Total synthesis of the (+)-antimycin A3 family: structure elucidation of (+)-antimycin A3a

Neoantimycins A and B, Two Unusual Benzamido Nine-Membered Dilactones from Marine-Derived Streptomyces antibioticus H12-15

An actinomycete strain (H12-15) isolated from a sea sediment in a mangrove district was identified as Streptomycesantibioticus on the basis of 16S rDNA gene sequence analysis as well as the investigation of its morphological, physiological, and biochemical characteristics. Two novel benzamido nonacyclic dilactones, namely neoantimycins A (1) and B (2), together with the known antimycins A_1ab (3a,b), A_2a (4), and A₉ (5), were isolated from the culture broth of this strain. Compounds 1 and 2 are the first natural modified ATNs with an unusual benzamide unit. The structures of these new compounds, including their absolute configuration, were established on the basis of HRMS, NMR spectroscopic data, and quantum chemical ECD calculations. Their cytotoxicities against human breast adenocarcinoma cell line MCF-7, the human glioblastoma cell line SF-268, and the human lung cancer cell line NCI-H460 were also tested. All compounds exhibited mild cytotoxic activity. However, Compounds 1 and 2 showed no activity against C. albicans at the test concentration of 1 mg/mL via paper disc diffusion, while the known antimycins showed obvious antifungal activity.

Antimycin-type depsipeptides: discovery, biosynthesis, chemical synthesis, and bioactivities

This review discusses the isolation, structural variation, biosynthesis, chemical synthesis, and biological activities of antimycin-type depsipeptides.

Mitochondrial drugs

Mitochondria are cellular organelles that perform pivotal functions essential for ATP production, homeostasis, and metabolism. Moreover, mitochondria are integral to a variety of cell death and survival pathways. These roles identify mitochondria as a potential target for drugs to treat metabolic and hyperproliferative diseases. Differences in the redox state of pathogenic versus non-pathogenic cells may be exploited to achieve selective anti-proliferative and cytotoxic activity against target cell populations. Pro-oxidant drugs, such as Trisenox and Elesclomol, are demonstrating clinical utility in the treatment of cancer. Results obtained with Bz-423 in mice demonstrate the potential for mitochondria-targeted drugs to control disorders of immune function. Research associating an elevated oxidant state with mitochondrial damage, degenerative disease, and aging dictates the need for a better understanding of when and how pharmacological manipulation of mitochondrial function provides most therapeutic benefit.

Antineoplastic agents. 561. Total synthesis of respirantin

Total synthesis of the 18-membered ring cyclodepsipeptide believed to be respirantin (1b) has been achieved. The key step in the synthesis is an intramolecular transesterification of the beta-ketoester alcohol 6 to afford the protected macrocycle 5. The synthetic product was shown to be identical to a natural product presumed to be respirantin (1b), and the absolute stereochemistry of six of the seven asymmetric centers of cyclodepsipeptide 1b was unequivocally established. Respirantin (1b) was found to be a remarkable inhibitor of cancer cell growth and related to the antimycin family of antibiotics.

A Practical Total Synthesis of (+)-Antimycin A9

(+)-Antimycin A9 (AA9) isolated from a cultured broth of Streptomyces sp. K01-0031 was synthesized via an asymmetric aldol reaction using Oppolzer's sultam as a chiral auxiliary.

An Expeditious Enantioselective Synthesis of Antimycin A3b

A straightforward enantioselective route to (+)-antimycin A3b is presented, which used a TiCl4-mediated asymmetric aldolization to construct C-7/C-8 and BnOH/DMAP to remove the chiral auxiliary with concurrent protection of the carboxylic group, respectively. Closing the dilactone ring was achieved in 62% yield (previously 0.8%, 13.4%, or 20%) in the presence of the C-8 ester functionality. The overall yield (34.5%) was significantly higher than that (0.019-3.6%) of the earlier routes.

Apoptolidin: Induction of Apoptosis by a Natural Product

Apoptolidin is a natural product that selectively induces apoptosis in several cancer cell lines. Apoptosis, programmed cell death, is a biological key pathway for regulating homeostasis and morphogenesis. Apoptotic misregulations are connected with several diseases, in particular cancer. The extrinsic way to apoptosis leads through death ligands and death receptors to the activiation of the caspase cascade, which results in proteolytic degradation of the cell architecture. The intrinsic pathway transmits signals of internal cellular damage to the mitochondrion, which loses its structural integrity, and forms an apoptosome that initiates the caspase cascade. Compounds which regulate apoptosis are of high medical significance. Many natural products regulate apoptotic pathways, and apoptolidin is one of them. The known synthetic routes to apoptolidin are described and compared in this Review. Selected further natural products which regulate apoptosis are introduced briefly.