141942-85-0

Basic information

• Product Name: Ethyl (R)-(-)-4-cyano-3-hydroxybutyate
• Synonyms: (R)-(-)-4-CYANO-3-HYDROXYBUTYRIC ACID ETHYL ESTER;(R)-4-CYANO-3-HYDROXYBUTYRIC ACID ETHYL ESTER;(R)-(-)-ETHYL 4-CYANO-3-HYDROXYBUTYRATE;(R)-ETHYL 4-CYANO-3-HYDROXYBUTYRATE;(S)-4-CYANO-3-HYDROXYBUTANOATE ETHYL;ETHYL (3R)-4-CYANO-3-HYDROXY-BUTANOATE;ETHYL (S)-4-CYANO-3-HYDROXYBUTANOATE;ETHYL (R)-4-CYANO-3-HYDROXYBUTANOATE
• CAS NO: 141942-85-0
• Molecular Formula: C₇H₁₁NO₃
• Molecular Weight: 157.17
• EINECS: 430-220-6
• Product Categories: Pharmaceutical Intermediates;Alcohols, Hydroxy Esters and Derivatives;Chiral Compounds;INTERMEDIATESOFATORVASTATIN;chiral;API intermediates;Atorvastatin intermediates
• Mol File: 141942-85-0.mol
• Article Data: 31

Chemical Properties

• Boiling Point: 270 °C(lit.)
• Flash Point: >230 °F
• Appearance: Colorless to yellow/Liquid
• Density: 1.114 g/mL at 25 °C(lit.)
• Vapor Pressure: 1.75E-05mmHg at 25°C
• Refractive Index: n20/D 1.448(lit.)
• Storage Temp.: 2-8°C
• Solubility: Chloroform (Sparingly), DMSO (Slightly), Methanol (Slightly)
• PKA: 13.03±0.20(Predicted)
• BRN: 5328715
• CAS DataBase Reference: Ethyl (R)-(-)-4-cyano-3-hydroxybutyate(CAS DataBase Reference)
• NIST Chemistry Reference: Ethyl (R)-(-)-4-cyano-3-hydroxybutyate(141942-85-0)
• EPA Substance Registry System: Ethyl (R)-(-)-4-cyano-3-hydroxybutyate(141942-85-0)

Safety Data

• Hazard Codes: Xi
• Statements: 36/37/38
• Safety Statements: 26-36
• WGK Germany: 1
• Hazardous Substances Data: 141942-85-0(Hazardous Substances Data)

Usage

Chemical Properties

yellow liquid

Uses

Different sources of media describe the Uses of 141942-85-0 differently. You can refer to the following data:
1. Atorvastatin Intermediate
2. analgesic, antipyretic, and anti-inflammatory
3. (3R)-4-Cyano-3-hydroxybutanoic Acid Ethyl Ester is used in a biocatalytic process for the synthesis of an atorvastatin intermediate and degredation products/impurities.

Application

Hydroxyglutaryl coenzyme A (HMG-CoA) reductase inhibitors are a new class of lipid-lowering drugs, and they have a market share of more than 10 billion US dollars in the current pharmaceutical field. They can selectively inhibit the rate-limiting enzyme HMG-CoA reductase in cholesterol synthesis in the liver, reduce liver lipoprotein production, and increase the expression of low-density lipoprotein (LDL) cholesterol receptors, thereby reducing plasma cholesterol levels. They can also significantly reduce very low-density lipoprotein (VLDL) and triglycerides, and increase anti-atherosclerotic high-density protein (HDL), preventing atherosclerosis and coronary heart disease. Ethyl (R)-(-)-4-cyano-3-hydroxybutyate is an important intermediate for the synthesis of HMG-CoA reductase inhibitors. If it is used as a raw material, synthetic atorvastatin is mainly used for the treatment of hypercholesterolemia and mixed hyperlipidemia, coronary heart disease and stroke.

InChI:InChI=1/C7H11NO3/c1-2-11-7(10)5-6(9)3-4-8/h6,9H,2-3,5H2,1H3/t6-/m1/s1

Synthetic route

ethyl (2-chloroaceto)acetate (638-07-3) + sodium cyanide (143-33-9) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With glucose dehydrogenase; ketoreductase In acetic acid butyl ester; water at 30 - 40℃; for 16h; Product distribution / selectivity; Aqueous phosphate buffer;	98%

sodium cyanide (143-33-9) + (S)-4-bromo-3-hydroxy-butyric acid ethyl ester (32224-01-4, 95310-94-4, 128052-98-2, 95537-36-3) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
at 50℃; for 3h;	95%
In N,N-dimethyl-formamide at 20℃;	50%

sodium cyanide (773837-37-9) + ethyl (S)-4-chloro-3-hydroxybutanoate (10488-69-4, 86728-85-0, 87068-18-6, 90866-33-4) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With sulfuric acid; sodium hydroxide In water at 40℃; pH=7.3; Enzymatic reaction;	93%
With halohydrindehalogenase from parvibaculum lavamentivorans at 40℃; for 14h; pH=8; Kinetics; Enzymatic reaction;	85%
In water; N,N-dimethyl-formamide at 50℃; for 3h;	70%

(R)-3-hydroxy-4-cyano-butyric acid (287955-93-5) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With sulfuric acid In ethanol	90%

cyanoacetoacetic acid ethyl ester (1715-68-0) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With D-glucose In phosphate buffer at 30℃; for 24h; pH=7;	83.1%

sodium cyanide (143-33-9) + (S)-4-iodo-3-hydroxy-butyric acid ethyl ester (112100-39-7) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
In ethanol; water at 45℃; for 3h;	81%

(S)-4-bromo-3-hydroxybutyric acid,ethyl ester (32224-01-4) + sodium cyanide (143-33-9) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
In water at 25 - 35℃; for 7.33h; pH=8 - 9.5;	80%

sodium cyanide (143-33-9) + ethyl (S)-4-chloro-3-hydroxybutanoate (10488-69-4, 86728-85-0, 87068-18-6, 90866-33-4) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With acetic acid In water at 105 - 110℃; for 0.02125h;	80%
With sodium dihydrogen phosphate monohydrate In formamide at 65℃; for 1.25h;	76.4%
In water at 105℃; for 0.0133333h;	67.4%

ethanol (64-17-5) + (R)-3-hydroxy-4-cyano-butyric acid (287955-93-5) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With sulfuric acid at 80℃; for 1h;	62%
hydrogenchloride In diethyl ether; ethanol at 20℃; for 30h;
With hydrogenchloride In diethyl ether; ethanol at 20℃; for 30h; Inert atmosphere;
With hydrogenchloride In diethyl ether at 20℃; for 30h; Inert atmosphere;

ethanol (64-17-5) + (R)-3-hydroxy-4-cyano-butyric acid (287955-93-5) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) + (S)-3-hydroxy-4-cyanobutyric acid ethyl ester (312745-91-8)

Conditions	Yield
With hydrogenchloride at 20℃; for 0.5h; Title compound not separated from byproducts.;

3-hydroxyglutaronitrile (13880-89-2) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
Multi-step reaction with 2 steps 1: nitrilase III; phosphate buffer / 22 h / 22 °C / pH 7 2: HCl / 0.5 h / 20 °C View Scheme
Multi-step reaction with 2 steps 1: water / 22 h / 22 °C / pH 7 2: hydrogenchloride / ethanol; diethyl ether / 30 h / 20 °C / Inert atmosphere View Scheme
Multi-step reaction with 2 steps 1: water; A190H / aq. phosphate buffer / 21 °C / pH 7 / Enzymatic reaction 2: hydrogenchloride / diethyl ether / 30 h / 20 °C / Inert atmosphere View Scheme

(R)-4-cyano-3-hydroxybutyric acid calcium salt + ethanol (64-17-5) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With sulfuric acid at 0℃; for 1h; Heating / reflux; Neat (no solvent);

(R)-potassium 3-hydroxy-4-cyano-butyrate (635680-93-2) + ethanol (64-17-5) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With sulfuric acid at 0℃;	n/a

diethyl sulfate (64-67-5) + (S)-(-)-methyl-(3-hydroxy-4-bromo)-butanoate (88759-56-2) + (R)-3-hydroxy-4-cyano-butyric acid (287955-93-5) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With hydrogenchloride; calcium hydroxide; sodium bicarbonate; calcium chloride; triethylamine In water; ethyl acetate

(S)-4-bromo-3-hydroxy-butyric acid ethyl ester (32224-01-4, 95310-94-4, 128052-98-2, 95537-36-3) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With NaCN In ethanol; water	29.8 g (95%)

sodium cyanide (143-33-9) + ethyl (S)-4-chloro-3-hydroxybutanoate (10488-69-4, 86728-85-0, 87068-18-6, 90866-33-4) → (E)-ethyl 4-hydroxybut-2-enoate (10080-68-9) + (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
In water at 55℃; for 3h; pH=8.5 - 9; Product distribution / selectivity;

hydrogen cyanide (74-90-8) + ethyl (S)-4-chloro-3-hydroxybutanoate (10488-69-4, 86728-85-0, 87068-18-6, 90866-33-4) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
Stage #1: hydrogen cyanide With halohydrin dehalogenase In water at 40℃; for 0.5h; pH=7; Stage #2: ethyl (S)-4-chloro-3-hydroxybutanoate In water for 21h; pH=7; Product distribution / selectivity;

sodium cyanide (773837-37-9) + (S)-4-bromo-3-hydroxy-butyric acid ethyl ester (32224-01-4, 95310-94-4, 128052-98-2, 95537-36-3) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
In ethanol; water

sodium cyanide (773837-37-9) + ethyl (-)-(2S)-oxirane-2-acetate (112083-63-3) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With ammonia; nickel dichloride In aq. phosphate buffer; water at 30℃; pH=8; Kinetics; Enzymatic reaction;

sodium cyanide (773837-37-9) + ethyl (2-chloroaceto)acetate (638-07-3) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With vector pACYCDuet-RB and vector pET30-halohydrin dehalogenase in Escherichia coli BL21 (DE3) In aq. buffer at 30℃; for 2h; pH=7; Enzymatic reaction; stereoselective reaction;	n/a

sodium cyanide (773837-37-9) + ethyl (2-chloroaceto)acetate (638-07-3) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) + (S)-3-hydroxy-4-cyanobutyric acid ethyl ester (312745-91-8)

Conditions	Yield
With vector pCDFDuet-HF and vector pET30-(S)-alcohol dehydrogenase in Escherichia coli BL21(DE3) In aq. buffer at 30℃; for 10h; pH=7; Enzymatic reaction; stereoselective reaction;	A n/a B n/a
With halohydrin dehalogenase; NAD; magnesium chloride; alcohol dehydrogenase In tert-butyl methyl ether at 40℃; under 760.051 Torr; for 10h; pH=8; Solvent; Reagent/catalyst; Concentration; Time; Electrolysis; Sealed tube; Inert atmosphere; Enzymatic reaction;	A n/a B n/a

ethyl (S)-4-chloro-3-hydroxybutanoate (10488-69-4, 86728-85-0, 87068-18-6, 90866-33-4) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
With sodium cyanide; halohydrin dehalogenase In aq. phosphate buffer at 30℃; for 4h; pH=8; Enzymatic reaction;

ethyl (2-chloroaceto)acetate (638-07-3) → (E)-ethyl 4-hydroxybut-2-enoate (10080-68-9) + (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
Multi-step reaction with 2 steps 1: ketoreductase / acetic acid butyl ester; water / 11 h / pH 7 2: water / 3 h / 55 °C / pH 8.5 - 9 View Scheme

ethyl (2-chloroaceto)acetate (638-07-3) → (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0)

Conditions	Yield
Multi-step reaction with 2 steps 1: ketoreductase / acetic acid butyl ester; water / 11 h / pH 7 2: water / 3 h / 55 °C / pH 8 View Scheme

O-(4-methoxybenzyl)-trichloroacetimidate (89238-99-3) + (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → ethyl (R)-4-cyano-3-[(4-methoxybenzyl)oxy]butanoate (1031883-60-9)

Conditions	Yield
With boron trifluoride diethyl etherate In dichloromethane; cyclohexane at 25℃; for 3h;	99%

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → (R)-ethyl-5-amino-3-hydroxy-5-oxopentanoate (717127-73-6)

Conditions	Yield
With Wilkinson's catalyst; 2,2-dimethylpropionaldehyde oxime In toluene at 110℃; for 4h;	99%

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → 4-hydroxy-δ-valerolactam (1051316-41-6)

Conditions	Yield
With platinum(IV) oxide; hydrogen In methanol	99%

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → (R)-4-cyano-3-hydroxybutyric acid hydrazide

Conditions	Yield
With hydrazine In ethanol for 2h;	98%

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → (R)-4-cyano-3-hydroxybutyramide

Conditions	Yield
With ammonium hydroxide In methanol for 10h;	83%
With ammonium hydroxide In methanol

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) + methyl iodide (74-88-4) → (R) 4-cyano-3-methoxyl butyric acid ethyl ester

Conditions	Yield
With silver(l) oxide at 20℃;	63.1%

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) + 1,2-dibromomethane (74-95-3) → (R)-6,6-dibromo-3-hydroxy-5-oxohexanenitrile

Conditions	Yield
Stage #1: 1,2-dibromomethane With lithium diisopropyl amide In tetrahydrofuran at -90℃; for 0.0666667h; Inert atmosphere; Flow reactor; Stage #2: (R)-ethyl 4-cyano-3-hydroxybutyrate In tetrahydrofuran at -90℃; Inert atmosphere; Flow reactor;	22%

t-butyl lithioacetate (150942-98-6) + (R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → tert-butyl (5R)-6-cyano-5-hydroxy-3-carbonylhexanoate (125988-01-4)

Conditions	Yield
In tetrahydrofuran; hexane Yield given;

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → (R)-5-Amino-pentane-1,3-diol

Conditions	Yield
With lithium aluminium tetrahydride In tetrahydrofuran
With lithium aluminium tetrahydride In tetrahydrofuran at 0 - 20℃;

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → (R)-3-hydroxy-4-cyano-butyric acid (287955-93-5)

Conditions	Yield
With sodium hydroxide at 20℃; for 2h;
With sodium hydroxide; water for 2h;

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → [3-((R)-4-Cyano-3-hydroxy-butyrylamino)-propyl]-carbamic acid (2R,3S,5R)-2-[bis-(4-methoxy-phenyl)-phenyl-methoxymethyl]-5-(5-methyl-2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-tetrahydro-furan-3-yl ester (669013-16-5)

Conditions	Yield
Multi-step reaction with 2 steps 1: aq. NaOH / 2 h / 20 °C 2: 64 percent / 1-hydroxybenzotriazole hydrate; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; aq. NaH2PO4 / dimethylformamide; tetrahydrofuran / 16 h / 20 °C / pH 5.7 - 6.0 View Scheme

(R)-ethyl 4-cyano-3-hydroxybutyrate (141942-85-0) → (3-{(R)-4-Cyano-3-[(2-cyano-ethoxy)-diisopropylamino-phosphanyloxy]-butyrylamino}-propyl)-carbamic acid (2R,3S,5R)-2-[bis-(4-methoxy-phenyl)-phenyl-methoxymethyl]-5-(5-methyl-2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-tetrahydro-furan-3-yl ester (669013-14-3)

Conditions	Yield
Multi-step reaction with 3 steps 1: aq. NaOH / 2 h / 20 °C 2: 64 percent / 1-hydroxybenzotriazole hydrate; 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride; aq. NaH2PO4 / dimethylformamide; tetrahydrofuran / 16 h / 20 °C / pH 5.7 - 6.0 3: 63 percent / N,N-diisopropylethylamine / CH2Cl2 / 3 h / 20 °C View Scheme

Upstream product

• 86728-85-0 ethyl 4-chloro-3-hydroxybutanoate 
• 143-33-9 sodium cyanide 
• 64-67-5 diethyl sulfate 
• 147028-51-1 4-cyano-3-hydroxybutanoic acid 
• 109462-45-5 (S)-4-bromo-3-hydroxybutanoic acid,methyl ester 
• 32224-01-4 (S)-4-bromo-3-hydroxy-butyric acid ethyl ester 
• 773837-37-9 sodium cyanide 
• 64-17-5 ethanol 
• 635680-93-2 (R)-potassium 3-hydroxy-4-cyano-butyrate 
• 10488-69-4 ethyl (S)-4-chloro-3-hydroxybutanoate 
• 88759-56-2 (S)-bromo-3-hydroxybutyric acid methyl ester 
• 287955-93-5 (R)-3-hydroxy-4-cyano-butyric acid 
• 638-07-3 ethyl (2-chloroaceto)acetate 
• 151-50-8 potassium cyanide 

Downstream Products

• 158008-69-6 (R)-4-cyano-3-hydroxybutyramide 
• 287955-93-5 (R)-3-hydroxy-4-cyano-butyric acid 
• 848645-01-2 ethyl 3-(tert-butyldiphenylsilyloxy)-4-cyanobutanoate 
• 156051-83-1 (R)-6-cyano-5-hydroxy-3-oxo-N,N-bis(phenylmethyl)hexanamide 
• 156051-95-5 (R)-6-cyano-N-(1,1-dimethylethyl)-5-hydroxy-3-oxo-N-(phenylmethyl)hexanamide 
• 1031883-60-9 ethyl (R)-4-cyano-3-[(4-methoxybenzyl)oxy]butanoate 
• 1694-31-1 tert-butyl acetoacetate 
• 125988-01-4 tert-butyl (5R)-6-cyano-5-hydroxy-3-carbonylhexanoate 
• 95310-88-6 (3R)-5-ethoxy-3-hydroxy-5-oxopentanoic acid 
• 152044-54-7 epothilone B 
• 219989-84-1 ixabepilone 
• 189453-10-9 epothilone D 
• 189453-35-8 (4S,7R,8S,9S,13Z,16S,1'E)-4,8-di-tert-butyldimethylsilyloxy-5,5,7,9,13-pentamethyl-16-[1-methyl-2-(2-methyl-1,3-thiazol-4-yl)-1-ethenyl]-1-oxa-13-cyclohexadecene-2,6-dione 
• 193146-26-8 (3S,6R,7S,8S,12Z,15S,16E)-3,7-bis{[tert-butyl(dimethyl)silyl]oxy}-15-hydroxy-4,4,6,8,12,16-hexamethyl-17-(2-methyl-1,3-thiazol-4-yl)-5-oxoheptadeca-12,16-dienoic acid 

Relevant articles and documents

Biphasic Bioelectrocatalytic Synthesis of Chiral β-Hydroxy Nitriles

Two obstacles limit the application of oxidoreductase-based asymmetric synthesis. One is the consumption of high stoichiometric amounts of reduced cofactor. The other is the low solubility of organic substrates, intermediates, and products in the aqueous phase. In order to address these two obstacles to oxidoreductase-based asymmetric synthesis, a biphasic bioelectrocatalytic system was constructed and applied. In this study, the preparation of chiral β-hydroxy nitriles catalyzed by alcohol dehydrogenase (AdhS) and halohydrin dehalogenase (HHDH) was investigated as a model bioelectrosynthesis, since they are high-value intermediates in statin synthesis. Diaphorase (DH) was immobilized by a cobaltocene-modified poly(allylamine) redox polymer on the electrode surface (DH/Cc-PAA bioelectrode) to achieve effective bioelectrocatalytic NADH regeneration. Since AdhS is a NAD-dependent dehydrogenase, the diaphorase-modified biocathode was used to regenerate NADH to support the conversion from ethyl 4-chloroacetoacetate (COBE) to ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE) catalyzed by AdhS. The addition of methyl tert-butyl ether (MTBE) as an organic phase not only increased the uploading of COBE but also prevented the spontaneous hydrolysis of COBE, extended the lifetime of DH/Cc-PAA bioelectrode, and increased the Faradaic efficiency and the concentration of generated (R)-ethyl-4-cyano-3-hydroxybutyrate ((R)-CHCN). After 10 h of reaction, the highest concentration of (R)-CHCN in the biphasic bioelectrocatalytic system was 25.5 mM with 81.2% enantiomeric excess (eep). The conversion ratio of COBE achieved 85%, which was 8.8 times higher than that achieved with the single-phase system. Besides COBE, two other substrates with aromatic ring structures were also used in this biphasic bioelectrocatalytic system to prepare the corresponding chiral β-hydroxy nitriles. The results indicate that the biphasic bioelectrocatalytic system has the potential to produce a variety of β-hydroxy nitriles with different structures.

Nitrilases

The invention relates to nitrilases and to nucleic acids encoding the nitrilases. In addition, methods of designing new nitrilases and methods of use thereof are also provided. The nitrilases have increased activity and stability at increased pH and temperature.

Synthesis of ethyl (R)-4-cyano-3-hydroxybutyrate in high concentration using a novel halohydrin dehalogenase HHDH-PL from Parvibaculum lavamentivorans DS-1

We identified and characterized a novel halohydrin dehalogenase HHDH-PL from Parvibaculum lavamentivorans DS-1. Study of substrate specificity indicated that HHDH-PL possessed a high activity toward ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE). After optimizations of the pH and temperature, whole cell catalysis of HHDH-PL was applied to the synthesis of ethyl (R)-4-cyano-3-hydroxybutyrate (HN) at 200 g L-1 of (S)-CHBE, which gave 95% conversion and 85% yield in 14 h.