No abstract

A diastereoisomeric mixture of racemic β-methylleucine was synthesized by the condensation of 2-benzyl-4(5H)-imidazolone with the methyl isopropyl ketone, followed by catalytic hydrogenation and hydrolysis. The separation of the mixture into threo-β-methyl-Dl-leucine and erythro-β-methyl-Dl-leucine was mainly achieved by fractional crystallization from water. The resolution of each diastereoisomer was also accomplished through salt-formation with (−)- and (+)-ephedrine alternately before or after the methylation of the amino group. The specific rotation and the NMR and IR spectra of one isomer, threo-N,β-dimethyl-l-leucine, corresponded closely with those reported for dimethylleucine isolated from nature.

No abstract

β-Methylnorleucine and β-methylleucine were synthesized, separated into diastereomers and optically resolved. The configurational assignments of these isomers and the determinations of the optically active isomers were achieved by means of NMR spectroscopy and the enzymatic method respectively.

No abstract