Chemistry and Structure of Diterpenes of the Kaurane Series: III. Molecular H Complex of Isosteviol with Aniline

摘要

Individual molecular H complex of isosteviol with aniline (2:1) was isolated. The aniline NH_2 group plays the role of proton donor and the isosteviol carboxy group, acts as proton acceptor. Isosteviol molecules bound to aniline molecules form double helices about the 4_3 chiral axis. In their turn, these helices are bound to each other by hydrogen bonds between isosteviol molecules of neighboring helices, thus forming a supramolecular crystal structure of the complex. The enthalpies of formation of the hydrogen bonds in the complex were estimated. In CCl_4 solutions the complexes are in equilibrium with acid isosteviol dimers, their associates with aniline, as well as free isosteviol and aniine molecules.