Abstract
Benzoylation of N-acetylneuraminic acid (Neu5Ac) gave a variety of partially benzoylated bicyclic 1, 7-lactone derivatives and a perbenzoylated bicyclic 1, 4-lactone derivative in good yields. The structures of these compounds were elucidated mainly by means of proton nuclear magnetic resonance spectroscopy.Further, pivaloylation and ethoxycarbonylation of Neu5Ac also gave the corresponding acylated bicyclic lactone derivatives.These results allowed us to postulate a mechanism for the formation of bicyclic lactone derivatives in the acylation of Neu5Ac. Furthermore, treatment of Neu5Ac with diazomethane in an acidic methanol solution gave methyl a-D-neuraminoside methyl ester and a monocyclic 2-O-methyl-y-lactone derivative in 18% and 29% yields, respectively.These results provided information about the equilibrium of Neu5Ac in basic and acidic media.
