Labeling of Amino Acids and Peptides With Isotopic Oxygen as Followed by super(17)O-N.M.R

super(17)O was introduced into the respective alpha - and gamma -COOH groups of Boc-Gly and Boc-Glu by saponification of the corresponding O-methyl esters with 1 N NaOH in H sub(2) super(17)O. Other super(17)O enriched Boc-amino acids were prepared by acid catalyzed exchange into the amino acid alpha -COOH group followed by t-butyloxycarbonylation with t-butyl S-4, 6-dimethylpyrimidin-2-ylthio carbonate. Final enrichment, by approximately three orders of magnitude over natural abundance, was 60-100% of the possible maximum. The synthesis of ( super(17)O)-Gly-Ala, ( super(17)O)-Gly-Leu and ( super(17)O)-Gly-Glu by Dcc/HBT mediated coupling of Boc-Gly-( super(17)O)- alpha minus or plus OOH with amino acid-O-t-butyl esters followed by deprotection with HCl/EtOAc proceeded without undue loss of the isotope.