To obtain an analog of BCH-189 from an inexpensive precursor.

This method comprises such processes that an allyl ester 1 or ester is ozonized to produce an aldehyde 2, the aldehyde 2 produces a lactone 3 by reacting with thioglycolic acid, the lactone 3 is treated with a reducing agent: e.g. diisobutylaluminum hydride(DIBAL), sodium bis(2-methoxyethoxy) aluminum hydride (called 'Red-Al'TM, available as a 3.4 mol toluene solution on the market), NaBH4; followed by being treated with a carboxylic anhydride to produce a carboxylate 4, and then the resultant product is coupled with a pyrimidine base in the presence of a Lewis acid to produce the β isomer of a substituted nucleoside 5, essentially β/α isomer in the proportion of 100:0, and the objective BCH-189 or analog thereof 6 is produced by deprotecting the substituted nucleoside 5.