Reaction of 3-deoxypentosulose with N-methyl- and N,N-dimethylguanidine as model reagents for protein-bound arginine and for creatine.

Deoxyosones are established key-intermediates in Maillard processes. Due to their dicarbonyl structure, they undergo condensation to form heterocyclic compounds with guanidine derivatives. In biological systems, guanidino functions are present in protein-bound arginine moieties as well as in creatine. The reactivity of such structures towards 3-deoxypentosulose is investigated with N-methyl- and N,N-dimethylguanidine as model substrates. Two diastereoisomers each are isolated from both reactions; they have been characterized unequivocally, respectively, as 4-(2,3-dihydroxypropyl)-2-N-methylamino-2-imidazoline-5-one and 4-hydroxy-5-(2,3-dihydroxypropyl)-2-(N,N-dimethylamino)-5H-imidazole. In aqueous medium as well as in the crystalline state, both diastereoisomer pairs exist in different tautomeric forms.