A concise synthesis of glycosyl-α-amino acid derivatives via homologation of dialdoses into bromo uronic acids and esters

The synthesis of the compounds of the title involves three steps from dialdoses. The reaction between potassium dibromoacetonitrile carbanion and protected dialdoses provides corresponding β-bromo-α-ketonitriles that are easily transformed into α-bromo esters by treatment with methanol or isopropanol or α-bromo acids by treatment with t-BuOH. Substitution of the bromine by sodium azide onto these last compounds and subsequent catalytic hydrogenation of the azide group afford the targeted glycosyl-α-amino acid derivatives. This methodology represents the most rapid access to the key α-amino acid moiety of polyoxins.