The indicated hydrogen is placed just in front of the parent hydride (pyran).

There are two isomers of pyran that differ by the location of the double bonds.

The name derives from its similarity to the oxygen heterocycle pyran, but the pyranose ring does not have double bonds.

Molydopterin consists of a pyranopterin, a complex heterocycle featuring a pyran fused to a pterin ring.

The term pyran is also often applied to the saturated ring analog, which is more properly referred to as tetrahydropyran (oxane).

In six-membered heterocycles such as pyran, a substituent next to an heteroatom may prefer the axial position due to the anomeric effect.

In IUPAC names, "dihydro" refers to the two added hydrogen atoms needed to remove one double bond from the parent compound pyran.

In chemistry, pyran, or oxine, is a six-membered heterocyclic, non-aromatic ring, consisting of five carbon atoms and one oxygen atom and containing two double bonds.

The reaction between C-1 and C-5 creates a molecule with a six-membered ring, called pyranose, after the cyclic ether pyran, the simplest molecule with the same carbon-oxygen ring.

These forms are called furanoses and pyranoses, respectively - by analogy with furan and pyran, the simplest compounds with the same carbon-oxygen ring (although they lack the double bonds of these two molecules).