P-80 Isocyanocadineneの全合成(ポスター発表の部)

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10-Isocyano-4-cadinene (1), a marine sesquiterpene isolated from nudibranchs of the family Phyllidiidae by Okino et al., exhibits potent antifouling activity against the larvae of the barnacle Balanus amphitrite (EC_<50> 0.14μg/mL). 10-Isocyano-4-cadinene (1) is expected to be new nontoxic antifouling agents. Furthermore, the absolute stereochemistry of 1 has not been determined. To access these issues, we started the enantioselective total synthesis toward 1. The synthesis toward 1 was commenced with known imide 6, which was converted into dieneacetate 5c in 9 steps. The Diels-Alder reaction between 5c and methyl acrylate with MeAlCl_2 afforded cyclohexene 11c as a mixture of four diasereomers. This mixture was epimerized to two isomers, desired carboxylic acid 12 as a major product and ester 13, by the treatment of NaOMe followed by selective hydrolysis with 1N HCl in one-pot. Carboxylic acid 12 was transformed into aldehyde 14, which was cyclized by SmI_2-induced Barbier-type reaction to give alcohol 15. To introduce the functional groups at C10, homologation of 15 with TosMIC afforded aldehyde 16, which was treated with t-BuOK and 21 to give MPM ether 22 in stereoselective fashion. Wolff-Kishner reaction followed by Curtis rearrangement of 24 gave isocyanate 25, C10 was fully functionalized. Total synthesis was completed by reduction of isocyano group with NaBH_4 and dehydration with POCl_3. The absolute configuration of 1 was determined as (1R, 6R, 7S, 10R) by the comparison with the optical rotation between natural and synthetic samples.
天然有機化合物討論会の論文
2008-09-01

P-80 Isocyanocadineneの全合成(ポスター発表の部)

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