Lactams

          A cyclic amide that is the nitrogen analog of a lactone. For example, a γ-aminobutyric acid readily forms γ-butyrolactam (also known as 2-pyrrolidinone) upon heating, as in the reaction below. The tautomeric enol form of a lactam is known as a lactim.

          The δ-amino acids similarly form δ (six-membered-ring) lactams upon heating, but larger- and smaller-ring lactams must be made by indirect methods.

Several lactams are of considerable industrial importance. 2-Pyrrolidinone and 1-methyl-2-pyrrolidinone are made by heating γ-butyrolactone with ammonia and methylamine, respectively. They are useful specialty solvents. Vinylation of 2-pyrrolidinone with acetylene gives 1-vinyl-2-pyrrolidinone, which is polymerized to a substance commonly used in aerosol hair sprays.

The ß-lactam antibiotics comprise two groups of clinically important therapeutic agents, the penicillins and the cephalosporins. In both cases they contain a four-membered or ß-lactam ring which has its nitrogen atom and a carbon atom in common with another ring. Such substances are derived commercially from fermentation processes, followed usually by chemical manipulation of the functional groups. See also Amino acids; Biochemical engineering; Lactone.

( McGraw-Hill Science & Technology Encyclopedia)

         any intramolecular cyclic amide produced by the formal removal of a molecule of water between the amino and the carboxyl groups of an amino acid, other than an α-amino acid. A prefix (as in β-lactam) may be used to designate the position of the amino group in the parent compound. A lactam commonly exists in tautomeric equilibrium with its corresponding lactim.

( Oxford Dictionary of Biochemistry)

Lactones, lactams, lactims, and analogues

          Compounds that may be considered as derived from a hydroxy catboxylic acid or amino carboxylic acid by loss of water intramolecularly are called generically "lactones" or "lactams", respectively. Tautomeric forms of lactams are called "lactims". In these recommendations, such compounds are preferably named as heterocycles although names that may be considered to be derived from the corresponding hydroxy or amino acid are also given. R-5.7.5.1 Lactones. Inrtamolecular esters of hydroxy carboxylic acids are "lactones" and are named as heterocycles or by substituting "-olactone" for the "-ic acid" ending of a trivial name of a hydroxy acid, or "-lactone" for the "-ic acid" ending of a systematic "-oic acid" name for the nonhydroxylated parent acid, and inserting a locant designating the position of the hydroxy group between the "o" and "lactone"

Example to R-5.7.5.1

Heterocycles in which one or more (but not all) rings of a polycyclic ring system are lactones are named bu adding the suffix "-carbolactone" (denoting a cyclic group) to the name of the ring system left after the residue is replaced by two hydrogen atoms, preceded by a pair of locants indicating the points of attachment of the carbonyl group and the oxygen atom of the lactone, respectively; the locant for the carbonyl group is cited first, and, if there is a choice, is the lower locant. Multiplying prefixes and pairs of locants separated by a colon denote the precence of two or more lactone rings.

Examples to R-5.7.5.1

(R-2.4.2.1)

(R-2.4.4.1)

R-5.7.5.2 Sultones. Intramolecular esters of hydroxy sulfonic acids are called "sultones" and are named as heterocycles or by citing the term "sultone" denoting the cyclic group after the name of the appropriate parent hydride preceded by a pair of locants describing the points of attachment of the sulfonyl group and oxygen atom, respectively; the locant for the sulfonyl group is cited first and, if there is a choice, is the lower locant. Multiplying prefixes and pairs of locants separated by a colon are used to indicate two or more sultone rings.

Examples to R-5.7.5.2

R-5.7.5.3 Lactams and lactims. Nitrogen analogues of lactones having the group as part of a ring or ring system are called generically "lactams" and their tautomers, , are "lactims". These compounds are named as heterocyclic compounds or in accordance with R-5.7.5.1 using "-lactam" or "-lactim", respectively, in place of "-lactone". Names such as "propiolactam" and "butyrolactim" are not included in these recommendations.

Examples to R-5.7.5.3

Tetrahydropyrrol-2-one
Pyrrolidin-2-one (2-Pyrrolidone)
Butano-4-lactam

R-5.7.5.4 Sultams. Nitrogen analogues of sultones having the group as a part of a ring are named as heterocycles or in accordance with R-5.7.5.2 using "sultam" in place of "sultone". The locant for the point of attachment of the sulfonyl group is cited first and, where there is a choice, has preference over the imino group for lower locant.
Examples to R-5.7.5.4