Irigermanone, a Noriridal with Unprecedented Methylketone Function, from Iris germanica

A new iridal, irigermanone (1) and nine known congeners, 2–10, respectively, have been isolated from the dried rhizomes of German iris (Iris germanica). The structure of 1 was established by spectroscopic methods including HR‐ESI‐MS, 1D‐ and 2D‐NMR, and electronic circular dichroism (ECD) spectroscopy. Compound 1 is a structurally unique noriridal, and it possesses an unprecedented methylcarbonyl group instead of the α,β‐unsaturated aldehyde function typical for this group of triterpenes.