Highly stereoselective α-sialylation. Synthesis of GM3-saccharide and a bis-sialic acid unit

Article abstract of DOI:10.1021/jo00116a022

The novel sialyl donor methyl [ethyl 5-acetamido-4,7,8,9-tetra-O-acetyl-2-thio-3-(phenylthio)-2,3,5-trideox y-D-erythro-α-L-gluco-2-nonulopyranosid]onate (6) was synthesized in six steps from N-acetylneuraminic acid in an overall yield of 47%. Donor 6 was shown to be superior to conventional sialyl donors in that the sialylation yields were higher, even with sterically hindered and unreactive sialyl acceptors, and the α/β-selectivity was virtually complete.