S. Abbas, J. Barlow, K. Matta
Dec 1, 1981
Citations
0
Influential Citations
11
Citations
Journal
Carbohydrate Research
Abstract
Abstract Isopropylidenation of p -nitrophenyl β- d -galactopyranoside under kinetic control afforded the 4,6-acetal ( 2 ). The structure of 2 was established by 1 H- and 13 C-n.m.r. spectroscopy, and confirmed by methylation, and hydrolysis to 2,3-di- O -methyl- d -galactose. Selective benzoylation of 2 with benzoyl chloride in pyridine afforded the 3- O -benzoyl derivative 3 . Isomerization of 3 in a phase-transfer type of reaction gave a mixture of 3 and its 2- O -benzoyl isomer 4 . Glycosidation of 4 (catalyzed by mercuric cyanide) with 2,3,4,6-tetra- O -acetyl-α- d -galactopyranosyl bromide ( 7 ) gave a crystalline disaccharide derivative ( 8 ). O -Deacylation of 8 furnished the disaccharide acetal ( 9 ). The 13 C-n.m.r. spectrum of 9 revealed the presence of a 3,4-acetal, indicating that neither 9 nor 8 was a (1→3)-linked disaccharide derivative. Deacetylation of 9 afforded p -nitrophenyl 6- O -β- d -galactopyranosyl-β- d -galactopyranoside ( 10 ). The (1→6) linkage in 10 was established by permethylation, and hydrolysis to 2,3,4-tri- O -methyl- d -galactose. Compound 10 was converted into the crystalline 2-benzoate ( 11 ) of its 3,4,2′,3′,4′,6′-hexaacetate, and 11 afforded the amorphous 2,3,4,2′,3′,4′,6′-heptaacetate. The disaccharide 10 was also synthesized by condensation of the bromide 7 with p -nitrophenyl 2,3-di- O -acetyl-β- d -galactopyranoside ( 6 ), followed by O -deacetylation; compound 6 was obtained from 2 by way of the crystalline 4,6-acetal 2,3-diacetate.