Name: synthesis and evaluation of a ruthenium-based mitochondrial calcium uptake inhibitor
Uploaded: 2017-10-26T15:00:00
Description: Watch this Scientific Journal Video about Synthesis and Evaluation of a Ruthenium-based Mitochondrial Calcium Uptake Inhibitor at JoVE.com

This research was supported by Cornell University. This work made use of the Cornell Center for Materials Research Shared Facilities, which are supported through the NSF MRSEC program (Grant DMR-1120296). S.R.N. acknowledges support by an NSF Graduate Research Fellowship (Grant DGE- 1650441) and Dr. Dave Holowka for assistance with the calcium experiments. Any opinion, findings, and conclusions or recommendations expressed in this material are those of the authors(s) and do not necessarily reflect the views of the National Science Foundation.

NOTE: Concentrated acids and bases are used in this synthesis. Use all appropriate safety practices when performing the reaction including the use of engineering controls (fume hood) and personal protective equipment (PPE) including safety glasses, gloves, lab coat, full length pants, and closed-toe shoes.
1. Preparation of [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]Cl5
<ol>
	<li>Synthesis of [Ru(NH3)5Cl]Cl...

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M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Integrative+genomics+identifies+MCU+as+an+essential+component+of+the+mitochondrial+calcium+uniporter.">Integrative genomics identifies MCU as an essential component of the mitochondrial calcium uniporter.</a> Nature. 476 (7360), 341-356 (2011).</li><li>Kamer, K. J., Mootha, V. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+molecular+era+of+the+mitochondrial+calcium+uniporter.">The molecular era of the mitochondrial calcium uniporter.</a> Nat. Rev. Mol. Cell Biol. 16 (9), 545-553 (2015).</li><li>Ying, W. -. L., Emerson, J., Clarke, M. J., Sanadi, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inhibition+of+mitochondrial+calcium+ion+transport+by+an+oxo-bridged+dinuclear+ruthenium+ammine+complex.">Inhibition of mitochondrial calcium ion transport by an oxo-bridged dinuclear ruthenium ammine complex.</a> Biochemistry. 30 (20), 4949-4952 (1991).</li><li>Emerson, J., Clarke, M. J., Ying, W. -. L., Sanadi, D. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+component+of+"ruthenium+red"+responsible+for+inhibition+of+mitochondrial+calcium+ion+transport.+Spectra,+electrochemistry,+and+aquation+kinetics.+Crystal+structure+of+&#181;-O-[(HCO2)(NH3)4Ru]2Cl3.">The component of "ruthenium red" responsible for inhibition of mitochondrial calcium ion transport. Spectra, electrochemistry, and aquation kinetics. 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The mitochondrial calcium uptake inhibitor [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]Cl5 can be synthesized from [Ru(NH3)5Cl]Cl2, a well known ruthenium(III) starting material, as described in this procedure. The synthesis of [Ru(NH3)5Cl]Cl2 is readily achieved with little difficulty. After stirring RuCl3 for 16 h in hydrazine hydrate, the pH of the solution should be adjus...

Mitochondrial calcium is a key regulator for a number of processes that are critical to normal cell function, including energy production and apoptosis.1,2,3 The mitochondrial calcium uniporter (MCU), an ion transporter protein that resides on the inner mitochondrial membrane, regulates the influx of calcium ions into the mitochondria.4,5,6 Chemical inhibitors of the MCU are valuable tools for continuing efforts to study the function and cellular roles of this transport protein and mitochondrial calcium. The compound [(HCO2)(NH3)4Ru(&#181;-O)Ru(NH3)4(O2CH)]3+, Ru360, is one of the only known selective inhibitors for the MCU with a reported Kd value of 24 &#181;M.7,8,9,10 This complex is a common impurity found in commercial formulations of ruthenium red (RuRed), a triruthenium di-&#181;-oxo bridged hexacation of the formula [(NH3)5Ru(&#181;-O)Ru(NH3)4(&#181;-O)Ru(NH3)5)]6+, which has also been used as a calcium uptake inhibitor. Although Ru360 is commercially available, it is very costly. Moreover, the synthesis and isolation of Ru360 is challenged by difficult purification procedures and ambiguous characterization methods.
We have recently reported alternative procedures to access a Ru360 analogue, [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]Cl5.11 This compound inhibits the MCU with high affinity, similar to Ru360. In this protocol, we will describe our most effective synthesis of this compound, which commences from [Ru(NH3)5Cl]Cl2. Purification of the product using strongly acidic cation-exchange resin is detailed, along with common pitfalls for this procedure. We also present methods for characterization and assessment of compound purity, and delineate a simple approach to test its efficacy in blocking mitochondrial calcium uptake.

<table style="border-collapse:collapse;width:663pt" width="884">
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	<tbody>
		<tr height="23" style="height:17.25pt">
			<td class="xl69" height="23" style="width:182pt;height:17.25pt" width="243">Ruthenium Trichloride hydrate</td>
			<td class="xl69" style="width:227pt" width="302">Pressure Chemical</td>
			<td class="xl69" style="width:129pt" width="172">3750</td>
			<td class="xl70" style="width:125pt" width="167"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">Concentrated hydrochloric acid</td>
			<td class="xl69" style="width:227pt" width="302">J.T. Baker</td>
			<td class="xl69" style="width:129pt" width="172">9535</td>
			<td class="xl70"></td>
		</tr>
		<tr height="22" style="height:16.5pt">
			<td class="xl69" height="22" style="width:182pt;height:16.5pt" width="243">Concentrated ammonium hydroxide</td>
			<td class="xl71" style="width:227pt" width="302">Mallinckrodt Chemical Works</td>
			<td class="xl71" style="width:129pt" width="172">A669C-2 1</td>
			<td class="xl70"></td>
		</tr>
		<tr height="24" style="height:18.0pt">
			<td class="xl69" height="24" style="width:182pt;height:18.0pt" width="243">Dowex 50 WX2 200-400 Mesh</td>
			<td class="xl69" style="width:227pt" width="302">Alfa Aesar</td>
			<td class="xl69" style="width:129pt" width="172">13945</td>
			<td class="xl70"></td>
		</tr>
		<tr height="25" style="height:18.75pt">
			<td class="xl69" height="25" style="width:182pt;height:18.75pt" width="243">Calcium Green 5N</td>
			<td class="xl69" style="width:227pt" width="302">Invitrogen</td>
			<td class="xl69" style="width:129pt" width="172">C3737</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">Digitonin</td>
			<td class="xl69" style="width:227pt" width="302">Aldrich</td>
			<td class="xl71" style="width:129pt" width="172">260746</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">DMSO</td>
			<td class="xl69" style="width:227pt" width="302">Aldrich</td>
			<td class="xl69" style="width:129pt" width="172">471267</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">EGTA</td>
			<td class="xl69" style="width:227pt" width="302">Aldrich</td>
			<td class="xl69" style="width:129pt" width="172">E3889</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">KCl</td>
			<td class="xl69" style="width:227pt" width="302">USB</td>
			<td class="xl69" style="width:129pt" width="172">20598</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">KH2PO4</td>
			<td class="xl69" style="width:227pt" width="302">Aldrich</td>
			<td class="xl69" style="width:129pt" width="172">P3786</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">MgCl2</td>
			<td class="xl77" style="width:227pt" width="302">Fisher Scientific</td>
			<td class="xl69" style="width:129pt" width="172">M33-500</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">HEPES</td>
			<td class="xl69" style="width:227pt" width="302">Fluka</td>
			<td class="xl69" style="width:129pt" width="172">54466</td>
			<td class="xl70"></td>
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		<tr height="22" style="height:16.5pt">
			<td class="xl69" height="22" style="width:182pt;height:16.5pt" width="243">Sodium Succinate</td>
			<td class="xl69" style="width:227pt" width="302">Alfa Aesar</td>
			<td class="xl69" style="width:129pt" width="172">33386</td>
			<td class="xl70"></td>
		</tr>
		<tr height="22" style="height:16.5pt">
			<td class="xl69" height="22" style="width:182pt;height:16.5pt" width="243">EDTA</td>
			<td class="xl69" style="width:227pt" width="302">J.T. Baker</td>
			<td class="xl69" style="width:129pt" width="172">8993-01</td>
			<td class="xl70"></td>
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		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">Glucose</td>
			<td class="xl69" style="width:227pt" width="302">Aldrich</td>
			<td class="xl69" style="width:129pt" width="172">G5000</td>
			<td class="xl70"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl69" height="21" style="width:182pt;height:15.75pt" width="243">200 Round bottom flask</td>
			<td class="xl69" style="width:227pt" width="302">ChemGlass</td>
			<td class="xl75">CG-1506-14</td>
			<td class="xl74" style="width:125pt" width="167"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">Glass stopper</td>
			<td class="xl65" style="width:227pt" width="302">ChemGlass</td>
			<td class="xl65" style="width:129pt" width="172">CG-3000-05</td>
			<td class="xl68"></td>
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		<tr height="42" style="height:31.5pt">
			<td class="xl65" height="42" style="width:182pt;height:31.5pt" width="243">10 mm x 15 cm glass column with reservoirs</td>
			<td class="xl77" style="width:227pt" width="302">Custom - similar to Chemglass columns</td>
			<td class="xl77" style="width:129pt" width="172">Similar to CG-1203-20</td>
			<td class="xl68"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl65" height="20" style="width:182pt;height:15.0pt" width="243">DMEM</td>
			<td class="xl77" style="width:227pt" width="302">Corning</td>
			<td class="xl77" style="width:129pt" width="172">10-017-CV</td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">FBS</td>
			<td class="xl77" style="width:227pt" width="302">Gibco</td>
			<td class="xl69" style="width:129pt" width="172">10437028</td>
			<td class="xl68"></td>
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		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">PBS</td>
			<td class="xl77" style="width:227pt" width="302">Corning</td>
			<td class="xl69" style="width:129pt" width="172">21-040-CV</td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">Round bottom Falcon tubes</td>
			<td class="xl77" style="width:227pt" width="302">Fisher Scientific</td>
			<td class="xl69" style="width:129pt" width="172">14-959-11B&#160;</td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">500 cm2 petri dishes</td>
			<td class="xl65" style="width:227pt" width="302">Corning</td>
			<td class="xl76" style="width:129pt" width="172">431110</td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">Trypan blue</td>
			<td class="xl65" style="width:227pt" width="302">ThermoFisher Scientific</td>
			<td class="xl76" style="width:129pt" width="172">15250061</td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">Hemacytometer</td>
			<td class="xl65" style="width:227pt" width="302">Aldrich</td>
			<td class="xl76" style="width:129pt" width="172">Z359629</td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">Acrylic Cuvettes</td>
			<td class="xl65" style="width:227pt" width="302">VWR&#160;</td>
			<td class="xl76" style="width:129pt" width="172">58017-875</td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl72" height="21" style="width:182pt;height:15.75pt" width="243">UV-Vis spectrometer</td>
			<td class="xl68">Agilent Model Cary 8454&#160;</td>
			<td class="xl65" style="width:129pt" width="172"></td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl72" height="21" style="width:182pt;height:15.75pt" width="243">Spectrofluorimeter</td>
			<td class="xl68">SLM Model 8100C</td>
			<td class="xl65" style="width:129pt" width="172"></td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl72" height="21" style="width:182pt;height:15.75pt" width="243">IR spectrometer</td>
			<td class="xl68">Bruker Hyprion FTIR with ATR attachment</td>
			<td class="xl65" style="width:129pt" width="172"></td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">Centrifuge</td>
			<td class="xl65" style="width:227pt" width="302">ALC Model PM140R</td>
			<td class="xl65" style="width:129pt" width="172"></td>
			<td class="xl68"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl65" height="21" style="width:182pt;height:15.75pt" width="243">Inverted light microscope</td>
			<td class="xl65" style="width:227pt" width="302">VWR&#160;</td>
			<td class="xl65" style="width:129pt" width="172">89404-462</td>
			<td class="xl68"></td>
		</tr>
	</tbody>
</table>

synthesis and evaluation of a ruthenium-based mitochondrial calcium uptake inhibitor

We detail the synthesis and purification of a mitochondrial calcium uptake inhibitor, [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]5+. The optimized synthesis of this compound commences from [Ru(NH3)5Cl]Cl2 in 1 M NH4OH in a closed container, yielding a green solution. Purification is accomplished with cation-exchange chromatography. This compound is characterized and verified to be pure by UV-vis and IR spectroscopy. The mitochondrial calcium uptake inhibitory properties are assessed in permeabilized HeLa cells by fluorescence spectroscopy.

This method describes a synthesis of the mitochondrial calcium uptake inhibitor [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]Cl5 starting from [Ru(NH3)5Cl]Cl2, a well known ruthenium(III) starting material. [Ru(NH3)5Cl]Cl2 is characterized by IR spectroscopy, with vibrational modes at 3200 cm-1, 1608 cm-1, 1298 cm-1, and 7...

Watch this Scientific Journal Video about Synthesis and Evaluation of a Ruthenium-based Mitochondrial Calcium Uptake Inhibitor at JoVE.com

Synthesis and Evaluation of a Ruthenium-based Mitochondrial Calcium Uptake Inhibitor

A protocol for the synthesis, purification, and characterization of a ruthenium-based inhibitor of mitochondrial calcium uptake is presented. A procedure to evaluate its efficacy in permeabilized mammalian cells is demonstrated.

We detail the synthesis and purification of a mitochondrial calcium uptake inhibitor, [(OH2)(NH3)4Ru(&#181;-O)Ru(NH3)4(OH2)]5+. The optimized synthesis of ...

The overall goal of the synthesis and purification is to relatively easily produce a ruthenium 360 analog used in mitochondrial calcium uptake assays that is 10 times more effective than commercially available ruthenium 360. This method can help answer key questions in the field of mitochondrial calcium biology by providing a pure inhibitor of mitochondrial calcium uptake. The main advantage of this technique is that the final product is both very potent and pure.Individuals new to this method may struggle because purification requires time and patience. Demonstrating the producer will be Sarah Nathan, a graduate student from my laboratory. Begin this procedure with synthesis of pentaammine chloro ruthenium dichloride as described in the text protocol.Dissolve 100 milligrams of pentaammine chloro ruthenium dichloride in 50 milliliters of one molar ammonium hydroxide solution in a 200 milliliter round bottom flask. Loosely cap the flask with a glass stopper and heat the reaction mixture at 75 degrees Celsius for six hours. Heating a sealed vessel results in a pressure build up.Make sure the glass stopper is loose to allow release of excess pressure. After six hours remove the reaction mixture from the heat. And stir at room temperature for four days to yield a dark green solution.To purify the resulting trans-diaqua octo amine mu-oxo diruthenium pentachloride by cation exchange chromatography first suspend five grams of mesh cation exchange resin in 10 milliliters of 0.1 molar HCL in a 25 milliliter beaker. Load this slurry into a 10 milliliter column affixed with a 50 milliliter solvent reservoir. Wash the resin with approximately 20 to 30 milliliters of 0.1 molar HCL until the elute is colorless.Next add concentrated HCL to the previously isolated green reaction solution to adjust the PH to two at which point the solution color changes to brown. Load this acidified solution to the cation exchange resin column by gently pipetting it on top of the resin. Let the elute completely drain and continue loading the solution.Repeat this process until the entire solution has been added. The top of the resin will be dark brown or black. The resin will decrease in volume slightly.Next cover the top of the resin with glass beads to prevent the resin from being disturbed when new solutions are added. Elute the column with 20 milliliters of one molar HCL. Then elute the column with 50 milliliters of an increased HCL concentration of 1.5 molar.A yellow solution will begin to come off the column. Next increase the HCL concentration to two molar and continue eluting with 150 to 200 milliliters. The eluant will start as a very pale yellow and go to a bright yellow.Wait until the eluant coming from the column is again very pale. Patience is critical at this step. The eluant must be very pale.Increase the HCL concentration further to 2.5 molar. Collect the eluant as fractions in test tubes. Finally increase the concentration to three molar HCL.The product will elute from the column as a green-brown solution. A red-brown fraction may also begin to come off the column. These fractions are ruthenium brown impurities and should not be pooled with the green-brown fractions.To test all of the fractions by UV-Vis spectroscopy add 100 microliters of a given fraction into two milliliters of three molar ammonia. Then analyze the mixture by UV-Vis spectroscopy. Fractions containing pure product will have a large absorbance band at 360 nanometers and a less intense absorbance at 600 nanometers.Absorbance at 480 nanometers is indicative of ruthenium brown and absorbance at 533 nanometers represents ruthenium red impurities. Other impurities are seen at absorbance of less than 300 nanometers. Pool fractions containing pure product and evaporate the solution to dryness by rotary evaporation before analysis of the sample in the solid state by IR spectroscopy.Proceed to evaluate mitochondrial calcium uptake inhibition by fluorescent spectroscopy as detailed in the text protocol. UV-Vis spectra of purified trans-diaqua octo amine mu-oxo diruthenium pentachloride is characterized by the major and minor absorptions at 360 nanometers and 600 nanometers respectively. Conversely an impure mixture shows absorption bands at 533 nanometers from ruthenium red impurities and at 275 to 300 nanometers from starting material.Solid state characterization using infrared spectroscopy has the expected stretches from the amines. As well as the ruthenium oxygen ruthenium stretch at 850 inverse centimeters. Permeabalized HeLa cells treated with a calcium sensitive fluorescent dye and trans-diaqua octo amine mu-oxo diruthenium pentachloride show inhibition of calcium uptake into the mitochondria.While attempting the procedure it is important to remember to allow the fractions to completely elute. Patience will yield a pure product. After watching this video you should have a good understanding of how to synthesize, purify and characterize this potent ruthenium 360 analog.Mitochondrial calcium levels regulate a wide range of intercellular processes including bioenergetics and controlled cell death. The inhibitor produced from this method can be applied in studies to understand the role of mitochondrial calcium biology in mediating other biological processes. Don't forget that working with concentrated acids and bases are corrosive and precautions such as wearing proper PPE should always be taken while performing this procedure.

synthesis-evaluation-ruthenium-based-mitochondrial-calcium-uptake

Research

JoVE Journal

Chemistry

Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

Seeded Synthesis of CdSe/CdS Rod and Tetrapod Nanocrystals

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded synthesis strategy is used in which spherical seeds of CdSe are prepared first using a hot-injection technique. By controlling the crystal structure of the seed to be either wurtzite or zinc-blende, the subsequent hot-injection growth of CdS off of the seed results in either a rod-shaped or tetrapod-shaped nanocrystal, respectively. The phase and morphology of the synthesized nanocrystals are confirmed using X-ray diffraction and transmission electron microscopy, demonstrating that the nanocrystals are phase-pure and have a consistent morphology. The extinction coefficient and quantum yield of the synthesized nanocrystals are calculated using UV-Vis absorption spectroscopy and photoluminescence spectroscopy. The rods and tetrapods exhibit extinction coefficients and quantum yields that are higher than that of the bare seeds. This synthesis demonstrates the precise arrangement of materials that can be achieved at the nanoscale by using a seeded synthetic approach.

A protocol for the seeded synthesis of rod-shaped and tetrapod-shaped multicomponent nanostructures consisting of CdS and CdSe is presented.

We demonstrate a method for the synthesis of multicomponent nanostructures consisting of CdS and CdSe with rod and tetrapod morphologies. A seeded ...

Anticancer Metal Complexes: Synthesis and Cytotoxicity Evaluation by the MTT Assay

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; therefore their preparation should be conducted under an inert atmosphere. Evaluation of the anticancer activity of these complexes can be achieved by the MTT assay.
The MTT assay is a colorimetric viability assay based on enzymatic reduction of the MTT molecule to formazan when it is exposed to viable cells. The outcome of the reduction is a color change of the MTT molecule. Absorbance measurements relative to a control determine the percentage of remaining viable cancer cells following their treatment with varying concentrations of a tested compound, which is translated to the compound anticancer activity and its IC50 values. The MTT assay is widely common in cytotoxicity studies due to its accuracy, rapidity, and relative simplicity.
Herein we present a detailed protocol for the synthesis of air sensitive metal based drugs and cell viability measurements, including preparation of the cell plates, incubation of the compounds with the cells, viability measurements using the MTT assay, and determination of IC50 values.

A method for synthesis of air-sensitive titanium and vanadium anticancer agents is described, along with the evaluation of their cytotoxic activity towards human cancer cell line by the MTT Assay.

Titanium (IV) and vanadium (V) complexes are highly potent anticancer agents. A challenge in their synthesis refers to their hydrolytic instability; ...

Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. Diiodomethyllithium is prepared by the deprotonation of diiodomethane with LiHMDS, in a THF/diethyl ether mixture, at -78 &#176;C in the dark. These conditions are essential for the stability of the LiCHI2 reagent generated. The subsequent dropwise addition of N-Ts aldimines to the preformed diiodomethyllithium solution affords an amino-diiodide intermediate, which is not isolated. Rapid warming of the reaction mixture to 0 &#176;C promotes cyclization to afford iodoaziridines with exclusive cis-diastereoselectivity. The addition and cyclization stages of the reaction are mediated in one reaction flask by careful temperature control.
Due to the sensitivity of the iodoaziridines to purification, assessment of suitable methods of purification is required. A protocol to assess the stability of sensitive compounds to stationary phases for column chromatography is described. This method is suitable to apply to new iodoaziridines, or other potentially sensitive novel compounds. Consequently this method may find application in range of synthetic projects. The procedure involves firstly the assessment of the reaction yield, prior to purification, by 1H NMR spectroscopy with comparison to an internal standard. Portions of impure product mixture are then exposed to slurries of various stationary phases appropriate for chromatography, in a solvent system suitable as the eluent in flash chromatography. After stirring for 30 min to mimic chromatography, followed by filtering, the samples are analyzed by 1H NMR spectroscopy. Calculated yields for each stationary phase are then compared to that initially obtained from the crude reaction mixture. The results obtained provide a quantitative assessment of the stability of the compound to the different stationary phases; hence the optimal can be selected. The choice of basic alumina, modified to activity IV, as a suitable stationary phase has allowed isolation of certain iodoaziridines in excellent yield and purity.

A protocol for the diastereoselective one-pot preparation of cis-N-Ts-iodoaziridines is described. The generation of diiodomethyllithium, addition to N-Ts aldimines and cyclization of the amino gem-diiodide intermediate to iodoaziridines is demonstrated. Also included is a protocol to rapidly and quantitatively assess the most appropriate stationary phase for purification by chromatography.

The highly diastereoselective preparation of cis-N-Ts-iodoaziridines through reaction of diiodomethyllithium with N-Ts aldimines is described. ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Synthesis and Exfoliation of Discotic Zirconium Phosphates to Obtain Colloidal Liquid Crystals

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and engineers. Growth of such anisotropic nanocrystals through a simple chemical method is a challenging task. In this study, we fabricate discotic nanodisks of zirconium phosphate [Zr(HPO4)2&#183;H2O] as a model material using hydrothermal, reflux and microwave-assisted methods. Growth of crystals is controlled by duration time, temperature, and concentration of reacting species. The novelty of the adopted methods is that discotic crystals of size ranging from hundred nanometers to few micrometers can be obtained while keeping the polydispersity well within control. The layered discotic crystals are converted to monolayers by exfoliation with tetra-(n)-butyl ammonium hydroxide [(C4H9)4NOH, TBAOH]. Exfoliated disks show isotropic and nematic liquid crystal phases. Size and polydispersity of disk suspensions is highly important in deciding their phase behavior.

A two dimensional model material of discotic zirconium phosphate was developed. The inorganic crystal with lamellar structure was synthesized by hydrothermal, reflux, and microwave-assisted methods. On exfoliation with organic molecules, layered crystals can be converted to monolayers, and nematic liquid crystal phase was formed at sufficient concentration of monolayers.

Due to their abundance in natural clay and potential applications in advanced materials, discotic nanoparticles are of interest to scientists and ...

Synthesis and Structure Determination of &#181;-Conotoxin PIIIA Isomers with Different Disulfide Connectivities

Peptides with a high number of cysteines are usually influenced regarding the three-dimensional structure by their disulfide connectivity. It is thus highly important to avoid undesired disulfide bond formation during peptide synthesis, because it may result in a completely different peptide structure, and consequently altered bioactivity. However, the correct formation of multiple disulfide bonds in a peptide is difficult to obtain by using standard self-folding methods such as conventional buffer oxidation protocols, because several disulfide connectivities can be formed. This protocol represents an advanced strategy required for the targeted synthesis of multiple disulfide-bridged peptides which cannot be synthesized via buffer oxidation in high quality and quantity. The study demonstrates the application of a distinct protecting group strategy for the synthesis of all possible 3-disulfide-bonded peptide isomers of &#181;-conotoxin PIIIA in a targeted way. The peptides are prepared by Fmoc-based solid phase peptide synthesis using a protecting group strategy for defined disulfide bond formation. The respective pairs of cysteines are protected with trityl (Trt), acetamidomethyl (Acm), and tert-butyl (tBu) protecting groups to make sure that during every oxidation step only the required cysteines are deprotected and linked. In addition to the targeted synthesis, a combination of several analytical methods is used to clarify the correct folding and generation of the desired peptide structures. The comparison of the different 3-disulfide-bonded isomers indicates the importance of accurate determination and knowledge of the disulfide connectivity for the calculation of the three-dimensional structure and for interpretation of the biological activity of the peptide isomers. The analytical characterization includes the exact disulfide bond elucidation via tandem mass spectrometry (MS/MS) analysis which is performed with partially reduced and alkylated derivatives of the intact peptide isomer produced by an adapted protocol. Furthermore, the peptide structures are determined using 2D nuclear magnetic resonance (NMR) experiments and the knowledge obtained from MS/MS analysis.

Cysteine-rich peptides fold into distinct three-dimensional structures depending on their disulfide connectivity. Targeted synthesis of individual disulfide isomers is required when buffer oxidation does not lead to the desired disulfide connectivity. The protocol deals with the selective synthesis of 3-disulfide-bonded peptides and their structural analysis using NMR and MS/MS studies.

Peptides with a high number of cysteines are usually influenced regarding the three-dimensional structure by their disulfide connectivity. It is thus ...

Solid-phase Synthesis of [4.4] Spirocyclic Oximes

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of solid-phase synthesis, regenerating Michael (REM) linker strategies, and 1,3-dipolar cycloaddition, a library of structurally similar heterocycles, both with and without a spirocyclic center, can be constructed. The main advantages of the solid-support synthesis are as follows: first, each reaction step can be driven to completion using a large excess of reagents resulting in high yields; next, the use of commercially available starting materials and reagents keep the costs low; finally, the reaction steps are easy to purify via simple filtration. The REM linker strategy is attractive because of its recyclability and traceless nature. Once a reaction scheme is completed, the linker can be reused multiple times. In a typical solid-phase synthesis, the product contains either a part of or the whole linker, which can prove undesirable. The REM linker is &#34;traceless&#34; and the point of attachment between the product and the polymer is indistinguishable. The high diastereoselectivity of the intramolecular 1,3-dipolar cycloaddition is well documented. Limited by the insolubility of the solid support, the reaction progression can only be monitored by a change in the functional groups (if any) via infrared (IR) spectroscopy. Thus, the structural identification of intermediates cannot be characterized by conventional nuclear magnetic resonance (NMR) spectroscopy. Other limitations to this method stem from the compatibilities of the polymer/linker to the desired chemical reaction scheme. Herein we report a protocol that allows for the convenient production of spirocyclic heterocycles that, with simple modifications, can be automated with high-throughput techniques.

Here we present a protocol to demonstrate an efficient method for the synthesis of spirocyclic heterocycles. The five-step process utilizes solid-phase synthesis and regenerating Michael linker strategies. Generally difficult to synthesize, we present a customizable method for the synthesis of spirocyclic molecules otherwise inaccessible to other modern approaches.

A convenient synthetic route for spirocyclic heterocycles is well sought after due to the molecule&#39;s potential use in biological systems. By means of ...

Synthesis of Esters Via a Greener Steglich Esterification in Acetonitrile

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the reaction is commonly performed using chlorinated or amide solvent systems, which are hazardous to human health and the environment. Our methodology utilizes acetonitrile as a greener and less hazardous solvent system. This protocol exhibits rates and yields that are comparable to traditional solvent systems and employs an extraction and wash sequence that eliminates the need for the purification of the ester product via column chromatography. This general method can be used to couple a variety of carboxylic acids with 1&#176; and 2&#176; aliphatic alcohols, benzylic and allylic alcohols, and phenols to obtain pure esters in high yields. The goal of the protocol detailed here is to provide a greener alternative to a common esterification reaction, which could serve useful for ester synthesis in both academic and industrial applications.

A modified Steglich esterification reaction was used to synthesize a small library of ester derivatives with primary and secondary alcohols. The methodology uses a non-halogenated and greener solvent, acetonitrile, and enables product isolation in high yields without the need for chromatographic purification.

The Steglich esterification is a widely-used reaction for the synthesis of esters from carboxylic acids and alcohols. While efficient and mild, the ...

Synthesis Method for Cellulose Nanofiber Biotemplated Palladium Composite Aerogels

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often result in fragile aerogels with poor shape control. The use of carboxymethylated cellulose nanofibers (CNFs) to form a covalently bonded hydrogel allows for the reduction of metal ions such as palladium on the CNFs with control over both nanostructure and macroscopic aerogel monolith shape after supercritical drying. Crosslinking the carboxymethylated cellulose nanofibers is achieved using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) in the presence of ethylenediamine. The CNF hydrogels maintain their shape throughout synthesis steps including covalent crosslinking, equilibration with precursor ions, metal reduction with high concentration reducing agent, rinsing in water, ethanol solvent exchange, and CO2 supercritical drying. Varying the precursor palladium ion concentration allows for control over the metal content in the final aerogel composite through a direct ion chemical reduction rather than relying on the relatively slow coalescence of pre-formed nanoparticles used in other sol-gel techniques. With diffusion as the basis to introduce and remove chemical species into and out of the hydrogel, this method is suitable for smaller bulk geometries and thin films. Characterization of the cellulose nanofiber-palladium composite aerogels with scanning electron microscopy, X-ray diffractometry, thermal gravimetric analysis, nitrogen gas adsorption, electrochemical impedance spectroscopy, and cyclic voltammetry indicates a high surface area, metallized palladium porous structure.

A synthesis method for cellulose nanofiber biotemplated palladium composite aerogels is presented.The resulting composite aerogel materials offer potential for catalysis, sensing, and hydrogen gas storage applications.

Here, a method to synthesize cellulose nanofiber biotemplated palladium composite aerogels is presented. Noble metal aerogel synthesis methods often ...