Diamino acid

Diaminosaure, /. diamino acid. Diaminschwarz, n. diamine black. 

A convenient synthesis of , -diamino acids from azlactones involves catalytic hydrogenolysis of a hydroxylamino function over palladium-on-carbon 141). 

The asymmetric synthesis of 2,3-diamino acids can be accomplished by the addition of chiral enolates to prochiral imines. For example, reaction of morpholine-2-one 103, derived from (S)-phenylglycinol, with N-benzyl ben-zaldimine in the presence of pyridine and para-toluenesulfonic acid at high... 

On the other hand, following the same sequences from the differently protected serine-derived nitrone 168, through the formation of hydroxylamines 169, C2 epimers of carboxylic acid and aldehydes are obtained, i.e., (2S,3R)-170 and (2S,3R)-171. Moreover, the syn adducts 164 were exclusively obtained in the addition of Grignard reagents to the nitrone 163, whereas the same reactions on nitrone 168 occurred with a partial loss of diastereoselectivity [80]. Q, j6-Diamino acids (2R,3S)- and (2R,3R)-167 can also be prepared from the a-amino hydroxylamines 164 and 169 by reduction, deprotection and oxidation steps. The diastereoselective addition of acetylide anion to N,N-dibenzyl L-serine phenyhmine has been also described [81]. 

With the exception of cystine, a, a -diamino acids represent a class of compounds not found naturally in biological samples. However, it should be noted that such compounds have been isolated previously from certain... 

We might think that the Murchison meteorite would have been studied thoroughly enough in the years since its arrival on Earth. But the results obtained always depend on the performance of the technical resources available in this case, the analytical methods and the apparatus. Thus, it is not really surprising that a new class of amino acid has been discovered in Murchison material diamino acids, such as DL-2,3-diaminopropionic acid, DL-2,4-diaminobutanoic acid etc. These were identified using a new enantioselective GLPC/MS method, which is also being used in analysis of material from the Rosetta mission. 

As in all cases already mentioned, diastereoselective addition of Grignard reagents to j3-amino nitrones (a-aminoalkyl nitrones) is a key step in the stereo-controlled syntheses of O.,j3-diamino acids (Scheme 2.141) (565, 566), of unsym-metrical a-amino hydroxylamines and 1,2-diamines (Scheme 2.142) (209, 567). 

J Leclerc, L Benoiton. On the selectivity of acylation of unprotected diamino acids. Can J Chem 46, 1047, 1968. 

In an original application, Yasuda et al have used both l-AAO and d-AAO, and L-lysine oxidase to oxidize o ,Ci -diamino acids. The reactions produce the expected a-keto w-amino acid products, but these then spontaneously cyclize to form cyclic a-imino acids. These compounds are then substrates for the authors recently discovered A methyl amino acid dehydrogenase (NMAADH) from Pseudomonas putida, producing the pure L-cyclic amino acid (Scheme 5). 

In connection with the synthesis of cytohalasin B, a pyrrole derivative 13 was prepared from methyl (5)-3-aminophenylbutyrate (78JA7775). In connection with the synthesis of l,2,4-triazolo[4,3-a]pyrazine derivatives with human Renin inhibitor activity, a /3,y-diamino acid derivative was transformed into a pyrrolidin-2-one (91JMC151). 

For the unsubstituted compound 197a-Me the 2R/2S ratio was only 5.6 1 [ 10b, c], yet in this case the absolute configuration was checked by X-ray crystal structure analysis. The a-azidoesters 197-R were converted to the a,)3-diamino acids 198-R as described above, i.e. by catalytic hydrogenation over palladium on charcoal and hydrolysis of the ester group (Scheme 58) [10b, c, 62]. Saponification was not necessary for the benzyl esters 197a,b,i-Bn. 

The a-azidoesters 197-Me are not only precursors for a,)3-diamino acids 198 but could also be used to prepare 2 -substituted aminocyclopropanecarboxylic acid (ACC) derivatives 203 [10b, c, 62] (Scheme 60). Upon treatment with freshly prepared lithium methoxide in THF and subsequent hydrolysis (HCI), the a-... 

This FAD-dependent enzyme [EC 1.13.12.2] catalyzes the reaction of L-lysine with dioxygen to produce 5-aminopentanamide, carbon dioxide, and water. Other diamino acids can serve as substrates as well. 

As the result of hydrolysis a complex mixture of all, or nearly all, the previously mentioned units is obtained. These have been isolated by various methods based upon the fractional crystallisation of the compounds themselves, or of their copper, silver and other salts. Only when one or more of the amino acids occurred in somewhat large amounts was their isolation and characterisation effected their amount seldom reached a value higher than 20 per cent, of the total quantity and the remainder was represented by uncrystallisable syrups of unknown nature. A great advance was made when Drechsel discovered that the protein molecule contained diamino acids as well as monoamino acids, and to Kossel and Kutscher we owe our chief knowledge concerning their isolation and estimation. Emil Fischer, in igoi, by his... 

By this method of extracting the esters from their hydrochlorides, neither that of tyrosine, which remains behind combined with alkali, nor those of the diamino acids, which are soluble with difficulty in ether, are obtained. This is advantageous for the subsequent process of separation, but the method has the disadvantage that the whole quantity of esters is not taken up by the ether on account of their destruction by the alkali. In order to avoid their loss, the mass of carbonate is treated with excess of hydrochloric acid and evaporated down, the potassium... 

Only in a few cases has this compound been isolated from the products of hydrolysis of proteins, since its separation is extremely laborious. It can only be effected after all the other amino acids have been removed by crystallisation and by the ester method, and after the diamino acids have been precipitated by phosphotungstic acid. From the last mother-liquors it is obtained by crystallisation, and is best identified in the form of its /8-naphthalene sulpho-derivative. 

The separation and estimation of the two main groups of amino acids can be carried out in one experiment, instead of separately as described. The protein is hydrolysed by sulphuric acid, the tyrosine, cystine and diaminotrioxydodecanic acid are removed by crystallisation, and the diamino acids are precipitated by phosphotungstic acid. From this precipitate they are obtained by decomposition with baryta, and they are then separated by means of their silver compounds by Kossel, Kustcher and Patten s method. The filtrate from the phosphotungstic acid precipitate is freed from the excess of phosphotungstic acid by means of baryta, and the solution is treated by Fischer s ester method for the monoamino acids. 

The combination of the two processes is generally only carried out when the amount of protein available is limited they require very different quantities of material thus, the diamino acids can be determined in 25 to 50 grammes of protein with considerable accuracy, whereas the monoamino acids can only be determined with fair accuracy when 250 to 500 grammes of protein can be used. On the whole, it is not... 

The protamines are built up almost exclusively of diamino acids, salmine containing over 80 per cent, of arginine. Only small amounts of monoamino acids are present in them, and even these amounts may be due to impurity, for fish sperm only at maturity is made up of protamine and nucleic acid, whereas at other times histone takes the place of protamine, and histones contain less diamino acids. Kossel and Dakin s analysis appears to show us a quantitative result in the case of salmine. 

The histones contain about 30 per cent, of diamino acids, and only in the case of thymus-histone has an estimation been made of the monoamino acids. They were supposed to be intermediate compounds between protamines and other proteins, and this supposition is confirmed by the results of analysis. 

The presence of diamino acids in all proteins led Kossel to suppose that there was a protamine nucleus (t.e, of diamino acids) in all proteins the more recent work, especially that by Osborne and Clapp on the gliadins, where the diamino acids are present in such small amounts, though it supports the theory, yet suggests that proteins may exist in which it is not present, more especially if the view of Emil Fischer be taken that all the proteins we know, even the crystalline ones, are still mixtures of several proteins. The isolation of complexes containing only diamino acids from proteins, where they are combined together, will be the only proof of a protamine nucleus in a protein molecule. 

The synthesis of the diamino acids, in comparison with that of the monoamino acids, is very much more difficult and has only been achieved within the last few years. 

Ornithine or a, h-diamimrvalerianic Acid.—In 1877 JafTe obtained from the urine of birds, which he had fed with benzoic acid, dibenzoyl ornithine or ornithuric acid, and from this substance he prepared ornithine chloride. He regarded it as a diaminovalerianic acid, the first known representative of the series of diamino acids, but only in 1898 was the position of the two amino groups definitely determined by Ellinger, who obtained putrescine from it by putrefaction the identity of putrescine with tetramethylenediamine had been previously shown by... 

The expected synthesis of a-S-diaminovalerianic acid, which was attempted by Willstatter in 1900, by the action of ammonia upon a-B-dibromovalerianic acid, led to the synthesis of a-pyrrolidine-carboxylic acid, and only in the following year was the synthesis of this important naturally occurring diamino acid accomplished by E. Fischer. He made use of Gabriel s phthalimide method with a slight modification and obtained ornithine by the following series of reactions —... 

---