Synthesis of gamma-lactone-type sialic acid, an isomer of 2,3-dehydrosialic acid.

An efficient synthesis of gamma-lactone-type sialic acid, which is an isomer of 2,3-dehydrosialic acid, was achieved from the corresponding sialic ester. The sialic ester was reconstructed from the gamma-lactone in a 95% yield. The gamma-lactone structure was determined by methylating to its corresponding methyl ether.