 In the final step the BOC group is removed with phosphoric acid and the oseltamivir phosphate 15 is formed.Also in 2006 the group of Masakatsu Shibasaki of the University of Tokyo published a synthesis again bypassing shikimic acid.An improved method published in 2007 starts with the enantioselective desymmetrization of aziridine 1 with trimethylsilyl azide (TMSN3) and a chiral catalyst to the azide 2.