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

Abstract

The total synthesis of nyingchinoids A and B has been achieved through 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 with 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 through retro‐[2+2] cycloaddition followed by aerobic [2+2+2] cycloaddition.

Synthesis of sinapine and its unprecedented ruthenium-catalyzed [2+2] photodimerization

“…Although these strained mono-cyclic rings were regarded in the beginning to be somewhat exotic; they could be found and isolated in many plants but only in a very tiny amount, but curiosity in these molecules together with the better isolation techniques and the development of synthetic strategies enable access to many of them. This development was driven in particular by the fact that some cyclobutanoid dimers [5][6][7][8][9][10] , such as innovanoside A, showed high biological activity. Furthermore, numerous cyclobutanoids of superior biological activity were isolated from the Piper genus, such as dipiperamides A-E [11][12][13][14][15][16][17][18] and piperarborenines A-E [19][20][21][22][23][24][25][26][27][28] (Scheme 1) and several total syntheses have been developed.…”