Heterocycle in the context of "Bicyclic molecule"

Coumarin (/ˈkuːmərɪn/) or 2H-chromen-2-one is an aromatic organic chemical compound with formula C₉H₆O₂. Its molecule can be described as a benzene molecule with two adjacent hydrogen atoms replaced by an unsaturated lactone ring −(CH)=(CH)−(C=O)−O−, forming a second six-membered heterocycle that shares two carbons with the benzene ring. It belongs to the benzopyrone chemical class and is considered a lactone.

Coumarin is a colorless crystalline solid with a sweet odor resembling the scent of vanilla and a bitter taste. It is found in many plants, where it may serve as a chemical defense against predators. While coumarin is not an anticoagulant, its 3-alkyl-4-hydroxy derivatives, such as the fungal metabolite dicoumarol, inhibit synthesis of vitamin K, a key component in blood clotting. A related compound, the prescription drug anticoagulant warfarin, is used to inhibit formation of blood clots, deep vein thrombosis, and pulmonary embolism.

A deoxyribonucleotide is a nucleotide that contains deoxyribose. They are the monomeric units of the informational biopolymer, deoxyribonucleic acid (DNA). Each deoxyribonucleotide comprises three parts: a deoxyribose sugar (monosaccharide), a nitrogenous base, and one phosphoryl group. The nitrogenous bases are either purines or pyrimidines, heterocycles whose structures support the specific base-pairing interactions that allow nucleic acids to carry information. The base is always bonded to the 1'-carbon of the deoxyribose, an analog of ribose in which the hydroxyl group of the 2'-carbon is replaced with a hydrogen atom. The third component, the phosphoryl group, attaches to the deoxyribose monomer via the hydroxyl group on the 5'-carbon of the sugar.

When deoxyribonucleotides polymerize to form DNA, the phosphate group from one nucleotide will bond to the 3' carbon on another nucleotide, forming a phosphodiester bond via dehydration synthesis. New nucleotides are always added to the 3' carbon of the last nucleotide, so synthesis always proceeds from 5' to 3'.

Imidazole (ImH) is an organic compound with the formula (CH)₃(NH)N. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. It can be classified as a heterocycle, specifically as a diazole.

Many natural products, especially alkaloids, contain the imidazole ring. These imidazoles share the 1,3-C₃N₂ ring but feature varied substituents. This ring system is present in important biological building blocks, such as histidine and the related hormone histamine. Many drugs contain an imidazole ring, such as certain antifungal drugs, the nitroimidazole series of antibiotics, and the sedative midazolam.

In organometallic chemistry, a sandwich compound is a chemical compound featuring a metal bound by haptic, covalent bonds to two arene (ring) ligands. The arenes have the formula C_nH_n, substituted derivatives (for example C_n(CH₃)_n) and heterocyclic derivatives (for example BC_nH_n+1). Because the metal is usually situated between the two rings, it is said to be "sandwiched". A special class of sandwich complexes are the metallocenes.

The term sandwich compound was introduced in organometallic nomenclature in 1956 in a report by J. D. Dunitz, L. E. Orgel and R. A. Rich, who confirmed the structure of ferrocene by X-ray crystallography. The correct structure, in which the molecule features an iron atom sandwiched between two parallel cyclopentadienyl rings, had been proposed several years previously by Robert Burns Woodward and, separately, by Ernst Otto Fischer. The structure helped explain puzzles about ferrocene's conformers. This result further demonstrated the power of X-ray crystallography and accelerated the growth of organometallic chemistry.