Purines, pyrimidines, and imidazoles. Part XLI. Glycofuranosylamines derived from D-xylose, D-glucose, D-mannose, and L-rhamnose and their use in the synthesis of pyrimidine and imidazole nucleosides
3,5-O-Isopropylidene-D-xylofuranosylamine, 5,6-O-isopropylidene-D-glucofuranosylamine, 2,3-O-isopropylidene-L-rhamnofuranosylamine, and 2,3:5,6-di-O-isopropylidene-D-mannofuranosylamine toluene-p-sulphonates have been prepared in good yield by reactions of the corresponding pyranosylamines with acetone, 2,2-dimethoxypropane, and toluene-p-sulphonic acid. Reaction of the glycofuranosylamines with α-acetyl-, α-cyano-, or N-methyl-α-cyano-β-ethoxy-N-ethoxycarbonylacrylamides gave the corresponding 5-substituted uracil α- or β-glycofuran-osides. Furanose structures were confirmed by periodate titration or periodate oxidation. Assignments of anomeric configurations were in most cases confirmed by n.m.r. spectroscopy. The anomeric structures of the glycofuranosylamines in various solvents were studied by means of n.m.r. spectroscopy and optical rotation measurements. A bis(di-isopropylidenemannofuranosyl)amine of unknown anomeric structure was obtained as a by-product in one reaction. The isopropylidenemannofuranosylamine either with ethyl N-[ethoxycarbonyl-or carbamoyl(cyano)methyl]formimidates, or with ethyl formimidate hydrochloride [to give a mixture of ethyl N-1-(2,3:5,6-di-O-isopropylidene-α- and -β-D-mannofuranosyl)formimidates] followed by ethyl amino(cyano)acetate, gave 2,3:5,6-di-O-isopropylidene-α- and -β-5-amino-4-ethoxycarbonyl or -carbamoyl-imidazole D-mannofuranosides, from which the isopropylidene groups could be removed by aqueous acid. Structures of the aminoimidazole mannofuranosides were confirmed by means of periodate oxidation, n.m.r. and c.d. studies, and conversion of the esters into the corresponding amides.