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Amlodipine Benzenesulfonate: A Mechanistic Investigation of Its Industrial Preparation via Detritylation of N-tritylamlodipine and Related NMR Studies

By Borut Furlan, Simona Golič Grdadolnik, Stanko Hočevar, Darko Kocjan, Janez Levec, Howard Maskill, Hana Navrátilová, Jiří Pospíšil, Milan Potáček, Uroš Urleb and Janko Žmitek

Abstract

Kinetics and product analysis of detritylation of N-tritylamlodipine by benzenesulfonic acid in methanol, methanol-chloroform (volume ratio 9:1), ethanol, 2-propanol, and methanol/2-propanol (mole ratio 1:1) have been investigated by HPLC; amongst these reaction conditions are ones closely similar to those of one method of manufacturing amlodipine benzenesulfonate. Kinetics of detritylation of Ntritylamlodipine have also been investigated in methanol-d4 by 1H NMR spectroscopy and the agreement with the results by HPLC is good. The rate of detritylation increases with increasing concentrations of benzenesulfonic acid, and p-methoxy-substituents in the trityl group have been shown to lead to faster reactions. In methanol, the rate is hardly affected by 10 % (vol. fraction) chloroform. These studies relate to mechanistic investigations of acid-catalysed deaminations of methoxy-substituted tritylalkylamines, and Arrhenius activation parameters (Ea and A) are similar indicating a common generic mechanism. Acid-catalysed trans-esterification has been shown by HPLC to accompany detritylation in methanol, and attendant protium-deuterium exchange in the methyl at C6 by reversible acid-catalysed iminium ion formation in the 4-aryl-1,4-dihydropyridine moiety of both N-tritylamlodipine and amlodipine has been investigated in deuteriated methanol by 1H, 13C, and 15N NMR spectroscopy

Topics: QD
Publisher: The Croatian Chemical Society
Year: 2009
OAI identifier: oai:eprints.hud.ac.uk:5501

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