Publications
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016 |
Pheromone Chemistry
![]() Chirality, 2018, online DOI: 10.1002/chir.22978 ![]()
Both enantiomers of petromyroxol are putative pheromones in sea lamprey (Petromyzon marinus). Here, we describe the separation and quantification of the petromyroxol enantiomers using high-performance liquid chromatography tandem mass spectrometry. The separation was tested on a wide range of chiral columns with normal phases, and effects of the chromatographic parameters such as mobile phase and temperature on the separation were optimized. The AD-H column showed the best separation of enantiomers with n-hexane and ethanol as the mobile phase. The enantiomers were detected by multiple reaction monitoring with a positive atmospheric-pressure chemical ionization on triple quadrupole mass spectrometer. Validation revealed that the method was specific, accurate, and precise. The validated method was applied to measure the amount of petromyroxol enantiomers in water conditioned with sea lamprey larvae, the source of the putative pheromone. This method will be applied in quantifying the natural scalemic petromyroxol mixture, enabling further investigations of a rare non-racemic enantiomeric pheromone mixture in a vertebrate species. |
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015 |
Total Synthesis: Oxonium Ylide Formation and Rearrangement of 1-Sulfonyl-1,2,3-Triazoles
![]() J. Org. Chem, 2015, 80, 4771–4775 DOI: 10.1021/acs.joc.5b00399 ![]()
Petromyroxol is a non-racemic mixture of enantiomeric oxylipids isolated from water conditioned with larval sea lamprey. The (+)-antipode exhibits interesting biological properties but only 1 mg was isolated from >100000 L of water. Recently, transition metal-catalyzed denitrogenation of 1-sulfonyl-1,2,3-triazoles has emerged as a powerful strategy for the synthesis of value-added products, including efficient diastereocontrolled construction of tetrahydrofurans. This methodology enabled the rapid development of the first synthesis of (+)-petromyroxol in 9 steps and 20% overall yield from a readily accessible starting material. |
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014 |
Brønsted Acid Catalysis: Cyclopropanation
![]() Angew. Chem. Int. Ed., 2015, 54, 5744–5747 DOI: 10.1002/anie.201500625 ![]()
Chloroacetic acid promotes an efficient and diastereoselective intramolecular cascade reaction of electron-deficient ynenones to deliver products featuring a 2,3,5-trisubstituted furan bearing a fused cyclopropyl substituent at the 5-position. Synthetically relevant polycyclic building blocks featuring various size rings and heteroatoms have been synthesized in high yield using this mild acid-catalysed reaction. |
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013 |
1-Sulfonyl-1,2,3-Triazoles: Oxonium Ylide Formation and Rearrangement
![]() Org. Lett., 2014, 16, 5878–5881 DOI: 10.1021/ol5028267 ![]()
Rhodium(II) acetate catalyzes the denitrogenative transformation of 4-substituted 1-sulfonyl-1,2,3-triazoles with pendent allyl and propargyl ethers and thioethers to onium ylides that undergo [2,3]-sigmatropic rearrangement to give 2-tetrasubstituted heterocycles with high yield and diastereoselectivity. |
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012 |
1-Sulfonyl-1,2,3-Triazoles: Oxonium Ylide Formation and Rearrangement
![]() Org. Lett., 2014, 16, 1660–1663 DOI: 10.1021/ol500309x ![]()
Rhodium(II) acetate catalyzes the denitrogenative transformation of 5-substituted and 4,5-disubstituted 1-sulfonyl-1,2,3-triazoles with pendent allyl and propargyl ether motifs to oxonium ylides that undergo [2,3]-sigmatropic rearrangement to give substituted dihydrofuran-3-imines in high yield and diastereoselectivity. |
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011 |
Organocatalysis: Sulfur Catalysis
![]() Angew. Chem. Int. Ed., 2012, 51, 12128–12131 DOI: 10.1002/anie.201207300 ![]()
Tetrahydrothiophene (THT) is an efficient organocatalyst for the synthesis of highly substituted furfuryl products from readily-accessible electron-poor enynes under neutral conditions. This process is demonstrated to be applicable to a wide-range of nucleophiles and enynes; and can be incorporated in a domino organocatalysis sequence. |
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010 |
Rhodium Catalysis: Domino Reactions
![]() Angew. Chem. Int. Ed., 2011, 50, 7346–7349 DOI: 10.1002/anie.201101773 ![]()
Once... twice... three times a catalyst! We demonstrate a novel triple domino rhodium(I)-catalysed asymmetric transformation of substituted oxabicyclic alkenes into bicycle[2.2.2]lactones. The reaction proceeds with good yields and excellent levels of stereoselectivity in each of the 16 examples studied. Mechanistic investigations suggest that this process proceeds by rhodium catalysed asymmetric ring opening, allylic alcohol isomerisation and oxidation. |
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009 |
Rhodium Catalysis: Regiodivergent Resolution
![]() Org. Lett., 2010, 12, 5418–5421 DOI: 10.1021/ol1022239 ![]()
Catalyst-controlled asymmetric ring opening of a racemic oxabicyclic alkene leads to two readily separable regioisomeric products both in excellent ee. A cationic Rh catalyst, with added NH4BF4 to modulate reactivity, was required to obtain synthetically useful yields. The utility of each substituted aminotetralin product has been demonstrated by their conversion to different biologically relevant molecules in a highly efficient and practical manner. |
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008 |
Rhodium Catalysis: Domino Reactions
![]() Tetrahedron, 2010, 66, 6468–6482 DOI: 10.1016/j.tet.2010.05.106 ![]()
Rhodium(I) catalysts promote the transformation of o-alkynyl phenols and anilines to the corresponding benzo[b]furans and indoles. The reaction is postulated to proceed via a transient 3-rhodium heterocycle intermediate, which can be trapped with suitable electrophiles to give poly-substituted heterocycles. In the case of mono-substituted electron-withdrawn electrophiles, excellent yield and selectivity for conjugate addition versus Heck/Mizoroki reaction can be achieved. In the case of 2-alkynyl pyridine electrophiles, novel 2-(benzofuran-3-yl)vinylpyridines are formed. |
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007 |
Total Synthesis: Azadirachtin
![]() Angew. Chem. Int. Ed., 2009, 48, 1317–1320 DOI: 10.1002/anie.200805395 ![]()
A second bite of the apple: A new and highly efficient synthesis of the propargylic mesylate fragment of azadirachtin has been accomplished. An enantioselective catalytic hetero Diels-Alder reaction sets up the stereocenter at C15, which then controls the installation of the remaining functionality in a total of only 17 steps. |
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006 |
Total Synthesis: Azadirachtin
![]() Angew. Chem. Int. Ed., 2008, 47, 9402–9429 DOI: 10.1002/anie.200802675 ![]()
Azadirachtin has been the subject of intensive research within the scientific community ever since its isolation from the neem tree in 1968. There are now over 1000 publications relating to this natural product which cover all aspects of structural, biological and synthetic studies. Herein, we describe the worldwide efforts towards the synthesis of this fascinating molecule. |
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005 |
Total Synthesis: Azadirachtin
![]() Chem. Eur. J., 2008, 14, 10683–10704 DOI: 10.1002/chem.200801103 ![]()
The final chapter! We describe in full the first synthesis of the potent insect antifeedant azadirachtin through a highly convergent approach. An O-alkylation reaction is used to unite decalin ketone and propargylic mesylate fragments, after which a Claisen rearrangement constructs the central C8-C14 bond in a stereoselective fashion. The allene which results from this sequence then enables a second critical carbon-carbon bond forming event whereby the [3.2.1] bicyclic system, present in the natural product, is generated via a 5-exo-radical cyclisation process. Finally, using knowledge gained through our early studies into the reactivity of the natural product, a series of carefully designed steps completes the synthesis of this challenging molecule. |
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004 |
Supercritical Carbon Dioxide
![]() Chem. Commun., 2008, 2152–2154 DOI: 10.1039/b801537f ![]()
The synthesis of a family of O-silylcarbamates from the corresponding silylamines has been achieved simply by heating the silylamine in supercritical carbon dioxide (scCO2), and these O-silylcarbamates have been shown to be effective precursors for the synthesis of a range of symmetrical and unsymmetrical ureas. |
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003 |
Total Synthesis: Azadirachtin
![]() Org. Lett., 2008, 10, 569–572 DOI: 10.1021/ol7027898 ![]()
The synthesis of five natural products isolated from the Indian neem tree Azadirachta indica, is reported from a common intermediate. The judicious choice of transacetalization conditions allows efficient access to both the azadirachtinin and the azadirachtin skeletons. |
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002 |
Total Synthesis: Azadirachtin
![]() Angew. Chem. Int. Ed., 2007, 46, 7633–7635 DOI: 10.1002/anie.200703028 ![]()
22 Years in the making: Azadirachtin was synthesized for the first time by a highly convergent approach, utilizing a Claisen rearrangement and a radical cyclization as key steps. End-game strategies relied on a relay-intermediate, which could be obtained by synthetic methods as well as by degradation of the natural product. |
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001 |
Total Synthesis: Azadirachtin
![]() Angew. Chem. Int. Ed., 2007, 46, 7629–7632 DOI: 10.1002/anie.200703027 ![]()
22 Years in the making: Azadirachtin was synthesized for the first time by a highly convergent approach, utilizing a Claisen rearrangement and a radical cyclization as key steps. End-game strategies relied on a relay-intermediate, which could be obtained by synthetic methods as well as by degradation of the natural product. |
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Non-refereed contributions: | ||
002 |
Organic Syntheses
![]() Org. Synth., 2011, 88, 152–161 DOI: 10.15227/orgsyn.088.0152 ![]() |
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001 |
Organic Syntheses
![]() Org. Synth., 2010, 87, 95–103 DOI: 10.15227/orgsyn.087.0095 ![]()
Benzyne is a highly reactive intermediate that has attracted wide attention from synthetic organic chemists. One of the commercially available precursors of benzyne is 2-(trimethylsilyl)phenyl trifluoromethanesulfonate which undergoes fluoride-promoted ortho-elimination to generate benzyne, mild conditions which tolerate a range of functional groups. Benzyne which is generated in this way has been shown to react with diazo compounds as 1,3-dipoles to afford substituted 1H-indazoles following a hydrogen shift. |
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