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20 Mar 09:16

Luxury of N‐Tosylhydrazones in Transition‐Metal‐Free Transformations

by Dhanarajan Arunprasath, Balasubramanian Devi Bala, Govindasamy Sekar
Advanced Synthesis & Catalysis Luxury of N‐Tosylhydrazones in Transition‐Metal‐Free Transformations


Abstract

This review is focused on the recent developments in transition‐metal‐free transformations using N‐tosylhydrazones, emerging building blocks in contemporary organic chemistry. Emphasis is given to their synthetic potential, scope, mechanism and limitations. N‐Tosylhydrazones, derivatives of carbonyl compounds, can undergo a wide range of reactions under transition‐metal‐free reaction conditions. The chemical behaviour of tosylhydrazones is unique under different reaction conditions as they can act as diazo precursors, carbene sources, 1,3‐dipoles, ambiphilic reagents, one‐carbon synthons, and an alternative to the parent carbonyl compounds. These diverse reactivities have resulted in the development of novel C−C and C−heteroatom bond‐forming reactions. The potential of N‐tosylhydrazones in transition‐metal‐free reactions is evident from the synthesis of a handful of molecules such as cyclopropanes, di‐ and triarylmethanes, pyrazoles, triazoles, pyridazines, ethers, carbamates, thioacetals, thiadiazoles and many others.

19 Mar 15:33

[ASAP] Strain-Release-Driven Homologation of Boronic Esters: Application to the Modular Synthesis of Azetidines

by Alexander Fawcett, Amna Murtaza, Charlotte H. U. Gregson, Varinder K. Aggarwal
Kirsty Milne

Autotaxin core synthesis?

TOC Graphic

Journal of the American Chemical Society
DOI: 10.1021/jacs.9b01513
06 Feb 18:02

2018 Drug Approvals: A Closer Look

by Derek Lowe
Kirsty Milne

problem sessions??

Let’s have a look at the recent new drug approvals. 2018 was quite a year, by the numbers. C&E News has a comprehensive roundup: 59 approvals (versus 46 in 2017, which was already a record by itself), and about two-thirds of those small molecules. There are some very interesting molecules in the list, and I always recommend that medicinal chemists sit down every so often and look over the structures of approved drugs as if you’re seeing them for the first time (say, as screening hits). You might be surprised at how many of them you find chemically somewhat unappealing – would you aim for an n-hexyl ether in your final structure (Mulpleta/lusutrombopag), the heterocyclic ring in the lower section of Xofluza (baloxivir marboxil), or think that 3,4-diaminopyridine (Firdapse) or Diacomet (stiripentol) could be drugs at all?

Those last two also illustrate the tricky nature of drug approval statistics. Diaminopyridine has been kicking around as a therapy since at least the early 1980s, and stiripentol was discovered in 1978. They each have taken very winding paths to final US approval. There’s also Galafold (migalastat), which was isolated in 1988 and given orphan drug status by the FDA for Fabry’s disease back in 2004, finally approved this year. As an extreme example, you have Aemcolo, which is rifamycin (discovered in the Eisenhower administration), approved this year for traveler’s diarrhea. These all can be contrasted with Vitrakvi (larotrectinib), which is a new kinase inhibitor (TRK fusion proteins) that went from first-in-man to FDA approval in under four years (blazing speed, if you’re not in the business and wondering about that) and Onpattro (patisiran) which is the first RNA-interference-based drug to be approved anywhere at all (an impressive scientific achievement). So that 59 number is rather heterogeneous, as all year-by-year approval numbers are.

Interestingly, over half of those 59 (34 approvals) were for rare diseases, which is the natural outcome of the way things have been going in the industry for some years now. Not everyone is happy about that – C&E News quotes Peter Bach of Sloan-Kettering referring to these as “amazing science one-offs”, which is pretty accurate, and noting that each of them treat only a very small number of people (albeit people who in most cases had no treatments at all before these drugs were developed). So you have people who are being helped tremendously, on the one hand (although at great expense), but not that big an impact on overall public health, on the other. If you ranked drug approval years by number of patients affected, I don’t think 2018 would look as impressive.

And that leads to the next thing to think about: are recently approving drugs earning back the expense that went into making them? The first thought is “Well, they’d better”, and that ain’t wrong. IDEA Pharma has its annual roundup of innovation in the industry out, and they also have some thoughts about the finances involved. If you look at 2013-2017, their top-ten innovative companies still only average about one approval a year (while the bottom ten average about one approval every four years!). Interestingly, adding up R&D expenses over that time, both groups spend about $6 billion dollars per approval. And yes, those R&D figures have various amounts of SG&A (selling, general, and administrative expenses) rolled into them, but it’s money spent either way that has to be earned back. Is it?

Apparently not. There were 217 drug approved over that time span, and so far only 6 of them have reached cumulative sales of $6 billion or more. Note, that’s just sales – not profits. And it’s very much a power-law-looking distribution, with Gilead’s Harvoni and Solvadi raking in huge profits and most everyone else tailing off pretty quickly. Only 48 of the 217 have even added up to one billion in sales over this period. Mike Rea of IDEA sums it up this way:

So, we have a problem. Not only do most of the drugs we put into pipelines not make it to market, those that do are not even paying for their own R&D programmes, never mind the R&D for the failures around them.

Companies can talk about ‘innovation’ all they want, but this is an unsustainable state. Launching medicines that stand a chance of repaying their own investment has to be the measure of success, of productivity. The commercial environment is a whole lot easier to predict than the biology of the human. (Or, should be.)

Now, it’s worth remembering that consulting firms have an interest in making things appear dire, because their business is coming in to fix your horrible problems. But even if you turn those figures down quite a bit, they’re still unsettling. These drugs have many more years on the market, for one thing, but balancing that out is that they’re likely to show declining sales over the longer term. Not everyone spent that $6 billion per approval, either – the smaller companies probably didn’t, but balancing that out is that they’re generally bringing out drugs with smaller sales. And so on.

It does make you think. How much of the investment money flowing into biopharma over the last few years been coming from people who hope that they’re buying into the next Gilead? The VCs and other early-stage investors are (for the most part) smarter than that, but you do wonder about the investors in the publicly traded companies. In the end, very few companies and very few drugs are going to hit like that. Maybe none.

 

07 Dec 09:28

Nucleophilic reactivities of Schiff base derivatives of amino acids

Kirsty Milne

might be useful Meghan

Publication date: 25 January 2019

Source: Tetrahedron, Volume 75, Issue 4

Author(s): Daria S. Timofeeva, Armin R. Ofial, Herbert Mayr

Abstract

Treatment of α-imino esters derived from glycine esters and benzophenone or benzaldehydes with potassium tert butoxide in DMSO gave persistent solutions of carbanions at 20 °C. The kinetics of their reactions with quinone methides and benzylidene malonates (reference electrophiles) have been followed photometrically under pseudo-first order conditions. The reactions followed second-order rate laws. Since addition of 18-crown-6 ether did not affect the reaction rates, the measured rate constants correspond to the reactions of the non-paired carbanions. Plots of the second-order rate constants against the electrophilicity parameters E of the electrophiles are linear, which allowed us to derive the nucleophile-specific parameters N and sN, according to the linear Gibbs energy relationship lg k2(20 °C) = sN(N + E). The Ph2C = N- and PhCH = N- groups act as very weak electron acceptors with the consequence that Ph2C = N-CH-CO2R and PhCH = N-CH-CO2R have a similar nucleophilicity as Ph-CH-CO2Et, the anion of ethyl phenylacetate.

Graphical abstract

Image 1

27 Sep 08:38

A convenient cyclopropanation process of oxindoles via bromoethylsulfonium salt

Publication date: 22 November 2018

Source: Tetrahedron, Volume 74, Issue 47

Author(s): Hui Qin, Yuanyuan Miao, Ke Zhang, Jian Xu, Haopeng Sun, Wenyuan Liu, Feng Feng, Wei Qu

Abstract

A practical convenient conversion of oxindoles into the corresponding spirocyclopropyl oxindoles is achieved efficiently using bromoethylsulfonium salt, which is easily prepared on a large scale and is stable crystalline. This reaction of bromoethylsulfonium salt with different substituted unprotected oxindoles proceeded under mild condition and provided moderate yields.

Graphical abstract

Image 1

18 Sep 10:53

[ASAP] Discovery of (S)-3-(3-(3,5-Dimethyl-1H-pyrazol-1-yl)phenyl)-4-((R)-3-(2-(5,6,7,8-tetrahydro-1,8-naphthyridin-2-yl)ethyl)pyrrolidin-1-yl)butanoic Acid, a Nonpeptidic avß6 Integrin Inhibitor for the Inhaled Treatment of Idiopathic Pulmonary Fibrosis

by Panayiotis A. Procopiou, Niall A. Anderson, John Barrett, Tim N. Barrett, Matthew H. J. Crawford, Brendan J. Fallon, Ashley P. Hancock, Joelle Le, Seble Lemma, Richard P. Marshall, Josie Morrell, John M. Pritchard, James E. Rowedder, Paula Saklatvala, Robert J. Slack, Steven L. Sollis, Colin J. Suckling, Lee R. Thorp, Giovanni Vitulli, Simon J. F. Macdonald

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Journal of Medicinal Chemistry
DOI: 10.1021/acs.jmedchem.8b00959
21 Aug 14:09

[ASAP] Synthesis and Activity of a Novel Autotaxin Inhibitor–Icodextrin Conjugate

by Natalie Fisher, Michael G. Edwards, Ryan Hemming, Steven M. Allin, John D. Wallis, Philip C. Bulman Page, Michael J. Mckenzie, Stefanie M Jones, Mark R. J. Elsegood, John King-Underwood, Alan Richardson

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Journal of Medicinal Chemistry
DOI: 10.1021/acs.jmedchem.8b00935
01 Aug 16:35

[ASAP] N–N Bond Formation between Primary Amines and Nitrosos: Direct Synthesis of 2-Substituted Indazolones with Mechanistic Insights

by Jie S. Zhu, Niklas Kraemer, Marina E. Shatskikh, Clarabella J. Li, Jung-Ho Son, Makhluf J. Haddadin, Dean J. Tantillo, Mark J. Kurth

TOC Graphic

Organic Letters
DOI: 10.1021/acs.orglett.8b01655
31 Jul 14:46

[ASAP] Atom Efficient Synthesis of Selectively Difluorinated Carbocycles through a Gold(I)-Catalyzed Cyclization

by Adam W. McCarter, Magdalena Sommer, Jonathan M. Percy, Craig Jamieson, Alan R. Kennedy, David J. Hirst

TOC Graphic

The Journal of Organic Chemistry
DOI: 10.1021/acs.joc.8b01121
25 Jul 16:30

Development of autotaxin inhibitors: A series of zinc binding triazoles

Publication date: 15 July 2018

Source: Bioorganic & Medicinal Chemistry Letters, Volume 28, Issue 13

Author(s): Christopher G. Thomson, Darren Le Grand, Mark Dowling, Cara E. Brocklehurst, Colin Chinn, Lucy Elphick, Michael Faller, Mark Freeman, Vikki Furminger, Cornelia Gasser, Ahmed Hamadi, Elizabeth Hardaker, Victoria Head, Johan C. Hill, Diana I. Janus, David Pearce, Anne-Sophie Poulaud, Emily Stanley, Lilya Sviridenko

Abstract

A series of inhibitors of Autotaxin (ATX) has been developed using the binding mode of known inhibitor, PF-8380, as a template. Replacement of the benzoxazolone with a triazole zinc-binding motif reduced crystallinity and improved solubility relative to PF-8380. Modification of the linker region removed hERG activity and led to compound 12 – a selective, high affinity, orally-bioavailable inhibitor of ATX. Compound 12 concentration-dependently inhibits autotaxin and formation of LPA in vivo, as shown in pharmacokinetic-pharmacodynamic experiments.

Graphical abstract

Graphical abstract for this article

06 Apr 07:59

[ASAP] Systematic Evaluation of 2-Arylazocarboxylates and 2-Arylazocarboxamides as Mitsunobu Reagents

by Daisuke Hirose, Martin Gazvoda, Janez Košmrlj, Tsuyoshi Taniguchi

TOC Graphic

The Journal of Organic Chemistry
DOI: 10.1021/acs.joc.8b00486
16 Mar 17:25

Scalable total synthesis and comprehensive structure–activity relationship studies of the phytotoxin coronatine

by Mairi M. Littleson

Scalable total synthesis and comprehensive structure–activity relationship studies of the phytotoxin coronatine

Scalable total synthesis and comprehensive structure–activity relationship studies of the phytotoxin coronatine, Published online: 16 March 2018; doi:10.1038/s41467-018-03443-1

Development of comprehensive structure–activity relationships for coronatine has been a major goal in the agrochemical industry. Here, the authors report the gram-scale production and structure–activity relationship of parent coronafacic acid and ultimately rationalise the biological activity of analogues of this phytotoxin.
21 Nov 08:48

Discovery of BI-2545: A Novel Autotaxin Inhibitor That Significantly Reduces LPA Levels in Vivo

by Christian A. Kuttruff, Marco Ferrara, Tom Bretschneider, Stefan Hoerer, Sandra Handschuh, Bernd Nosse, Helmut Romig, Paul Nicklin and Gerald J. Roth
Kirsty Milne

Might be useful Jen

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ACS Medicinal Chemistry Letters
DOI: 10.1021/acsmedchemlett.7b00312
01 Nov 18:16

Song of Experience

by Derek Lowe
Kirsty Milne

might come in useful at some point?

I noticed this paper when it came out, and filed it in my “Useful Lab Tricks” folder. Organic chemists who have used triphenylphosphine-driven reactions will want to do so, too. For the non-chemists in the crowd, triphenylphosphine (TPP) is a cheap, crystalline substance that is pretty easy to oxidize to triphenylphosphine oxide (TPPO), a noticeably lower-energy species. There are a number of reactions that take advantage of those thermodynamics, setting things up so that the TPP-to-TPPO reaction is part of the mechanism and letting that drive the whole thing forward. It’s not exactly the most atom-efficient way to go, but it gets the job done at the bench. (Process chemists will make a little mark next to your name if you suggest doing this on scale, though, so be warned).

The oxide is an even more crystalline compound, but there are problems. It’s soluble to some extent in a number of common organic solvents, and there tends to be a lot of it around in a reaction that’s using triphenylphosphine in this fashion. The classic Wittig reaction throws off a lot of triphenylphosphine oxide, as does the Mitsunobu reaction, and you can end up trying to purify your product out of a big mound of white stuff. Sometimes it’s straightforward, and sometimes it’s a real pain. It can form very nice crystalline complexes with other organic molecules, which can help you out if you want to grow those, but you can lose material that way if you don’t.

What this new paper has found is a straightforward way of causing all the TPPO to fall out as an even more definitively insoluble mass. Treatment with zinc chloride apparently forms a complex between the two that crashes out of most everything, and I can tell you that I’ve had a few occasions where that knowledge would have come in pretty handy. I wondered at the time how this was discovered, but then I came across this story (courtesy of Chemjobber on Twitter).

The inventor of this trick is 85-year-old Donald Batesky, who used to work at Kodak back in the 1960s doing custom synthesis for non-catalog orders, work that will expose you to a lot of different kinds of chemistry, for sure. After Kodak, he worked for Aldrich (along with some other ex-Kodak chemists) doing contract synthesis for them in rented lab space in Rochester. So it’s safe to say he knows his way around a synthetic lab; by this point he’s seen it all. And now he’s on his third lab career at the University of Rochester, helping out as an assistant in the chemistry department. That’s where he remembered some metal-complex work from back when and hit on the zinc chloride idea.

Long experience at the bench, if you’re any good at all, gives you a fund of knowledge that’s hard to pick up from the literature. What solvents to try first for a crystallization, what reactions have exothermic inductions that you have to watch out for, which reducing agents have the easiest workups, how to get rid of metal contamination in the final product, when to deoxygenate rigorously and when not to worry about it so much, ways to get rid of Common Byproduct X or Pesky Solvent Y. Donald Batesky has just contributed another one of those to the trade, and good for him. This guy is clearly a chemist (he’s already stipulated that he wants to be buried in a lab coat), and I would very much enjoy sitting down and talking with him. It’s always worthwhile to listen to people who are really good at their work or to watch them do it, and I’m glad to hear that he’s still sharing his knowledge with his co-workers at Rochester.

03 Oct 14:56

Oxidative Synthesis of Benzimidazoles, Quinoxalines, and Benzoxazoles from Primary Amines by ortho-Quinone Catalysis

by Ruipu Zhang, Yan Qin, Long Zhang and Sanzhong Luo
Kirsty Milne

Jen - might be useful

TOC Graphic

Organic Letters
DOI: 10.1021/acs.orglett.7b02786
02 Oct 16:31

Direct Synthesis of Benzimidazoles by Dehydrogenative Coupling of Aromatic Diamines and Alcohols Catalyzed by Cobalt

by Prosenjit Daw, Yehoshoa Ben-David and David Milstein
Kirsty Milne

Jen - might be useful for zinc binding groups?

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ACS Catalysis
DOI: 10.1021/acscatal.7b02777
16 Jun 14:49

Tubular clathrin/AP-2 lattices pinch collagen fibers to support 3D cell migration

by Elkhatib, N., Bresteau, E., Baschieri, F., Rioja, A. L., van Niel, G., Vassilopoulos, S., Montagnac, G.

Migrating cells often use focal adhesions in order to move. Focal adhesions are less prominent in cells migrating in three-dimensional (3D) as compared with 2D environments. We looked for alternative adhesion structures supporting cell migration. We analyzed the dynamics of clathrin-coated pits in cells migrating in a 3D environment of collagen fibers. Both topological cues and local engagement of integrins triggered the accumulation of clathrin-coated structures on fibers. Clathrin/adaptor protein 2 (AP-2) lattices pinched collagen fibers by adopting a tube-like morphology and regulated adhesion to fibers in an endocytosis-independent manner. During migration, tubular clathrin/AP-2 lattices stabilized cellular protrusions by providing anchoring points to collagen fibers. Thus, tubular clathrin/AP-2 lattices promote cell adhesion that, in coordination with focal adhesions, supports cell migration in 3D.

02 May 07:55

Discovery of 2-[[2-Ethyl-6-[4-[2-(3-hydroxyazetidin-1-yl)-2-oxoethyl]piperazin-1-yl]-8-methylimidazo[1,2-a]pyridin-3-yl]methylamino]-4-(4-fluorophenyl)thiazole-5-carbonitrile (GLPG1690), a First-in-Class Autotaxin Inhibitor Undergoing Clinical Evaluation for the Treatment of Idiopathic Pulmonary Fibrosis

by Nicolas Desroy, Christopher Housseman, Xavier Bock, Agnès Joncour, Natacha Bienvenu, Laëtitia Cherel, Virginie Labeguere, Emilie Rondet, Christophe Peixoto, Jean-Marie Grassot, Olivier Picolet, Denis Annoot, Nicolas Triballeau, Alain Monjardet, Emanuelle Wakselman, Veronique Roncoroni, Sandrine Le Tallec, Roland Blanque, Celine Cottereaux, Nele Vandervoort, Thierry Christophe, Patrick Mollat, Marieke Lamers, Marielle Auberval, Boska Hrvacic, Jovica Ralic, Line Oste, Ellen van der Aar, Reginald Brys and Bertrand Heckmann
Kirsty Milne

might be useful Jen

TOC Graphic

Journal of Medicinal Chemistry
DOI: 10.1021/acs.jmedchem.7b00032