A stereoselective construction of the methylcyclopentane core (3) of jatrophane diterpenoids peditithins B-H was achieved in 14 steps from commercially available d-(+)-ribono-1,4-lactone (9). The linear 5-ene-heptanal derived from 9 was cyclized to the five-membered ring by an intramolecular carbonyl ene reaction, and five continuous stereocenters on 3 were stereoselectively introduced via a successive substrate-controlled manner, involving diastereoselective 1,4-addition, MoOPH-induced hydroxylation, and stereospecific epoxidation.