Intramolecular [4 + 1] pyrroline annulation via azide-diene cycloadditions. 2. Formal stereoselective total syntheses of (.+-.)-platynecine, (.+-.)-hastanecine, (.+-.)-turneforcidine, and (.+-.)-dihydroxyheliotridane
Intramolecular [4 + 1] pyrroline annulation via azide-diene cycloadditions. 2. Formal stereoselective total syntheses of (.+-.)-platynecine, (.+-.)-hastanecine, (.+-.)-turneforcidine, and (.+-.)-dihydroxyheliotridane