Hydroboration and subsequent oxidation of 2-methoxy-3,4-dihydro-2H-pyran gave a 1 :2 mixture of cis-and trans-5-hydroxy-2-methoxytetrahydropyran (2). From the methylated product 4, trons-2,5-dimethoxytetrahydropyran could be obtained by gas-liquid chromatography. The cis-2,5-dimethoxytetrahydropyran (8) was obtained by conversion of 4 to 3-methoxy-3,4-dihydro-2H-pyran (6) which upon bromomethoxylation and subsequent reduction with palladium catalyst gave 8.Both cis-and truns-2,5-dimethoxy-6-methyltetrahydropya (11) were obtained by hydroboration and oxidation of 2-methoxy-6-methyl-3,4-dihydro-2H-pyran (9) followed by methylation of the resulting product.