Synthesis of medium-sized ring lactams

Medium-sized ring lactams (7- to 15-membered) find widespread use in organi c chemistry as key intermediates in the synthesis of more complex structure s or as core structures in natural product or pharmaceutically important co mpounds. Until now, the generation of such rings is still a challenge in or ganic synthesis. During the past decade an increasing interest has focused on the generation of cyclic peptides as well as hairpin and beta -turn mimi cs and the medium-sized rings were thought to represent suitable fragments. Furthermore, a range of complex natural products is characterized by such lactam structure and their total synthesis is a broad field for organic che mists to test new strategies and to develop new methods. The aim of the present chapter is to discus some modern strategies to synth esize seven- to fifteen-membered ring lactams, the scope is restricted to t he generation to ring systems bearing a single lactam function. Although th e range of reactions described concern only the generation of simple struct ures without complicated stereogenic properties, most of them seem to bear undiscovered potential with regard to stereoselective synthesis. However, t he emphasis of the methods is focused on stereoselective processes. The rev iew is subdivided in three major chapters of ring closure reactions and rin g enlargements, additional information is given on cycloadditons and fragme ntations.