An intramolecular Mannich reaction, involving cyclanones together with a ke
toprotected aminobutanone in the presence of a Lewis acid, is employed to p
repare rapidly 2,2 ' -spiropiperidine skeletons. Phis approach is validated
through a concise and efficient synthesis of spiro [piperidine-2,2 ' -adam
antane] 4, an antiviral agent. (C) 2001 Elsevier Science Ltd. All rights re
served.