“…Some 1,3,5,7-tetraazabicyclo[3.3.1]nonane derivatives have antithrombotic activities [29]. Although tremendous progress has been achieved in the synthesis of mono-, di-, and tri-azabicyclo[3.3.1]nonanes [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27], the synthesis of tetra- and penta-azabicyclo[3.3.1]nonane frameworks has rarely been disclosed in the literature [30,31,32,33].…”