ORDER
REPRINTS
662
POZSGAY
EXPERIMENTAL
General Methods. All chemicals were commercial grade and were used
without purification. Anhydrous solvents were obtained from Aldrich. Column
chromatography was performed on silica gel 60 (0.040–0.063 mm). Melting points
were taken on a Meltemp capillary melting point apparatus and are uncorrected.
Optical rotations were measured at 23 °C with a Perkin-Elmer Type 341 polarime-
ter in CHCl3 unless stated otherwise. The 1H and 13 C NMR spectra were recorded
at 500 and 125 MHz nominal frequencies, respectively. Internal references: TMS
(0.00 ppm) for 1H for solutions in CDCl3 and CDCl3 (77.00 ppm) for 13C for solu-
tions in CDCl3. Coupling constants are given in Hz. The mass spectra were
recorded at the Laboratory of Bioorganic Chemistry, NIDDK, NIH, Bethesda, MD.
Ammonia was used as the ionizing gas for the chemical ionization (CI) mass spec-
tra. Elemental analyses were performed by Atlantic Microlab, Inc., Norcross, GA.
Phenyl 1-thio-ꢀ-D-mannopyranoside (1) was obtained from acetobromo-
mannose and thiophenol essentially as described in ref. 14. The following modifi-
cations were made. Phenyl 2,3,4,6-tetra-O-acetyl-1-thio-ꢀ-D-mannopyranoside
was purified by filtration through a silica gel column. Removal of the O-acetyl
groups (Zemplén) followed by stirring the solid residue in ethyl acetate for several
hours afforded crystalline 1: mp sintering above 180 °C, [ꢁ]D ꢂ76° (c 1.1, MeOH).
For NMR data, see ref. 14.
Phenyl 2,3:4,6-di-O-isopropylidene-1-thio-ꢀ-D-mannopyranoside (2).
To a stirred mixture of phenyl 1-thio-ꢀ-D-mannopyranoside (1) (54.0 g, 198 mmol),
acetone (250 mL), and 2,2-dimethoxypropane (800 mL) was added Sc(OTf)3 (500
mg). After dissolution (ca. 20 min) approx. 600 mL of the volatiles were removed
by distillation. Acetone (500 mL) was added to the crystalline mixture. After dis-
solution, the solution was concentrated to approx. 500 mL by distillation followed
by addition of Et3N (3 mL) and removal of the volatiles under diminished pressure.
To the residue was added CH2Cl2 followed by concentration. The crystalline
residue was dissolved in CH2Cl2 (300 mL). The solution was extracted with water
twice (150 mL each). The combined organic layer was concentrated to afford 2 (68
g, 93%) as a crystalline material: mp 140–142 °C, [ꢁ]D ꢂ145° (c 0.7); NMR 1H ꢃ
7.53ꢂ7.39 (m, 2 H), 7.34ꢂ7.26 (m, 3 H), 5.10 (d, 1 H, J ꢄ 2.3), 4.46 (dd, 1 H, J
ꢄ 2.3, J ꢄ 5.3), 4.08 (dd, 1 H, J ꢄ 5.3, J ꢀ 8), 3.92 (dd, 1 H, J ꢄ 5.8, J ꢄ 11.0),
3.87 (dd, 1 H, J ꢀ 8, J ꢄ 9.8), 3.85 (t, 1 H, J ꢄ 11.0), 3.18 (m, 1 H), 1.62 and 1.52
(2 s, 2 ꢅ 3 H), 1.42 (s, 6 H); 13C, ꢃ 131.2, 129.0, 127.7, 110.6, 99.7, 84.7, 76.6, 76.2,
ꢆ
72.4, 69.8, 61.8, 29.0, 28.3, 26.3, 18.8; CI-MS m/z 370 (MꢆNH4 ).
Anal. Calcd for C18H24O5S (352.45): C, 61.34; H, 6.86. Found: C, 61.53; H,
6.71.
Phenyl 4,6-di-O-acetyl-2,3-O-isopropylidene-1-thio-ꢀ-D-mannopyra-
noside (4). A stirred mixture of 2 (32.0 g) in CH2Cl2 (30 mL), MeOH (80 mL),
and acetic acid (40 mL) was boiled under reflux for 4–5 h. Boiling was discontin-