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heterocyclic compounds that contain an oxygen atom and two conjugated (α-pyrene) or isolated (γ-pyran) double bonds. Pyrans are highly unstable compounds: α-pyran is only known in derivative form, and γ-pyran is a colorless liquid with a boiling point of 84°C (with decomposition; also decomposes rapidly at room temperature).

Dihydropyrans and tetrahydropyrans are most stable and more readily accessible. Important pyran derivatives are αpyrone

and γ-pyrone. The pyran ring is a structural feature of many natural substances. For example, most hexoses (aldoses and ketoses) are essentially six-membered pyranoses.

References in periodicals archive ?
Smoke screen systems that use PYRANS do not need frame constructions at all.
PYRANS borosilicate fire-resistant glass at Hangar 7 is opening up a new dimension of transparent architecture in a format previously unattained in frameless glazing: the fire-resistant glass separates the two fire-protection compartments over a floor height of up to 3.
Kolekar, An Efficient Protocol for Synthesis of tetrahydrobenzo [b] pyrans using Amino Functionalized Ionic Liquid, C.