ParaHydrogen Polarized Ethyl-[1-13C]pyruvate in Water,a Key Substrate for Fostering the PHIP-SAH Approach to Metabolic Imaging

An efficient synthesis of vinyl-[1-¹³C]pyruvate has been reported, from which ¹³C hyperpolarized (HP) ethyl-[1-¹³C]pyruvate has been obtained by means of ParaHydrogen Induced Polarization (PHIP). Due to the intrinsic lability of pyruvate, which leads quickly to degradation of the reaction mixture even under mild reaction conditions, the vinyl-ester has been synthesized through the intermediacy of a more stable ketal derivative. ¹³C and ¹H hyperpolarizations of ethyl-[1-¹³C]pyruvate, hydrogenated using ParaHydrogen, have been compared to those observed on the more widely used allyl-derivative. It has been demonstrated that the spin order transfer from ParaHydrogen protons to ¹³C, is more efficient on the ethyl than on the allyl-esterdue to the larger J-couplings involved. The main requirements needed for the biological application of this HP product have been met, i. e. an aqueous solution of the product at high concentration (40 mM) with a good ¹³C polarization level (4.8 %) has been obtained. The in vitro metabolic transformation of the HP ethyl-[1-¹³C]pyruvate, catalyzed by an esterase, has been observed. This substrate appears to be a good candidate for in vivo metabolic investigations using PHIP hyperpolarized probes.     

Saturated Commutative Spaces of Heisenberg Type

In this paper, we give a partial classification of commutative spaces of Heisenberg type. Several classification results were known previously. In order to avoid complicated technical details, we restrict ourselves to saturated commutative spaces. Our results are presented in Table II.     

An algorithm for the single-input partial pole assignment problem

An algorithm for translating unstable eigenvalues of single-input partial pole assignment problems based on rank-one transformations is suggested. Special attention is paid to the practical case where translations are constructed using inexact spectral information provided by the Arnoldi procedure. Estimates of the resulting perturbations of stable and translated poles are derived. These estimates depend on the accuracy of spectral information about the unstable poles. The algorithm proposed is illustrated with numerical examples. Bibliography: 11 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 229, 1995, pp. 5–28. Translated by A. Yu. Yeremin.     

Oxidation of 4-H-selenopyrans

Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, p. 996, July, 1991.     

Role of the 3d orbitals of sulfur in the thiapyrylium cation

The electronic structure of the thiapyrylium cation with allowance for and neglect of the 3d orbitals of sulfur was investigated by the self-consistent field MO LCAO method within the CNDO/2 (complete neglect of differential overlap) approximation. Inclusion of the 3d AO of sulfur in the basis leads to slight redistribution of the electron density to favor equalization of the charges on the carbon atoms. A qualitative correlation of the calculated populations of the atoms with the chemical shifts of the PMR spectrum of the thiapyrylium cation was obtained.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1627–1629, December, 1976.     

Thiapyrylium salts (review)

The literature data touching upon the synthesis of thiapyrylium salts and the stability of the thiapyrylium cation as compared with its isoelectronic analogs, as well as the nucleophilic, oxidation, anion-exchange, and other reactions of the salts with substituted and unsubstituted thiapyrylium cations are examined in this review.     

New method for the synthesis of sym- octahydroxanthenes and sym- octahydrothioxanthenes

-Ketols formed as a result of intramolecular cyclization of 1,5-diketones by alkaline condensation of aldehydes with ketones are converted to 9-R-sym-octahydroxanthenes by the action of acids. Treatment of the -ketols with acids in the presence of hydrogen sulfide leads to the corresponding 9-R-sym-octahydrothioxanthenes. The spectral characteristics of the compounds obtained are given, and some of their properties are described.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1615–1619, December, 1978.     

Investigation of the lability of furan and its derivatives in nucleophilic substitution reactions by the mindo/3 method

The a complexes of furan, thiophene, pyrrole, pyridine, and benzene with the hydride ion were calculated by the MINDO/3 method. The affinities of the indicated aromatic rings and a number of substituted furans for the H^– ion were estimated. It is shown that the relative magnitude of the affinity correlates qualitatively with the experimental data on the relative rates of the reaction of the examined compounds with nucleophilic reagents. The following order of increasing reactivities of unsubstituted aromatic rings was obtained: pyrrole相似文献   

Structural Study of C-undecylcalix[4]resorcinarene Solvate with Dioxane

The crystal structure of the molecular complex of C-undecylcalix[4]resorcinarene with dioxane has been determined by X-ray analysis. The asymmetric unit contains one host and four guest molecules. The calix[4]resorcinarene moiety adopts a bowl conformation with C_4v symmetry. Four undecyl chains are axially oriented. Calix molecules are packed in a bowl-to-bowl fashion with alternating hydrophilic and hydrophobic layers. One of the hydrophilic dioxane molecules is located at the rim of the calix moiety and is hydrogen bonded to the other one. There is no interaction to attract, or direct the dioxane molecule into the interior of the cavity. There is an exo complex formed. The dioxane molecules – located in the hydrophobic part – are highly disordered.