| Popis: |
A highly stereo- and enantioselective total synthesis of sarcophytol A (1), a marine cembranoid promising as a cancer chemopreventive agent, is described. The nitrile 10 obtained Z-selectively (Z:E=>35:1) by the Horner-Emmons reaction of (E,E)-farnesal (5) with the phosphononitrile 9 in 91% yield was converted to the conjugated 2(Z),4(E)-dienal 3 in which the terminal (E)-methyl group was functionalized. Intramolecular alkylation of the cyanohydrin TMS ether of 3 provided the macrocyclic ketone 2 in 79% of overall yield from 3 without isolation of the cyclic cyanohydrin 20 as well as its TMS ether 19. Reduction of 2 with several chiral LiAlH 4 reagents afforded 1 highly enantioselectively (78-97%) yield, from which enantiomerically pure 1 (>99% ee) was readily obtained upon a single recrystallization |
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