Chemical linkers with single amino acids and conjugates thereof

1. A single α-amino acid compound of the formula

wherein

AA 1 is a single α-amino acid selected from the group consisting of Cit and Lys;

L 3 is substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted heterocycloalkyl;

o is 0 or 1;

X 4 -(L 4 ) p is

P is 1;

and

D comprises a structure:

wherein X is a member selected from O, S and NR 23 ;

Z is NR 23 ;

R 23 is H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, acyl;

R 1 is H substituted or unsubstituted lower alkyl, C(O)R 8 , or CO 2 R 8 , wherein R 8 is a member selected from NR 9 R 10 and OR 9 ,

in which R 9 and R 10 are members independently selected from H, substituted and unsubstituted alkyl and substituted and unsubstituted heteroalkyl;

R 1′ is H, substituted or unsubstituted lower alkyl, or C(O)R 8 is a member selected from NR 9 R 10 and OR 9 ,

in which R 9 and R 10 are members independently selected from H, substituted and unsubstituted alkyl and substituted and unsubstituted heteroalkyl;

R 2 is H, substituted or unsubstituted lower alkyl, unsubstituted heteroalkyl, cyano or alkoxy;

R 2′ is H, substituted or unsubstituted lower alkyl or unsubstituted heteroalkyl;

R 3 is OR 11 ,

wherein R 11 is H, substituted alkyl, unsubstituted alkyl, substituted heteroalkyl, unsubstituted heteroalkyl, diphosphate, triphosphate, acyl, C(O)R 12 R 13 , C(O)OR 12 , C(O)NR 12 R 13 , P(O)(OR 12 ) 2 , C(O)CHR 12 R 13 , SR 12 , or SiR 12 R 13 R 14 ,

in which R 12 , R 13 , and R 14 are members independently selected from H, substituted and unsubstituted alkyl, substituted and unsubstituted heteroalkyl and substituted and unsubstituted aryl, wherein R 12 and R 13 together with the nitrogen or carbon atom to which they are attached are optionally joined to form a substituted or unsubstituted heterocycloalkyl ring system having from 4 to 6 members, optionally containing two or more heteroatoms;

R 4 , R 4′ , R 5 and R 5′ , are members independently selected from the group consisting of H, substituted alkyl, unsubstituted alkyl, substituted aryl, unsubstituted aryl, substituted heteroaryl, unsubstituted heteroaryl, substituted heterocycloalkyl, unsubstituted heterocycloalkyl, halogen, NO 2 , SO 3 , SO 2 R 15 , NR 15 R 16 , NR 16 C(O)R 15 , OC(O)NR 15 R 16 , OC(O)OR 15 , C(O)R 15 , SR 15 , OR 15 , CR 15 ═NR 16 , and O(CH 2 ) n N(CH 3 ) 2 ;

wherein

n is an integer from 1 to 20;

R 15 and R 16 are independently selected from H, substituted and unsubstituted alkyl, substituted and unsubstituted heteroalkyl, substituted and unsubstituted aryl, substituted and unsubstituted heteroaryl, substituted and unsubstituted heterocycloalkyl, and substituted and unsubstituted peptidyl, wherein R 15 and R 16 together with the nitrogen atom to which they are attached are optionally joined to form a substituted or unsubstituted heterocycloalkyl ring system having from 4 to 6 menibers, optionally containing two or more heteroatoms;

R 6 is a single bond which is either present or absent and when present R 6 and R 7 are joined to form a cyclopropyl ring; and

R 7 is CH 2 —X 1 or —CH 2 — joined in said cyclopropyl ring with R 6 , wherein

X 1 is a leaving group,

wherein at least one of R 4 , R 4′ , R 5 , R 5′ , R 11 , R 12 , R 13 , R 15 or R 16 links D to the remainder of the compound; and

wherein the compound is a single α-amino acid compound,

or a pharmaceutically acceptable salt thereof.

2. The compound of claim 1 , wherein at least one of R 4 , R 4′ , R 5 , R 5′ , R 15 or R 16 links D to the remainder of the compound.

3. The compound of claim 1 , wherein L 3 is present and -L 3 -NH— is selected from

wherein

Z is a member selected from O, S and NR 23

wherein

R 23 is H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, or acyl.

4. The compound of claim 3 , wherein -L 3 -NH— is

5. The compound of claim 1 , wherein the compound is selected from

wherein X 1 is Cl or Br.

6. The compound of claim 5 , wherein X 1 is Cl,

7. A pharmaceutical formulation comprising a compound according to claim 1 and a pharmaceutically acceptable carrier.