A short, high-yield, stereoselective synthesis of racemic exo- and endo-brevicomin
Abstract
Stereoselective reduction and cyclization of 6-methyl-2-propionyl-2,3-dihydro-4H-pyran provides brevicomin in quantitative yield as a 86:14 or a 17:83 mixture of exo and endo isomers through DIBAH reduction in ether at reflux or Zn(BH4)2 in the presence of ZnCl2 in ether at 0 °C, respectively.