State of the rare earth elements tetapyrazinoporphyrazinate complexes in protic media

Russian Journal of General Chemistry - The acid-base interactions of tetrapyrazinoporphyrazine erbium(III) and lutetium(III) complexes in the media based on acetic and trifluoroacetic acids were...     

Nucleophilic thiylation of limonene 8,9-oxide

Thioterpenols of the menthane series have been obtained by reactions of limonene 8,9-oxide with thiols and with isothiuronium salts.S. V. Kurashov Kazan' State Medical University, 420012, Kazan', ul. Butlerov, 49, Korp. B Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 197–200, March–April, 1999.     

First example of Diels-Alder reaction in the 2,3,4,4a-tetrahydroquinoline series. Synthesis of hydrogenated 5,8-ethanoquinolines

Diels-Alder reactions in the 2,3,4,4a-tetrahydroquinolines series were studied for the first time. It was shown that these dienes demonstrate only moderate reactivity. [4+2] Cycloaddition occurs stereo- and regioselectively only for alkenes bearing an electron-withdrawing group (acrylonitrile, maleic anhydride, dimethyl acetylene dicarboxylate, methyl propiolate). In this case, endo-Diels-Alder adducts, spiroannelated 5,8-ethanoquinolines, are formed in a high yield. Cyclopentadiene, being a highly reactive diene component, reacts with 2,3,4,4a-tetrahydroquinolines as the dienophile. Electron-rich unsaturated compounds (N-vinylpyrrolidone, vinylethyl ether, phenylacetylene) are inert to this cycloaddition reaction.     

1-R-2-[(1E,3E)-4-Aminobuta-1,3-dien-1-yl]-1H-benzimidazoles. Synthesis and some transformations

7-Nitropyridobenzimidazolium salts are cleaved with secondary amines to form 2-[(E,E)-4-aminobuta-1,3-dienyl]-1H-benzimidazoles. The latter react with dimethyl acetylene-dicarboxylate to yield 4a-[(E,Z,E)-6-amino-4,5-dimethoxycarbonylhexa-1,3,5-trien-1-yl]-1,2,3,4-tetra(methoxycarbonyl)-4a,5-dihydropyrido[1,2-a]benzimidazoles.     

Lifetimes of Rydberg states in ions of the group II elements

Total probabilities A _nl of spontaneous radiative transitions, which determine lifetimes τ _nl = 1/A _nl of nS-, nP-, nD- and nF-states in singly charged ions of the group IIa (Be⁺, Mg⁺, Ca⁺, Sr⁺, Ba⁺) and IIb (Zn⁺, Cd⁺, Hg⁺) elements, were calculated in the single-electron Fues’ model potential (FMP) method. An asymptotic dependence is determined for highly excited states with small angular momentums and presented in the form τ _nl = τ _l ⁽⁰⁾ n ³ Q _l (1/n) and numerical values of the factors τ _l ⁽⁰⁾ and coefficients of the cubic polynomial Q _l (x) are calculated, which approximate results of numerical computations with relative error below 2% in the range of states with principal quantum numbers from n = 7 to n ≈ 2000. The comparison of the numerical results with data in literature is presented, and applicability and reliability of single-electron model calculations are discussed in detail for positive singly charged ions of the group II elements.     

Boronated protohaemins: synthesis and in vivo antitumour efficacy

The conjugates of porphyrin macrocycles with boron-containing polyhedra are under investigation as agents for binary treatment strategies of cancer. Aiming at the design of photoactive compounds with low-to-zero dark toxicity, we synthesized a series of carboranyl and monocarbon-carboranyl derivatives of protohaemin IX using the activation of porphyrin carboxylic groups with di-tert-butyl pyrocarbonate or pivaloyl chloride. The water-soluble 1,3,5,8-tetramethyl-2,4-divinyl-6(7)-[2'-(closo-monocarbon-carborane-1'-yl)methoxycarbonylethyl]-7(6)-(2'-carboxyethyl)porphyrin Fe(III) (compound 9) exerted no discernible cytotoxicity for cultured mammalian cells, nor did it cause general toxicity in rats. Importantly, 9 demonstrated dose-dependent activity as a phototoxin in photodynamic therapy of M-1 sarcoma-bearing rats. In animals injected with 20 mg kg(-1) of 9, the tumours shrank by day 3 after one single irradiation of the tumour with red laser light. Between 7 and 14 days post-irradiation, 88.9% of rats were tumour-free; no recurrence of the disease was detectable within at least 90 days. Protohaemin IX alone was without effect, indicating that boronation is important for the phototoxic activity of 9. This is the first study that presents the synthesis and preclinical in vivo efficacy of boronated derivatives of protohaemin as phototoxins. The applicability in photodynamic treatment broadens the therapeutic potential of boronated porphyrins beyond their conventional role as radiosensitizers in boron neutron capture therapy.     

Chemoselectivity of [4 + 2] cycloaddition in <Emphasis Type="Italic">N</Emphasis>-maleyl- and <Emphasis Type="Italic">N</Emphasis>-allyl-2,6-difurylpiperidin-4-ones

On the basis of a transition state conformation analysis, an attempt was made to explain the high chemoselectivity of intramolecular [4 + 2] cycloaddition in 3-alkyl-2,6-difuryl-N-maleylpiperidin-4-ones. It was shown that the thermal Diels–Alder reaction in these piperidine derivatives takes place through the “boat” conformation and leads to the formation of hydrogenated 1-alkyl-4-(2-furyl)-2H-8,10a-epoxy-pyrido[2,1-a]isoindol-2-ones. The alternative regioisomers, 3-alkyl-4-(2-furyl)-2H-8,10a-epoxy-pyrido[2,1-a]isoindol-2-ones, are hardly formed at all. At the same time, the intramolecular Diels–Alder reaction in the isostructural 3-alkyl-N-allyl-2,6-difurylpiperidin-4-ones, takes place non-regioselectively from the “chair” conformation.     

Synthesis of caranoids with two sulfide functions from 3-carene α- and β-sulfides

A convenient method has been developed for obtaining 3-carene α- and β-sulfides from which isomeric 4-RS-carane-3-thiols have been obtained by the nucelophilic addition of thiols under the conditions of base catalysis. The S-alkylation of the latter has formed the corresponding 4-RS-3-R'S-caranes. A high degree of regio- and stereoselectivity of the reactions studied has been found.