| Research Abstract |
Clerodanes constitute a large class of diterpenoids, and display unique biological activities among which the insect antifeedant represented by clerodin is well known. The most important characteristic in this class is four contiguously arranged chiral centers ; C (5) -C (10) -C (9) -C (8), in a molecule.
To synthesize these clerodane natural products, we have accomplished stereocontrolled preparation of two kinds of key-intermediates ; (3S,4R,4aS,8S,8aR) -7,7-ethylenedioxy-3,4,8,8a-tetramethyl-4-vinyl-3,4,4a, 5,6,7,8,8a-octahydronaphthalen-2 (1H) -one 1 and (3S,4R,4aS,8aR) -3,4,8,8a-tetramethyl-4-vinyl-3,4,4a, 5,6,8a-hexahydronaphthalen-2 (1H) -one2, which possess correctly arranged four chiral centers, necessary for the enantioselective synthesis of neo-trans-clerodanes.
The acetal and ketone functions would serve as a clue for construction of oxygenated A and B rings. In addition, as a vinyl group is equivalent to the synthetically versatile ethanal moiety, installment of this function in 1 and 2 could be useful for construction of a six-carbon substituent at the C(9) position in the clerodane-synthesis.
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