89. Highly Stereoselective Total Syntheses of (±)-Chelidonine and of (±)-Norchelidonine by an Intramolecular o-Quinodimethane/Nitrostyrene-Cycloaddition
    Oppolzer, W.; Robbiani, C.
    Helv. Chim. Acta 1983, 66, 1119-1128

Conversion of 2-bromomethylstyrene 22 and benzocyclobutenyl carbamate 28 to the benzophenanthridine alkaloids (±)-chelidonine (1, five steps, 25% from 28) and to (±)-norchelidonine (2, six steps, 24% from 28) are described. The key step 29 31 involves a highly regio- and stereocontrolled intramolecular Diels-Alder reaction of the (E)-quinodimethane 30.

DOI : 10.1002/hlca.19830660415