β-Homo-peptides Built from β2,2-HBip, a Biphenyl-substituted 3-Amino-2,2-dimethylpropanoic Acid

Abstract A novel β 2,2 - gem -disubstituted amino acid, β 2,2 -HBip, has been synthesized by α,α-bis-alkylation of alkyl cyanoacetates with 2,2′-bis-(bromomethyl)-1,1′-diphenyl, followed by NaBH 4 /CoCl 2 reduction of the cyano group. Both its C- and N-protected derivatives have been obtained. A slow interconversion at the NMR time scale is generally observed between the two enantiomers of the conformationally labile β 2,2 -HBip residue. The homo-peptides Boc-(β 2,2 -HBip) n -OMe have been prepared in solution by the EDC/HOBt coupling method to the hexamer level and a preliminary conformational analysis has been performed by 1 H NMR and FT-IR absorption techniques.