New Continuous Production Process for Enantiopure (2R,5R)-Hexanediol

Abstract

A new continuous production process has been developed for optically active pure (2R,5R)-hexanediol. The process uses resting whole cells of Lactobacillus kefir DSM 20587 as a biocatalyst. The reduction of (2,5)-hexanedione to (2R,5R)-hexanediol was carried out in a 2-L continuously operated membrane reactor. Conversion of (2,5)-hexanedione was nearly quantitative and the selectivity between product and intermediate was 78% for the product. Enantioselectivity and diastereoselectivity were >99% for the whole period. The productivity of L. kefir could be increased by factor 30. (2R,5R)-Hexanediol was continuously produced over 5 days with a space−time yield of 64 g·L-1·d-1.

Optically Active Phospholanes as Substituents on Ferrocene and Chromium‐Arene Complexes

“…The synthesis of both enantiomers could be achieved with quantitative conversion and with excellent diastereo-and enantioselectivities (Ͼ 96% de, Ͼ 99% ee for the (R,R)-isomer and 99% de, Ͼ 99% ee for the (S,S)-isomer) (Scheme 1). [13] Both enantiomers prepared by this route are now also commercially available.…”

“…Further studies on catalysis employing these ligands are currently under investigation and are due to be published soon. 13 C: 100 MHz, 31 P: 162 MHz) spectrometers at ambient temperature. IR spectra were recorded with a PerkinϪElmer FT-IR model 1720 X spectrometer.…”

“…For a detailed description of the synthesis of (2R,5R)-hexanediol see ref. [13] (2R,5R)-Dimethylphospholane (2): Ammonia (300 mL) was condensed into a three-necked flask at Ϫ78°C. Sodium (5.4 g, 234 mmol) was added in small portions.…”

Membranes in Biotechnology

“…The continuous production of (2R,5R)-hexanediol was studied by Haberland et al [43]. Resting cells of Lactobacillus kefiri DSM 20587 were retained over a UF membrane (membrane area 1.7 m 2 , MWCO 400 kD) in a membrane reactor.…”

Direct Utilization of Naturally Occurring Sulfides for the Asymmetric Epoxidation of Aldehydes Mediated by Catalytic Ylides

“…18,19 This led us to design a C2 symmetric sulfide 1, and to develop a catalytic simple procedure. [20][21][22] The chiral auxiliary was prepared from (2S,5S)-hexanediol, which is accessible by enzymatic reduction 23,24 of 2,5-hexanedione, and commercially available, but not cheap.…”