N-alkoxycarbonyl-glutamic and aspartic acids. Studies on the activation and cyclodehydration and side-reaction encountered in analysis of glutamic acid using Fmoc-chloride.
N-Alkoxycarbonylaminodicarboxylic acids were reacted in dichloromethane with N-ethyl-N'-(dimethylaminopropyl)carbodiimide hydrochloride, and with methyl chloroformate in the presence of N-methylmorpholine. Removal of secondary products by washing the mixtures with aqueous solutions gave good yields of the pure crystalline internal anhydrides. Anhydrides of N-benzyloxycarbonyl- (Z) and N-9-fluorenylmethoxycarbonyl-(Fmoc) L-glutamic and L-aspartic acids and of N-tert.-butoxycarbonyl-L-aspartic acid were prepared in this way. The compounds were shown to be amenable to normal phase high-performance liquid chromatography (NP-HPLC) on a CN-column using tert.-butanol-hexane as solvent. The products of the reactions of Z- and Fmoc-glutamic acid with hot acetic anhydride were examined by nuclear magnetic resonance and NP-HPLC before and after methanolysis in an attempt to establish if any of the corresponding pyroglutamates were formed. The reaction of Fmoc-chloride with Fmoc-glutamate was examined for the same reason. It is concluded that the side product generated during the reaction of Fmoc-chloride with glutamic acid which is used for analysis of the latter is the N-protected internal anhydride and not the pyroglutamate as reported in the literature.
Department of Biochemistry, University of Ottawa, Ontario, Canada.
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Benoiton
D000596:Amino Acids / Q000138:chemical synthesis*; D001224:Aspartic Acid / Q000031:analogs & derivatives* / Q000032:analysis / Q000737:chemistry; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000737:chemistry; D005449:Fluorenes / Q000138:chemical synthesis*; D005971:Glutamates / Q000032:analysis* / Q000138:chemical synthesis / Q000737:chemistry*; D018698:Glutamic Acid; D008752:Methylene Chloride / Q000737:chemistry
D000596:Amino Acids; D005449:Fluorenes; D005971:Glutamates; C016456:N(alpha)-fluorenylmethyloxycarbonylamino acids; D001224:Aspartic Acid; D018698:Glutamic Acid; D008752:Methylene Chloride; D005022:Ethyldimethylaminopropyl Carbodiimide