Highly reactive 4-membered ring nitrogen-containing heterocycles: Synthesis and properties.

4-Membered nitrogen-containing heterocycles, such as β-lactams (ie, 2-azetidinones) and azetidines, are useful substrates in organic chemistry for the design and preparation of biologically active compounds by functionalization of the different positions of the ring. In addition, these compounds are versatile building blocks for the synthesis of other types of nitrogen-containing compounds with potential biological properties. This review summarizes recent data regarding the preparation and properties of 4-membered nitrogen-containing heterocyclic rings, as well as their biological activities.