A simple and efficient synthesis of an Asp-Gly dipeptide mimetic

Alkylation of Nα-Boc protected aspartic acid with allyl bromide in the presence of lithium bis(trimethylsilyl)amide (LHMDS) and hexamethylphosphoramide (HMPA) afforded chiral β-allyl substituted aspartic acid in good yields. After deprotection of the Nα-Boc group and reprotection as a trifluoroacetamide, the terminal alkene was oxidized to an aldehyde. The aldehyde was then coupled with l-cysteine through a cascade three-bond formation process to afford aspartic acid–glycine bicyclic dipeptide mimetics.