N-Hydroxyamino acid residues

II. N-Hydroxyamino Acid Residues as Fragments of Natural Products. 206... 

A description of physical and chemical properties of N-hydroxyamino acids and methods of their analysis will be included and brief mention will be made of the more important natural products containing N-hydroxyamino acid residues as well as the main aspects of their biogenesis. 

Free N-hydroxyamino acids (1) or (2) have never been isolated from living organisms, probably because of their instability. As already mentioned, N-hydroxyamino acid residues occur only as fragments of many natural products containing the N-hydroxyamide bond. The isolation of free N -hydroxy-L-arginine from the fermentation medium of Bacillus cereus (6, 7) may be considered as an exception however, this compound contains an N-hydroxyguanidine rather than an N-hydroxyamine group. 

The N O acyl rearrangement reaction at the hydroxyamino-acid residues (Ser and Thr) and the selective chemical cleavage of the chain at the resulting ester bonds have been studied in detail using unfractionated clupeine (Iwai, 1959, 1960, 1961 Iwai and Ando, 1967). This method of degradation retains intact sequences of arginine residues in the products. 

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