Progress toward the Total Synthesis of Gukulenin A: Photochemically Triggered Two-Carbon Ring Expansion Key to α-Tropolonic Ether Synthesis

Abstract

The ex-chiral-pool synthesis of an advanced gukulenin A precursor from (-)-piperitone is revealed. Key C/C connecting maneuvers to the synthesis of a C dissymmetric bis(α-tropolonic) ether building block are a ring-contracting Meinwald rearrangement, a photochemically triggered two-carbon ring expansion, and a homodimerization by cross-metathesis.

An Update on Cyclohepta[b]indoles

“…[40] In 2018, Tymann et al made an initial report on a photochemical synthesis of the cyclohepta[b]indole scaffold. [41] Originally designed for tropolone synthesis is the context of terpenoide total synthesis, [42] the photochemically triggered two-carbon ring expansion was adapted and expanded for cyclohepta 32). [43] The two-carbon ring-expansion exploits the inherent atom economy of a photochemically triggered cycloisomerization.…”

“…made an initial report on a photochemical synthesis of the cyclohepta[ b ]indole scaffold [41] . Originally designed for tropolone synthesis is the context of terpenoide total synthesis, [42] the photochemically triggered two‐carbon ring expansion was adapted and expanded for cyclohepta[ b ]indole synthesis. In 2020, Tymann et al.…”

Development of an Alkyne Analogue of the de Mayo Reaction: Synthesis of Medium‐Sized Carbacycles and Cyclohepta[b]indoles

“…Va luable applications of the alkyne-de Mayo reaction in target-oriented synthesis are easily conceivable. [21]…”

“…Key to success in developing an alkyne‐de Mayo reaction was the use of a quasi‐monochromatic light source and a polar protic solvent. Valuable applications of the alkyne‐de Mayo reaction in target‐oriented synthesis are easily conceivable …”

Psathyrellanic Acid, a Monocyclic Diterpenoid From the Basidiomycete Psathyrella candolleana

“…Diterpenoids from fungi have structural and biological diversity, which attracted great attention of both organic and biological researchers. [1][2][3] The basidiomycete Psathyrella candolleana, belonging to the family Psathyrellaceae, is commonly found on lawns or pastures in Europe and North America. It is also widely distributed in Yunnan and Sichuan provinces of China.…”