Total synthesis of the coccinellid alkaloid (+/-)-adalinine utilizing a nitrenium ion cyclization

The total synthesis of (+/-)-adalinine, a piperidine alkaloid from the European two-spotted ladybird Adalia bipunctata, is reported. Central to this undertaking are (i) the use of an N-alkoxy-N-acyinitrenium ion-induced spirocyclization to rapidly access the 6,6'-disubstituted piperidinone ring of the natural product and (ii) exploitation of the cyclohexa-2,5-dienone system generated in this process as a latent 1,6-ketoaldehyde.