Patent ID: 8592419

Claim:
A compound of formula: and pharmaceutically acceptable salts thereof, wherein: R 1 is —SH, —NH 2 , —Cl, —Br, —I, —C(O)OH, —C(O)NH 2 , —NH(C═NH)NH 2 , —NH(R 2 ), or —N-heterocycle having from 5 to 6 atoms in the ring; R 2 is —H or —(C 1 -C 6 )alkyl; R 3 is -phenyl optionally substituted with one or more —R 5 ; R 4 is —(C 1 -C 6 )alkyl, —SH, —NH 2 , —CH 2 Cl, —CH 2 Br, —CH 2 I, —C(O)OH, or —C(O)NH 2 ; R 5 is —(C 1 -C 6 )alkyl, —F, —Cl, —Br, —I, —NH(R 2a ), —NO 2 , or an amide of formula R 2a is —H or —(C 1 -C 6 )alkyl; X is —CH 2 —, —CH((C 1 -C 6 )alkyl)—, or —C(S)-; Y is —CH 2 —, —C(O)—, —N(H)—, or —O—; A is —CH(OH)—; a is 0 or 1; b is 1; n is an integer from 8 to 22; and A − is a pharmaceutically acceptable counter-anion.