ISSN:
0947-3440
Keywords:
S-Glycosylation, base-promoted, acid-catalyzed
;
S-Glycosides
;
Anomeric S-alkylation
;
Glycosyltrichloroacetimidates
;
Lewis X analogues
;
Oligosaccharides, thio-
;
Carbohydrates
;
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The synthesis of thio-linked Lewis X and sialyl Lewis X-derived epitopes 3-5 has been achieved using a small number of building blocks. The key building-block was 1-O-silyl-protected 4-S-acetyl-2,6-di-O-benzoyl-3-S-(2,3,4-tri-O-acetyl-α-L-fucopyranosyl)-3,4-dithio-β-D-glucopyranose (15), which was obtained from the fucosyl donor 6 together with 3-thiogalactose 7 as the acceptor. Their acid-catalyzed S-glycosylation afforded the thio-linked disaccharide 8 which was subsequently converted to the 4a-O-unprotected derivative 12. Conversion to the 4a-triflate followed by treatment with KSAc in tetrahydrofuran led, under inversion of configuration, to 15 in good overall yield. Selective removal of the S-acetyl group followed by base-promoted S-glycosylation with acetobromogalactose gave the acyl-protected Lewis X analogue 25. Acetobromogalactose gave the acyl-protected Lewis X analogue 25. Transformation into trichloroacetimidate 27, followed by acid-catalyzed S-glycosylation of heptylthiol and complete deacylation afforded target molecule 3. Similarly, acid-catalyzed reaction of donor 27 and the 3b,4b-O-unprotected lactose derivative 31 as acceptor led to pentasaccharide 32, complete deacylation of which afforded target molecule 4. Transformation of 15 into the donor trichloroacetimidate 34, followed by acid-catalyzed S-glycosylation of heptylthiol afforded thioglycoside 35. Selective removal of the S-acetyl group and subsequent base-promoted S-glycosylation with the known donor 37 furnished the thio-linked tetrasaccharide 38. Cleavage of all the O-acyl groups and hydrolysis of the methyl ester moiety afforded the sialyl Lewis X analogue 5.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jlac.199719970705
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