The total synthesis of the Hakomori MBr1 antigen, heavily expressed on human breast tumors, is related. The construction involved the assembly of four glycals : (17 (twice), 18, 20, and 26) and an L-fucose derivative, 34. The sensitivity of the stereochemistry of sulfonamido galactosylation by a terminal galactose ring as a function of the state of protection status of its C-4 alcohol was exploited in a key step. (See the formation of compound 51.) The synthesis served to confirm the Hakomori assignment of structure, and paves the way for immunoconjugation.