Isoalloxazine

Isoalloxazine is the structural foundation of flavins such as riboflavin (vitamin B2) and is a heterocyclic compound.^[2] It has a tricyclic structure which means it has three interconnected rings of atoms and is a tautomer of alloxazine.^[1] The structure is formed by primary-secondary aromatic o-diamines and they are a high-melting crystalline substance.^[1] The R-group is used to attach various flavin groups It has a similar structure to pteridines which has two interconnected rings.^[1] Isoalloxazine was first obtained in 1934^[1] by Richard Kuhn an Austrian-German biochemist and lab mates.

Isoalloxazine Structure

Isoalloxazine

Names
IUPAC name 1H-benzo[g]pteridine-2,4-dione
Other names 1,2,3,4-Tetrahydrobenzopteridine-2,4-dione; Benzo(g)pteridine-2,4(1H,3H)-dione
Identifiers
CAS Number	490-59-5
3D model (JSmol)	Interactive image
Beilstein Reference	85819
ChEBI	CHEBI:37325
ChEMBL	ChEMBL68500
ChemSpider	4522915
ECHA InfoCard	100.007.014
EC Number	207-714-3
IUPHAR/BPS	456
PubChem CID	5372720
UNII	880W3VF9YW
CompTox Dashboard (EPA)	DTXSID50197656
InChI InChI=1S/C10H6N4O2/c15-9-7-8(13-10(16)14-9)12-6-4-2-1-3-5(6)11-7/h1-4H,(H2,12,13,14,15,16) Key: HAUGRYOERYOXHX-UHFFFAOYSA-N
SMILES C1=CC=C2C(=C1)N=C3C(=N2)NC(=O)NC3=O
Properties
Chemical formula	C10H6N4O2
Molar mass	214.184 g·mol−1
Appearance	Red solid
Melting point	200 °C (392 °F; 473 K)[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Isoalloxazine ring

Isoalloxazine rings can exist in different redox and ionization states depending on the chemistry of FMN and FAD associated with it.^[3] Using the redox-active isoalloxazine system, FAD and FMN are able to do one and two electron transfer reactions and also be coupled with proton transfers.^[4]

Ionization and redox states of the isoalloxazine ring