Derivatization acylation

The lipid is dissolved in pyridine and a 10% excess of methaneboronic acid is added. The mixture is left at room temperature for 10 min. The nature of the starting material governs whether or not further derivatization (acylation, silylation or esterification) is necessary. If it is, then the solution is first evaporated to dryness in a stream of nitrogen otherwise the sample may be analysed directly by GC or GC-MS [51, 79],... 

Bei der Herstellung von Aldehyden iiber die 1-Acyl-imidazole wird die Carbonsaure mit l-[Imidazolyl-(l)-carbonyI]-imidazol umgesetzt und das erhaltene Imidazol-Derivat ohne Isolierung zum Aldehyd reduziert5 ... 

Bei 2,2,2-Trichlor-athanolen bzw. deren O-Sulfonyl- bzw. O-Acyl-Derivaten wird in saurem Medium in einer Sekundar-Reaktion teilweise unter Abspaltung von Sulfonsaure bzw. Carbonsaure das 1,1-Dichlor-athen-Derivat erhalten ... 

Pyridine and BF3 in methanol are hazardous and must be used only in a well-ventilated hood. A solvent partition after acylation helps remove residual pyridine from the sample. Material Safety Data Sheets for the derivatizing agents should be reviewed and kept readily available. 

A different MS-based ee-assay makes use of a proline-derived mass-tagged acylating agent.95 In the course of derivatization it is necessary that some degree of kinetic resolution comes about. The sensitivity of the method was reported to be 10% ee. It can also be applied to the reaction of a prochiral compound lacking enantiotopic groups, as in the transformation of acetophenone to phenylethanol. 

The amine containing side chains in lysine, arginine, and histidine typically are exposed on the surface of proteins and can be derivatized with ease. The most important reactions that can occur with these residues are alkylation and acylation (Figure 1.8). In alkylation, an active... 

Cysteine sulfhydryls and cystine disulfides may undergo a variety of reactions, including alkylation to form stable thioether derivatives, acylation to form relatively unstable thioesters, and a number of oxidation and reduction processes (Figure 1.10). Derivatization of the side chain sulfhydryl of cysteine is one of the most important reactions of modification and conjugation techniques for proteins. 

Citraconic anhydride (or 2-methylmaleic anhydride) is a derivative of maleic anhydride that is even more reversible after acylation than maleylated compounds. At alkaline pH values (pH 7-8) the reagent effectively reacts with amine groups to form amide linkages and a terminal carboxylate. However, at acid pH (3-4), these bonds rapidly hydrolyze to release citraconic acid and free the amine (Figure 1.86) (Dixon and Perham, 1968 Habeeb and Atassi, 1970 Klapper and Klotz, 1972 Shetty and Kinsella, 1980). Thus, citraconic anhydride has been used to temporarily block amine groups while other parts of a molecule are undergoing derivatization. Once the modification is complete, the amines then can be unblocked to create the original structure. 

The phosphonium and carbenium salts are efficient reagents for activating and coupling A-alkoxycarbonylamino acids as well as peptide acids. However, the requirement for tertiary amine to effect the reaction has several implications. The base renders hydroxyl groups subject to acylation. Hence, the side chains of serine and threonine and any hydroxymethyl groups of a resin that have not been derivatized... 

The advantage of trimethylsilyl (TMS) derivatives lies in the simplicity of the derivatization procedure, which is carried out by the addition of N,0-bis(trimethylsilyl)trifluoroacetamide (BSTFA) in acetonitrile and heating for approximately 2 h at 150 °C under anhydrous conditions in a sealed tube. However, there may be problems owing to the formation of multiple derivatives of each amino acid. Another technique involves the formation of n-butyl esters of the amino acids and their subsequent trimethylsilylation by a similar procedure. The n-butyl esters are formed by heating the amino acids for 15 min in n-butanol and HC1 and these are then converted to the A-TMS-n-butyl ester derivatives. A-acyl amino acid alkyl esters are commonly used. Acetylation of the butyl, methyl or propyl esters of amino acids,... 

An easily accessible DA CSP derived from L-A-(2-naphthyl)valine (80) was used to separate appropriately derivatized amines, amino alcohols and thiols, derivatization consisting of N-, O- and 5-acylation with 3,5-dinitrobenzoyl chloride or 3,5-dinitrophenyl... 

A-Acylation can be preformed with esters of A-hydroxysuccinimide A-succinimidyl 4-nitrophenylacetate (95) was used to derivatize the primary and secondary amines conferring bad odor to water253. Derivatization of amines with the ester of A-hydroxysuccinimide with A-(quinolin-6-yl)carbamic acid (96) gives excellent yields of... 

Pre-column derivatization with either 134 or 135 followed by CZE and LIF detection was proposed for amino acids. The amino group of the analyte displaces the succinyloxy moiety of the reagent yielding a carboxamide325. See also Section IV.D.3.C for other acylating reagents derived from A-hydroxysuccinimide (95 and 96). 

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