The preparation and proton-induced cyclization of silyl-substituted 4,S-epoxy-l-alkanols is described The regioselectivity of intramolecular attack of the hydroxy group on the epoxy silane moiety is highly dependent on the configuration of the epoxy alcohols employed. Thus 1,4-anti epoxy alcohols exclusively yield tetrahydropyrans whereas the corresponding 1,4-syn derivates furnish a diastereomeric