Total Synthesis of (-)-Silphiperfol-6-ene and (-)-Methyl Cantabradienate
作者:Nha Huu Vo、Barry B. Snider
DOI:10.1021/jo00097a053
日期:1994.9
(-)-Silphiperfol-6-ene (10) and (-)-methyl cantabradienate (11) have been prepared in seven steps from (R)-3-methyl-1-cyclopentenecarboxaldehyde in 13 and 9% overall yield, respectively. Addition of isopentenylmagnesium bromide to imine 22 afforded 65% of aldehyde 14. Oxidation provided acid 15, which was converted to ketene 20, which underwent an intramolecular [2 + 2] cycloaddition to afford cyclobutanone 13. Mn(III)-based oxidative fragmentation-cyclization of ethynyl cyclobutanol 25 provided an efficient route to the key methylenecyclopentanone 12. Addition of methyllithium and Birch reduction completed the synthesis of (-)-silphiperfol-6-ene 10. Formation of dienyl triflate 29 and palladium-catalyzed carbonylation concluded the first synthesis of (-)methyl cantabradienate (11).