Pyrans

thumb|upright=1.25|Four steps of molybdenum cofactor (Moco) biosynthetic pathway occurring in bacteria and humans: (i) radical-mediated cyclization guanosine 5'-triphosphate (GTP) to (8S)‑3,8‐cyclo‑7,8‑dihydroguanosine-5́‑triphosphate (3,8‑cH2GTP), (ii) formation of cyclic pyranopterin monophosphate (cPMP) from the 3,8‑cH2GTP, (iii) conversion of cPMP into molybdopterin (MPT), (iv) insertion of molybdate into MPT to form Moco (human enzymes in parentheses). Molybdopterins are a class of cofactors found in most molybdenum-containing and all tungsten-containing enzymes. Synonyms for molybdopteri

In chemistry, pyran is a six-membered heterocyclic, non-aromatic ring, consisting of five carbon atoms and one oxygen atom and containing two double bonds. The molecular formula is C5H6O. There are two isomers of pyran that differ by the location of the double bonds. In '2H-pyran, the saturated carbon is at position 2, whereas, in 4H-pyran', the saturated carbon is at position 4. "Oxine” is not used for pyran because it has been used as a trivial name for quinolin-8-ol.

A spiropyran is a type of photochromic organic chemical compound, characterized by their ability to reversibly switch between two structural forms—spiropyran and merocyanine—upon exposure to light or other external stimuli. This reversible transformation alters their optical and electronic properties, making them valuable in various applications, including molecular switches, optical data storage, sensors, and smart materials.

Xylindein is a quinone pigment, a dimeric naphthoquinone derivative. It is produced by fungi in the genus Chlorociboria. This pigment causes green staining of wood infected by the fungi.