Synthesis of highly functionalized phenylalanine derivatives via cross-enyne metathesis reactions

A new method for the synthesis of constrained phenylalanine derivatives is described. In this regard, the simple synthesis of acyclic diene building blocks embodying an α-amino acid moiety has been achieved. The diene building blocks have been prepared by cross enyne-metathesis reaction as a key step. The Diels–Alder reaction of the dienes with a dienophile such as dimethyl acetylenedicarboxilate (DMAD) followed by oxidation of the resulting cycloadduct gave highly substituted phenylalanine derivatives.