3 -Hydroxy-2-butanon

Biacetyl is produced by the dehydrogenation of 2,3-butanediol with a copper catalyst (290,291). Prior to the availabiUty of 2,3-butanediol, biacetyl was prepared by the nitrosation of methyl ethyl ketone and the hydrolysis of the resultant oxime. Other commercial routes include passing vinylacetylene into a solution of mercuric sulfate in sulfuric acid and decomposing the insoluble product with dilute hydrochloric acid (292), by the reaction of acetal with formaldehyde (293), by the acid-cataly2ed condensation of 1-hydroxyacetone with formaldehyde (294), and by fermentation of lactic acid bacterium (295—297). Acetoin [513-86-0] (3-hydroxy-2-butanone) is also coproduced in lactic acid fermentation. 

C4H303 3-Hydroxy-2-butanone C4HnN s-Buty amine... 

Diels and Stephan173 treated the benzoate of 3-hydroxy-2-butanone with bromine, and obtained crystalline 1-bromo- and 1,1-dibromo- derivatives. With dilute alkali, these formed 4-deoxy-DL-gZycero-tetrulose and 4-deoxy-DL-erythrosone respectively. Both compounds gave with phenylhydrazine 4-deoxy-DL-erythrose phenylosazone, which had previously been prepared from the corresponding aldotetrose.174... 

The reaction of ethyl acetoacetate with simple hydroxy ketones has been compared with the corresponding reactions of the ketoses. The results obtained with l-hydroxy-2-propanone and 3-hydroxy-2-butanone, under the same experimental conditions as with D-fructose, establish a parallel between these reactions. However, as in the case of the aldoses, the yield is greater for these simpler hydroxy ketones than for the ketoses.9 The resultant esters, (XV and XVI), were obtained in the form of sirups, but the free acids, (XVII and XVIII), and their phenacyl esters are crystalline. The acids were shown to be identical with those of known structure described in the literature.9... 

Several products were also detected in base-degraded D-fructose solution acetoin (3-hydroxy-2-butanone 62), l-hydroxy-2-butanone, and 4-hydroxy-2-butanone. Three benzoquinones were found in the product mixture after sucrose had been heated at 110° in 5% NaOH these were 2-methylbenzoquinone, 2,3,5-trimethylbenzoquinone, and 2,5-dimethyl-benzoquinone (2,5-dimethyl-2,5-cyclohexadiene-l,4-dione 61). Compound 62 is of considerable interest, as 62 and butanedione (biacetyl 60) are involved in the formation of 61 and 2,5-dimethyl-l,4-benzenediol (63) by a reduction-oxidation pathway. This mechanism, shown in Scheme 10, will be discussed in a following section, as it has been proposed from results obtained from cellulose. 

Alternative precursors for the synthesis of NHCs are thiourea derivatives of type 3. The preparation of such thiones with a symmetrical substitution pattern is achieved by the reaction of a-hydroxyketones like 3-hydroxy-2-butanone with suitable 2-thiones (Fig. 3d) [31] or by reaction of a diamine with thiophosgene [32, 33]. Unsymmetrically substituted thiones 4 possessing a saturated heterocycle have also been described (Fig. 3e) [34, 35]. 

Pentanol in fraction 2 and to 61% for 3-Methyl-3-Hydroxy-2-Butanone in fraction 3. 

Hydroxy-2-Butanone were used as the internal standards for fractions 1, 2, and 3,... 

Reaction of Acetoin (3-Hydroxy-2-butanone) with Ammonia. Aqueous solution of ammonium hydroxyde (20%, 100 ml) was added to acetoin (17.6 g, 0.2 mol) and the reaction mixture was stirred for 30 min at 50°C and then for 6 h at room temperature. The precipitated product was filtered off, the filtrate was neutralized with 10% hydrochloric acid, and extracted with ether (continuous overnight extraction). The extract was washed with water, dried over anhydrous sodium sulfate, and concentrated on a spinning-band distillation apparatus. The residual solution was then analyzed by GC and GC-MS. 

Hydrophobic amino acid containing 0-aminoacyl sugars, biuemess, 159,160r 3-Hydroxy-2-butanone, See Acetoin... 

SCHEME 9. 2-Hydroxypropanal (19), 3-hydroxy-2-butanone 20 and 3,4-di-0-methyl-TO-(tri-methylsilyl)-L-erythmlose (21), used as the carbonyl substrate in 17... 

Characterisation of the aromatic profile in commercial guava essence and fresh fruit puree extracted with solvent yielded a total of 51 components [29]. Commercial essence was shown to be rich in components with low molecular weight, especially alcohols, esters, and aldehydes, whereas in the fresh fruit puree terpenic hydrocarbons and 3-hydroxy-2-butanone were the most abundant components. 

In another investigation, the volatile compounds were isolated [19] using a Porapack Q trap by vacuum for 2 h and were then eluted with hexane. The esters were the chemical class of compounds that predominated in the samples among 21 volatile compounds detected. Ethyl butanoate, ethyl 2-methylbutano-ate, 1-butanol, ethyl hexanoate, 3-hydroxy-2-butanone, ethyl octanoate, acetic acid, linalool, palmitic acid, and oleic acid were identified in cupuacu pulp by solid-phase extracton [15]. 

Hydroxy-2-butanone (acetoin) is a characteristic constituent of butter flavour used for flavouring margarine and can be obtained as a by-product of molasses-based and lactic acid fermentations [49, 71]. The closely related 2,3-butanedione (diacetyl) has a much lower organoleptic threshold than acetoin and is an important strongly butter-like flavour compound in butter and other dairy products [72] in buttermilk, for instance, the diacetyl concentration is only about 2-4 mg [73]. a-Acetolactate (a-AL) is an intermediate of lactic acid bacteria mainly produced from pyruvate by a-acetolactate synthase. In most lactic acid bacteria, a-AL is decarboxylated to the metabolic end product acetoin by a-AL decarboxylase (ALDB) [71] (Scheme 23.5). 

Hydroxy-2-butanone [513-86-0] M 88.1, b 144-145°, [m 100-105° dimer]. Washed with EtOH until colourless, then with ethyl ether or acetone to remove biacetyl. Air dried by suction and further dried in a vacuum desiccator. 

Reaction of anthranilonitrile or methyl anthranilate with 3-hydroxy-2-butanone followed by malononitrile gave the pyrrolo [1,2-a] quinazoline 16 (79AP552). Both of the diazine and azole rings of pyrroloquinazolines were also simultaneously formed by cyclization of the anilide 17 derived from 3-chloropropionic acid and 2-aminobenzophenone with potassium cyanide to afford the pyrrolo [1,2-a] quinazoline 18 (68JHC185 71USP3595861). 

The intermediary cofactor bound acetyl anion equivalent can be transferred to an aldehyde acceptor, e.g. to acetaldehyde already produced during regular catalytic reaction in which optically active 3-hydroxy-2-butanone (acetoin, an important aroma constituent) is formed. Interestingly, PDCs from different sources differ in stereoselectivity [443] acetoin (I )-143 is obtained using brewer s yeast PDC (ee 28-54%) [444,445] while the enantiomeric (S)-143 is produced preferentially by PDC from wheat germ (ee 16-34%) [446] or from Z. mobilis (ee 24-29%) [445], When glyoxylate 14 (instead of 2) is subjected to decarboxylation in the presence of acetaldehyde, optically active lactaldehyde... 

Many other compounds have been identified as products of the sugar-amino acid reaction. Amongst these are 2,3-butanedione,195 formaldehyde,196 pyruvaldehyde,20,195, 247, 248 3-hydroxy-2-butanone,248 hydroxy-2-propanone,248 and acetaldehyde.73 Imidazoles,196, 249-251 especially 4(5)-methylimidazole, have also been isolated from the reaction under mild conditions, and could have been formed from a-hydroxy ketones or aldehydes plus amino compounds. Following the early identification247 of pyru-valdehyde as a product of the Maillard reaction, much work was done in an attempt to show that this reactive compound plays a major role in the reaction,249 262 254 but, that this is so is by no means certain.7... 

Methyl ketones from esters (12, 126).1 The reaction of a carboxylic acid or ester with CH3Li and ClSi(CH3)3 to provide a methyl ketone has been used to obtain a silyl protected (S)-3-hydroxy-2-butanone (2) from ethyl lactate (1). The addition of... 

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