Sterically-Hindered Molecular p-Dopants Promote Integer Charge Transfer in Organic Semiconductors

Molecular p-dopants designed to undergo electron transfer with organic semiconductors are typically planar molecules with high electron affinity. However, their planarity can promote the formation of ground-state charge transfer complexes with the semiconductor host and results in fractional instead of integer charge transfer, which is highly detrimental to doping efficiency. Here, we show this process can be readily overcome by targeted dopant design exploiting steric hindrance. To this end, we synthesize and characterize the remarkably stable p-dopant 2,2',2''-(cyclopropane-1,2,3-triylidene)tris(2-(perfluorophenyl)acetonitrile) comprising pendant functional groups that sterically shield its central core while retaining high electron affinity. Finally, we demonstrate it outperforms a planar dopant of identical electron affinity and increases the thin film conductivity by up to an order of magnitude. We believe exploiting steric hindrance represents a promising design strategy towards molecular dopants of enhanced doping efficiency.

Diverse Applications of Biomass-Derived 5-Hydroxymethylfurfural and Derivatives as Renewable Starting Materials

This Review summarizes recent efforts to capitalize on 5-hydroxymethylfurfural (HMF) and related furans as emerging building blocks for the synthesis of fine chemicals and materials, with a focus on advanced applications within medicinal and polymer chemistry, as well as nanomaterials. As with all chemical industries, these fields have historically relied heavily on petroleum-derived starting materials, an unsustainable and polluting feedstock. Encouragingly, the emergent chemical versatility of biomass-derived furans has been shown to facilitate derivatization towards valuable targets. Continued work on the synthetic manipulation of HMF, and related derivatives, for access to a wide range of target compounds and materials is crucial for further development. Increasingly, biomass-derived furans are being utilized for a wide range of chemical applications, the continuation of which is paramount to accelerate the paradigm shift towards a sustainable chemical industry.

Solvent-free synthesis of 3,5-isoxazoles via 1,3-dipolar cycloaddition of terminal alkynes and hydroxyimidoyl chlorides over Cu/Al2O3 surface under ball-milling conditions

Scalable, solvent-free synthesis of 3,5-isoxazoles under ball-milling conditions has been developed. The proposed methodology allows the synthesis of 3,5-isoxazoles in moderate to excellent yields from terminal alkynes and hydroxyimidoyl chlorides, using a recyclable Cu/Al₂O₃ nanocomposite catalyst. Furthermore, the proposed conditions are reproducible to a 1.0-gram scale without further milling time variations.

A practical and scalable mechanochemical 1,3-dipolar cycloaddition between hydroxyimidoyl chlorides and terminal alkynes catalyzed by Cu/Al₂O₃ allows a quick access to 3,5-isoxazole derivatives.

Characterization of a recently synthesized microtubule-targeting compound that disrupts mitotic spindle poles in human cells

We reveal the effects of a new microtubule-destabilizing compound in human cells. C75 has a core thienoisoquinoline scaffold with several functional groups amenable to modification. Previously we found that sub micromolar concentrations of C75 caused cytotoxicity. We also found that C75 inhibited microtubule polymerization and competed with colchicine for tubulin-binding in vitro. However, here we found that the two compounds synergized suggesting differences in their mechanism of action. Indeed, live imaging revealed that C75 causes different spindle phenotypes compared to colchicine. Spindles remained bipolar and collapsed after colchicine treatment, while C75 caused bipolar spindles to become multipolar. Importantly, microtubules rapidly disappeared after C75-treatment, but then grew back unevenly and from multiple poles. The C75 spindle phenotype is reminiscent of phenotypes caused by depletion of ch-TOG, a microtubule polymerase, suggesting that C75 blocks microtubule polymerization in metaphase cells. C75 also caused an increase in the number of spindle poles in paclitaxel-treated cells, and combining low amounts of C75 and paclitaxel caused greater regression of multicellular tumour spheroids compared to each compound on their own. These findings warrant further exploration of C75’s anti-cancer potential.

Design, structure-activity relationship study and biological evaluation of the thieno[3,2-c]isoquinoline scaffold as a potential anti-cancer agent

Several derivatives of a series that share a thienoisoquinoline scaffold have demonstrated potent activity against cancer cell lines A549, HeLa, HCT-116, and MDA-MB-231 in the submicromolar concentration range. Structure-activity relationship (SAR) studies on a range of derivatives aided in identifying key pharmacophores in the lead compound. A series of compounds have been identified as the most promising with submicromolar IC₅₀ values against a lung cancer cell line (A549). Microscopy studies of cancer cells treated with the lead compound revealed that it causes mitotic arrest and disrupts microtubules. Further evaluation via an in vitro microtubule polymerization assay and competition studies indicate that the lead compound binds to tubulin via the colchicine site.

Programmed Synthesis of Tetra-Aryl Thiophenes with Stepwise, Ester-Controlled Regioselectivity

Herein, we report a modular synthetic route to access tetra-arylated thiophene compounds with four different substituents with programmed chemical control provided by an ester activating/directing group. This method enables the functionalization of individual positions of thiophene sequentially via regioselective halogenations and cross-coupling reactions. The reaction sequence described provides tetra-arylated thiophenes in higher yields than previous routes and employs practical reaction protocols, simple catalytic systems, and short reaction times.

Synthesis of 2,5-Diaryl Nonsymmetric Furans C6-Platform Chemicals via Catalytic Conversion of Biomass and the Formal Synthesis of Dantrolene

Biomass-derived commodity chemical 5-hydroxymethyl furfural is an underutilized C6-platform chemical derived from cellulose that is ideal to prepare next-generation value-added products. We have developed an efficient synthetic strategy to access 2,5-diaryl nonsymmetric furans from 5-hydroxymethyl furfural utilizing decarboxylative cross-couplings. A key finding was that the presence of the hydroxymethyl handle enhances the yields of the palladium-catalyzed decarboxylative cross-coupling reaction. The method provides access to a broad-range nonsymmetric 2,5-diaryl furans where each arene can be systematically introduced as required. Additionally, this green synthetic strategy was employed for a formal synthesis of the muscle relaxant Dantrolene in excellent yields.

Microwave-assisted Synthesis and Docking Studies of Phenylureas as Candidates for the Drug Design Against the Biological Warfare Agent Yersinia Pestis

Background:

Bubonic plague is amongst the diseases with the highest potential for being used in biological warfare attacks today. This disease, caused by the bacterium Yersina pestis, is highly infectious and can achieve 100% of fatal victims when in its most dangerous form. Besides, there is no effective vaccine, and the chemotherapy available today against plague is ineffective if not administered at the beginning of the infection.

Objective:

Willing to contribute for changing this reality we propose here new phenylureas as candidates for the drug design against plague meant to target the enzyme dihydrofolate reductase from Y. pestis (YpDHFR).

Methods:

Seven phenylureas, four of them new, were synthesized, following synthetic routes adapted from procedures available in the literature, and using microwave irradiation. After, they were submitted to docking studies inside YpDHFR and human DHFR (HssDHFR) in order to check their potential as selective inhibitors.

Results:

Our results revealed four new phenylureas and a new synthetic route for this kind of molecule using microwave irradiation. Also, our docking studies showed that these compounds are capable of binding to both HssDHFR and YpDHFR, with U1 - U4 and U23 showing more selectivity for HssDHFR and U7, U8 being more selective towards YpDHFR.

Conclusion:

We reported the synthesis with good yields of seven phenylureas, following a simple and clean alternative synthetic route using microwave irradiation. Further molecular docking studies of our compounds suggested that two are capable of binding more selectivity to YpDHFR, qualifying as potential candidates for the drug design of new drugs against plague.

Approaching the Integer-Charge Transfer Regime in Molecularly Doped Oligothiophenes by Efficient Decarboxylative Cross-Coupling

A library of symmetrical linear oligothiophene was prepared employing decarboxylative cross-coupling reaction as the key transformation. Thiophene potassium carboxylate salts were used as cross-coupling partners without the need of co-catalyst, base, or additives. This method demonstrates complete chemoselectivity and is a comprehensive greener approach compared to the existing methods. The modularity of this approach is demonstrated with the preparation of discreet oligothiophenes with up to 10 thiophene repeat units. Symmetrical oligothiophenes are prototypical organic semiconductors where their molecular electrical doping as a function of the chain length can be assessed spectroscopically. An oligothiophene critical length for integer charge transfer was observed to be 10 thiophene units, highlighting the potential use of discrete oligothiophenes as doped conduction or injection layers in organic electronics applications.

Facile Aqueous-Phase Synthesis of an Ultrasmall Bismuth Nanocatalyst for the Reduction of 4-Nitrophenol

Bismuth metallic nanoparticles have evoked considerable interest in catalysis owing to their small size, high surface area-to-volume ratio, and low toxicity. However, the need for toxic reductants and organic solvents in their synthesis often limits their desirability for application development. Here, we describe a green strategy to synthesize bismuth nanodots via the redox reactions between bismuth nitrate and d-glucose, in the presence of poly(vinylpyrrolidone) in the basic aqueous phase. Both reagents play a crucial role in the formation of monodisperse bismuth nanodots acting as mild reducing and capping agents, respectively. We further demonstrate that the catalytic activity of these dots via the successful reduction of the environmental contaminant 4-nitrophenol to its useful 4-aminophenol analogue requiring only 36 μg/mL nanocatalyst for 20 mM of the substrate. Moreover, they can be recovered and recycled in multiple reactions before the onset of an appreciable loss of catalytic activity. The proposed facile synthetic route and inexpensive matrix materials lead the way to access bismuth nanodots for both the fundamental study of reactions and their industrial catalysis applications.

A High-Throughput Glycosyltransferase Inhibition Assay for Identifying Molecules Targeting Fucosylation in Cancer Cell-Surface Modification

In cancers, increased fucosylation (attachment of fucose sugar residues) on cell-surface glycans, resulting from the abnormal upregulation of the expression of specific fucosyltransferase enzymes (FUTs), is one of the most important types of glycan modifications associated with malignancy. Fucosylated glycans on cell surfaces are involved in a multitude of cellular interactions and signal regulation in normal biological processes, as well as in disease. For example, sialyl Lewis^X is a fucosylated cell-surface glycan that is abnormally abundant in some cancers where it has been implicated in facilitating metastasis, allowing circulating tumor cells to bind to the epithelial tissue within blood vessels and invade into secondary sites by taking advantage of glycan-mediated interactions. To identify inhibitors of FUT enzymes as potential cancer therapeutics, we have developed a novel high-throughput assay that makes use of a fluorogenically labeled oligosaccharide as a probe of fucosylation. This probe, which consists of a 4-methylumbelliferyl glycoside, is recognized and hydrolyzed by specific glycoside hydrolase enzymes to release fluorescent 4-methylumbelliferone, yet when the probe is fucosylated prior to treatment with the glycoside hydrolases, hydrolysis does not occur and no fluorescent signal is produced. We have demonstrated that this assay can be used to measure the inhibition of FUT enzymes by small molecules, because blocking fucosylation will allow glycosidase-catalyzed hydrolysis of the labeled oligosaccharide to produce a fluorescent signal. Employing this assay, we have screened a focused library of small molecules for inhibitors of a human FUT enzyme involved in the synthesis of sialyl Lewis^X and demonstrated that our approach can be used to identify potent FUT inhibitors from compound libraries in microtiter plate format.

Convenient and Inexpensive Route to Sulfonylated Pyridines via SNAr Reaction of Electron-Rich Pyridines by Iron Catalysis

Sulfonylated pyridines were synthesized in moderate to excellent yields, with a wide scope of substituted pyridines and sulfinate salts as starting materials, by an iron-catalyzed SNAr reaction. This new methodology exhibits advantages for the synthesis of these useful substrates, such as the use of a readily available, inexpensive catalyst, prevention of the disproportionation of the sulfinate salts, and, more importantly, providing access to electron-rich pyridine substrates.

Abstract 3247: Discovery of a novel drug that affects centrosome clustering

Our goal is to identify molecular regulators of a mechanism that occurs uniquely in cancer cells, and to develop a selective anti-cancer drug. Most chemotherapies are non-selective, causing severe side-effects. In additions, cancers often develop resistance to some of the more commonly used chemotherapies. To expand the repertoire of available drugs, and to design drugs that are selective, we need to identify molecules that regulate the physiological changes that occur primarily in cancer cells. For example, cancer cells in many hard-to-treat cancers have aberrant centrosomes, which may be supernumerary or fragmented. During mitosis, these aberrant centrosomes must cluster to form bipolar spindles for successful division. Thus, targeting a process like centrosome clustering is ideal, since it is not necessary in healthy cells. We synthesized a small, stable scaffold with amenability to structure-activity-relationship studies, and found several analogues with IC50 values < 50 nM, depending on the cancer cell line. Preliminary tests showed that these compounds prevent tumors from forming and/or cause their regression in vitro. We performed cell biological studies to characterize their mechanism of action. In several different types of cancer cells, these compounds cause mitotic arrest and centrosome declustering at concentrations where they have little affect on non-cancerous cells. Live imaging revealed that within minutes of adding the compounds to HeLa cells expressing GFP-tagged tubulin, we observed rapid microtubule depolymerization and centrosome declustering. After washing out the compound, microtubule polymerization recovered, but the mitotic spindles were multipolar. Adding similar concentrations of Nocodazole, a microtubule-depolymerizing drug, also caused rapid microtubule depolymerization, but after washing out the drug, the spindles were bipolar. We are in the process of identifying the molecular target of these compounds to provide crucial insight to the mechanism governing centrosome clustering, and are continuing to perform SAR studies to obtain compounds with higher efficacy and selectivity.

Citation Format: Dilan B. Jaunky, Kevin Larocque, Javier Porro Suardiaz, Dan Yang, Emma J. Furze, Pat Forgione, Alisa Piekny. Discovery of a novel drug that affects centrosome clustering [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3247. doi:10.1158/1538-7445.AM2017-3247

Spruce budworm feeding and oviposition are stimulated by monoterpenes in white spruce epicuticular waxes

Monoterpenes, source of the distinctive odor of conifers, are generally considered plant defensive compounds. However, they are also known to act as long-range insect attractants, as they are volatile and permeate forest airspaces. Moreover, they are lipid soluble and can be absorbed into plant epicuticular waxes. We test their role in short-range host plant choice by both adult females and larvae of a folivorous forest pest (Choristoneura fumiferana). We conducted laboratory assays testing the responses of Eastern spruce budworm to an artificial monoterpene mix (α-pinene, β-pinene, limonene, myrcene) and to white spruce (Picea glauca) epicuticular waxes in closed arenas. Ovipositing females preferred filter paper discs treated with P. glauca waxes to controls, and preferred the waxes + monoterpenes treatment to waxes alone. However, females showed no preference between the monoterpene-treated disc and the control when presented without waxes. Feeding larvae prefered wax discs to control discs. They also consumed discs treated with realistic monoterpene concentrations and wax preferentially over wax-only discs, but showed no preference between extremely high monoterpene concentrations and wax-only controls. In an insect-free assay, P. glauca epicuticular wax decreased monoterpene volatilization. These results suggest that P. glauca waxes and realistic concentrations of monoterpenes are stimulatory to both egg-laying females and feeding larvae, and that their effects are synergistic.

Analysis of Coxiela burnetti dihydrofolate reductase via in silico docking with inhibitors and molecular dynamics simulation

Coxiella burnetii is a gram-negative bacterium able to infect several eukaryotic cells, mainly monocytes and macrophages. It is found widely in nature with ticks, birds, and mammals as major hosts. C. burnetii is also the biological warfare agent that causes Q fever, a disease that has no vaccine or proven chemotherapy available. Considering the current geopolitical context, this fact reinforces the need for discovering new treatments and molecular targets for drug design against C. burnetii. Among the main molecular targets against bacterial diseases reported, the enzyme dihydrofolate reductase (DHFR) has been investigated for several infectious diseases. In the present work, we applied molecular modeling techniques to evaluate the interactions of known DHFR inhibitors in the active sites of human and C. burnetii DHFR (HssDHFR and CbDHFR) in order to investigate their potential as selective inhibitors of CbDHFR. Results showed that most of the ligands studied compete for the binding site of the substrate more effectively than the reference drug trimethoprim. Also the most promising compounds were proposed as leads for the drug design of potential CbDHFR inhibitors.

Abstract 3808: Novel compound conferring selectivity for cancer cells

There is a need to develop novel compounds that can effectively treat a broad range of cancers on their own, or in combination with approved therapies. As personalized medicine is developed, combinatorial approaches will become more common making it crucial to increase the repertoire of available drugs. In the past, drugs often were developed to target a biologically-relevant molecule, but structural limitations, stability and solubility issues, or lack of selectivity have hindered the clinical use of many of these drugs. Our approach was to first find a ‘high-quality’ compound that is selective for cancer cells, then characterize its mechanism of action and identify its target. High throughput screening (HTS) helped to rapidly identify a subset of compounds with selective toxicity toward MCF-7 (breast cancer) cells. Some of these compounds were further tested for their efficacy in HeLa (cervical cancer) cells, and we found one that selectively causes mitotic arrest at 250 nM in comparison to non-cancerous HFF-1 (foreskin fibroblast) cells. At 200 nM, this compound synergizes with drugs known to affect microtubule dynamics and cause mitotic arrest including Nocodazole and Paclitaxel (currently in use as an anti-cancer drug), causing them to be more effective at lower concentrations. Excitingly, this compound also provides a shielding effect for HFF-1 cells treated with Paclitaxel. To learn the mechanism of action for this compound, we performed immunofluorescence microscopy on HeLa and HFF-1 cells treated with a range of concentrations. We found that the mitotic spindle is improperly organized in HeLa cells at 250 nM, but not in HFF-1 cells. Interestingly, microtubules are completely gone in mitotic HeLa cells and are reduced in mitotic HFF-1 cells treated with >500 nM. Given that this compound synergizes with drugs that directly bind to tubulin subunits to modify their dynamics of assembly and disassembly, and differently affects cancerous vs. healthy cells, we hypothesize that it has a unique mechanism of action and may affect microtubule nucleation. We are continuing to characterize the compound, and will identify its molecular target. In addition, we are generating further iterations to explore the Structure-Activity Relationship, and optimize its efficacy. Our in vitro data shows that our approach has the potential to identify novel compounds with the potential for therapeutic use.

Citation Format: Dilan B. Jaunky, Pat Forgione, Alisa Piekny. Novel compound conferring selectivity for cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3808.

Synthesis of 2,5-diaryl-substituted thiophenes as helical mimetics: towards the modulation of islet amyloid polypeptide (IAPP) amyloid fibril formation and cytotoxicity

A range of 2,5-diarylated thiophenes were synthesised as small molecule mimetics of the α-helix to modulate the amyloidogenesis and cytotoxic effect of islet amyloid polypeptide (IAPP). 3-Substituted thiophene-2-carboxylic acids were used as key intermediates and functionalised by palladium decarboxylative cross-coupling and direct C-H activation successively with overall yields ranging from 23 to 95 %. The effect of the ligands on IAPP amyloid fibril formation was evaluated with the thioflavin T (ThT) fluorescence-based assay. Furthermore, the capacity of these compounds to inhibit the cytotoxic effect of IAPP was assessed using β-pancreatic cells.

Palladium-catalyzed intermolecular desulfinylative cross-coupling of heteroaromatic sulfinates

Beauty lies in simplicity: An efficient and environmentally benign palladium-catalyzed protocol has been developed using a sulfinate as a nucleophilic coupling partner. The sulfinate position is arylated chemoselectively in very good yields. The bench-stable, non-hygroscopic heteroaromatic sulfinate salts rapidly undergo cross-coupling without the need of a co-catalyst, base, or additives (see scheme; mw = microwave).

Combined directed ortho and remote metalation-Suzuki cross-coupling strategies. Efficient synthesis of heteroaryl-fused benzopyranones from biaryl O-carbamates

A concise synthesis of heteroaryl dibenzopyranones 9a,b, 10a,b, 11a-c, and 12a-c has been achieved by the LDA-induced migration of heterobiaryl O-carbamates 18, 21, 25, and 30 which, in turn, were prepared in good yield using a combined directed ortho lithiation (DoM)-transition-metal-catalyzed Suzuki cross-coupling strategy. An efficient and general route to a wide variety of heterocycles including coumestans 19a,c and the previously unknown isothiocoumestan ring system 22b has been thereby achieved.

A modular approach to marine macrolide construction. 4. Assembly of C36-C51 and C29-C44 building blocks and evaluation of key coupling reactions targeting spongistatin 1 (altohyrtin A)

Routes have been developed for the stereocontrolled elaboration of two highly functionalized sectors of spongistatin 1. The approach to ring F takes advantage of B-alkyl Suzuki-Miyaura coupling to install the C44-C45 bond. The E-ring pyran moiety was generated by acylation of an alpha-sulfonyl carbanion, the stereogenic centers of which were incorporated by sequential asymmetric aldol reactions. [structure: see text].

Unexpected Intermolecular Pd-Catalyzed Cross-Coupling Reaction Employing Heteroaromatic Carboxylic Acids as Coupling Partners

Aryl-substituted five-membered heteroaromatics have attracted great interest over the past years due to their presence in a large number of pharmaceuticals and natural products. Recently, an advance in the preparation of these scaffolds was achieved by employing a C-H functionalization strategy. This method allows easy access to these biaryl motifs by precluding the necessity of preparing specific coupling partners, although poor regioselectivity is sometimes observed when more than one reactive C-H is present on the substrate. In an effort to circumvent this liability, we envisioned the use of a carboxylic acid moiety as a blocking group that could be later functionalized or removed. Remarkably, the coupling was found to occur exclusively at the position previously occupied by the acid, even in the presence of a reactive C-H group. This selective transformation was also found to proceed with other heteroaromatic carboxylic acids, allowing for the preparation of a variety of aryl-substituted heteroaromatics that would be difficult to obtain via other methods.

Part 1: Efficient strategies for the construction of variably substituted bicyclo[5.3.1]undecenones (AB taxane ring systems)

Strategies for the construction of cyclic molecules containing variably substituted bicyclo[5.3.1]undecenones (AB taxane ring systems) are described. These routes employ a multi-component coupling protocol that utilizes sequential magnesium-mediated carbometallation of propargyl alcohols and intramolecular Diels–Alder reactions (IMDA). The cycloaddition generates the key eight-membered taxane ring as a single diastereomer, induced by preferential Lewis acid (diethylaluminum chloride or boron trifluoride etherate) complexation with the cross-ring oxygens. Both the electronic nature of the dienophile and the neighbouring group non-bonded interactions contribute to the success of these cycloadditions.Key words: magnesium chelate, Lewis acid, intramolecular Diels–Alder, cycloaddition.

[Scrofuloderma. a clinical case]

Scrofuloderma is a form of colliquative cutaneous tuberculosis resulting from the spread of an underlying focus, generally represented by lymphnodes; osteoarticular tubercular locations or epididimus locations can also lead to ulcerative cutaneous involvement. We report the case of a female patient aged 12 who had been in Italy for 15 days following her arrival from Marocco. In the left clavicular region she presented an ulcerated lesion with palpable lymphnodes on the corresponding side of the neck. Histopathological examination of one of the involved lymphnodes suggested a mycobacteriosis; differential diagnosis was carried out between MAIS (M. avium, M. intracellulare, M. scrofulaceum) group mycobacteria infection and tuberculosis. Bacteriological research in the lymphnode of alcohol-acid resistant bacilli gave a negative result, while cultural examination and protein chain reaction pointed to M. tuberculosis. The patient was subjected to combined treatment based on rifampycin, isoniazide, etambutolol and pyrazinamide. At the present time, tuberculosis is an important public health problem in developing countries. In western countries such as the United Kingdom, which have been open to immigration for a longer time, scrofuloderma is present with higher prevalence in immigrants from Asia and Africa; in these immigrant populations, this tubercular form involves a wide age segment between the ages of 10 and 50. In the autochthonous population the highest incidence is in subjects aged more than 50. In Italy too, extra-communitary immigration has also contributed, with a delay compared to other western countries, to bring tuberculosis back into the public eye after a period of decades during which it was wrongly considered to have disappeared.

Tether-controlled cycloadditions for the asymmetric synthesis of decalins: increased selectivity in acetonitrile solvent

[reaction: see text] The beneficial influence of cis-isopropylidene acetal tether control groups, to facilitate the asymmetric synthesis of substituted decalins by intramolecular Diels-Alder reactions, is described. Compared to trans-acetonides, these cases proceed under milder conditions to afford the cis-fused adducts from an endo transition state. An unusual acetonitrile solvent effect exerts a dramatic influence on the diastereoselectivity. This strategy leads to the chiral nonracemic bicyclo[4.4.0]decane core of diverse natural products.