Patent ID: 7635750

Claim:
A method for preparing a peptide comprising a peptidic backbone made up of four or more amino acids; wherein the method comprises a step of: reacting a peptide acyl donor comprising a peptidic backbone made up of two or more amino acids wherein said peptide acyl donor has the structure: with a peptide amine acceptor having the structure: under reducing reaction conditions employing an excess of a reducing agent; wherein k1 and k2 are independently integers between 1 and about 20; each occurrence of A 1 and A 2 is independently an aliphatic, heteroaliphatic, aromatic, heteroaromatic, aryl, heteroaryl group; R S1 is a sulfide protecting group; R is aliphatic, heteroaliphatic, aromatic or heteroaromatic; each occurrence of L 1 is independently substituted or unsubstituted, linear or branched, cyclic or acyclic, saturated or unsaturated aliphatic or heteroaliphatic; R X1 is hydrogen, alkyl, acyl, aromatic, heteroaromatic, aryl, heteroaryl, -alkyl(aryl), -alkyl(heteroaryl), a nitrogen protecting group, an amino acid or a proctected amino acid; and R X2 is —OR X2a or —NR X2b R X2c , wherein R X2a is hydrogen, alkyl, aromatic, heteroaromatic, aryl, heteroaryl, -alkyl(aryl), -alkyl(heteroaryl), a carboxylic acid protecting group, an amino acid or a proctected amino acid; and R X2b and R X2c are independently hydrogen, alkyl, aromatic, heteroaromatic, aryl, heteroaryl, -alkyl(aryl), -alkyl(heteroaryl), a nitrogen protecting group, an amino acid or a proctected amino acid.