Stereospecific synthesis of tabtoxin

Abstract

Tabtoxin (1), the exotoxin fromPseudmonas tabaci (the organism responsible for Wildfire disease of tobacco plants), has been synthesised by a stereospecific route. The cycloaddition of an acylnitroso compound to a cyclohexadiene proceeded regioselectively to give the bicyclic ester (6), which was transformed to the amine (24) through reductive amination of the aldehyde (10). Oxidative cleavage of the olefin (25) gave the corresponding diacid (26), whose functional groups were appropriately differentiated by formation of the peptide (29). Cyclisation of the β-amino acid (30) and subsequent hydrogenolysis of the resulting spiro β-lactam (31) gave tabtoxin.