A selective glycosylation strategy enabling access to all stereochemical combinations of tumor associated Thomsen-nouveau (Tn) antigen, D-GalNAc-O-Ser/Thr, has been developed. The key component for selectivity is the phthalimide-protected D- or L-amino acid acceptors which allow access to α- or β-anomers in excellent yields (72-96%) and selectivity (∼100%) when appropriate C-2 substitution is installed. The glycoamino acid intermediates were divergently converted to Tn-based carboxylates or to hydrazides by tandem Pd-C debenzylation followed by treatment with hydrazine hydrate or hydrazine hydrate treatment alone.