Atropisomerism in Rilpivirine hydrochloride: Spectroscopic characterization of Rilpivirine and related impurities.

Nuclear magnetic resonance (NMR) technique has been used to find the property of atropisomerism in Rilpivirine hydrochloride by variable temperature analysis and various 2D techniques. Both the Rilpivirine hydrochloride (E-isomer) and Impurity-A (Z-isomer) isomers have been differentiated and confirmed by NMR and ultraviolet techniques. Preparative high-performance liquid chromatography isolation for Impurity-A is followed by spectroscopic (NMR, mass spectra, and infrared) investigation that provides a perfect solution for determination of the structure of Rilpivirine and related impurities.

Optimized and validated spectrophotometric methods for the determination of raloxifene in pharmaceuticals using permanganate.

Two simple and sensitive spectrophotometric methods are described for the determination of raloxifene hydrochloride (RLX) in pure form and in tablets. The first method (method A) is based on the formation of a yellowish-brown chromogen peaking at 430 nm when RLX was reacted with permanganate in acetic acid medium. In the second method (method B), RLX was reacted with a measured excess of permanganate in H2SO4 medium followed by the spectrophotometric measurement of the unreacted KMnO4 at 550 nm.

Unusual detritylation of tritylated tetrazole in Sartan molecules.

Tritylated tetrazole of 2a underwent unusual detritylation under basic reaction condition during the synthesis of methyl ether of olmesartan medoxomil 1. The unusual detritylation was found to be a common feature in the case of all tetrazole containing Sartan molecules (3-7).