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Fluorinated nucleoside 1 is a key starting material in the synthesis of rovafovir etalafenamide (2), a novel nucleotide reverse transcriptase inhibitor under development at Gilead Sciences for the treatment of HIV. While an initial manufacturing route enabled the production of 1 to support clinical development, alternative approaches were explored to further enhance manufacturing effectiveness, improve processing time, reduce cost, and minimize the environmental impact. Toward this end, two new routes were developed to a key synthetic intermediate, which was converted to 1 using a new protecting group strategy. The new chemistry led to improvements in the manufacturing process while reducing the overall process mass intensity (PMI).

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The multicomponent proton conducting ceramics SiO2–TiO2–ZrO2–P2O5 (STZP) and SiO2–TiO2–ZrO2–P2O5–Bi2O3 with three different compositions (STZPBi3, STZPBi10, and STZPBi15) were synthesized via a wet chemical route. These prepared materials showed good thermal stability up to around 900°C by TG/DTA analyses. Introduction of optimum quantity of bismuth as a sintering aid into the samples contributed to enhance the densification of microstructure, which is essential for the utilization of proton conducting ceramics in fuel cells operated at elevated temperature. The proton conductivity of STZP was 3.6×10−5 S/cm at 80°C and that of STZPBi10 was 4.6×10−3 S/cm at 180°C. The fuel cell performances using STZP and STZPBi10 were implemented at 80°C and up to 230°C, respectively. The maximum power density was 0.03 mW/cm2 at 80°C for the STZP sample and 2.5 mW/cm2 at 150°C for the STZPBi10 sample under wet hydrogen and dry oxygen. The reduction of CO poisoning on platinum catalyst was demonstrated in fuel cell operating at temperatures of 180°C, 200°C, and 230°C.