NOVELTY - Synthesis of 1-ethoxycarbonyl-5-methyl-(3R)-tert-butyldimethylsilyloxy glutarate involves adding methanol to (R)-(-)-4-cyano-3-hydroxybutyric acid, cooling, reacting resultant product for 5-10 hours, drying, distilling to obtain (R)-(+)-3-hydroxymonomethyl glutarate, adding dichloromethane, imidazole and t-butyldimethylchlorosilane, reacting, adding aqueous sodium bicarbonate, filtering, distilling to obtain methyl tert-butyldimethylsilyl-(R)-3-((tert-butyldimethylsilyl)oxy)glutarate, adding dichloromethane and organic base, reacting, drying and concentrating.    USE - Synthesis of 1-ethoxycarbonyl-5-methyl-tert-butyldimethylsilyloxy glutarate used as intermediate for preparing rosuvastatin (claimed).    ADVANTAGE - The method provides 1-ethoxycarbonyl-5-methyl-tert-butyldimethylsilyloxy glutarate by environmentally-friendly and economical process.    DETAILED DESCRIPTION - Synthesis of 1-ethoxycarbonyl-5-methyl-(3R)-tert-butyldimethylsilyloxy glutarate involves adding methanol as solvent to (R)-(-)-4-cyano-3-hydroxybutyric acid, cooling the resultant product to -5 degrees C to 10 degrees C, stirring the resultant product, purging dry hydrogen chloride, reacting the resultant product for 5-10 hours, extracting the resultant product with dichloromethane, drying the resultant product using anhydrous sodium sulfate, filtering, distilling the resultant product under reduced pressure to obtain (R)-(+)-3-hydroxymonomethyl glutarate, adding dichloromethane as solvent, imidazole and t-butyldimethylchlorosilane, reacting the resultant product at 20-50 degrees C for 5-10 hours, adding 5-10 %mass aqueous sodium bicarbonate, drying organic phase using anhydrous sodium sulfate, filtering, distilling to obtain methyl tert-butyldimethylsilyl-(R)-3-((tert-butyldimethylsilyl)oxy)glutarate, then adding dichloromethane as solvent and organic base, reacting the resultant product at -5 degrees C to 10 degrees C, dripping ethyl chloroformate, reacting the resultant product for 5-10 hours, adding ethyl acetate and saturated brine, drying the resultant product using anhydrous sodium sulfate, and concentrating the resultant product under reduced pressure. The mass ratio of methanol and (R)-(-)-4-cyano-3-hydroxybutyric acid is 5-10:1. The molar ratio of hydrogen chloride and (R)-(-)-4-cyano-3-hydroxybutyric acid is 2-3:1. The molar ratio of imidazole and (R)-(+)-3-hydroxymonomethyl glutarate is 2-3:1. The molar ratio of t-butyldimethylchlorosilane and (R)-(+)-3-hydroxymonomethyl glutarate is 2-3:1. The molar ratio of methyl tert-butyldimethylsilyl-(R)-3-((tert-butyldimethylsilyl)oxy)glutarate and organic base is 1:1-2. The molar ratio of methyl tert-butyldimethylsilyl-(R)-3-((tert-butyldimethylsilyl)oxy)glutarate and chloro carbonic acid monomethyl ester is 1:1-2.