Regioselective Alcoholysis of Silychristin Acetates Catalyzed by Lipases

Abstract

A panel of lipases was screened for the selective acetylation and alcoholysis of silychristin and silychristin peracetate, respectively. Acetylation at primary alcoholic group (C-22) of silychristin was accomplished by lipase PS (Pseudomonas cepacia) immobilized on diatomite using vinyl acetate as an acetyl donor, whereas selective deacetylation of 22-O-acetyl silychristin was accomplished by Novozym 435 in methyl tert-butyl ether/n-butanol. Both of these reactions occurred without diastereomeric discrimination of silychristin A and B. Both of these enzymes were found to be capable to regioselective deacetylation of hexaacetyl silychristin to afford penta-, tetra- and tri-acetyl derivatives, which could be obtained as pure synthons for further selective modifications of the parent molecule.

Chirality Matters: Biological Activity of Optically Pure Silybin and Its Congeners

“…The above enzymatic protocols were also tested with silychristin A/B. However, none of the tested lipases [59] was suitable for kinetic separation of silychristin A and silychristin B, so only chromatographic methods can be considered [46]. Most of the above procedures require silica gel chromatography or reversed-phase HPLC.…”

Three Regioselectively Acylated Flavonoid Aglycone Derivatives in Equimolar Yield at One Blow

“…We have reported that Candida antarctica lipase B (CALB) can transform flavonoid aglycones to their relevant esters in organic solvents using proper acyl donors, whereas alcoholysis reactions have been reported for flavonolignans consisted of a flavonoid and a lignan part . Along these lines, we developed a simple and time‐effective process, the “NMR‐tube bioreactor”, allowing to monitor in situ the transformation efficacy and regioselectivity in multiple substrate biotransformations .…”

Cold-Active Lipase-Based Biocatalysts for Silymarin Valorization through Biocatalytic Acylation of Silybin

“…Besides chemical modification, or chemo-enzymatic or biocatalytic approaches, Xanthakis et al showed that a lipase-based acylation of silybin with vinyl butyrate via Novozyme 435 biocatalyst strongly depends on the organic medium, where the conversion degree increased from 78 to 100% [18]. In favor of a faster synthesis, Vavrikova et al used divinyl esters to modify silybin through Candida antartica B lipase mediation and achieved silybin dimers with a 24-44% yield range [19].…”