Stereocontrolled total synthesis of (±)-gelsemine
The stereocontrolled total synthesis of gelsemine (1) via 21-oxogelsemine (2) is reported. Our total synthesis features a stereoselective condensation of cyclopropyl carboxaldehyde 11 and 4-iodo-oxindole, a facile construction of the bicyclo(3.2.1) intermediate 20 with a complete control of the stereochemistry by means of a novel application of divinylcyclopropane-cycloheptadiene rearrangement, and an unprecedented silver ion-mediated lactam formation between carbamoyl chloride and enecarbamate.