1-Tosloxy-2,2-ethylenedioxy-6,10-dimethyl undecanes and undecenes, process for the preparation of 2S*,3R*-3-benzyloxy-6,6-ethylene dioxy-2-methyl-2-(5'-hydroxy-4'-methylpentyl)-oxepane, and use of the latter for the preparation of oxepan-3-ol derivatives