A short, regiospecific and first synthesis of (+)-galanolactone 5 and (+)labdienedial I I was achieved from sclareol, respectively. Β© 1997 Elsevier Science Ltd.
Galanolactone $ and (+)-(~-8(17), 12-1abdiene-15, 16-dial 1 1, new labdane-type diterpenes were isolated from Alpinia galanga by Morita et. al I and show cytotoxic, antifungal activities. Recently $ also shows anti-5-HT (serotonin) effect. 2 No information is available on the synthesis of optically active galanolactone 5 and labdienedial 1 1. Only total synthesis of galanolactone 5 as racemic form in multiple steps from geraniol was reported by Its typical structure of epoxide and ct, ~ unsaturated lactone of galanolactone 5 is commonly found in insect antifeedant natural products such as azadirachtin 4 isolated from the seeds of the neem, and ajugarin, 5 etc. Interesting biological activities, natural scarcity ( 0.002 % for $ and 0.01% for 1 1, respectively) and labdane-type structure of 5 as a model for new agrochemicals prompted us to synthesize optically active galanolactone 5 and its related compounds. We report in this letter a short, regiospecific and first synthesis of (+)-galanolactone 5, (-)-8-epi-galanolactone 6 and (+)-labdienedial