The enantioselective hydrolysis of insoluble (R,S)-ketoprofen ethyl ester to the optically active (S)-ketoprofen was carried out in a dispersed aqueous lipase reaction system induced by the inclusion of chiral cyclodextrins for complexation of the substrate. Hydroxypropyl-beta-cyclodextrin was the most effective chiral selector and disperser giving an enantiomeric excess and conversion yield of 0.99 and 0.49, respectively.
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http://dx.doi.org/10.1023/b:bile.0000030040.13828.d7 | DOI Listing |
Chemistry
December 2024
Organocatalysis Research Group, Institute of Organic Chemistry, HUN-REN Research Centre for Natural Sciences, 2. Magyar tudósok krt., H-1117, Budapest, Hungary.
A concise, bioinspired, and enantioselective synthesis of (-)-hunterine A, an odd 6/7/6/6/5 pentacyclic natural product, is described. The key step in the synthesis of this complex structure is an interim-template directed 6-exo selective epoxide ring-opening reaction, which is interwoven with a hydrolysis step of the indolenine hemiaminal template to create the unusual 7-membered azepine bridge motif. Our work not only refines the previously proposed biogenetic pathway, but also reveals the possible stereochemical prerequisite of the unique skeletal rearrangement, which provides a vantage point for understanding how (-)-hunterine A is likely to be generated in nature.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain.
Bioorg Chem
December 2024
College of Science, Sichuan Agricultural University, Ya'an 625104, China; Featured Medicinal Plants Sharing and Service Platform of Sichuan Province, Ya'an 625104, China. Electronic address:
Chemistry
November 2024
Dipartimento di Chimica e Biologia "A. Zambelli", Università di Salerno, Via Giovanni Paolo II, 84081, Fisciano, Italy.
Optically active mandelic acid esters represent a highly valuable class of building blocks in organic synthesis and recurrent motifs embedded in bioactive compounds and drugs. Herein, we provide an enantioselective one-pot synthesis based on Knoevenagel condensation/asymmetric epoxidation/domino ring-opening hydrolysis (DROH) sequence to the crude mandelic acids, which underwent a final esterification step to (R)-methyl mandelates. These products have been obtained in good to high overall yield and enantioselectivity, using commercially and widely available reagents and catalyst including aldehydes, phenylsulfonyl acetonitrile, cumyl hydroperoxide, water and an epi-quinine-derived urea as the organocatalyst.
View Article and Find Full Text PDFJ Org Chem
November 2024
Centre for Synthesis and Chemical Biology, School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland.
The preparation of a focused library of chiral 2-amido and 2-amido-1-phenyl-1,3-dienes from a range of chiral oxazolidinones using palladium-catalysis is reported. This palladium-catalyzed carbon-nitrogen bond-forming reaction provides the corresponding chiral amido-dienes in moderate to excellent yields (12 examples, up to 97%). The resulting chiral amido-dienes are employed as novel dienes in Diels-Alder (DA) reactions (58 examples, up to 93:7 dr, up to 70% yield).
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