Lactone Annulation and Substitutive Spiroannulation

The facile conversion of carbonyl groups into lactones via cyclobutanones offers many opportunities for synthetic applications considering the importance of butanol-ides in natural products synthesis. The iridoids vividly illustrate this potential. Allamandin (163) 135 c) and its dehydrated relative plumericin (164) 135 d), compounds possessing antifungal, antibacterial, and antitumor activity, pack a great deal of 

At this time, we can focus on the creation of the butenolide. Sulfur based methodoly allows simplification to the simple butanolide as in 170. While cyclobutanone spiroannulation of 171 followed by a Baeyer-Villiger reaction would create 170, 

---