STEREOCHEMICAL STUDIES .30. SYNTHESIS AND CONFORMATIONAL-ANALYSIS OF DECA AND DODECA-HYDROPYRIDO[2,1-B]QUINAZOLIN-11-ONES

cis- and trans-Decahydro- and dodecahydro-pyrido[2,1-b]quinazolin-11-ones have been synthesized and their preferred conformations established by 1H n.m.r. spectroscopy. At room temperature the A and B rings of the cis-decahydro derivatives are conformationally mobile, while the t-butyl derivatives have fixed conformations. The predominant conformation of the cis-dodecahydro-derivatives is that in which the C=O group is equatorial, the N atom is axial, and the configuration of the nitrogen bridgehead B/C fusion is trans.