Chapter VII The Strychnos Alkaloids

Alkaloids from nitrones

“…Cycloreversion of 53 to nitrone ester 49 was accompanied by concomitant intramolecular cycloaddition to give tricycloadduct 54. The crucial stereochemical result of this process places the ester function in the desired exo orientation in 54. This consequence stems from the trans configuration of the double bond in 49 and the maintenance of stereochemical integrity during the cycloaddition to 54. After the alkylation of 54, the resulting methiodide 55 is subjected to reductive scission of the N O bond, affording ecgonine methyl ester (56).…”

“…A synthetic foray55 in this area which highlights several advantages of nitrones in synthesis involves the chemical construction of ¿/-cocaine (48). 56 Retrosynthetic analysis suggests that nitrone 49 incorporates the features essential to the problem. The synthesis and cyclization of nitrone 49 are shown in Scheme VI.…”