Lactam: Difference between revisions
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{{Image|Lactams.jpg|right|200px|<small>Lactam structures.</small>}} | {{Image|Lactams.jpg|right|200px|<small>Lactam structures.</small>}} | ||
In chemistry, a '''lactam''' is a cyclic [[amide]]. The name is derived from two chemical terms, [[lactone]], referring to a cyclic ketone, and [[amide]], a compound containing a [[nitrogen]] atom next to a [[carbonyl]] group. Lactams are named according to the size of the cyclic ring in the lactam: <math>\alpha</math>-lactams, <math>\beta</math>-lactams, <math>\gamma</math>-lactams and <math>\delta</math>-lactams contain rings made of three, four, five or six atoms, respectively. <math>\alpha</math>-lactams are also called aziridinones. Many widely used antibiotic drugs, including the[[penicillin]]s and [[cephalosporin]]s, owe their activity to the presence of a <math>\beta</math>-lactam structure. The lactams may have substitutions added to the nitrogen atom or any of the non-carbonyl carbon atoms in the base structure. | In chemistry, a '''lactam''' is a cyclic [[amide]]. The name is derived from two chemical terms, [[lactone]], referring to a cyclic ketone, and [[amide]], a compound containing a [[nitrogen]] atom next to a [[carbonyl]] group. Lactams are named according to the size of the cyclic ring in the lactam: <math>\alpha</math>-lactams, <math>\beta</math>-lactams, <math>\gamma</math>-lactams and <math>\delta</math>-lactams contain rings made of three, four, five or six atoms, respectively. <math>\alpha</math>-lactams are also called aziridinones. Many widely used antibiotic drugs, including the [[penicillin]]s and [[cephalosporin]]s, owe their activity to the presence of a <math>\beta</math>-lactam structure. The lactams may have substitutions added to the nitrogen atom or any of the non-carbonyl carbon atoms in the base structure. | ||
== Synthesis of lactams == | == Synthesis of lactams == | ||
Revision as of 11:08, 23 May 2010
In chemistry, a lactam is a cyclic amide. The name is derived from two chemical terms, lactone, referring to a cyclic ketone, and amide, a compound containing a nitrogen atom next to a carbonyl group. Lactams are named according to the size of the cyclic ring in the lactam: -lactams, -lactams, -lactams and -lactams contain rings made of three, four, five or six atoms, respectively. -lactams are also called aziridinones. Many widely used antibiotic drugs, including the penicillins and cephalosporins, owe their activity to the presence of a -lactam structure. The lactams may have substitutions added to the nitrogen atom or any of the non-carbonyl carbon atoms in the base structure.
Synthesis of lactams
Synthesis of alpha-lactams
The cyclization reaction of an -haloamide precuror in the presence of sodium hydride and 15-crown-5 ether at room temperature in dichloromethane (CH2Cl2) is a high-yielding, general route to -lactam (aziridinone) products. The hydrogen gas and sodium halide by-products are readily removed.[1]
Antibiotics
The -lactam forms the center structure of many antibiotic drugs, such as the cephalosporins and the penicillins, as shown above. In the penicillins, the non-lactam ring is one atom smaller compared to the cephalosporins. The activity of cephalosporins, penicillins, and some other antibiotics are due to the presence of the beta-lactam, which binds irreversibly, via acylation, to penicillin-binding proteins, thereby inhibiting the peptidogycan layer of bacterial cell wall synthesis. Cephalosporins and penicillins are often made semi-synthetically, using a core structure obtained from a natural organism, such as a fungus, due to the difficulty and expense of synthesizing these lactams.
- ↑ V. Cesare, T. M. Lyons and I. Lengyel (2002). "A High-Yielding General Synthesis of α-Lactams". Synthesis 2002: 1716-1720.