Visible Light Photoredox Catalysis Enables the Biomimetic Synthesis of Nyingchinoids A, B and D, and Rasumatranin D

The total synthesis of nyingchinoids A and B has been achieved via successive rearrangements of a 1,2‐dioxane intermediate that was assembled using a visible light photoredox catalysed aerobic [2+2+2] cycloaddition. Nyingchinoid D was synthesised by a competing [2+2] cycloaddition. Based on NMR data and biosynthetic speculation, we proposed a structure revision of the related natural product rasumatranin D, which was confirmed through total synthesis. Under photoredox conditions, we observed the conversion of a cyclobutane into a 1,2‐dioxane via retro‐[2+2] cycloaddition followed by aerobic [2+2+2] cycloaddition.

from A via a.sfakia on Inoreader http://bit.ly/2RxHa6Q