The Globo series of tumor-associated antigens are glycosphingolipids implicated in several cancer types. These oligosaccharides contain an alpha-linked galactose. Reported are methods to efficiently install cis-galactosidic linkages by automated solid-phase oligosaccharide synthesis. The complex tumor-associated oligosaccharides Globo-H and Gb-3 were assembled in about 1 day using the new approach that extends the scope of automated oligosaccharide synthesis to structurally more challenging carbohydrates.