Aminoacyl and dihydro-derivatives of isocytidine and isocytosine
Abstract
Isocytosine and 2′,3′-O-protected isocytidines were coupled with appropriately protected L-phenylalanine, glycine, or glycylglycine yielding the corresponding 2-N-aminoacyl-isocytosines and -isocytidines. The mode of hydrolysis of 2-N-(N-t-butoxycarbonyl-L-phenylalanyl)isocyfidine (5) with trifluoroacetic acid, to give 2-N-L-phenylalanylisocytidine (16), 2-N-L-phenylalanylisocytosine (17), and minor amounts of unexpected 5′-O-phenylalanyl derivatives, (18) and (19), was shown to depend on the reaction conditions.
Catalytic hydrogenation of 2′,3′-O-ethoxymethyleneisocytidine (9), the 2-N-aminoacylisocytidines (5) and (7), and 2-N-glycylglycylisocytosine (15) over 5% rhodium–carbon gave the corresponding 5,6-dihydro-derivatives (20), (23), (22), and (21) in quantitative yields.