The reaction of l-(5-deoxy-2,3-0-isopropylidene-i?-D-eryf/zro-pent-4-enofuranosyl)uracil (1) with iodine fluoride in methylene chloride leads to the stereospecific formation of 5'-deoxy-4'-fluoro-5'-iodo-2',3'-0-isopropylideneuridine (4a) in almost quantitative yield. The 5'-iodo function of 4a can be converted into the analogous 5'azido derivative (5a) by vigorous treatment with lithium azide in dimethylformamide. Treatment of 5a with nitrosyl tetrafluoroborate leads to the isolation of 2,5,-anhydro-4'-fluoro-2,,3,-0-isopropylideneuridine (6a) which can be readily hydrolyzed to 4'-fluoro-2,,3'-0-isopropylideneuridine (7a). The latter compound has been converted into 4'-fluoro-5,-0-sulfamoyluridine (8b), the uracil analogue of nucleocidin, by treatment with sulfamoyl chloride followed by mild acidic hydrolysis. The synthesis of 4'-fluorouridine '-phosphate (8d] has also been achieved via conversion of 7a to its bis(2,2,2-trichloroethyl)phosphate ester followed by careful removal of protecting groups. The unusual stabilities of 4'-fluorouridine derivatives are discussed. In addition, it has been shown that treatment of 2',3'-methoxymethylene-and 2',3'-methoxyethylideneuridine derivatives with nitrosyl tetrafluoroborate leads to the formation of 2,2'-anhydro-1 -ß-D-arabinofuranosyluracils, presumably via 2',3'-acyloxonium ions.Recent work from this laboratory has explored methods for the introduction of substituents at C4> of the furanose ring in both purine and pyrimidine nucleosides.3 While other types
TobraDex ST demonstrated improved suspension formulation characteristics, enhanced pharmacokinetic distribution and improved bactericidal characteristics, and may provide a useful alternative as compared to TobraDex.
Moxifloxacin achieved the highest levels of antibiotic in ocular tissues. In the conjunctiva and cornea, the moxifloxacin level was 3-30 times the level of other fluoroquinolones, at least twice the level of the aminoglycosides, and 25 times the level of the antibacterial trimethoprim.
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