Oxazolophanes as masked cyclopeptide alkaloid equivalents: cyclic peptide chemistry without peptide couplings

Synthetic studies on the preparation of heteroatom-substituted, novel [3.3]oxazolophanes as precursors to the 14-membered ring system characteristic of the cyclopeptide alkaloids are reported. Simpler model systems are discussed, as is the successful formation of a fully functionalized, nonracemic cyclophane incorporating an oxazole nucleus. Unmasking of the requisite cyclic dipeptide is achieved in a single operation