A successful synthesis of O-sulfated syndecan-1-like (Q23-E120) glyco-polypeptide was accomplished. The synthesis features the integration of an O-sulfated carbohydrate-bearing glycopeptide cassette with efficient protein ligation strategies, overcoming the acid lability of carbohydrate sulfates as a major hurdle in solid-phase peptide synthesis. Crucial to the synthesis is the microwave-assisted Ag(I) ligation, which afforded the ligation product in improved overall yield. This O-sulfated syndecan-1 (Q23-E120) is the longest O-sulfated glyco-polypeptide prepared to date.