Conformationally Restricted Amino Cyclopropane-Fused Lactones from Mannich Bases

We converted easily accessible Mannich bases into cyclopropane-fused lactones by combining a photochemical reaction using simple 370 nm LED source with acid-catalyzed hydrolysis and lactonization. The alcohol functional group generated in the photochemical reaction was used in the subsequent step. This three-step sequence rapidly generates conformationally restricted amino cyclopropane-fused γ-, δ-, and ε-lactones. We also devised a method to kinetically monitor the cyclopropanation reaction and to analyze the data through a full-spectrum quantitation approach.