Syntheses of Isomaltose, Isomaltotetraose, and Isomaltooctaose

Abstract

Abstract Ethyl 2,3,4-tri-O-benzyl-6-O-p-nitrobenzoyl-1-thio-α-d-glucopyranoside (I–1) was brominated and subsequently condensed with a deacylated derivative of I–1 in nitromethane in the presence of 2,6-lutidine to give ethyl 2,2′,3,3′,4,4′-hexa-O-benzyl-6′-O-p-nitrobenzoyl-1-thio-α-isomaltoside (I–2) in a 92% yield. These processes were repeated on I–2 to give the blocked tetrasaccharide (I–4) in a 49% yield. Finally, the octasaccharide (I–8) was synthesized in an 11% yield by one more repetition of this reaction cycle. The blocked glycosides, I–2, I–4, and I–8, gave isomaltose, isomaltotetraose, and isomaltooctaose respectively after the sequence of unblocking processes: bromolysis, hydrolysis, methanolysis, and hydrogenolysis.