Design, synthesis and in vitro splicing inhibition of desmethyl and carba-derivatives of herboxidiene.

Herboxidiene is a potent inhibitor of spliceosomes. It exhibits excellent anticancer activity against multiple human cancer cell lines. Herein, we describe an enantioselective synthesis of a desmethyl derivative and the corresponding carba-derivatives of herboxidiene. The synthesis involved Suzuki coupling of a vinyl iodide with boronate as the key reaction. For the synthesis of carba-derivatives, the corresponding optically active cyclohexane-1,3-dicarbonyl derivatives were synthesized using an enantioselective desymmetrization of meso-anhydride. The biological properties of these derivatives were evaluated in an in vitro splicing assay.

Total synthesis of GEX1Q1, assignment of C-5 stereoconfiguration and evaluation of spliceosome inhibitory activity.

An enantioselective total synthesis of GEX1Q1 has been accomplished in a convergent manner. The C-5 asymmetric center has now been assigned through synthesis. GEX1Q1 displayed slightly better spliceosome inhibitory activity over its C-5 epimer. The salient features of this synthesis include an asymmetric hetero-Diels-Alder reaction to construct the tetrahydropyran ring and a Suzuki cross-coupling to assemble the key segments.

Coherence between cellular responses and in vitro splicing inhibition for the anti-tumor drug pladienolide B and its analogs.

Pladienolide B (PB) is a potent cancer cell growth inhibitor that targets the SF3B1 subunit of the spliceosome. There is considerable interest in the compound as a potential chemotherapeutic, as well as a tool to study SF3B1 function in splicing and cancer development. The molecular structure of PB, a bacterial natural product, contains a 12-member macrolide ring with an extended epoxide-containing side chain. Using a novel concise enantioselective synthesis, we created a series of PB structural analogs and the structurally related compound herboxidiene. We show that two methyl groups in the PB side chain, as well as a feature of the macrolide ring shared with herboxidiene, are required for splicing inhibition in vitro. Unexpectedly, we find that the epoxy group contributes only modestly to PB potency and is not absolutely necessary for activity. The orientations of at least two chiral centers off the macrolide ring have no effect on PB activity. Importantly, the ability of analogs to inhibit splicing in vitro directly correlated with their effects in a series of cellular assays. Those effects likely arise from inhibition of some, but not all, endogenous splicing events in cells, as previously reported for the structurally distinct SF3B1 inhibitor spliceostatin A. Together, our data support the idea that the impact of PB on cells is derived from its ability to impair the function of SF3B1 in splicing and also demonstrate that simplification of the PB scaffold is feasible.

Efficient systemic delivery of siRNA to the mouse liver by pegylated lipopolymer.

Short interfering RNA (siRNA) drugs have entered clinical trials in various disease areas. However, systemic use of siRNA drugs faces a challenge of tissue in-specificity and membrane impenetrability. In this study, we hypothesized that the combined of lipidic molecules with a pegylated cationic polymer through random polymerization of Micheal reaction could enhance the hepatocyte's preferential uptake and improve membrane penetrability. We reported the efficacy of in vitro knockdown of apoB mRNA in HepG2 cell line and in vivo knockdown of the liver apoB mRNA using a pegylated lipopolymer-siapoB complex. Results show that apoB mRNA in the nu/nu and C57BL/6 black mice was knockdown to ∼60-80%, up to 2 weeks, at low doses of 1.0-2.5 mg/kg of siRNA. The finding sets a new stage for further developments for apoB siRNA therapeutics.

Novel biodegradable lipid nano complex for siRNA delivery significantly improving the chemosensitivity of human colon cancer stem cells to paclitaxel.

BACKGROUND: Targeting of a specific subset of cells is mandatory for the successful application of siRNA mediated silencing in anticancer therapy. A recent theory suggests that colon cancer is sustained by a small subpopulation of cells, termed cancer stem cells (CSCs). These cells are characterized by their innate drug resistance properties, which is one of the key factors of chemotherapy failure. The goal of this study was to assess whether a novel siRNA delivery carrier, with an appropriate siRNA, targeted to CD133+ cells has the potential to improve the efficacy of conventional chemotherapy. METHODS: In this study, a novel synthetic siRNA carrier platform was designed and synthesized. This carrier was composed of a cationic oligomer (PEI(1200)), a hydrophilic polymer (polyethylene glycol) and a biodegradable lipid-based crosslinking moiety. Libraries of polymers were synthesized by varying their lipid composition. Their transfection efficacy was evaluated in vitro using CHOK1 cells. The polymer was characterized using molecular weight, particle encapsulation assay, particle size and surface charge analysis. RESULTS: It was demonstrated that the lipid composition in the polymer plays a critical role in transfection. Optimizing the physicochemical properties of the polymers is crucial in achieving favorable knockdown. Lipid nano complex with composition PEI-Lipid(1:16) was the optimum ratio for gene silencing. Additionally, silencing of multidrug resistance gene (MDR1) and treatment with paclitaxel play a synergistic role in increasing the efficacy as compared to the drug alone. CONCLUSIONS: In the present study a novel siRNA delivery carrier system with an MDR1-targeting siRNA (siMDR1) effectively reduced the expression of MDR1 in human colon CSCs (CD133+ enriched cell population), resulting in significantly increasing the chemosensitivity to paclitaxel.

Synthesis of the positron-emitting radiotracer [(18)F]-2-fluoro-2-deoxy-D-glucose from resin-bound perfluoroalkylsulfonates.

A new approach to the synthesis of 2-fluoro-2-deoxy-d-glucose (FDG, [(19/18)F]-) is described, which employs supported perfluoroalkylsulfonate precursors , where the support consists of insoluble polystyrene resin beads. Treatment of these resins with [(19)F]fluoride ion afforded protected FDG [(19)F]- as the major product, and the identities of the main byproducts were determined. Acidic removal of the acetal protecting groups from [(19)F]- was shown to produce [(19)F]FDG. The method has been applied to the efficient radiosynthesis of the imaging agent [(18)F]FDG, and was shown to produce the radiochemical tracer in good radiochemical yield (average 73%, decay corrected).

Study of the intramolecular cyclization of N-methyl-3-phenyl-N-(2-(E)-phenylethenyl)-trans(cis)-oxiranecarboxamide--syntheses of Homoclausenamide and Dehydroclausenamide.

Homoclausenamide was synthesized for the first time, and the intramolecular cyclization study of N-methyl-3-phenyl-N-(2-(E)-phenylethenyl)-trans(cis)-oxiranecarboxamide well demonstrated how the stereochemistry affects the cyclization paths.

An elegant synthesis of Zetaclausenamide.

Zetaclausenamide, which was isolated as a hepatoprotective agent from the leaves of medicinal plant Clausena lansium, was synthesized for the first time in six steps including Darzen's condensation, photoisomerization, and the final cyclization reactions.

Design and synthesis of simple macrocycles active against vancomycin-resistant enterococci (VRE).

16-membered meta,para-cyclophanes mimicking the vancomycin binding pocket (D-O-E ring) were designed and synthesized. The structural key features of these biaryl ether containing macrocycles are (1) the presence of beta-amino-alpha-hydroxy acid or alpha,beta-diamino acid as the C-terminal component of the cyclopeptide and (2) the presence of a hydrophobic chain or lipidated aminoglucose at the appropriate position. Cycloetherification by an intramolecular nucleophilic aromatic substitution reaction (S(N)Ar) is used as the key step for the construction of the macrocycle. The atropselectivity of this ring-closure reaction is found to be sensitive to the peptide backbone and chemoselective cyclization (phenol versus primary amine) is achievable. Glycosylation of phenol was realized with freshly prepared 3,4,6-tri-O-acetyl-2-N-lauroyl-2-amino-2-deoxy-alpha-D-glucopyranosyl bromide under phase-transfer conditions. Minimum inhibitory concentrations for all of the derivatives are measured by using a standard microdilution assay, and potent bioactivities against both sensitive and resistant strains are found for some of these compounds (MIC (minimum inhibitory concentration) = 4 microg mL(-1) against VRE). From these preliminary SAR studies, it was anticipated that both the presence of a hydrophobic substituent and an appropriate structure of the macrocycle were required for this series of compounds to be active against VRE.

An efficient approach to the asymmetric total synthesis of (-)-anisodine.

-Anisodine (l-6,7-epoxy-3-tropyl-alpha-hydroxytropate), which was isolated from the medicinal plant Scopolia tanguticus Maxim, was the first efficiently prepared using 6-beta-acetyltropine as the starting material via a key step of the Sharpless asymmetric dihydroxylation (AD). The intermediate compounds 10 and 11 showed promising cholinergic activity.

Identification of synthetic compounds active against VRE: the role of the lipidated aminoglucose and the structure of glycopeptide binding pocket.

A modified vancomycin binding pocket (D-O-E ring) incorporating an alpha-hydroxy-beta-amino acid at the AA4 position is designed and synthesized. Some of these compounds display potent bioactivities against both sensitive- and resistant-strains (8 microg/ml against VREF). Both the lipidated aminoglucose and the structure of the 16-membered macrocycle are found to be important for the anti-VRE activities. The polyamine appendage at the C-terminal, on the other hand, improved the activity against vancomycin-sensitive strains.

Synthesis of beta-amino-alpha-hydroxy esters and beta-amino-alpha-azido ester by Sharpless asymmetric aminohydroxylation, byproducts analysis.

[reaction: see text] Synthesis of enantiomerically pure beta-amino-alpha-hydroxy esters (1, 2) and beta-amino-alpha-azido ester (3) using Sharpless AA as a key step is described. A hitherto unreported side reaction, the oxidation of the beta-hydroxy-alpha-amino ester (5) into the alpha,alpha-di-tert-butyloxycarbamoyl-beta-ketoester (8) under AA conditions, is documented.

Design and synthesis of macrocycles active against vancomycin-resistant enterococci (VRE): the interplay between d-Ala-d-Lac binding and hydrophobic effect.

A modified vancomycin binding pocket (D-O-E ring) incorporating a CHNHCOR function at the AA4 position is designed and synthesized. Potent bioactivities against both sensitive- and resistant-strain are found for some of these compounds (MIC 4 microg/mL against VREF). From this preliminary SAR studies, it was speculated that the D-Ala-D-Ala binding was required for this series of compounds since the corresponding des-leucine derivative is inactive. The presence of long aliphatic chain was important for the desired activities and such hydrophobic effect is specific as no beneficial effect is observed when the same aliphatic chain was attached to the other part of the molecule.

Sulfoximine version of double elimination protocol for synthesis of chiral acetylenic cyclophanes.

A new strategy for constructing enantiopure acetylenic cyclophanes is described on the basis of one-pot double elimination reaction starting from dialdehydes and bis(sulfoximine)s. In this case, the conventional sulfone protocol affords poorer yields of the desired cyclophanes. Thus, arylene-ethynylene moieties with terminal sulfoximine or formyl functions are linked to binaphthyl cores and these building blocks are then subjected to double elimination reaction. The desired macrocycles are obtained in up to 35 % yield. The corresponding Sonogashira coupling fails to afford cyclophanes indicative of effectiveness of the double elimination methodology.