39 Diterpeneに於ける骨格の変換

抄録

Although large amounts of 1-abietic acid (1) are readily available from many kinds of common japanese pine tree, the acid itself has not remarkable physiological activities. However, many natural diterpenoids, such as gibberellin and diterpenoid alkaloid, closely related to (1) have been widely known as noticeable substance. Accordingly, studies on chemical conversion of (1) to the useful compounds have been undertaken in our laboratory. In this report, abietic acid skeleton is transformed into compounds (9) and (46), regarded as the basic structure of gibberellin and aconitine type alkaloid respectively. A synthesis of c-homohydrofluorene (9) has been realized by opening and successive ring closure of B/C-ring juncture of Δ^<8,9>-unsaturated ester (4) prepared from (1). Furthermore, a standard trans-A/B-ring hydrofluorene (30) is synthesized from (9). In comparison with this standard, structures of hydrofluorene (36), (38) and (39) previously prepared by alkaline treatment of cis-diketo ester (32) have been confirmed to have cis-A/B-ring fusion. Otherwise, stereochemical analysis on catalytic hydrogenation of unsaturated hydrofluorene (37) and (41) is also carried out. Successively, Δ^<8,9>-unsaturated ether (43) obtained from epoxy compound (42) was treated as in previous ring construction. Under the sterical influence of the ether bridge, the condensation of the diketo ether (45) lead to afford an aconitine type skeleton, which is in contrast to the previous case.