Synthesis of MEN11420, a glycosylated bicyclic peptide, by intramolecular double cyclization using a chloroimidazolinium coupling reagent

The synthesis of MEN11420, a potent tachykinin receptor antagonist, has been achieved. The bicyclic glycosylated structure of MEN11420 was constructed via intramolecular double cyclization using CIP-mediated activation. The head to tail cyclization of the linear precursor, which contained an α-amino acid at its C-terminus, proceeded so rapidly that no serious racemization was apparent at the activated carboxyl function. The desired product was obtained without the need for purification of the intermediates throughout the synthesis.