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Recent Progress in Chemistry of β-Lactams

The β-lactams constitute a well-known class of compounds having tremendous biological significance. Besides being a motif of biological interest, they serve as versatile synthons in organic chemistry. In fact, their easy accessibility in the laboratory by several methods combined with inherent reactivity of the β -lactam ring due to ring-strain places it among the most sought for substrate in the arsenal of synthetic organic chemists. Several chemical reagents, heat, and light promote its ring-opening, ring-expansions and rearrangement reactions yielding a wide variety of biologically relevant nitrogen-containing acyclic and heterocyclic compounds. In recent years, the reactivity of differently functionalized β-lactam rings towards diverse kinds of reagents has been investigated. These investigations exploit selective bond cleavage of the β-lactam nucleus via N1-C2, C3- C4, C2-C3 or N1-C4 bond cleavage using simple reagents. The reduction of amide carbonyl group, thionation, and pyrolysis/photolysis have also been explored. These investigations have led to the discovery of many easy synthetic methods for biologically important classes of compounds such as β-amino acids, β-amino esters, amino sugars, amino alcohols, peptides, azetidines, and other heterocyclic compounds. This article discusses the advances made in the studies on the reactivity of β- lactam ring during the last ten years.