Nucleoside, XXXII. Über die Ribosidierung des 7‐Oxo‐7,8‐dihydrolumazins und seines 6‐Methyl‐ und 6‐Phenyl‐Derivates

7-Oxo-7,8-dihydrolumazin (1), sein 6-Methyl-(2) und 6-Phenyl-Derivat (3) werden in Form ihrer Trimethylsilyl-Derivate 6 – 8 Ribosidierungsreaktionen unterworfen. 2,3,5-Tri-O-benzoyl-1-brom-D-ribofuranose (9) fuhrt unter Hg-Salz-Katalyse zu den entsprechenden N-1-Mono-(11 – 13) und N-1,N-3-Diribosiden (17 – 19), wahrend mit 1-O-Acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (10) und SnCl4 die N-3-Nucleoside 23 – 25 gebildet werden. Eine N-8-Substitution wird nicht beobachtet. Entbenzoylierungen fuhren zu den freien Nucleosiden 14 – 16, 22 und 26 – 28. Die Verbindungen werden durch UV- und NMR-Spektren sowie pK-Werte charakterisiert. Nucleosides, XXXII. Ribosylations of 7-Oxo-7,8-dihydrolumazine and its 6-Methyl- and 6-Phenyl Derivatives Ribosylation reactions of 7-oxo-7,8-dihydrolumazine (1) and its 6-methyl- (2) and 6-phenyl derivative, respectively, are described. Treatment of the trimethylsilyl derivatives 6 – 8 with 2,3,5-tri-O-benzoyl-1-bromo-D-ribofuranose (9) in the presence of Hg-salts leads to mixtures of the corresponding N-1-mono- (11 – 13) an N-1,N-3-diribosides (17 – 19), whereas the analogous reaction with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (10) and SnCl4 gave N-3-nucleosides (23 – 25). N-8-Substitution has not been observed. On debenzoylations the free nucleosides 14 – 16, 22, and 26 – 28 are formed. The structures of the newly synthesized compounds have been established by UV- and NMR spectra as well as pK determinations.