A laboratory model for the atisane leads to aconane conversion.

Abstract

Atisine (1) has been converted into the epimeric toluene-p-sulphonates (28) and (29). On acetolysis either (28) or (29) affords the same 14(8 → 15)abeo-17-oxa-8-ene (19). In contrast, whereas gas phase pyrolysis of the ester (28) gives the olefin (19), the isomer (29) gives a 9(8 → 15)abeo-17-oxa-8(14)ene (20); each conversion takes place stereospecifically via a seven-membered transition state. The structure of the olefin (20) has been confirmed by an X-ray crystal structure analysis of the derived ethylene acetal hydriodide (48). An n.m.r. analysis of hindered rotation in two amides [(19) and (21)] is presented.