Lipase-mediated regioselective modifications of macrolactonic sophorolipids
摘要:
Chemoenzymatic synthesis and modification of well-defined macrolactonic sophorolipid (SLML) analogues via a series of successive regioselective de-esterification/transesterification reactions is investigated. Of the lipases screened, Candida antartica lipase- B (Novozyme-435) successfully deacylated the C-6' acetoxy group of natural and peracylated SLMLs. Subsequent transesterification with acylating agents (esters of fatty acids) was successful only with the C-6' deacetylated natural SLML providing an avenue to well-defined analogues of varying amphilicity. The macrolactonic motif was essential for enzymatic recognition of the sophorose rings of these complex glycolipids. In the absence of the lactonic motif, the peracylated sophorose rings are not deacylated, rather the carboxyl end of the non-lactonic forms that was preferentially transesterified. All macrolactonic derivatives were characterized by IR, H-1, C-13, H-1-H-1 and H-1-C-13 NMR spectroscopy, as well as HRMS where applicable. (C) 2017 Elsevier Ltd. All rights reserved.
A Convenient Approach to Enantioenriched
Cyclopropanes Bearing Electron-Withdrawing Functionalities
作者:Henryk Krawczyk、Katarzyna Wąsek、Jacek Kędzia
DOI:10.1055/s-0028-1088034
日期:——
1,2-Disubstituted cyclopropanes with different electron-withdrawing groups were accessed stereospecifically from similarly functionalized γ-hydroxy-α,β-unsaturated compounds.
Enantioselective Synthesis of <i>syn</i>/<i>anti</i>-1,3-Amino Alcohols via Proline-Catalyzed Sequential α-Aminoxylation/α-Amination and Horner−Wadsworth−Emmons Olefination of Aldehydes
作者:Vishwajeet Jha、Nagendra B. Kondekar、Pradeep Kumar
DOI:10.1021/ol100856u
日期:2010.6.18
A novel and general method for asymmetric synthesis of both syn/anti-1,3-amino alcohols is described. The method uses proline-catalyzed sequential alpha-aminoxylation/alpha-amination and Horner-Wadsworth-Emmons (HWE) olefination of aldehydes as the key step. By using this method, a short synthesis of a bioactive molecule, (R)-1-((S)-1-methylpyrrolidin-2-yl)-5-phenylpentan-2-ol, is also accomplished.