C-nucleoside studies. Part 8. Synthesis of 3-β-D-arabinofuranosylpyrazole fromD-mannose

Synthesis of Functionalized Compounds Containing Pyridazine and Related Moieties

“…(46). In order to carry out transformation of bis-ketals 45, 46 into C-nucleosides 49, 50, a slightly modified synthetic protocol, reported previously by Buchanan and co-workers [12], was employed. Thus, compounds 45 and 46 were mesylated and then, the mesylates 47 and 48 were heated in 1,2-dimethoxyethane in the presence of 1 equivalent of 4% hydrochloric acid to afford 3-(α-D-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine (49) and its β-anomer 50 in 81% and 54% yield, respectively.…”

The Chemistry of C-Nucleosides

“…It was later found (200) that these ethynes can be more readily obtained by treatment of 2,3,4,S-tetra-O-benzyl-D-aldefrydo-ribose(270) with the Grignard reagent, followed by cyclization of the sugar. Several pento-and hexofuranosyl-ethynes were also prepared (201)(202)(203)(204). 1,3-Dipolar addition to the ethynes with diazomethane gave their corresponding 3-glycosylpyrazoles in good yields (203,205).…”

“…1,3-Dipolar addition to the ethynes with diazomethane gave their corresponding 3-glycosylpyrazoles in good yields (203,205). An alternative method to prepare 3-glycosylpyrazoles from carbohydrate ethynes has also been developed (201,203). For example, l-diethoxymethyl-2-ribofuranosylethyne(2061(273)was prepared from 251, and then the aldehyde 274 was generated by acid treatment.…”