A convergent synthesis of trisaccharides with α-Neu5Ac-(2 → 3)-β-D- Gal-(1 → 4)-β-D-GlcNAc and α-Neu5Ac-(2 → 3)-β-D-Gal-(1 → 3)-α-D-GalNAc sequences

The syntheses of three trisaccharides: α-Neu5Ac-(2 → 3)-β-D-Gal-(1 → 4)-β-D-GlcNAc → OMe, α-Neu5Ac-(2 → 3)-β-D-Gal6SO₃Na-(1 → 4)-β-D- GlcNAc → OMe, and α-Neu5Ac-(2 → 3)-β-D-Gal-(1 → 3)-α-D-GalNAc → OBn were accomplished by using either methyl (phenyl 5-acetamido-4,7,8,9-tetra-O- acetyl-3,5-dideoxy-2-thio-β-D-glycero-D-galacto-2-nonulopyranoside)onate or methyl (phenyl N-acetyl-5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2- thio-β-D-glycero-D-galacto-2-nonulopyranoside)onate as the sialyl donor. The N,N-diacetylamino sialyl donor appears to be more reactive than its parent acetamido sugar when allowed to react with an disaccharide acceptor under the same glycosylation conditions. The trisaccharides, as well as the intermediate products, were fully characterized by 2D DQF ¹H-¹H COSY and 2D ROESY spectroscopy. (C) 2000 Elsevier Science Ltd.