TADALAFIL CIS-(1R,3R)-N- CHLOROACETYLTETRAHYDRO B-C

Tadalafil cis-(1R,3R)-N-chloroacetyltetrahydro B-C is a stereoisomeric impurity arising from the enantioselective acetylation of the tetrahydro-pyrimidine core in tadalafil synthesis. The (1R,3R) configuration introduces a cis-oriented chloroacetyl substituent at the N-position of a partially saturated bicyclic framework, differing from the parent drug by a chlorinated acyl chain and altered ring geometry. This impurity forms via non-optimal reaction conditions during API manufacturing. Serves as an HPLC reference standard for quantifying enantiomeric purity in tadalafil drug substance analysis.