The reaction of methyl D-ribofuranoside (I) with SOCl2 gives methyl 5-chloro-5-deoxy-2,3-O-sulfinyl-D-ribofuranoside (II), which is treated with ammonia to yield methyl 5-chloro-5-deoxy-D-ribofuranoside (III). The reaction of (IV) with benzoyl chloride and pyridine affords the dibenzoate (IV), which is treated with lithium azide in DMF to provide the 5'-azido derivative (V). The condensation of 3-iodo-1H-pyrazolo[3,4-d]pyrimidine-4-amine (VII) (prepared by iodination of (1H-pyrazolo[3,4-d]pyrimidine-4-amine (VI) with N-iodosuccinimide (NIS)) with the azido derivative (V) by means of BF3/Et in nitromethane gives the adduct (VIII), which is debenzoylated with sodium methoxide yielding the azido nucleoside (IX). Finally this compound is reduced with triphenylphosphine and ammonia to furnish the target 5'-amino-nucleoside.

The iodination of 1H-pyrazolo[3,4-d]pyrimidine-4-amine (I) with N-yodosuccinimide (NIS) gives 3-iodo-1H-pyrazolo[3,4-d]pyrimidine-4-amine (II), which is condensed with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose (III) by means of BF3/ethyl ether in nitromethane to yield the benzoylated adduct (IV). Finally this compound is deprotected with sodium methoxide.

The reaction of methyl D-ribofuranoside (I) with SOCl2 gives methyl 5-chloro-5-deoxy-2,3-O-sulfinyl-D-ribofuranoside (II), which is treated with ammonia to yield methyl 5-chloro-5-deoxy-D-ribofuranoside (III). The reaction of (IV) with benzoyl chloride and pyridine affords the dibenzoate (IV), which is treated with lithium azide in DMF to provide the 5'-azido derivative (V). The condensation of 3-iodo-1H-pyrazolo[3,4-d]pyrimidine-4-amine (VII) (prepared by iodination of (1H-pyrazolo[3,4-d]pyrimidine-4-amine (VI) with N-iodosuccinimide (NIS)) with the azido derivative (V) by means of BF3/Et in nitromethane gives the adduct (VIII), which is debenzoylated with sodium methoxide yielding the azido nucleoside (IX). Finally this compound is reduced with triphenylphosphine and ammonia to furnish the target 5'-amino-nucleoside.

The reaction of methyl D-ribofuranoside (I) with SOCl2 gives methyl 5-chloro-5-deoxy-2,3-O-sulfinyl-D-ribofuranoside (II), which is treated with ammonia to yield methyl 5-chloro-5-deoxy-D-ribofuranoside (III). The reaction of (IV) with benzoyl chloride and pyridine affords the dibenzoate (IV), which is treated with lithium azide in DMF to provide the 5'-azido derivative (V). The condensation of 3-iodo-1H-pyrazolo[3,4-d]pyrimidine-4-amine (VII) (prepared by iodination of (1H-pyrazolo[3,4-d]pyrimidine-4-amine (VI) with N-iodosuccinimide (NIS)) with the azido derivative (V) by means of BF3/Et in nitromethane gives the adduct (VIII), which is debenzoylated with sodium methoxide yielding the azido nucleoside (IX). Finally this compound is reduced with triphenylphosphine and ammonia to furnish the target 5'-amino-nucleoside.