Synthesis of 9-O-acyl- and 4-O-acetyl-sialic acids.

Various 9-O-acyl derivatives of N-acetyl- and N-glycoloyl-neuraminic acid, and O-(5-acetamido-3,5-dideoxy-D-glycero-alpha- and beta-D-galacto-2-nonulopyranosylonic acid)-(2----6)-O-beta-D-galactopyranosyl-(1----4)-D-glucopyranose were regioselectively synthesized by use of ortho esters. In addition, 5-acetamido-4-O-acetyl-D-glycero-D-galacto-2-nonulopyranosonic acid was prepared starting from the benzyl and methyl esters of N-acetylneuraminic acid.