To obtain the subject compound having advantageous antiviral activity, especially viral activity advantageous for infection with human immunological deficiency virus and hepatitis type B virus and low cytotoxicity, by not substantially including an enantiomer corresponding to a specific nucleoside compound.

This compound is (1S,4R)-cis-4-[2-amino-6-(cyclopropylamino)-9H- purin-9-yl]-2-cyclopentene-1-methanol containing <10% w/w of a corresponding enantiomer and substantially not containing the corresponding enantiomer. As a preferable production method, the compound is obtained by treating an enantiomer compound of the formula [A is cyclopentene-1-methanol-yl of (1S,4R) configuration; Z is a precursor of a group R showing cyclopropylamino or the like] with a reagent to convert the precursor group Z into the fixed group R or under conditions.