A convergent total synthesis of F1 alpha antigen, a member of the tumor-associated O-linked mucin glycosyl amino acids, was accomplished by one-pot sequential glycosylation. In the first step, the corresponding disaccharide was formed from galactosyl phenylcarbonate 2 or fluoride 3 and thioglycoside 4 by the promotion of TrB(C6F5)(4) or TfOH, and following glycosylation of glycosyl amino acid 5 by further addition of N-iodosuccinimide(NIS) afforded protected F1 alpha in 80 or 89% overall yield, respectively. By the subsequent deprotection, F1 alpha antigen was obtained in good yield.