A compound represented by Formula [2]: wherein R.sub.2 and R.sub.3 each
independently represent a hydrogen atom, a halogen atom, a methoxy group,
a 2-methoxyethoxy group or a hydroxyl group; and B.sub.2 and B.sub.3 each
independently represent a nucleic acid base, or a salt thereof can be
synthesized from a compound represented by Formula [1]: wherein R.sub.1
represents a hydrogen atom, a halogen atom, a methoxy group, a
2-methoxyethoxy group, or a hydroxyl group substituted with a hydroxyl
protecting group; and B.sub.1 represents a nucleic acid base which may be
protected.