An efficient RCM-based synthesis of orthogonally protected meso-DAP and FK565.

A condensation--ring-close--ring-open sequence was employed for the synthesis of orthogonally protected meso-2,6-diaminopimelic acid, starting from easily accessible chiral synthons. Condensation of suitably protected L-allylglycine and D-vinylglycinol derivatives was followed by Grubbs' ring-closing metathesis to generate the key lactam intermediate. This strategy has been applied to a concise total synthesis of the potent immunostimulatory peptide FK565.