Stereoselective Total Synthesis of (-)-β-Conhydrine and (+)-α-Conhydrine

We have carried out the stereoselective synthesis of (-)-β-conhydrine and (+)-α-conhydrine, two bioactive α-hydroxyalkyl-substituted piperidines, using the commercially available and inexpensive amino alcohol (S,S)-(+)-pseudoephedrine as chiral auxiliary. The key step of this synthesis relies on new methodology previously developed in our group, consisting of the chemo- and dia­stereoselective addition of Grignard reagents across the C=N bond of α-iminoglyoxylamides derived from (S,S)-(+)-pseudoephedrine followed by the selective monoaddition of organolithium reagents­ to the carbamoyl group, leading to the formation of enantioenriched α-amino ketones.