Dual activation in a homolytic coupling reaction promoted by an enantioselective dinuclear vanadium(IV) catalyst

A new concept of dual activation catalysis in homolytic coupling reaction of 2-naphthol derivatives is described. The dinuclear vanadium(IV) catalyst (R,S,S)-1a promotes the oxidative coupling reaction of 2-naphthol derivatives with high reactivity and enantioselectivity. This dual activation mechanism is supported by the fact that the reaction rate of oxidative coupling of 2-naphthol promoted by the (R,S,S)-1a is 48 times faster than that of the mononuclear complex (S)-3 and a lower catalyst loading of (R,S,S)-1a shows higher catalyst efficiency both in enantioselectivity and chemical yield.     

Enantioselective synthesis of 1-deoxy-d-gulonojirimycin from a phenylglycinol-derived lactam

Cyclocondensation of (R)-phenylglycinol with appropriately γ-substituted δ-oxo acid derivatives provides bicyclic lactams from which the enantioselective synthesis of 1-deoxy-d-gulonojirimycin has been reported.     

Tröger's base scaffold in racemic and chiral fashion as a spacer for bisdistamycin formation. Synthesis and DNA binding study

‘Head-to-head’ oligo-N-methylpyrrole peptide dimers linked by a methano[1,5]diazocin scaffold are presented in racemic as well as chiral fashion. Their DNA binding activities were assayed on calf thymus DNA, poly(dA-dT)₂, and poly(dC-dG)₂ by NMR and ECD spectroscopies, and fluorescence probe displacement assay. The presented dimers prefer AT sequences, but show higher affinity to poly(dC-dG)₂ than distamycin A. The (4R,9R) configuration of methanodiazocin bridge was found to be better suited for interaction with ct-DNA and poly(dA-dT)₂ than (4S,9S) configuration.     

Enantioselective catalytic epoxidation of nonfunctionalized prochiral olefins by dissymmetric chiral Schiff base complexes of Mn(III) and Ru(III) metal ions II

A series of new dissymmetric chiral Schiff base complexes has been obtained by a systematic condensation of (1S,2S)(+)-diaminocyclohexane and 3-acetyl-4-hydroxy-6-methyl-2-pyrone with salicylaldehyde, 5-chloro-, 5-methoxy-and 5-nitrosalicylaldehyde and by subsequent metallation with manganese and ruthenium. The characterization of the complexes 1–8 was accomplished by physico chemical studies viz. microanalysis, IR-, UV/VIS-, and CD spectral studies, optical rotation, molar conductance measurements and cyclic voltammetry. Enantioselective epoxidation of non functionalised olefins, viz. cis-stilbene, trans-3-nonene and trans-4-octene with iodosyl benzene as oxidant was demonstrated in the presence of catalytic amounts of chiral Mn(III) and Ru(III) dissymmetric Schiff base complexes. Good optical yields of epoxides were obtained for the catalyst 4 with the substrates trans-3-nonene and cis-stilbene.     

Ni-P/SiO_2催化剂晶化过程及其加氢活性研究

采用化学还原法制备了负载型Ni－P／SiO2非晶态合金催化剂．应用ICP、BET、氢氧滴定法、XRD、SEM、XPS研究了上述催化剂在高温晶化过程中的表面结构、表面形貌和表面电子态的变化。测定了Ni－P／SiO2非晶态合金晶化前后对其液相苯甲醛加氢反应催化活性和选择性,并讨论了非晶态合金催化剂晶化过程中结构变化对催化性能的影响．     

Determination of enantiomeric excess and degree of hydrogenation in the enantioselective hydrogenation of ketopantolactone

Summary A new gas chromatographic method for the simultaneous determination of the degree of hydrogenation of ketopantolactone and the enantiomeric excess of pantolactone does not require any derivatisation.

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Bestimmung von Enantiomerenüberschuß und Hydriergrad bei der enantioselektiven Hydrierung von Ketopantolacton (Kurze Mitt.)

Zusammenfassung Zur Bestimmung des Hydriergrads von Ketopantolacton und des Enantiomerenüberschusses von Pantolacton wird ein neues gaschromatographisches Verfahren eingesetzt, das keine Derivatisierung erfordert.

     

Electroorganic synthesis of benzathine

Benzathine is prepared in good yields from cyanobenzene by a combination of electrochemical hydrogenation and Kolbe electrolysis using nickel and platinum electrodes in the presence of methanolic sodium methoxide in an undivided cell.     

有机高分子金属络合物催化剂——在加氢方面的应用

论述了各种带有氮、氧、磷等配位基团的可溶性和不溶性高分子与铑、钯、铂等贵金属配位后对氢化反应的催化作用。一般说有机高分子-金属络合物催化剂比相应的低分子催化剂催化活性、稳定性和选择性都高。     

新型手性双膦配体的合成及其催化性能考察

以苯乙烯为原料,通过Sharpless不对称二羟基化反应合成高对映体纯的苯基乙二醇,经环化、亲核开环和取代反应转化为手性碳膦-氧膦型双膦配体.后者与[Rh(COD)Cl]2及NH4PF6作用生成手性膦-铑阳离子催化剂.在α-脱氢氨基酸衍生物的不对称氢化反应中,化学转化率为100%,对映选择性最高达到77?.     

Synthesis of glutamate by reductive amination of 2-oxoglutarate with the combination of hydrogenase and glutamate dehydrogenase

Glutamate synthesis by reductive amination of 2-oxoglutarate was performed by the combination of NADH regeneration system and glutamate dehydrogenase (GluDH). The conversion of 2-oxoglutamate to glutamate was 98% after 3 h, and the turnover number of NAD⁺was 17.