Lithium diisopropylamide → 3-Cyclopentyl-2-[4-(2-oxo-propylsulfonyl)-phenyl]-propionic acid ethyl ester

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A solution of the title B compound, [4-(2-oxo-propylsulfonyl)-phenyl]-acetic acid ethyl ester (8 g, 0.028 mol) in 5 mL of DMTP and 80 mL of THF is cooled to −78 g and then treated with 15 mL of LDA (2 M solution in THF/hexane, 0.030 mol). The reaction is maintained at −78° C. for 20 min and then treated with a solution of 5.91 g (0.028 mL) of cyclopentylmethyl iodide in a mixture of THF (10 mL) and DMTP (3 mL), and the reaction is maintained at −78° C. for 6 h and subsequently at RT for another 6 h. The reaction is quenched with saturated ammonium chloride solution (20 mL). The organic layer is separated and aqueous layer then extracted with ethyl acetate (2×50 mL). Both the organic layers are combined and then washed with water. The organic layer is dried over sodium sulfate, filtered and evaporated under vacuum to give a brown oil as a crude product which is purified by column chromatography over Silica gel (60-120 mesh) using 80/20—hexane/ethyl acetate as an eluent to give 3-cyclopentyl-2-[4-(2-oxo-propylsulfonyl)-phenyl]-propionic acid ethyl ester as a white solid.

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