9.4 g of 1-(4-nitrobenzyl) hydrogen 2(R)-isobutylsuccinate were dissolved in 30 ml of dry diethyl ether and the solution was cooled in a dry-ice/acetone bath. There were then added 70 ml of isobutene, followed dropwise by 0.64 ml of concentrated sulfuric acid. The reaction flask was tightly topped and the mixture was stirred at room temperature for 2 days. The mixture was made basic with saturated sodium hydrogen carbonate solution and water was added. The organic phase was separated and the aqueous phase was extracted twice more with diethyl ether. The combined ethereal phases were washed with water and saturated sodium chloride solution, dried over anhydrous sodium sulfate and evaporated to give 8.8 g (77%) of 4-tert.butyl 1-(4nitrobenzyl) 2(R)-isobutylsuccinate in the form of an oil. Rf (System A) 0.87.
