Mono-alanine complex

Catalyst screening experiments resulted in the discovery that copper(salen) complex 33 was a highly effective catalyst for the conversion of alanine derivative 16b into (f )-a-methyl phenylalanine 17 under the conditions shown in Scheme 8.16. The presence of just 1 mol% of catalyst 33 was sufficient to induce the formation of compound 17 with up to 92% ee and in >70% yield [33]. Allyl bromide, 1-chloromethylnaphthalene and ethyl iodide also reacted with substrate 16b to give the corresponding (H)-a-methyl a-amino acids in the presence of 2 mol % of complex 33 [34], Complex 33 also catalyzed the asymmetric mono-alkylation of glycine-derived substrate 34 by benzylic or allylic halides, to give (H)-a-amino acid derivatives 35 with 77-81% ee. and in greater than 90% yield, as shown in Scheme 8.17. 

In addition, OPEN is an efficient chiral solvating agent for determination of the enantiomeric excess in the H NMR analysis of various chiral mono- and dicarboxylic acids including a-arylpropanoic and a-halo carboxylic acids. The chemical-shift non-equivalence (S A) in certain diastereomeric complexes is greater than 0.05 ppm. A DPEN/Pd(II) complex can be used for determination of enantiomeric excess of the non-protected chiral amino acids by H and C NMR analysis. For example, Pd[(S,S)-dpen](D20)2 and racemic alanine with a base forms the square-planar complex (eq 14). The 5 A of H-NMR resonance in the diastereomeric complexes in D2O is 0.056 ppm, while this complex hardly dissolves in D2O. 

After cooling to 100 °C, disodium phosphate is added to precipitate traces of iron, and sodium carbonate is then added for neutralization to pH 5.S. The hot slurry is first filtered to remove insoluble humins and then stored for about two months for maturation. Then it is filtered again. H. results as a red-brown clear liquid, which exhibits the basic flavor of well-browned beef. This is the result of the complex action of - mono-sodium glutamate as a flavor enhancer and of several - amino acids that contribute to the boullion flavor, such as glycine, alanine, proline, leucine, serine, phenylalanine, asparagine, valine and tyrosine. 

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