Total Synthesis of Gymnothelignan K via a One-Pot Homologative γ-Butyrolactonization

Divergent Syntheses of (-)-Chicanine, (+)-Fragransin A2, (+)-Galbelgin, (+)-Talaumidin, and (+)-Galbacin via One-Pot Homologative γ-Butyrolactonization

In this study, the divergent syntheses of (-)-chicanine, (+)-fragransin A2, (+)-galbelgin, (+)-talaumidin, and (+)-galbacin are detailed. In this approach, an early-stage modified Kowalski one-carbon homologation reaction is utilized to construct the central γ-butyrolactone framework with the two necessary β,γ-vicinal stereogenic centers. The two common chiral γ-butyrolactone intermediates were designed to be capable for assembling five different optically active tetrahydrofuran lignans from commercially available materials in a concise and effective divergent manner in five to eight steps. These five syntheses are among the shortest and highest-yielding syntheses reported to date.

Bioinspired Total Syntheses of Gymnothelignans

Since 2012, Xu and Zhou have reported the isolation of a series of gymnotheligans, a large group of novel tetrahydrofuran-containing lignan natural products. In the past decade, considerable achievements in the total syntheses of these lignans have been achieved based on a plausible biogenetic pathway proposed by our group in 2014. In this account, we summarize these remarkable synthetic works of the past ten years.

1 Introduction

2 Biogenetic Pathways to Gymnothelignans

3 Total Syntheses of Eupodienones

4 Total Syntheses of Eupomatilones

5 Total Synthesis of Dibenzocyclooctenes

6 Conclusions