A compound of formula or a pharmaceutically acceptable salt thereof, wherein: A is selected from; wherein: denotes the point of attachment to the carbonyl group and denotes the point of attachment to the nitrogen atom; n is 0, 1, or 2; m is 1 or 2; p is 0, 1, or 2; R 14 and R 15 are independently selected from hydrogen and methyl; R z is selected from hydrogen and -C NHR 16; wherein R 16 is selected from hydrogen, -CHR 17 C NH 2, -CHR 17 C NHCHR 18 C NH 2, and -CHR 17 C NHCHR 18 C NHCH 2 C NH 2; wherein R 17 is selected from hydrogen and -CH 2 OH and wherein R 18 is selected from hydrogen and methyl; R v is hydrogen, methyl, or a natural amino acid side chain; R c, R f, R h, R i, and R m are hydrogen; R n is hydrogen or methyl or R v and R n form a pyrrolidine ring; R a, R e, and R j, are each independently selected from hydrogen and methyl; R k is methyl; R 1, R 2, R 3, R 5, R 6, R 8, R 9, R 10, R 11, R 12, and R 13 are independently selected from a natural amino acid side chain and an unnatural amino acid side chain or R 2 or R 12 form a ring with the corresponding vicinal R group as described below; R b is methyl or, R b and R 2, together with the atoms to which they are attached, form a ring selected from azetidine, pyrrolidine, morpholine, piperidine, piperazine, and tetrahydrothiazole; wherein each ring is optionally substituted with one to four groups independently selected from amino, cyano, methyl, halo, and hydroxy; R d and R 4, together with the atoms to which they are attached, form a pyrrolidine ring; R g and R 7, together with the atoms to which they are attached, form a pyrrolidine ring which is optionally substituted with one hydroxyl group; and R L is methyl or, R L and R 12, together with the atoms to which they are attached, form a ring selected from azetidine and pyrrolidine, wherein each ring is optionally substituted with one to four groups independently selected from amino, cyano, methyl, halo, and hydroxy. A is selected from; wherein: denotes the point of attachment to the carbonyl group and denotes the point of attachment to the nitrogen atom; n is 0, 1, or 2; m is 1 or 2; p is 0, 1, or 2; R 14 and R 15 are independently selected from hydrogen and methyl; R z is selected from hydrogen and -C NHR 16; wherein R 16 is selected from hydrogen, -CHR 17 C NH 2, -CHR 17 C NHCHR 18 C NH 2, and -CHR 17 C NHCHR 18 C NHCH 2 C NH 2; wherein R 17 is selected from hydrogen and -CH 2 OH and wherein R 18 is selected from hydrogen and methyl; R v is hydrogen, methyl, or a natural amino acid side chain; denotes the point of attachment to the carbonyl group and denotes the point of attachment to the nitrogen atom; n is 0, 1, or 2; m is 1 or 2; p is 0, 1, or 2; R 14 and R 15 are independently selected from hydrogen and methyl; R z is selected from hydrogen and -C NHR 16; wherein R 16 is selected from hydrogen, -CHR 17 C NH 2, -CHR 17 C NHCHR 18 C NH 2, and -CHR 17 C NHCHR 18 C NHCH 2 C NH 2; wherein R 17 is selected from hydrogen and -CH 2 OH and wherein R 18 is selected from hydrogen and methyl; R v is hydrogen, methyl, or a natural amino acid side chain; R c, R f, R h, R i, and R m are hydrogen; R n is hydrogen or methyl or R v and R n form a pyrrolidine ring; R a, R e, and R j, are each independently selected from hydrogen and methyl; R k is methyl; R 1, R 2, R 3, R 5, R 6, R 8, R 9, R 10, R 11, R 12, and R 13 are independently selected from a natural amino acid side chain and an unnatural amino acid side chain or R 2 or R 12 form a ring with the corresponding vicinal R group as described below; R b is methyl or, R b and R 2, together with the atoms to which they are attached, form a ring selected from azetidine, pyrrolidine, morpholine, piperidine, piperazine, and tetrahydrothiazole; wherein each ring is optionally substituted with one to four groups independently selected from amino, cyano, methyl, halo, and hydroxy; R d and R 4, together with the atoms to which they are attached, form a pyrrolidine ring; R g and R 7, together with the atoms to which they are attached, form a pyrrolidine ring which is optionally substituted with one hydroxyl group; and R L is methyl or, R L and R 12, together with the atoms to which they are attached, form a ring selected from azetidine and pyrrolidine, wherein each ring is optionally substituted with one to four groups independently selected from amino, cyano, methyl, halo, and hydroxy.