1. The nomenclature generally employed in this area is as follows. The penam 1, and cepham 2, skeletons are the basic structures commonly encountered among the β-lactam antibiotics, the latter one bearing a double bond at position 3 as the ceph-3-em system. The penicillanic acid structure 3, generally bears an acylamino group at position 6 and has the natural configuration 3S, 5R, 6R. The chirality about the β-lactam (azetidinone) ring in the cephalosporins is the same as for the penicillins: Reference is often made to stereochemical centers in terms of the trivial α,β convention, the α-face being the less hindered side of the folded, bicyclic penam of cepham skeletons. For more details, see P. G. Sammes [4].
2. 8 Functional Modifications and Nuclear Analogues of β-Lactam Antibiotics-Part I
3. Recent chemistry of the β-lactam antibiotics