Nine-membered rings

Cyclononane is an alicyclic hydrocarbon consisting of a ring of nine carbon atoms. Its molecular formula is C9H18.

Neocarzinostatin (NCS) is a macromolecular chromoprotein enediyne antitumor antibiotic secreted by Streptomyces macromomyceticus.

Azonine is an unsaturated heterocycle of nine atoms, with a nitrogen replacing a carbon at one position. A variety of derivatives have been synthesised. It is considered to possess a considerable amount of aromatic stability. It and C9H9– are the largest monocyclic all-cis ring systems to be aromatic and close to planar. Due to a balance between angle strain (~20°) and aromaticity, a planar conformation and distorted conformation are very close in energy and the two are observable as an equilibrium mixture in the solution phase in acetone. Furthermore, the presence of substituents or nearby ca

Cyclononene is a cycloalkene with a nine-membered ring, with two possible geometric isomers, denoted cis-cyclononene and trans-cyclononene, or (Z)-cyclononene and (E)-cyclononene.

Kedarcidin is a chromoprotein antitumor antibiotic first isolated from an Actinomycete in 1992, comprising an ansa-bridged enediyne chromophore (shown) as well as an apoprotein that serves to stabilize the toxin in the Actinomycete. Like other members of the enediyne class of drugs—so named for the nine-or-ten-membered core structure bearing an alkene directly attached to two alkynyl appendages—kedarcidin was likely evolved to kill bacteria that compete with the producing organism. Because it achieves this by causing DNA damage, however, kedarcidin is capable of harming tumor cells, as well. K

Cyclononatetraene is an organic compound with the formula C9H10. It was first prepared in 1969 by protonation of the corresponding aromatic anion (described below). It is unstable and isomerizes with a half-life of 50 minutes at room temperature to via a thermal 6π disrotatory electrocyclic ring closing. Upon exposure to ultraviolet light, it undergoes a photochemical 8π electrocyclic ring closing to give .

9-Crown-3, also called 1,4,7-trioxonane or 1,4,7-trioxacyclononane, is a crown ether with the formula (C2H4O)3. A colorless liquid, it is obtained in low yield by the acid-catalyzed oligomerization of ethylene oxide.