Four routes towards the synthesis of the natural dihydropyrans 1, i.e. from chiral oxiranes 9 as C2O building blocks and sulfur-substituted allyl (14) or propargyl (10, 11) anions as C3 fragments, have been investigated. The resulting C5O derivatives 4, 8 could be cyclized after generation of a carbonyl group by oxidation (6, 7) or hydrolysis (8). Here, the Pummerer reaction of 6 turned out to be only