Stereochemical studies on isomeric 1,2,5-trimethyl-4-phenylpiperidin-4-ols : reactions with acyl chlorides and thionyl chloride

The acylation of some isomeric 2,5-dimethyl-4-phenylpiperidin-4-ols is described and 1H n.m.r. features of the resultant esters are interpreted in terms of configuration and preferred conformation. Evidence of stereochemistry is also provided by the differing behaviour of 1,t-2,t-5- and 1,t-2,c-5-trimethyl-4-phenylpiperidin-r-4-ol towards thionyl chloride; both are dehydrated but the former gives a single product whereas the latter gives a binary mixture of alkenes. The analgesic activities of alcohols and esters related to trimeperidine in mice, as assessed by the hot-plate test, are reported.