Kurt Torssell

An improved procedure for the preparation of 2-isoxazolines

Abstract Aldoximes were converted in high yields by N-Chlorosuccinimide into hydroxamic acid chlorides, and corresponding nitrile oxides generated by addition of triethylamine at 40°–50° underwent 1,3-dipolar polar addition to alkenes, giving 2-isoxazolines. The whole procedure could be performed as a one-pot reaction. Oximes with other functions, sensitive to free chlorine could be converted selectively into hydroxamic acid chlorides by this procedure. Isopropylidene glyceraldoxime was added to acrolein diethylacetal thus affording an entrance to carbohydrate synthesis but the stereospecificity of the reaction is low. 2:3, 5:6-Di-O-isopropylidene-D-mannose oxime was converted to the N-hydroximinolactone by treatment with NCS and base.

Investigation of radical intermediates in organic reactions by use of nitroso compounds as scavengers the nitroxide method

Abstract Hydrogen peroxide reactions with ketones were studied by the nitroxide method. Fragmentation of ketones proceeded via hydrogen peroxide adducts. Radical substitution took place with boranes and plumbanes. Postulated radicals from photolysis of certain ketones have been trapped. Photolysis of aryliodides in the presence of t -nitrosobutane gave aromatic nitroxide radicals, the spectra of which were analyzed. Oxidative decarboxylation of carboxylic acid with thallic acetate proceeded via radicals. The splitting of the trichloromethyl nitroxide radicals is discussed. Some relationship between hyperfine Splittings and structure has been observed.

Relationship between the properties of radical cations and the rate constants and the substitution patterns in electrophilic aromatic substitution

Abstract By a charge transfer mechanism for electrophilic aromatic substitution the logarithmic plot of overall rate constants for substitution against ionization potentials is correctly predicted. Also, orientation of substitution is found to be correlated with the hyperfine coupling constants of the aromatic radical cation. The presence of radical cations under the conditions of electrophilic substitution is discussed.

Silyl nitronates, nitrile oxides, and derived 2-isoxazolines in organic synthesis. Functionalization of butadiene, a novel route to furans and 2-isoxazolines as an alternative to aldol-type condensations

Abstract Mono- and di-addition of silylnitronates and nitrile oxides is a useful procedure for functionalizing butadiene leading to cyano and acyl derivatives. A novel route to 2,5-disubstituted furans is also established. The potential of the method in carbohydrate synthesis is pointed out. The route via 2-isoxazoline is shown to be a useful alternative to aldol-type reactions in organic synthesis. 15a has been studied by X-ray diffraction and shown to be the meso form.

Silyl nitronates in organic synthesis. Synthesis of 3(2H)-furanones

Abstract A synthesis of 3(2H)-furanones, a structural element of several natural products, has been developed in which silyl nitronates or nitrile oxides are condensed with vinyl ketones to form 5-acyl-2-isoxazolines which are reduced with titanous ions or catalytically to 1,4-diketo-2-ols and cyclized with sodium acetate in acetic acid.

Silyl nitronates and nitrile oxides in organic synthesis. A novel route to d,l-deoxysugars. Use of aluminum oxide as solid phase base for generation of

Abstract Novel methodology is developed for a three step synthesis of deoxyaldoses and deoxyketoses: 1. Regioselective addition of silyl nitronate or nitrile oxide to a diene. 2. Stereospecific hydroxylation of the double bond. 3. Unmasking of the aldol moiety by catalytic reduction of the 2-isoxazoline. The syntheses of D,L-deoxyribose, D,L-oleose, D,L-digitoxose, D,L-2-deoxygalactose, 1,3-dideoxyfructose, 3-deoxyfructose etc. are described. Basic aluminum oxide is introduced as a solid phase base for the one step synthesis of 2-isoxazolines from aldoximes and olefins. An X-ray diffraction study of compound 13c verifies the stereochemical assignments.

Addition of nitrile oxides to olefins. Synthesis of dihydrojasmone and starting material for prostanoids. A novel route to pyrroles

Abstract Routes to dihydrojasmone and γ-keto-aldehydes and an alternative procedure for a key intermediate in our prostaglandin synthesis are described. 2-Isoxazolines are useful intermediates for a preparation of a variety of classes of compounds. A novel route to pyrroles is established.

19F and 1H NMR and ESR investigations of aryl-t-butyl nitroxides and nitronylnitroxides

Abstract 1 H and 19 F NMR and ESR spectra of several nitroxides have been recorded. The 19 F couplings are sensitive to steric factors and this shows why the simple linear relationship a F = O eff F · ϱ C π is not adequate. The π and σ spin delocalization mechanisms are demonstrated. The spin transmission via oxygen and sulphur is affected by geometry (efficiency of pπ-nπ overlap), pπ-dπ overlap only plays a role in positively charged S atoms (sulphones). The absolute sign of the proton coupling in an alkyl chain depends upon chain length and substituents. The syntheses of several stable nitroxides are described.

Lignans and lactones from Phyllanthus anisolobus

Abstract The ichtyotoxic lignan justicidin B , ca 0.6% of the dry weight, and the lignan-glucoside phyllanthostatin A were isolated from the chloroform extract of Phyllanthus anisolobus . Two γ-lactones, menisdaurilide and aquilegiolide, were also isolated and their absolute stereostructures determined by the CD allylic benzoate method.

Triterpenes, lichexanthone and an acetylenic acid from Minquartia guianensis

Abstract Lichexanthone, 17-hydroxy,9,11,13,15-octadecatetraynoic acid and fatty acid esters (mixture) of erythrodiol (12-oleanene-3,28-diol, 3-β-form), and betulin (20-(29)-lupen-3,28-diol) were isolated. The structure of the new triterpene, 13,28-epoxy-3-acetoxy-11-oleanene, 3β,13β form, was determined by X-ray diffraction. The triterpenes occur mainly as C-3-O-palmitates.