Development of des-fatty acyl-polymyxin B decapeptide analogs with Pseudomonas aeruginosa-specific antimicrobial activity.

Twelve N-terminal analogs of des-fatty acyl-polymyxin B (Des-FA-[X(1)]-PMB, X=various amino acids or peptides) were synthesized and examined for their antimicrobial activity against Escherichia coli (E. coli), Salmonella Typhimurium (S. Typhimurium) and Pseudomonas aeruginosa (P.

Semi-synthesis of polymyxin B (2-10) and colistin (2-10) analogs employing the Trichloroethoxycarbonyl (Troc) group for side chain protection of alpha,gamma-diaminobutyric acid residues.

Improved strategies for the chemical conversion of natural polymyxin B and colistin to their N-terminal analogs are reported. First, the protection of the side chains of five L-alpha,gamma-diaminobutyric acid (Dab) residues in natural polymyxin B and colistin was achieved with trichloroethoxycarbonyl (Troc), then the resulting pentakis(N gamma-Troc)-polymyxin B and pentakis(N gamma)Troc)-colistin were treated with trifluoroacetic acid (TFA) : methanesulfonic acid (MSA) : dimethylformamide (DMF) : H2O (10 : 30 : 55 : 5) at 40 degrees C in order to remove N alpha-alkanoyl-Dab(Troc)-OH selectively. The new key compounds, tetrakis(N gamma-Troc)-polymyxin B (2-10) and tetrakis(N gamma-Troc)-colistin (2-10), were obtained in 19% and 15% yields, respectively, which is higher than previous reports using trifluoroacetyl (Tfa) for tetrakis(N gamma-Tfa)-polymyxin B (2-10) and tetrakis(N gamma-Tfa)-colistin (2-10), respectively.