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 of N ‐acyl‐L‐leucines was investigated. Pure N ‐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‐ and N ‐ricinoleoyl leucines were also evaluated for comparison. The N ‐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.