Patent ID: 8283472

Claim:
A synthetic esterification process comprising: (i) reacting (a) an amino acid of Formula I: wherein R a is a substituent at one or more of carbons 2, 3, 4, 5 and 6 of the phenyl ring, wherein the substituent is independently selected from the group consisting of hydrogen, alkyl, alkoxy, haloalkyl, haloalkoxy, hydroxyalkyl, alkoxyalkyl, halogen and —NR m R n , wherein R m and R n are independently selected from the group consisting of hydrogen, alkyl, haloalkyl and alkoxyalkyl; wherein R b is a substituent at one or more of carbons 7, 8, 9, 10 and 11 of the piperidine ring, wherein the substituent is independently selected from the group consisting of hydrogen, oxo, alkyl, alkoxy, haloalkyl, haloalkoxy, hydroxyalkyl, alkoxyalkyl and halogen; and wherein R c is selected from the group consisting of hydrogen, alkyl, haloalkyl, aralkyl, cycloalkylalkyl, hydroxyalkyl, alkoxyalkyl, and wherein R t is selected from the group consisting of alkyl, alkoxy, cycloalkyl, cycloalkylalkyl, aralalkoxy and aralkyl; with (b) an alcohol of formula R y —OH, wherein R y is selected from the group consisting of alkyl, haloalkyl, cycloalkyl, cycloalkylalkyl, aryl, aralkyl, heteroaryl, and heteroaralkyl; in the presence of (c) an acid; and (d) a water sequestrant to produce a reaction mixture containing an amino acid ester of Formula II and (ii) isolating the amino acid ester of Formula II or a pharmaceutically acceptable salt thereof.