A large number of diterpenoids can be classified as 4-methylcyclopentanoid derivatives, including compounds with the jatrophane, lathyrane, and tigliane (phorbol) skeletons. Three synthetic routes to 4-methylcyclopentanoids have been developed to obtain chiral, nonracemic synthons for assembly of the diterpenoids. These routes draw on the readily available monoterpenoids citronellol or pulegone as chiral resources, providing for synthesis of natural diterpenoid enantiomers without recourse to resolution. © 1990, American Chemical Society. All rights reserved.