Abstract A synthesis is described of the pseudo-trisaccharideantibiotic, destomycinC, which contains orthoester and β- d -talopyranosidic linkages. A β- d -mannopyranosidic linkage was formed first in the presence of silver triflate in tetrahydrofuran. Glycosylidenation with trimethylsilyl triflate in ether proceeded successfully without anomerisation of the β- d -mannopyranosidic linkage. The β-