Synthesis of 6-amino-1-hexyl 2-acetamido-2-deoxy-3-, -4-, and -6- O-β- D-galactopyranosyl-β- D-glucopyranosides

Abstract

6-Aminohexyl glycosides of β- D-Gal→β- D-GlcNAc disaccharides having β-(1→3)-, β-(1→4)-, and β-(1→6)-Iinkages were prepared. 6-(Benzyloxycarbonylamino)-1-hexanol was glycosylated with 2-acetamido-3,4,6-tri- O-acetyl-2-deoxy-α- D-glucopyranosyl chloride, to yield (80 %) a crystalline β-glycoside acetate (3), Deacetylation of 3, followed by isopropylidenation (2,2-dimethoxypropane-TsOH) gave a crystalline 4,6- O-isopropylidene derivative ( 5) in 84% overall yield. Benzylation of 5 [benzyl bromide-BaO-Ba(OH 2), in N,N-dimethylformamide] gave its 3- O-benzyl derivative, which was converted into 6-(benzyloxycarbonylamino)-1-hexyl 2-acetamido-3- O-benzyl-2-deoxy-β- D-glucopyranoside (7) in 69% overall yield. Glycosylation of 7 with 2,3,4,6-tetra- O-acetyl-α- D-galactopyranosyl bromide ( 12) and silver trifluoromethanesulfonate in dry CH 2Cl 2 at 0° yielded the β-(1→6)-disaccharide glycoside ( 17) in 66% yield. Glycosylation of 5 with 12, using mercuric cyanide in 1: 1 (vlv) benzene-nitromethane at 60°, gave the β-(1→3)-disaccharide (86% yield). Limited benzylation of 7, followed by chromatography, gave its 3,6-di- O-benzyl derivative ( 9) in 47% yield. Glycosylation of 9 with 12 yielded the β-(1→4)-disaccharide (89%). Removal of the protecting groups under standard conditions yielded the desired 6-aminohexyl glycosides of the disaccharides.