"Tandem Beckmann and Huisgen-White Rearrangement of the 9-Azabicyclo[3.3.1]-Nonan-3-One System. Part 2. The secound Mode of the Rearrangement Leading to 6-(Prop-L-Enyl)Piperidin-2-Ylacetic Acid, a Versatile Intermediate for the Syntheses of Piperidine Alk