14C-labeled antimalarials. I. Synthesis of dl-erythro- and threo-α(2-piperidyl)-2,8-bis(trifluoromethyl)-4-quinolinemethanol-α-14C

Erythro‐ and threo‐ isomers of α‐(2‐piperidyl)‐2,8‐bis‐(triflucoromethyl)‐4‐quinolinemethanol‐α‐14C hydrochloride and methanesulfonate were prepared from labeled carbon dioxide for metabolic and pharmacological studies. Intermediates were 2,8‐bis(trifluoromethyl) cinchoninic‐carboxy‐14C acid and 2,8‐bis(trifluoromethyl)‐4‐quinolyl 2‐pyridyl ketone‐14C. The ratio of erythro to threo isomers formed on hydrogenation of the precursor ketone was 5.6. The diastereomers were separated by recrystallization and preparative tlc. Erythro‐to‐threo conversion was effected by isomerization of the acetylated erythro isomers and deacetylation.