Benzoic Acid → 5-[4-(4-(2-t-Butoxycarbonylamino-2-methoxycarbonylethyl)phenoxy)benzilidene]thiazolidin-2,4-dione

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Reaction Steps

To a solution of methyl-2-[(t-butoxycarbonyl)amino]-3-[-(4-formylphenoxy)phenyl]propanoate obtained in step (i) above in anhydrous toluene (10 g, 25 mmol), 2,4-thiazolidinedione (3.53 g, 30 mmol) was added followed by benzoic acid (0.46 g, 3.75 mmol) and piperidine (0.28 g, 3.25 mmol). The solution was heated to reflux at 145-155° C. with continuous removal of water using Dean-Stark apparatus for 5 hr. The solution was cooled to RT and the yellow solid was precipitated to afford the title compound (yield 11.9 g, 96%, purity 96.5% by HPLC, mp: 160-164° C.).

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