5'-O-(tert-butyldimethylsilyl)-N2-isobutyryl-3'-tritylamino-2',3'-dideoxyguanosine

Diphenyl-carbamic acid 9-[(2R,4S,5S)-5-hydroxymethyl-4-(trityl-amino)-tetrahydro-furan-2-yl]-2-isobutyrylamino-9H-purin-6-yl ester

2-amino-9-(3'-azido-2',3'-dideoxy-β-D-erythro-pentofuranosyl)-6-allylamino-9H-purine

2-amino-9-(3'-azido-2',3'-dideoxy-β-D-erythro-pentofuranosyl)-6-N-methylallylamino-9H- purine

2-amino-9-(3'-azido-2',3'-dideoxy-β-D-erythro-pentofuranosyl)-6-N-2-methyl-2-amino- propanol-9H-purine