On the structure of calonyctin A, a plant growth regulator

The plant growth regulator calonyctin A, isolated from the dried leaves of Calonyction aculeatum L. House (Yue-Guang-Hua), was separated into two pure components by high performance liquid chromatography. By use of mass spectrometry based on various ionization techniques, one- and two-dimensional NMR spectroscopy, IR spectrometry, and chemical methods the molecular structures of the two homologous glycosides were determined. Each molecule contains two hydroxy fatty acid residues and four 6-deoxyhexose units. The fatty acids are 3-hydroxy-2-methylbutanoic acid and 11-hydroxytetradecanoic acid or 11-hydroxyhexadecanoic acid. The 6-deoxyhexose residues (three of quinovose and one of rhamnose) comprise a tetrasaccharide having the following structure: [formula: see text] The long-chain hydroxy acid is linked glycosidically through its O-11 to Qui D and esterified to O-2 of Qui C, forming a macrocyclic lactone. The 3-hydroxy-2-methylbutanoic acid is ester-linked to O-3 of Qui C.