Symmetrical vicinal diuloses were prepared from 2,3:4,5‐di‐O‐isopropylidene‐D‐arabinose and ‐L‐arabinose by using methyltriphenylphosphonium bromide to convert both enantiomers into the corresponding 1,2‐dideoxy‐3,4:5,6‐di‐O‐isopropylidene‐arabino‐hex‐1‐enitols D‐5 and L‐5. The metathesis reactions of D‐5 with itself and with L‐5, respectively, by using the Hoveyda–Grubbs catalyst gave diastereomeric dec‐5‐enitols DD‐6 and DL‐6, which were dihydroxylated with osmium tetroxide to give 1,2:3,4:7,8:9,10‐tetra‐O‐isopropylidene‐protected decitols DD‐7 and DL‐7. Swern oxidation of the decitols afforded isopropylidene‐protected deco‐5,6‐diuloses DD‐8 and DL‐8, which gave unprotected deco‐5,6‐diuloses DD‐9 and DL‐9 upon acidic cleavage of the isopropylidene groups. The structures of both diastereomers were confirmed by NMR spectroscopy and X‐ray crystal structure analysis.
Abstract:Benzyl 3,4,6-tri-O-benzyl-β-D-arabino-hexos-2-ulo-1,5-pyranoside was subjected to mannoselective ketone alkynylation with propiolaldehyde dibenzyl acetal, resulting in the formation of a 2-C-alkynyl β-mannoside bearing a γ-dibenzyl acetal functionality. Subsequent transacetalization of the acetal moiety with methanol and 1,3-dihydroxypropane and acetylation of position 2, respectively, gave 4 different 2-C-alkynyl branched mannosides. Lindlar hydrogenation of the latter under optimized conditions in dimethylformamide afforded a series of 2-C-cis-alkenyl mannosides. X-ray molecular structures of benzyl 3,4,6-tri-O-benzyl-β-D-arabino-hexos-2-ulo-1,5-pyranoside and of the branched glycoside benzyl 3,4,6-tri-O-benzyl-2-C-((Z)-3,3-dibenzyloxyprop-1-en-1-yl)-β-Dmannopyranoside are reported.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.