Keto formula

Geuther represented the substance as CHg.C OH) CH.COOC2H6, that is /3-hydroxycrotonic ester, but Frankland and Duppa preferred the keto formula CH8.CO.CH2.COOC2H6, and represented it as aceto-acetic ester,7... 

Enol formula Ethyl aceto acetate Keto formula... 

Note also that if another ester, of general formula R-COOCjHj, were used in place of benzaldehyde in the above reaction, a similar complex would be formed, and on acidification would give an unstable p-hydroxy-P-ethoxy ester, which would very readily lose ethanol with the formation of a 3-keto-ester. 

In a similar attempt, Decker and Eichler reduced A -methylnor-papaverinium phenolbetaine (VIII) with tin and hydrochloric acid and obtained i/i-laudanine, m.p. 112°, pierate, m.p. 162-3°, which was subsequently investigated by Spath and Epstein, who showed that on methylation it furnished dMaudanosine and that the ethyl ether on energetic oxidation yielded veratric acid (3 4-dimethoxybenzoic acid) and the methyl ethyl ether of nor-m-hemipinic acid. This clearly indicated that the free hydroxyl group was in the woquinoline nucleus, and its position was determined by the fact that on mild oxidation 7-methoxy-6-ethoxy-l-keto-2-methyl-l 2 3 4-tetrahydrowoquinoline, m.p. 95-6°, was produced, and on this basis these authors assigned formula (IX R = H R = CH3) to -laudanine. 

The former passes into the second on further oxidation with hydrogen peroxide, indicating that it is an a-keto-carboxylic acid. Acid (b) loses carbon dioxide on fusion and gives a neutral substance, CjaHj OgN, m.p. 238°, which was shown to be 6 7-methylenedioxy-A-methylphenanthri-done (I), by comparison with a synthetic specimen. The position of the carboxyl group in (b) could not be determined by synthetic methods but is probably at since dihydrolycorineanhydromethine, Cl 7 7 2 ) m.p. 87-5° [picrate, m.p. 174° (dec.) methiodide, m.p. 236° (dec.)] on distillation with zinc dust yields a mixture of phenanthridine, 1-methyl-phenanthridine and 6 7-methylenedioxyphenanthridine, m.p. 142° [picrate, m.p. 257° (dec.)], the identity of the two latter being established by comparison with the synthetic products. These results indicate for lycorineanhydromethine formula (II). 

The directions of rotation at C and C have been arrived at from the following considerations. The deoxy-bases (II p. 443 Q = quinoline residue) obtained from cinchonine and cinchonidine are structurally identical, i but optically different, and since they must be optically identical at C and C, and C is no longer asymmetric, the difference between them (see table, p. 446) must be due to difference in direction of rotation at C , which must therefore be dextrorotatory in cinchonine and laevorotatory in cinchonidine, and this must also be true of quinidine and quinine respectively and of the corresponding dihydro-bases. The keto-bases, cinchoninone and quininone, might be expected to exist each in two pairs, since carbon atom 8 is, according to the formula (p. 442), asymmetric, but it is better represented by the tautomeric grouping —... 

These formulae explain the scission products of the two alkaloids and the conversion of evodiamine into rutaecarpine, and were accepted by Asahina. A partial synthesis of rutaecarpine was effected by Asahina, Irie and Ohta, who prepared the o-nitrobenzoyl derivative of 3-)3-amino-ethylindole-2-carboxylic acid, and reduced this to the corresponding amine (partial formula I), which on warming with phosphorus oxychloride in carbon tetrachloride solution furnished rutaecarpine. This synthesis was completed in 1928 by the same authors by the preparation of 3-)S-amino-ethylindole-2-carboxylic acid by the action of alcoholic potassium hydroxide on 2-keto-2 3 4 5-tetrahydro-3-carboline. An equally simple synthesis was effected almost simultaneously by Asahina, Manske and Robinson, who condensed methyl anthranilate with 2-keto-2 3 4 5-tetrahydro-3-carboline (for notation, see p. 492) by the use of phosphorus trichloride (see partial formulae II). Ohta has also synthesised rutaecarpine by heating a mixture of 2-keto-2 3 4 5-tetrahydrocarboline with isatoic anhydride at 195° for 20 minutes. 

Cyanogen azide is a useful reagent for conversion of pyrrolidine enamines of 3-keto steroids to A-norsteroids. " Ring contractions can be carried out in the presence of 17j5-hydroxy, 17j -acetoxy, 20-keto groups and isolated double bonds. In a typical procedure, 17j -hydroxy-5a-androstan-3-one (partial formula 8) is converted into the enamine (9) by pyrrolidine in benzene... 

For low molecular weight aliphatic acids, try TMSDEA reagent. Otherwise, use MSTFA, BSTFA, or TRI-SIL BSA (Formula P). For analysis of the keto acids, methoxime derivatives should be prepared first, followed by the preparation of the trimethylsilane (TMS) derivatives using BSTFA reagent. This results in the meth-oxime-TMS derivatives. 

This product is also obtained on alkaline hydrolysis of compounds of the formula RCOCHX2. Similar reactions have been performed on a-keto acetals and y-keto... 

Aldose-ketose isomerism Fructose has the same molecular formula as glucose but differs in its structural formula, since there is a potential keto group in position 2, the anomeric carbon of fmctose (Figures 13 and 13-7), whereas there is a potential aldehyde group in position 1, the anomeric carbon of glucose (Figures 13-2 and 13-6). 

Carotenoids are a group of more than 750 naturally occurring molecules (Britton et al. 2004) of which about 50 occur in the normal human food chain. Of these, only 24 have, so far, been detected in human plasma and tissues (Khachik et al. 1995), with only six molecules being abundant in normal human plasma (for chemical formulas see Figure 13.1). Carotenoids are subdivided into two main classes the carotenes, cyclized (e.g., P-carotene) or uncyclized (e.g., lycopene) hydrocarbons, and the xanthophylls, which have hydroxyl groups (e.g., lutein and zeaxanthin), keto-groups (e.g., canthaxanthin), or both (e.g., astaxanthin) as functional groups. 

XVIII has now been excluded,42 since the methyl glycoside of the sugar reacts rather rapidly with one mole of periodate per mole furthermore, in contrast to the behavior of mycaminose (XXI), no moiety with one carbon atom less has been isolated from the products of periodate oxidation. Oxidation of mycarose with hypoiodite affords a crystalline lactone with the empirical formula C7H12O4 this observation eliminates the possibility of the keto structure XX. Thus, mycarose appears to be a 2,6-dideoxy-3-C -methylhexose (XIX). In the original compound, the isovaleryl group must be esterified to the alcohol function at C4, since the methyl glycoside isovalerate obtained from carbomycin is only attacked by periodate after alkaline hydrolysis. 

Asymmetric hydrogenation of fi-keto esters.7 The Ru(OAc)2(BINAP) complexes are ineffective catalysts for asymmetric hydrogenation of (i-keto esters, but on treatment with HX (2 equiv.) are converted into complexes with the empirical formula RuX2(BINAP), which are effective catalysts for this enantioselective hydrogenation. Complexes of (R)-BINAP catalyze hydrogenation to (R)-(S-hydroxy esters in >99% ee, whereas the enantiomeric (S)-P-hydroxy esters are obtained... 

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