This work was funded by the Spanish Ministerio de Econom&#236;a y Competitividad (CTQ 2013-41067-P). H.B. acknowledge with thanks a MEC-FPI grant.

1. Functionalization of 2,15-Dimethylhexahelicene
<ol>
	<li>Dibromination of 2,15-dimethylhexahelicene
	<ol>
		<li>Weigh 0.356 g (1.0 mmol) of 2,15-dimethylhexahelicene, 0.374 g (2.1 mmol) of freshly recrystallized N-bromosuccinimide (NBS) and 24 mg (0.07 mmol) of benzoyl peroxide (BPO) (70% wt with 30% of water as stabilizer). Place all solids in a 100 ml Schlenk flask with a magnetic stir bar. Put under nitrogen atmosphere by three cycles of gas evacuation followed by refilling with inert gas in the Schlenk line.</li>
		<li>Add 21 ml of carbon tetrachloride (CCl4). Degas the solution by the same evacuation/refilling process (step 1.1.1) with vigorous stirring and carefully in order to prevent massive loss of solvent.</li>
		<li>Heat at reflux (77 &#176;C) the mixture with an oil bath for 4 hours. Check the reaction by 1H-nuclear magnetic resonance (NMR). Doublets between 3.7 ppm and 4.0 ppm should appear. They indicate the presence of diastereotopic -CH2- groups (Figure 1).</li>
		<li>Once finished, cool the mixture to room temperature and remove the solvent under vacuum. Set up a trap filled with liquid nitrogen to avoid pump contamination.</li>
		<li>Redissolve the crude in 30 ml of dichloromethane (DCM), transfer to a round-bottom flask and mix with 4 g of silica gel (typically add 5-fold the crude weight). Concentrate the mixture in a rotary evaporator.</li>
		<li>In the meantime, fill a column (length around 20 cm and a thickness of 4.5 cm) with SiO2 gel mixed previously with hexane/ethyl acetate (95:5) as the mobile phase. Add the mixture to the top of the column and then add a layer of sand (2 cm).</li>
		<li>Carefully pour in the new mobile phase and perform the chromatography by collecting fractions in test tubes (typically 20 ml per tube and 4 ml near the expected product elution). Check fractions by thin layer chromatography (TLC) with the same mobile phase (hexane/ethyl acetate 95:5) and image under UV light. The expected product (4b) should elute at a Retention factor (Rf) of 0.35 as a yellow oil after combining all wanted fractions and removing off the solvent in the rotary evaporator. 334 mg should be obtained (yield 65%). 
		NOTE: All Schlenk techniques, the use of an oil bath for heating and column chromatography settings will be widely utilized in most of the protocols, so from now on, they will not be covered in detail and only a few comments, when necessary, will be given.</li>
	</ol>
	</li>
</ol>
<img alt="Figure 1" src="/files/ftp_upload/53954/53954fig1.jpg" /> 
Figure 1. 1H-NMR spectra (500 MHz, CDCl3) of 2,15-dimethylhelicene (top) and an aliquot taken after 2 hr. New signals, corresponding to -CH2-, are depicted in a red circle (bottom). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53954/53954fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<ol start="2">
	<li>Synthesis of 2,15-bis(azidomethyl)hexahelicene
	<ol>
		<li>Weigh 0.103 g (0.2 mmol) of 2,15-bis(bromomethyl)hexahelicene and 0.390 g (6 mmol) of sodium azide. Place both solids in a 50 ml Schlenk flask equipped with magnetic bar and put under nitrogen atmosphere.</li>
		<li>Mix 8.6 ml of tetrahydrofuran (THF) with 5.2 ml of water (H2O) and pour the mixture of solvents into the Schlenk flask. Degas the solution.</li>
		<li>Heat at reflux (65 &#176;C) for 3 hr. Check the reaction by 1H-NMR. -CH2- signals should shift to 3.75 ppm (Figure 2).</li>
		<li>Afterwards, cool down the mixture to room temperature and remove THF under vacuum. Dilute with 50 ml of H2O.</li>
		<li>Transfer the mixture to a separatory funnel and extract three times with 40 ml of DCM. Combine all organic phases and wash with pure H2O (50 ml).</li>
		<li>Purify the crude by column chromatography on silica gel using hexane/ethyl acetate (85:15) as the mobile phase to give a yellow oil at Rf=0.38 corresponding to 2,15-bis(azomethyl)hexahelicene (5b). 70 mg should be obtained (yield 80%).</li>
	</ol>
	</li>
</ol>
<img alt="Figure 2" src="/files/ftp_upload/53954/53954fig2.jpg" /> 
Figure 2: 1H-NMR spectra (500 MHz, CDCl3) of 4b (top) and an aliquot taken after 3 hr (bottom). Note the changes in the aliphatic region. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53954/53954fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
2. Functionalization of Corannulene
<ol>
	<li>Monobromination of Corannulene
	<ol>
		<li>Weigh 0.125 g (0.5 mmol) of corannulene, 89 mg (0.5 mmol) of freshly recrystallized NBS and 17 mg of gold(III) chloride hydrate.</li>
		<li>Place all compounds into a 10 ml vial specially designed for microwave reactions equipped with a magnetic bar and then put into a nitrogen atmosphere with the help of a 2-necked round-bottom flask.</li>
		<li>Add 7 ml of 1,2-dichloroethane (DCE) and degas the solution.</li>
		<li>Sonicate the mixture for 2 min to disperse gold salt particles.</li>
		<li>Heat inside the microwave reactor at 100 &#176;C for 2 hr.</li>
		<li>When finished, transfer the crude to a round-bottom flask and remove solvent by rotary evaporation.</li>
		<li>Purify the crude by column chromatography on SiO2 gel using hexane as mobile phase. 
		NOTE: Bromocorannulene (4a) is obtained as a yellow solid at Rf=0.38. 99 mg should be obtained (yield 60%). Unreacted corannulene (3a) can be recovered and stored for further uses. It appears at Rf=0.29.</li>
	</ol>
	</li>
	<li>Sonogashira Coupling of Bomocorannulene and Ethynyltrimethylsilane
	<ol>
		<li>Weigh 49 mg (0.15 mmol) of bromocorannulene, 11 mg (0.015 mmol) of [PdCl2(dppf)]49,50 (dppf being 1,1-&#39;bis(diphenylphsphino)ferrocene, 3 mg (0.015 mmol) of CuI.51</li>
		<li>Place all solids in a 50 ml Schlenk flask along with a magnetic bar and put under nitrogen atmosphere.</li>
		<li>Add 5.0 ml of triethylamine (NEt3) and degas the mixture.</li>
		<li>Finally, add 104 &#181;l (0.75 mmol) of ethynyltrimethylsilane.</li>
		<li>Sonicate the mixture for 2 min to disperse metal salt particles.</li>
		<li>Heat at 85 &#176;C for 24 hr with periodic sonication to prevent deposition of metal salts. 
		NOTE: The mixture color turned to black soon, indicating the presence of palladium(0).</li>
		<li>Cool down to room temperature and evaporate NEt3 in vacuo.</li>
		<li>Redissolve in 20 ml of DCM and purify by column chromatography on silica gel eluting with hexane to give a yellow solid at Rf=0.28 corresponding to 5a. 41 mg should be obtained (yield 78%). 
		NOTE: If the crude is filtered through a Celite pad in DCM, a reasonable pure sample might be obtained, however phosphine derivatives are not removed totally.</li>
	</ol>
	</li>
	<li>Preparation of Ethynylcorannulene by TMS Deprotection
	<ol>
		<li>Weigh 35 mg (0.10 mmol) of 5a and 7.3 mg (0.125 mmol) of anhydrous potassium fluoride.</li>
		<li>Place all solids in a 50 ml Schlenk flask equipped with a magnetic bar and put under nitrogen atmosphere.</li>
		<li>Mix 4 ml of THF and 4 ml of methanol (MeOH) and pour the mixture into the Schlenk flask. Degas thoroughly.</li>
		<li>Allow to react at room temperature, Keep the flask away from light by covering it with an opaque film. Check the reaction by 1H-NMR by looking at 3.48 ppm. A signal corresponding to -CCH must emerge (Figure 3). 
		NOTE: Although this compound bears a terminal alkyne that is reactive and decomposes easily, we found no problems during the work up described below. It was carried out under natural light.</li>
		<li>Once finished, remove THF under vacuum and dilute with 10 ml of water, transferring everything to a separatory funnel.</li>
		<li>Extract with DCM (3 x 15 ml), combine all organic phases in a round-bottom flask and concentrate in a rotary evaporator at room temperature to finally get a yellow solid corresponding to 6a. 27 mg should be obtained (quantitative yield).</li>
	</ol>
	</li>
</ol>
<img alt="Figure 3" src="/files/ftp_upload/53954/53954fig3.jpg" /> 
Figure 3: 1H-NMR spectra (500 MHz, CDCl3) of 5a (top) and 6a (bottom). -CCH singlet is depicted in a red circle. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53954/53954fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
3. Final Assembly by Click Chemistry
<ol>
	<li>Weigh 15.3 mg (0.035 mmol) of 5b, 20.0 mg (0.073 mmol) of 6a, 1.4 mg (0.007 mmol) of ascorbic acid sodium salt, 1.7 mg (0.007 mmol) of CuSO4&#183;5H2O.</li>
	<li>Place all solids in a 50 ml Schlenk flask equipped with a magnetic bar and put under nitrogen atmosphere.</li>
	<li>Mix 3 ml of H2O and 12 ml of THF and pour the mixture into the Schlenk flask. Degas the solution thoroughly.</li>
	<li>Heat at 65 &#176;C for 3 days with a condenser connected to the top of the flask and check periodically the reaction to control temperature, stirring and solvent volume. Check the reaction by 1H-NMR. The signal at 3.48 ppm should disappear and be shifted to 7.27 ppm indicating the consumption of ethynyl corannulene and the existence of the triazole unit (Figure 4).</li>
	<li>When finished, remove THF under vacuum and dilute with 20 ml of water, transferring the mixture to a separatory funnel.</li>
	<li>Extract with DCM (3 x 20 ml), combine all organic phases in a round-bottom flask and concentrate in a rotary evaporator.</li>
	<li>Purify the crude by column chromatography on SiO2 gel eluting with hexane/ethyl acetate (1:1) to give a pale yellow solid at Rf = 0.59 corresponding to 7. 27 mg should be obtained (yield 75%).</li>
</ol>
<img alt="Figure 4" src="/files/ftp_upload/53954/53954fig4.jpg" /> 
Figure 4: 1H-NMR spectra (500 MHz, CDCl3) of 5b (top), 6a (middle) and an aliquot taken after 2 days (bottom). Note the disappearance of -CCH signal in the crude. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53954/53954fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

The authors have nothing to disclose.

Final compound 7 has been prepared after 6 steps from nonplanar polyaromatic precursors 3a and 3b with moderate to very good yields at each reaction. The main limitation observed in this route was the bromination of both nonplanar polyaromatic compounds. However, in the case of compound 4a, an important amount of free corannulene can be recovered for further uses. The synthesis of 4<stro...

Due to their special geometry, corannulene and helicenes are molecules that can adopt a structure far from planarity and give rise to interesting properties.1-15 In the last few years, the search of molecular receptors for carbon nanotubes and fullerenes is a very active area16-19 due, mainly, to their potential applications as materials for organic solar cells, transistors, sensors and other devices.20-28 The excellent complementarity in shape between corannulene and a fullerene have attracted the attention of several researchers with the aim of designing molecular receptors capable of establishing supramolecular association by dispersion forces.29-39
The chemistry of the above mentioned nonplanar polyaromatic compounds is similar to that described for totally planar molecules, but it is sometimes difficult to find suitable conditions to achieve desired selectivities and yields.40 In this work we present the synthesis of a molecule (7) having three polyaromatic units in a few steps with good yields by applying easy and typical techniques found in every research laboratory. The molecule is of great importance because it can adopt a pincer-like conformation to establish good interactions with C6037 in solution; and it may open a research line as a potential receptor for higher chiral fullerenes thanks to the helicene linker, which is a chiral molecule due to the existence of a stereogenic axis.41-45 However, only racemic helicene will be used in this work.
At this point, the only limitation to synthesize these receptors is the preparation of helicenes and corannulenes, since they are not commercially available. But, according to new methods published elsewhere46-48 they can be obtained in suitable amounts in a reasonable short period of time.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>2,15-Dimethylhexahelicene</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Prepared according to reference 5b,c in the main text.</td>
		</tr>
		<tr>
			<td>Corannulene</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Prepared according to reference 5a in the main text.</td>
		</tr>
		<tr>
			<td>N-Bromosuccinimide (NBS)</td>
			<td>Sigma Aldrich</td>
			<td>B8.125-5</td>
			<td>ReagentPlus&#174;, 99%. Recrystallized from hot water.</td>
		</tr>
		<tr>
			<td>Benzoyl peroxide (BPO)</td>
			<td>Sigma Aldrich</td>
			<td>B-2030</td>
			<td>~70% (titration). 30% water as stabilizer.</td>
		</tr>
		<tr>
			<td>Sodium azide</td>
			<td>Sigma Aldrich</td>
			<td>S2002</td>
			<td>ReagentPlus&#174;, &#8805;99.5%.</td>
		</tr>
		<tr>
			<td>Gold (III) chloride Hydrate</td>
			<td>Sigma Aldrich</td>
			<td>50778</td>
			<td>puriss. p.a., ACS reagent, &#8805;49% Au basis.</td>
		</tr>
		<tr>
			<td>Ethynyltrimethylsilane</td>
			<td>Sigma Aldrich</td>
			<td>218170</td>
			<td>98%.</td>
		</tr>
		<tr>
			<td>[PdCl2(dppf)]</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Prepared according to reference 6 in the main text.</td>
		</tr>
		<tr>
			<td>CuI</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Prepared according to reference 7 in the main text.</td>
		</tr>
		<tr>
			<td>KF</td>
			<td>Sigma Aldrich</td>
			<td>307599</td>
			<td>99%, spray-dried.</td>
		</tr>
		<tr>
			<td>(+)-Sodium L-ascorbate</td>
			<td>Fluka</td>
			<td>11140</td>
			<td>BioXtra, &#8805;99.0% (NT).</td>
		</tr>
		<tr>
			<td>Copper(II) Sulphate 5-hydrate</td>
			<td>Panreac</td>
			<td>131270</td>
			<td>for analysis.</td>
		</tr>
		<tr>
			<td>Carbon tetrachloride (CCl4)</td>
			<td>Fluka</td>
			<td>87030</td>
			<td>for IR spectroscopy, &#8805;99.9%.</td>
		</tr>
		<tr>
			<td>Dichloromethane (DCM)</td>
			<td>Fisher Scientific</td>
			<td>D/1852/25</td>
			<td>Analytical reagent grade. Distilled prior to use.</td>
		</tr>
		<tr>
			<td>Hexane</td>
			<td>Fisher Scientific</td>
			<td>H/0355/25</td>
			<td>Analytical reagent grade. Distilled prior to use.</td>
		</tr>
		<tr>
			<td>Ethyl acetate</td>
			<td>Scharlau</td>
			<td>AC0145025S</td>
			<td>Reagent grade. Distilled prior to use.</td>
		</tr>
		<tr>
			<td>Tetrahydrofuran (THF)</td>
			<td>Fisher Scientific</td>
			<td>T/0701/25</td>
			<td>Analytical reagent grade. Distilled prior to use.</td>
		</tr>
		<tr>
			<td>1,2-Dichloroethane (DCE)</td>
			<td>Sigma Aldrich</td>
			<td>D6,156-3</td>
			<td>ReagentPlus&#174;, 99%.</td>
		</tr>
		<tr>
			<td>Methanol (MeOH)</td>
			<td>VWR</td>
			<td>20847.36</td>
			<td>AnalaR NORMAPUR.</td>
		</tr>
		<tr>
			<td>Triethyl amine (NEt3)</td>
			<td>Sigma Aldrich</td>
			<td>T0886</td>
			<td>&#8805;99%.</td>
		</tr>
		<tr>
			<td>Silica gel</td>
			<td>Acros</td>
			<td>360050010</td>
			<td>Particle size 40-60mm.</td>
		</tr>
		<tr>
			<td>Sand - low iron</td>
			<td>Fisher Scientific</td>
			<td>S/0360/63</td>
			<td>General purpose grade.</td>
		</tr>
		<tr>
			<td>TLC Silica gel 60 F254</td>
			<td>Merck</td>
			<td>1.05554.0001</td>
			<td></td>
		</tr>
		<tr>
			<td>Monowave 300 (Microwave reactor)</td>
			<td>Anton Para</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator</td>
			<td>Grupo Selecta</td>
			<td>3000513</td>
			<td>6 Litres.</td>
		</tr>
	</tbody>
</table>

preparation of a corannulene-functionalized hexahelicene by copper(i)-catalyzed alkyne-azide cycloaddition of nonplanar polyaromatic units

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar polyaromatic units, which are two corannulene moieties and a racemic hexahelicene linking them. The compound described in this work is a good host for fullerenes. Several common organic reactions, such as free-radical reactions, C-C coupling or click chemistry, are employed demonstrating the versatility of functionalization that this compound can accept. All of these reactions work for planar aromatic molecules. With subtle modifications, it is possible to achieve similar results for nonplanar polyaromatic compounds.

Corannulene (3a) and 2,15-dimethylhexahelicene (3b) could be prepared following current methods46-48 in a straightforward fashion with very good yields (Figure 5). Both share a common molecule, 2,7-dimethylnaphthalene, as the starting material, giving rise to a divergent to convergent synthesis of the final molecule.
<img alt="Fi...

Watch this Scientific Journal Video about Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units at JoVE.com

Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

Here, we present a protocol to synthesize a complex organic compound comprised of three nonplanar polyaromatic units, assembled easily with reasonable yields.

Preparation of a Corannulene-functionalized Hexahelicene by Copper(I)-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

The main purpose of this video is to show 6 reaction steps of a convergent synthesis and prepare a complex molecule containing up to three nonplanar ...

preparation-corannulene-functionalized-hexahelicene-copper-i

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11.4K Views.  Universidad de Valladolid. Here, we present a protocol to synthesize a complex organic compound comprised of three nonplanar polyaromatic units, assembled easily with reasonable yields.

Video: Preparation of a Corannulene-functionalized Hexahelicene by CopperI-catalyzed Alkyne-azide Cycloaddition of Nonplanar Polyaromatic Units

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 ...

Isolation and Preparation of Bacterial Cell Walls for Compositional Analysis by Ultra Performance Liquid Chromatography

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the face of turgor pressures several atmospheres in magnitude. Across the diverse shapes and sizes of the bacterial kingdom, the cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by short peptides. Peptidoglycan&#8217;s central importance to bacterial physiology underlies its use as an antibiotic target and has motivated genetic, structural, and cell biological studies of how it is robustly assembled during growth and division. Nonetheless, extensive investigations are still required to fully characterize the key enzymatic activities in peptidoglycan synthesis and the chemical composition of bacterial cell walls. High Performance Liquid Chromatography (HPLC) is a powerful analytical method for quantifying differences in the chemical composition of the walls of bacteria grown under a variety of environmental and genetic conditions, but its throughput is often limited. Here, we present a straightforward procedure for the isolation and preparation of bacterial cell walls for biological analyses of peptidoglycan via HPLC and Ultra Performance Liquid Chromatography (UPLC), an extension of HPLC that utilizes pumps to deliver ultra-high pressures of up to 15,000 psi, compared with 6,000 psi for HPLC. In combination with the preparation of bacterial cell walls presented here, the low-volume sample injectors, detectors with high sampling rates, smaller sample volumes, and shorter run times of UPLC will enable high resolution and throughput for novel discoveries of peptidoglycan composition and fundamental bacterial cell biology in most biological laboratories with access to an ultracentrifuge and UPLC.

The bacterial cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by peptides. Ultra Performance Liquid Chromatography provides high resolution and throughput for novel discoveries of peptidoglycan composition. We present a procedure for the isolation of cell walls (sacculi) and their subsequent preparation for analysis via UPLC.

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the ...

Real-time Monitoring of Reactions Performed Using Continuous-flow Processing: The Preparation of 3-Acetylcoumarin as an Example

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible to ensure consistent product quality over time using this technique. We here show how to interface a commercially available flow unit with a Raman spectrometer. The Raman flow cell is placed after the back-pressure regulator, meaning that it can be operated at atmospheric pressure. In addition, the fact that the product stream passes through a length of tubing before entering the flow cell means that the material is at RT. It is important that the spectra are acquired under isothermal conditions since Raman signal intensity is temperature dependent. Having assembled the apparatus, we then show how to monitor a chemical reaction, the piperidine-catalyzed synthesis of 3-acetylcoumarin from salicylaldehyde and ethyl acetoacetate being used as an example. The reaction can be performed over a range of flow rates and temperatures, the in-situ monitoring tool being used to optimize conditions simply and easily.

Real-time monitoring allows for fast optimization of reactions performed using continuous-flow processing. Here the preparation of 3-acetylcoumarin is used as an example. The apparatus for performing in-situ Raman monitoring is described, as are the steps required to optimize the reaction.

By using inline monitoring, it is possible to optimize reactions performed using continuous-flow processing in a simple and rapid way. It is also possible ...

Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles

Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar concentration forming hydrophobic cores surrounded by hydrophilic shells in aqueous environments. The core of these micelles can be utilized to load hydrophobic, poorly water soluble drugs like docetaxel (DTX) and everolimus (EVR). Systematic characterization of the micelle structure and drug loading capabilities are important before in vitro and in vivo studies can be conducted. The goal of the protocol described herein is to provide the necessary characterization steps to achieve standardized micellar products. DTX and EVR have intrinsic solubilities of 1.9 and 9.6 &#181;g/ml respectively Preparation of these micelles can be achieved through solvent casting which increases the aqueous solubility of DTX and EVR to 1.86 and 1.85 mg/ml, respectively. Drug stability in micelles evaluated at room temperature over 48 hr indicates that 97% or more of the drugs are retained in solution. Micelle size was assessed using dynamic light scattering and indicated that the size of these micelles was below 50 nm and depended on the molecular weight of the polymer. Drug release from the micelles was assessed using dialysis under sink conditions at pH 7.4 at 37 oC over 48 hr. Curve fitting results indicate that drug release is driven by a first order process indicating that it is diffusion driven.

The goal of this protocol is to describe the preparation and characterization of physically entrapped, poorly water soluble drugs in micellar drug delivery systems composed of amphiphilic block copolymers.

Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar ...

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled (functionalized) CNTs are used as stabilizers to produce Pickering type oil-in-water (O/W) emulsions. Lipids namely, Dimodan U and Phytantriol are used as emulsifiers, which in excess water self-assemble into the bicontinuous cubic Pn3m phase. This highly viscous phase is fragmented into smaller particles using a probe ultrasonicator in presence of conventional surfactant stabilizers or CNTs as done here. Initially, the CNTs (powder form) are dispersed in water followed by further ultrasonication with the molten lipid to form the final emulsion. During this process the CNTs get coated with lipid molecules, which in turn are presumed to surround the lipid droplets to form a particulate emulsion that is stable for months. The average size of CNT-stabilized nanostructured lipid particles is in the submicron range, which compares well with the particles stabilized using conventional surfactants. Small angle X-ray scattering data confirms the retention of the original Pn3m cubic phase in the CNT-stabilized lipid dispersions as compared to the pure lipid phase (bulk state). Blue shift and lowering of the intensities in characteristic G and G&#39; bands of CNTs observed in Raman spectroscopy characterize the interaction between CNT surface and lipid molecules. These results suggest that the interactions between the CNTs and lipids are responsible for their mutual stabilization in aqueous solutions. As the concentrations of CNTs employed for stabilization are very low and lipid molecules are able to functionalize the CNTs, the toxicity of CNTs is expected to be insignificant while their biocompatibility is greatly enhanced. Hence the present approach finds a great potential in various biomedical applications, for instance, for developing hybrid nanocarrier systems for the delivery of multiple functional molecules as in combination therapy or polytherapy.

We report on a smart application of carbon nanotubes for kinetic stabilization of lipid particles that contain self-assembled nanostructures in their cores. The preparation of lipid particles requires rather low concentrations of carbon nanotubes permitting their use in biomedical applications such as drug delivery.

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled ...

Preparation of Macroporous Epitaxial Quartz Films on Silicon by Chemical Solution Deposition

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step process based on the preparation of a sol in a one-pot synthesis which is followed by the deposition of a gel film on Si(100) substrates by evaporation induced self-assembly using the dip-coating technique and ends with a thermal treatment of the material to induce the gel crystallization and the growth of the quartz film. The formation of a silica gel is based on the reaction of a tetraethyl orthosilicate and water, catalyzed by HCl, in ethanol. However, the solution contains two additional components that are essential for preparing mesoporous epitaxial quartz films from these silica gels dip-coated on Si. Alkaline earth ions, like Sr2+ act as glass melting agents that facilitate the crystallization of silica and in combination with cetyl trimethylammonium bromide (CTAB) amphiphilic template form a phase separation responsible of the macroporosity of the films. The good matching between the quartz and silicon cell parameters is also essential in the stabilization of quartz over other SiO2 polymorphs and is at the origin of the epitaxial growth.

A protocol is presented for the preparation of piezoelectric macroporous epitaxial films of quartz on silicon by solution chemistry using dip-coating and thermal treatments in air.

This work describes the detailed protocol for preparing piezoelectric macroporous epitaxial quartz films on silicon(100) substrates. This is a three-step ...

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE). Characterization of the copolymer revealed a narrow molecular distribution (PDI &#60; 1.03) and confirmed the degree of polymerization of mPEG122-b-(PheGE)15. The critical micelle concentration of the copolymer was evaluated using an established fluorescence method with the aggregation behavior evaluated by dynamic light scattering and transmission electronic microscopy. The potential of the copolymer for use in drug delivery applications was evaluated in a preliminary manner including in vitro biocompatibility, loading and release of the hydrophobic anti-cancer drug doxorubicin (DOX). A stable micelle formulation of DOX was prepared with drug loading levels up to 14% (wt%), drug loading efficiencies &#62; 60% (w/w) and sustained release of drug over 4 days under physiologically relevant conditions (acidic and neutral pH, presence of albumin). The high drug loading level and sustained release is attributed to stabilizing &#960;-&#960; interactions between DOX and the core-forming block of the micelles.

The key steps of living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE) are described. The resulting block copolymer micelles (BCMs) were loaded with doxorubicin 14% (wt%) and sustained release of drug over 4 days under physiologically relevant conditions was obtained.

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl ...

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of Phosphorus(I)

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable low-valent-phosphorus-containing compound acts as a useful P+ transfer agent. Unlike traditional methods employed to access low-coordinate phosphorus species which usually require pyrophoric phosphorus-containing precursors (white phosphorus, Tris(trimethylsilyl)phosphine, etc.), or harsh reducing agents (alkali metals, potassium graphite, etc.), the current approach does not involve pyrophoric or explosive reagents and can be done on large scales (&#62;20 g) in excellent yields by undergraduates with basic air-free synthetic training. The bromide counter ion is readily exchanged with other anions such as tetraphenyl borate (described herein) using typical salt metathesis reagents to obtain materials with desired properties and reactivities. The versatility of this P+ transfer approach is exemplified by the reactions of these triphosphenium precursors with an N-heterocyclic carbene and an anionic bisphosphine, each of which readily displace the neutral bisphosphine to give an NHC-stabilized phosphorus(I) cation and a phosphorus(I) containing zwitterion, respectively.

Preparation and Reactivity of a Triphosphenium Bromide Salt: A Convenient and Stable Source of PhosphorusI

The synthesis of a triphosphenium bromide salt is described and its use as a P+ transfer agent is outlined by reactions with an N-heterocyclic carbene and an anionic bisphosphine, yielding an NHC-stabilized P(I) cation and a P(I) containing zwitterion, respectively.

We present herein the optimized synthesis of a triphosphenium bromide salt. Apart from being a versatile metathesis reagent, this unusually stable ...

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the inverse electron demand Diels-Alder (IEDDA) cycloaddition between a radiolabeled tetrazines and trans-cyclooctene (TCO) linked to a biomolecule has proven to be a highly effective bioorthogonal approach to imaging specific biological targets. Despite the fact that technetium-99m remains the most widely used isotope in diagnostic nuclear medicine, there is a scarcity of methods for preparing 99mTc-labeled tetrazines. Herein we report the preparation of a family of tridentate-chelate-tetrazine derivatives and their Tc(I) complexes. These hitherto unknown compounds were radiolabeled with 99mTc using a microwave-assisted method in 31% to 83% radiochemical yield. The products are stable in saline and PBS and react rapidly with TCO derivatives in vitro. Their in vivo pre-targeting abilities were demonstrated using a TCO-bisphosphonate (TCO-BP) derivative that localizes to regions of active bone metabolism or injury. In murine studies, the 99mTc-tetrazines showed high activity concentrations in knees and shoulder joints, which was not observed when experiments were performed in the absence of TCO-BP. The overall uptake in non-target organs and pharmacokinetics varied greatly depending on the nature of the linker and polarity of the chelate.

Preparation and Evaluation of 99mTc-labeled Tridentate Chelates for Pre-targeting Using Bioorthogonal Chemistry

Here, we describe a protocol for radiolabeling and in vivo testing of tridentate 99mTc(I) chelate-tetrazine derivatives for pre-targeting and bioorthogonal chemistry.

Pre-targeting combined with bioorthogonal chemistry is emerging as an effective way to create new radiopharmaceuticals. Of the methods available, the ...

Accessing Valuable Ligand Supports for Transition Metals: A Modified, Intermediate Scale Preparation of 1,2,3,4,5-Pentamethylcyclopentadiene

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that derive from initial 2-bromo-2-butene lithiation followed by acid mediated dienol cyclization. The revised synthesis and purification of the ligand avoids the use of mechanical stirring while still permitting access to significant quantities (39 g) of Cp*H in good yield (58%). The procedure offers other additional benefits, including a more controlled quench of excess lithium during the production of the intermediate heptadienols and a simplified isolation of Cp*H of sufficient purity for metallation with transition metals. The ligand was subsequently used to synthesize [Cp*MCl2]2 complexes of both iridium and ruthenium to demonstrate the utility of the Cp*H prepared and purified by our method. The procedure outlined herein affords substantial quantities of a ubiquitous ancillary ligand support used in organometallic chemistry while minimizing the need for specialized laboratory equipment, thus providing a simpler and more accessible entry point into the chemistry of 1,2,3,4,5-pentamethylcyclopentadiene.

Reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented. The revised protocol for the synthesis and purification of the ligand minimizes the need for specialized laboratory equipment while simplifying reaction workups and product purification. Use of Cp*H in the synthesis of [Cp*MCl2]2 complexes (M = Ru, Ir) is also described.

A reliable, intermediate scale preparation of 1,2,3,4,5-pentamethylcyclopentadiene (Cp*H) is presented, based on modifications of existing protocols that ...