- Short de novo synthesis of fully functionalized uronic acid monosaccharides
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(Chemical Equation Presented) Short and Sweet: A convergent route leads to orthogonally protected D-glucuronic and L-iduronic acid thioglycoside building blocks, commonly used in heparin oligosaccharide assembly (see scheme). Rapid access to substantial q
- Timmer, Mattie S. M.,Adibekian, Alexander,Seeberger, Peter H.
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p. 7605 - 7607
(2007/10/03)
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- Cyano/diallylamine additions to glycoside and nucleoside aldehydes and its application to the synthesis of polyoxin L and uracil polyoxin C
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Three efficient, high yielding syntheses of precursors (1) of carbamoylpolyoxamic acid from L-arabinose, based on the simultaneous addition of the acid and amine functionalities, are described. Utilizing the same methodology and uridine as the starting ma
- Kutterer, Kristina M. K.,Just, George
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p. 1409 - 1420
(2007/10/03)
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- Synthesis of 4-cyanophenyl 4-azido-4-deoxy-1,5-dithio-β-D-xylopyranoside
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L-Arabinose diethyl dithioacetal was converted, via its 4-azido-5-S-benzoyl-4-deoxy-2,3-O-isopropylidene-5-thio-D-xylose diethyl dithioacetal, into 4-azido-4-deoxy-5-thio-α-D-xylopyranose triacetate 29. Glycosidation of 29 with 4-cyanothiophenol in the presence of trimethylsilyl triflate gave the 4-cyanophenyl 2,3-di-O-acetyl-4-azido-4-deoxy-1,2-dithio-α- and -β-D-xylopyranosides 31 and 33 as well as 3-O-acetyl-2,5-anhydro-4-azido-4-deoxy-5- thio-D-lyxose bis(4-cyanophenyl) dithioacetal 34 in a 8:2:1 respective ratio. Treatment of 29 with hydrogen bromide in acetic acid yielded a 1:4 mixture of 2,3-di-O-acetyl-4-azido-4-deoxy-5-thio-D-xylopyranosyl bromide 38 and 2,3 -di-O-acetyl-5-bromo-5-deoxy-4-thio-L-arabinofuranosyl bromide 40. Reaction of the mixture of bromides 38 and 40 with 4-cyanothiophenol in the presence of potassium carbonate afforded the expected 31 and 33 only in traces, while 2-(1R,2S,-1,2-di-O-acetyl-1,2-dihydroxy-but-3-en-1-yl)-5-cyano-1,3 dithiole and 4-cyanophenyl 2,3-di-O-acetyl-5-S-(4-cyanophenyl)-1,4,5-trithio-α-L-arabinofuranoside (42) were isolated in 18% and 20% yield, respectively. The formation of these two derivatives is tentatively explained by involvement of a radical reaction mechanism. When O-(2,3-di-O-acetyl-4-azido-4-deoxy-5-thio-α-D-xylopyranosyl) trichloroacetimidate was used as donor and boron trifluoride ethyl etherate as promoter, 31 and 33 were formed in excellent yield (96%) in a 2:1 ratio. The glycosides, obtained on deacetylation of 33, 34, and 42 showed a significant antithrombotic activity on rats.
- Bozo, Eva,Boros, Sandor,Kuszmann, Janos
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p. 149 - 162
(2007/10/03)
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- The Synthesis of Optically Pure Epoxyalkyl β-D-Glucosides and β-Cellobiosides as Active-Site Directed Inhibitors of Some β-Glucan Hydrolases
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(2R)- and (2S)-2,3-Epoxypropyl, (3R)- and (3S)-3,4-epoxybutyl and (4S)-4,5-epoxypentyl β-D-glucopyranoside, together with the (3R)- and (3S)-3,4-epoxybutyl β-cellobioside, have been prepared by condensation of a glycosyl bromide with the appropriate enantiomer of a chiral alcohol containing a diol protected as an isopropylidene acetal, and subsequent manipulation of the unmasked diol to the epoxide function.As well, in an improvement to the whole process, both diastereoisomers of the various epoxypropyl and epoxybutyl glycosides were available, from just the one enantiomer of the alcohol by an alternative manipulation of the diol.Finally, precursors to 2,3-epoxy-4-hydroxybutyl β-D-glucosides and β-cellobiosides were prepared in high optical purity by Sharpless asymmetric epoxidation of the appropriate 4-hydroxybutyl-2-enyl glycosides.
- Rodriguez, Evelyn B.,Scally, Gavin D.,Stick, Robert V.
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p. 1391 - 1405
(2007/10/02)
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- Crystalline 2,3:4,5-di-O-isopropylidene-DL-arabinose diethyl dithioacetal: some reactions of acetal derivatives of arabinose.
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Acetonation of the diethyl dithioacetals of D- and L-arabinose gives the corresponding 2,3:4,5-diisopropylidene acetals (2a and 2b) as oils having [alpha]D +82 and -81 degrees, respectively; in admixture, the enantiomers form a well crystallized racemate, m.p. 43-45 degrees. The initial product of acetonation is the 4,5-monoisopropylidene acetal. Demercaptalation of 2a with mercury(II) chloride-cadmium carbonate gives 2,3:4,5-di-O-isopropylidene-aldehydo-D-arabinose (5) in high yield, but the literature procedure employing mercury(II) chloride-mercury(II) oxide affords a mixture of 5 and 1,2:3,4-di-O-isopropylidene-beta-D-arabinopyranose (6). A trace of acid readily and completely converts the aldehydo derivative 5 into the cyclic diacetal 6.
- Horton,Varela
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p. 205 - 214
(2007/10/02)
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- Synthesis of ring A of ambruticin and proof of its absolute stereochemistry
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Appropriately derivatized ambruticin was converted by reductive ozonolysis to tetrahydropyran 9c and cyclopropane 12a, which were synthesized from L-arabinose and (R)-Feist's acid in an unambiguous manner.
- Just, George,Potvin, Pierre
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p. 2173 - 2177
(2007/10/02)
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