Synthesis of 4-oxonorleucine and Comparison with an Amino Acid Isolated from Citrobacter Freundii.

Many new amino acids have been discovered in plants (l-9) and in microorganisms (10-13) which are not normally found in animal tissues. Some of these show little structural similarity to the amino acids found in animal protein whereas others are closely related structural analogues. The isolation of 4-0x0norleucine from acid hydrolysates of a polysaccharide obtained from Citrobacter jreundii was recently reported (14). As this amino acid had not previously been found in nature, it was of interest to firmly est,ablish its identity by synthesis and by a comparison of the properties of the isolated material with those of the synthetic product. In addition, a comparison was made of 4-hydroxynorleucine obtained by reduction of the isolated amino acid with synthetic 4-hydrosynorleucine.