Lactams


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Related to Lactams: lactim

Lactams

 

internal cyclic amides of amino carboxylic acids that contain a —CO—NH— group in the ring (I). The tautomeric, enol form of lactam is known as lactim (II):

Lactams are classified as β-, γ-, δ-, ε-, and so forth according to the type of amino carboxylic acids included in their composition, for example, β-propiolactam (III; melting point, 73°-74°C), γ-butyrolactam (IV; melting point, 24.6°C), and ε-caprolactam (V; melting point, 68°-69°C):

Lactams are primarily obtained by the cyclization of amino carboxylic acids or their derivatives [Y—(CH2)nNH2, where Y = COOH, COOR, CONH2, CN], as well as by the cyclization of amides of halogen carboxylic or hydroxycarboxylic acid [X—(CH2)nCONHR, where X = OH or a halogen]. An important method of obtaining lactam is the Beckmann rearrangement of cyclic ketoximes, which is used in the industrial preparation of ε-caprolactam.

Lactams readily undergo alkylation, acylation, and halogena-tion with retention of the ring. The lactam ring, however, is opened at the —CO—NH—bond during hydrolysis, ammonolysis, hydrogenolysis, and polymerization. For example, ε-caprolactam polymerization yields polycaproamide, from which nylon 6 fiber is made. Many lactams are biologically active substances (for example, a molecule of penicillin contains a β-propiolactam residue).

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The antibiotics investigated in the study included penicillins (ampicillin, carbenicillin and piperacillin), 1st generation cephalosporins (cephalothin), 2nd generation cephalosporins (cefuroxime, cefoxitin and cefaclor), 3rd generation cephalosporins (ceftriaxone, cefotaxime and ceftazidime), 4th generation cephalosporins (cefepime) carbapenems (imipenem) and monocyclic lactams (aztreonam).
The sensitive and resistance rates to 2nd and 3rd generation cephalosporins and monocyclic lactams were close, but resistance rate to cefoxitin was very low.
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Results of the frequency of use of different tests for screening for p lactam antibiotics in milk were shown in Figure 1.
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Comparative in vitro activity of beta lactam / beta lactamases inhibitor combinations against gram negative bacteria.