Stereochemical studies. Part 50. Saturated heterocycles. Part 29. Synthesis and X-ray analysis of stereoisomeric dodecahydropyrido[2,1 -b]quinazolin-11-ones

Abstract

Reductions of cis- and trans-decahydropyrido[2,1-b]quinazolin-11-ones (4), (3) and their quaternary salts (10), (9), prepared by means of dimethyl sulphate, have been investigated. Stereospecific or stereoselective formation of the unsubstituted tricycles was found, whereas the 5-methylperhydropyrido[2,1-b]quinazolines were formed stereospecifically only in the case of the trans-derivatives. The relative configurations of the 5-methyl compounds were established by means of configurative correlation, and the steric structures of the r-4a, c-5a,t-11a- and r-4a,c-6a,c-11a-dodecahydropyrido[2,1 -b]quinazolin 11 -ones (5a) and (7a), respectively, were determined by X-ray diffraction analysis.