 Both by-products were successfully converted to the desired derivative.Finally, the addition of "p"-toluenethiol with Cs2CO3 gives (6) in a 70% yield after being purified by column chromatography, with the desired isomer dominating.In the second one-pot operation, trifluoroacetic acid is employed first to deprotect the "tert"-butyl ester of (6); any excess reagent was removed via evaporation.