3-Aminopyrrolidines via Ring Rearrangement of 2-Aminomethylazetidines. Synthesis of (−)-Absouline

[reaction: see text] A new entry to enantiopure 3-aminopyrrolidines was developed using a boron trifluoride-mediated rearrangement of 2-aminomethylazetidines. The method is quite general and produces rearranged products in good yield regardless of both substitution pattern and relative stereochemistry of the starting material. A concise stereocontrolled synthesis of (-)-absouline was achieved on the basis of this new method.