The preparation of the enantiomerically homogeneous bicyclic iodide 26 and its use as a key intermediate for the total syntheses of the cis-clerodane diterpenoids ( -)-agelasine A 5 and ( +)-(3R,4&5R,gS,9R, 10S)-3,4epoxyclerod-13-en-15,16-olide 6 are described. r'Members of the very large family of clerodane diterpenoids, 15 which share the general carbon skeleton 1, have been isolated 16 13 14 antiviral, from Collectively, been tested a wide antibiotic, exhibit the range relatively a antitumour of variety terrestrial1 small of number biological and and insect of marine' clerodanes activities, antifeedant organisms. including that prop-have 2 d7dFW 8 .-erties.'*2 However, it appears that most of the clerodanes that 5 55, 5406. 51,4941.

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Several 2-carbalkoxy-2-cyclohepten-I-ones were prepared and their Diels-Alder characteristics examined in order to develop a facile general approach to the synthesis of cycloheptane ring-containing polycyclic natural products. Substitution pattern on the seven-membered ring was found to greatly affect the Diels-Alder behavior. In addition, some extraordinary facial stereoselectivity was observed.

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