Search

Losartan is an anti-hypertensive angiotensin II (ANGII) type 1 receptor (AT1R) blocker (ARB) with many unexpected therapeutic properties, even in non-blood pressure (BP)-related diseases. Administered as a prodrug, losartan undergoes serial metabolism into EXP3179, a metabolite alleged to lack AT1R-blocking properties, and EXP3174, the dominant AT1R antagonist. Having observed that losartan can decrease vascular tone in mice with low AT1R expression and inhibit Marfan aortic widening at very high doses, we investigated whether EXP3179 may have unique, AT1R-independent effects on vascular tone and endothelial function.We compared the AT1R blocking capabilities of EXP3179 and EXP3174 using AT1R-expressing cell lines. Their BP lowering and vasoactive properties were studied in normal, hypertensive and transgenic rodents, and ex vivo wire myography.We observed that both EXP3179 and EXP3174 can fully block (100%) AT1R signaling in vitro and significantly decrease BP in normotensive and spontaneously hypertensive rats. Only EXP3179 prevented PE-induced contraction by up to 65% (p 0.01) in L-NAME and endothelium removal-sensitive fashion. Use of transgenic mice revealed that these effects involve the eNOS/caveolin-1 axis and the endothelium-dependent hyperpolarization factor (EDHF).We provide direct structure-activity evidence that EXP3179 is a BP-lowering AT1R blocker with unique endothelial function-enhancing properties not shared with losartan or EXP3174. The major pharmacological effects of losartan in patients are therefore likely more complex than simple blockade of AT1R by EXP3174, which helps rationalize its therapeutic and prophylactic properties, especially at very high doses. Reports relying on EXP3179 as an AT1R-independent losartan analogue may require careful re-evaluation.

This paper describes a synthesis of ALC-0315 by a sequence that more than doubles the overall yield relative to the published one, and that employs much cleaner reactions, thereby facilitating purifications to a considerable extent.

The regulatory approval of Onpattro, a lipid nanoparticle-based short interfering RNA drug for the treatment of polyneuropathies induced by hereditary transthyretin amyloidosis, paves the way for clinical development of many nucleic acid-based therapies enabled by nanoparticle delivery.

Successfully employing therapeutic nucleic acids, such as small interfering RNA (siRNA), requires chemical modifications or the use of nanocarrier technology to prevent their degradation in the circulation and to facilitate intracellular delivery. Lipid nanoparticles (LNP) are among the most advanced nanocarriers culminating in the first siRNA therapeutic’s clinical translation and approval. At the same time, their applicability as modular platform technology due to the interchangeable building blocks and siRNA payload hallmarks one of LNPs’ major advantages. In addition, drug derivatization approaches to synthesize lipophilic small molecule prodrugs enable stable incorporation in LNPs. This provides ample opportunities to develop combination therapies by co-encapsulating multiple therapeutic agents in a single formulation. Here, we describe how the modular LNP platform can be applied for combined gene silencing and chemotherapy to induce additive anti-cancer effects. We show that various lipophilic taxane prodrug derivatives and siRNA against the androgen receptor, a prostate cancer driver, can be efficiently and stably co-encapsulated in LNPs. In addition, we demonstrate that prodrug incorporation does not affect LNPs’ gene silencing ability and that the combination therapy induces additive therapeutic effects in vitro. Using a double-radiolabeling approach, we quantitively determined the LNPs’ and prodrugs’ pharmacokinetic properties and biodistribution following systemic administration in tumor-bearing mice. Our results indicate that co-encapsulation of siRNA and lipophilic prodrugs into LNPs is an attractive and straightforward approach for combination therapy development.GRAPHICAL ABSTRACT

Marfan syndrome (MFS) is a connective tissue disorder caused by mutations in the FBN1 gene, which encodes fibrillin-1, a protein essential for the formation and stabilization of elastic fibers as well as signaling homeostasis. Progressive aortic root widening is the most serious manifestation of MFS as it can lead to aortic dissection, aneurysm formation and rupture. However, despite their ability to decrease the hemodynamic stress the aorta is subjected to, anti-hypertensive medications often lead to underwhelming reductions in the rate of aortic root dilation, which illustrates how fragmental our understanding of MFS-associated aortic remodeling is. This manuscript summarizes recent evidence that document nitric oxide (NO) synthase (NOS)-related changes to the vasculature during the pathogenesis of MFS and how they result in a unique state of vascular dysfunction that likely plays a causal role in the aortic root widening process. We also review how clinic-approved and experimental therapies as well lifestyle approaches may promote aortic root stability by correcting NO homeostasis, which if properly optimized may improve outcomes in this population afflicted by a notoriously refractory type of aortopathy.

A chiral aryl iodide promotes the enantioselective oxidative cyclization of 1-naphtholic sulfonamides, albeit in moderate ee and low yield. The products tend to crystallize as conglomerates. Recrystallization thus increases their ee to > 99% ee. This highly enantioenriched material provides seed crystals for the resolution of the racemate (prepared in high yield by oxidative cyclization with (diacetoxyiodo)benzene in trifluoroacetic acid) by coupled preferential crystallization. This enables the production of significant quantities of highly enantioenriched products, despite the low efficiency of the enantioselective reaction.

A chiral aryl iodide enables the catalytic, oxidative kinetic resolution of various 2-[(3-hydroxy-2-alkyl)propyl]naphthalen-1-ols.

BACKGROUND AND PURPOSE Attempts to generate active site-directed cathepsin K (CatK) inhibitors for the treatment of osteoporosis have failed because of side effects. We have previously shown that an ectosteric tanshinone CatK inhibitor isolated from Salvia miltiorrhiza blocked, selectively, the collagenase activity of CatK, without affecting the active site and demonstrated its bone-preserving activity in vivo. Here, we have characterize the antiresorptive potential of other tanshinones, which may provide a scaffold for side effect-free CatK inhibitors. EXPERIMENTAL APPROACH Thirty-one tanshinones were tested for their activity against CatK in enzymic and cell-based assays. The inhibitory potency against triple helical and fibrillar collagen degradation was determined in enzymic assays, by scanning electron microscopy and mechanical strength measurements. Human osteoclast assays were used to determine the effects of the inhibitors on bone resorption, its reversibility and osteoclastogenesis. Binding sites were characterized by molecular docking. KEY RESULTS Twelve compounds showed highly effective anti-collagenase activity and protected collagen against destruction and mechanical instability without inhibiting the hydrolysis of non-collagenous substrates. Six compounds were highly effective in osteoclast bone resorption assays with IC50 values of

Aryl iodides that are unreactive toward various diaryliodonium triflates undergo metathesis reaction with λ 3 -iodanes based on a highly nucleofugal aryl iodide such as 2-iodothiophene. Examples of such reactive iodanes include phenyl(2-thienyl)iodonium triflate and bis-(2-thienyl)iodonium triflate. This observation provides support for a mechanistic hypothesis advanced earlier.

A catalyst-free heterocyclization reaction of &alpha, chloroglycinates with thiobenzamides or thioureas leading to 2,4-disubstituted-5-acylamino-1,3-thiazoles has been developed. The methodology provides straightforward access to valuable building blocks for pharmaceutically relevant compounds.

In order to identify structural features of pyrimethamine (5-(4-chlorophenyl)-6-ethylpyrimidine-2,4-diamine) that contribute to its inhibitory activity (IC50 value) and chaperoning efficacy toward β-N-acetylhexosaminidase, derivatives of the compound were synthesized that differ at the positions bearing the amino, ethyl, and chloro groups. Whereas the amino groups proved to be critical to its inhibitory activity, a variety of substitutions at the chloro position only increased its IC50 by 2–3-fold. Replacing the ethyl group at the 6-position with butyl or methyl groups increased IC50 more than 10-fold. Surprisingly, despite its higher IC50, a derivative lacking the chlorine atom in the para-position was found to enhance enzyme activity in live patient cells a further 25% at concentrations >100 μM, while showing less toxicity. These findings demonstrate the importance of the phenyl group in modulating the chaperoning efficacy and toxicity profile of the derivatives.

The successful oxidative spirocyclization of 1- or 2-naphtholic sulfonamides extends oxidative amidation methods to the naphthalene series. A method to prepare N-unsubstituted spirolactam derivatives of 1-naphthol is also presented.

The catalytic, enantioselective oxidative cyclization of naphthol-derived carboxylic acids mediated by chiral hypervalent iodine reagents has been studied extensively in the recent past, but analogous reactions of non-carboxylic substrates are yet unknown. This paper describes a catalytic, enantioselective, hypervalent iodine-promoted oxidative cycloetherification reaction of naphtholic alcohols. The new process relies on a variant of the Uyanik–Ishihara catalyst, in which the stereogenic centers have been relocated closer to the iodine atom. The new catalyst design affords optical yields comparable to those available with Uyanik–Ishihara iodides, but chemical yields are sensibly higher, at least with the tests substrates. An even more problematic reaction is the catalytic, enantioselective oxidative cyclization of naphtholic sulfonamides. In this case, the new catalyst affords significantly higher optical inductions than Uyanik–Ishihara iodides. The kinetic resolution of particular naphtholic alcohols is demonstrated. The absolute configuration of a numver of enantioenriched compounds obtained in this study was ascertained by X-ray diffractometry.

The therapeutic applications of lipid nanoparticle (LNP) formulations of small interfering RNA (siRNA), are hampered by inefficient delivery of encapsulated siRNA to the cytoplasm following endocytosis. Recent work has shown that up to 70% of endocytosed LNP-siRNA particles are recycled to the extracellular medium and thus cannot contribute to gene silencing. Niemann-Pick type C1 (NPC1) is a late endosomal/lysosomal membrane protein required for efficient extracellular recycling of endosomal contents. Here we assess the influence of NP3.47, a putative small molecule inhibitor of NPC1, on the gene silencing potency of LNP-siRNA systems in vitro. Intracellular uptake and colocalization studies revealed that the presence of NP3.47 caused threefold or higher increases in accumulation of LNP-siRNA in late endosomes/lysosomes as compared with controls in a variety of cell lines. The gene silencing potency of LNP siRNA was enhanced up to fourfold in the presence of NP3.47. Mechanisms of action studies are consistent with the proposal that NP3.47 acts to inhibit NPC1. Our findings suggest that the pharmacological inhibition of NPC1 is an attractive strategy to enhance the therapeutic efficacy of LNP-siRNA by trapping LNP-siRNA in late endosomes, thereby increasing opportunities for endosomal escape.

A route to a racemic diene intermediate for the synthesis of tetrodotoxin is described. Key steps of the sequence leading to such a compound include the oxidative amidation of a phenol, a Cu(II)-catalyzed cyclocondensation of a nitroketone with an olefin (Machetti-DeSarlo reaction), and a nucleophilic fragmentation of the resulting isoxazoline. Several unusual reactions encountered in the course of this study are thoroughly discussed.

A catalyst consisting of 1 mol % of the 1:2 complex of Pd(OAc)2 with N-(4-carbethoxyphenyl)urea promotes the Heck arylation of 2- or 3-substituted, conjugated esters, nitriles, aldehydes, and ketones (an uncharacteristically broad range of substrates), but only with electron-rich aryl iodides (an uncharacteristically narrow range of halides).

A catalyst consisting of the 1:2 complex of Pd(OAc)2 (1 mol %) with N-(4-carbethoxy)-phenylurea promotes the Heck arylation of a range of crotonic and cinnamic substrates, including aldehydes, ketones, esters, and nitriles, with electron-rich—but not electron-deficient—aryl iodides.

The in vivo gene silencing potencies of lipid nanoparticle (LNP)-siRNA systems containing the ionizable cationic lipids DLinDAP, DLinDMA, DLinKDMA, or DLinKC2-DMA can differ by three orders of magnitude. In this study, we examine the uptake and intracellular processing of LNP-siRNA systems containing these cationic lipids in a macrophage cell-line in an attempt to understand the reasons for different potencies. Although uptake of LNP is not dramatically influenced by cationic lipid composition, subsequent processing events can be strongly dependent on cationic lipid species. In particular, the low potency of LNP containing DLinDAP can be attributed to hydrolysis by endogenous lipases following uptake. LNP containing DLinKC2-DMA, DLinKDMA, or DLinDMA, which lack ester linkages, are not vulnerable to lipase digestion and facilitate much more potent gene silencing. The superior potency of DLinKC2-DMA compared with DLinKDMA or DLinDMA can be attributed to higher uptake and improved ability to stimulate siRNA release from endosomes subsequent to uptake.This study reports on the in vivo gene silencing potency of lipid nanoparticle-siRNA systems containing ionizable cationic lipids. It is concluded that the superior potency of DLinKC2-DMA compared with DLinKDMA or DLinDMA can be attributed to their higher uptake thus improved ability to stimulate siRNA release from endosome.

The androgen receptor (AR) plays a critical role in the progression of prostate cancer. Silencing this protein using short-hairpin RNA (shRNA) has been correlated with tumor growth inhibition and decreases in serum prostate specific antigen (PSA). In our study, we have investigated the ability of lipid nanoparticle (LNP) formulations of small-interfering RNA (siRNA) to silence AR in human prostate tumor cell lines in vitro and in LNCaP xenograft tumors following intravenous (i.v.) injection. In vitro screening studies using a panel of cationic lipids showed that LNPs containing the ionizable cationic lipid 2,2-dilinoleyl-4-(2-dimethylaminoethyl)-[1,3]-dioxolane (DLin-KC2-DMA) exhibited the most potent AR silencing effects in LNCaP cells. This is attributed to an optimized ability of DLin-KC2-DMA-containing LNP to be taken up into cells and to release the siRNA into the cell cytoplasm following endocytotic uptake. DLin-KC2-DMA LNPs were also effective in silencing the AR in a wild-type AR expressing cell line, LAPC-4, and a variant AR expressing cell line, CWR22Rv1. Importantly, it is demonstrated that LNP AR-siRNA systems containing DLin-KC2-DMA can silence AR gene expression in distal LNCaP xenograft tumors and decrease serum PSA levels following i.v. injection. To our knowledge, this is the first report demonstrating the feasibility of LNP delivery of siRNA for silencing AR gene expression in vivo.

Lipid nanoparticles (LNPs) are currently the most effective in vivo delivery systems for silencing target genes in hepatocytes employing small interfering RNA. Antigen-presenting cells (APCs) are also potential targets for LNP siRNA. We examined the uptake, intracellular trafficking, and gene silencing potency in primary bone marrow macrophages (bmMΦ) and dendritic cells of siRNA formulated in LNPs containing four different ionizable cationic lipids namely DLinDAP, DLinDMA, DLinK-DMA, and DLinKC2-DMA. LNPs containing DLinKC2-DMA were the most potent formulations as determined by their ability to inhibit the production of GAPDH target protein. Also, LNPs containing DLinKC2-DMA were the most potent intracellular delivery agents as indicated by confocal studies of endosomal versus cytoplamic siRNA location using fluorescently labeled siRNA. DLinK-DMA and DLinKC2-DMA formulations exhibited improved gene silencing potencies relative to DLinDMA but were less toxic. In vivo results showed that LNP siRNA systems containing DLinKC2-DMA are effective agents for silencing GAPDH in APCs in the spleen and peritoneal cavity following systemic administration. Gene silencing in APCs was RNAi mediated and the use of larger LNPs resulted in substantially reduced hepatocyte silencing, while similar efficacy was maintained in APCs. These results are discussed with regard to the potential of LNP siRNA formulations to treat immunologically mediated diseases.

The paper reviews the oxidation of oximes to nitrile oxides with hypervalent iodine reagents, especially PhI(OAc)2, and the synthetic uses of such a transformation. Side reactions attending the process are also discussed.

5-tert-Butoxycarbonylamino-5-carbethoxy-2-tert-butyldimethylsilyloxy-cyclopentadiene undergoes a Diels-Alder reaction exclusively from the face syn to the nitrogen functionality. Complete reversal of facial bias may be achieved, but at the cost of diminished reactivity, through steric shielding of the N-syn face.

The total synthesis of the thiopeptide antibiotic, thiocillin I, is described. This work unequivocally defines the full structure (constitution and configuration) of the natural product as 1.

Iodobenzene diacetate in MeOH containing a catalytic amount of TFA efficiently oxidizes aldoximes to nitrile oxides. The latter may be trapped in situ with olefins in a bimolecular or an intramolecular mode. The new method enables the execution of tandem oxidative dearomatization of phenols/intramolecular nitrile oxide cycloaddition sequences leading to useful synthetic intermediates.

A convergent approach to a macrocyclic compound embodying the complete "eastern" quadrant of diazonamides is described. The opening sequence in this work relies on an oxazole-forming reaction devised earlier in this group, while a late step involves a Robinson-Gabriel cyclization of an amidoketone to form a second oxazole.

A full account of the oxidative dearomatization of para- and ortho-phenolic sulfonamides is provided together with an overview of the chemistry of the products and their elaboration to building blocks for spirocyclic alkaloids. A concise total synthesis of putative lepadiformine complements the discussion.

The oxidative amidation of phenols effects the conversion of appropriately substituted phenols into 4-amidodienones (‘ para -oxidative amidation’) or 2-amidodienones (‘ ortho -oxidative amidation’) by the action of hypervalent iodine reagents. The reagent, (diacetoxyiodo)benzene (‘DIB’) is especially effective in these transformations. This paper focuses on techniques for the desymmetrization of the dienoes thus obtained, leading to the stereocontrolled creation of N -substituted spiro carbons. The methodology creates new opportunities in alkaloid synthesis, as apparent from a number of examples.

Hydrophobic uncharged drugs such as docetaxel are difficult to encapsulate and retain in liposomal nanoparticles (LNP). In this work we show that a weak base derivative of docetaxel can be actively loaded into LNP using pH gradient loading techniques to achieve stable drug encapsulation and controlled release properties. Docetaxel was derivatized at the hydroxyl group in the C-2' position to form an N-methyl-piperazinyl butanoic acid ester. The free hydroxyl group in this position is essential for anticancer activity and the prodrug has, therefore, to be converted into the parent drug (docetaxel) to restore activity. Cytotoxicity testing against a panel of cancer cell lines (breast, prostate and ovarian cancer) demonstrated that the prodrug is readily converted into active drug; the derivative was found to be as active as the parent drug in vitro. The docetaxel derivative can be efficiently loaded at high drug-to-lipid ratios (up to 0.4 mg/mg) into LNP using pH loading techniques. Pharmacokinetic, tolerability and efficacy studies in mice demonstrate that the LNP-encapsulated prodrug has the long drug circulation half-life required for efficient tumor accumulation (50-100 times higher drug plasma levels compared with free derivative and Taxotere, the commercial docetaxel formulation), is active in a xenograft model of breast cancer (MDA-MB-435/LCC6), and is well tolerated at i.v. doses of 3 times higher than the maximum tolerated dose (MTD) of the parent drug. This is the first demonstration that a therapeutically active, remote-loaded, controlled-release LNP formulation of a taxane can be achieved. The approach reported here has broad applicability to other approved drugs as well as new chemical entities.

Fungal infections are of small concern to healthy persons, but they can become life threatening in immunocompromised individuals, such as AIDS and cancer patients, as well as recipients of organ tr...

An oxidative cyclization of dienic sulfonamides mediated by iodobenzene diacetate in TFA, followed by a tandem intramolecular Diels-Alder reaction, achieves desymmetrization of a "locally symmetrical" dienone with good levels of diastereoselectivity and leads to valuable synthetic intermediates for the himandrine alkaloids.

We adopted a rational approach to design cationic lipids for use in formulations to deliver small interfering RNA (siRNA). Starting with the ionizable cationic lipid 1,2-dilinoleyloxy-3-dimethylaminopropane (DLinDMA), a key lipid component of stable nucleic acid lipid particles (SNALP) as a benchmark, we used the proposed in vivo mechanism of action of ionizable cationic lipids to guide the design of DLinDMA-based lipids with superior delivery capacity. The best-performing lipid recovered after screening (DLin-KC2-DMA) was formulated and characterized in SNALP and demonstrated to have in vivo activity at siRNA doses as low as 0.01 mg/kg in rodents and 0.1 mg/kg in nonhuman primates. To our knowledge, this represents a substantial improvement over previous reports of in vivo endogenous hepatic gene silencing.

An approach to tetrodotoxin that relies on the oxidative amidation of methyl 4-hydroxyphenylacetate as a key step is described. The stereoselective introduction of a beta-hydroxynitrile functionality on one of the double bonds of the emerging dienone is achieved through an intramolecular nitrile oxide cycloaddition-fragmentation sequence.

Avenues to bi- and tricyclic building blocks for the elaboration of sordaricin and its analogues are described. The target molecules were obtained through inter- and intramolecular Diels-Alder reactions of a number of previously unknown cyclopentadienes. Unusual properties of 3-cyanoenones and 1-cyanocyclopentadienes have been unveiled and circumvented.

This contribution reviews a family of reactions devised in our laboratory that effect the oxidative conversion of phenols into 4-amido-dienones. A salient feature of this chemistry is the use of hypervalent iodine reagents, especially diacetoxyiodobenzene (DIB), as uniquely capable oxidants in the context of the new transformation. The advent of this methodology has created new opportunities in alkaloid synthesis. Our efforts toward FR-901483, TAN-1251C, cylindricine C, and other nitrogenous natural products illustrate some applications in that domain. 1 Introduction 2 Background 3 First-Generation Oxidative Amidation of Phenols: The Oxazoline Route 4 Initial Applications: Total Synthesis of FR-901483 and of TAN-1251C 5 Second-Generation Oxidative Amidation of Phenols: Sulfonamide Technology 6 Applications: Total Synthesis of (-)-Cylindricine C 7 Third-Generation Solution: The Bimolecular Reaction 8 Conclusion

Oxidative amidation chemistry provides a unified route to aromatic Erythrina alkaloids through a sequence that illustrates new principles and improved conditions to effect a crucial eliminative Curtius–Schmidt rearrangement.

A facile method for the oxidative ortho-cyclization of 1- and 2-naphtholic sulfonamides as well as a new method for the preparation of N-unsubstituted spirolactam derivative (X) of 1-naphthol is given.

In contrast to the effective arylation of diarylsulfides and diphenylselenide, the conversion of diphenyltelluride is insufficiently slow.

A concise route to the 3-hydroxypyridine core of thiopeptide antibiotics such as nocathiacin is described. Key phases of the sequence involve a modified Hantzsch pyridine construction and a chemoselective Peng deprotection of a phenolic MOM ether.

[reaction: see text] We describe a convergent approach to soraphen A, 1, that involves coupling of two fragments by an aldol condensation-olefin metathesis sequence. This route permits rapid access to congeners of 1.