2-Methylbutanoic acid derivatives

Few studies have been conducted to determine organic residues in spent foundry sand and leachates from disposal sites. It is reported that several organic compounds are present in the spent foundry sand but have concentrations below the regulated toxicity characteristic limits. Organic compounds of concern include benzoic acid, naphthalene, methylnaphthalenes, phenol, methylenebisphenol, diethylphenol, and 3-methylbutanoic acids.12 These compounds are thought to be derived from the decomposition of organic binders such as phenolic urethane, furan, and alkyd isocyanate. 

The 3-(2-hydroxy-4,6-dimethylphenyl)-3-methylbutanoic acid shown in Fig. 8.23, as well as another phenylpropanoic derivative presented below, have been used as pro-moieties to prepare a number of prodrugs of therapeutic peptides [169] [238], Of interest here is that the pro-moiety is linked to the peptide by both amide and ester bonds to form a cyclic, double prodrug, the two-step activation of which is schematized in Fig. 8.24. Briefly, enzymatic hydrolysis of the ester bond unmasks a nucleophile (in this case, a phenol) that carries out an intramolecular attack on the amide bond, resulting in cy-clization of the pro-moiety and elimination of the peptide. [Leu5]enkephalin was one of the therapeutic peptides used to validate the concept, as illustrated in Fig. 8.25 [241],... 

This strategy also provides a convenient method for amination of various ester enolates with DPH Ih (Scheme 14). The amination of lithium eniminate of phenyl acetonitrile, the silyl enolate of ethyl phenylacetate and the Reformatsky reagent derived from ethyl a-bromoacetate with DPH were found to be unsuccessful. A failure of DPH for the amination of sodium enolates of S-diketones and the lithium enolate of 3-methylbutanoic acid was also reported . 

The use of 0-acylhydroxylamine-type reagents for amination of a-metallated carbonyl compounds is limited. The use of 0-mesitoylhydroxylamine 2j or 0-(3,5-dinitromesitoyl) hydroxylamine 2k in the amination of the enolate derived from 3-methylbutanoic acid was unsuccessful ". 

Branched chain fatty acids, such as 2-methylpropanoic, and 2-methylbutanoic and 3-methylbutanoic acids, are not products of the fatty acid synthetic pathway. They are instead derived from oxidation of the aldehydes formed from a-keto acids during amino acid metabolism (Fig 8D.5). The mechanism of regulation is not known. 

Besides tropic and phenyllactic acids, little is known about the biosynthesis of other acids esterifying the tropane nucleus. Leete [26] listed the acids found in tropane alkaloids whose biosynthesis has been studied, usually by feeding labelled precursors to intact plants. Thus, tiglic acid, the acidic moiety of tigloidine and meteloidine, has been shown to be derived from the amino-acid L-isoleucine, probably via 2-methylbutanoic acid [38],... 

A chiral 2-alkyl-4,5-dihydrooxazole 7 is obtained by the use of (+)-( 5, 2 S)-1-phenyl-2-aminopropane-1,3-diol, available from the chiral pool (see p 115). From this, the methyl ether 8 is prepared using sodium hydride and iodomethane. As a result of internal asymmetric induction, the alkylation of its lithium derivative occurs diastereoselectively. In the case of = Me, = Et, hydrolysis yields the (+)-( S)-enantiomer of 2-methylbutanoic acid 9, with ee = 67 %, as the main product ... 

Fig. 12 Enantioselective sensing by conformational changes in the sensors, (a) Mechanism of sensing in fluorophore-bearing cyclodextrins by interaction with a guest (b) water soluble imidazolium containing BINOL macrocycles 38, 39 (c) tris- and bis(oxazolmyl)phtaiols (40, 41) (d) l,8-bis(9,9 -diacridyl)naphthalene derivative 42 (e) Stem-Vobner plot of 42 upon interaction with enantiomers of a-halo acids (left 2-chloropropanoic acid, right 2-bromo-3-methylbutanoic acid), showing nonlinear response (from [85] reproduced by permission of The Royal Society of Chemistry)...

The same isocyanate derivative is also seen in the Hofmann rearrangement (Scheme 10.36). TTiat is, if the carboxylic acid chloride from the 2-methylbutanoic acid is first converted to the corresponding amide by reaction with ammonia (NH3) and the latter treated with bromine (Br2) and sodium hydroxide (i.e.,NaOBr formed from reaction of the two reagents), the corresponding A -bromo compound forms. 

Upon alkaline fusion of the crystalline mixture of beta acids, 2-methylbutanoic acid and 4-methylpentanoic acid have been isolated and Identified as the corresponding p.-bromophenacyl esters, in addition to 3-methylbutanoic acid and 2-methylpropanoic acid, derived from lupulone and colupulone, respectively (12). This suggests the presence of two homologues, which are named, in analogy with the alpha acids, adlupulone or 2-(2-methylbutanoyl)-4,6,6-tris(3-methyl-2-butenyl)-3,5-dihydroxy-cyclohexa-2,4-dienone (173, Fig. 79) and prelupulone or 4,6,6-tris(3-methyl-2-butenyl)-3,5-dihydroxy-2-(4-methylpentanoyl)cyclohexa-2,4-dienone (174, Fig. 79). 

The even-numbered acyl moieties are derived from valine, while the odd-numbered acyl units are derived from leucine. 2-Methyl-propanoic acid and 3-methylbutanoic acids were isolated from incubations with valine and leucine respectively. The results are consistent with earlier work on the biosynthesis of these alkaloids 225 226)... 

Because of the increased internal pressure ( Hydroskelett ), dissected mawworms emit malodorous compounds, which are present in both perienteric fluid and tissues of these nematodes. During dissection, these volatiles may evoke pruritus, inflammation of the eye, and vomiting in humans. In Ascaris lumbricoides, and also in other species such as Parascaris equorum, formic, acetic, propionic, -butyric, 2-methylbutanoic, and caproic acids (C5- and C6-acids main compounds) were found along with unidentified C5-a,/3 unsaturated acids.53 These acids are probably derived from mawworm metabolism and are not formed by microbial activity. 

The primary aromatic substances in beer are derived from raw materials (barley or hops) that confer the beer s typical odour and taste. Bitter acids of hops have a bitter taste (see Section 8.3.5.1.3), but hop cones also contain 0.3-1% m/m of terpenoids (60-80% of hop essential oil), which have a considerable influence on the smell of beer. The main components of aromatic hop oils are sesquiterpenic hydrocarbons in which a-humulene, P-caryophyllene and famesene dominate. The major monoter-penic hydrocarbon is myrcene. For example, the essential oil content of fine aromatic varieties, such as Saaz, is 0.8% m/m, of which 23% is myrcene, 20.5% a-humulene, 14% famesene 6% and P-caryophyUene. Significant components of the hop aroma in beer are mainly isomeric terpenoid monoepoxides resulting from autoxidation and diepoxides of a-humulene and fS-caryophyUene, but also other terpenoids. Important components of hops odour are also various alcohols (such as geraniol and hnalool), esters (ethyl 2-methylpropanoate, methyl 2-methylbutanoate, propyl 2-methylbutanoate and esters of terpenic alcohols, such as geranyl isobutanoate), hydrocarbons, aldehydes and ketones formed by oxidation of fatty acids, such as (3E,5Z)-undeca-l,3,5-triene, (Z)-hex-3-enal, nonanal, (Z)-octa-l,5-dien-3-one, their epoxides, such as ( )-4,5-epoxydec-2-enal and sulfur compounds. Other important components of hops are so-called polyphenols (condensed tannins) that influence the beer s taste and have antioxidant effects. Less important compounds are waxes and other hpids. Hop products, such as powder, pellets and extracts (by extraction with carbon... 

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