Synthetic studies on virantmycin .1. Total synthesis of (+/-)-virantmycin and determination of its relative stereochemistry

The efficient and stereospecific route to the tetrahydroquinoline ring models 3 and 4 of virantmycin has been developed by means of an intramolecular nitrene addition reaction as a key step. In the NOE experiments of 4 and 3 we revealed that a ring inversion occurs in their piperidine ring system and determined the relative stereochemistry by capturing each half-chair conformer as cyclic carbamates 26 and 27, respectively. Utilizing this protocol total syntheses of (+/-)-1 and its diastereomer (+/-)-2 have been accomplished and the relative stereochemistry of virantmycin has been established as shorn in 1. Copyright (C) 1996 Elsevier Science Ltd