Alanine reactions

Simple esters cannot be allylated with allyl acetates, but the Schiff base 109 derived from o -amino acid esters such as glycine or alanine is allylated with allyl acetate. In this way. the o-allyl-a-amino acid 110 can be prepared after hydrolysis[34]. The Q-allyl-o-aminophosphonate 112 is prepared by allylation of the Schiff base 111 of diethyl aminomethylphosphonates. [35,36]. Asymmetric synthesis in this reaction using the (+ )-A, jV-dicyclohex-ylsulfamoylisobornyl alcohol ester of glycine and DIOP as a chiral ligand achieved 99% ec[72]. 

Miscellaneous Reactions. Sodium bisulfite adds to acetaldehyde to form a white crystalline addition compound, insoluble in ethyl alcohol and ether. This bisulfite addition compound is frequendy used to isolate and purify acetaldehyde, which may be regenerated with dilute acid. Hydrocyanic acid adds to acetaldehyde in the presence of an alkaU catalyst to form cyanohydrin the cyanohydrin may also be prepared from sodium cyanide and the bisulfite addition compound. Acrylonittile [107-13-1] (qv) can be made from acetaldehyde and hydrocyanic acid by heating the cyanohydrin that is formed to 600—700°C (77). Alanine [302-72-7] can be prepared by the reaction of an ammonium salt and an alkaU metal cyanide with acetaldehyde this is a general method for the preparation of a-amino acids called the Strecker amino acids synthesis. Grignard reagents add readily to acetaldehyde, the final product being a secondary alcohol. Thioacetaldehyde [2765-04-0] is formed by reaction of acetaldehyde with hydrogen sulfide thioacetaldehyde polymerizes readily to the trimer. 

Other examples are glycine — formaldehyde, alanine — acetaldehyde, valine — isobutyraldehyde, phenylalanine — phenylacetaldehyde, and methionine — methional (106). Products such as dried skim milk, dried eggs, and dehydrated vegetables and fmits are particularly susceptible to deteriorative flavor changes ascribed to this reaction (Table 10). 

Enzymes, measured in clinical laboratories, for which kits are available include y-glutamyl transferase (GGT), alanine transferase [9000-86-6] (ALT), aldolase, a-amylase [9000-90-2] aspartate aminotransferase [9000-97-9], creatine kinase and its isoenzymes, galactose-l-phosphate uridyl transferase, Hpase, malate dehydrogenase [9001 -64-3], 5 -nucleotidase, phosphohexose isomerase, and pymvate kinase [9001-59-6]. One example is the measurement of aspartate aminotransferase, where the reaction is followed by monitoring the loss of NADH ... 

Enzymatic Process. Chemically synthesized substrates can be converted to the corresponding amino acids by the catalytic action of an enzyme or the microbial cells as an enzyme source, t - Alanine production from L-aspartic acid, L-aspartic acid production from fumaric acid, L-cysteine production from DL-2-aminothiazoline-4-catboxyhc acid, D-phenylglycine (and D-/> -hydtoxyphenylglycine) production from DL-phenyUiydantoin (and DL-/)-hydroxyphenylhydantoin), and L-tryptophan production from indole and DL-serine have been in operation as commercial processes. Some of the other processes shown in Table 10 are at a technical level high enough to be useful for commercial production (24). Representative chemical reactions used ia the enzymatic process are shown ia Figure 6. 

In some cases, Bucherer s process is employed also, but strict control of reaction conditions is needed because the reactivity of formaldehyde is different from other aldehydes. DL-Alanine (212) is produced by either Strecker s or Bucherer s process from acetaldehyde. 

Reactions with OC-Amino Acids. On heating two moles of an a-amino acid, such as alanine, in the presence of a tetraalkyl titanate and an alcohol, reaction that gives a 2,5-pipetazineclione and an oxytitanate occurs (36). 

The metabohcaHy active form of pantothenic acid is coen2yme A. Pantothenic acid is produced only by microorganisms, starting from (R)-pantoate (22) and P-alanine. (R)-Pantoate is synthesi2ed by a set of en2ymatic reactions, as follows (63,64) ... 

The other main reaction in this class is the Dieckmann-type cyclization of the intermediates (163) from 4(6)-halo-5-ethoxycarbonylpyrimidines with AC-substituted /3-alanine esters and nitriles, and related compounds, to give 5,6,7,8-tetrahydro-5-oxopyrido[2,3-[Pg.221]

The member of this class which has been studied most thoroughly is 2-benzylidene-4-methyl-5(2 )-oxazolone (57). This compound may be prepared by ring closure of either 3-bromo-2-phenylacetamido-propionic acid or A-(a-halophenylacetyl)alanine (56) [Eq. (30)]. These reactions presumably proceed via unstable halogeno-5(4IT)-oxazolones, which rapidly lose hydrogen halide. 

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