Dimethylsilyl modification

Reversed phase with C-8 or C-18 hydrocarbon chain Reversed phase with dimethylsilyl modification Water-tolerant, wettable layer Mean pore size in A... 

The urine samples were analyzed using a modified version of a published method.8 The method involved fortification of the urine samples with an internal standard 3,4,5-trichloro-2-pyridinyl, which is a structural isomer of the 3,5,6-TCP metabolite of chlorpyrifos hydrolysis of labile acid conjugates to 3,5,6-TCP solvent extraction derivitization to the f-butyl-dimethylsilyl ester of 3,5,6-TCP and subsequent negative-ion chemical ionization gas chromatography/mass spectrometry (GC/MS) analysis. Creatinine was determined in urine using a modification of a method of Fabiny and Erting-shausen.9... 

The synthesis of enantioenriched acyl chloride 54 was originally conducted using a modification of procedures described by Villieras and coworkers for the preparation of racemic alcohol 55 (Scheme 12). Thus, the synthesis commenced with the preparation of racemic allylic alcohol 55 from 2,5-dimethoxytetrahydrofuran. The alcohol was resolved enzymatically, following procedures reported by Ogasawara, to provide enantioenriched alcohol (S)-55 in 50% yield and 99% ee. Protection of the alcohol with the sterically encumbered ferf-butyl dimethylsilyl group allowed a diastereoselective copper(I)-mediated conjugate addition of methyl magnesium bromide to... 

Several methods for the reduction of allylic functional groups have been reported. Although some of these are derivative of earlier procedures, useful improvements and modifications are noteworthy. For example, combination of [Pd(PhaP)4] with lithium triethylborohydride provides an effective system for the reductive removal of allylic ethers, sulphides, sulphones, selenides, and t-butyl-dimethylsilyl ethers. Many of these functional groups, of course, are not readily removed by other methods. Furthermore, this combination gives good to excellent maintenance of the regio- and stereo-integrity of the allylic double bonds. In a similar fashion, 2-tosyl homoallyl alcohols can be easily desulphonylated to... 

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