Concise synthesis of N3- and N6-monoprotected 3,6-diazabicyclo[3.1.1]heptanes; useful intermediates for the preparation of novel bridged bicyclic piperazines

Bridged bicyclic piperazines are important building blocks in medicinal chemistry research. The bicyclic piperazine 3,6-diazabicylo[3.1.1]heptane is of particular interest as a piperazine isostere because it is achiral and shows similar lipophilicity to that of piperazine based on the c Log P of a derived analog. A concise synthesis of N3- and N6-monoprotected 3,6-diazabicyclo[3.1.1]heptanes 2d and 2e, respectively, is described. The seven step sequence begins with inexpensive starting materials and uses straightforward chemistry.