Stereocontrolled Synthesis of Pyridooxazinones and Pyridodiazepinones

Significance

Diastereomeric pipecolates 3 and 7 can be obtained from either syn-1 or anti-1. The stereochemical complexity was increased further by subjecting 3 and 7 to the reaction with chiral epoxides (R)-4 or (S)-4 bearing various substituents. Thus, a number of diastereomeric pyrido­oxazidinones 5, 6, 8 or 9 can be synthesized in six or seven steps, with all stereocenters well defined. The azido analogs of 5, 6, 8 and 9 were shown to undergo a Staudinger-reductive amination-transesterification sequence to yield the pyridodiazepinones 10 .