Finnegan, Henderson, Farabow, Garrett & Dunner, L.L.P.
Nucleoside derivatives and process for preparing thereof
 Nucleoside derivatives represented by formula (I); ##STR1## wherein, R.sub.1 represents hydrogen, phosphate or phosphonate group, R.sub.2 represents substituted or unsubstituted pyrimidine or purine base, and Z represents S, SO, SO.sub.2, O or C; or pharmaceutically acceptable salts thereof. Compound (I) can be obtained by reacting a compound of the formula (II); ##STR2## wherein, R.sub.7 represents hydrogen or hydroxy-protecting group, L represents aromatic or nonaromatic acyl, halide or alkoxy, and Z represents S, SO, SO.sub.2, O or C, with a base. 
Chong Kun Dang Corp.
C A C A Y C C C
C07D A61P C07H A61P Y02P C07D C07D C07H
inventional inventional inventional inventional additional inventional inventional inventional
Koo Hun Soon Kil Chong Ryul Jung Woo Byeong Seon Kyung Hoi Hoe Joo Kyeong Bok Sung Jo
Chung Ahn Lee Kim Jeong Cha Son Min Choi