Asymmetric hydrogenation of methyl 3,5-dioxohexanoate catalyzed by ru-binap complex: a short step asymmetric synthesis of dihydro-60methyl-2-H-pyran-2-one

Hydrogenation of methyl 3,5-dioxohexanoate 3 using Ru₂Cl₄((R) or (S)-binap)₂(NEt₃) as the catalyst gave dominantly anti 3,5-dihydroxyester 9, which was then converted into unsaturated lactone 4. The pathway of the hydrogenation reaction was also investigated.     

Phase transfer-catalyzed nitromercuration of diene polymers

A mild, efficient method of nitrating olefins was described recently by Corey and Estreicher. Application of their procedure to diene polymers failed because of the insolubility of the hydrophobic polymer in the aqueous nitromercuration regent. Use of water-immiscible organic cosolvents gave slow nitromercuration with substantial formation of nitrite esters. To overcome these problems a nonaqueous phase transfer-assisted method of rapid selective nitromercuration of diene polymers was developed.     

Aromatic sulphonate ion-selective electrode membrane with crystal violet as ion-exchange site

Four triphenylmethane derivatives (cations) and a high molecular-weight quaternary ammonium ion were used as the ion-exchange site in the liquid membranes of electrodes responsive to aromatic sulphonate ions, such as benzenesulphonate and alpha-naphthalenesulphonate. The nitrobenzene or 1,2-dichloroethane membrane containing the Crystal Violet-aromatic sulphonate pair had good sensitivity, showing an approximately Nernstian response down to 10(-4)M sulphonate. The potential of the Crystal Violet membrane was independent of pH variation from 2.5 to 12. Chloride and sulphate ions in the aqueous sample solution did not affect the electrode potential. 1,3,6-Naphthalenetrisulphonate exerted essentially no influence on the potential of the alpha-naphthalenesulphonate electrode. The interference of the nitrate ion was relatively large. The conductivity and association of the solute species in the membrane were estimated.     

Capillary electrochromatographic separation of amino acid enantiomers with molecularly imprinted polymers as chiral recognition agents

The use of molecularly imprinted polymers polymerized in a capillary for the separation of amino acid enantiomers by electrochromatography is described. The substrate-selective polymers were prepared by using l-phenylalanine anilide as print molecule and methacrylic acid as the functional monomer. The treatment of the inside surface of the capillary, the composition of the polymer and the electrochromatographic running conditions were investigated. This preliminary report demonstrated a novel and simple method for capillary electrochromatographic separations of amino acid enantiomers using molecularly imprinted polymers. Received: 9 April 1996 / Revised: 8 August 1996 / Accepted: 8 August 1996     

2-甲基-7-亚甲基-1,4,6-三氧螺[4,4]壬烷与丙烯腈、丙烯酸甲酯的共聚合反应及竞聚率的测定

用高效液相色谱跟踪2-甲基-7-亚甲基-1,4,6-三氧螺[4,4]壬烷(MMTN)与丙烯腈(AN),丙烯酸甲酯(MA)的共聚合反应。根据Lowry-Meyer共聚积分方程式,采用插值法进行数据拟合测定单体的竞聚率。对于体系MMTN(M_1)-AN(M_2),r_1=0.048;r_2=0.213;MMTN(M_1)-MA(M_2)r_1=0.025,r_2=0.764。说明两组共聚体系均有较强的交替共聚趋势。     

Discrete decomposability of the restriction ofA q(λ) with respect to reductive subgroups and its applications

Summary LetGG be real reductive Lie groups and q a -stable parabolic subalgebra of Lie (G) . This paper offers a sufficient condition on (G, G, q) that the irreducible unitary representation ofG with non-zero continuous cohomology splits into a discrete sum of irreducible unitary representations of a subgroupG, each of finite multiplicity. As an application to purely analytic problems, new results on discrete series are also obtained for some pseudo-Riemannian (non-symmetric) spherical homogeneous spaces, which fit nicely into this framework. Some explicit examples of a decomposition formula are also found in the cases whereA _q is not necessarily a highest weight module.Oblatum 3-IV-1993The author is supported by the NSF grant DMS-9100383.     

Mass level of heavy flavored hadrons in the heavy-quark effective theory

We have studied the heavy flavored hadron spectroscopy, which is motivated by the heavy quark effective theory. TheQ \(\bar q\) ,Qqq andQQq hadrons have been investigated systematically. Regarding thes-quark as a member of heavy quarks, the predicted mass levels of both theQqq andQQq baryons are quite consistent with experimental ones.     

Diastereo- and enantioselective reduction of α,β-diketodithiane with the baker's yeast

The Baker's yeast reduction of 1-(1,3-dithian-2-yl)-1,2-propanedione gave highly enantio-and diastereoselectively (S)-(+)-(1-1,3-dithian-2-yl)-2-hydroxy-1-propanone or (1S,23-(+)-(1)-(1,3-dithian-2-yl-1,2-propanediol, depending on the reaction time. The hydroxy ketone was reduced with diisobutylaluminum hydride to give (1R,2S)-1-(1,3-dithian-2-yl)-1,2-propanediol with high diastereoselectivity. The former (1S,2S)-diol was converted into L-digitoxose.     

Cyclopolymerization. XIX. Effect of N-substituents on cyclopolymerizability of N-allylmethacrylamides

The effect of bulky N-substitutents of N-t-butyl- and N-phenyl-N-allylmethacrylamides (BAMA and PAMA, respectively) on their cyclopolymerizability was investigated. BAMA yielded an almost completely cyclized polymer while the degree of cyclization of poly (PAMA) was about 95%. The latter value indicates that the effect of phenyl group is comparable with that of methyl group, since N-methyl-N-allylmethacrylamide was reported to give a polymer with a degree of cyclization of 93%. Structural investigation on telomerization products of BAMA and PAMA permitted the assignment of the repeating cyclic units of these polymers to that of a five-membered ring. This structural characteristic was also supported by the observation of five-membered cyclized radicals on ESR measurements of these monomers. Rotation around amide C? N bonds of these monomers and related compounds studied by ¹³C-NMR was found to be strongly dependent on N-substitutents. The mechanism of the cyclization was discussed in terms of the structure of the ring formed and rotation around amide C? N bonds of these monomers. The reactivity of the methacryloyl and allyl groups involved in these monomers were compared based on the information obtained by structural investigation of polymers and telomerization products and by ESR studies. © 1993 John Wiley & Sons, Inc.