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Updated: Aug 15, 2026

Preparation and In Vivo Use of an Activity-based Probe for N-acylethanolamine Acid Amidase
Published on: November 23, 2016
Selective endothelin A receptor antagonists. 4. Discovery and structure-activity relationships of stilbene acid and
P C Astles1, T J Brown, F Halley
1Rhône-Poulenc Rorer, Dagenham Research Centre, Rainham Road South, Dagenham, Essex, RM10 7XS U.K.
Abstract:
This publication describes the synthesis and optimization of a novel series of stilbene endothelin antagonists. Analysis of the SAR established for previous papers in this series prompted the design and synthesis of (Z)-4-phenyl-5-(3-benzyloxyphenyl)pent-4-enoic acid 3 which was found to be a moderately active inhibitor of the binding of [125I]ET-1 to ETA receptors with an IC50 of 6 microM. More interestingly, the intermediate compound (E)-2-phenyl-3-(3-benzyloxyphenyl)propenoic acid 5 was equiactive with 3. Optimization of 5 resulted in the preparation of (E)-2-phenyl-3-(2-cyano-5-(thien-3-ylmethoxy))phenylprope noic acid 18 (RPR111723) which had an IC50 in the binding assay of 80 nM on the ETA receptor and a pKB of 6.5 in the functional assay, measured on rat aortic strips. Reduction of the acid group of 5 gave the first nonacidic ETA antagonist in our series, (E)-2-phenyl-3-(3-benzyloxyphenoxy)prop2-enol 6 with an IC50 of 20 microM. Optimization of 6 resulted in the preparation of 2-(2-methylphenyl)-3-(2-cyano-5-(thien-3-ylmethyl)phenyl)pro p-2-enol 33 with an IC50 of 300 nM on the ETA receptor.
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