Pyrimidine, also known as 1,3-diazobenzene, is a heterocyclic compound with the chemical formula C4H4N2. Pyrimidine is formed by substituting 2 nitrogen atoms for 2 carbons in the meta-position of benzene. It is a diazine and retains its aromaticity. Derivatives of pyrimidine widely exist in organic macromolecular nucleic acids, and many drugs also contain pyrimidine rings. In nucleic acids, three nucleobases are pyrimidine derivatives: cytosine, thymine and uracil. There are a variety of pyrimidine-containing drugs on the market, most of which are kinase inhibitors.
Dioxolane is a heterocyclic acetal with the formula (CH2)2O2CH2. It is related to tetrahydrofuran by exchanging an oxygen for the CH2 group. The isomer 1,2-dioxolane (in which the two oxygen centers are adjacent) is a peroxide. 1,3-Dioxolane is used as solvent and comonomer in polyacetal. The dioxolane-type and their hydrogenolysis can provide very valuable partially protected building blocks either for oligosaccharide syntheses or sugar transformations.