名称:
                                Synthesis of .alpha.-benzyl .gamma.-lactam, .alpha.-benzyl .delta.-lactam, and .alpha.-benzylproline derivatives as conformationally restricted analogs of phenylalaninamide
                             
                            
                                摘要:
                                The ready availability of N-(trifluoroacetyl)-alpha-allylphenylalaninamide (4) via a dehydration/hetero-Cope rearrangement/ammonolysis sequence starting with N-(trifluoroacetyl)phenylalanine allyl ester made it an attractive intermediate for elaboration into C-alpha to N- or C-alpha to N'bridged products as conformationally restricted phenylalaninamide analogues.  Oxidative one-carbon degradation of the side-chain olefin followed by acid-catalyzed silane reduction afforded C-alpha to N'-bridged gamma-lactam.  Hydroboration/oxidation of the side-chain olefin provided an intermediate that could be cyclized selectively either to a delta-lactam or a proline analogue depending on choice of dehydrating conditions.  For preparation of a target dipeptide containing the alpha-substituted proline moiety, a preferred route involved N-deprotection of 4 and coupling to Boc-Asp(OBn)-OH to give a dipeptide intermediate, which similarly could be elaborated selectively to either the alpha-benzyl delta-lactam analogue or the alpha-benzylproline analogue.