Nucleosides part LXVI I: synthesis of 4-amino-7(8H)pteridinone-N8-nucleosides-structural analogs of adenosine

Various 4-amino-7(8H)pteridones (6, 12, 14, 15, 20, 22) have been glycosylated with 1-chloro-2'-deoxy-D-ribofuranose derivatives (25, 26) applying the new DBU-salt method to form the N(8)-2'-deoxy-D-ribofuranosides (27-36) which can be regarded as 2'-deoxyadenosine analogs. Analogously reacted the 2-N,N-dimethyl-amino-methyleneimino-7(8H)pteridones (43-48) to give preferentially the corresponding N(8)-beta-D-anomers (49-55). Ribosylation with 1-bromo-2,3,5-tri-O-benzoyl-a-D-ribofuranose (56) proceeded as well with 6, 12, 15, 45, and 46 to yield to N(8)-beta-D-ribofuranosides 57-61. Sugar deprotection led to the free N(8)-2'-deoxy-beta-D-ribofuranosides 37-42 and N(8)-beta-D-ribofurano-sides 62-65, respectively. Glycosylations via the silyl-method under Vorbruggen conditions led with 6, 12 and 15 to the same results, however, 4-amino-6-phenyl-7(8H)pteridone (14) reacted differently forming the N(1)-beta-D-ribofuranosides (71, 79) and the N(1)-2'-deoxy-alpha-and ss-D-ribofuranosides 73, 74, 77, 78. The assignments of the structures have been achieved by (1)H-NMR- and UV-spectra. C,H,N-elemental analyses account for the composition.