Search results for "Excess"

Cu2+ Coordination Properties of a 2-Pyridine Heptaamine Tripod: Characterization and Binding Mechanism

2009

The synthesis, protonation, and Cu(2+) coordination chemistry of a tripodal heptaamine ligand (L(1)) functionalized with 2-pyridine fragments at the ends of its three branches are reported. L(1) presents six relatively high protonation constants followed by much more reduced constant that as indicated by the UV-vis and NMR data, occur on the pyridine fragments. p[H]-metric, ESI/MS(+), EPR and UV-vis data show that L(1) is able to form mono-, di-, and trinuclear Cu(2+) complexes. Slippage movements and molecular reorganizations have been observed to occur as a function of p[H] in the 1:1 Cu(2+) complexes. The kinetic studies showed that the complex formation is fast and proceeds through a di…

ChemInform Abstract: Enantioselective LaIII-pyBOX-Catalyzed Nitro-Michael Addition to (E)-2-Azachalcones.

2013

A [La(OTf)3] complex with a new pyBOX ligand bearing a bulky 1-naphthylmethyl substituent at the 4′-position of the oxazoline ring catalyzes the conjugate addition of nitroalkanes to a broad range of (E)-2-azachalcones, providing the expected nitro-Michael products with good yields and enantiomeric excesses up to 87 %. The optical purity of the products can be increased by a single crystallization. A plausible stereochemical model to account for the observed stereochemistry has been proposed.

Physiologische Erythrozyten-Protektionslösung (PEP)

2001

Separation of Enantiomers in a Monolayer of Racemic 3-Hexadecyl-oxy-propane-1,2-diol

1993

Monolayers of a racemic mixture and of the pure S enantiomer of 3-hexadecyloxy-propane-1,2-diol have been characterized by thermodynamic measurements at the air/water interface as well as by fluorescence microscopy. The critical temperatire T c , the limiting molecular area at high pressure and the pressure π c corresponding to the observed main phase transition, derived from the isotherms, slightly depend on chiral purity

A Simple Organocatalytic Enantioselective Synthesis of Pregabalin

2009

This paper describes a new procedure for the enantioselective synthesis of the important anticonvulsant drug Pregabalin, which shows biological properties as the (S) enantiomer only. The key step of the synthetic sequence is the Michael addition reaction of Meldrum's acid to a nitroalkene mediated by a quinidine derived thiourea. A variety of novel catalysts bearing different groups at the thiourea moiety were synthesized and tested. The most successful catalyst that incorporates a trityl substituent provided up to 75 % ee of (S)-4. The conjugate addition reaction was carried out on a multigram scale with low loadings of catalyst (10 mol-%). Moreover, the catalyst can be recycled showing th…

Synthesis of Chiral Catalyst Modifiers by Hydrosilylation of Cinchonidine and Their Application in the Hydrogenation of 1-Phenylpropane-1,2-dione and…

2005

Four new chiral modifiers were synthesized in order to investigate the effect of distal modifier substitution in the hydrogenation of ethyl pyruvate and 1-phenylpropane-1,2-dione on a supported Pt/Al2O3 catalyst. The chiral modifiers were prepared in good to moderate overall yields by Pt-catalyzed hydrosilylation of 9-O-TMS-protected cinchonidine with triethylsilane, triphenylsilane, bis(dimethylsilyl)ethane and (+)-(R)-methyl(1-naphthyl)phenylsilane followed by cleavage of the silyl ether protective group. Comparison of the synthesized modifiers in enantioselective hydrogenation using cinchonidine as reference modifier is reported, as well as details on their synthesis and characterization…

Kinetische Racematspaltungen ausgehend vonrac-Alkoholen oderrac-Carbonsäurehalogeniden unter Mitwirkung optisch aktiver Induktorbasen

1989

Bei der Umsetzung eines Molaquivalents achiraler Carbonsaurehalogenide mit zwei Molaquivalenten rac-Alkoholen entstehen unter Mitwirkung von einem Molaquivalent einer optisch aktiven Induktorbase (tertiares Amin) partiell optisch aktive Ester sowie partiell optisch aktive Alkohole in zum Teil hoher optischer Reinheit (60 – 70%). Der im Ester gebundene Anteil an Alkohol sowie der nicht umgesetzte Alkohol haben entgegengesetzte Konfiguration. Der Induktionsgrad ist ahnlich hoch, wenn man zwei Molaquivalente eines rac-Carbonsaurehalogenids mit je einem Molaquivalent eines achiralen Alkohols und einer Induktorbase umsetzt. Der Carbonsaureanteil im Ester und die freie Saure haben entgegengesetzt…

Enantioselective LaIII-pyBOX-Catalyzed Nitro-Michael Addition to (E)-2-Azachalcones

2013

A [La(OTf)3] complex with a new pyBOX ligand bearing a bulky 1-naphthylmethyl substituent at the 4′-position of the oxazoline ring catalyzes the conjugate addition of nitroalkanes to a broad range of (E)-2-azachalcones, providing the expected nitro-Michael products with good yields and enantiomeric excesses up to 87 %. The optical purity of the products can be increased by a single crystallization. A plausible stereochemical model to account for the observed stereochemistry has been proposed.

Clinical manifestations of cancer in patients with acute pulmonary embolism

2023

Background Neoplasmatic disease increases the risk of acute pulmonary embolism (APE) by different pathophysiological mechanisms that favor thrombosis in patients with cancer. Recently, the role of cancer (active and occult) in the prevalence of venous thromboembolism has been discussed more thoroughly in the subject literature. Material Medical records of 366 consecutive patients with a diagnosis of APE (aged: mean = 65.0 ± 16.6, median = 68, range = 19–94; men = 41%/women = 59%) were collected with a wide range of demographic data, medical history of coexisting diseases, computer examination, and laboratory tests. Methods The APE patients were analyzed in two groups: negative cancer cases …

Relationship between dysfunctional eating patterns and binge drinking in young people and associated risk factors

2022

La joventut (compresa entre els 18 i 30 anys) es considera un període de vulnerabilitat, en què és freqüent observar trastorns alimentaris, consum de drogues i una major tendència a buscar noves sensacions i comportaments de risc, entre moltes altres conductes. En concret, hi ha dos comportaments molt prevalents en els joves i s'associen amb conseqüències de salut molt negatives: el consum de menjar ultraprocessat i el consum d'alcohol. Tot i això, el problema no rau només en el tipus de consum (és a dir, beure alcohol o menjar menjar ràpid), sinó també en com es consumeix l'alcohol o el menjar. L'afartament es caracteritza per la ingesta de grans quantitats de menjar (afartament de menjar)…