4(R)-(6-chloro-9H-purin-9-yl)-2(R)-(tert-butyldiphenylsilyloxymethyl)tetrahydrofuran-3(S)-ol

2(R)-(tert-butyldimethylsilyloxymethyl)-4(R)-(5-amino-6-chloro-4-pyrimidylamino)tetrahydrofuran-3(S)-ol