Different metabolites (2-7) of oxapadol 1 were carried out from 3 by known methods. Their acidic hydrolysis provided compounds 4 in which the dioxolane moiety was opened. The reaction of glycerol with compounds 3 gave the dioxolane derivatives 5 which have a hydroxymethyl group and which (R = H) gave by oxidation the carboxylic acid 7. From 3 (R = H), the hydroxy acid 6 has been also prepared.