Advances in the Use of Enantiopure β-Lactams for the Synthesis of Biologically Active Compounds of Medicinal Interests

β-Lactams play a significant role in organic synthesis in addition to its importance as the core structure of β-lactam antibiotics. The “β-lactam synthon method” introduced in late 1970s has greatly advanced the use of β-lactams as key intermediates for the synthesis of biologically active compounds such as nonprotein amino acids, peptides, peptidomimetics, and complex natural products and congeners. This chapter describes the advances in the synthesis of β-lactams with excellent enantiopurity, useful patterns of β-lactam ring cleavage, ring-opening coupling, and applications of the β-lactam synthon method to the synthesis of biologically active compounds of medicinal interests. In addition, novel β-lactams, exhibiting potent activities, not as antibacterials but as anticancer and cholesterol-controlling agents, are described.