Peptide antibiotics

A composition comprising a pharmaceutically acceptable carrier and an antibiotic peptide or salt of an antibiotic peptide of formula:

• wherein:
• a, b, and c are independently selected integers, wherein a=1-5, b=2-6, and c=2-5;
• Y is selected from the group consisting of:
• H;
• OH;
• and, a linear, branched or cyclic, saturated or unsaturated alkyl of one to ten carbon atoms;
• LPAA is an amino acid residue having the structure —NX—CαR1—CO—, wherein for each LPAA in the peptide, R1 is selected from the group consisting of:
• hydrogen;
• a linear, branched or cyclic, saturated or unsaturated alkyl containing one to ten carbons atoms optionally substituted with —OH, —OR, —SH, —SR, —SOCR, —NHCOR, —I, —Br, —Cl, —F, —CN, —O2CR, —CO2R, —CHO, —COR, —CONH2, —CONHR, —CON(R)2, —COSR, —SOR, or —SO2R;
• benzyl, in which a phenyl ring of the benzyl is optionally substituted with R, —OH, —OR, —O2CR, —SH, —SR, —SOCR —NHCOR, —I, —Br, —Cl, —F, —CN, —CO2R, —CHO, —COR, —CONH2, —CONHR, —CON(R)2, —COSR, —NO2, —SOR, or —SO2R;
• and, arylalkyl in which an alkyl group of the arylalkyl has two to ten carbon atoms and is linear, branched or cyclic, saturated or unsaturated, optionally substituted with —OH, —OR, —O2CR, —SH, —SR, —SOCR, —NHCOR, —I, —Br, —Cl, —F, —CN, —CO2R, —CHO, —COR, —CONH2, —CONHR, —CON(R)2, —COSR, —NO2, —SOR or —SO2R, and in which an aryl ring of the arylalkyl is phenyl, or indole, optionally substituted with R, —OH, —OR, —O2CR, —SH, —SR, —SOCR, —NHCOR, —I, —Br, —Cl, —CN, —CO2R, —CHO, —COR, —CONH2, —CONHR, —CON(R)2, —COSR—NO2, —SOR, or —SO2R;
• wherein for R1, R in a substituent is a linear, branched or cyclic, saturated or unsaturated alkyl of one to ten carbon atoms, and providing that when R1 is joined to Cα by a single bond, H is also present joined to Cα;
• and, for each LPAA in the peptide, X is selected from the group consisting of:
• H;
• OH;
• and, a linear, branched or cyclic, saturated or unsaturated alkyl group containing one to ten carbons;
• BAA is an amino acid residue having the structure —NX—CHR2—CO—, wherein for each BAA in the peptide, R2 is selected from the group consisting of:
• a linear, branched or cyclic, saturated or unsaturated alkyl group of one to ten carbons, substituted with one of NH2, NRH, N(R)2, N(R)3+, —NH—CNH—NH2, or imidazole, and optionally additionally substituted with —OH, —OR, —SH, —SR, —SOCR, —NHCOR, —I, —Br, —Cl, —F, —CN, —CO2R, —CHO, —O2CR, —COR, —CONH2, —CONHR, —CON(R)2, —COSR, —SOR, or SO2R;
• benzyl in which a phenyl ring of the benzyl is substituted with one of NH2, NRH, N(R)2, or N(R)3+;
• and optionally additionally substituted with R, —OH, —OR, —O2CR, —SH, —SR, —SOCR, —NHCOR, —I, —Br, —Cl, —F, —CN, —CO2R, —CHO, —COR, —CONH2, —CONHR, —CON(R)2, —COSR, —NO2, —SOR, or —SO2R;
• arylalkyl in which an alkyl of the arylalkyl is linear, branched or cyclic, saturated or unsaturated of two to ten carbons, optionally additionally substituted with —OH, —OR, —O2CR, —SH, —SR, —SOCR, —NHCOR, —I, —Br, —Cl, —F, —CN, —CO2R, —CHO, —COR, —CONH2, —CONHR, —CON(R)2, —COSR, —NO2, —SOR, or —SO2, and in which an aryl ring of the arylalkyl is phenyl substituted with one of NH2, NRH, N(R)2, N(R)3+, indole substituted with one of NH2, NRH, N(R)2, N(R)3+, pyridine, or imidazole;
• and wherein the aryl ring is optionally additionally substituted with R, —OH, —OR, —O2CR, —SH, —SR, —SOCR, —NHCOR, —I, —Br, —Cl, —F, —CN, —CO2R, —CHO, —COR, —CONH2, —CONHR, —CON(R)2, —COSR, —NO2, —SOR, or —SO2R;
• wherein for R2, R in a substituent is a linear, branched or cyclic, saturated or unsaturated alkyl of one to ten carbon atoms and for each BAA in the peptide, X is selected from the group consisting of:
• H;
• OH;
• and a linear, branched or cyclic, saturated or unsaturated alkyl of one to ten carbons;
• and,
• R3 and R4═R1, and R3 and R4 are the same or different.