Thiosugars. XV. Further Contribution on Anomalous High Reactivity of Secondary Methanesulfonic Esters in Thiosugars

抄録

1, 2-Di-S-acetyl-3, 4, 6-tri-O-acetyl-β-D-mannopyranose (X) and methyl 1, 2-dithio-2-S-methyl-3, 4, 6-tri-O-acetyl-β-D-mannopyranoside (XI) were synthesized using an unequivocal route. A detailed comparison of the physical constants and NMR data of X with those of 1, 2-di-S-acetyl-3, 4, 6-tri-O-acetyl-β-D-mannopyranose, which had been reported from our laboratory (H. Nakamura, S. Tejima, M. Akagi, Chem. Pharm. Bull. (Tokyo), 14, 648 (1966).) clarified that the previous compound (VI) was the α-anomer of X. The corresponding methyl 1, 2-dithio-2-S-methyl-3, 4, 6-tri-O-acetyl-α-D-mannopyranoside (VII) was prepared from VI. Reaction of potassium thiolacetate with 2-O-mesyl-3, 4, 6-tri-O-acetyl-β-D-glucopyranosyl N, N-dimethyldithiocarbamate (XVI) afforded three products (XVII, XVIII, VIII) in proportions of 5 : 2 : 3. The structure of the main product (XVII), which had been assigned as 1, 2-dithio-1-N, N-dimethyldithiocarbamoyl-2-S-acetyl-3, 4, 6-tri-O-acetyl-β-D-mannopyranose (S. Ishiguro, S. Tejima, Chem. Pharm. Bull. (Tokyo), 15, 1478 (1967).), was corrected to 1, 2-dithio-1-S-acetyl-2-N, N-dimethyldithiocarbamoyl-3, 4, 6-tri-O-acetyl-β-D-mannopyranose. The by-products, XVIII and VIII, were assigned as 2-N, N-dimethyldithiocarbamoyl-2-deoxy-3, 4, 6-tri-O-acetyl-D-arabino-hexopyranose-1-ene and 1, 2-dideoxy-1, 2-trithiocarbonyl-3, 4, 6-tri-O-acetyl-β-D-mannopyranose, respectively. The reaction mechanisms on the facile substitution of secondary mesyl in thiosugars, which may be more reasonable than before, were discussed.