Diastereocontrolled synthesis of (-)-codonopsinine

An efficient process is described for the total synthesis of the alkaloid (-)-codonopsinine. The synthetic strategy is based on the diastereoselective hydrocyanation of a 2,3-dialkoxyaldehyde derived from L-threonine followed by a reductive alkylation of the nitrile function with a Grignard compound and sodium borohydride. The resulting aminotriol was then cyclized into the target molecule after selective mesylation.