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A New General Approach to Enantiomerically Pure Cyclic and Open-Chain (R) - and (S)-alpha,alpha-Disubstituted alpha-Amino Acids


Obrecht, Daniel; Spiegler, Clive; Schönholzer, Peter; Müller, Klaus; Heimgartner, Heinz; Stierli, Friedrich (1992). A New General Approach to Enantiomerically Pure Cyclic and Open-Chain (R) - and (S)-alpha,alpha-Disubstituted alpha-Amino Acids. Helvetica Chimica Acta, 75:1666-1696.

Abstract

A wide range of cyclic and open-chain alpa,alpha-disubstituted alpha-amino acids 1a-p were prepared. The racemic N-acylated alpha,alpha-disubstituted amino acids were resolved by coupling to chiral amines 15-18 derived from (S)- phenylalanine to form diastereoisomers 19/20 or 21/22 that could be separated by crystallization and/or flash chromatography on silica gel (Scheme 3). Selective cleavage via the 1,3-oxazol-5(4H)-ones 10a-p gave the corresponding optically pure alpha,alpha-disubstituted amino-acid derivatives 11 or 12 in high yield (Scheme 3). The absolute configurations of the alpha,alpha-disubstituted amino acids were determined from X-ray structures of the diastereoisomers 20, 21g', 22d.

Abstract

A wide range of cyclic and open-chain alpa,alpha-disubstituted alpha-amino acids 1a-p were prepared. The racemic N-acylated alpha,alpha-disubstituted amino acids were resolved by coupling to chiral amines 15-18 derived from (S)- phenylalanine to form diastereoisomers 19/20 or 21/22 that could be separated by crystallization and/or flash chromatography on silica gel (Scheme 3). Selective cleavage via the 1,3-oxazol-5(4H)-ones 10a-p gave the corresponding optically pure alpha,alpha-disubstituted amino-acid derivatives 11 or 12 in high yield (Scheme 3). The absolute configurations of the alpha,alpha-disubstituted amino acids were determined from X-ray structures of the diastereoisomers 20, 21g', 22d.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:1992
Deposited On:03 Jan 2014 07:01
Last Modified:05 Apr 2016 17:20
Publisher:Wiley-Blackwell
ISSN:0018-019X
Funders:F. Hoffmann-La Roche AG, Basel
Publisher DOI:https://doi.org/10.1002/hlca.19920750522

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