CRYSTAL AND MOLECULAR-STRUCTURE OF A RIMAZOLIUM(R) DECOMPOSITION PRODUCT - CALCULATION OF PYRAMIDALITY OF ANALOGOUS CYCLIC AMIDES

The solid state structure of 10 was determined by X-Ray investigations , and stereostructure of 1,6,7,8,9,9a-hexahydro-4H-pyrido [1,2-a]pyrim idin-4-ones were studied by semiempirical quantum chemical calculation s at the AM1 level. While 9a-unsubstituted ,8,9,9a-hexahydro-4H-pyrido [1,2-a]pyrimidin-4-ones adopt a cis-fused conformation, 9a-ethoxy-1-me thyl derivative has a trans-fused conformation to avoid a serious non- bonding interaction between 9a-ethoxy and 1-methyl groups in cis-fused one.