A devised synthetic strategy toward the QRSTU ring system 4 of the marine-derived biotoxin maitotoxin (1) delivered, in addition to 4, its diastereoisomers 85-epi-QRSTU and 86-epi-QRSTU ring systems 5 and 6. The convergent route to these maitotoxin fragments involved coupling of UT and Q building blocks 9 (obtained from 2-deoxy-D-ribose) and 10 (obtained from D-ribose) followed by ring-closing metathesis to afford enol ether 8, whose elaboration to the targeted QRSTU ring system 4 required its conversion to hydroxy ketone 7. The latter compound (7) was transformed to the final product through a hydroxy dithioketal cyclization, followed by oxidationmethylation of the resulting O,S-mixed ketal to install the last of the five methyl groups contained within the target molecule (4). 13 C NMR spectroscopic analysis of synthesized fragments 4, 5 and 6, and comparisons with maitotoxin, provided strong support for the originally assigned structure of the QRSTU domain of the natural product.

Mild reaction conditions for the regioselective synthesis of isoquinolin‐1‐ones and related fused‐ring heterocycles from N‐Boc‐protected (β‐arylethyl)carbamates are described. The reactions involved the use of Tf2O and 2‐chloropyridine and isocyanates are likely to be key intermediates. The method was extended to substrates bearing less nucleophilic aryl moieties by using Lewis acid additives, such as BF3·Et2O, to enhance the Friedel–Crafts‐type cyclization of the isocyanate intermediates. This method allowed the synthesis of various substituted isoquinolin‐1‐ones, β‐carbolines, thiophene‐fused ring systems and tetrahydrobenzoazepin‐1‐ones in good yields and with high regioselectivities.

A devised biomimetic strategy toward the C′D′E′F′ domain (6) of maitotoxin (1) led to hydroxy triepoxide 8 as a postulated polyepoxide precursor. However, all attempts to induce the desired cascade to form the targeted compound through a zip-type reaction under neutral or acidic conditions failed, prompting adoption of a linear stepwise approach to 6. The successful synthetic strategy for the synthesis of the C′D′E′F′ domain of maitotoxin commenced from furfuryl alcohol (11), proceeded through F′ ring building block 15, and involved two regio-and stereoselective intramolecular hydroxy epoxide openings and a stereoselective SmI 2 -mediated ring closure to forge rings C′, E′, and D′, respectively. 13 C NMR spectroscopic analysis of the synthesized domain (6) and comparisons with previous results confirmed the original structural assignment of this region of maitotoxin. X-Ray crystallographic analysis of 6 provided unambiguous proof of its structure.

KJH-1002 restored cognitive function in scopolamine-induced amnesia mice by activating the cGMP/CREB signalling pathway and attenuating oxidative stress. The beneficial effects of KJH-1002 on cognition indicate its potential as a therapeutic candidate for Alzheimer's disease.

We developed and validated an accurate and sensitive LC-MS/MS method for the simultaneous quantitation of ginsenoside Rg3 and Rh2 epimers (R-Rg3, S-Rg3, R-Rh2, and S-Rh2) in rat plasma. Analytes were extracted from 0.1 mL aliquots of rat plasma by liquid-liquid extraction, using 2 mL of ethyl acetate. In this assay, dioscin (500 ng/mL) was used as an internal standard. Chromatographic separation was conducted using an Acclaim RSLC C18 column (150 × 2.1 mm, 2.2 μm) at 40°C, with a gradient mobile phase consisting of 0.1% formic acid in distilled water and in acetonitrile, a flow rate of 0.35 mL/min, and a total run time of 20 min. Detection and quantification were performed using a mass spectrometer in selected reaction-monitoring mode with negative electrospray ionization at m/z 783.4 → 161.1 for R-Rg3 and S-Rg3, m/z 621.3 → 161.1 for R-Rh2 and S-Rh2, and m/z 867.2 → 761.5 for the internal standard. For R-Rg3 and S-Rg3, the lower limit of quantification was 5 ng/mL, with a linear range up to 500 ng/mL; for R-Rh2 and S-Rh2, the lower limit of quantification was 150 ng/mL, with a linear range up to 6000 ng/mL. The coefficient of variation for assay precision was less than 10.5%, with an accuracy of 86.4-112%. No relevant cross-talk or matrix effect was observed. The method was successfully applied to a pharmacokinetic study after oral administration of 400 mg/kg and 2000 mg/kg of BST204, a fermented ginseng extract, to rats. We found that the S epimers exhibited significantly higher plasma concentrations and area under curve values for both Rg3 and Rh2. This is the first report on the separation and simultaneous quantification of R-Rg3, S-Rg3, R-Rh2, and S-Rh2 in rat plasma by LC-MS/MS. The method should be useful in the clinical use of ginseng or its derivatives.

A new synthetic strategy for construction of the heptacyclic marine fungal alkaloid (±)-communesin F has been devised. Key reactions include an intramolecular Heck cyclization of a tetrasubstituted alkene to generate a tetracyclic enamide bearing one of the quaternary carbon centers (C7) of the alkaloid, an intramolecular reductive cyclization of an N-Boc aniline onto the oxindole moiety to form a pentacyclic framework containing the southern aminal, a stereoselective N-Boc-lactam enolate C-allylation to introduce the second quaternary carbon center (C8), and an azide reduction/N-Boc-lactam-opening cascade leading to the northern aminal.

An efficient synthetic strategy for installation of the two vicinal quaternary carbon centers of the communesins is reported. Key steps include the O-allylation/Claisen rearrangement of spirolactone systems, which are formed by tandem intramolecular Heck cyclization/carbonylation. Substituent and solvent effects on the stereochemical outcome of the Claisen rearrangements have been examined. The stereochemical assignment of the allyl spirolactone previously reported as 17 has now been revised to 32, which has the communesin relative configuration at the quaternary carbons. Key C-allyl spirolactone 59 bearing functional handles required for the communesin core has been constructed with a 9.8:1 diastereomer ratio.

We have developed an efficient three-component tandem reaction for the synthesis of 3-(1,3-diarylallylidene)oxindoles combining three palladium-catalyzed reactions: the Sonogashira, Heck, and Suzuki-Miyaura reactions. This method allows a stereoselective approach to each (E)- and (Z)-isomer by ligand change and controlling the reaction temperature.