Structure of Hydroazulenoid Diterpens from a Marine Alga and Their Absolute Configuration Based on Circular Dichroism

Article abstract of DOI:10.1021/jo00255a025

First, we describe the isolation of three new diterpenoids with a hydroazulene skeleton, dictyotriol C (1), D (2) and E (3), as well as the previously known pachydictyol A (4), dictyol B (5), dictyol C (6), and dictyotadiol (7), from a Dictyota sp.The structures of the new diterpenoids 1-3 were proposed on the basis of their spectral data and confirmed by chemical transformation of dictyol B (5).This is followed by absolute configuration studies, based on the circular dichroic (CD) allylic benzoate method.The absolute stereochemistries of the new compounds as well asthat of the known dictyol B (5) and dictyotadiol (7) were determined.These absolute configurations were opposite to that reported for pachydictyol A (4).