Practical gram-scale synthesis of bicyclol metabolites M2 and M3.

Bicyclol, an innovative hepatoprotective drug, was approved by the Chinese National Medical Products Administration (NMPA) in 2001 to treat Hepatitis B and drug-induced liver injury. Two active metabolites of bicyclol have been identified as M2 and M3. To evaluate the impact on drug safety and efficacy of possible drug-drug interactions (DDIs) associated with these metabolites, a sufficient quantity of these metabolites is required. Herein, we report a concise novel route for the synthesis of M2 and M3 using the Suzuki-Miyaura coupling as the key step. Furthermore, we complete the gram-scale syntheses of M2 and M3.

Total Synthesis of (-)-Levesquamide.

The total synthesis of levesquamide, a natural product with an unprecedented pentasubstituted pyridine-isothiazolinone skeleton, has been accomplished from kojic acid for the first time. The key features of the synthesis include a Suzuki coupling reaction between bromopyranone and oxazolyl borate fragments, a copper-mediated introduction of a thioether, a mild hydrolysis of a pyridine 2-N-methoxyamide, and a Pummerer-type cyclization of a tert-butyl sulfoxide to form the key pyridine-isothiazolinone unit of the natural product.

Convenient synthesis of perhydrobenz[e]indene triketone, a key intermediate for the total synthesis of stelletins.

A complementary strategy for the formal total synthesis of (±)-stelletins is reported. Key reactions include a diastereoselective Eschenmoser-Claisen rearrangement, a highly diastereoselective alkylation of decalin-nitrile, and an intramolecular [3 + 2] cycloaddition/N-O reductive bond cleavage to construct the strained functionalized tricyclic core of (±)-stelletins.

Total synthesis of (±) commiphoranes C-D and their epimers.

(±) Commiphorane C, (±) commiphorane D, and their two isomers were synthesized through a linear synthesis strategy in 14 steps. Key features of the strategy include the construction of the relative configurations of C-5 and C-6 via aldehyde crotylation followed by the Mitsunobu reaction and ring A via an intramolecular Aldol reaction. The biological evaluation revealed that (±) commiphorane C and (±) isomer-1 significantly attenuated the overproduction of fibronectin, collagen I, and α-SMA in TGF-ß1-induced rat renal proximal tubular cells. Intermediate (±) 11 significantly decrease the overexpression of collagen I. Cytotoxicity studies showed that 1a-1d and (±) 11 were not toxic to NRK-52E cells.

(+)-Isocryptotanshinone derivatives and its simplified analogs as STAT3 signaling pathway inhibitors.

Isocryptotanshinone (ICTS), a natural product with potential signal transducer and activator of transcription-3 (STAT3) signaling pathway inhibitory activity, shows significant inhibitory activity against several tumors. In this study, a series of ICTS derivatives and simplified analogs containing a 1, 4-naphthoquinone core was designed, synthesized, and evaluated. The results demonstrated that most target compounds were potent STAT3 signaling pathway inhibitors based on their mechanism of inhibition of STAT3 phosphorylation. Moreover, based on the obtained data, the structure-activity relationship (SAR) was rationally deduced. Simultaneously, molecular docking of the compound 16r suggested its possible interaction mode with STAT3. To further verify anticancer activity, all target compounds were tested using HCT116, HepG2, MCF-7, A549, and U251 cell lines. Interestingly, compared with different tumor cell lines, the HCT-116 cell line was determined to be the most sensitive. Furthermore, compounds 21e, 16r, 28a, and 16e showed a dose-dependent inhibition of the growth of HCT116 cells. Thus, the SAR of ICTS derivatives and its simplified analogs was determined, and some of them were discovered to be potential anticancer candidates owing to their ability to inhibit the STAT3 signaling pathway.

Discovery of CAPE derivatives as dual EGFR and CSK inhibitors with anticancer activity in a murine model of hepatocellular carcinoma.

Caffeic acid phenethyl ester (CAPE), a bioactive component extracted from propolis of honeybee hives, can inhibit hepatocellular carcinoma (HCC). In order to explore more stable CAPE derivatives, 25 compounds were designed, synthesized, and pharmacologically assessed in vitro and in vivo as anti-tumor agents in HCC. Compounds 8d, 8f, 8l, 8j, and 8k showed favorable antiproliferative activity than other compounds including CAPE in the HCC cell lines. Based on the result of QTRP (Quantitative Thiol Reactivity Profiling), epidermal growth factor receptor (EGFR) and C-terminal Src kinase (CSK) were supposed to the targets of 8f, which was confirmed by binding mode analysis. Furthermore, compounds 8f, 8l, 8j, 8k, 8g, and 8h showed potent inhibitory effects against both CSK and EGFR than other derivatives in an ADP-Glo™ kinase assay. The representative compound, 8f, potently inhibited various tumor growth in murine model including murine hepatocellular carcinoma H22, meanwhile downregulating the EGFR/AKT pathway and enhancing T cell proliferation through inhibition of CSK. Metabolic stability in vitro suggested 8f and 8k were more stable in mouse plasma than CAPE and susceptible to metabolism in liver microsomes. The overall excellent profile of compound 8f makes it a potential candidate for further preclinical investigation.

Design, synthesis and biological evaluation of substituted (+)-SG-1 derivatives as novel anti-HIV agents.

SG-1 was previously identified as a potent Non-nucleoside reverse transcriptase inhibitors (NNRTI) which works through inhibition of reverse transcriptase (RT) RNA-dependent DNA polymerase activity via a direct binding event. To further investigate the relationship between its structure and activity, four series of novel analogues were designed and synthesized with 12 of them inhibiting HIV-1 replication with IC50s in the range 0.09-6.71 µM. Compound 4b, 4c, 4f, 2 and 6b were further tested on two NNRTI-resistant HIV-1 strains and one NNRTI-resistant superbug. The result showed that RT- E138K/M184V mutant virus conferred 4.7-9.1-fold resistance to 4c, 4f, 2 and 6b, but only showed slight resistance to 4b (2-fold) which was better than SG-1.

Design, synthesis of a novel 4-O-methylsaucerneol analogue LXY7824 as potent HIF-1 inhibitor and anti-cancer agent.

Hypoxia-inducible factor-1 (HIF-1), an important transcription factor for tumor survival, is an attractive target for anti-cancer treatment. Herein, we present the design and synthesis of LXY7824, a simplified analogue of 4-O-methylsaucerneol. In addition, its significant HIF-1 inhibitory activity and potent anti-cancer activity in vivo and in vitro were also reported.

Enantioselective total synthesis of colomitides and their absolute configuration determination and structural revision.

An efficient stereoselective synthetic approach to colomitides, 2,7-dioxabicyclo[3.2.1]octane-type natural products, is reported. Key steps are a stereocontrolled aldol reaction and a gold-catalyzed cycloisomerization. This synthetic strategy has been applied for the first asymmetric total synthesis of the proposed colomitides and their possible diastereomers. Comparison of their 1H and 13C NMR spectra and specific rotations with those of the natural product revealed that the structure of colomitide A should be revised to 1c, and that the absolute stereochemistries of colomitides A and B are 2'R,4R,5R,8S,1R and 2'R,4S,5R,8S,1R.

Discovery of Novel N-Substituted Prolinamido Indazoles as Potent Rho Kinase Inhibitors and Vasorelaxation Agents.

Inhibitors of Rho kinase (ROCK) have potential therapeutic applicability in a wide range of diseases, such as hypertension, stroke, asthma and glaucoma. In a previous article, we described the lead discovery of DL0805, a new ROCK I inhibitor, showing potent inhibitory activity (IC50 6.7 µM). Herein, we present the lead optimization of compound DL0805, resulting in the discovery of 24- and 39-fold more-active analogues 4a (IC50 0.27 µM) and 4b (IC50 0.17 µM), among other active analogues. Moreover, ex-vivo studies demonstrated that 4a and 4b exhibited comparable vasorelaxant activity to the approved drug fasudil in rat aortic rings. The research of a preliminary structure-activity relationship (SAR) indicated that the target compounds containing a ß-proline moiety have improved activity against ROCK I relative to analogues bearing an α-proline moiety, and among the series of the derivatives with a ß-proline-derived indazole scaffold, the inhibitory activity of the target compounds with a benzyl substituent is superior to those with a benzoyl substituent.

A practical synthesis of chiral tricyclic cyclopenta[b]benzofuran, a key intermediate of Beraprost.

A novel formal synthesis of Beraprost (1) is described. The tricyclic cyclopent[b]benzofuran core is efficiently prepared from (-)-Corey lactone diol in 12 steps with an overall yield of 37.4%. Key features of the strategy include a ring-closing metathesis reaction and aromatization to form the tricyclic cyclopenta[b]benzofuran framework, and selective halogenation/formylation to install the butyrate side-chain.

Total synthesis and stereochemical revision of xiamenmycin A.

The relative and absolute configurations of xiamenmycin A, a benzopyran compound isolated from Streptomyces xiamenensis 318 with a highly potent anti-fibrotic activity, have been characterized through the total synthesis. The key steps include the construction of the 3-chromanol moiety via Sharpless epoxidation followed by regio- and diastereo-selective cyclization and introduction of the threonine moiety at a later stage via Pd-catalysed aminocarbonylation in a one-pot procedure. The stereochemical assignment of natural xiamenmycin A has been accordingly revised to be 2R, 3S, 3'S, 4'R.

DL0805-2, a novel indazole derivative, relaxes angiotensin II-induced contractions of rat aortic rings by inhibiting Rho kinase and calcium fluxes.

AIM: DL0805-2 [N-(1H-indazol-5-yl)-1-(4-methylbenzyl) pyrrolidine-3-carboxamide] is a DL0805 derivative with more potent vasorelaxant activity and lower toxicity. This study was conducted to investigate the vasorelaxant mechanisms of DL0805-2 on angiotensin II (Ang II)-induced contractions of rat thoracic aortic rings in vitro. METHODS: Rat thoracic aortic rings and rat aortic vascular smooth muscle cells (VSMCs) were pretreated with DL0805-2, and then stimulated with Ang II. The tension of the aortic rings was measured through an isometric force transducer. Ang II-induced protein phosphorylation, ROS production and F-actin formation were assessed with Western blotting and immunofluorescence assays. Intracellular free Ca(2+) concentrations were detected with Fluo-3 AM. RESULTS: Pretreatment with DL0805-2 (1-100 µmol/L) dose-dependently inhibited the constrictions of the aortic rings induced by a single dose of Ang II (10(-7) mol/L) or accumulative addition of Ang II (10(-10)-10(-7) mol/L). The vasodilatory effect of DL0805-2 was independent of endothelium. In the aortic rings, pretreatment with DL0805-2 (1, 3, and 10 µmol/L) suppressed Ang II-induced Ca(2+) influx and intracellular Ca(2+) mobilization, and Ang II-induced phosphorylation of two substrates of Rho kinase (MLC and MYPT1). In VSMCs, pretreatment with DL0805-2 (1, 3, and 10 µmol/L) also suppressed Ang II-induced Ca(2+) fluxes and phosphorylation of MLC and MYPT1. In addition, pretreatment with DL0805-2 attenuated ROS production and F-actin formation in the cells. CONCLUSION: DL0805-2 exerts a vasodilatory action in rat aortic rings through inhibiting the Rho/ROCK pathway and calcium fluxes.

Total synthesis of xiamenmycin C and all of its stereoisomers: stereochemical revision.

Xiamenmycin C, a potent anti-fibrotic natural product, and all of its stereoisomers have been synthesized and their structures were fully characterized. Based on this study, the originally proposed structure of xiamenmycin C has been accordingly revised to be 2R,3S.

Vasodilatory effect of a novel Rho-kinase inhibitor, DL0805-2, on the rat mesenteric artery and its potential mechanisms.

PURPOSE: In the present study, we investigated the vasodilatory effect of a novel scaffold Rho-kinase inhibitor, DL0805-2, on isolated rat arterial rings including mesenteric, ventral tail, and renal arteries. We also examined the potential mechanisms of its vasodilatory action using mesenteric artery rings. METHODS: A DMT multiwire myograph system was used to test the tension of isolated small arteries. Several drugs were employed to verify the underlying mechanisms. RESULTS: DL0805-2 (10(-7)-10(-4) M) inhibited KCl (60 mM)-induced vasoconstriction in three types of small artery rings (pEC50: 5.84 ± 0.03, 5.39 ± 0.03, and 5.67 ± 0.02 for mesenteric, renal, and ventral tail artery rings, respectively). Pre-incubation with DL0805-2 (1, 3, or 10 µM) attenuated KCl (10-60 mM) and angiotensin II (AngII; 10(-6) M)-induced vasoconstriction in mesenteric artery rings. The relaxant effect on the rat mesenteric artery was partially endothelium-dependent (pEC50: 6.02 ± 0.05 for endothelium-intact and 5.72 ± 0.06 for endothelium-denuded). The influx and release of Ca(2+) were inhibited by DL0805-2. In addition, the increased phosphorylation levels of myosin light chain (MLC) and myosin-binding subunit of myosin phosphatase (MYPT1) induced by AngII were blocked by DL0805-2. However, DL0805-2 had little effect on K(+) channels. CONCLUSIONS: The present results demonstrate that DL0805-2 has a vasorelaxant effect on isolated rat small arteries and may exert its action through the endothelium, Ca(2+) channels, and the Rho/ROCK pathway.

Total synthesis of (+/-)-4-demethylenglerin A.

Racemic 4-demethylenglerin A (1'), a simplified analog of the guaiane-type sesquiterpene englerin A (1), has been synthesized. The cyclic hydrocarbon core structure was built through modified Metz approach using epoxynitrile cyclization and direct Aldol reaction to prepare the precursor of RCM. The primary cytotoxicity test summarized that C4 methyl has marked impacts on the bioactivity.

New bysspectin A derivatives as potent inhibitors of human carboxylesterase 2A.

Human carboxylesterase 2A (hCES2A), the most abundant carboxylesterase in the human gut, plays a crucial role in the metabolic clearance and activation of various ester-bearing drugs, environmental toxins and carcinogens. Inhibition of intestinal hCES2A can alleviate irinotecan-induced gut toxicity and modulate the oral bioavailability of hCES2A-substrate drugs. Bysspectin A, a natural product isolated from the endophytic fungus Byssochlamys spectabilis, has been identified as a highly selective hCES2A inhibitor. Herein, two sets of bysspectin A derivatives have been designed and synthesized, utilizing a Cu-catalyzed domino Sonogashira-cyclization as the key step. Following two rounds of structure activity relationship (SAR) studies and structural optimizations, compound 20w was identified as the most potent hCES2A inhibitor, with an IC50 value of 1.6 nM, an approximately 1000-fold improvement over bysspectin A. Further investigation showed that 20w potently inhibited hCES2A in a mixed inhibition manner, while this agent could also potently inhibit intracellular hCES2A in living cells and exhibited suitable metabolic stability. In summary, our findings demonstrate that a new bysspectin A derivative (20w) is a promising candidate for the development of clinically used hCES2A inhibitor.

The vasorelaxant mechanisms of a Rho kinase inhibitor DL0805 in rat thoracic aorta.

Rho-kinase has been suggested as a potential therapeutic target in the treatment of cardiovascular diseases. The Rho-kinase signaling pathway is substantially involved in vascular contraction. The aim of the present study was to evaluate the vasorelaxant effects of Rho kinase inhibitor DL0805 in isolated rat aortic rings and to investigate its possible mechanism(s). It was found that DL0805 exerted vasorelaxation in a dose-dependent manner in NE or KCl-induced sustained contraction and partial loss of the vasorelaxation under endothelium-denuded rings. The DL0805-induced vasorelaxation was significantly reduced by the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine methyl ester, the guanylate cyclase inhibitor methylene blue and the cyclooxygenase inhibitor indomethacin. The voltage-dependent K⁺ channel blocker 4-aminopyridine remarkably attenuated DL0805-induced relaxations. However, the ATP-sensitive K⁺ channel blocker glibenclamide and Ca²âº-activated K⁺ channel blocker tetraethylammonium did not affect the DL0805-induced relaxation. In the endothelium-denuded rings, DL0805 also reduced NE-induced transient contraction and inhibited contraction induced by increasing external calcium. These findings suggested that DL0805 is a novel vasorelaxant compound associated with inhibition of Rho/ROCK signaling pathway. The NO-cGMP pathway may be involved in the relaxation of DL0805 in endothelium-intact aorta. The vasorelaxant effect of DL0805 is partially mediated by the opening of the voltage-dependent K⁺ channels.

Total Synthesis of the Proposed Structure of Characellide B.

We achieved the total synthesis of the proposed structure of characellide B, a novel lipoglycotripeptide. Comparison of the data for the synthetic compound with those for the natural product indicated some possible errors in the original structural assignment. Furthermore, we synthesized the other four stereoisomers, focusing on the d-Asp-d-allo-Thr fragment, to determine the actual structure of characellide B. Nevertheless, the data for the stereoisomers were not consistent with those for the natural product.

Concise total synthesis of largazole.

The concise total synthesis of largazole was accomplished. The key step included the use of the Nagao thiazolidinethione auxiliary for the diastereoselective acetate aldol reaction and it acts as an acylating agent for the peptide formation.