AN ALTERNATE SYNTHESIS OF THE POTENT ANTIMUSCARINIC AGENT SILA-BIPERIDEN

Abstract

Sila-biperiden, 9x(RS,SR ), i. e. racemic (SiRS, C2SR)-(exo-bicyclo[2.2.1]hept-5-en-2-yl)phenyl(2-piperidinoethyl)silanol, the silicon analogue of the antimuscarinic agent biperiden, is prepared by a seven-step synthesis. The first step consists in the hydrosilylation of 5-exo-bromobicyclo[2.2.1]-hept-2-ene (2) with dichloro(phenyl)silane (1) in the presence of H₂PtCl₆. The product of the last synthetic step is a mixture of four endo- (9n) and four exo-diastereomers (9x) of (bicyclo[2.2.1]hept-5-en-2-yl)phenyl(2-piperidinoethyl)silanol and of the (tricyclo[2.2.1.0^2,6]hept-1−yl)silanol derivative 9t. Eight-fold crystallization of the 9n/9x/9t-mixture gave pure sila-biperiden (racemate) in an overall yield of 5.3%, which represents a more than 30-fold improvement over the earlier synthesis.

Key Words:

• Sila-pharmaca
• Hydrosilylation
• Elimination of hydrogen bromide
• thermally and baseinduced