TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The organic solvent is dichloromethane, toluene, 1,2-dichloroethane, tetrahydrofuran and/or 2-methyltetrahydrofuran. Molar ratio between the reducing agent and (II) or (IIa) is 1.1-3, and molar ratio of lithium chloride and/or lithium bromide to (II) or (IIa) is 0.1-2. Preferred Method: The reaction temperature is -78 to 100 degrees C, preferably -20 to 40 degrees C. Preparation of (II) and (IIa), comprises carrying out Tamao-Fleming oxidation reaction of (III) or (IIIa) in a solvent. The Tamao-Fleming oxidation reaction comprises carrying out oxidation of (III) or (IIIa) in presence of an oxidizing agent in a solvent under action of a base and a fluorinating reagent, where the solvent is water, methanol, tetrahydrofuran, ethanol and/or N,N-dimethylformamide, the base is triethylamine, diisopropylethylamine, potassium bicarbonate, sodium bicarbonate and/or cesium bicarbonate, molar ratio between the base and (III) or (IIIa) is 0.5-30, the oxidizing agent is hydrogen peroxide, peracetic acid, tert-butyl hydroperoxide, m-chloroperoxybenzoic acid, chlorine gas, bromine, iodine, N-chlorosuccinimide, N-bromosuccinimide and/or N-iodosuccinimide, hydrogen peroxide concentration is 1-60 wt.%, molar ratio between the oxidizing agent and (III) or (IIIa) is 0.8-30, the fluorinating agent is sodium fluoride, cesium fluoride, potassium fluoride, hydrogen fluoride and/or boron trifluoride, molar ratio between the fluorinating agent and (III) or (IIIa) is 0.8-30, and Tamao-Fleming oxidation reaction temperature is -20 to 120 degrees C. Preparation of (III) or (IIIa), comprises carrying out hydrolysis reaction of (1R,3S)-3-(2-amino-6-oxo-1H-purin-9(6H)-yl)-2-methylenecyclopentanecarboxylate compounds of formula (V) or their tautomers of formula (Va) in a solvent under action of a protonic acid, where the solvent is an organic solvent and/or water, the organic solvent is dichloromethane, 1,2-dichloroethane, tetrahydrofuran, 2-methyltetrahydrofuran, acetonitrile, methanol, ethanol, isopropanol, toluene and/or tert-butyl methyl ether, the protonic acid is hydrochloric acid, sulfuric acid, trifluoroacetic acid, nitric acid, methanesulfonic acid and/or trifluoromethanesulfonic acid, molar ratio between the protonic acid and (V) or (Va) is 0.1-20, and the reaction temperature is -20 to 80 degrees C.R2 = cyclic silane group of formula (VI); andR3 = pyridyl or 6-10C aryl (both optionally substituted with 1-3C alkyl, halo or 1-3C alkoxy), preferably pyridin-2-yl, pyridin-3-yl, pyridin-4-yl, naphthyl, 2-fluorophenyl, 3-fluorophenyl, 4-fluorophenyl, naphthalen-2-yl, 2-chlorophenyl, 3-chlorophenyl, 4-chlorophenyl, biphenyl-3-yl, o-tolyl, m-tolyl, p-tolyl, biphenyl-2-yl, 4-methoxyphenyl, 3-methoxyphenyl, 2-methoxyphenyl or biphenyl-4-yl.Provided that: cyclic silane and heterocyclic silane are monocyclic rings or fused rings; X is C when n is 0, and Y2 is C when p is 0. Preferred Definitions:    R = methyl.