Enantioselective synthesis of novel homochiral α-substituted (S)-isoserine derivatives. Incorporation of this amino acid in a highly conformationally constrained dipeptide surrogate

Optically pure isoserine derivatives with a chiral polyfunctional bicyclo[3.1.0]hexyl substituent at the α-carboxyl position were synthesized from a common cyclopentene precursor bearing an α-epoxy ester function in a side-chain. Cyclopropanation of the double bond and nucleophilic oxirane-ring opening by using a homochiral amine were the key steps. One of the synthesized derivatives was condensed with Cbz-cyclo-Asp-OMe affording a highly conformationally constrained dipeptide surrogate.