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Several series of 45 acetophenone derivatives bearing various alkyl or benzyl substituents were conveniently synthesized and their structures characterized by (1)H and (13)C NMR spectroscopy, HRMS and single-crystal X-ray analysis. Their in vitro antifungal activities against a panel of phytopathogenic fungi were evaluated by mycelial growth rate assay. Of them, 12 derivatives (e.g., 3a-c, 4c and 4e) exhibited more potent antifungal effects on some phytopathogens than a commercial fungicide hymexazol as positive control. In particular, compound 3b with IC50 values of 10-19 μg/mL was found to be the most active in this series and might be a potential lead structure for further optimization. The preliminary structure-activity relationship (SAR) studies of a series of acetophenones are also discussed.

There is a strong demand for bioanalytical techniques to rapidly detect protease activities with high sensitivity and high specificity. This study reports an activity-based electrochemical method toward this goal. Nanoelectrode arrays (NEAs) fabricated with embedded vertically aligned carbon nanofibers (VACNFs) are functionalized with specific peptide substrates containing a ferrocene (Fc) tag. The kinetic proteolysis curves are measured with continuously repeated ac voltammetry, from which the catalytic activity is derived as the inverse of the exponential decay time constant based on a heterogeneous Michaelis–Menten model. Comparison of three peptide substrates with different lengths reveals that the hexapeptide H2N─(CH2)4─CO─Pro-Leu-Arg-Phe-Gly-Ala─NH─CH2─Fc is the optimal probe for cathepsin B. The activity strongly depends on temperature and is the highest around the body temperature. With the optimized peptide substrate and measuring conditions, the limit of detection of cathepsin B activity and concentration can reach 2.49 × 10−4 s−1 and 0.32 nM, respectively. The peptide substrates show high specificity to the cognate proteases, with negligible cross-reactions among three cancer-related proteases cathepsin B, ADAM10, and ADAM17. This electrochemical method can be developed into multiplex chips for rapid profiling of protease activities in cancer diagnosis and treatment monitoring.

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Pinnigorgiols B and E are 9,11-secosteroids with a unique tricyclic γ-diketone framework. Herein, we report the first synthesis of these natural products from inexpensive, commercially available ergosterol. This synthesis features a semipinacol rearrangement and an acyl radical cyclization/hemiketalization cascade; the latter efficiently assembled the tricyclic γ-diketone skeleton, with two rings and three contiguous stereogenic centers being formed in a single step.

No abstract

Myrmenaphthol A is a structurally unique phenolic steroid with a naphthyl AB-ring system and an unusual C2 hydroxy group. Herein, we report the first total synthesis of this natural product in 10 steps from inexpensive, commercially available sitolactone. Key features of the synthesis include a Baran decarboxylative coupling and a Friedel–Crafts cyclization/olefin isomerization/aromatization cascade that rapidly assembled the tetracyclic core framework. This synthetic strategy is expected to be readily amenable to the synthesis of other phenolic steroids.

Second-generation chiral-substituted poly-N-vinylpyrrolidinones (CSPVPs) (−)-1R and (+)-1S were synthesized by free-radical polymerization of (3aR,6aR)-and (3aS,6aS)-5-ethenyltetrahydro-2,2-dimethyl-4H-1,3-dioxolo [4,5-c]pyrrol-4-one, respectively, using thermal and photochemical reactions. They were produced from respective D-isoascorbic acid and D-ribose. In addition, chiral polymer (−)-2 was also synthesized from the polymerization of (S)-3-(methoxymethoxy)-1-vinylpyrrolidin-2one. Molecular weights of these chiral polymers were measured using HRMS, and the polymer chain tacticity was studied using 13 C NMR spectroscopy. Chiral polymers (−)-1R, (+)-1S, and (−)-2 along with poly-N-vinylpyrrolidinone (PVP, MW 40K) were separately used in the stabilization of Cu/Au or Pd/Au nanoclusters. CD spectra of the bimetallic nanoclusters stabilized by (−)-1R and (+)-1S showed close to mirror-imaged CD absorption bands at wavelengths 200−300 nm, revealing that bimetallic nanoclusters' chiroptical responses are derived from chiral polymer-encapsulated nanomaterials. Chemo-, regio-, and stereoselectivity was found in the catalytic C−H group oxidation reactions of complex bioactive natural products, such as ambroxide, menthofuran, boldine, estrone, dehydroabietylamine, 9-allogibberic acid, and sclareolide, and substituted adamantane molecules, when catalyst Cu/Au (3:1) or Pd/Au (3:1) stabilized by CSPVPs or PVP and oxidant H 2 O 2 or t-BuOOH were applied. Oxidation of (+)-boldine N-oxide 23 using NMO as an oxidant yielded 4,5-dehydroboldine 27, and oxidation of (−)-9-allogibberic acid yielded C6,15 lactone 47 and C6-ketone 48.