Pteridines CII Synthesis and Characterization of Dimeric Lumazines

Abstract

Reduction of 1.3-dimethyllumazine (1) by zinc dust in Ac2O/AcOH leads to the formation of 6-7 connected bis-Iumazinyl derivatives. Depending on the reaction conditions either 7 -(5-acetyl-5,6, 7,8-tetrahydro-1.3-dimethyllumazin- 6-yl)-l, 3-dimethyllumazin (3) or isomeric 7 -(5-acetyl-5.6. 7.8-tetrahydro-I. 3-dimethyllumazin- 6-yl)-5-acetyl-5,6,7,8-tetrahydro-I. 3-dimethyllumazines (2) are formed . Treatment of 3 with MeOH/HCl gave 4 which is oxidized by air to a very stable 7.8-dihydro derivative 5 showing unexpected spectra properties. Further oxidation by KMnO. afforded 6.1 -bis-I. 3-dimethyllumazinyl (6). The isomeric 6.6-(14) and 7.7 -bis-I. 3-dimethyllumazinyls (21) were also synthesized from 6-chloro-(1l) and I-chloro-I. 3-dimethyllu-mazine (18). respectively. in a nickel catalyzed dimerization reaction. The various structures were proven by spectral means. elemental analyses and an X-ray analysis of 2. Comparisons of the structural features are mainly based on UV data.