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[摘要]：New peptidomimetics featuring CH(RF)NH units, having different degrees of fluorination, as peptide-bond surrogates were synthesized. The key step in the synthesis consists of a stereoselective aza-Michael addn. of chiral a-amino acid esters to b-fluoroalkyl-a-nitroethenes. The diastereoselection of the process was influenced by the electronegativity, rather than by the steric bulk, of the fluorinated residue RF in b-position of the nitro alkene acceptors. Replacement of a single F atom of RF by an H or Me group brings about a dramatic drop of stereocontrol, whereas Br, Cl, and CF3, albeit bulkier than F, provide poorer results in terms of stereocontrol. |
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