3'-nitrophenylpropyloxycarbonyl (NPPOC) protecting groups for high-fidelity automated 5' --> 3' photochemical DNA synthesis

[structure: see text]. The most powerful DNA microarrays would be prepared by photolithography with free 3'-ends that could be processed enzymatically. A photoremovable group that could be removed in quantitative yield would ensure high purity of the synthesized probes. We have developed new pyrimidine building blocks for 5' --> 3' DNA synthesis with high cycle yields using the NPPOC (3'-nitrophenylpropyloxycarbonyl) protecting group. These phosphoramidites were proved in automated photochemical DNA synthesis on a modified synthesizer.     

Preparation of alkyl-containing derivatives of chitosan and its oligomers in polymer-analogous reactions

It has been shown that the interaction of chitosan and oligochitosan with unsaturated acrylic esters via the nucleophilic addition mechanism and their condensation with heptadecyl isocyanate yield hydrophobic alkyl-containing derivatives of the above polymers. The method of modification of oligochitosan in reactions via end functional groups is developed.     

The nature of clay volatiles and condensates and the effect on their environment

When clays are heated, a mass loss occurs due to the evolution of volatiles. Most of these are water vapour, but in addition minor amounts of a complex assemblage of other species are liberated. The corresponding condensates are colloidal suspensions. The composition of the volatiles and condensates and the release patterns of the gases are reviewed. The nature of the assemblages varies from one clay to another and depends on the thermal regime. Both volatiles and condensates are very reactive. Their reactivity persists even after prolonged storage. They act as acid catalysts in reactions with organic matter and decompose calcite and other carbonates. Condensates were found to etch the surfaces of quartz crystals and to dealuminate and partly destroy an Al-rich faujasite (zeolite). Possible implications of reactions of clay volatiles and condensates for natural processes are discussed.     

Chromatographic studies of corrosion sites in metallic materials

Many types of corrosion phenomena are controlled by the ionic composition of a small volume of solution at the surface. Localized corrosion and atmospheric corrosion are two examples in which < 1 μl of solution can cause dramatic damage. Ion chromatographic (IC) techniques have been used to analyze these solutions in order to gain a better understanding of the mechanisms which govern them. Two examples are presented. The presence of minor alloying elements at localized corrosion sites in two aluminum alloys has been demonstrated, indicating non-stoichiometric dissolution of the alloy during localized corrosion. In addition, IC analysis allowed the determination of the species responsible for the atmospheric corrosion failure of electrical connectors, including their likely origin.     

Isolation and separation of transplutonium and rare-earth elements in unusual oxidation states on ion exchangers in inorganic acid solutions

The behaviour of transplutonium and rare-earth elements on anion and cation exchangers in solutions of H₃PO₄ and H₂SO₄ in the presence of oxidants (KBrO₃, PbO₂, (NH₄)₂S₂O₈) and in HCl solutions in the presence of reducing agents [Zn(Hg), Eu²⁺] depending on acid concentration as well as on oxidant content and nature in solution or in resin and other factors has been studied. Effective methods of Bk(IV), Ce(IV), Am(VI), Eu(II) and Md(II) separation from trivalent TPE and REE, as well as continuous methods of isolation of isotopically pure radionuclides²⁵⁰Bk,¹⁴⁴Pr by using ion exchangers and inorganic acid solutions have been developed.     

Luminescence of the pyrene/N,N-diethylaniline triplet exciplex in methanol at room temperature

Fluorescence, whose spectral and magnetic properties permit its assignment to the luminescence of a triplex exciplex, has been discovered at times 3 sec after photoexcitation in the luminescence spectrum of the pyrene+N,N-diethylaniline system in methanol at 600 nm by the method of nanosecond stroboscopic fluorometry.Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 25, No. 5, pp. 623–626, September–October, 1989.     

Further applications of endocyclic enamine-enone annulations : The total syntheses of rac-Sceletium alkaloid A4 and 3'-demethoxy sceletium alkaloid A4

The total synthesis of rac-sceletium alkaloid A₄1a and of its 3'-demethoxy analogue 1b via the annulation of endocyclic enamines 4a–b is presented. The Michael acceptor 5a is a useful synthon for the two-step synthesis of 2,3-disubstituted pyridines from Δ²-pyrrolines.     

Mass spectrometry of π-complexes of transition metals. Communication 32. Derivatives of π-cyclopentadienyl-π-(3)-1,2-dicarbollyliron(III)

Conclusions The basic paths have been established in the fragmentation of derivatives of -cyclopentadienyl--(3)-1,2-dicarbollyliron(III) under electron impact: cleavage of the carbollyl-Fe bond, deep dehydrogenation, dehydration, and dehydrohalogenation. The carbollyl complexes are less stable to electron impact thatn are the ferrocene derivatives. In the molecular ions, the Cp-Fe bond is stronger than the carbollyl-Fe bond.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2246–2251, October, 1984.     

Substituted chromans and tetrahydrofuro[2,3-b]benzofurans (trapped tetrahedral intermediates) from 3-phenyl-2-benzofuranones

The previously discovered neighboring group reaction has been extended to the synthesis of chroman derivatives (i.e., 4, 5, 6) containing geminal methyls in the 2-position, a feature common to certain physiologically active natural chromans. In two instances, cyclic ortho ester by-products (8), not observed in previous work, were formed as a result of the intramolecular trapping of tetrahedral intermediates. Reasons for the incursion of this unexpected side reaction are discussed.     

Photoelectron spectra of polyunsaturated [4,4,2]propellanes

The photoelectron spectra of the six propellanes 1 to 6 have been recorded. Those bands which correspond to ejection of an electron from a π-orbital have been assigned, using the concept of through bond and through space interaction. Homoconjugative interaction between the π-systems of the two butadiene moieties of 6 is of the same order as that of the π-orbitals in norbornadiene.