Purines, pyrimidines, and imidazoles. Part XXV. Some chemical reactions and interconversions of intermediates in the sequence of biosynthesis de novo of purine nucleotides leading to imidazole nucleotides

Abstract

Controlled mild acid treatment of 5-amino-1-cyclohexylimidazole-4-carboxylic acid leads progressively to the formation of 5-amino-1-cyclohexylimidazole, N′-cyclohexyl-α-formylaminoacetamidine, α-amino-N′-cyclohexylacetamidine (or at higher pH α-N-formylamino-N′-cyclohexylacetamide) and also at higher pH, α-amino-N′-cyclohexylacetamide. The deformylations were readily reversed in each case by formylation with formic acid–acetic anhydride, and α-amino-N′-cyclohexylacetamidine was rapidly reconverted into 5-amino-1-cyclohexylimidazole with ethyl formimidate hydrochloride in a buffered aqueous solution. The structures of all the intermediates were confirmed by alternative syntheses from glycine or aminoacetonitrile. A similar sequence of reactions has been observed with the corresponding 5-amino-1-β-D-ribofuranosyl imidazole-4-carboxylic acid 5′-phosphate and the possible significance of the results in terms of the evolution of the biosynthetic pathway is discussed.