Process for the preparation of (3R)-hydroxybutyl (3R)-hydroxybutyrate by enzymatic enantioselective reduction employing Lactobacillus brevis alcohol dehydrogenase
Inventors
Robertson, Jeremy • Clarke, Kieran • Veech, Richard Lewis
Assignees
Oxford University Innovation Ltd • US Department of Health and Human Services
Publication Number
US-9034613-B2
Publication Date
2015-05-19
Expiration Date
2029-04-16
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Abstract
A process for producing a compound which is (3R)-hydroxybutyl (3R)-hydroxybutyrate of formula (I) which process comprises submitting, to enantioselective reduction, a compound of the following formula (II), (III) or (IV).
Core Innovation
The invention relates to a process for producing (3R)-hydroxybutyl (3R)-hydroxybutyrate in enantiomerically enriched form by submitting compounds of specific formulas to enantioselective reduction. This process involves distinct synthetic routes to prepare compounds of formula (II), (III), or (IV), which are then enantioselectively reduced to the target compound (formula (I)). The preparation can involve treating 4-hydroxybutan-2-one or (R)-1,3-butanediol with diketene, 2,2,6-trimethyl-4H-1,3-dioxin-4-one, or (R)-4-methyloxetan-2-one under various conditions.
The enantioselective reduction can be mediated by enzymes such as ketoreductases or alcohol dehydrogenases, with a preference for enzymes that exhibit R-enantiomer selectivity and high activity, including the alcohol dehydrogenase from Lactobacillus brevis (ADH-LB). The process also allows for chemical asymmetric reduction alternatives. The enzymatic reduction is typically conducted under mild conditions using cofactors and cofactor recycling systems to achieve high enantiomeric purity, often exceeding 95% enrichment in the (3R,3′R) isomer.
The problem addressed by this invention arises from previous methods for synthesizing 3-hydroxybutyl 3-hydroxybutyrate, which typically yield mixtures of four stereoisomers and suffer from limitations such as low yields, impure products, many chemical steps, or impracticability at manufacturing scales. There was a need for a convenient, scalable process that produces the (3R,3′R) isomer in high enantiomeric purity suitable for clinical applications and large-scale production.
Claims Coverage
The claims include multiple independent claims that cover processes for producing (3R)-hydroxybutyl (3R)-hydroxybutyrate by enantioselective reduction, with further independent claims detailing methods of producing intermediate compounds through specific reactions and conditions. The main inventive features relate to synthetic routes, the enantioselective enzymatic reduction, and process conditions.
Process for producing (3R)-hydroxybutyl (3R)-hydroxybutyrate by enantioselective reduction
A process comprising submitting compounds of formula (II), (III), or (IV) to enantioselective reduction to produce (3R)-hydroxybutyl (3R)-hydroxybutyrate of formula (I).
Preparation of intermediate compounds from specific starting materials
Processes for producing compounds of formula (II), (III), or (IV) by treating 4-hydroxybutan-2-one or (R)-1,3-butanediol with diketene, 2,2,6-trimethyl-4H-1,3-dioxin-4-one in the presence of transesterification reagents, compounds of formula (X), or (R)-4-methyloxetan-2-one, under esterification or transesterification conditions.
Enzymatic enantioselective reduction using specific enzymes
Carrying out the enantioselective reduction step using an enzyme, specifically ketoreductases or alcohol dehydrogenases, notably the alcohol dehydrogenase from Lactobacillus brevis (ADH-LB).
Conducting enantioselective reduction at mildly acidic pH
Maintaining the pH during the reduction step below 7.0 but at least 4.0, preferably between 5.0 and 6.0, to improve reaction performance and stability of reactants.
Alternative chemical asymmetric reduction processes
Carrying out the enantioselective reduction using chemical asymmetric reduction methods, including asymmetric hydride transfer reduction, hydrogenation, or hydrosilylation with chiral catalysts.
The patent claims extensively cover the synthetic preparation of key intermediate compounds and their subsequent enantioselective reduction by enzymatic or chemical means under controlled conditions to yield (3R)-hydroxybutyl (3R)-hydroxybutyrate with high enantiomeric purity, emphasizing scalable and practical process improvements.
Stated Advantages
Convenience, scalability, and non-toxicity of the enzymatic reduction process which is environmentally non-hazardous.
Capability to perform the enantioselective reduction at high reactant concentrations with better pH control, improving yields and reaction cleanliness.
Production of (3R)-hydroxybutyl (3R)-hydroxybutyrate in enantiomerically enriched form with at least 95% to 99% purity of the desired (3R,3′R) isomer.
Use of commercially available enzymes and cofactors facilitates practical and economical implementation on a manufacturing scale.
Documented Applications
The (3R)-hydroxybutyl (3R)-hydroxybutyrate compound produced is useful as a food additive that boosts ketone body levels in blood, leading to enhanced physical and cognitive performance.
Formulation of the produced compound into food products composed of macronutrients and micronutrients for clinical or dietary benefits.
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