Rosane lactones

The tricyclic alcohol (130) is an intermediate in the synthesis of rimuene. Hydroboronation of its tetrahydropyranyl ether and then oxidation with iodine and lead tetra-acetate afforded the 6—18 ether which could be cleaved and oxidized to a keto-acid. Such derivatives might form suitable intermediates for the synthesis of the rosane lactones. O-MethyI-14-methyl podocarpic acid has been synthesized "" by a conventional ring a + ring c route. 

Herz, W., S.V. Govindan, and J.F. Blount Tetracyclic analogues of the rosane lactones from Eupatorium album. J. Org. Chem. 44, 2999 (1979). 

The occurrence of the rosane lactones e.g., 249) raises the interesting question of whether a carbonium ion intermediate (248, R = CO2H) is neutralized by lactonization immediately following the shift of the methyl group from Cio to C9. If so, oxidation of the methyl group would obviously have to precede cyclization. Separate incorporation of mevalonate bearing tritium at positions 4 and 5 into rosenonolactone... 

Bohimann, F., Zdero, C., Jakupovic, J., Gerke, T., Wallmeyer, M., King, R. M., and Robinson, H. (1984). New sesquiterpene lactones and rosane derivatives from Trichogonia species. Liebigs Ann. Chem. 162-185. 

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