Stereoselective total synthesis of cochliomycin A

Resorcylic acid lactones (RALs) and their structural congeners: recent advances in their biosynthesis, chemical synthesis and biology

Resorcylic acid lactones (RALs) are naturally occurring 14-membered macrolactones that constitute a class of polyketides derived from fungal metabolites and that possess significant and promising biological activity.

Discovery, Semisynthesis, Antiparasitic and Cytotoxic Evaluation of 14-Membered Resorcylic Acid Lactones and Their Derivatives

Ten antifouling 14-membered resorcylic acid lactones 1-10 were isolated previously with low or trace natural abundance from the zoanthid-derived Cochliobolus lunatus fungus. Further optimization of fermentation conditions led to the isolation of two major natural compounds 7 and 8 with multi-gram quantities. By one or two steps, we semisynthesized the six trace natural compounds 1-6 and a series of derivatives 11-27 of compounds 7 and 8 with high yields (65-95%). Compounds 11-13 showed strong antiplasmodial activity against Plasmodium falciparum with IC50 values of 1.84, 8.36, and 6.95 μM, respectively. Very importantly, 11 and 12 were non-toxic with very safety and high therapeutic indices (CC50/IC50 > 180), and thus representing potential promising leads for antiplasmodial drug discovery. Furthermore, 11 was the only compound showed obvious antileishmanial activity against Leishmania donovani with an IC50 value of 9.22 μM. Compounds 11 and 12 showed the values of IC50 at 11.9 and 17.2 μM against neglected Chagas' disease causing Trypanosoma cruzi, respectively.

Total Syntheses of the Resorcylic Acid Lactones Paecilomycin F and Cochliomycin C Using an Intramolecular Loh-Type α-Allylation Reaction for Macrolide Formation

Subjection of the resorcylic ester 16 to a Nozaki-Hiyama-Kishi reaction afforded the 12-membered lactone 17, while treatment of it under the Loh-type α-allylation conditions using indium metal gave the isomeric, 14-membered macrolide 18. Compound 18 was readily elaborated to the resorcylic acid lactone type natural products paecilomycin F and cochliomycin C.

Mini-review: marine natural products and their synthetic analogs as antifouling compounds: 2009-2014

This review covers 214 marine natural compounds and 23 of their synthetic analogs, which were discovered and/or synthesized from mid-2009 to August 2014. The antifouling (AF) compounds reported have medium to high bioactivity (with a threshold of EC(50) < 15.0 mg ml(-1)). Among these compounds, 82 natural compounds were identified as new structures. All the compounds are marine-derived, demonstrating that marine organisms are prolific and promising sources of natural products that may be developed as environmentally friendly antifoulants. However, this mini-review excludes more than 200 compounds that were also reported as AF compounds but with rather weak bioactivity during the same period. Also excluded are terrestrial-derived AF compounds reported during the last five years. A brief discussion on current challenges in AF compound research is also provided to reflect the authors' own views in terms of future research directions.

Modular total syntheses of the marine-derived resorcylic Acid lactones cochliomycins a and B using a late-stage nozaki-hiyama-kishi macrocyclization reaction

The natural products cochliomycin A (1) and cochliomycin B (2), two resorcylic acid lactones obtained from marine sources, have been prepared in a concise and stereocontrolled manner from the readily accessible building blocks 4-6. Olefin cross-metathesis, trans-esterification and Nozaki-Hiyama-Kishi (NHK) macrocyclization reactions were employed in the key steps. Hydrolysis of the immediate precursor to cochliomycin B affords the resorcylic acid lactone zeaenol (24).

Asymmetric total synthesis of paecilomycin E, 10'-epi-paecilomycin E and 6'-epi-cochliomycin C

The asymmetric total syntheses of naturally occurring resorcylic acid lactone paecilomycin E and two of its structural congeners have been reported in this article. The major highlight of the synthetic venture is the application of the late stage Mitsunobu macrolactonization method (as it is difficult to achieve the desired products through the standard carboxyl activation method) of a properly functionalized seco-acid. The macrolactonization precursor was synthesized by applying an "E"-selective Julia-Kocienski olefination of a highly functionalized aromatic aldehyde and a sulphone, which constitutes all the stereocenters (C4', C5', C6' and C10'; 3S,7R,8R,9S) in the target molecule.