Synthesis of functionally diverse and conformationally constrained polycyclic analogues of proline and prolinol

Alkylation of the monoenolate of N-Boc-l-pyroglutamic acid methyl ester with a variety of benzylic halides and their homologues gave the corresponding anti-C-4-alkylated products as major products. Formation of the N-Boc-iminium ion and Friedel-Crafts intramolecular cationic ring closure afforded a series of fused 1-azacyclodihydroindene derivatives with interesting topologies. Functional diversity was introduced via further manipulation of pendant groups on the original proline motif as well as on the aromatic moiety.