1993 Volume 41 Issue 1 Pages 90-96
When acetylated pyranose-1, 2-(ethyl orthyl orthoacetates) were hydrolyzed in acidic solvents, the ring-opening of the orthoacetate rings was influenced by the axial or equatorial OAc group at C-4 on the pyranoses; on acid-catalyzed hydrolysis, 3, 4, 6-tri-O-acetyl-α-D-glactopyranose- (8) and methyl 3, 4-di-O-acetyl-α-D-galacturonatopyranose-1, 2-(ethyl orthoacetate) (16) having an axial OAc group at C-4 on the pyranose rings gave 1, 3, 4, 6-tetra-O-acetyl-α-D-galactopyranose (9) and methyl 1, 3, 4-tri-O-acetyl-α-D-galacturonatopyranose (23), respectively, whereas 3, 4, 6-tri-O-acetyl-α-D-glucopyranose- (10) and methyl 3, 4-di-O-acetyl-α-D-glucuronatopyranose-1, 2-(ethyl orthoacetate) (22)having an equatorial OAc group at C-4 on the pyranose rings gave 2, 3, 4, 6-tetra-O-acetyl-D-glucopyranose (11) and methyl 2, 3, 4-tri-O-acetyl-D-glucuronatopyranose (24), respectively. On the acid-catalyzed hydrolysis, 3, 4-di-O-acetyl-β-L-arabinopyranose-1, 2-(ethyl orthoacetate) (34) having an axial OAc group at C-4 on the pyranose ring gave a mixture of 1, 3, 4-tri-O-acetyl-β-L- (35) and 2, 3, 4-tri-O-acetyl-L-arabinopyranose (36). These selectivities of ring-opening of the 1, 2-(orthoacetates) were considered to have resulted from the differences of the conformers fo the 1, 2-(orthoacids)intermediates derived from the 1, 2-(othoacetates) and the orientation of the acetyl groups at C-4 on the pyranose rings.
