Establishment of benzodioxazine core structure for sarcodonin class of natural products by X-ray analysis.

Sarcodonin ε (2), isolated from Sarcodon scabrosus, was treated with trimethylsilyldiazomethane to yield a crystalline methylated derivative 6. The structure of 6 was determined by X-ray analysis, which confirmed the presence of an unprecedented N(1b)-OMe group, the configuration at N(1b) and the 1,3,4-substituted phenyl ring structure of 2. More importantly, the structures of 6 and 2 have answered the intriguing problem of solving the core structure of the sarcodonin class of natural products, establishing that sarcodonins have a benzodioxazine core structure, rather than the recently proposed benzodioxane aminal core structure.