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Regioselective ribosylation conditions were established which gave both 6,7-dichloro-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)imidazo[4,5-b]quinolin-2-one (4) and 6,7-dichloro-3-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)imidazo [4,5-b]quinolin-2-one (5), respectively, in high yield from 6,7-dichloroimidazo[4,5-b]quinolin-2-one (6). The distributions of the sites of ribosylation under a variety of conditions are discussed.

The polyhalogenated benzimidazole nucleosides 2,5,6-trichloro-1-(β-d-ribofuranosyl)benzimidazole (TCRB) and the 2-bromo analogue (BDCRB) were synthesized in our laboratory and established as potent and selective antiviral agents against human cytomegalovirus (HCMV) with a novel mode of action. In an effort to study the behavior of the key substructure of these analogues in a dimensionally stretched-out manner and probe the spatial limitation of the target enzyme(s), a series of N1- and N3-ribonucleosides of imidazo[4,5-b]quinolines were designed as linear dimensional analogues. The nucleosides 6,7-dichloro-1-(β-d-ribofuranosyl)imidazo[4,5-b]quinolin-2-one and 6,7-dichloro-3-(β-d-ribofuranosyl)imidazo[4,5-b]quinolin-2-one were selected and prepared as the key intermediates in this study. During this study, a novel photoassisted annulation was developed for the synthesis of 6,7-dichloroimidazo[4,5-b]quinolin-2-one, which overcame several problems that were encountered with the literature annulation method. ...

Preparation of novel model polymers of polynucleotides with copoly(vinylamine–vinylalcohol) [P(Vam–Val)] backbone and a pair of adeninyl and thyminyl pendant groups is described. At first, direct, low temperature esterification was used to attach (−) and (±)-2-(thymin-1-yl)propionic acid [(−)TPA and (±)TPA], to the N–Cbz protected hydroxy polymer P(Vamz–Val) which was prepared by selective N-protection of N-benzyloxycarbonyloxy-5-norbornene-2,3-dicarboximide (CbzONB) with P(Vam–Val), at the hydroxy group via an ester bond. Two novel precursors P(Vamz–Ve(−)T) and P(Vamz–Ve(±)T) were obtained. Then the Cbz protecting group of P(Vamz–Ve(−)T) and P(Vamz–Ve(±)T) were removed by hydrobromic acid to give the hydrobromide salt of P(Vam–Ve(−)T) and P(Vam–Ve(±)T), respectively. Finally, the attachment of (±)-2-(adenine-9-yl)propionic acid [(±)APA] to linear P(Vam–Ve(−)T) and P(Vam–Ve(±)T) by selective N-acylation with N-hydroxy-5-norbornene-2,3-dicarboximide (HONB). This procedure gave the corresponding P(Vam–Val) having a pair of adeninyl and thyminyl pendant groups, such as P(Va(±)Ad–Ve(−)T) and P(Va(±)Ad–Ve(±)T). In contrast to the corresponding polymer models, the related segment model compounds were also prepared from threo-2-amino-4-pentanol without N-blocking-deblocking operations. The segment model compounds including four stereoisomers of highly optical purities, were separated and purified by reverse phase HPLC technique.