A-Aminoacrylic acid

While investigating the biomimetic formation of cysteine, Schmidt et al. 2331 added thiolates to N-protected chiral a-aminoacrylic acid derivatives (dehydropeptides). (235) was obtained in optical yields up to 90 %. 

Several 3-vinyl- and 1,3-divinyl-hydantoin derivatives have been prepared and converted to polymers having pendant hydantoin groups, e.g. (66) (B-74MI11100). Interesting spiro hydantoin polymers (67) are readily prepared from the very reactive 5-methylenehydantoin, hydrolysis of which cleanly produces polymers containing a-aminoacrylic acid units and having corresponding polyampholytic properties. 

Neither of the linkages formed by reactions (XXI) or (XXII) has been demonstrated in alkali-treated wool, but Patchornik and Sokolovsky (1964) and Bohak (1964) have demonstrated recently the presence of -iV-(D,L-2-amino-2 carboxymethyl)-L-lysine in hydrolyzates of proteins treated with alkali. This they attribute to the reaction of the -NH2 group of lysine residues with a-aminoacrylic acid residues formed from cystine residues by the 8-elimination reaction (Section V,A,5). Ziegler (1964) has shown that this amino acid residue is formed during the alkali treatment of wool in both the stretched and unstretched states. No assessment of the importance of these linkages in retaining set has yet been reported. 

The stress-strain characteristics of alkali-treated wools are variable (Satlow, 1959). Probably two main reactions affect the stiffness of the fibers conversion of disulfide bonds to thioether linkages and disruption of cystine residues to form a-aminoacrylic acid residues (Cuthbertson and Phillips, 1945). 

Polypeptide. The release of phosphogalactomannan, mannose, mannobiose and mannotriose from the polymer by alkali suggests that these saccharides are attached to a polypeptide (11). The amino acid composition of a peptidophosphogalactomannan preparation was determined (Table III). This table shows that approximately one-half of the amino acyl residues of the polypeptide are either seryl or threonyl residues and that the polypeptide has no aromatic or sulfur-containing amino acids. Treatment of the pol3nner with alkali followed by reduction of the a,3-dehydroamino-acyl residues formed resulted in a loss of all but 2 of the seryl residues and essentially all of the threonyl residues (Table IV). Furthermore, the number of alanyl residues increased from 4 to 8 and 4 residues of a-aminobutyric acid were obtained. These were derived from the reduction products of the a,3-dehydroserine (a-aminoacrylic acid) and a,3-dehydrothreonine (a-aminocrotonic acid), respectively, following 3-elimination of saccharides from seryl... 

Cysteine synthesis in bacteria proceeds via a-aminoacrylic acid bound to the enzyme as a Schiff base with pyridoxal phosphate (Cook and Wedding, 1976). Partially purified cysteine synthase from spinach (Schmidt, 1977a) and Chlorella (Schmidt, 1977b) catalyzes an exchange of sulfide into cysteine, consistent with the above mechanism. The exchange of acetate into OAS that would be expected due to formation of the proposed enzyme intermediate was not tested. 

Certain early speculations about the mechanism of formation of cystine from methionine contained shrewd inferences ivhich later work has shown to be correct in part. Brand and co-workers- first postulated transfer of the sulfur from a 4-carbon to a 3-carbon chain. These workers suggested that homocysteine condensed with a-aminoacrylic acid to form an intermediate compound which was cleaved to yield cysteine. Toennies suggested the direct transsulfuration between methionine... 

The increase in the extinction at this wavelength is related to the formation of a-amino-acrylic acid. The ultraviolet spectrum of a-aminoacrylic acid has been shown to have a maximum at 241 nm. This result could be explained if it is assumed that a nucleophilic attack (jS-elimination) of the alkoxide moiety (sugar residue) of Fraction B occurred to give a dehydro derivative (Fig. 4). The fact that glucose is released by alkaline treatment sug-... 

The unsaturated intermediate formed in this manner may dissociate off a-aminoacrylic acid, which immediately reacts spontaneously with water to form pyruvic acid and ammonia. This is the essence of the media-nism of the serine deaminase reaction. It is shown structurally in F. 3. The same mechanism applies to the deamination of other /8-hydroxyaniino acids, such as threonine, discussed in the next section. 

The a-aminoacrylic acid produced gives rise to the following spontaneous reactions ... 

These reactions are explained by the presence of an enzyme of yet unknown nature in the enzyme preparation which catalyzes the oxidation-reduction between cysteine and a-aminoacrylic acid (or iminopyruvic acid). 

Rothstein, E. Experiments in the Synthesis of Derivatives of a-Aminoacrylic Acid from Serine and N-Substituted Serines. J. Chem. Soc. 1949, 1968. 

In structural terms, djenkolic has two units of L-cysteine joined through a CH2 group linked to sulfur atoms. It has also been found in seeds of Albizzia lophanta and Parkia speciosa32 and, as noted earlier, is the source of CS2 in Mimosa pudica (Section 11.1.2.2.2). An enzyme in A. lophanta seeds converted djenkolic acid to an unstable material with a leek-like odor, methylene dithiol 39.92 This was presumably an elimination of aminoacrylic acid 28 via intermediates 37 and 38 (Scheme 13). The methylene dithiol decomposed to H2S and possibly, thioformaldehyde, CH2S the latter might be a source for polysulfides. 

Peptides that contain 2-aminoacrylic acid and 2-aminocrotonic acid groups absorb in the ultraviolet region, the former at a wavelength maximum of 240 nm, and the latter with a more generalized absorption. At 240 nm, the molar absorptivity is the same (4,200) for the two... 

P-Elimination and then replacement reaction of an a-amino acid with a nucleophile is very attractive from the viewpoint of synthetic organic chemistry because various P-substituted alanines may be prepared from a simple a-amino acid, such as serine, and nucleophiles. A reaction catalyzed by tryptophan synthase - the formation of tryptophan from serine and indole - is one of the most well-known P-elimination and replacement reactions (Scheme 2.7). Here, an aldimine Schiff base is derived from reaction of the enzyme-bound PLP with serine, which then dehydrates to give the Schiff base of PLP with 2-aminoacrylate. Indole then adds to the vinyl Schiff base, generating tryptophan after lysine aminolysis of the Schiff base product. 

The Hiyama aminoacrylate synthesis " is the synthesis of alkyl ester of 3-aminoacrylic acids or derivatives by aldol-type condensation of nitriles with ester in the presence of a base such as (i-Pr)2NH. 

The mass spectra of the cysteinyl conjugate 12. illustrate the complementary nature of positive and negative ion analysis (Figure 17). The protonated molecular ion is evident in the positive ion spectrum along with a major fragment ion at m/z 388 for a protonated thioacid. The ion at m/z 388 arises from loss of 2-aminoacrylic acid from the molecular ion. The anion of the thioacid is the highest mass ion observed in the negative ion spectrum, which provides little structural information otherwise. 

Reaction of 2,3-diphenylcyclopropenone with A-alkylbenzylidenamines in refluxing pro-pan-2-ol produced indenyl benzamide 26, but-3-ene-l, 2-dione 27, and 3-aminoacrylic acid 28. ... 

Scission of the side chain leaves an Ai ion which takes up a pioton to give indole from tryptophan (as with tryptophanase) or phenol from tyrosine (as with 3-tyrosinase). The side chain of the original molecule is left as the pyridoxal phosphate complex of aminoacrylic acid, and on hydrolysis the aminoacrylic acid tautomerizes to the imine of pyruvic acid which is hydrolyzed to pyruvic acid and ammonia ... 

The pyridoxal phosphate complex of aminoacrylic acid can also be formed from serine by loss of an OH radical in a manner analogous to loss of the. 4.r" radical depicted above. This complex contains a reactive double bond to which the reactive /3-hydrogen of indole can add, giving a complex which on hydrolysis yields tryptophan. Such a mechanism is in accord with the known facts on tryptophan biosynthesis (cf. 858, and previous discussion, p. 41). 

With the exception of diaryl ketones, all aldehydes and ketones undergo the 4CC as the carbonyl component (4). Note that the derivatives of the a-oxocarboxylic acids react very well as the carbonyl components (4), whereas the derivatives of the 3-oxocarboxylic acids may form the resonance-stabilized derivatives of 3-aminoacrylic acid, such as ethyl 3-aminocrotonate (45), which can even be used as the amine component (43) of the Ugi reaction. ... 

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