Photomediated Transformation of Salannin a Tetranortriterpenoid from Azadirachta indica A. Juss

摘要

Photolysis of Salannin (>1), an important bioactive compound from Azadirachta indica A.Juss (Neem), affords Δ¹⁷-isosalanninolide (>2), a hitherto unknown compound, along with isosalanninolide (>3) and salanninolide (>4). A probable mechanism has been suggested. While the mechanism of formation of >2 involves both a [4+2] cycloaddition and a [,] sigmatropic shift in the furan and D-rings, respectively, formation of >3 and >4 involves the decomposition of an ozonoide-like peroxide intermediate.