An alternative synthesis of 9-(5,6-dideoxy-~-D-ribo-hex-5-ynofuranosyl)adenine (5), which is known to be a potent, irreversible, and time-dependent inhibitor of AdoHcy hydrolase, has been accomplished. Compound 5 had a potent antiviral activity against influenza A and B viruses as well as vesicular stomatitis virus. Since the usual inhibitors of AdoHcy hydrolase, such as neplanocin A, are inactive on both influenza viruses, the mechanism of action of 5 would be different from that of known AdoHcy hydrolase inhibitors.