Reagents, modifying

The first reports on enantioselective addition reactions of achiral organometallic reagents, modified by aprotic chiral additives, described the addition of Grignard reagents to prostereogenic carbonyl compounds in the presence of ( + )-(/ ,/J)-2,3-dimethoxybutane (l)4 5, (-)-tetrahydro-2-methylfuran (2)6, (-)-l-[(tetrahydro-2-furanyl)methyl]pyrrolidine (3)7 or (-)-sparteine (4)8. The enantioselectivity, however, was poor (0-22% ee). 

ICAT reagent-modified peptide via thioether linkage... 

In the procedure with mobile phase 1 and 2, the visualization is accomplished by screening under uv light (254 and 366 nm) and in addition by spraying with Dragendorff s reagent, modified by Munier and Deboeuf, followed by 30 percent hydrogen peroxide. 

Because of the complex nature of gold-containing Cu-Pb-Zn ores, the reagent schemes used are also complex. Reagent modifiers such as ZnS04, NaCN and lime have to be used, all of which have a negative effect on gold flotation. 

Schematic diagram of the modification of protection from modification by application of a reversible ligand (agonist or antagonist, ). The reversible binding site specific ligand slows the rate at which the MTS reagent modifies the thiolate group of the introduced cysteine...

The sample preparation methodology for the determination of TCDD at these low levels is an active area of development as indicated by the improved procedure reported here and used to analyze the milk for the NIEHS study. It uses reagent modified adsorbants, a higher efficiency basic alumina column than previously (19) and a new degree of separation, reverse phase HPLC as an integral part of the procedure. All of these are directed towards improving the specificity of the sample preparation for 2,3,7,8-TCDD. Increased specificity is needed since the lowest detection limit achievable in all previous studies of TCDD in environmental samples has been dictated by the presence of other substances in the samples which have not been removed by the sample preparation. 

SchifPs Reagent, Modified Dissolve 200 mg of rosaniline hydrochloride (C20H20CIN3) in 120 mL of hot water. Cool, add 2 g of sodium bisulfite (NaHS03) followed by 2 mL of hydrochloric acid, and dilute to 200 mL with water. Store in a brown bottle at 15° or lower. 

Fig. 22 Absorption spectra of [Ru(phen)3]2+ 10 pM at pH = 6.0, NaCl (0.3 M) (solid curve) in presence of H2TPPS4 10 pM (dashed curve). Spectra were recorded about 1 h after mixing the reagents. Modified from [51]...

Enantioselective Conjugate Addition to Prochiral Enones of Organometallic Reagents Modified with Ephedrine. Enantioselective conjugate addition to 2-cyclohexenone with chiral organo(alkoxo)cuprates [MCu(OR )R] has been studied. When the cuprate is prepared from the lithium alkoxide of ephedrine, Phenyllithium, and Cul, 3-phenylcyclo-hexanone with 50% ee is obtained. The enantioselectivity reaches 92% ee in enantioselective ethylation when a chiral diamino alcohol derived from ephedrine is employed (eq 13). ... 

If the change of reagents modifies the influence of the variables, a measure of this is the difference of the effects of the variables determined in the different blocks, e.g. a difference in the sensitivity of variation in temperature is measured by the difference bj - b ... 

A complete factorial design for each reagent would provide rather detailed infonnation on main effects and interaction effects of the experimental variables. It would also provide infonnation on to how a change of reagent modifies these effects. In a screening situation, this may not be necessary. With complete factorial designs, the number of experiments is still rather high. 

Organic Solvent. The organic phase consists of two or three components reagent, modifier, and solvent. A basic study of possible chemicals for these components dates back to 1960 [5.33],... 

Acyl Anion Equivalents d1 Reagents Modified Acetals as Acyl Anion Equivalents... 

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