are prepared by single-stage reaction of alkoxydihydropyrans of the formula (II) with water and hydrogen in the presence of a catalyst comprising oxides of nickel, zirconium and copper. In the formulae (I) and (II), R, R′, R″, R′″ can be identical or different and are each hydrogen or a linear or branched saturated hydrocarbon radical having from 1 to 20 carbon atoms in which the hydrocarbon chain may contain O, S and N as heteroatoms and which may be monosubstituted or polysubstituted by hydroxy, thiol or amino groups or halogens.