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1.
Robert Glaser Menachem Twaik Shimona Geresh Jeanine Blumenfeld 《Tetrahedron letters》1977,18(52):4635-4638
Z--acetamidocinnamic acid was hydrogenated with neutral diphosphine-rhodium(I) complexes containing trans-1,2-bis(diphenylphosphinomethyl) cycloalkanes to give N-acetylphenylalanine: 86 % e.e.-(R) [(1R,2R)-cyclobutane]; 63 % e.e.-(R) [(1R,2R)-cyclopentane]; 35 % e.e.-(S) [(1S,2S)-cyclohexane]; and 82 % e.e.-(R) [(2R,3R)-DIOP]. Similarly, -acetamidoacrylic acid was hydrogenated to give N-acetylalanine: 72 % e.e.-(R) [(1R,2R)-cyclobutane]; 72 % e.e.-(R) [(1R,2R)-cyclopentane]; 40 % e.e.-(S) [(1S,2S)-cyclohexane]; and 73 % e.e.-(R) [(2R,3R)-DIOP]. 相似文献
2.
Wolfson A Janssens S Vankelecom I Geresh S Gottlieb M Herskowitz M 《Chemical communications (Cambridge, England)》2002,(4):388-389
A new chiral heterogeneous catalytic system obtained by occlusion of the Rh-MeDuPHOS complex in a polydimethylsiloxane film was tested in the asymmetric hydrogenation of methyl 2-acetamidoacrylate in aqueous medium. 相似文献
3.
Hydrogenation of bicyclo[2.2.1]heptadiene-1R,2R-(trans-1,2-bis(diphenylphosphinomethyl)cyclbutane rhodium (I) tetrafluoroborate in methanol gives a solvent adduct which reacts with N-acyldehydroamino acids and their esters to give air-unstable scarlet to yellow complexes. Effects of structure variation in the enamide on the 31P NMR spectra of these species are reported and discussed with reference to (a) the equilibrium between methanol and enamide complexes; (b) the ratio of diastereomeric enamide complexes formed; (c) the temperature dependence of this ratio; (d) the rate of complexation equilibria and (e) the structure of enamide complexes, which are normally bidentate with binding via the olefin and amide groups. In certain cases the complex may be terdentate and E-enamides bind through the olefin and carboxyl groups. Each mode of binding gives rise to characteristic 31P NMR spectra with regard to P-P and P-Rh coupling constants. 相似文献
4.
5.
Glaser Robert Geresh Shimona Luria Shlomo Drouin Marc Michel André 《Structural chemistry》1994,5(4):277-282
Hydrogenation ofZ-(–)-(1R, 3R, 4S)-menthyl 2-formamido-4,4,4-trifluoro-2-butenoate catalyzed by Pd/C was performed at atmospheric pressure to yield a mixture of (2R, 1R, 3R, 4S)- and (2S, 1R, 3R, 4S)-menthyl 2-formamido-4,4,4-trifluorobutanoate diastereomers in a 5545 ratio, respectively. Repeated fractional crystallization from ethyl acetate and vapor diffusion of petroleum ether afforded (+)–(2S, 1R, 3R, 4S)-menthyl 2-formamido-4,4,4-trifluorobutanoate as clear colorless, crystalline prisms which were subjected to single-crystal X-ray diffraction analysis. The crystals belong to the orthorhombic system P212121, and at 213 K:a=5.054(1),b= 10.000(2),c=32.707(1) Å,V=1652.9(4) Å3,Z=4,R(F)=0.040, andR
w
(F)=0.037. The finding of the (2S)-configuration for the formamido-acid portion of the (+)-ester enabled the configurational assignment of the asymmetric hydrogenation products ofZ-methyl 2-formamido-4, 4,4-trifluoro-2-butenoate catalyzed by chiral diphosphine/rhodium(I) complexes. 相似文献
6.
Z-α-acylaminocinnamic acids and esters were hydrogenated with rhodium(I) complexes containing (4R,5R) - trans - 4,5 - bis(diphenylphosphinomethyl) - 2,2 - dimethyl - 1,3 - dioxolan (DIOP). Increasing the steric bulk of the acyl function (NHCOR, where R is an alkyl moiety) resulted in a lowered reduction of the si-re prochiral face to yield a decreasing excess of the (R)-amino acid derivatives. In the series of N-acylphenylalanine free acids (resulting from hydrogenation of Z-α-acylaminocinnamic acids) the optical purity decreased from 82% ee-(R) [Me]; 57% ee-(R) [i-Pr]; 52% ee-(R) [t-Bu]; to 46% ee-(R) [1-adamantyl]. Theα-benzamido, α-formamido and α-trifluoroacetamido substrates gave hydrogenation products having 68% ee-(R) [Ph]; 60% ee-(R) [H]; and 16% ee-(R)[CF3]. In the corresponding methyl esters, increasing the steric bulk of the acyl function (NHCOR) resulted in a markedly greater decrease in enantioface differentiation. In the series of N-acylphenylalanine methyl ester products (resulting from hydrogenation of Z-methyl α-acylaminocinnamates) the optical purity decreased from 69% ee-(R)[Me]; 15% ee-(R) [i-Pr]; to 0% ee[t-Bu and 1-adamantyl]. The α-benzamido, α-formamido, and α-trifluoroacetamido substrates gave hydrogenation products having 36% ee-(R) [Ph]; 58% ee-(R) [H]; and 22% ee-(S) [CF3]In the series of N-acetylphenylalanine alkyl ester products (resulting from hydrogenation of Z-alkyl α-acetamidocinnamate esters) trifluoro substitution in the alkyl alcohol moiety resulted in a decrease in optical purity to 52% ee-(R) [CH2CF3] compared to 72, 76 and 77% ee-(R) [Et, i-Pr and t-Bu, respectively]. 相似文献
7.
Akiva Gross Shimona Geresh George M. Whitesides 《Applied biochemistry and biotechnology》1983,8(5):415-422
S-Adenosyl-L-methionine (SAM) has been synthesized on 7-mmol scale from L-methionine and ATP. The ATP was generated in situ from AMP, and the synthesis of SAM was catalyzed by the enzyme ATP:L-methionine S-adenosyltransferase (EC 2.5.1.6). Although substantial effort was required to obtain even small quantities of enzyme, it has good stability once isolated and immobilized. The SAM produced by this procedure contains 89% of the (-) diasterioisomer and 11% of the (+) diasterioisomer. 相似文献
8.
The structure and physicochemical properties of the sulfated polysaccharides that encapsulate cells of the red microalgae have been studied in our laboratory for a number of years with the aim of evaluating their potential applications.2-6 Exploitation of the charged groups of these heteropolymers as chelating agents could provide an environmentally friendly means of disposing of toxic metals in industrial wastes. Ion exchangers and affinity absorbents may be prepared by crosslinking polysaccharides with epichlorhydrin, for example, mucopolysaccharides can bind polyvalent ions.7-9 相似文献
9.
(+)-(25,3S)-DIOP was used in neutral rhodium(I)-diphosphime complexes to catalyze the asymmetric hydrogenation of Z-methyl-u-acylaminocimnamates. Increasing steric bulk in the acyl function (NHCOR, where R is a hydrocarbon moiety) resulted in a decrease in optical purity of the N-acylphenylalanine methyl ester products. The optical purity decreased from 69 % ee (S) [Me], 15 % ee (S) [i-Pr], to 0 % ee [t-Bu and 1-adamantyl]. The α-formamido substrate decreased in optical purity [58 % ee (S)] relative to the Me analogue. The a-trifluoroacetamido analogue gave a reversal in chirality [22 % ee (R)]. 相似文献
10.
Z-α-N-methylacetamidocinnamic acid and its methyl ester were hydrogenated with rhodhim(I) complexes containing (2R, 3R)-O-2,3-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane (DIOP) or its carbocyclic analogues: (1R,2R)-trans-1,2-bis(diphenylphosphinomethyl)cyclobutane or (1S,2S)-trans-1,2-bis(diphenylphosphinomethyl) cyclohexane. The N-acetyl-N-methylphenylalanine methyl ester reaction product was formed with an optical purity of 73% ee-(R) [(2R, 3R)-DIOP]; 43% ee-(R) [(1R, 2R)-cyclobutane analogue]; and 26% ee-(R) [(1S,2S])-cyclohexane analogue]. Similarly, N-acetyl-N-methylphenylalanine was formed with an optical purity of 87% ee-R [(2R, 3R)-DIOP] and 68% ee-(R) [(1R, 2R)-cyclobutane analogue]. 相似文献