Heterocycles amino acids made

The FTT synthesis has given less impressive results, having produced only 11 definite and 8 tentative matches (Yoshino et al., 1971 Hayatsu et al., 1971). Total yields were 0.01-0.1%, much less than in the Miller-Urey synthesis (2%), though similar to the abundance in meteorites ( 0.1% of the organic carbon). The product. distribution again was fairly similar to that in meteorites, but also included aromatic or heterocyclic amino acids such as tyrosine and histidine that cannot be made by conventional Miller-Urey syntheses. In the present context, that is a liability rather than an asret, since these amino acids have not been found in meteorites either. 

The p-carboline alkaloids are heterocyclic amines, biosynthesized from combination of five- and six-ringed (i.e., cyclic) carbon structures, containing an amine group, p-carboline is made up of planar tricyclic ring structures derived from L-tryptophan (i.e., a-aminoindole-3-propinoic acid), a neutral heterocyclic amino acid containing essentially an indole ring system. The shikimic acid... 

Just as proteins are biopolymers made of amino acids, nucleic acids are biopolv-mers made of nucleotides joined together to form a long chain. Each nucleotide is composed of a nucleoside bonded to a phosphate group, and each nucleoside is composed of an aldopentose sugar linked through its anomeric carbon to the nitrogen atom of a heterocyclic purine or pyrimidine base. 

Effect of Phospholipids on Reaction Volatiles. As would be expected, the inclusion of phospholipids in the reaction mixtures produced many volatiles derived from lipid degradation these included hydrocarbons, alkylfurans, saturated and unsaturated alcohols, aldehydes and ketones. However, two other important observations were made. First, the concentrations of most of the hetero- cyclics, formed by the amino acid + ribose Maillard reaction, were reduced. For most of the major volatiles this reduction was of the order of 40 - 50%, but in the case of thiophenethiol and methyl- furanthiol the reduction was over 65%. This appears to support the findings that in meat and coconut, lipids exert a quenching effect on the amount of heterocyclic compounds formed in Maillard reactions during heat treatment (11,12). Second, and perhaps more important, the addition of phospholipid to the reaction mixtures resulted in the production of large amounts of compounds derived from the interaction of the lipid or its degradation products with Maillard reaction intermediates. 

Aminals are another class of saturated heterocycles that form very readily under thermodynamic control aminals are nitrogen analogues of acetals. They are usually made by refluxing a 1,2-diamine with an aldehyde in toluene (no acid catalyst is needed because the nitrogens are very nucleophilic), and this makes a very useful way of forming a chiral derivative of an achiral aldehyde. Here is an example the diamine is made from the amino acid proline. The product has a new chiral centre, and it forms as a single diastereoisomer because the phenyl ring prefers to be on the exo face of the bicyclic system (see Chapter 33). 

To make rosoxacin two heterocyclic systems must be constructed. Workers at the pharmaceutical company Sterling decided to build the pyridine in an ingenious version of the Hantzsch synthesis using acetylenic esters on 3-nitrobenzaldehyde. The ammonia was added as ammonium acetate. Oxidation with nitric acid made the pyridine, hydrolysis of the esters and decarboxylation removed the acid groups, and reduction with Fe(TT) and HC1 converted the nitro group into the amino group required for the quinolone synthesis. 

We have introduced you to this chiral auxiliary before any other because it is more commonly used than any other. It is a member of the oxazolidinone (the name of the heterocyclic ring) family of auxiliaries developed by David Evans at Harvard University, and is easily and cheaply made from the amino acid (S)-valine. Not only is it cheaply made it can also be recycled. The last step of the route above, transesterification with benzyl alcohol, regenerates the auxiliary ready for re-use. synthesis of Evans s oxazolidinone chiral auxiliary from (S)-valine NH2 NH2... 

In 1971 when Patterson et al. made this suggestion, the presence in amino acid pyrolysates of the /V-heterocyclic amines and the inordinately high mutagenicity of several of them were unknown. 

Native and microcrystalline cellulose precoated plates are used in the life sciences for the separation of polar compounds (e.g. carbohydrates, carboxylic acids, amino acids, nucleic acid derivatives, phosphates, etc) [85]. These layers are unsuitable for the separation of compounds of low water solubility unless first modified, for example, by acetylation. Several chemically bonded layers have been described for the separation of enantiomers (section 10.5.3). Polyamide and polymeric ion-exchange resins are available in a low performance grade only for the preparation of laboratory-made layers [82]. Polyamide layers are useful for the reversed-phase separation and qualitative analysis of phenols, amino acid derivatives, heterocyclic nitrogen compounds, and carboxylic and sulfonic acids. Ion-exchange layers prepared from poly(ethyleneimine), functionalized poly(styrene-divinylbenzene) and diethylaminoethyl cellulose resins and powders and are used primarily for the separation of inorganic ions and biopolymers. 

The target can be best disconnected into three fragments at the amide bonds. The aminopyridine can be made by the standard methods of heterocycle synthesis (chapter 30), so we are more interested in the other two chiral fragments. The middle one is an amino acid, and you should recognize it as a member of the chiral pool, (S)-glutamic acid, so this poses no problem of synthesis. (Though it will need to be appropriately protected to form the correct amide). 

Several amino acids, the building block of life, are made of heterocycles. Histidine has an imidazole tryptophan has an indole yet proline has a pyrrolidine. 

Progress in the enantioselective synthesis of amino acids has been made, most notably this year by Seebach s research group. Simple amino acids, such as (S)-alanine, are converted into cis-(29) and trans-(29) imidazolidinones. These heterocycles undergo deprotonation to afford chiral enolates, alkylation of which takes... 

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