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Hydrogenolysis of (5 R )-3-(1,2:3,4-di- O -isopropylidene- d - arabino -tetritol-1-yl)-5-(3- O -benzyl-1,2- O -isopropylidene-α- d - xylo -tetrofuranos-4-yl)-4,5-dihydroisoxazole afforded the 7-ulose derivative, from which 6-deoxy- d - gluco - d - gluco - and d - manno - d - gluco -undecose derivatives 17 and 18 were prepared by reduction with sodium borohydride or l -Selectride. The configuration of the new stereogenic centre (C-7) in compounds 17 and 18 was established by NMR analysis of their 5,7- O -isopropylidene derivatives. 6-Deoxy- l - manno - d - gluco - and l - gluco - d - gluco -undecose analogues 19 and 20 were prepared similarly from the isomeric 3-( l - arabino -tetritolyl)-4,5-dihydroisoxazole. Removal of the isopropylidene protecting groups from compounds 17 and 20 yielded 3- O -benzyl-6-deoxy- d - gluco - and l - manno - d - gluco -undecopyranoses, which were characterised as their octa-acetate derivatives. The corresponding reaction sequence from 3-( d - and l - arabino -tetritol-1-yl)-5-(2,3- O -isopropylidene-3- O -methyl-α- d - lyxo -tetrofuranos-4-yl)-4,5-dihydroisoxazoles afforded 6-deoxy- d / l - gluco - d - manno and d / l - manno - d - manno -undecose derivatives. |
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