Abstract
New peptidomimetics featuring CH(RF )NH units, having different degree of fluorination, as peptide-bond surrogates have been synthesized. The key step in the synthesis consists of a stereoselective aza-Michael addition of chiral α-amino acid esters to β-fluoroalkyl-α-nitroethenes. The diastereoselection of the process was influenced by the electronegativity, rather than by the steric bulk, of the fluorinated residue RF in β-position of the nitroalkene acceptors. Replacement of a single F atom of RF by a hydrogen or methyl group brings about a dramatic drop of stereocontrol, whereas Br, Cl, and CF3 , albeit bulkier than F, provide poorer results in terms of stereocontrol.
Key words
peptidomimetics - fluorine - electronegativity - peptide bond surrogate - fluoroalkyl
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