Patent ID: 7115769

Claim:
A method of preparing a 2-alkylcysteine derivative represented by Structural Formula (I): or a salt thereof, wherein R 1 is —NH 2 ; —N(R 5 )(R 6 ); —NHR 7 ; or —N═R 8 ; wherein R 5 , R 6 , R 7 , and R 8 are, independently, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, or a substituted or unsubstituted heterocyclic group; R 2 and R 3 are, independently, —H, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, or a substituted or unsubstituted heterocyclic group; and R 4 is a substituted or unsubstituted alkyl group; the method comprising, reacting, in the presence of a phase transfer catalyst, a cysteine derivative represented by Structural Formula (II): or a salt thereof, wherein R 1 , R 2 and R 3 are defined as above; with a compound having the formula R 4 -L, wherein R 4 is defined as above and L is a leaving group thereby forming the 2-alkylcysteine derivative represented by Structural Formula (I), wherein the phase transfer catalyst is a compound represented by Structural Formula (V): wherein R 9 is a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, or a substituted or unsubstituted heterocyclic group; R 10 and R 11 are, independently, —H, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aromatic group, or a substituted or unsubstituted heterocyclic group; and X is a halogen.