NUCLEOSIDES .49. SYNTHESIS AND PROPERTIES OF 2,4-QUINAZOLINEDIONE N-1-2'-DEOXYNUCLEOSIDES, 3'-DEOXYNUCLEOSIDES AND 2',3'-DIDEOXYNUCLEOSIDES

A series of 6- and/or 7-substituted 2,4-quinazoline-dione N-1-deoxyribofuranosides have been synthesized and characterized. The 2'-deoxy-beta-D-ribofuranosides 23-28 have been prepared by transformation of the corresponding ribofuranosides by chemical deoxygenation. Direct glycosidation to the beta-anomers with a 2'-deoxyribofuranosyl donor to pure anomers failed due to missing diastereoselectivity and difficult separation of the reaction products. The synthesis of the 3'-deoxy-beta-D-ribofuranosides 54-58, however, was achieved by glycosidation of the trimethylsilylated 2,4-quinazolinediones 43-47 with an appropriate 3'-deoxyribofuranosyl donor (48). The 2',3'-dideoxy-beta-D-ribofuranosyl derivatives 63-66 were again obtained by chemical deoxygenation of the corresponding 2'-deoxy-beta-D-nucleosides, since all experiments of direct glycosidation with a 2',3'-dideoxyribofuranosyl donor as well as the chemical conversion of the corresponding ribonucleosides into the 2',3'-dideoxynucleosides failed due to side reactions. The newly synthesized compounds have been identified by UV and H-1-NMR spectra as well as elemental analyses.