10-Oxoisopiperitenone and 10-hydroxyisopiperitenone (for which the trivial names vesperal and vesperol are proposed) were identified using various EIMS (or MS-MS), CIMS data and GC-Fourier transform infrared obtained from the female-specific semiochemicals of the longhorn beetle Vesperus xatarti. Their structure was confirmed by synthesis via a Diels-Alder reaction and appropriate oxidation steps. The role of the female sex pheromone for vesperal was demonstrated. Comparison of the HPLC retention time of natural vesperal with those of synthesized pure enantiomers revealed that the natural compound has (S)-stereochemistry.
A 6-endo-trig cyclization was performed from enzymes 8 and 10 usingBu(3)SnH/AIBN, leading to the construction of the trans-decalinic AB ring system of (+/-)-forskolin 1. In a second radical approach to (+/-)-forskolin 1, the diol 31 was oxidized to dialdehyde 6. A pinacolic coupling reaction promoted by SmI2 then delivered the cyclized 6 beta,7 beta-diol 41. From this compound the unsaturated lactone 2 was then prepared leading to a formal synthesis of (+/-)-forskolin 1.
Different (omega-1)-functionalized phosphonium ylides 5 were obtained from commercially available 5-chloropentan-2-one 3 and but-3-yn-1-ol 4 in several steps. Some of the phosphonium ylides obtained were coupled using a Wittig reaction with a chiral epoxydienal 1 (prepared from (-)-2-deoxy-D-ribose 2 as starting material) to afford (omega-1)-functionalized leukotriene A(4) (LTA(4)) methyl ester analogues. The described strategy demonstrates a general and flexible approach to other leukotriene analogues stable to beta-oxidation, and/or molecular probes carrying reporter groups to characterize a potential LTC4 receptor.
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
sec-Butyllithium/(-)-sparteine mediated deprotonation, followed by reprotonation with various protonating agents, of the meso (E,E)-1,2,5-triphenylphospholane 1-oxide 2 affords the chiral (E,Z)-1,2,5-triphenylphospholane 1-oxide 4 with up to 45% ee. The results are best explained by a diastereoselective protonation of configurationally stable diastereomeric lithiated species.
Reference EPFL-ARTICLE-203053View record in Web of Science Record created on 2014-11-07, modified on 2017-11-27
The cobalt-catalyzed home Diels-Alder reaction of norbornadiene and terminal acetylenes yields chiral deltacyclenes. We tried to extend the scope of this reaction to acetylenes containing a heteroatom (i) in the propargylic position, (ii) in the ortho position of phenylacetylene or (iii) directly bonded to the triple bond. The synthesis of nine new substituted deltacyclenes with cobalt catalysts derived from CoI2 and zinc powder or Co(acac)(3) and Et2AlCl is described. Using Norphos as a cocatalyst, the products are obtained in high enantiomeric excess.
As a model for a synthetic approach to taxol and taxotere, the condensation of racemic alpha-alkoxy allylic stannane 9 with aldehydes 10a-h was examined. Under BF3 . OEt(2)-promoted reaction conditions, the syn-E 11a-h homoallylic alcohols were obtained as the major isomers. EtAlCl(2) was found to be an efficient promoter for the condensation of aldehyde 10e,f. With beta- or alpha-hydroxyaldehydes 10g or 10h in the presence of intramolecular chelated MgBr2, the stereochemical outcome of the reaction was inverted to give, in high yield and good stereoselectivity, the anti-E 11g,h homoaldol products exhibiting the stereochemistry required for the synthesis of taxanes.
Nous decrivons l'addition diastereoselective de reactifs organoceriques et organolithies sur des α-alcoxyhydrazones chirales. Le comportement de trois differents groupes alcoxy vis-a-vis de trois types de reactifs nucleophiles a ete examine. A une exception pres, les trois reactifs etudies ont conduit a des rendements eleves et a de hautes diastereoselectivites. L'auxiliaire chiral de type pyrrolidine a pu etre recupere par clivage hydrogenolytique (nickel de Raney) de la liaison N-N. Les β-aminoethers ainsi obtenus ont cependant subi une legere epimerisation.
The direct and quantitative preparation of monoorganotins 2, 3, 4 and 11 starting from Lappert's stannylene 1 represents a general access to a new class of organotin reagents. Their reactivity and versatility in the held of organic synthesis is highlighted. The influence of the substituents bound to the tin atom is shown for various reactions such as nucleophilic addition onto carbonyl compounds, radical transfer of functionalized allylic moieties and coupling reactions catalysed by transition metals.
Diels-Alder additions between anthracene and maleic anhydride or benzoquinone. Chemical and sonochemical catalysis. Diels-Alder cycloadditions of anthracene with either maleic anhydride or benzoquinone behave very differently under sonication or in the presence of monoelectronic oxidizers. The second cycloaddition is influenced by both physical and chemical catalysts. As a chemical catalyst, iron trichloride exhibits an efficiency at least equal to that of the classical Bauld reagent.
A comprehensive bibliography describes the current knowledge about the synthesis of diamond. The synthesis by explosives has been realized by a simple device allowing us to follow the thermal and light effects. Carbon yields (detonation soot) are from 32 to 36% by using TNT and hexolite. The presence of diamond, about 60%, in the soot, has been confirmed by X-ray diffraction. The synthesis by shock compression has been carried out by an original device. The X-ray results of the carbon products obtained from different carbon precursors (graphite, coal, carbon black) show the presence of nanodiamonds because of the high pressure applied by our device. The diamond yield is influenced by the particle size and the dispersion of black carbon. The obtained nanodiamonds have a structure of a diamond core with a graphitic shell. It seems that the graphitic shell observed systematically around the diamond particles are formed during the regraphitisation of diamonds when the pressure drops sharply and the temperature of the sample stays high. The copper powder, acting as a thermal buffer, makes it possible to stop the process before the total graphitisation. Finally our experience shows that we can obtain diamond with all the carbon materials on condition that adequate pressures and temperatures are applied. The synthesis process of diamond by shock seems reconstructive, which could correspond to the very first steps of the synthesis by high pressure and high temperature.
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
An improved synthesis for ferrocenyldichlorophosphane, FcPCl(2) (Fc = C5H4FeC5H5) is reported. The availability of this compound gives access to the other, previously unknown members of the homologous ferrocenyldihalophosphane series, FcPX(2) (X = F, Br, I). The latter are characterised by NMR and high-resolution mass spectroscopy. The class of ferrocenyldihalophosphanes is a valuable synthon for the generation of a large variety of ferrocenylphosphanes.
Study of the regioselectivity of addition of Grignard reagents onto imide ester 7 led to the expected phenyl derivative 12. By contrast, the methyl derivative 15 necessitated the use of a Mannich reaction onto the ketone 4. Finally, reaction of diethyl malonate with ketone 4 exhibited a dehydrogenation leading to a conjugate diester 19 and the expected diester 18.
The composition and equilibrium constants of magnesium(II), cobalt(II), nickel(II), copper(II), cadmium(II), lead(II) and iron(III) complexes with two bidentate catechol ligands : dopamine and adrenaline, were studied in aqueous solution, by using protometric and spectrophotometric techniques. Both of the ligands give similar species, with very close equilibrium constants. The coordination degree of the metal ion is not greater than two, with the stability order Cu(II) > Pb(II) > Ni(II) approximate to Co(II) approximate to Cd(II) > Mg(II). Iron(III) gives much more stable complexes with adrenaline, especially the Fe(H2L)(3+) species in acidic medium.
AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Pentacarbonyl(2-alkynylanilinocarbene) complexes of chromium undergo a novel intramolecular tandem alkyne insertion/carbene annulation sequence to give 9H-carbazoles and 11H-benzo[alpha]carbazoles in a one-pot reaction. The yields of the cyclization products depend on the substitution pattern both at the alkyne terminus and within the carbene carbon side chain. Generally, aryl carbene ligands react more cleanly than their vinyl analogues, and the yields increase in the order of phenyl, methoxyphenyl and mesityl substituents bound to the C drop C bond.
In this paper we report the synthesis of new ester intermediates possessing two tails R-F/R-H or R-F/R-F' and their conversion into anionic, non-ionic and dianionic surfactants.
