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Various new nickel complexes and amides are synthesized using monomeric nickel hydroxide (PN3P)Ni(OH) (3) as the precursor or catalyst.

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Starting from commercially available N-protected L-α-amino acids, N,N'-protected gem-diaminic units were obtained by a two-step methodology. A Hofmann reaction performed using a primary alcohol as the solvent to trap the isocyanate intermediate represents the key step of the new synthetic procedure. Then, the methodology was applied to α-carbamoyl α'-carboxyl aziridines, also functionalized with L-α-amino esters and stable gem-diaminic units characterized by an aziridine ring and by a retro-peptide modification were obtained. The use of the latter units in the retro-peptide chemistry allows to obtain modified peptides containing an aziridine ring able to behave as an electrophilic site and as a biomimetic structural analog of proline.

Desymmetrization of chiral α-diimines by ethyl nosyloxycarbamate using water as a co-solvent takes place with very high diastereoselectivity, the nucleophilic attack occurring only on the less hindered side of the CN double bond. Interestingly, the presence of water in the reaction medium likely stabilizes the anion intermediate slowing down the successive cyclization reaction and favoring the rotation around the C-N single bond. In fact, as confirmed by ROESY experiments, only the two diastereomeric 3-(iminomethyl) diaziridine-1-carboxylates that differ in the absolute configuration of the alkyl substituted nitrogen atoms were always obtained in equimolar ratios. Finally, all compounds were easily obtained in optically pure form through HPLC separation and can be considered as interesting chiral synthons. © 2013 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique