272778-12-8

75-77-4

189028-95-3

272778-12-8

Step (c): In a 500 ml three-necked round-bottomed flask, assemble a thermometer, dosing funnel and nitrogen inlet. To the flask was added a dichloromethane solution of Compound VIII (28.1 mmol as 10 g of Compound VIII) and Compound IX (12.05 g) from step (b), and the total volume of the reaction mixture was adjusted to 150 mL with dry dichloromethane.The mixture was cooled to -10 °C and N,N-diisopropylethylamine (DIPEA, 25.7 mL, 147.5 mmol), keeping the temperature at -10 °C. Subsequently, trimethylchlorosilane (3.4 mL, 30.8 mmol) was added slowly, keeping the reaction temperature at -10 °C. Stirring of the reaction mixture was continued for 2 hours. Upon completion of the reaction, the organic layer was separated and washed with 120 mL of water. The organic layer was concentrated to a smaller volume, bis(trimethylsilyl)acetamide (8.4 mL) was added and the mixture was heated to reflux for 30 minutes. The mixture was concentrated to remove the dichloromethane and the product was obtained by crystallization from a mixture of ethyl acetate and heptane. After filtration, washing and drying, 13 g of Compound III was obtained (65% yield based on Compound VIII).