Palladium(0)-catalyzed reactions of N-methanesulfonyl- or N-(arenesulfonyl)-3-alkyl-2-vinylaziridines reveal that 2,3-cis-isomers are more stable than the corresponding 2,3-trans-isomers in accord with ab initio calculations. A highly stereoselective synthetic route to (E)-alkene dipeptide isosteres having desired stereochemistries from 2,3-cis-3-isobutyl-2-vinylaziridine by the use of organocopper chemistry is also presented.

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Palladium(0)-catalyzed reactions of five sets of four stereoisomeric 4,5-epimino-N-(methanesulfonyl) or -N-(arylsulfonyl) 2-enoates reveal that 4,5-cis-(2E)-isomers are thermodynamically more stable than other isomers, in accord with calculations. A highly stereoselective synthesis of (E)-alkene dipeptide isosteres having the desired stereochemistries from unwanted stereoisomeric 4,5-epimino-N-(arylsulfonyl) 2-enoates is also presented.

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Palladium (0)-catalysed reactions of N-alkylsulfonyl-or N-arylsulfonyl-3-alkyl-2-vinylaziridines reveal that 2,3-cisisomers are more stable than the corresponding 2,3-truns-isomers in accord with ab initio calculations.Activated chiral aziridines, notably 2-~inylaziridines~ and their derivatives,3 are versatile synthetic intermediates for the synthesis of biologically important compounds. Recently we,4 Mercks and Dupont Merck6 groups, and Panek7 have reported that peptides containing (E)-alkene dipeptide isosteres show potent biological activity. As part of an ongoing project aimed at the synthesis of biologically active peptides containing (E)alkene isosteres* we required a reliable method for the preparation of activated cis-3-alkyl-2-vinylaziridines 4, key synthetic intermediates in the synthesis of these isosteres.Chiral activated 3-alkyl-2-vinylaziridines 4 and 5 could be derived from a homochiral N-protected amino aldehyde 1 via amino alcohols 2 and 3. However, the highly stereoselective synthesis of either syn-or anti-amino alcohols 2 or 3 and hence 2,3-cisor 2,3-trans-3-alkyl-2-vinylaziridines 4 or 5 from an amino aldehyde 1 has hitherto been difficult.

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