Construction of carbohydrate-based antitumor vaccines: synthesis of glycosyl amino acids by olefin cross-metathesis

The synthesis of biologically relevant glycosyl amino acids from corresponding O-allyl glycosides is described. The procedure involves a cross-metathesis reaction with Fmoc-l-allylglycine benzyl ester, followed by reduction of the resulting olefin via catalytic hydrogenation, with the concomitant release of the free acid. This method has also been applied to the breast and prostate cancer antigen Globo-H, to afford a hexasaccharide glycosyl amino acid that has been previously incorporated in a polyvalent antitumor vaccine.