Selective method for plasma quantitation of the stereoisomers of a new aminotetralin by high-performance liquid chromatography with electrochemical detection

A high-performance liquid chromatographic method is described for the quantitation in plasma of the four stereoisomers of a new aminotetralin, (SRR, RSS)(SRS, RSR)-5,6-dimethoxy-2-[3'-(p-hydroxyphenyl)-3'-hydroxy-2'- propyl]aminotetralin (CHF 1255, internal code). After liquid-liquid extraction of the drug, separation was obtained after chiral derivatization with R-(+)-alpha-methylbenzyl isocyanate. The selective derivatization of the amino group was obtained by controlling the pH of the reaction medium at 7.5. The reaction was quantitative after a period of 16 h. The structures of the urea derivatives were confirmed by proton nuclear magnetic resonance spectroscopy and high-performance liquid chromatography with mass spectrometric detection. The use of an electrochemical detector, operating in the oxidative mode, allows the quantitation in plasma of all four urea derivatives at the nanogram level. The method was demonstrated to be precise, reproducible and applicable to pharmacokinetics studies after administration of the two epimeric racemates.