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By successive treatment with lithium bistrimethylsilylamide and boron trifluoride–diethyl ether in tetrahydrofuran at –78°C optically active (Z)-dienediyne epoxide 20 prepared from D-xylose and (Z)-enol triflate 16 is found to undergo smooth cyclization to afford the title compound.
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Nakatani et al. (1992) studied this question.
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