Efficient Construction of the Nucleus of Rosuvastatin Calcium

A novel and efficient five-step synthetic route, including a Biginelli reaction, dehydrogenation, chlorination, sulfonamidation, and reduction, for the core of Rosuvastatin was established. All steps were systematically studied. Tert-butylhydroperoxide aqueous solution was applied in the dehydrogenation instead of nitric acid. N,N-dimethylaniline was employed as a catalyst to accelerate the chlorination proceeding smoothly, and its catalytic mechanism is discussed. In the sulfonamidation, the conversion of compound 5 was obviously improved by use of NaH and acetonitrile. In addition, two sulfonamidation side products 6 and 7 were detected and isolated. Thus, under the optimized reaction conditions, the target product was obtained in 60.4% total yield, much higher than the reported yield (36.4%).