An efficient and large scale chamical synthesis of 5-aminoimidazole-4-carboxamide (AICA) 2'-deoxyriboside (5a) and its 3'-deoxyriboside 5b is described. Treatment of 3', 5'-di-O-acetyl- N 1-triphenylmethyl-2'-deoxyinosine (3a) with 5 N NaOH in EtOH, followed by anhydrous trifluoroacetic acid gave 5a in 59% yield from 2'-deoxyinosine (1a). AICA 3'-deoxyriboside (5b) was also obtained in a similar manner as for 5a in 73% yield from 3'-deoxyinosine (1b ...