N‐acyl‐L‐leucines of biologically active uncommon fatty acids: Synthesis and antibacterial activity

The effect of structural variation in the fatty acid chain on the antibacterial activity ofN‐acyl‐L‐leucines was investigated. PureN‐acyl leucines of some structurally different and biologically active uncommon fatty acids were synthesized for the first time and tested for antimicrobial activity.N‐Stearoyl‐,N‐oleoyl‐ andN‐ricinoleoyl leucines were also evaluated for comparison. TheN‐acyl leucines exhibited greater activity in acid form than the methyl ester form and against gram positive bacteria than gram‐negative bacteria. The presence of a cyclopropane or a hydroxy group or unsaturation in the acyl chain increased the antibacterial activity. Shifting the hydroxyl group toward the amide linkage resulted in a diminished effect on the antibacterial activity.