page_title: Discovery and development of cephalosporins
section_title: 2nd generation cephalosporins
hierarchical_section_title: Discovery and development of cephalosporins / Drug development / 2nd generation cephalosporins
caption_attribution_description: English: 2nd genxx
context_page_description: Cephalosporins are a broad class of bactericidal antibiotics that include the β-lactam ring and share a structural similarity and mechanism of action with other β-lactam antibiotics. The cephalosporins have the ability to kill bacteria by inhibiting essential steps in the bacterial cell wall synthesis which in the end results in osmotic lysis and death of the bacterial cell. Cephalosporins are widely used antibiotics because of their clinical efficiency and desirable safety profile.
  The cephalosporins are diverse in their antibacterial spectrum, water solubility, acid tolerability, oral bioavailability, biological half-life and other properties. Therefore, the cephalosporins can be further classified into generations depending on antibacterial activity, time of invention and structural basis.
context_section_description: Early second generation cephalosporins are very similar in basic structure to the first generation. Loracarbef however does not have the normal dihydrothiazin ring but is a carbacephem that has a carbon atom in the ring instead of a sulfur atom making it a tetrahydropyridine ring. This chemical property gives Loracarbef better stability in plasma while retaining oral absorption characteristics and affinity for binding to PBP. The 7-phenyl-glycine makes it orally available and the chlorine at position C-3 makes it as active as Cefaclor. An important structural change in the development of second generation cephalosporins was the introduction of an α-iminomethoxy group to the C-7 side chain. This gave an increased resistance to β-lactamases due to stereochemical blocking of the beta-lactam ring. Cefuroxime was the first cephalosporin to incorporate this side chain. Another very important group in the second generation is the aminothiazole ring to the C-3 side chain. This development drastically increased binding affinity to PBP and increased antimicrobial activity. The aminothiazole ring can be seen in the structure of Cefotiam.
caption: Examples of 2nd generation cephalosporins : A) Loracarbef B) Cefuroxime C) Cefotiam
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