Crystal Structure and Herbicidal Activity of N-Benzylbutanamides and Their Optical Isomers

Herbicidal Activity of N-Benzylbutanamides (Part 5)

Abstract

Optically active N-benzylbutanamides were prepared and their herbicidal activity against Scirpus juncoides and Echinochloa crus-galli was determined by the vial test. The crystal structure of N-(1′-methyl-1′-phenylethyl)-2-bromo-3, 3-dimethylbutanamide (S-47) and (2R, 1′S)-(-)-N-(1′-phenylethyl)-2-bromo-3, 3-dimethylbutanamide (S-44) was shown to have smooth shape by X-ray analysis and the absolute configuration of (-)-2-bromo-3, 3-dimethylbutanoic acid has been assigned as R. The activity of the (R)-(+)-isomer of S-47 was about 10 times higher than that of the (S)-(-)-isomer against a sensitive plant, S. juncoides, but the difference in the activity against a less sensitive plant, E. crus-galli, was only slight. The R-configuration at the acid moiety and the S-configuration at the amine moiety of S-44 were essential to the high activity.