A general method for the construction of functionalized cyclopentane derivatives 10 of high optical purity, via diastereoselective intramolecular CH insertion, is described. A methylation- retro Dieckmann dianion alkylation procedure on 10b (R= vinyl) gives 12. Decarbomethoxylation of 12 followed by thermolysis yields (+)-estrone methyl ether 1 having 91% ee.