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Generation and Recovery of β-cell Spheroids From Step-growth PEG-peptide Hydrogels
Published on: December 6, 2012
A versatile chemo-enzymatic route to enantiomerically pure beta-branched alpha-amino acids
Geoffrey J Roff1, Richard C Lloyd, Nicholas J Turner
1School of Chemistry, University of Edinburgh, King's Buildings, West Mains Road, Edinburgh, EH9 3JJ, U.K.
Abstract:
A series of diastereoisomers of beta-methyl-beta-phenylalanine analogues 1a-f have been prepared in enantiomerically pure form using a combination of chemo- and biocatalysis. Starting from l-threonine methyl ester 2, a range of beta,beta-disubstituted didehydroamino acids were obtained as their (Z)-isomers 6a-f. Asymmetric hydrogenation of these alkenes, using either the [Rh(R,R)-Et-DuPhos(COD)]BF4 or [Rh(S,S)-Et-DuPhos(COD)]BF4 catalyst, followed by hydrolysis yielded two of the four possible sets of diastereoisomers of the beta-branched amino acid. Subsequent stereoinversion, using a stereoselective amino acid oxidase in combination with a nonselective reducing agent, furnished the remaining two sets of diastereomers.
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