12 Robinson annelation反応によるEremophilane類の合成

抄録

The key intermediates (2, 2a, 23) in the syntheses of eremophilane sesquiterpenes were prepared by the indirect Robinson annelation method. (1) The reaction of isocamphorquinone (1) and trans-pent-3-en-2-one in the presence of sodium alcoholate gave complex products. Five neutral and two acidic products were separated. (see Table) The neutral products were stereoisomeric 2-hydroxy-7-isopropylidene-2,4,5-trimethylbicyclo[3.3.1]nona-6,9-diones (5, 6, 7) and the Michael adducts (3, 4). And also the acidic products were 2-hydroxy-7-isopropylidene-6-oxo-2,4,5-trimethylcyclooctanoic acid (8) and its dehydrated derivative (9). The structure of these products were determined by means of chemical and spectroscopic investigations. The three bicyclo[3.3.1]nonane derivatives were transformed to octalone derivatives (2, 2a) by acid catalyzer. 2 and 2a were converted to compound 12, 15, and 17, respectively. (2) The condensation reaction of 2,3-dimethylcyclohexane-1,4-dione (19) and MVK in the presence of sodium ethylate was carried out. Theree crystalline products (20, 21, 22) were separated by column chromatography. Treatment of 20 with TsOH in benzene afforded a expected product enone (23; 80% yield) and together with a small amount of nonane derivatives (22, 24). Chemical conversion studies of some eremophilane type sesquiterpenes from the above key intermediates are in progress.