Purines, Pyrimidines, and Imidazoles. Part 64. Alkylation and Acylation of Some Aminoimidazoles Related to Intermediates in Purine Nucleotide de novo and Thiamine Biosynthesis.

Treatment of ethyl 5-amino-1-benzylimidazole-4-carboxylate with butyl-lithium and methyl iodide gave the 5-N-methylamino derivative (4b) and the 3-methiodide (5) whereas ethyl 5-amino-1-(2,3-O-isopropylidene-β-D-ribofuranosyl)imidazole-4-carboxylate gave both the 5-N-methylamino (6b) and 2-methyl (6d) derivatives. Ethyl 5-amino-1-benzylimidazole-4-carboxylate with acetic anhydride or acetyl chloride gave various products, according to the conditions, including the 5-N-mono- and -N,N-di-acetylamino derivatives (4d) and (4c), respectively, and N,N′-dibenzyloxamide (9). The oxamide also arose from treatment of the imidazole (4a) with formaldehyde. 3-Cyanopropanimidate with ethyl α-amino-α-cyano acetate followed by benzylamine or 2,3-O-isopropylidene-D-ribosylamine afforded ethyl 5-amino-1-benzyl-2-(2-cyanoethyl)imidazole-4-carboxylate, respectively. Ethyl 5-amino-(2,3-O-isopropylidene-β-D-ribofuranosyl)-2-ethoxycarbonylethylimidazole-4-carboxylates, and the corresponding 2-ethoxyethyl nucleoside (6i) were similarly prepared. Oxidation of ethyl 5-amino-2-methylimidazole-4-carboxylate with N-chlorosuccinimide and potassium hydroxide led to ethyl 5-amino-1-benzyl-2-formylimidazole-4-carboxylate and oxidation of the protected 2-ethoxycarbonylethyl nucleoside (6j) with selenium dioxide produced the urea derivative (6I).