c. (ethyl acetate:petrol, 1:8) indicated
the formation of a major product (Rf 0.3) and the absence of
starting material (Rf 0). Methanol (20 ml) was added and the
solution was stirred for a further 15 min, the reaction mixture
was then concentrated in vacuo. The residue was taken up in ethyl
acetate (100 ml) and the resulting solution washed with brine
(3 × 100 ml), dried (MgSO4), filtered and concentrated in vacuo.
The residue was purified by flash column chromatography (ethyl
acetate:petrol, 1:8) to afford p-tolyl-2,3,4,6-O-benzyl-1-thio--
O r g . B i o m o l . C h e m . , 2 0 0 4 , 2 , 2 1 8 8 – 2 1 9 4
2 1 9 3