Asymmetric synthesis of (-)-adaline

[GRAPHIC] An enantioselective total synthesis of (-)-adaline has been achieved starting from a chiral 6,6-disubstituted piperidone derivative previously prepared by diastereoselective allylation of a chiral tricyclic N-acyl-N,O-acetal. The key steps include lithium ion-activated S(N)2-type alkynylation of the tricyclic NO-acetal leading to exclusive formation of the (6S)-ethynylpiperidine and ring-closing olefin metathesis of the (2R,6S)-cis-2,6-dialkenylpiperidine for constructing the bridged azabicyclononane.