|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1998 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1997 : ¥2,600,000 (Direct Cost : ¥2,600,000)
In this research, we have carried out the systematic investigation of skeletal rearrangements of polycyclic methylenecyclobutyl ketones prepared easily by photocycloaddition of corresponding cyclic enones to allene to develop the new method for construction of functional and useful polycyclic compounds. Furthermore, in order to exemplify the utility of the method, we have also done the synthetic study of some terpenoids. Reactions of 6-4-fused ketones bearing alkyl substituents at the C6 with acids such as H2S0_4, p-TsOH, CF_3SO_3H, BF_3 OEt2, FeCl_3, AlCl_3, TiCl_4, and BCl_3 gave various kinds of products. In the cases of the methyl and ethyl derivatives, cyclooctenones were obtained mainly using TiCl_4 and BCl_3, while cyclohexenones were major products using the other acids. In the cases of isopropyl and tert-butyl derivatives, however, bicyclo[4.2.1]nonanones were formed in good yields with TiCl_4 and BCl_3, and bicyclo[4.3.0]nonanones were produced with the other acids. The difference of the reactivity toward acids may be explained by the affinity of the acid to the carbonyl group of the substrate prefer to the exo-methylene moiety. Also, the products can be divided into two groups by acid used, and the difference may be attributed to the stability of the carbocation intermediates dependent on the bridgehead substituents. Utilizing this rearrangement protocol as a key step, total syntheses of (*)-pentalenene and (*)-tetramethylmediterraneol B have been achieved. Furthermore, the synthetic study on the anticancer terpenoid taxol is in progress.