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

Abstract

The total synthesis of nyingchinoids Aa nd Bh as been achieved through successive rearrangements of a1 ,2dioxane intermediate that was assembled using av isible-light photoredox-catalysed aerobic [2+ +2+ +2] cycloaddition. Nyingchinoid Dw as synthesised with ac ompeting [2+ +2] cycloaddition. Based on NMR data and biosynthetic speculation, we proposed as tructure revision of the related natural product rasumatranin D, which was confirmed through total synthesis. Under photoredoxc onditions,w eo bserved the conversion of ac yclobutane into a1 ,2-dioxane through retro-[2+ +2] cycloaddition followed by aerobic [2+ +2+ +2] cycloaddition. Scheme 1. Proposed biosynthesis of nyingchinoidsA,

Sarcaglarols A—D, Lindenane−Monoterpene Heterodimers from Sarcandra glabra Based on Molecular Networks

“…The discovery of sarcaglarols A—D ( 1 — 4 ) allowed us to reconsider our previously proposed biogenetic pathways of this unique lindenane‐monoterpene heterodimeric skeleton fused by a 1,2‐dioxane moiety. [ 6 ] According to their structures and recent references, [ 23‐25 ] geraniol and chloranthalactone A, the abundant constituents in S. glabra , [ 8 ] would be the biogenetic precursors, and photocatalytic aerobic [2+2+2] cycloaddition may play the key role in construction of this unique skeleton. A modified biosynthetic pathway of this heterodimeric skeleton was proposed in Scheme 1.…”

Recent advances in the total synthesis of cyclobutane-containing natural products

“…Upon removal of the TBDPS group, echinocidin B (53) was formed with high efficiency. Furthermore, the esterification of 48 with orsellinic acid derivative 49 delivered orsellinate ester 50, which was then advanced to armillaridin (54) in 70% yield over two steps.…”

“…53 Very recently, George and co-workers achieved the biomimetic synthesis of (±)-nyingchinoid D (130) and its analogues by a photocatalytic aerobic [2 + 2] cycloaddition pathway (Scheme 19). 54 Diene 127 was readily prepared through the known condensation of orcinol (125) and citral (126) followed by TBS protection. The pyrylium photoredox-catalyzed aerobic [2 + 2] cycloaddition of 128 according to the slightly modified procedure of Nicewicz [4-MeO-TPT (2 mol%), O 2 (1 atm), LED (470 nm), DCE, 0°C, 20 min] afforded cyclobutane 129 in 87% yield as the sole product.…”

Synthesis of Cannabinoids: “In Water” and “On Water” Approaches: Influence of SDS Micelles

“…Finally, compound 6 evolves via a formal [2+2+2] heterocycloaddition, initiated by condensation of a second molecule of citral, to produce the tetracyclic structure 7 . Although some recent examples of this reaction were reported, mainly via photochemical or radical processes, 16 no precedents of such a reaction involving two alkenes and a carbonyl group are found when the literature was revised to the best of our knowledge. Again, the production of compound 7 can be perfectly justified from the computational point of view with energetic barriers surmountable ( Scheme 3 ).…”