Regioselective synthesis of C-nucleosides by 1,3-dipolar cycloaddition of arylnitrile oxides to 5,6-dideoxy-1,2-O-iso-propylidene-α-d-xylo-hex-5-enofuranose

Syntheses of Anomeric Pairs of New C-Nucleosides via 1,3-Dipolar Cycloaddition Reaction, Part I

“…The following com pounds w ere p rep ared em ploying previously cited synthetic procedures : sil ver acetylide of ethyl propiolate [21], N -am inopyridinium iodide (6) [2 3 -27], N-phenylacyl pyridinium brom ide (12) [25] and N -ethyloxalyl-C -phenyl sarcosine (18) [26]. (200 ml) was follow ed by filtra tion, once through celite and th en thro u g h filter paper.…”

“…These sugar derivatives have been found to be the m ost useful key interm ediates (synthons) from which Q can be elab orated into a variety of heterocycles, thus giving rise to new and interesting C-nucleosides. This has provided routes to the synthesis of C -nu cleosides of several different heterocycles such as purines, pyrim idines, pyridines, lH -tetrazo les, oxadiazolones, pyridazones, substituted tetrazolopyridazines, isooxazolines, fused pyrazoles, pyrazolotetrazolopyridazines, and pyridopyrim idines during recent years [9][10][11][12][13][14][15][16][17][18][19], It was decided to use this approach for the syn thesis of C -nucleoside analogs w here suitably p ro tected and properly anom erically functionalized sugar derivatives (a and ß anom ers) w ere sepa rately used as a dipolarophile in 1,3-dipolar cyclo addition reactions. To the best of our know ledge this is the only rep o rt w here, b oth, a and ß anom ers have been sim ultaneously prep ared , allowing th e assignm ent of anom eric configuration of the product with high degree of certainity.…”