Simple and Rapid Procedures for the Synthesis of 5-Acylated 4 beta-Acylamido- and 4 beta-Acetoxyneuraminic Acid Glycals

Two simple and rapid procedures affording 4 beta-acylamido- and 4 beta-acetoxyneuraminic acid glycals acylated or perfluoroacylated at the 5-amino group are reported. The first protocol avoids the formation of oxazolines to synthesize the 4 beta-acetamido glycals through the Ritter reaction. The second passes through the oxazoline derivative to prepare 4 beta-acetoxyneuraminic acid glycals. Both protocols start from peracetylated methyl neuraminate, acylated at the amino group with a normal, a glycolyl, or a perfluoroacyl group, or with the corresponding peracetylated glycal methyl esters (of the DANA or FANA series).