Amino acids, acetyl derivatives salts

Inactivation and Removal of Viruses. In developing methods of plasma fractionation, the possibiHty of transmitting infection from human vimses present in the starting plasma pool has been recognized (4,5). Consequentiy, studies of product stabiHty encompass investigation of heat treatment of products in both solution (100) and dried (101) states to estabHsh vimcidal procedures that could be appHed to the final product. Salts of fatty acid anions, such as sodium caprylate [1984-06-17, and the acetyl derivative of the amino acid tryptophan, sodium acetyl-tryptophanate [87-32-17, are capable of stabilizing albumin solutions to 60°C for 10 hours (100) this procedure prevents the transmission of viral hepatitis (102,103). The degree of protein stabilization obtained (104) and the safety of the product in clinical practice have been confirmed (105,106). The procedure has also been shown to inactivate the human immunodeficiency vims (HIV) (107). 

C-Alkylation of the sodio derivative is accomplished by a technique similar to the alkylation of malonic ester. Primary halogen compounds, quaternary ammonium salts,and an alkene oxide have been used as alkylating agents. Alkylation by secondary halides has been less successful. Hydrolysis of the substituted esters to acetylated amino acids is described for leucine (64%) and phenylalanine (83%). Hydrolysis with deacylation has been used to prepare histidine (45%) and phenylalanine (67%). Glutamic acid (75%) is obtained from substituted acylaminomalonates prepared by the Michael condensation of methyl acrylate and the acylated amino esters. ... 

The acid reduces ammoniacal. silver nitrate solution, and with sodium nitrite gives a yellow diazo-compound, which couples with resorcinol to give a bluish-red dye. Wren dissolved in sodium hydroxide and treated with acetic anhydride, the amino-acid yields an acetyl derivative, which separates in colourless prisms from water, and yields amorphous calcium and magnesium salts. ... 

This acid is obtained bj reducing the corresponding nitro-acid (p. 171) with ferrous chloride and alkali. It is instantly soluble in an excess of normal hydrochloric acid, and with sodium nitrite gives an orange-brown solution which couples with j8-naphthol. The monohydrochloride of the arsinic acid crystallises in clear prisms calcium, magnesium and barium salts may be obtained. The acetyl derivative separates in small prisms, sparingly soluble in boiling water, readily soluble in acids, sym.-Carbamide of 3-amino-4-piperidinophenylarsinic acid,... 

N-Acetylation of basic amino acids. The reagent reacts with an aqueous solution of the copper salt of a basic amino acid to give the N-acetyl derivative.1 The procedure is superior to the usual synthesis in which acetic anhydride is used because the reaction goes to completion. As applied to L-lysine, the method is simple and gives better yields of pure e-N-acetyl-L-lysine. Excess cupric carbonate is added to a boiling aqueous solution of L-lysine (0.1 mole) and the solution is filtered and cooled to 25° and treated with sodium bicarbonate, p-nitrophenylacetate, and a few milliliters of ethyl acetate to keep the acetate in solution. After stirring for 15 hrs the copper salt which separates is filtered, suspended in water, and freed of copper with H2S. The solution is evaporated to dryness and the N-acetyllysine crystallized from water-ethanol. 

In 1909, 4-amino-6-methyl-l,3,5-triazin-2-ol was obtained by cyclization of (acetylcarbamimi-doyl)urca under basic conditions.443 Subsequently, several new processes based on acylated dicyanodiamides were developed.444-447,449 Thus, when acyldicyanodiamides 1 are heated to reflux in 2-ethoxyethanol, 4-amino-1,3,5-triazin-2-ols 2 are obtained in crude yields of 60 to 100%.444,445 Catalytic amounts of amine salts significantly accelerate this reaction. After selective acid hydrolysis of acyldicyanodiamides, (acylcarbamimidoyl)ureas 3 are obtained which can also be cyclized to the 1,3,5-triazines 2. These reactions are carried out in excess sodium hydroxide solution and provide the triazines in 90 to 99% yield.443,444,446 447 Cyclization of 1-acylbiurets 4, prepared by acid hydrolysis of (acylcarbamimidoyl)ureas 3, is effected by treatment with potassium hydroxide solution.444,448 While the benzoyl derivative 3 (R = Ph) yields the corresponding l,3,5-triazine-2,4-diol 5 (R = Ph) in quantitative yield, the acetyl derivative 3 (R = Me) cyclizes only partially to the corresponding triazinediol 5 (R = Me).448... 

Needless to say that the product of synthesis is a racemate, from which the L and D enanthiomers have to be separated. Of the numerous methods of resolution a fairly general approach, enzyme catalyzed hydrolysis of acetyl-amino acids should be given special consideration. Acylase greatly enhances the rate of removal by hydrolysis of the acetyl group from L-amino acids, but leaves the (negligible) hydrolysis rate of the acetyl-D-amino acid unaffected. Hence, after completion of the hydrolysis, concentration of the neutral solution and dilution with absolute ethanol yields the L-amino acid, a dipolar ion insoluble in alcohol, while the salt of the unchanged acetyl derivative of the D-enanthiomer remains in solution. 

In view of the presence in azlactones of type VI of a labile a-hydrogen atom it is not surprising that optically active substances of this type racemize very readily. So rapid is the process that an optically active azlactone never has been isolated. This property is the basis of two effective methods for the racemization of amino acids. - > In one, the amino acid is heated in glacial acetic acid with 2 moles of acetic anhydride. In the other, the sodium salt of the amino acid in aqueous solution is treated with a large excess of acetic anhydride at room temperature. The racemic acetyl derivative of the amino acid is produced by either procedure. 

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