Synthesis of the non-classical acetogenin mucocin: a modular approach based on olefinic coupling reactions

Acetogenins from Annonaceae

In recent decades, annonaceous acetogenins have become highly studied plant secondary metabolites in terms of their isolation, structure elucidation, synthesis, biological evaluation, mechanism of action, and toxicity. The aim of the present contribution is to summarize chemical and biological reports published since 1997 on annonaceous acetogenins and synthetic acetogenin mimics. The compounds are considered biologically in terms of their cytotoxicity for cancer cell lines, neurotoxicity, pesticidal effects, and miscellaneous activities.

Total synthesis of annonaceous acetogenins belonging to the non-adjacent bis-THF and non-adjacent THF-THP sub-classes

The synthesis of the subgroups of acetogenins containing non-adjacent bis-THF and non-adjacent THF-THP core units is reviewed. Specifically, total syntheses of gigantecin, 4-deoxygigantecin, cis-sylvaticin, squamostatin-C, squamostatin-D, sylvaticin and mucocin are discussed.

Recent progress on the total synthesis of acetogenins from Annonaceae

An overview of recent progress on the total synthesis of acetogenins from Annonaceae during the past 12 years is provided. These include mono-tetrahydrofurans, adjacent bis-tetrahydrofurans, nonadjacent bis-tetrahydrofurans, tri-tetrahydrofurans, adjacent tetrahydrofuran-tetrahydropyrans, nonadjacent tetrahydrofuran-tetrahydropyrans, mono-tetrahydropyrans, and acetogenins containing only gamma-lactone. This review emphasizes only the first total synthesis of molecules of contemporary interest and syntheses that have helped to correct structures. In addition, some significant results on the novel synthesis and structure-activity relationship studies of annonaceous acetogenins are also introduced.

Synthetic and Computational Studies on the ABC Trioxadispiroketal Subunit of the Marine Biotoxin Azaspiracid-1

The trioxadispiroketal residue in the marine biotoxin azaspiracid-1, which exists in a configuration capable of exhibiting a double anomeric effect, is believed to be the thermodynamically most stable bis-spiroketal diastereomer. In order to get insight into how structural factors affect this equilibrium, a simplified ABC trioxadispiroketal analog of azaspiracid-1 was synthesized and subjected to equilbration and computational studies. Compound 7, which represents a double anomeric effect was obtained as the major isomer, together with diastereomers 14 and 15, in a respective ratio of 62:22:16. DFT calculations for 7, 14 and 15 qualitatively matched this observation. These results suggest that while a double anomeric effect may play a major role in the stability of the trioxadispiroketal configuration in the more complex natural product, the substitution pattern of the C ring is also a contributing factor.

Structural determination of montanacin D by total synthesis

The first total syntheses of acetogenin 3 and its 4 S,8 R-isomer are described. The key step involves intermolecular metathesis of an alpha,beta-unsaturated ketone carrying a tetrahydropyranyl lactone with a tetrahydrofuran derivative. Compound 3 has spectroscopic and physical data consistent with those of natural montanacin D, suggesting that the absolute configuration of the natural product is as shown in 3.

Total synthesis of (-)-mucocin

[reaction: see text] An enantioselective total synthesis of (-)-mucocin has been completed. A combination of asymmetric glycolate aldol additions and ring closing metathesis reactions were exploited to construct the C18-C34 and C7-C17 fragments. A selective cross-metathesis reaction was employed as the key step to couple two complex fragments.