Ferenc Evanics

Euphosalicin, a new diterpene polyester with multidrug resistance reversing activity from Euphorbia salicifolia

Abstract A novel diterpene polyester, named euphosalicin ( 1 ), the first representative of a new class of bicyclic diterpenes, was isolated from the dichloromethane extract of the whole plant of Euphorbia salicifolia , together with one known ( 2 ) and two new jatrophane diterpenes ( 3 , 4 ). The new carbon skeleton is formally derived from the jatrophane framework by incorporation of a geminal methyl group in the ring system. Compound 1 was found to be more active than verapamil in reversing multidrug resistance in mouse lymphoma cells.

Synthesis and ring—Chain tautomerism of angularly substituted cycloalkane-fused tetrahydro-1,3-oxazines

Abstract Starting from 1-methyl-1-cyclopentene and -cyclohexene, regioisomeric 1,3-amino alcohols 6a,b and 7a,b were prepared by regio- and stereospecific reactions. When the amino alcohols were condensed with aromatic aldehydes, well-defined products 8–11 were obtained, which exist as three-component tautomeric mixtures in CDCl3 solution. When equation (1) was applied in all four sets 8–11, good linear correlations were obtained. For regioisomeric compounds, introduction of the methyl group in the bridgehead position resulted in reverse effects on the stability.

Speciation of AlIII in blood serum - The AlIII-citrate-phosphate ternary system

Time-dependent speciation studies have been carried out on the ternary AlIII−citrate (A)−phosphate (B) system in order to clarify the solution state of AlIII in blood serum. The potentiometric results indicate that ternary complexes predominate both in freshly prepared mixtures and at equilibrium. The ternary species AlAB and AlABH−1 and the binary species AlAH−1 and AlBH−1 are present at physiological pH. As the solution ages the amount of the trinuclear species [Al3(AH−1)3(OH)]4− increases at the expense of the mononuclear binary and ternary complexes. 31P NMR spectra measured at neutral pH provide corroborating evidence of the formation of the ternary complexes AlAB and AlABH−1 and binary species AlBH−1 and Al2BH−3 found potentiometrically. Time-dependent 1H NMR measurements show that monodentate phosphate can slowly displace citrate from the otherwise very stable structure of the trinuclear species [Al3(AH−1)3(OH)]4−. At blood serum concentrations [c(AlIII) = 3 μM], AlIII is mostly bound to citrate either in binary species or in the ternary species formed with phosphate. However, with increasing AlIII concentrations binding to phosphate becomes more important.

Onium-decavanadate ion-pair complexes as catalysts in the oxidation of hydrocarbons by O2

Abstract The catalysed oxidations of hydrocarbons were found to involve radicals and to be inhibited effectively by phenolic scavengers. The dependences of the activities of the catalysts on their concentrations are explained by the structural changes in the inverse micelles, from the first small spherical associates through an open-layered more active structure, which finally folds back by forming a hollow spherical closed structure, with a fall in the rate. The 51 V NMR spectral behaviour of the ion-pair catalysts and the colour changes in the solutions are discussed. The decavanadate structure is not destroyed entirely during the catalysed oxidation, in spite of the partial reduction of the V(V) centres and some structural deformations. The essential role of water and the influence of the products of oxidation by O 2 on the courses of the reactions are also discussed.

Ring-Chain tautomerism of 2-aryl-substituted imidazolidines

Abstract N-Methyl-, N-ethyl-, N-(n-propyl)-, N-(iso-propyl)- and N-phenyl-2-arylimidazolidines proved to be ring-chain tautomeric mixtures in CDCl3. The ratios of the open and ring forms in the tautomeric equilibria of these compounds is described by the equation log Kx = ϱσ + log KX−H, used earlier for the ring-chain equilibria of saturated 2-aryl-1,3-O,N-heterocycles. These are the first examples among 2-arylimidazolidines of ring-chain tautomeric processes characterized by a Hammett-type correlation.

Salicifoline and salicinolide, new diterpene polyesters from Euphorbia salicifolia

Abstract Two new diterpenes ( 1 and 2 ) were isolated from a dichloromethane extract of fresh, whole plants of Euphorbia salicifolia: salicifoline ( 1 ) is the first representative of a new type of tricyclic diterpenes involving a novel 5-8-8 fused ring system, and salicinolide ( 2 ) is a bishomoditerpene lactone based on the jatrophane skeleton. The carbon skeleton of 1 is formally derived from jatrophane via transannular intramolecular CC bond formation between C-12 and C-17.

Serrulatin A and B, New Diterpene Polyesters from Euphorbia serrulata

Abstract Two new diterpene polyesters, serrulatin A (1) and B (2), were isolated from an n-hexane extract of the whole, undried plant of Euphorbia serrulata. The structures were elucidated by various spectroscopic methods, including ESI-MS, IR, UV, 1D and 2D NMR techniques and X-ray crystallography. Serrulatin A contains a hitherto unknown heterocyclic ring system, while serrulatin B is a diterpene, which can be formally derived from 1 by ring opening.

FORMATION OF DIHYDROPEROXIDE DERIVATIVES DURING THE OXIDATION OF CYCLOHEXENE AND TETRALIN BY DIOXYGEN

Abstract1H- and13C-NMR investigations revealed that prolonged oxidation of unsubstituted cyclohexene and tetralin, containing symmetrical and weak allylic and benzylic CH bonds, results in the formation of both mono- and dihydroperoxo derivatives.

Cracking of neopentane over acidic zeolites: influence of isobutane and isobutene admission

Abstract Catalytic cracking of neopentane on acidic faujasites, mordenites and ZSM-5 zeolites was studied applying a batch reactor. The reaction proceeds with measurable rates above 523 K. Methane and isobutane are the primary products. The rate of methane formation is in good correlation with the A1 contents of ZSM-5 zeolites. Isobutane is the result of an intermolecular hydride transfer. The amount of initially added isobutene gradually decreases, while isobutane slightly increases the rate of reaction.