The preparation of the two diastereoisomeric 3-methoxy-2-oxa-6-thiabicyclo-[3.2.0]heptan-4-ols4and5from D-xylose1viamethyl 2,3-anhydro-α-D-ribofuranoside and the corresponding β-anomer is described. Oxidation of4and5yields the sulfoxides6and7and the sulfones8. – On the other hand, the two diastereoisomeric 3-methoxybicyclo[2.2.1]heptan-7-ols11and12are obtained from methyl 5-acetylthio-5-deoxy-2-O-mesyl-D-xylofuranosides9and10viaMitsunobu reaction and intramolecular cyclization. – The stereoisomeric counterparts of4and5, 13and14, are obtained in only four steps from L-arabinose.