Diastereoselective Synthesis of New <i>ψ</i>[(<i>E</i>)-CHCMe]- and <i>ψ</i>[(<i>Z</i>)-CHCMe]-type Alkene Dipeptide Isosteres by Organocopper Reagents and Application to Conformationally Restricted Cyclic RGD Peptidomimetics
cis-conformers of D-Phe-L-MeVal, respectively, were utilized in a structure-activity relationship study on cyclic RGD peptides 1 and 2, in company with a psi[(E)-CH=CH]-type alkene dipeptide isostere, D-Phe-psi[(E)-CH=CH]-L-Val. The cyclic isostere-containing pseudopeptides 3, 4, and 40 were synthesized and biological activity against integrin alpha(V)beta(3) and alpha(IIb)beta(3) receptors were also evaluated.