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.

Asymmetric synthesis of trans-4,5-disubstituted γ-butyrolactones involving a key allylboration step. First access to (−)-nicotlactone B and (−)-galbacin

A new approach based on one-pot sequential transformations with application for the first total synthesis of (−)-nicotlactone B and (−)-galbacin.

Asymmetric synthesis of ent-fragransin C1

The first asymmetric synthesis of ent-fragransin C₁ bearing 2,3-anti-3,4-syn-4,5-anti stereochemistries is reported.

Lignans from the Australian Endemic Plant Austrobaileya scandens

The sole species of the vascular plant family Austrobaileyaceae, Austrobaileya scandens, is endemic to the tropical rainforest of northeastern Queensland, Australia. A single lead-like enhanced fraction of A. scandens showed potent inhibition against human prostate cancer PC3 cells. Chemical investigation of this plant resulted in the isolation of two new aryltetralin lignans, austrobailignans 8 and 9 (1 and 2), and the synthetic compound nicotlactone B (3), newly identified as a natural product together with nine known lignans (4-12). Their structures were established on the basis of spectroscopic analyses. Absolute configurations of the new compounds were determined by quantum chemical electronic circular dichroism (ECD) calculations employing time-dependent density functional theory. The ECD calculations were also used to assign the absolute configuration of marphenol K (4) and revise the absolute configuration of kadsurindutin C (20). Ten out of the 12 isolated compounds inhibited the growth of PC3 cells with IC50 values ranging from micromolar to nanomolar. Marphenol A (5) was found for the first time to induce apoptosis and arrest the S cell cycle phase of PC3 cells.