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Editorial
No full textCurt Wentrup was educated at the University of Copenhagen (Cand. Scient. 1966; D.Sc. 1976) and the Australian National University (Ph.D. 1969). He held an assistant professorship at the Universite de Lausanne, Switzerland, and a professorship at the Universitat Marburg, Germany, before returning to Australia in 1985 as professor of organic chemistry and head of the organic chemistry section at the University of Queensland, where he is now emeritus professor. Since 2009 he has been chair of the National Committee for Chemistry of the Australian Academy of Science. He is a Fellow of the Australian Academy of Science and has published over 300 publications. His research interests are in the fields of both experimental and computational chemistry of reactive intermediates and unusual molecules, flash vacuum thermolysis, and photochemistry, and he collaborates extensively with groups in Denmark, France, Germany, Singapore and Switzerland
The Australian Journal of Chemistry - Its New Publishing Concept
Full text linkCurt Wentrup was born in Denmark and educated at the University of Copenhagen (Cand. Scient. 1966 with Prof. K. A. Jensen; DSc 1976), and the Australian National University, Canberra (PhD 1969 with Prof. W. D. Crow). After postdoctoral work with Prof. H. Dahn at the Universite de Lausanne, Switzerland, and a junior faculty position at the same institution, he was appointed professor of organic chemistry at the Universit t Marburg (1976-85) before taking up the Chair of Organic Chemistry at The University of Queensland in 1985. In 2008 he was appointed Emeritus Professor at The University of Queensland. He is a Fellow of the Royal Australian Chemical Institute, was elected Fellow of the Australian Academy of Science in 2000, and received the Centenary Medal of the Australian Commonwealth in 2001. He serves or has served on the editorial or advisory boards of a number of journals and has been the organizer or co-organizer of numerous national and international conferences and symposia, including the well-known Heron Island Conferences on Reactive Intermediates and Unusual Molecules. He collaborates extensively with groups in Australia, Austria, Belgium, Denmark, France, Germany, Singapore, and Switzerland. His research interests are in the field of reactive intermediates, particularly nitrenes, carbenes, zwitterions, and ylides (R-: N:, R(2)C:, and R-CN(+)-X-) and cumulenes (ketenes, ketenimines, and iminopropadienonesRN=C=C=C=O). This research employs flash vacuum thermolysis (FVT), photochemistry, matrix isolation, and in recent years has included microwave-induced thermal chemistry as an alternative to FVT. This technique offers much potential for the application of reactive intermediates in organic synthesis
Interconversion of nitrenes, carbenes, and nitrile ylides by ring expansion, ring opening, ring contraction, and ring closure: 3-quinolylnitrene, 2-quinoxalylcarbene, and 3-quinolylcarbene
No full textPhotolysis of 3-azidoquinoline 6 in an Ar matrix generates 3-quinolylnitrene 7, which is characterized by its electron spin resonance (ESR), UV, and IR spectra in Ar matrices. Nitrene 7 undergoes ring opening to a nitrile ylide 19, also characterized by its UV and IR spectra. A subsequent 1,7-hydrogen shift in the ylide 19 affords 3-(2-isocyanophenyl)ketenimine 20. Matrix photolysis of 1,2,3-triazolo[1,5-c]quinoxaline 26 generates 4-diazomethylquinazoline 27, followed by 4-quinazolylcarbene 28, which is characterized by ESR and IR spectroscopy. Further photolysis of carbene 28 slowly generates ketenimine 20, thus suggesting that ylide 19 is formed initially. Flash vacuum thermolysis (FVT) of both 6 and 26 affords 3-cyanoindole 22 in high yield, thereby indicating that carbene 28 and nitrene 7 enter the same energy surface. Matrix photolysis of 3-quinolyldiazomethane 30 generates 3-quinolylcarbene 31, which on photolysis at >500 nm reacts with N to regenerate diazo compound 30. Photolysis of 30 in the presence of CO generates a ketene (34). 3-Quinolylcarbene 31 cyclizes on photolysis at >500 nm to 5-aza-2,3-benzobicyclo[4.1.0]hepta-2,4,7-triene 32. Both 31 and 32 are characterized by their IR and UV spectra. FVT of 30 yields a mixture of 2- and 3-cyanoindenes via a carbenecarbenenitrene rearrangement 31 → 2-quinolylcarbene 39 → 1-naphthylnitrene 43. The reaction mechanisms are supported by density functional theory calculations of the energies and spectra of all relevant ground and transition state structures at the B3LYP/631G*level
The absolute configurations of haliclonacyclamines A and B determined by X-ray crystallographic analysis
No full textX-Ray crystallography establishes that the marine alkaloids ()-haliclonacyclamine A 1 and (+)-haliclonacyclamine B 2 each have the configuration C2 (R), C3 (R), C7 (R), and C9 (R). The alkaloids appear to be enantiomerically pure; this provides an insight into the stereochemical consequences of the biosynthetic pathway leading to these bioactive 3-alkylpiperidine alkaloids
Base-sensitivity of arginine alpha-ketoamide inhibitors of serine proteases
No full textSerine protease enzymes use a serine hydroxyl group to catalyze hydrolysis of polypeptides. They are important in immunity, blood clotting, digestion, and as therapeutic or diagnostic targets for cancer, diabetes, stroke, inflammatory diseases, and viral infections. Their inhibitors typically possess an electrophile that reacts with the nucleophilic hydroxyl group of the catalytic serine. The α-ketoamide is a valuable electrophile in inhibitor discovery as it permits synthetic elaboration to both sides, unlike other electrophiles. Here we show that an α-ketoamide is unstable above pH 7 when adjacent to the C-terminus of arginine – the guanidine side chain condenses with the α-ketoamide at the keto group rather than the amide carbonyl to form a six-membered hemiaminal rather than a seven-membered lactam
Fluoroquinolones from imidoylketenes and iminopropadienones, R-N=C=C=C=O
No full text3-Fluoro-, 4-fluoro-, and 2,3,4-trifluorophenyliminopropadienones have been generated by flash vacuum thermolysis (FVT) of 5-[(fluoroarylamino)methoxymethylene]-2,2-dimethyldioxan-4,6-dione (Meldrum’s acid) derivatives. Their reaction with methanol affords interconverting imidoylketenes and oxoketenimines, which are employed in a synthesis of fluoroquinolones. The same quinolones are obtained from methyl 1-fluoroaryl-1,2,3-triazole-4-carboxylates, which on FVT eliminate N2 to generate oxoketenimines. Rearrangement of the oxoketenimines to imidoylketenes and cyclization afford the quinolones
Structure and activity of the leaf-specific cyclotide vhl-2
Full text linkCyclotides are plant-derived macrocyclic peptides with potential applications in the pharmaceutical and agricultural industries. In addition to their presumed natural function as host-defence peptides arising from their insecticidal activity, their other biological activities include antimicrobial, haemolytic, and cytotoxic activities, but at present, only limited information is available on the structural and chemical features that are important for these various activities. In the current study, we determined the three-dimensional structure of vhl-2, a leaf-specific cyclotide. Although the characteristic cyclic cystine knot fold of other cyclotides is maintained in vhl-2, it has more potent haemolytic activity than well-characterized cyclotides such as kalata B1 and kalata B8. Analysis of surface hydrophobicity and haemolytic activity for a range of cyclotides indicates a correlation between them, with increasing hydrophobicity resulting in increased haemolytic activity. This correlation is consistent with membrane binding being a vital step in mediating the various cytotoxic activities of cyclotides. The gene sequence for vhl-2 was determined and indicates that vhl-2 is processed from a multidomain precursor protein that also encodes the cyclotide cycloviolacin H3
Controlled dispersion polymerization in supercritical carbon dioxide
No full textRecent advances in controlled polymerization have led to increased activity in controlled free radical polymerization in unconventional solvents. This short report focuses on the renewed interest in dispersion polymerization in supercritical CO2 brought about by the application of controlled free radical polymerization techniques. The emergence of novel and industrially-applicable materials is discussed, as well as the dependence of material properties and morphology upon factors such as surfactant type and how it is employed during the polymerization
RAFT-Mediated Emulsion Polymerization of Styrene in Water using a Reactive Polymer Nanoreactor
No full textWe have demonstrated a nanoreactor methodology to produce polystyrene nanoparticles with narrow molecular weight distributions (MWD) and control over the final particle size distributions. Our reactive thermoresponsive diblock copolymer nanoreactor is an ideal setting to carry out otherwise difficult reversible addition-fragmentation chain transfer (RAFT)mediated polymerizations, resulting in surfactant-free nanoparticles that can be tuned to size and MWD. By confining the MacroRAFT agent within the nanoreactor, the poor P(DMA(68)-b-NIPAM(73))-SC(=S)SC4H9 (PNIPAM) leaving group on the MacroCTA behaves as a highly active MacroCTA through kinetic rather than thermodynamic control. The M-n was close to theory with low polydispersity indices (PDIs)
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