Trimethylsilyl deriv applications

Application of the integrated GC/MS system to problems in organometallic chemistry currently falls far short of potential. Interestingly, one of the major applications of GC/MS in organometallic systems has been made with compounds of biochemical interest. The widespread use of trimethylsilyl derivatives for GC (288, 289) was extended to MS (290) and GC/MS spectrometry (291, 292). Similarly, the use of GC for... 

For groups experienced in trace analysis of chemical markers for bacteria, currently samples are analyzed almost exclusively by GC-MS/MS. GC-MS/MS assays are now well established and a wide range of clinical and environmental samples have been analyzed. However, application in the pharmaceutical industry requires further evaluation. For example, Mur is released by hydrolysis and analyzed as an alditol acetate 3-OH FAs after methanolysis are converted to methyl trimethylsilyl derivative. Detailed analytical procedures have been described elsewhere for Mur [3,4,7, 8,11] and for 3-OH FAs [2, 5,12,13]. The compounds of interest contain active... 

The trimethylsilyl group was the first to be developed and is widely used for the protection of serine and threonine (Table 6). Chlorotrimethylsilane, l,14 3,3,3-hexamethyldisilazane, and A(0-bis(trimethylsilyl)acetamide are commercially available reagents used for the conversion of alcohols into the corresponding trimethylsilyl derivatives.Furthermore, trimethylsilyl cyanide has been used to protect the side chains of serine, threonine, and ty-rosine.f This silyl protection allows the formation of A -carboxyanhydrides from H-Ser(TMS)-OH and H-Thr(TMS)-OH, and their application in peptide synthesis in the aqueous phase.f l The TMS group can be removed under various conditions, depending on the kind of functional group to which it is bound the TMS ethers are more stable than related amino or carboxy derivatives.These differences in stability allow the direct application of completely silylated hydroxy amino acids in peptide synthesis.b ... 

If the unknown is sufficiently volatile or can be made volatile by derivatization, then the LC/MS approach can be complemented by the use of GC/MS. A useful starting point in this regard is to make a trimethylsilyl derivative. Silylation is applicable to a wide range of nonsterically hindered functional groups, including alcohols, phenols, thiols, amines, oximes, and carboxylic acids (Table 6) 22,127 The dried sample (1 pg... 

The collection of carbon-14 and tritium-labeled steroids in GLC has been described by Kliman and Briefer (K8) with application to the analysis of testosterone in human plasma. Using the phenylmethylsiloxane polymer, OV-17, as liquid phase, Homing (H13) has achieved complete separation of testosterone and epitestosterone, both as free steroids and as trimethylsilyl derivatives. Figure 5 illustrates these separations. 

Determination of carbohydrates in biological materials by GC was reviewed by Clamp et al. [400] who present extensive tables of the previously published applications as well as the retention characteristics of various carbohydrate derivatives. The survey of applications strongly indicates that the use of trimethylsilyl derivatives is by far the most popular. The other very common procedures are acetylation and methylation. Because of the procedural simplicity, these main derivatives continue to be most commonly used. 

The application of the formation of trimethylsilyl derivatives to the study of silicate structures has been discussed with particular reference to the sodium silicate hydrates Na2H2Si04, H20 ( = 4, 5, and 8) and the mineral hemi-morphite, Zn4(0H)2Si207,H20. The technique is based on the extraction of silicate ions from crystalline and amorphous solids as their stable trimethylsilyl derivatives followed by separation by g.l.c. Although it was found necessary to control the conditions of the trimethylsilylation reaction very carefully, it was concluded that the method is universally applicable to all silicate structures, including those soluble in water. 

A new procedure described for the determination of cellulase activity is based on incubation of the enzyme with finely divided cellulose at pH 6.9 and determination of the D-glucose and cellobiose liberated as their trimethylsilyl derivatives by g.l.c. The method, although generally applicable, was specifically developed for measurement of cellulase activity in mixed enzyme preparations from sheep rumen contents the coefficient of variation of the assay was 2.4-4.5%. 

Although certain purine and pyrimidine nucleosides are adaptable to mass spectrometiic studies without prior substitution, the application of this technique to nucleotides and nucleosides containing more polar heterocycles (guanosine, cytidine) has been precluded because of their lower volatility. Conversion of these substances into their trimethylsilyl derivatives affords sufficiently volatile compounds which are conveniently studied by mass spectrometry. From a study of trimethylsilyl ethers of nucleosides it should be possible to determine the molecular weight or elemental composition from the M and M-15 peaks, in addition to other... 

Gas-liquid chromatography has been used to follow syntheses, anomeri-sations, glycosidations and other chemical reactions (Table III), but the major application has been to biological materials both for the qualitative and quantitative analyses of constituent monosaccharides and for structural studies of biopolymers. Trimethylsilyl derivatives are now widely... 

Gas Chromatography of Aromatic Acids as Their Trimethylsilyl Derivatives, Including Applications to Urine Analysis... 

Gas liquid chromatography (GLC) has found only limited application in lichen chemistry because most lichen substances are very polar and have low volatility. To overcome this problem, more volatile derivatives are used. Nishikawa et al. (1973) analyzed the low molecular weight carbohydrates of eight lichen species as their acetyl, trifluoroacetyl and trimethylsilyl derivatives by GLC under the following conditions Hj,... 

Another way to improve sensitivity is to use NMR methods such as INEPT and DEPT which, through scalar spin-spin coupling, will allow polarization to be transferred from the abundant high-/ protons to the rare low-/ Si nuclei. Some ten years ago, measurements of Si NMR spectra of trimethylsilyl derivatives by anploying the INEPT technique were reported . The authors suggested that the use of this technique will substantially shorten the measuring time and widen the scope of the analytical applications of Si NMR spectroscopy. 

Ureas and thioureas can be obtained in high yield with silicon isocyanate and isothiocyanate respectively thus providing another example of the growing application of silicon derivatives in organic chemistry. Trimethylsilyl derivatives have recently been used in acetylene chemistry for the preparation of p-vinyl-phenol and glycosy 1-N-heterocydies to which the nucleosides... 

Magnus and his group have discovered a new method of cyclization via quinodimethane intermediates, which avoids the problems associated with the well known methods involving benzocyclobutenes, dihydrothiophen dioxides, etc. The discovery was made after the observation that when the trimethylsilyl derivative (173) was treated with fluoride ion cyclization did not occur, only (174) was isolated. The cyclization to (175) is affected in good yield by heating (174) with acetic anhydride, and although the method is being developed for synthesis of Aspidosperma alkaloids, it promises to have much wider application. 

Two approaches are currently used for the preparation of volatile derivatives of the vitamin. The first approach is mostly based on the conversion of pantothenic acid and/or panthenol to acetyl (72) or trimethylsilyl derivatives (73). A simpler and more convenient approach for most applications seems to be the procedure based on the hydrolysis of the vitamin in acidic medium and analysis of the hydrolysis products. Pantothenic acid, its salts, and coenzyme A as well as its analogs undergo acid hydrolysis with formation of P-alanine and pantolactone. Panthenol breaks down to 3-amino-l-propanol (P-alanol) and pantolactone. For instance, P-alanine can be analyzed as the corresponding jv-trifluoroacetyl methyl ester or AMrifluoroacetyl butyl ester. Pantolactone is sufficiently volatile to be amenable to direct GLC (23,76,77), but it can also be analyzed as the corresponding trimethylsilyl ether, trifluoroacetyl, or isopropylurethane derivative (5,78). 

Dolhun, j. j., and J. L. Wiebers Mass Spectrometry of Trimethylsilyl Derivatives of Nucleoside and Dinucleotide Phenylboronates. Application to Oligonucleotide Sequence Analysis. J. Amer. Chem. Soc. 91, 7755 (1969). 

Trimethylsilyl derivative, a chemical derivative to increase substance volatility to facilitate chromatographic application, typical diagnostic mass mIz 73. 

Coward, R.F. and Smith, P. (1969a), The gas chromatography of aromatic acids as their trimethylsilyl derivatives, including applications to urine analysis. J. Chromatogr., 45, 230. 

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