Synthesis of N-thioacetyl gangliosides GM1 and GM3

Reaction of de-N-acetyl gangliosides GM1 (1) and GM3 (2b) with methyl dithioacetate (3) afforded N-thioacetyl GM1 (1c) and N-thioacetyl GM3 (2c) with the oxygen of the acetamido group of N-acetylneuraminic acid residue replaced by sulfur.