A protected 2-deoxycytidine is purified by precipitating the protected 2-deoxycytidine represented by general formula (3) in the form of a hydrated crystal from a solution containing the protected 2-deoxycytidine and water, and by recovering the protected 2-deoxycytidine: ##STR1##

wherein R1 represents a 4-methoxytrityl, 4, 4-dimethoxytrityl, or triphenylmethyl group; and B1 represents a cytosine group having a protected amino group. The compound represented by general formula (3) is, in particular, a protected 2-deoxycytidine represented by formula (4): ##STR2##

The 2-deoxycytidine is used as a raw material for antisense DNA.