Amination amino reagents listed

The second group of hydroxy compound derivatization reactions includes acylation of OH groups with the formation of esters. The most important are listed below (for the table of physicochemical and gas chromatographic constants of acylation reagents refer to the entry Derivatization of Amines, Amino Acids, Amides, and Imides for GC Analysis). 

Acylation is one of the most popular derivatization reactions for primary and secondary amines (Figure 11.1). The reagents listed in Table 11.5 easily react with amino groups under mild reaction conditions. In the reactions of amines with acid anhydrides and acyl chlorides, it is usually necessary to remove excess reagent and byproduct acid because these compounds damage the GC column. 

Method. A standard amino-acid analyzer (Technicon or an equivalent) may be used. The reagents for development and the buffers are prepared as for analysis of amino acids. The analytical column (24 cm X 0.57 cm) consists of Zeocarb 226-4.5% DVB (average particle diameter, 24 jum). The two buffers are prepared by dissolving 8.74 g of potassium citrate, 60.36 g of potassium chloride, 10 ml of Brij and 100 ml of n-propanol (for the first buffer, 140 ml of n-propanol for the second buffer) in enough water to make a total volume of 11. The pH of each buffer is 7.4. For analysis the sample is adjusted to pH 7.4 and an aliquot portion is applied to the column. The column temperature is maintained at 43 °C for 103 min and is automatically switched to 75 °C for the remainder of the run. The flow-rate of the buffer is 42 ml/h. The first buffer is automatically replaced by the second after 120 min. The second buffer is necessary for the separation of tryptamine and cadaverine. The use of the increased temperature results in a shorter elution time. The retention times of some basic amino acids and amines are listed in Table 4.3. Absorption is monitored at 570 nm with a 1,5-cm flow cell. 

There are several types of chiral derivatizing reagents commonly used depending on the functional group involved. For amines, the formation of an amide from reaction with an acyl halide [147,148], chloroformate reaction to form a carbamate [149], and reaction with isocyanate to form the corresponding urea are common reactions [150]. Carboxyl groups can be effectively esterified with chiral alcohols [151-153]. Isocynates have been used as reagents for enantiomer separation of amino acids, iV-methylamino acids, and 3-hydroxy acids [154]. In addition to the above-mentioned reactions, many others have been used in the formation of derivatives for use on a variety of packed and capillary columns. For a more comprehensive list, refer to References 155-159. 

Enantiomeric Mannich bases may be obtained either by using optically active starting materials or by optical resolution of racemic derivatives. In the former case, the reactants are mostly provided by natural products, such as components of essential oils (e.g., camphor ), hormones, nucleic acids, employed as substrates, or a-amino acids - mainly used as amine reagents, etc. A list of optically active reactants reported in the literature is summarized in Table 12. 

Unfortunately, in proteins the number of reactive amino-acid side-chain functions is extremely limited and the peptide chain is notoriously inert toward most reagents. At best, the alcohols, thiols, phenols, amines and carboxylates of the protein could act as nucleophiles toward appropriate electrophilic centres of the substrate. Thus covalent bond formation between enzyme and substrate is limited in scope, and, to make the rather poor nucleophiles more efficient, further activating processes are needed. This activating action was found to occur in the numerous acid and base functions carried by all proteins. The types of functions found in proteins are listed in Table 1,... 

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