C-linked disaccharide analogue of the Thomsen-Friedenreich (T)-epitope alpha-O-conjugated to L-serine

Condensation of a silylated beta-D-galactopyranosylaldehyde (3) with isolevoglucosenone (4) in the presence of Et(2)AII provided bicyclic enone 5. Subsequent addition of BnNHOMe gave adduct 6, which was converted into 4-O-acetyl-1,6-anhydro-3-C-[ R)1.3,4,5,7-penta-O-acetyl-2,6-anhydro-D-glycero-L-manno-heptitol-1-C-yl ]-2- azido-2,3-dideoxy-beta-D-galacto-hexopy-ranose after liberation of the 2-amino group, its transformation into a 2-azido moiety, desilylation, and peracetylation. Ring-opening of the 1,6-anhydro galactopyranosyl unit and O-glycosidation with Fmoc-Ser-O-tBu afforded a 5:1 mixture of alpha- and beta-galactosides. Treatment with CH3COSH gave pure N-[(9H-fluoren-9-ylmethoxy)carbonyl]- [4,6-di-0-acetyl-3-C+1 R)-2,6-anhydro 1,3,4,5,7- penta-O- acetyl- D-glycero- Linanno-heptitol-1-C-yl]-2-[(N-acetyl)- amino] -2,3-dideoxy-alpha- D-galactopyranosyl-L-serine tert-butyl ester (2), a protected form of a C-disaccharide analogue of the Thomsen-Friedenreich (or T) epitope (alpha-D-Galp-(1-3)-alpha-D-GalNAcp) alpha-O-conjugated to L-serine.