NOVELTY - An adefovir dipivoxil drug is synthesized by suspending p-formaldehyde into 2-chloroethanol, adding anhydrous sodium sulfate into organic layer, distilling, and collecting distillate to obtain 1-chloro-2-chloromethoxy ethane colorless liquid; heating, dripping triisopropyl phosphite, reacting for 3-6 hours to obtain yellow liquid, distilling, and collecting distillate to obtain intermediate 2-chloroethoxy methyl isopropyl phosphite; and adding adenine and alkaline catalyst into organic solvent, distilling to remove solvent, and recrystallizing.    USE - Method for synthesizing adefovir dipivoxil drug (claimed).    ADVANTAGE - The method is simple with easy operation, safe, and environment friendly; and has moderate reaction conditions, low cost and high purity.    DETAILED DESCRIPTION - Synthesis of adefovir dipivoxil drug involves:    (A) suspending p-formaldehyde (1000-3000 mol) into 2-chloroethanol (1000-3000 mol) at less than 10 degrees C in the presence of dry hydrochloric acid (HCl) gas, setting aside, adding anhydrous sodium sulfate into organic layer, distilling, and collecting distillate at 78-84 degrees C under 40.64 kPa to obtain 1-chloro-2-chloromethoxy ethane colorless liquid;    (B) adding 1-chloro-2-chloromethoxy ethane (500-2000 mol), heating at 90 degrees C, dripping triisopropyl phosphite (550-2200 mol) for 2.5-3 hours at 125-130 degrees C, reacting for 3-6 hours to obtain yellow liquid, distilling, and collecting distillate at 160-175 degrees C under 40.64 kPa to obtain intermediate 2-chloroethoxy methyl isopropyl phosphite;    (C) adding adenine (500-1200 mol) and alkaline catalyst (1005-2412 mol) into organic solvent (600-1500 L) with boiling point greater than 110 degrees C, raising temperature at 100-110 degrees C, dripping 2-chloroethoxy methyl isopropyl phosphite (575-1380 mol), reacting for 5-8 hours, recovering organic solvent, refluxing, extracting, collecting organic layer, distilling to remove solvent, and recrystallizing to obtain 9-(2-diisopropoxyphosphorylmethoxyethyl)adenine white crystals;    (D) adding 9-(2-diisopropoxyphosphorylmethoxyethyl)adenine (50-100 kg) and catalyst (5-20 kg) into polar non-protonic organic solvent at room temperature, dripping trimethylchlorosilane (60-130 kg), reacting for 5-7 hours, distilling to recover solvent, separating and purifying to obtain adefovir refined product;    (E) adding adefovir (150-400 mol) and catalyst (90-250 kg) into strongly polar non-protonic solvent (200-500 L), dripping chloromethyl tertvalerate (375-1000 mol) at 60 degrees C, reacting for 3-5 hours, cooling to 40 degrees C, adding ethyl acetate (600-2000 L), blending for 1-2 hours, precipitating white solid, and filtering to obtain adefovir bistertvaleryloxymethyl ester crude product; and    (F) dissolving into ethyl acetate, dripping 2-15C fatty ether or petroleum ether, precipitating white crystals, filtering, washing crystals with acetone-ether at volume ratio of 1:4, pump drying to obtain adefovir bistertvaleryloxymethyl white solid, and vacuum-drying at 40 degrees C to obtain adefovir bistertvaleryloxymethyl pure product.