Diastereoselective Synthesis of Methanopyridoxazocinones

Two approaches to the synthesis of oxygen-bridged tetrahydropyridones have been developed. In the first approach, substituted pyrido[4,3-<i>g</i>][1,3]oxazocines derivatives were prepared by diastereoselective one-pot reactions of substituted 7-azacoumarins with enolizable ketones and non-bulky primary amines. In the second one, 3-amido-7-azacoumarins were reacted with enolizable ketones in the presence of a base to form diastereomerically pure pyrido[4,3-<i>g</i>][1,3]oxazocines.