Synthesis of a Chiral Precursor for (R) α Lipoic Acid via Novozym 435 Mediated Enantioselective Transesterification
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Graphical Abstract
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Abstract
Abstract: An efficient process by lipase catalyzed transesterification to synthesize optically pure ethyl 8 chloro 6 hydroxy octanoate (ECHO), an important chiral precursor for the synthesis of (R) α lipoic acid, was developed. The conditions of enzymatic resolution were optimized. The production of (R) O acetylated ECHO was achieved in 90% eep, 47% conversion within 6 h, 36.3% isolated yield and 471 g/(L·d) space time yield on a gram scale synthesis using vinyl acetate as acyl donor, diisopropyl ether as solvent, with 100 g/mol ECHO catalyst loading and 1 mol/L substrate loading at 50 ℃. This process provides a new way for the preparation of (R) α lipoic acid precursor.
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