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DOI: 10.1055/s-2007-968750
Concise Synthesis of Vinyl Glycines
Contributor(s):Benjamin List, Corinna ReisingerImperial College London, UK
Exploiting Organocatalysis: Enantioselective Synthesis of Vinyl Glycines by Allylic Sulfimide [2,3] Sigmatropic Rearrangement
Angew. Chem. Int. Ed. 2007, 46: 5369-5372
Publication History
Publication Date:
24 July 2007 (online)
Key words
vinyl glycines - α-sulfenylation - allylic sulfides - oxaziridines - [2,3]-sigmatropic rearrangement
Significance
A concise asymmetric synthesis of (E)-vinyl glycines 7 has been achieved. Enantioselective α-sulfenylation of aldehydes 1 catalyzed by α,α-diaryl prolinol ether 2 followed by stereoselective in situ olefination of intermediates 4 allowed ready access to optically enriched allylic sulfides 5. Subsequent amination of 5, accomplished by using oxaziridine 6 and stereospecific [2,3]-sigmatropic rearrangement of the resulting allylic sulfimides, furnished products 7 in good overall yields with essentially complete chirality transfer. Rapid and clean N-S bond cleavage took place on treatment with P(OEt)3 and Et3N. Finally, a one-pot amination-rearrangement-desulfurization sequence directly giving N-Boc-protected (E)-vinyl glycines could be realized.
Comment
Vinyl glycines (β,γ-unsaturated amino acids) are highly interesting and synthetically challenging motifs present in several biologically significant targets. Combining an organocatalytic α-sulfenylation of aldehydes (K. A. Jørgensen and co-workers Angew. Chem. Int. Ed. 2005, 44, 794) with the [2,3]-sigmatropic rearrangement of allylic sulfimides, which has previously been utilized in the Armstrong group (J. Org. Chem. 2006, 71, 4028), has resulted in a highly valuable and practical synthesis of vinyl glycines. An intriguing feature of the present study is that both enantiomeric product series (7 and ent-7) can be obtained from the same chiral catalyst depending on the choice of either E- or Z-selective in situ olefination.