The Novel Asymmetric Synthesis of β-Functionalized Phenylalanine Derivatives

Abstract

As part of a continuing effort in our laboratory to obtain either backbone and/or side chain conformationally constrained, novel amino acids, we have designed and synthesized new types of β-functionalized amino acids, namely β-substituted cysteines, β-substituted serines and β-substituted tryptophanes. β-Substituted cysteines when introduced into the peptide chain can not only constrain backbone conformation through the formation of a disulfide bridge, but also preserve the respective side chains, which is important for the molecular recognition [1]. β-Substituted cysteines and β-substituted serines are also building blocks for so-called “rigid dipeptide β-turn mimetics” [2]. β-Phenylsubstituted tryptophans are chimeric amino acids contaning two bulky side chain groups, a indole and a phenyl group. The interaction between these two bulky side chain groups can produce strong constraints simultaneously for both χ ¹ and χ² side chain torsional angles [3].