Chemical Modification of Maltose. IV. Synthesis of 4-O-α-D-Altropyranosyl-D-glucopyranose

抄録

The new reducing disaccharide 4-O-α-D-altropyranosyl-D-glucopyranose (12) was synthesized by isomerization of secondary hydroxyl groups in the non-reducing part of maltose. Treatment of 1, 6-anhydro-4', 6'-O-benzylidene-2, 2'-di-O-tosyl-β-maltose (2) with methanolic sodium methoxide at room temperature gave the corresponding monoepoxide (3) in 90% yield, in which the oxirane ring is located in the reducing part of maltose. When the reaction was performed at boiling temperature, the diepoxide (5) having α-D-mannopyranosyl-D-mannopyranose configuration was obtained in 77% yield. Compound 5 was also obtainable from 2 in 79% yield. Heating a mixture of 5 and excess potassium hydroxide resulted in trans-diaxial cleavage of both oxirane rings, and 2, 3-di-O-acetyl-1, 6-anhydro-4-O-(2, 3-di-O-acetyl-4, 6-O-benzylidene-α-D-altropyranosyl)-β-D-glucopyranose (6) was isolated in 81.4% yield after acetylation of the cleavage product. Compound 6 was also obtainable from 2 in 59% yield. The disaccharide 12 was prepared as a hygroscopic amorphous powder after removal of the protecting groups of 6 as follows ; debenzylidenation, acetylation, acetolysis, and deacetylation.