A practical synthesis of trans-3-substituted proline derivatives through 1,4-addition |
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Authors: | Huy Peter Neudörfl Jörg-Martin Schmalz Hans-Günther |
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Affiliation: | Department of Chemistry, University of Cologne, Greinstr. 4, 50939 K?ln, Germany. |
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Abstract: | A practical four-step synthesis of 3-alkyl-, vinyl-, and aryl-substituted proline derivatives, which are important building blocks for conformationally restrained peptide analogs, was developed. The method relies on a Cu-catalyzed 1,4-addition of Grignard reagents to N-protected 2,3-dehydroproline esters, efficiently prepared in a new one-pot protocol. The 1,4-addition products are obtained with good trans-selectivity (dr 5:1 to 25:1). A nonracemic sample of N-Cbz-3-vinylproline (74% ee) was obtained using Evans oxazolidinone as a chiral auxiliary. |
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