[CH2:1]([C@H:5]([CH2:19][C:20]([O:22][C:23]([CH3:26])([CH3:25])[CH3:24])=[O:21])[C:6]([O:8]CC1C=CC([N+]([O-])=O)=CC=1)=[O:7])[CH:2]([CH3:4])[CH3:3]>C(OCC)(=O)C.[Pd]>[CH2:1]([C@H:5]([CH2:19][C:20]([O:22][C:23]([CH3:25])([CH3:24])[CH3:26])=[O:21])[C:6]([OH:8])=[O:7])[CH:2]([CH3:4])[CH3:3]4.4 g of 4-tert.butyl 1-(4-nitrobenzyl) 2(R)-isobutylsuccinate were dissolved in 50 ml of ethyl acetate and hydrogenated for 3.5 hours at room temperature and atmospheric pressure in the presence of 0.6 g of 5% palladium/carbon. The catalyst was removed by filtration and the solution was extracted three times with cold 2N hydrochloric acid. The organic layer was then washed with water and saturated sodium chloride solution and dried over anhydrous sodium sulfate. The solvent was removed by evaporation and the crude product was purified by chromatography on silica gel using chloroform for the elution. 2.0 g (72%) of 4-tert.butyl hydrogen 2(R)-isobutylsuccinate were obtained in the form of an oil. Rf (System C) 0.65.
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