Wiktionary
chromane
n. (context organic compound English) A bicyclic heterocycle in which a benzene ring is fused to one of dihydro-pyran; it is the base unit of tocopherols
Wikipedia
Chromane
Chromane (benzodihydropyran) is a heterocyclic chemical compound with the chemical formula CHO. Chromane is a structural feature of more complex compounds including E vitamins ( tocopherols and tocotrienols) and the pharmaceutical drugs troglitazone, ormeloxifene, and nebivolol.