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.

Synthesis of 4-thia-[6-(13)C]lysine from [2- (13)C]glycine: access to site-directed isotopomers of 2-aminoethanol, 2-bromoethylamine and 4-thialysine.

4-Thialysine (S-(2-aminoethyl)-L: -cysteine) is an analog of lysine. It has been used as an alternative substrate for lysine in enzymatic reactions. Site-directed isotopomers are often needed for elucidation of mechanism of reactions.

A mild, catalytic and efficient Nazarov cyclization mediated by phosphomolybdic acid.

A mild, selective and efficient Nazarov cyclization of divinyl ketones catalyzed by phosphomolybdic acid (PMA) is described. The process demonstrates a broad substrate scope with functional group tolerance under short reaction times. PMA supported on silica gel is more efficient than the bulk catalyst and is recycled up to three times without significant activity loss.

A facile method for preparation of [(2)h(3)]-sufentanil and its metabolites.

An improved process for the synthesis of sufentanil with an overall yield of 26% is described. The reactive and high yielding N-debenzylation of the piperidine intermediate 7 using a mixture of Pd/C and Pd(OH)(2) was applied to other drug intermediates affording free amines in short reaction times. The deuterium-labeled sufentanil and the metabolite desmethylsufentanil were synthesized applying the optimized process.

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).

Synthesis and crystal structure of [2 + 2] calixsalens.

Efficient synthesis of chiral [2 + 2] macrocyclic tetraimines which display calixarene-like crystal structures has been described, with short reaction times under microwave irradiation.