LACTAM

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: α-lactams, β-lactams, γ-lactams and δ-lactams contain rings made of three, four, five or six atoms, respectively. α-lactams are also called aziridinones. Many widely used antibiotic drugs, including the penicillins and cephalosporins, owe their activity to the presence of a β-lactam structure. The lactams may have substitutions added to the nitrogen atom or any of the non-carbonyl carbon atoms in the base structure. The β-lactam forms the center structure of many antibiotic drugs, such as the cephalosporins and the penicillins.

Beta β, gamma γ and delta δ are the second, third and fourth letters in the alphabetical order of the Greek alphabet, respectively.

Synthesis

General synthetic methods exist for the organic synthesis of lactams.

·      Lactams form by the acid-catalyzed rearrangement of oximes in the Beckmann rearrangement.

·      Lactams form from cyclic ketones and hydrazoic acid in the Schmidt reaction.

·      Lactams form from cyclisation of amino acids.

·      Lactams form from intramolecular attack of linear acyl derivatives from the nucleophilic abstraction reaction.

·      In iodolactamization an iminium ion reacts with an halonium ion formed in situ by reaction of an alkene with iodine.

·      Lactams form by copper catalyzed 1,3-dipolar cycloaddition of alkynes and nitrones in the Kinugasa reaction.

·      Diels-Alder reaction between cyclopentadiene and chlorosulfonyl isocyanate (CSI) can be utilized to obtain both β- as well as γ-lactam. At lower temp (−78 °C) β-lactam is the preferred product. At optimum temperatures, a highly useful γ-lactam known as Vince Lactam is obtained.

Tautomerization to Lactim

Lactim is a cyclic carboximidic acid compound characterized by an endocyclic carbon-nitrogen double bond. It is formed when lactam undergoes tautomerization.

Reactions

Lactams can polymerize to polyamides.