#Burgess reagent supplier

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What Role Does Burgess reagent Play?--APICDMO

Burgess reagent

Burgess reagent is a term used to describe Methyl N-(triethylammoniumsulphonyl) carbamate. It is a selective agent of mild strength used for dehydration in organic reactions and synthesis. Its main use is in the synthesis of alkenes using alcohols.

 It is also utilized to promote great synthetic values in medicinal chemistry. It has been used in the dehydration of primary amides, formamides, and primary nitroalkanes to generate nitriles, isocyanides, and nitrile oxides respectively. It forms urethanes when it reacts with primary alcohols.

 Burgess reagent was first discovered in 1968 by E.M. Burgess but it was only widely recognized when Peter Wipf used it extensively in different reactions.

 Features of Burgess reagent

♦ A particularly special characteristic of burgess reagent is how its dehydrating action is a pyrolytic reaction, that is it occurs only above 100°C.

♦ It is highly soluble in most organic solvents.

♦ Highly soluble even in nonpolar solvents formulated in the form of a salt.

♦ Dehydrating action of burgess reagent is syn-elimination.

 Uses of Burgess reagent

 Burgess reagent is used in many important transformations including the preparation of isocyanides, nitriles, and nitrile oxides. Of all its applications, the most important use of burgess reagent is the dehydration of thioamides and hydroxy amides to synthesize heterocycles.

 As dehydration with burgess reagent demands only mild conditions, it has been widely accepted in the synthesis of organic compounds.

 Mechanism of action of burgess reagent

 Burgess reagent is a variant of Ei mechanism, and this is the mechanism of action by which it works. This mechanism has been theorized based on the dehydration of threo and erythro-2-deuterio-1,2-diphenylethanol, which was originally studied by Burgess himself.

 The initial step, which comprises the formation of sulfamate ester, occurs in hydrocarbon solvents at or below 30° C through the reaction between the reagent and an alcohol.

After this compound is heated up with a microwave, pyrolysis occurs on the sufamate ester. The ionizing reaction of the carbon holding the main sulfamate group produces an ion pair. The collapse of this ion pair results in the transportation of hydrogen from the cation to the anion. This step is the rate-determining step.

 This process has a low energy level due to the contribution of positive entropy. Thereafter, the capture of proton becomes easier reducing all ion-pairing character and consequently the carbonium ion rearrangements.

 Applications of Burgess reagent

 ❶ Dehydration of alcohols

When alcohols need to be dehydrated, the primary factors that determine the reaction include the nature of the alcohol group, whether it is tertiary, secondary, or homoallylic, the configuration, as well as the environment. If tertiary or secondary alcohols are treated using a Burgess reagent within a solvent, the resulting olefins are approximately 90% in yields.

 ❷ Nitriles from primary amides

To synthesize nitriles, an easy process is via dehydration of primary amides. Commonly used reagents for this chemical process are often not suitable when other functional groups are present, and thus require further protection to prevent the synthesis of a completely different compound. However, burgess reagent works quite efficiently for this transformation.

 ❸ Isocyanides from formamides

Isocyanides are compounds that take part in a wide range of chemical reactions that involve synthetic transformations. Of all the methods available, the dehydration of formamides is the route that is most preferred. To this end, burgess reagent is an effective and safe agent that can be used to convert the compounds by altering their functional groups. Burgess reagent can convert formamides into isocyanides readily in large quantities. It is specially effective for all substrates that contain ether groups.

 ❹ Nitrile oxides from nitroalkanes

A particularly useful group of heterocylces are isoxazolines, which is formed from nitrile oxides by conversion of different alkenes. Generally, nitrile oxides are extremely reactive intermediate compounds which can itself undergo a transformation to produce isoxazoles or undergo dimerization to synthesize furoxanes. Two routes that are most commonly used for synthesizing nitrile oxides are dehydrogenation of aldoximes through hydroxamoyl halides or via dehydration of nitro compounds. The second method used to synthesize nitrile oxides using Burgess reagent is particularly useful as it is very easy to set up.

 ❺ Synthesis of heterocycles (Wipf cyclodehydration protocol)

Over the past few years, an increasingly common application of burgess reagent is in the cyclodehydration of hydroxy amides and thioamides. This leads to the production of corresponding heterocycles, which are essential synthetic intermediate compounds as they form an integral component of several biologically active natural products. Normally, the preparation of heterocycles is a complicated multistep process. But, with Burgess reagent, only a single step is essential for the cyclization of hydroxy amino acid in order to synthesize dihydrooxazoles using derivatives of serine and threonine derivatives.

 ❻ Other miscellaneous reactions

When Burgess reagent is used in different reactions, the end products are often unique and unexpected. But, such end products have often been found to be quite useful.

 【Reference】

 [1] Maki, T.; Tsuritani, T.; Yasukata, T. A Mild Method for the Synthesis of Carbamate-Protected Guanidines Using the Burgess Reagent. Org. Lett. 2014, 16 (7), 1868-1871.

[2] Mild, efficient dehydrating agent. Primary alcohols are converted to carbamates, which can be hydrolyzed to primary amines, thus providing a valuable alcohol to amine transformation. Secondary and tertiary alcohols afford olefins in synthetically useful yields: J. Org. Chem., 38, 26 (1973); Org. Synth. Coll., 6, 788 (1988). For further discussion, see: Encyclopedia of Reagents for Organic Synthesis, L. A. Paquette, Ed., Wiley, Chichester (1995), vol. 5, p. 3345.

[3] Sachin Khapli, Satyajit Dey & Dipakranjan Mal (2001). "Burgess reagent in organic synthesis" (PDF). J. Indian Inst. Sci. 81: 461–476. Archived from the original (PDF) on 2004-03-02.

[4] Edward M. Burgess; Harold R. Penton Jr. & E. A. Taylor (1973). "Thermal reactions of alkyl N-carbomethoxysulfamate esters". J. Org. Chem. 38 (1): 26–31. doi:10.1021/jo00941a006.

[5] Atkins, G. M.; Burgess, E. M. (1968). "The reactions of an N-sulfonylamine inner salt". J. Am. Chem. Soc. 90 (17): 4744–4745. doi:10.1021/ja01019a052.

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Team creates their own coronavirus test to fill gaps

A team has created their own coronavirus test to address shortages in testing capacity.

Scrolling Twitter late at night on March 12, Boston University’s George Murphy noticed a desperate tweet coming from the feed of his friend and fellow researcher, Lea Starita of the University of Washington. She was asking for lab-savvy volunteers to help process coronavirus tests that had been jury-rigged by the Seattle Flu Study.

“If you’re coming up with a test result that will lead to clinical decisions, it has to be right…”

As the two scientists began exchanging direct messages about what was happening in Seattle—the first US epicenter to emerge in the spread of the SARS-Cov-2 virus responsible for COVID-19 infections—Murphy, codirector of the Center for Regenerative Medicine (CReM) on Boston University’s Medical Campus, felt a dawning realization that the same fate would soon be upon the Greater Boston area and the university’s own teaching hospital, Boston Medical Center (BMC).

Across the nation, and the city of Boston, there would not be enough coronavirus tests from the Centers for Disease Control and Prevention (CDC) to go around. Researchers and clinicians would need to develop their own clinically validated tests to have a fighting chance.

“She was telling me her war story of having to do inhouse testing, navigating governmental restrictions,” Murphy says. “It got me thinking, maybe we should be thinking about trying to do something here.”

Center for Regenerative Medicine researchers Aditya Mithal, Claire Burgess, and Andrew McCracken prepare samples collected from Boston Medical Center patients suspected to be infected with the novel coronavirus. (Credit: Aditya Mithal/Boston U.)

‘Standing up’ a new coronavirus test

The next day, March 13, Murphy met with Chris Andry, chair of pathology at the School of Medicine and BMC.

“We hatched a plan to try and ‘stand up’ our own [coronavirus test],” Murphy says. Stand up, in the clinical world, describes the complex process to get a new diagnostic test validated and approved according to the stringent regulations of the US Food and Drug Administration. “If you’re coming up with a test result that will lead to clinical decisions, it has to be right,” he says.

Murphy and Andry’s meeting kicked off a week-plus-long flurry of around-the-clock activity, as CReM researchers—most of their own experiments already shuttered by social distancing efforts—volunteered in droves to design an inhouse COVID-19 test from scratch. They joined forces with a team of clinical lab technicians led by Nancy Miller, chief and vice chair of BMC laboratory medicine. They also leaned on the expert advice of fellow scientists at Massachusetts General Hospital, the Broad Institute of MIT and Harvard, and the University of Washington.

“My best friends are going to war.”

All told, more than 50 volunteers swarmed to the CReM from across the BU Medical Campus, working in shifts to ensure proper social distancing. By the week’s end, their teamwork culminated in a one-of-a-kind coronavirus test that can spit back a positive or negative result in less than 24 hours. The crew of collaborators is now processing many dozens of such tests each day—performing all of BMC’s COVID-19 testing—and making plans to even further ramp up capacity.

“We repurposed the whole CReM,” Murphy says of the state-of-the-art stem cell lab. Overnight, its researchers converted the facility into a makeshift command center and prototyping assembly line for coronavirus testing. Meanwhile, at BMC, patients began surging into the hospital with symptoms fitting the profile for the novel coronavirus. Clinicians faced agonizingly long delays waiting for patients’ COVID-19 test results, relying on state and commercial labs to validate swabs within five to seven days.

“It’s dangerous for healthcare workers if they are unaware someone they are treating has the coronavirus,” Murphy says. “That’s data that clinicians need to make decisions, to either quarantine patients or whether to use precious, dwindling supplies of [personal protective equipment] when they don’t need to. If we can [get a] result faster, that also protects our friends and loved ones from the CReM and around campus who are going into the clinic. My best friends are going to war.”

‘Heroic effort’

One of those friends includes the CReM’s director, Darrell Kotton, a stem cell biologist, Boston University School of Medicine professor of medicine, and a pulmonary/critical care physician at BMC. He reported into BMC’s intensive care unit on Wednesday, March 25, to serve as an attending physician alongside other doctors and physician-scientists from the BU Medical Campus community. There, he is doing everything he can to keep patients alive who have gone into respiratory failure from COVID-19 infection.

“…it’s been an exceptional and heroic effort—it’s made a big difference for the hospital, clearing a key early hurdle that faced us…”

“When the first patients were being admitted to BMC with COVID-19, we had a system meltdown in testing bandwidth,” Kotton says. “Tests being sent out that weren’t being turned around [quickly]. The hospital was getting bogged down. So I was thrilled when George’s team stepped in.”

He knew that since CReM researchers work with molecular reactions every day, Murphy’s team could help. “[Seeing them team up] with Chris, it’s been an exceptional and heroic effort—it’s made a big difference for the hospital, clearing a key early hurdle that faced us,” Kotton says.

To start, the collaborators filed what’s called an Emergency Use Authorization (EUA), an application released by the FDA that allows for research medical centers and commercial companies to develop their own inhouse COVID-19 tests and protocols for emergency FDA approval. Across the country, “everybody is trying to do it,” Murphy says. The idea is that you develop and “vet the diagnostic [test] in a research setting, and then move it up to clinical standards.”

Challenges and pitfalls

From the get-go, the team faced several choke points that threatened its ability to get an inhouse test off the ground. One of the first steps in testing for coronavirus is to use a reagent, called a viral RNA extraction kit, to break free the unique and identifying genetic strands of the SARS-Cov-2 virus from cells swabbed out of a patient’s nose or mouth mucosa.

Those unique SARS-Cov-2 RNA strands are what COVID-19 tests screen for; if they’re present, the patient is infected with the novel coronavirus. But viral RNA extraction kits weren’t available—suppliers were backordered for at least eight weeks, the team quickly found. So, they got scrappy. “We knew there were other reagents we could use,” Murphy says.

They knew that all across the BU Medical Campus, tons of labs had stockpiles of broad-use RNA extraction kits. RNA, which stands for ribonucleic acid, is essential to all organic life—it provides instructions for cellular machinery to manufacture the proteins that make up the structures of all cells, tissues, and organs. (Viruses don’t have cells of their own; instead they are made up of pieces of RNA encased in proteins. So, they rely on infecting animal and human cells to take advantage of their host’s cellular machinery, tricking them into reading the viral RNA instructions to build more copies of the virus—much to the host’s peril.) Studying RNA, therefore, is essential to understanding how humans stay healthy or develop disease. To do that, scientists need to isolate RNA from cells using a variety of standard RNA extraction kits.

“I don’t want to say the government failed, but there was a letdown in the kits being shipped to BMC…”

Murphy reached out, across the Charles River, to friend and fellow scientist Pardis Sabeti and her research team at the Broad Institute for their help working through the problem. “We were asking, ‘How would you do this with various reagents?’ We were working out the supply chain issues, identifying which reagents we were able to come by,” Murphy says.

Not only did they want to pick something that would work now, they also wanted a reagent they wouldn’t run out of in the coming weeks or months.

“We decided to go with using a very basic RNA extraction kit, we knew everyone would have it in their labs, so we plugged that into our EUA application,” Murphy says. The team put out the call to their colleagues across the BU Medical Campus, and kit donations came flooding in.

The problem with using a non-viral-specific kit, however, is that it liberates all the RNA within a cell, not just RNA from a virus. That muddies the waters, making it necessary to sift through lots of normally-occurring levels of human RNA, which keep our cells functioning properly, to find any amount of SARS-CoV-2 RNA. Just like any diagnostic test, a coronavirus test requires there to be a certain threshold of SARS-Cov-2 RNA to trigger a result. “You’ve got to be able to get enough viral RNA from a sample to amplify and detect it,” Murphy says.

Working around the clock

In the CReM, the team barely took breaks for sleep. Graduate students, faculty, postdoctoral researchers, staff technicians—it was all hands on deck. Richard Giadone, a BU graduate researcher days away from defending his PhD dissertation over Zoom, was there around the clock. “He was a critical part of the development team that created an FDA-approved COVID-19 test in one week,” Murphy says.

A CReM conference room became mission control, where researchers worked out new strategies to try optimizing the basic RNA extraction kit into a workable process for isolating SARS-Cov-2 RNA. On the table, coffee and snacks were strewn about, the team working so frantically they went without square meals for days. On the walls, whiteboards quickly filled with promising calculations and notes for troubleshooting each attempt. In the lab, researchers kept trying out each newly-conceived combination of techniques in hopes of developing a suitable protocol with the limited resources available.

“Our day job is to make stem cells, not diagnostics,” Murphy says. “It’s like we turned the CReM into a startup company to solve this problem. All the while, we’re working from separate rooms to maintain social distancing, never more than three people at a time in the same area.”

Within days, the team discovered that 150 microliters of RNA extraction solution, combined with other ingredients and several hands-on steps, generated enough viral RNA for detecting SARS-CoV-2.

“We made a brute-force RNA extraction process, we’re running the samples through spin columns, washing and pipetting samples into [PCR] plates,” Murphy says. PCR stands for polymerase chain reaction, a process that happens inside a lab machine—called a thermocycler—to make millions or billions of copies of genetic material. In this case, it multiplies the amount of viral RNA in a sample to a high-enough quantity that a test can detect SARS-CoV-2 from just a handful of a patient’s cells, originally captured by cotton swab.

A CReM bioinformatician, Taylor Matte, wrote a software script that allows the team to read off test data coming directly out of the thermocycler, allowing them to tentatively see a result before the sample gets sent up four floors to BMC pathology, where results are formally confirmed by clinicians.

“It takes a village,” Murphy says. “We started off with people from my own CReM group, but we knew immediately that we needed more people, so we started onboarding more help.” Behind the scenes, from the isolated safety of their homes, volunteers mobilized to recruit other researchers accustomed to running PCRs for their own experiments.

Molecular biologists from all over campus have stepped forward, getting cleared by BMC’s human resources department to work with clinical samples. “You can’t just show up and do it, you have to become a BMC-vetted employee,” Murphy says. “There are procedural things that need to happen to transform a basic scientific researcher into a clinical laboratory technician.”

Before they can work with real patient samples, BMC has to check their health history and make sure their vaccinations are up to date. Dozens upon dozens of these volunteers, once vetted, will staff the CReM around the clock so the inhouse COVID-19 tests keep pouring out results. All the while, just down the street, BMC clinicians will use those rapid-turnaround results to make decisions that could save lives.

“I don’t want to say the government failed, but there was a letdown in the kits being shipped to BMC,” Murphy says. “It’s science at its finest when collaborators get together to develop inhouse protocols, using their expertise, to directly impact patient care during a public health emergency.”

Most importantly, he says, in line with the CReM’s philosophy of doing “open source” biology and making its data available to all, the inhouse coronavirus test protocols developed by the team are now freely available to the worldwide scientific community.

Murphy says anyone interested in the protocols can reach out on Twitter: @DrGJMurphy.

Source: Boston University

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