D-Alanyl-L-leucine

Concerning the nomenclature of the two compounds where they have been isolated, the more insoluble is called the A compound and the more soluble the B compound. It has been possible to determine by the action of trypsin, which only hydrolyses the compound containing the naturally occurring amino acids, what combinations are present in them thus, as alanyl-leucine A was hydrolysed by trypsin it must contain d-alanyl-l-leucine, and the two compounds must therefore be... 

The compounds marked with an asterisk are racemic and their hydrolysis was effected asymmetrically, only that portion of the molecule containing the natural stereoisomer being attacked. This explained the difference between alanyl-leucine A and alanyl-leucine B the former probably consisted of d-alanyl-l-leucine -l- 1-alanyl-d-leucine, the first of which contains the natural stereoisomers upon which the hydrolysis depends the latter would consist of d-alanyl-d-leucine1-alanyl-l-leucine. The later experiments of 1907 proved this supposition. It is more noticeable in the case of leucyl-leucine, which must have been... 

Optically Active. Glycyl-l-tyrosine. Glycyl-d-alanine. Glycyl-d-tryptophane. Glycyl-l-phenylalanine. Glycyl-3, 5-diiodo-l-tyrosine. dl-Alanyl-d-alanine. 1-AlanyI-glycine. d-Alanyl-d-alanine. d-AIanyl-l-leucine. d-Alanyl-d-tryptophane. 

Still using heterogeneous gramicidin, Synge24 isolated the D-leucylglycine, L-alanyl-D-valine and L-alanyl-D-leucine from partial hydrolysates of gramicidin. He also had less conclusive evidence for the tripeptides alanyl-valylleucine or alanylleucylvaline. 

Cyclosporine A Cyclosporine A, [R-[R, R -(E)]]-cyclo-(L-alanyl-D-alanyl-iV-methyl-L-leucyl-iV-methyl-L-leucyl-A-methyl-L-valyl-3-hydroxy-iV,4-dimethyl-L-2-amino-6-octenoyl-L-a-aminobutyryl-A-methylglycyl-iV-methyl-L-leucyl-L-valyl-iV-methyl-L-leucine) (31.2.2), is extracted from a cultural liquid of products of the vital activity of the mushroom Tolypocladium inflatum [14-17], and which is also proposed to obtain synthetically [18-20]. 

Enzymes.—The possibility of synthesizing an artificial enzyme has been discussed. Condensation of 2-acetamido-3,4,6-tri-0-acetyl-l-A -[A -(benzyloxycarbonyl)-L-aspart-4-oyl]-2-deoxy-j8-D-glucopyranosylamine with suitably protected derivatives of L-alanine, L-alanyl-L-threonine, L-alanyl-L-threonyl-L-leucine, and L-alanyl-L-threonyl-L-Ieucyl-L-alanine afforded glycopeptides corresponding to the sequences 18—19, 18—20, 18—21, and 18—22 of deoxyribonuclease A. ... 

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