Generation from amino acids

Pyrazines and pyrroles are generated from amino acids and sugars by heating. 

In a variation on the two-component cycloaddition reaction, a [3+3] strategy was reported whereby reaction of enantiomerically pure aziridines, generated from amino acids, with palladium trimethylenemethane complexes leads to a piperidine (Scheme 114). Yields ranged from 63% to 82% and the efficiency of the methodology was demonstrated by the four-step synthesis of (—)-pseudoconhydrin <2001SL1596>. 

A novel strategy for piperidine synthesis has been developed by Harrity and co-workers <01SL1596>. A variety of piperidines were synthesized in yields ranging from 63-82% by employing a [3+3] cycloaddition reaction between enantiomcrically pure aziridines 100 (generated from amino acids) and palladium trimcthylenemethane complexes (99). The efficiency of the methodology was demonstrated through a 4-step synthesis of (-)-pseudoconhydrine (101). 

Chapman, J.A. and Hardcastle, R.A. (1974) The staining pattern of collagen fibrils. 11. A comparison with patterns computer-generated from amino acid sequence. Conn. Tiss. Res., 2,151—1 59. 

More recent examples have employed a milder reagent system, triphenyl-phosphine and dibromotetrachloroethane to generate a bromo-oxazoline, which is subsequently dehydrohalogenated. Wipf and Lim utilized their method to transform intermediate 11 into the 2,4-disubstituted system of (+)-Hennoxazole k Subsequently, Morwick and coworkers reported a generalized approach to 2,4-disubstituted oxazoles from amino acids using a similar reagent combination, triphenylphosphine and hexachloroethane. ... 

Heteroatom rings, such as that found in quinoline derivatives, can be generated from amino-ketones with [hydroxy(tosyloxy)iodo]benzene and perchloric acid. Cyclic imines are converted to pyridine derivatives with NCS and then excess sodium methoxide. ... 

Petasis reported an efficient addition of vinyl boronic acid to iminium salts.92 While no reaction was observed when acetonitrile was used as solvent, the reaction went smoothly in water to give allyl amines (Eq. 11.54). The reaction of the boron reagent with iminium ions generated from glyoxylic acid and amines affords novel a-amino acids (Eq. 11.55). Carboalumination of alkynes in the presence of catalytic Cp2ZrCl2 and H2O affords vinylalane intermediates, which serve as nucleophiles in the subsequent addition to enantiomerically enriched... 

If this is an important production reaction for amino acids, what concentrations are required globally to generate the amino acid budget and should this represent a global concentration within the oceans The concentrations of HCN and NH4"1" are limiting in this process and HCN in particular is familiar from comet chemistry. Amino acids seem to be synthesised rather easily in the chemistry of a reducing atmosphere or from exogenous delivery. 

Ring B and the central three-carbon bridge forming the C ring (see Fig. 5.1) originate from the amino acid phenylalanine, itself a product of the shikimate pathway, a plastid-based process which generates aromatic amino acids from simple carbohydrate building blocks. Phenylalanine, and to a lesser extent tyrosine, are then fed into flavonoid biosynthesis via phenylpropanoid (C6-C3) metabolism (see Fig. 5.1). 

The catalytic core is the part that ultimately cleaves the ubiquitinated protein into small peptides anywhere from 3 amino acids to 32 amino acids long. The peptides generated are probably further hydrolyzed to generate free amino acids by other proteases and amino peptidases. The proteases that break down the products of the proteasome action include but not limited to Thimet oligo peptidase, tricorn protease, and tripeptidyl protease... 

It is important to appreciate that this principle of coupling-in-series underlies all biochemical pathways or processes, e.g. glycolysis, generation of ATP in the mitochondrion, protein synthesis from amino acids or a signal transduction pathway. Indeed, despite the fundamental importance of signalling pathways in biochemistry, a thermodynamic analysis of such a pathway has never been done, but the principles outlined above must apply even to signalling pathways. 

Ammonia lyases catalyze the enantioselective addition of ammonia to an activated double bond. A one-pot, three-step protocol was developed for the enantioselective synthesis of L-arylalanines 50 using phenylalanine ammonia lyase (PAL) in the key step (Scheme 2.20). After formation of the unsaturated esters 48 in situ via a Wittig reaction from the corresponding aldehydes, addition of porcine Ever esterase and basification of the reaction mixture resulted in hydrolysis to the carboxylic acids 49. Once this reaction had gone to completion, introduction of PAL and further addition of ammonia generated the amino acids 50 in good yield and excellent optical purity [22]. 

The sulfur extrusion method 21 has been extensively investigated for the synthesis of threo-3-methyllanthionine 25 however, in this case desulfurization was not used to generate the amino acid (either in free or protected form), but rather to form different sulfide-bridged cyclic peptides as precursors for the total synthesis of nisin (3). Development of synthetic methods in this area was particularly important in respect to the synthesis of nisin, since this lantibiotic contains four // eo-3-methyllanthionine residues. The synthesis proceeded from a protected f/zreo-3-methyl-D-cysteine in the N-terminal position and L-cysteine in the C-terminal position. 

The elucidation of the genetics and regulations of the Ehrlich pathway leading from amino acids to alcohols and the corresponding acids and esters—a pivotal metabolic route to flavours generated by traditional food fermentation processes—has attracted much research interest in the past. More recent inves-... 

Many important biomolecules are derived from amino acids. Glycine is a precursor of porphyrins. Degradation of iron-porphyrin (heme) generates bilirubin, which is converted to bile pigments, with several physiological functions. 

G-h Tao, He L, Sun N et al (2005) New generation ionic liquids cations derived from amino acids. Chem Commun 28 3562-3564... 

Amino acids are a class of biomolecules that make a significant contribution to the generation of metabolic energy. The fraction of metabolic energy obtained from amino acids varies greatly with the type of cell and with metabolic conditions. 

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