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Habiterpenol is a G2 checkpoint inhibitor isolated from the culture broth of Phytohabitans sp. 3787_5. Here, we report the synthesis of new habiterpenol analogs through the total synthesis process of habiterpenol and evaluating the analogs for G2 checkpoint inhibitory activity. We investigated two different synthetic approaches for total synthesis, with intramolecular conjugate addition and Ti(III)-mediated radical cyclization as key reactions. Although the former was unsuccessful, the latter reaction facilitated stereoselective total synthesis and determination of the absolute configuration of habiterpenol. The extension of these chemistries to a structure-activity relationship (SAR) study gave new habiterpenol analogs, which could not be derived from natural habiterpenol and only be synthesized by applying the total synthesis. Therefore, this study provides important insights into SAR studies of habiterpenol.

Background: In clinical practice, a mixed suspension of clopidogrel bisulfate and magnesium oxide (MgO) tablets is administered frequently via a feeding tube. However, there is no report on the changes occurring when suspensions of these two drugs are combined, including the effects or potential decrease in dose following tube administration. Thus, the purpose of our study was to investigate the (i) changes caused by mixing clopidogrel bisulfate (ion form) and MgO tablets and (ii) effects on the administered clopidogrel dose after passing through a feeding tube., Methods: The molecular structure of clopidogrel generated in a mixture of clopidogrel bisulfate and a basic compound, such as sodium bicarbonate or MgO tablet, was determined by 1 H-NMR after extraction and purification. The suspension of clopidogrel bisulfate tablet alone and the mixed suspension of clopidogrel bisulfate tablet and MgO tablet were passed through a feeding tube. We compared the yield of the molecular form of clopidogrel from each passed fraction., Results: The substance obtained from the mixture of clopidogrel bisulfate tablet and sodium bicarbonate or MgO tablet was identified as the molecular form of clopidogrel, and chemical degradation did not occur under these conditions. In the tube passage test, the yield of clopidogrel (molecular form) from the mixture of clopidogrel bisulfate and MgO tablets was lower than that from the suspension of clopidogrel bisulfate tablet alone., Conclusions: The mixture of clopidogrel bisulfate and MgO tablets caused a considerable reduction in the administered dose passed through the feeding tube. Therefore, it is recommended to administer the suspensions of clopidogrel bisulfate and MgO tablets separately for safe and effective pharmacotherapy.

The Ginkgo biloba metabolite bilobalide is widely ingested by humans but its effect on the mammalian central nervous system is not fully understood 1-4 . Antagonism of γ-aminobutyric acid A receptors (GABA A Rs) by bilobalide has been linked to the rescue of cognitive deficits in mouse models of Down syndrome 5 . A lack of convulsant activity coupled with neuroprotective effects have led some to postulate an alternative, unidentified target 4 ; however, steric congestion and the instability of bilobalide 1,2,6 have prevented pull-down of biological targets other than the GABA Α Rs. A concise and flexible synthesis of bilobalide would facilitate the development of probes for the identification of potential new targets, analogues with differential selectivity between insect and human GABA Α Rs, and stabilized analogues with an enhanced serum half-life 7 . Here we exploit the unusual reactivity of bilobalide to enable a late-stage deep oxidation that symmetrizes the molecular core and enables oxidation states to be embedded in the starting materials. The same overall strategy may be applicable to G. biloba congeners, including the ginkgolides-some of which are glycine-receptor-selective antagonists 8 . A chemical synthesis of bilobalide should facilitate the investigation of its biological effects and its therapeutic potential.

Nafuredin-γ, obtained from natural nafuredin, has demonstrated a potent and selective inhibitory activity against nematode complex I. However, nafuredin-γ is unstable in air since its conjugated dienes are oxygen-labile. The instability in air was naturally solved by the synthesis of structure-simplified nafuredin-γ analogs without conjugated dienes. However, these modified analogs showed lower complex I inhibitory activities. Therefore, new air-stable structure-simplified nafuredin-γ analogs were designed and synthesized herein. Among all analogs synthesized, the one bearing a unique 1-azabicyclo[3.1.0]hexane scaffold showed the highest inhibitory activity (IC 50 =170 nM) while presenting high selectivity against nematode complex I.

The targets of antifungal antibiotics in clinical use are more limited than those of antibacterial antibiotics. Therefore, new antifungal antibiotics with different mechanisms of action are desired. In the course of our screening for antifungal antibiotics of microbial origins, new antifungal antibiotics, simplifungin (1) and valsafungins A (2) and B (3), were isolated from cultures of the fungal strains Simplicillium minatense FKI-4981 and Valsaceae sp. FKH-53, respectively. The structures of 1 to 3 including their absolute stereochemistries were elucidated using various spectral analyses including NMR and collision-induced dissociation (CID)-MS/MS as well as chemical approaches including modifications to the Mosher's method. They were structurally related to myriocin. They inhibited the growth of yeast-like and zygomycetous fungi with MICs ranging between 0.125 and 8.0 μg/mL. An examination of their mechanisms of action by the newly established assay using LC-MS revealed that 1 and 2 inhibited serine palmitoyltransferase activity, which is involved in sphingolipid biosynthesis, with IC50 values of 224 and 24 nM, respectively.

Cyslabdan was isolated from the culture broth of Streptomyces sp. K04-0144 as a new potentiator of imipenem activity against methicillin-resistant Staphylococcus aureus. We accomplished the synthesis of cyslabdan according to a previously reported structure. However, we subsequently found that this structure was incorrect; our analysis of natural cyslabdan showed that it possessed R stereochemistry at the C8 position, not S, as had previously been reported. Thus, we completed the protecting-group-free synthesis of the correct structure of cyslabdan, which is described herein.

Sterol O-acyltransferase 2 (SOAT2; also known as ACAT2) is considered as a new therapeutic target for the treatment or prevention of hypercholesterolemia and atherosclerosis. Fungal pyripyropene A (PPPA: 1,7,11-triacyl type), the first SOAT2-selective inhibitor, proved orally active in vivo using atherogenic mouse models. The purpose of the present study was to demonstrate that the PPPA derivatives (PRDs) prove more effective in the mouse models than PPPA. Among 196 semisynthetic PPPA derivatives, potent, SOAT2-selective, and stable PRDs were selected. In vivo antiatherosclerotic activity of selected PRDs was tested in apolipoprotein E knockout (Apoe(-/-)) mice or low-density lipoprotein receptor knockout (Ldlr(-/-)) mice fed a cholesterol-enriched diet (0.2% cholesterol and 21% fat) for 12 weeks. During the PRD treatments, no detrimental side effects were observed. Among three PRDs, Apoe(-/-) mice treated with PRD125 (1-,11-O-benzylidene type) at 1 mg/kg/day had significantly lower total plasma cholesterol concentration by 57.9 ± 9.3%; further, the ratio of cholesteryl oleate to cholesteryl linoleate in low-density lipoprotein was lower by 55.6 ± 7.5%, respectively. The hepatic cholesteryl ester levels and SOAT2 activity in the small intestines and livers of the PRD-treated mice were selectively lowered. The atherosclerotic lesion areas in the aortae of PRD125-treated mice were significantly lower at 62.2 ± 13.1%, respectively. Furthermore, both PRDs were also orally active in atherogenic Ldlr(-/-) mice. Among the PRDs tested, PRD125 was the most potent in both mouse models. These results suggest that SOAT2-selective inhibitors such as PRD125 have a high potential as poststatin agents for treatment and/or prevention in patients with atherosclerosis and hypercholesterolemia., (Copyright © 2015 by The American Society for Pharmacology and Experimental Therapeutics.)

Pyripyropene A (PPPA, 1) of fungal origin, a selective inhibitor of acyl-CoA:cholesterol acyltransferase 2 (ACAT2), proved orally active in atherogenic mouse models. The in vitro metabolites of 1 in liver microsomes and plasma of human, rabbit, rat and mouse were analyzed by ultra fast liquid chromatography and liquid chromatography/tandem mass spectrometry. In the liver microsomes from all species, successive hydrolysis occurred at the 1-O-acetyl residue, then at the 11-O-acetyl residue of 1, while the 7-O-acetyl residue was resistant to hydrolysis. Furthermore, dehydrogenation of the newly generated 11-alcoholic hydroxyl residue occurred in human and mouse-liver microsomes, while oxidation of the pyridine ring occurred in human and rabbit liver microsomes. On the other hand, hydrolysis of the 7-O-acetyl residue proceeded only in the mouse plasma. These data indicated that the in vitro metabolic profiles of 1 have subtle differences among animal species. All of the PPPA metabolites observed in liver microsomes and plasma markedly decreased ACAT2 inhibitory activity. These findings will help us to synthesize new PPPA derivatives more effective in in vivo study than 1.

The stereoselective total synthesis of atpenins A4 (2) and B (3), harzianopyridone (4), and NBRI23477 B (5) have been developed using a convergent approach involving the coupling reaction of a common iodopyridine with an aldehyde corresponding to the appropriate side chain of the desired compound. Furthermore, the absolute configurations of atpenin B (3), harzianopyridone (4), and NBRI23477 B (5) have been unambiguously determined.

Most cancer cells have mutations in genes at the G1 checkpoint and repair DNA only in the G2 phase; therefore, the G2 checkpoint is a potential target to develop novel therapy. In the course of screening, a known compound, pycnidione, was isolated from the fungal culture broth of Gloeotinia sp. FKI-3416. Pycnidione irreversibly abrogated bleomycin-induced G2 arrest in Jurkat cells and synergically potentiated the cytotoxicity of bleomycin. To elucidate the mechanism of action, the effect of pycnidione on the signal transduction of the G2 checkpoint was analyzed, showing that the increased phospho-cyclin dependent kinase-1 (CDK1) level caused by bleomycin was abrogated in the presence of pycnidione, indicating that cells did not arrest at the G2 phase. Moreover, under these conditions, Chk1 and Chk2 levels were markedly down-regulated. Thus, we concluded that pycnidione abrogated bleomycin-induced G2 arrest by decreasing Chk1 and Chk2.

Enantioselective total synthesis of atpenin A5, a potent mitochondrial complex II (succinate-ubiquinone oxidoreductase) inhibitor, has been achieved by a convergent approach through a coupling reaction between 5-iodo-2,3,4,6-tetraalkoxypyridine and a side-chain aldehyde. The two key segments were synthesized through ortho-metalation/boronation with (MeO)3B/oxidation with mCPBA, ortho-iodination, halogen dance reaction, Sharpless epoxidation and regioselective epoxide-opening reaction. This synthetic study resulted in the revision of the earlier reported 1H-NMR data of the natural atpenin A5 and the confirmation of the stereochemical assignment.

Selectivity of 96 semisynthetic derivatives prepared from fungal pyripyropene A, originally isolated as a potent inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), toward ACAT1 and ACAT2 isozymes was investigated in the cell-based assay using ACAT1- and ACAT2-expressing CHO cells. Eighteen derivatives including PR-71 (7-O-isocaproyl derivative) showed much more potent ACAT2 inhibition (IC50: 6.0 to 62 nM) than pyripyropene A (IC50: 70 nM). Among them, however, natural pyripyropene A showed the highest selectivity toward ACAT2 with a selectivity index (SI) of >1000, followed by PR-71 (SI, 667).

Aims: To clarify the mechanism for cellular uptake of fluvastatin (FV) into rat primary cultured hepatocytes and human aortic endothelial cells (HAEC)., Methods: Rat primary cultured hepatocytes and Endocell-AO as normal human aortic endothelial cells were used. Effects of incubation time, concentration- and temperature-dependency on cellular FV uptake were investigated after incubation with [14C]-FV and its enantiomers, (+)-FV and (-)-FV. Rat primary cultured hepatocytes were washed with either Na+-containing buffer or Na+-free buffer and incubated with metabolic inhibitors or bile acids. Intracellular radioactivity was measured by liquid scintillation counting. The determination of intracellular unchanged FV and its enantiomers was carried out by stereospecific h.p.l.c., Results: In rat cultured hepatocytes, concentration- and temperature-dependent saturable uptake of [14C]-FV was observed (Km=37.6 microm, V max=869 pmol (mg protein)-1 min-1 ), suggesting a specific uptake mechanism. The uptake of each enantiomer also showed a specific uptake mechanism as observed for the racemate with no difference between enantiomers; (+)-FV, Km=38.5 microm, V max=611 pmol (mg protein)-1 min-1, (-)-FV, Km=41.5 microm, V max=646 pmol (mg protein)-1 min-1. In the presence of cholate and taurocholate, the uptake of FV was inhibited by 39-46%. Pravastatin inhibited FV uptake by 29%. In the absence of Na+, the uptake of FV was markedly inhibited 91-96% by bile acid. The uptake of FV into HAEC at 37 degrees C and 4 degrees C increased with the concentration of FV, but no saturable uptake was observed., Conclusions: FV transport system may be, at least in part, Na+- and ATP-dependent, and may have some features in common with the bile acid transport system and the organic anion transport system. Since saturable uptake was not observed in HAEC, FV appears to be taken up into these cells mainly via nonspecific simple diffusion.

Background: The pharmacological properties of EM523, a nonpeptide motilin agonist, have not been well characterized., Methods: The prokinetic effect of EM523 on motor-stimulating activity in the stomach, duodenum, and jejunum in seventeen conscious dogs was studied using force transducers implanted long term. EM523 (0.3-10.0 micrograms/kg) and receptor antagonists were injected intravenously during the interdigestive state., Results: EM523 induced phase III-like contractions in a dose-dependent manner, and the contractions were inhibited dose dependently by pretreatment with cholinergic and 5-HT3 receptor antagonists and dopamine but not by adrenoceptor and opiate antagonists or methysergide. The plasma immunoreactive motilin level was increased after EM523 to 60% of the mean maximum value during the spontaneous phase III contractions. Pretreatment with anti-canine motilin serum inhibited EM523-induced contractions by 19.2% in the motor index, but the contractile pattern was not affected., Conclusions: EM-523-induced phase III-like contractions are brought about through the cholinergic neural pathway and 5-HT3 receptors, and endogenous motilin release is partially involved.

Simvastatin was more effectively metabolized by the liver microsomes of male rats than females. The sex difference appeared in the composition of the metabolites. Two male-specific metabolites were identified by NMR and mass spectrometry as 3''-hydroxy and 3',3''-dihydroxy-delta 4',5' derivatives of simvastatin.