Deltalactams

Deltalactams are six-membered cyclic amides, a class of lactams in which the amide linkage is contained within a six-membered ring. In lactam-size nomenclature, these are called delta-lactams. The prototypical member is piperidin-2-one (commonly written as 2-piperidone), in which the carbonyl carbon is directly adjacent to the ring nitrogen.

Most deltalam s are derivatives of the 2-piperidone core, including N-substituted and N-acylated variants. The six-membered ring provides a relatively rigid, polar scaffold due to the amide functional group, and it can participate in typical amide chemistry as well as ring-selective transformations. Deltalactams are generally stable under standard laboratory conditions but can undergo hydrolysis or ring-opening under strongly acidic or basic environments, respectively.

Synthesis of deltalamts commonly involves cyclization (lactamization) of appropriate amino acid derivatives or amino alcohol precursors to form the six-membered ring with an embedded amide. Other routes include ring expansion or contraction strategies starting from related lactams or amide-containing intermediates. N-substituted 2-piperidones and other 2-piperidone derivatives are widely reported in the literature as versatile building blocks.

In medicinal and organic synthesis, deltalamts are used as core scaffolds for exploring chemical space. Their combination of ring size, heteroatoms, and functionalizability makes them valuable in the development of pharmaceuticals and in the preparation of libraries of heterocyclic compounds.