Process for producing (r)-3-hydroxybutyl (r)-3-hydroxybutyrate

Abstract

Embodiments of the present invention are directed to processes for the production of (R)-3-hydroxybutyl (R)-3-hydroxybyrate. Poly (R)-3-hydroxybyrate is transesterified with an alcohol, to form a first ester portion and a second ester portion. The first ester portion is reduced to the diol to form a diol portion and the diol portion is reacted with the second ester portion to produce (R)-3-hydroxybutyl (R)-3-hydroxybyrate.

1 . A process for the production of (R)-3-hydroxybutyl (R)-3-hydroxybutyrate comprising:
 (i) contacting poly-(R)-3-hydroxybutyrate with an alcohol to transesterify the poly-(R)-3-hydroxybutyrate under transesterification conditions to produce an ester of (R)-3-hydroxybutyrate and the alcohol;   (ii) separating the product of step i) into a first and second portion and reducing the first portion of the (R) 3-hydroxybutyrate ester to form (R)-1,3-butanediol;   (iii) contacting under transesterification conditions the (R)-1,3-butanediol from step ii) with the second portion of the transesterified ester to produce (R)-3-hydroxybutyl-(R)-hydroxybutanoate.   
     
     
         2 . A process according to  claim 1  wherein the poly-(R)-3-hydroxybutyrate is obtained from corn starch or sugar cane. 
     
     
         3 . A process according to  claim 1  wherein the poly-(R)-3-hydroxybutyrate is transesterified in step i) using ethanol. 
     
     
         4 . A process according to  claim 1  wherein the weight ratio of alcohol to poly-(R)-3-hydroxybutyrate is from 1:1 to 10:1. 
     
     
         5 . A process according to  claim 1  wherein the step i) is carried out in acidic conditions. 
     
     
         6 . A process according to  claim 1  wherein the product of step i) is treated to neutralise the acid, remove the alcohol by distillation. 
     
     
         7 . A process according to  claim 6  wherein the distillation is carried out at a temperature of 110° C. to 150° C. 
     
     
         8 . A process according to  claim 1  wherein the reduction in step ii) comprises reducing (R)-3-hydroxybutyrate ester using a hydride transfer reagent. 
     
     
         9 . A process according to  claim 8  wherein the reducing agent is selected from lithium aluminium hydride, sodium bis (2-methoxyethoxy) aluminium hydride, sodium borohydride, nickel borohydride.