Synthesis of 2,6,7-trideoxy-7-C-(2,4-dichlorophenyl)-d-xylo-heptonic acid and 6-(2,4-dichlorophenyl)-d-xylo-2,3,4-trihydroxyhexanesulfonic acid
摘要:
2,4-O-Benzylidene-L-xylose was converted via a Wittig reaction into Z-2,4-O-benzylidene-5,6-dideoxy-6-C-(2,4-dichlorophenyl)-D-xylo-hex-5-enitol (17), which, on hydrogenation, gave 5,6-dideoxy-6-C-(2,4-dichlorophenyl)-D-xylo-hexitol (33). tert-Butyldimethylsililation of the primary hydroxyl group of 33, followed by 4-methoxybenzylation, and desilylation afforded 5,6-dideoxy-6-C-(2,4-dichlorophenyl)-2,3,4-tri-O-(4-methoxybenzyl)-D-xylo-hexitol (54). A Mitsunobu-type reaction of 54 replaced HO-1 by cyanide to give, after hydrolysis and hydrogenolysis, 2,6,7-trideoxy-7-C-(2,4-dichlorophenyl)-D-xylo-heptono-1,4-lactone (55). Mesylation of 33 and then acetylation gave 2,3,4-tri-O-acetyl-5,6-dideoxy-6-C-(2,4-dichlorophenyl)-1-O-methanesulfonyl-D-xylo-hexitol (63), which was converted via its 1-thiobenzoate into bis[1,5,6-trideoxy-6-C-(2,4-dichlorophenyl)-D-xylo-hexitol] 1,1'-disulfide (65). Acetylation of 65, followed by permanganate oxidation and deacetylation, afforded sodium 6-(2,4-dichlorophenyl)-D-xylo-2,3,4-trihydroxy-hexanesulfonate (67). Both 57 (obtained from 55 by hydrolysis with NaOH) and 67 are weak inhibitors of HMG-CoA reductase.
Stereoselective formation of tetrahydrofurans during allyltrimethylsilane additions to L-xylose derivatives
作者:Ronald A. Veloo、Martin J. Wanner、Gerrit-Jan Koomen
DOI:10.1016/s0040-4020(01)89027-x
日期:——
Stereoselective addition reactions to the aldehyde function of some L-xylose derivatives, under the influence of Lewis acid catalysts, lead to the formation of tetrahydrofuran derivatives at low temperatures, depending on the acetal protecting groups used. Via separate reactions it was shown, that these tetrahydrofurans seemed to be intermediates in the formation of homoallyl alcohols.
Abstract Acetolysis of ( Z )-1- O -acetyl-2,4- O -benzylidene-5,6-dideoxy-6- C -(2,4-dichlorophenyl)-3- O -methanesulfonyl- d - xylo -hex-5-enitol afforded ( E )-1,2,4-tri- O -acetyl-5,6-dideoxy-6- C -(2,4-dichlorophenyl)3- O -methanesulfonyl- d - xylo - and - l - arabino -hex-5-enitol, 2- C -[( R )-acetoxy(2,4-dichlorophenyl)methyl]-3,6-di- O -acetyl-2-deoxy-4- O -methanesulfonyl-β- l - galacto -
4-dichlorophenyl)-D-xylo-hex-5-enit ol and 2-C-[(R)-acetoxy(2,4-dichlorophenyl)methyl]-3,4,6-tri-O-acetyl-2-deoxy- beta-L-galacto- and -beta-L-gulo-hexopyranosylbenzene. The mechanism of this new rearrangement was studied by exchanging the substituents at C-1 and C-3 in 3 and those of the aromatic ring attached to C-6.