Issue 33, 2022, Issue in Progress

A cyanide-catalyzed imino-Stetter reaction enables the concise total syntheses of rucaparib

Abstract

Two routes toward the synthesis of rucaparib, an FDA-approved drug used for the treatment of ovarian and prostate cancers, have been developed from commercially available starting materials utilizing the cyanide-catalyzed imino-Stetter reaction as the key step for the construction of the indole motif bearing all the desired substituents in their correct positions. In the first-generation synthesis, meta-fluorobenzoate, the starting material currently used in the process chemistry route of rucaparib, was converted into 4,6-disubstituted 2-aminocinnamic acid derivatives (ester or amide). The cyanide-catalyzed imino-Stetter reaction of aldimines derived from the resulting 2-aminocinnamic acid derivatives and a commercially available aldehyde afforded the desired indole-3-acetic acid derivatives. The final azepinone formation completed the total synthesis of rucaparib in 27% overall yield. To resolve the issues raised in the first-generation synthesis, we further developed a second-generation synthesis of rucaparib. The Heck reaction of a commercially available ortho-iodoaniline derivative with acrylonitrile provided 4,6-disubstituted 2-aminocinnamonitrile, which was subjected to the imino-Stetter reaction with the same aldehyde to provide the desired indole-3-acetonitrile product. Subsequent construction of the azepinone scaffold completed the total synthesis of rucaparib in 59% overall yield over three separation operations. The synthetic strategy reported herein can provide a highly practical route to access rucaparib from commercially available starting materials (5.2% overall yield in the current process chemistry route vs. 59% overall yield in the second-generation synthesis).

Graphical abstract: A cyanide-catalyzed imino-Stetter reaction enables the concise total syntheses of rucaparib

Supplementary files

Article information

Article type
Paper
Submitted
11 Jun 2022
Accepted
12 Jul 2022
First published
01 Aug 2022
This article is Open Access
Creative Commons BY-NC license

RSC Adv., 2022,12, 21172-21180

A cyanide-catalyzed imino-Stetter reaction enables the concise total syntheses of rucaparib

J. Park and C. Cheon, RSC Adv., 2022, 12, 21172 DOI: 10.1039/D2RA03619C

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