In general, if the atoms that make up the ring contain heteroatoms, such rings become heterocycles, and organic compounds containing heterocycles are called heterocyclic compounds. An article called Negative chemical ionization mass spectrometry of nucleosides, published in 1983-09-30, which mentions a compound: 3066-84-0, Name is 8-Bromoguanine, Molecular C5H4BrN5O, Application In Synthesis of 8-Bromoguanine.
The title study, using H2/N2O mixed gas reagent, showed that each base fragment ion [b]- peak was strong, that the [m-H]- peak was weak or nonexistent, and that a significant [b + O]- ion was present. The formation of this latter in correlates with the LUMO energy of the corresponding base. A group of low mass ions, due to sugar moiety cleavages, was observed for ribonucleosides but not in 2′-deoxyribonucleosides. The neg. chem. ionization spectra of halonucleosides had prominent (often base peaks) halogen ion peaks; M- was always formed from these compounds The mechanism of neg ion production from nucleosides was discussed.
In addition to the literature in the link below, there is a lot of literature about this compound(8-Bromoguanine)Application In Synthesis of 8-Bromoguanine, illustrating the importance and wide applicability of this compound(3066-84-0).
Reference:
Tetrahydrofuran – Wikipedia,
Tetrahydrofuran | (CH2)3CH2O – PubChem