Syntheses and properties of pterin ribonucleosides

Abstract

Several pterin derivatives (1-8) have been ribosylated in form of their trimethylsilyl derivatives (9) with 1-bromo-(10) and 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribofuranose (11) under the catalysis of HgO/HgBr 2 , BF 3 -etherate and trimethylsilyl triflate, respectively. Mixtures of the N-1-(19-25) and N-3-ribofuranosides (12-18) which are difficult to be separated were obtained. Debenzoylation by the Zemplen method led to the free pterin-nucleosides (28-30). A second approach starting from 2-methylthio-4(3H)pteridinones (31-33) gave again mixtures of the N-1-(35-37) and N-3-ribonucleosides (38-40). The 2-methylthio function in 35-37 can easily be substituted by various amines leading after subsequently debenzoylation to the N-2-substituted pterin-ribonucleosides (41-50). The structural assignments were based on comparisons of the UV spectra with the corresponding N-methyl substituted model substances. 1 H-NMR-spectra functioned as additional structural proof.