Isocytosine

Isocytosine or 2-aminouracil is a pyrimidine base that is an isomer of cytosine. It is used in combination with isoguanine in studies of unnatural nucleic acid analogues of the normal base pairs in DNA.^[1] In particular, it is used as a nucleobase of hachimoji RNA.^[2]

Isoguanine-Isocytosine-base-pair

Isocytosine

Names
Preferred IUPAC name 2-Amino-3H-pyrimidin-4-one
Other names 2-Aminouracil
Identifiers
CAS Number	108-53-2 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:55502 Y
ChEMBL	ChEMBL56260 Y
ChemSpider	60309 Y
ECHA InfoCard	100.003.266
PubChem CID	66950
CompTox Dashboard (EPA)	DTXSID00148350
InChI InChI=1S/C4H5N3O/c5-4-6-2-1-3(8)7-4/h1-2H,(H3,5,6,7,8) Y Key: XQCZBXHVTFVIFE-UHFFFAOYSA-N Y InChI=1/C4H5N3O/c5-4-6-2-1-3(8)7-4/h1-2H,(H3,5,6,7,8) Key: XQCZBXHVTFVIFE-UHFFFAOYAD
SMILES O=C1/C=C\N=C(\N)N1
Properties
Chemical formula	C4H5N3O
Molar mass	111.104 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

It can be synthesized from guanidine and malic acid.^[3]

Synthesis of isocytosine from malic acid

It is also used in physical chemical studies involving metal complex binding, hydrogen bonding, and tautomerism and proton transfer effects in nucleobases.^[4]

Tautomerism of isocytosine

References

1. "Isocytosine". Molecule of the Week. American Chemical Society. Retrieved November 1, 2012.
2. Hoshika, Shuichi; et al. (22 February 2019). "Hachimoji DNA and RNA: A genetic system with eight building blocks". Science. 363 (6429): 884–887. doi:10.1126/science.aat0971. PMC 6413494. PMID 30792304.
3. William T. Caldwell , Harry B. Kime (1940). "A New Synthesis of Isocytosine". J. Am. Chem. Soc. 62 (9): 2365–2365. doi:10.1021/ja01866a028.
4. "Isocytosine". Sigma-Aldrich. Retrieved November 1, 2012.