This invention relates to a process of stereoselectively synthesizing a β-nucleoside compound of formula (I): wherein R1, R2, and B are as defined in the specification; each of R3 and R4, independently, is H or fluoro. The process includes reacting, in the presence of a transition metal salt, a tetrahydrofuran compound of formula (II): wherein R1, R2, and L are as defined in the specification, with a nucleobase derivative; and each of R3 and R4, independently, is H or fluoro.