Synthesis of oligosaccharides designed to form micelles, corresponding to structures found in ovarian cyst fluid

The syntheses of alpha-D-GlcpNAc-(1-->4)-beta-D-Galp-(1-->4)-beta-D-GlcNAc-(1-->O)-(CH2)(15)CH3 (1) and fragments thereof, corresponding to structures found in human ovarian cyst fluid, are described. Silver triflate promoted coupling of 3.4,6-tri-O-acetyl-2-azido-2-deoxy-beta-D-glucopyranosyl bromide (12) and galactose acceptor (11) gave a disaccharide donor (13), which was readily transformed into the corresponding bromo-derivative 18. For the synthesis of disaccharide beta-D-Galp-(1-->4)-D-GlcNAc, several differently protected glucosamine accepters were prepared. It was found that cetyl alcohol needed to be introduced after the formation of the P-galactoside bond. Glycosylation of pent-4-enyl 3,6-di-O-benzyl-2-deoxy-2-tetrachlorophthalimido-beta-D-glucopyranoside (30) with (3,4,6-tri-O-acetyl-2-azido-2-deoxy-alpha-D-glucopyranosyl)-(1-->4)-2,3,6-tri-O-benzoyl-alpha-D-galactopyranosyl bromide (18) by use of silver triflate as promoter gave the desired trisaccharide 31. Finally 31 was transformed via coupling to the long alkyl chain aglycon and deprotection into the title compound 1.