Synthesis of the quinolizidine alkaloids (-)-lasubine II and (+/-)-myrtine by conjugate addition and intramolecular acylation of amino esters with acetylenic sulfones.
The conjugate additions of (2-piperidyl)acetate esters to acetylenic sulfones, followed by LDA-promoted intramolecular acylations, afforded cyclic enaminones that were readily converted into the corresponding 4-substituted 2-keto- or 2-hydroxyquinolizidines by stereoselective reduction and desulfonylation. This procedure was applied to the total synthesis of (-)-lasubine II from methyl (S)-(2-piperidyl)acetate and 2-(3,4-dimethoxyphenyl)-1-(p-toluenesulfonyl)ethyne. Similarly, methyl (+/-)-(2-piperidyl)acetate and 1-(p-toluenesulfonyl)propyne provided (+/-)-myrtine.
Back
Thomas G
TG
Department of Chemistry, University of Calgary, Calgary, Alberta, Canada T2N 1N4. tgback@ucalgary.ca
Hamilton
Michael D
MD
Lim
Vania J J
VJ
Parvez
Masood
M