A Novel, Antimicrobially Active Analog of Gramicidin S without Amphiphilic Conformation

A novel gramicidin S analog, cyclo(-Val-Leu-Leu-Orn-Leu- D -Phe-Pro-) 2 , was synthesized, its antibiotic activity compared with gramicidin S and shown to be as potent as gramicidin S when compared with the susceptibility toward five Gram-positive microorganisms. It exceeded the activity of gramicidin S against Bacillus megaterium ATCC 19213 by a factor of two. Circular dichroism and NMR data suggested this analog to adopt an antiparallel β-sheet conformation without amphiphilic character.