Indoline is an aromatic heterocyclic organic compound with the chemical formula C8H9N. The compound is based on the indole structure, but the 2-3 bond is saturated. Indoles and their derivatives continue to inspire the development of synthetic organic chemistry even years after their discovery. The specific scaffold is a privileged structure and is ubiquitous in pharmaceuticals and biologically active compounds. Fused indolines as indole derivatives are of particular interest as they are often found in natural products and bioactives such as strychnine and tryptanthrins (alkaloids), mitosanes and mitosenes (antitumor activity) and isatisine (antiviral activity).
Cyclohexane is an organic compound with a chemical formula C6H12. It is a colorless liquid with a pungent odor, insoluble in water, and soluble in most organic solvents such as ethanol, ether, benzene, and acetone. Cyclohexyl fragments are a common structure in both natural and synthetic drugs. It can be used as both core structure and part of achiral side chain.
A spiro compound is a polycyclic compound in which two monocyclic rings share one carbon atom; the shared carbon atom is called a spiro atom. Spiro compounds have rigid structures, stable structures, and have special properties that general organic compounds do not possess, such as anomeric effect, spiro conjugation and spiro hyperconjugation. Compared with the monocyclic structure or the planar aromatic structure, the spiro structure has a larger three-dimensional structure; the heterocyclic spiro structure is also regarded as the biological isostere of some groups, which can change the drug to a certain extent. The water solubility, lipophilicity, dominant conformation and ADMET properties of the molecule make the optimized lead molecule easier to drug. Therefore, spiro compounds occupy a very important position in drug development.