Production of monatin enantiomers

Abstract

Methods for preferentially hydrolyzing one stereoisomer of an isoxazoline diester over another, as well as an enzyme for facilitating the preferential hydrolysis are provided. Also provided are methods for providing mixtures of (RR) and (RS) monatin as well as (SS) and (SR) monatin, which methods can include the step of stereoselectively hydrolyzing an isoxazoline diester.

1 . A process comprising:
 stereoselectively hydrolyzing a compound of Formula II using Carboxyestrase NP enzyme:   
       
         
           
           
               
               
           
         
       
       wherein:
 R 1  and R 2  are independently C 1-10  alkyl; 
 
       to form at least one of a compound of Formula IIIa: 
       
         
           
           
               
               
           
         
       
       or a compound of Formula IIIa′ 
       
         
           
           
               
               
           
         
       
       and a compound of Formula IIb: 
       
         
           
           
               
               
           
         
       
     
     
         2 . The process of  claim 1 , wherein R 1  and R 2  are both ethyl. 
     
     
         3 . The process of  claim 1 , further comprising converting the compound of Formula IIIa or IIIa′ or both into a compound of Formula Ia: 
       
         
           
           
               
               
           
         
       
     
     
         4 . The process of  claim 3 , wherein said converting comprises:
 (a) hydrolyzing the compound of Formula IIIa or IIIa′ to form a compound of Formula IVa:   
       
         
           
           
               
               
           
         
       
       and
 (b) and hydrogenating the compound of Formula IVa. 
 
     
     
         5 . The process of  claim 4 , wherein said hydrogenating forms a mixture of a compound of Formula Ia and a compound of Formula Ic: 
       
         
           
           
               
               
           
         
         and the process, further comprises separating the compound of Formula Ia from the compound of Formula Ic. 
       
     
     
         6 . The process of  claim 1 , further comprising converting the compound of Formula IIb into a compound of Formula Ib: 
       
         
           
           
               
               
           
         
       
     
     
         7 . The process of  claim 6 , wherein said converting comprises:
 (a) hydrolyzing the compound of Formula IIb to form a compound of Formula IVb:   
       
         
           
           
               
               
           
         
         (b) and hydrogenating the compound of Formula IVb. 
       
     
     
         8 . The process of  claim 7 , wherein said hydrogenating forms a mixture of a compound of Formula Ib and a compound of Formula Id: 
       
         
           
           
               
               
           
         
         and the process further comprises separating the compound of Formula Ib from the compound of Formula Id. 
       
     
     
         9 . The process of  claim 5 , further comprising:
 (a) incorporating the compound of Formula Ia into a food composition.   
     
     
         10 . A process comprising: hydrolyzing an isoxazoline diester composition comprising a mixture of seteroisomers using carboxylesterase NP enzyme. 
     
     
         11 . A method for identifying enzymes useful in the production of steroisomerically-pure or stereisomerically-enriched monatin compositions, comprising: screening hydrolytic enzymes for steroselective hydrolytic activity on a isoxazoline diester, wherein the screening comprises selecting a hydrolytic enzyme, forming a reaction mixture comprising the selected enzyme and an isoxazoline diester, providing conditions under which a hydrolysis reaction of the isoxazoline diester is expected to proceed, and analyzing the reaction mixture for presence of stereoisomerically-pure or stereoisomerically-enriched monatin.