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 LiAlH4 reagents afforded 1 highly enantioselectively (87-93% ee) in 78-97% yield, from which enantiomerically pure 1 (>99% ee) was readily obtained upon a single recrystallization.
Synthesis of the hydroxyethylene dipeptide isostere, (2S,4S,5S)-5-amino-6-cyclohexyl-4-hydroxy-2-isopropyl hexanoic acid n-butyl amide
作者:Michael A. Poss、Joyce A. Reid
DOI:10.1016/s0040-4039(00)91634-4
日期:1992.3
A stereoselectivesynthesis of the hydroxyethylenedipeptideisostere, (2S,4S,5S)-5-amino-6-cyclohexyl-4-hydroxy-2-isopropyl hexanoic acid n-butyl amide from Boc-L-phenylalanine is described.