Laurencia sesquiterpenes, synthesis

Laurene is a sesquiterpene isolated from marine red algae Laurencia elate. It possesses an exo-methylenecyclopentane core with two contiguous stereocenters, one of which is quaternary (Scheme 8.8). Fukumoto et al. reported the enantioselective synthesis of (-l-)-laurene by ring-expansion of 1-vinylcyclobutanol induced by an electrophilic palladium(II) catalyst [28]. 

Li et al. ° developed a method for the stereoselective formation of l-oxaspiro[4.4]nonanes, which was employed in the synthesis of laurentristich-4-ol, one of the 14 sesquiterpenes isolated from the red alga Laurencia tristicha in the South Sea of China. Thus, benzofuran 133 was treated with Sml2 and HMPA to afford spirocycle 134 in 65% yield as a single stereoisomer (Scheme 25.64). 

Greene, A.E., Coelho, F., Barreiro, E.J., and Costa, P.R.R. (1986) A selective synthesis of brasilenol, a novel sesquiterpene from the sea hare Aplysia brasiliana and the red alga Laurencia obtusa. J. Org. Chem., 51, 4250-4253. 

Gonzalez, A.G., Martin, J.D., Perez, C., Ramirez, M.A., and Ravelo, F. (1980) Total synthesis of 8-desoxy-isocaespitol a new polyhaloge-nated sesquiterpene from Laurencia caespitosa. Tetrahedron Lett., 21, 187-188. 

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