Biological Specificities of 4,5-Dehydro Analogues of Isoleucine and Alloisoleucine

The synthesis of 2-amino-3-methyl-4-pentynoic acid with a configuration corresponding to alloisoleucine has been reported (4), and a partial hydrogenation of this compound would afford a method of obtaining w-dehydroalloisoleucine. However, in the method of synthesis of 2-amino-3-methyl-4-pentynoic acid herein reported, a mixture of both of the diastereoisomeric forms of the acetylenic derivatives was obtained. Subsequent fractional recrystallization of the mixture separated the isomers into the two racemic forms. Partial hydrogenation of the appropriate triple bond compound produced either w-dehydroisoleucine or w-dehydroalloisoleucine, and complete hydrogenation yielded the anticipated nn-isoleucine or nn-alloisoleucine. The ethylenic analogues are more effective growth inhibitors than the acetylenic deriviatives for Escherichia coli, but for Lactobacillus arabinosus the relative inhibitory activity depends upon whether the antagonism of isoleucine or of valine is being determined. Under appropriate conditions, antagonism of both isoleucine and valine by these analogues can be demonstrated with both organisms.