Antiviral compounds. 3. The preparation of some diketophosphonates derived from sugars

3-[2',4'-O-benzylidene-3',5'-di'O-benzoyl-D-ribosylidene]2,4-pentanedione 3 and 3[2',4': 3',5'-di-O-benzylidene-D-ribosylidene]2,4-pentanedione 5 were converted by reaction with trimethyl phosphate to diketophosphonates 4 and 6 respectively. While compound 4 showed antiviral activity similar to 3 with lower toxicity, compound 6 was devoid of antiviral activity as well as cytotoxicity.