1,720,965 research outputs found
Stereoselective synthesis of short benzyl malonyl peptides
No full textA Rh-catalyzed addition reaction on non symmetric dehydro alanine retro-peptides is the key step in the reported three-step strategy for the diastereoselective synthesis of differently functionalized benzyl malonyl peptides (74% overall yield)
Synthesis of gem-diamino acid derivatives by a Hofmann rearrangement
No full textStarting from commercially available N-protected l-alpha-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 alpha-carbamoyl alpha'-carboxyl aziridines, also functionalized with l-alpha-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
Chiral bidiaziridines by a two-step domino aziridination of meso-α-diimines
No full textChiral racemic α-diimines, tested in aziridination reactions with NsONHCO2Et, for the first time led to the synthesis of d,l-bidiaziridines, stereoselectively derived from the corresponding meso (E-s-trans-E)-α-diimines. Moreover, a minor bidiaziridine isomer, probably a meso form that was lost under classical work-up conditions, can be obtained by adding water to the crude mixtures at the end of amination reactions. The results definitively prove that the imine aziridination by carbamates is a two-step domino process. The structures of the compounds were determined using 2D NMR on purified bidiaziridine
Short malonyl dehydro peptides as potential scaffolds for peptidomimetics by an efficient Knoevenagel reaction
No full textNon-symmetric disubstituted malonamides rAA-mGly-AA', obtained from Meldrum's acid, were considered as methylene active compounds and a Knoevenagel condensation methodology was developed involving piperidine and activated 4 molecular sieves as catalysts. The reaction is efficient, broad in scope, and easy to perform and allows access to E/Z mixtures of short malonyl dehydro peptides (MDHPs) rAA-m Delta(2)AAaEuro(3)-AA', partially modified retro peptides characterized by an interesting combination of retro and dehydro modifications in the same structure
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