Gibberellin metabolites from ent-kaura-2,16-dien-19-ol and its succinate in Gibberella fujikuroi

Exposure of ent-kaura-2,16-dien-19-ol (1) or its succinate (2) to resuspended mycelia of G. fujikuroi has produced a complex mixture of acids which after methylation gave the esters of two C₁₉ (24) and (30) and five C₂₀ gibberellins (4, 11, 20, 32 and 33). The triester (32) and the lactone ester (24) have been prepared before from the esters of gibberellin A₁₃ (8) and gibberellin A₄ (26) respectively. The structures of the other metabolites were assigned on spectroscopic data and by chemical transformations. Thus the lactone diester (4) has been converted to the known keto triester (6). The epoxide (11) has been related to gibberellin A₁₄ (14) and the aldehyde (33) has been related to gibberellin A₁₃ trimethyl ester (8) by way of the triol (34). Selective de-epoxidation of the 16,17-epoxy function in diepoxides has provided a route from the dienes (20 and 24) to the epoxides (11 and 30) respectively, but not from the ester of gibberellin A₅ (23) to that of gibberellin A₆ (29). On the other hand the latter can be obtained by epoxidation of gibberellin A₅ methyl ester trifluoroacetate. Backfeeding experiments carried out with the epoxy diacid (12), the diene diacid (21) and the derived diol (39) indicate pathways connecting the various metabolites. The natural gibberellins A₅ and A₆ were shown to be formed in some of the backfeeding experiments.     

Determination of the position of the acyl groups and the nature of some amino alcohols in native ester alkaloids of the genusVeratrum

Conclusions 1. On the basis of literature data on the structure of theVeratrum alkaloids, a definite law for the arrangement of the acyl radicals in these ester alkaloids and an interrelationship between the melting point and the structure of the substituent in the C₇ position, and between the melting point and the types of amino alcohols upon which the ester alkaloids are based, has been found.2. The features mentioned may be used in studying the structure of theVeratrum ester alkaloids according to a scheme which we propose.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 4, pp. 440–443, 1970     

Retention of85Sr and147Pm on insoluble hydroxides and phosphates prepared by the sol-gel procedure

Retention of strontium and promethium on hydroxides (hydrated oxides) and phosphates of iron and chromium prepared by the sol-gel method was studied. The sorption was determined under static conditions depending on the pH of the solution. The sorption isotherms and retention were investigated under dynamic conditions.     

Distribution of some elements in a solid - aqueous system: Mineral phosphate in contact with groundwater

The distribution of U, Th, Am, Eu, Cs, Sr and Ra in a solid-aqueous system, natural phosphate in contact with groundwater was investigated using g- and a-spectroscopy. The effect of contact time, pH, particle size of the solid phase, and the concentration of a concurrent element Ca, were studied. The results show that more than 98% of the actinide elements and europium are adsorbed by the solid phase under all conditions. The fission products Cs and Sr have different behaviors, depending on the experiment conditions. The behavior of Ra is closer to the actinides than to the fission products. There are small differences between the behaviors of the actinide elements, which can be interpreted by migration mechanism from the aqueous to the solid phase, i.e., adsorption or precipitation.     

Some lessons from the development of metal hydride chemistry in the light of hydrogen storage problems

The main trends of the chemistry of hydrides of transition metals and their alloys are briefly reviewed. “Sensational” hydrogen capacity data and the potential of some metal materials (metals, alloys, and quasi-crystals) and carbon nanomaterials in reversible hydrogen storage applications are critically analyzed. The significance of research in this field for hydrogen energy applications is underlined.     

Enantioselective reduction of ketophosphonates using chiral acid adducts with sodium borohydride

A method for asymmetric reduction of α-and β-ketophosphonates using a chiral complex prepared from sodium borohydride and D-or L-tartaric acid is developed. Reduction of α-or β-ketophosphonates by these reagents led to formation of corresponding (S)-or (R)-hydroxyphosphonates. Reduction of chiral di(1R,2S,5R)-menthylketophosphonates by the chiral complex NaBH₄/(R,R)-tartaric acid due to the dual compliant asymmetric induction resulted in increased stereoselectivity of the reaction and led to formation of the hydroxyphosphonates with ee 90% or higher. On the other hand, reduction of di(1R,2S,5R)-methylketophosphonates by the chiral complex NaBH₄/(S,S)-tartaric acid proceeded as non-compliant dual asymmetric induction and resulted in decreased reaction stereoselectivity leading to formation of hydroxyphosphonates with ～45–60% ee. The developed methodology was applied to the synthesis of (R)-phosphocarnitine in multigram amounts.     

Quantitative structure-property relationship: XXVII. Estimation of the free energy of formation of host-guest complexes of α-cyclodextrin with benzene derivatives

A structure-property relationship was used to estimate the free energy of formation of host-guest complexes of α-cyclodextrin with monosubstituted benzene and phenol derivatives and with symmetrical 1,4-disubstituted benzene derivatives, in which various nonvalent interactions (hydrophobic, van der Waals, donor-acceptor) play a significant role. The calculated values are well consistent with the experiment.     

Electron screening in low energy scattering of muonic hydrogen on hydrogen atoms

Electron screening corrections to the cross sections for low energy scattering of muonic hydrogen on hydrogen atoms are calculated. It is shown that the presence of the electron influences considerably the elastic cross sections at collision energies below 1 eV. This influence is relatively small for the spin-flip and isotopic exchange processes.