An improved synthesis of (2S, 4S)- and (2S, 4R)-2-amino-4-methyldecanoic acids: assignment of the stereochemistry of culicinins.

An improved synthesis of (2S, 4S)- and (2S, 4R)-2-amino-4-methyldecanoic acids was accomplished using a glutamate derivative as starting material and Evans' asymmetric alkylation as the decisive step. The NMR data of the two diastereomers were measured and compared with those of the natural product. As a result, the stereochemistry of this novel amino acid unit in culicinins was assigned as (2S, 4R).