Dab

1. An antimicrobial compound according to structural formula (III):

or pharmaceutically acceptable salt thereof, wherein:

R 3 is independently selected from hydrogen, (C 1 –C 25 ) alkyl optionally substituted with one or more of the same or different R 15 groups, (C 1 –C 25 ) heteroalkyl optionally substituted with one or more of the same or different R 15 groups, (C 5 –C 10 ) aryl optionally substituted with one or more of the same or different R 15 groups, (C 5 –C 15 ) arylaryl optionally substituted with one or more of the same or different R 15 groups, (C 5 –C 15 ) biaryl optionally substituted with one or more of the same or different R 15 groups, 5–10 membered heteroaryl optionally substituted with one or more of the same or different R 15 groups, (C 6 –C 26 ) arylalkyl optionally substituted with one or more of the same or different R 15 groups, 6–26 membered heteroarylalkyl optionally substituted with one or more of the same or different R 15 groups, and a linear or branched, saturated or singly or multiply unsaturated alkyl or hydroxy alkyl having a chain of 6 to 22 carbon atoms;

R 4 is Asp or Asn;

R 6 is independently selected from at least one amino acid, a substituent comprising a primary or secondary amine, (C 1 –C 25 ) alkyl optionally substituted with one or more of the same or different R 15 groups, (C 1 –C 25 ) heteroalkyl optionally substituted with one or more of the same or different R 15 groups, (C 5 –C 10 ) aryl optionally substituted with one or more of the same or different R 15 groups, (C 5 –C 15 ) arylaryl optionally substituted with one or more of the same or different R 15 groups, (C 5 –C 15 ) biaryl optionally substituted with one or more of the same or different R 15 groups, 5–10 membered heteroaryl optionally substituted with one or more of the same or different R 15 groups, (C 6 –C 26 ) arylalkyl optionally substituted with one or more of the same or different R 15 groups, and 6–26 membered heteroarylalkyl optionally substituted with one or more of the same or different R 15 groups;

each R 15 is independently selected from —OR 16 , —SR 16 , NR 16 R 16 , —CN, —NO 2 , —N 3 , —C(O)OR 16 , —C(O)NR 16 R 16 , —C(S)NR 16 R 16 , —C(NR 16 )NR 16 R 16 , —CHO, —R 16 CO, —SO 2 R 16 , —SOR 16 , —PO(OR 16 ) 2 , —PO(OR 16 ), —CO 2 H, —SO 3 H, —PO 3 H, halogen, and trihalomethyl; and

each R 16 is independently selected from hydrogen, (C 1 –C 6 ) alkyl, (C 5 –C 10 ) aryl, 5–10 membered heteroaryl, (C 6 –C 16 ) arylalkyl, and 6–16 membered heteroarylalkyl.

2. The compound of claim 1 wherein R 4 is Asp.

3. The compound of claim 1 wherein R 4 is Asn.

4. The compound of claim 1 wherein R 3 is a linear saturated or singly unsaturated alkyl of 10 to 15 carbon atoms.

5. The compound of claim 1 wherein R 3 is a branched saturated or singly unsaturated alkyl of 10 to 15 carbon atoms.

6. The compound of claim 5 wherein the alkyl is in the iso or ante-iso configuration.

7. The compound of claim 1 wherein R 6 is at least one amino acid that is linked to the β-amino group of the macrocyclic Dab 9 residue via its carboxyl group, and wherein said at least one amino acid optionally includes a side chain moiety.

8. The compound of claim 1 in which R 6 has a —X—R 10 —NHR 7 or a —X—(CR 11 R 11 ) n —NHR 7 structure, wherein:

X is —C(O)—, —C(O)O—, —CO(NH)—, or —S(O) 2 —;

R 7 is hydrogen or (C 1 –C 4 ) alkyl;

R 10 is independently selected from —CH 2 —, —CH═CH—, —C≡C—, —O—, —S—, —NH—, —NH—NH—, —N═N—, —C(O)—, —S(O) 2 —, —S(O) 2 —O—, —C(NH)—, (C 1 –C 6 ) alkyldiyl, (C 1 –C 6 ) alkyleno, and (C 1 –C 6 ) alkano, wherein each R 10 is optionally substituted with —NR 8 R 8 , —OR 8 , —SR 8 , halogen, trihalomethyl, —CN, —C(O)R 8 , —C(O)OR 8 , —C(O)NR 8 R 8 , amidine, guanidine, alkyl optionally substituted with one or more of the same or different R 9 , aryl optionally substituted with one or more of the same or different R 9 , arylalkyl optionally substituted with one or more of the same or different R 9 , heteroalkyl optionally substituted with one or more of the same or different R 9 , and heteroarylalkyl optionally substituted with one or more of the same or different R 9 ;

each R 8 is independently selected from hydrogen, alkyl, aryl, arylalkyl, heteroaryl and heteroarylalkyl; and

each R 9 independently selected from —NR 8 R 8 , —OR 8 , —SR 8 , halogen, trihalomethyl, —CN, —C(O)R 8 , —C(O)OR 8 , —C(O)NR 8 R 8 , amidine, guanidine, alkyl, aryl, arylalkyl, heteroaryl, and heteroarylalkyl;

each R 11 is independently selected from hydrogen, amino, amido, amidino, carboxy, guandino, hydroxy, sulfanyl, (C 1 –C 4 ) alkyl, (C 1 –C 4 ) alkyl substituted with one or more of the same or different R 12 , (C 5 –C 10 ) aryl, (C 5 –C 10 ) aryl substituted with one or more of the same or different R 12 , (C 6 –C 13 ) arylalkyl, (C 6 –C 13 ) arylalkyl substituted with one or more of the same or different R 12 , 5–10 membered heteroaryl, 5–10 membered heteroaryl substituted with one or more of the same or different R 12 , 6–13 membered heteroarylalkyl, and 6–13 membered heteroarylalkyl substituted with one or more of the same or different R 12 ;

each R 12 is independently selected from amino, amido, amidino, carboxyl, guanidino, hydroxy, and sulfanyl; and

n is an integer from 1 to 6.

9. The compound of claim 8 wherein R 10 is independently selected from (C 1 –C 6 ) alkyldiyl, (C 1 –C 6 ) alkyleno, and (C 1 –C 6 ) alkano.

10. The compound of claim 8 wherein n is 1 and R 11 is a side-chain moiety of a genetically encoded amino acid.

11. The compound of claim 8 wherein n is 2 to 4 and only one R 11 is other than hydrogen.

12. The compound of claim 1 in which R 6 has a —X 1 —R 3 structure, wherein X 1 is selected from —CO—, —SO 2 , —CS—, —PO—, —OPO—, —OC(O)—, —NHCO—, and —NR 3 CO—.

13. The compound of claim 1 in which R 4 is attached to R 3 via a linker X 1 , wherein X 1 is selected from —CO—, —SO 2 , —CS—, —PO—, —OPO—, —OC(O)—, —NHCO—, and —NR 3 CO—.

14. The compound of claim 1 in which R 6 has a —X 1 —R 3 structure and in which R 4 is attached to R 3 via a linker X 1 , wherein X 1 is selected from —CO—, —SO 2 , —CS—, —PO—, —OPO—, —OC(O)—, —NHCO—, and —NR 3 CO—.

15. A pharmaceutical composition comprising at least one compound according to one of claims 1 , 8 , and 12 – 14 and a pharmaceutically acceptable carrier, excipient or diluent.

16. A method of inhibiting the growth of Gram-positive bacteria, comprising contacting the bacteria with a compound according to claim 1 in an amount effective to inhibit growth.

17. The method of claim 16 wherein the compound is provided in an amount effective to kill Gram-positive bacteria.

18. The method of claim 16 or 17 wherein the Gram-positive bacteria are selected from Streptococci species, Staphylococci species, or Enterococci species.

19. A method of treating or preventing an infection caused by or associated with Gram-positive bacteria, comprising administering to a subject in need thereof at least one compound according to any one of claims 1 , 8 , and 12 – 14 in an amount effective to treat or prevent an infection caused by or associated with Gram-positive bacteria.

20. The method of claim 19 wherein said at least one compound is administered topically or systemically.

21. The method of claim 19 wherein the Gram-positive bacteria are selected from Streptococci species, Staphylococci species, or Enterococci species.

22. A method of treating or preventing an infection caused by or associated with Gram-positive bacteria, comprising administering to a subject in need thereof a composition according to claim 15 in an amount effective to treat or prevent an infection caused by or associated with Gram-positive bacteria.

23. The method of claim 22 wherein the composition is administered topically or systemically.

24. The method of claim 23 wherein the composition administered topically is in the form of a gel, ointment, cream, or paste.

25. The method of claim 22 wherein the Gram-positive bacteria are selected from Streptococci species, Staphylococci species, or Enterococci species.