Chemistry of isolated 2-pyranones

2 H -pyran-2-one is six-membered oxygen heterocycle having one oxygen in the ring and oxo group at position 2 of the ring and is also known as cyclic unsaturated ester. Two double bonds present are in the conjugation of the ring oxygen. 2-Pyranone-based compounds are well known for more than a century, but the chemistry of these compounds was unexplored and recognized after 1960. Various plants, animals, marine organisms, insects, and bacteria contain pyranone-based compounds in their biological system and participate in various biological processes such as defense mechanism, biosynthetic intermediates, etc. They are reported as HIV protease inhibitors, antifungals, anticonvulsants, cardiotonics, pheromones, antimicrobials, natural pigments, antitumor, and plant growth regulators. In addition, they are synthetically very important precursors for the generation of large class of molecules, for example, use of triacetic acid lactone ( I) and tetraacetic acid lactone ( II) involved for the assembly of α-chymotrypsin, solanopyrones, elastase, pheromones, and coumarins. 6-Aryl-4-methylsulfanyl/ sec .amino-2 H -pyran-2-one-3-carbonitriles are used for the assembly of larger class of carbocycles and heterocycles.