Total synthesis of an anticancer agent, mucocin. 2. A novel approach to a γ-hydroxy butenolide derivative and completion of total synthesis

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.

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.

The total synthesis of the annonaceous acetogenin, muricatetrocin C

The total synthesis of the potential antitumour agent muricatetrocin C has provided an ideal stage for the exploitation and development of new chemistry. A convergent synthetic strategy has been realised incorporating three distinct pieces of methodology, these include a highly diastereoselective hetero-Diels-Alder reaction to construct the butenolide terminus, an oxygen to carbon rearrangement to install the trans-2,5-disubstituted tetrahydrofuran ring and a spatial desymmetrisation process to afford the anti-diol unit.

Quinone-annonaceous acetogenins: synthesis and complex I inhibition studies of a new class of natural product hybrids

The natural product hybrids quinone-mucocin and quinone- squamocin D were synthesized. In these hybrids, the butenolide unit of the annonaceous acetogenins mucocin and squamocin D is exchanged for the quinone moiety of the natural complex I substrate ubiquinone. For both syntheses, a modular, highly convergent approach was applied. Quinone-mucocin was constructed out of a tetrahydropyran (THP) component 1, a tetrahydrofuran (THF) unit 2, and a quinone precursor 3. A stereoselective, organometallic coupling reaction was chosen for the addition of the THP unit to the rest of the molecule. In the final step, the oxidation to the free quinone was achieved by using cerium(IV) ammonium nitrate (CAN) as the oxidizing agent. Quinone-squamocin D was assembled in a similar manner, from the chiral side chain bromide 16, the central bis-THF core 17, and the quinone precursor 18. Inhibition of complex I (isolated from bovine heart mitochondria) by the quinone acetogenins and several smaller building blocks was examined; quinone mucocin and quinone-squamocin D act as strong inhibitors of complex I. These results and the data from the smaller substructures indicate that other substructures of the acetogenins besides the butenolide group, such as the polyether component and the lipophilic left-hand side chain, are necessary for the strong binding of the acetogenins to complex I.

Base-catalyzed epimerization of the butenolide in annonaceous acetogenins

The elusive epimerization process in the chiral butenolide moiety of Annonaceous acetogenins was examined under several sets of conditions commonly used for elimination leading to the alpha, beta-unsaturated lactone and the results provide practical guidance in choosing elimination conditions.

Total synthesis of a new cytotoxic acetogenin, jimenezin, and the revised structure

The first total synthesis of jimenezin was achieved by using carbohydrates as chiral building blocks, thus revising the proposed structure 1 to 2. The key steps in this synthesis include an efficient construction of the THP-THF fragments 3 and 16 through a stereoselective condensation between the pyranyl aldehyde 5 and the acetylene derivative 6, and a palladium-catalyzed coupling reaction of 3 or 16 with a terminal butenolide 4.