Pyruvic acids, degradation preparation

Apart from sotolon, the other compounds in Fig. 5 can be explained as the products of a Maillard reaction, and their carbon skeletons simply originate from the active Amadori intermediate in other words, they still preserve the straight carbon chain structure of monosaccharides. In spite of being a simple Cg lactone, sotolon has a branched carbon skeleton, which implies another formation process in the Maillard reaction. Sulser e al.(6) reported that ethyl sotolon (ll) was prepared from threonine with sulfuric acid, and that 2-oxobutyric acid, a degradation product of threonine, was a better starting material to obtain II. This final reaction is a Claisen type of condensation, which would proceed more smoothly under alkaline conditions. As we(lO) obtained II from 2-oxobutyric acid (see figure 6) with a high yield in the presence of potassium carbonate in ethanol, a mixed condensation of 2-oxobutyric and 2-oxo-propanoic (pyruvic) acids was attempted under the same conditions, and a mixture of sotolon (22% yield) and II were obtained however, the... 

Oxidative degradation of substituted pyruvic acids is accomplished by treating an aqueous solution of the sodium salt with 30% hydrogen peroxide (Superoxol) at 0-15°. Good descriptions have been published for the preparations of o-hydroxyphenylacetic acid (34%), 3,4-dim.ethoxy-phenylacetic acid (60%), m-chlorophenylacetic acid (57%), and o-nitro-phenylacetic acid. ... 

Degradation of L-tryptophan takes place in some bacteria by the tryptophanase reaction in which the amino acid is converted to indole (35), pyruvic acid and ammonia. The reaction was first observed in 1903. Wood and his collaborators first prepared the enzyme tryptophanase which catalyses the change from Escherichia coli and showed that pyridoxal phosphate is the co-enzyme involved . Snell and his colleagues have proposed a mechanism for the reaction in which the required cleavage occurs via the intermediacy of a pyridoxal phosphate-tryptophan-metal complex... 

Methyl 4,6-O-methylene-o-D-mannopyranoside was the only product isolated from the LiBr-catalised transacetalation of the unprotected methyl glycoside with dimethojqmiethane. Cyclopentylidene derivatives of pentoses have been prepared in moderate yields by treatment of the free sugars with cyclopentanone in the presence of copper (II) sulphate and sulphuric acid. D-Xylose formed the diacetal (11) (also used in Scheme 3 below), whereas from D-ribose the 2,3-monoacetal (12) was obtained. A novel, selective synthesis of (5)-configurated 4,6-pyruvate acetals of methyl D-hexopyranosides is illustrated in Scheme 1. It relies on transacetalation from the dimethyl acetal of 3,4-dimethoxybenzophenone to give, after acetylation, preferentially the intermediate (13) with an axial aryl substituent which, on oxidation, suffers rapid degradation to a carboxylic acid group. ... 

The procedure consists of stepwise enzymatic degradation of chemically prepared neuraminic acid derivatives (3) to give the corresponding modified ManNAc analogs (1), which is followed by subsequent neuraminic acid reconstruction in the presence of [3- C] labeled pyruvate (21). To ensure complete conversion in the desired direction the first step was promoted by cofactor-dependent reduction of pyruvate the second, synthetic step, was uncoupled by destruction of the nucleotide cofactor before addition of labeled pyruvate. Sialic acids such as 20 with high label incorporation (> 87%) were obtained in good yields (46-76%). 

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