<unk> , or oxane, is the organic compound consisting of a saturated six-membered ring containing five carbon atoms and one oxygen atom.
The<unk>  ring system is the core of pyranose sugars.
In organic synthesis, the 2-tetrahydropyranyl group is used as a protecting group for alcohols.  Reaction of the alcohol with dihydropyran forms a<unk> yl ether, protecting the alcohol from a variety of reactions.  The alcohol can later be restored readily by acidic hydrolysis with formation of 5-hydroxypentanal.
One classic procedure for the organic synthesis of<unk>  is by hydrogenation with Raney nickel of dihydropyran.
Tetrahydropyran
Tetrahydrozoline
Hermaphrodite
Tartaric acid
Gitoformate
Sodium glycerophosphate
Hydrotalcite
Glycobiarsol