Iterative one-pot syntheses of chitotetroses

Huang, Lijun; Wang, Zhen; Li, Xiaoning; Ye, Xin‐shan; Huang, Xuefei

doi:10.1016/j.carres.2006.01.007

Cited by 57 publications

(43 citation statements)

References 49 publications

(9 reference statements)

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“…[29] This is particularly advantageous for syntheses of oligosaccharides, which consist of repeating units, as the same building blocks can be used repeatedly without resorting to anomeric reactivity adjustments. [28,29] Herein, we explore the applicability of the iterative one-pot method in construction of the highly challenging sHA.…”

Section: Resultsmentioning

confidence: 99%

“…[28,29] Moreover, unlike the traditional reactivity based one-pot approach where glycosylation reactions must be performed in the order of decreasing donor anomeric reactivity values, [30,31] it is not necessary to fine-tune anomeric reactivities using the pre-activation method. [29] This is particularly advantageous for syntheses of oligosaccharides, which consist of repeating units, as the same building blocks can be used repeatedly without resorting to anomeric reactivity adjustments.…”

Section: Resultsmentioning

confidence: 99%

“…Sequential one-pot reactions of 26, [28] 21 and 22 following the reaction protocol A produced pentasaccharide 28 (65% yield) (Table 2, entry 2, protocol A). The other possible pentasaccharide sequence 29 with glucose at the reducing end was rapidly synthesized through consecutive condensations of four components, that is, 11, 2, 21 and 27 [25] (Table 2, entry 3, protocol B), in 55% overall yield for the one-pot reactions.…”

Section: One-pot Syntheses Of Shamentioning

confidence: 99%

“…Finally, we decided to introduce the tert-butyldimethylsilyl (TBS) moiety into the glucosyl donor (donor 11), due to beneficial effects of TBS on glycosylation in our previous chitotetraose syntheses. [28] Thioglucosyl donor 11 was prepared from p-tolyl-1-thio-β-D-glucopyranoside (16), [31] which was first protected with p-methoxybenzylidene (Scheme 1). Dibutyltin oxide mediated selective benzylation [38] followed by benzoylation gave thioglycoside 8 in 66% yield over three steps.…”

Section: Building Block Evaluationsmentioning

confidence: 99%

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Highly Efficient Syntheses of Hyaluronic Acid Oligosaccharides

Huang

2006

Chemistry A European J

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Highly efficient syntheses of hyaluronic acid oligosaccharides have been accomplished through the pre-activation based iterative one-pot strategy. A series of oligosaccharides ranging from di-to hexasaccharides were rapidly assembled using only near stoichiometric amounts of the building blocks without aglycon adjustment or purifications of intermediate oligosaccharides. Deprotection and oxidation protocols were developed for protective group removal and oxidation-state adjustment. The availability of such structurally well defined synthetic hyaluronic acid oligosaccharides will greatly facilitate the establishment of detailed structure-function relationships.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: One-pot Syntheses Of Shamentioning

confidence: 99%

Section: Building Block Evaluationsmentioning

confidence: 99%

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Highly Efficient Syntheses of Hyaluronic Acid Oligosaccharides

Huang

2006

Chemistry A European J

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“…Multiple glycosylations can be performed in a single reaction flask without intermediate oligosaccharide purifications, thus significantly expediting the glycoassembly process. We have demonstrated that this is a powerful methodology, which has been successfully applied in syntheses of linear oligosaccharides, including hyaluronic acid oligosaccharides, 14 heparin trisaccharides, 15 chitotetraose, 16 and GloboH. 17 Herein, we report the application of the pre-activation based methodology to one-pot construction of branched oligosaccharides.…”

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Syntheses of Lewis^X and Dimeric Lewis^X: Construction of Branched Oligosaccharides by a Combination of Preactivation and Reactivity Based Chemoselective One-Pot Glycosylations

et al. 2007

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Two asymmetrically branched oligosaccharides, Lewis X and dimeric Lewis X were assembled in onepot with high yields and exclusive regio-and stereo-selectivities. p-Tolyl thioglycosides were utilized as the sole type of building blocks, thus simplifying the overall synthetic design. The reactivity independent nature of the pre-activation based method allows modular assembly of the dimeric Lewis X octasaccharide without the need for tedious protective group manipulation to achieve exact anomeric reactivities.The Lewis family of oligosaccharides, as represented by Lewis X pentasaccharide 1 and dimeric Lewis X octasaccharide 2, is involved in a wide array of biological events, such as modulation of immune system towards a Th2 response, 1 bacterial and viral infection. 2,3 In addition, they are known to be over-expressed on tumor cell surface, 4,5 thus providing a promising target for carbohydrate based anti-cancer vaccine studies. 6 With their biological significance, structural and stereochemical complexities, Lewis antigens have served as targets for the development of new synthetic methodologies, 7,8 including automated solid phase synthesis, 9 automated parallel synthesis in solution, 7 soluble polymer supported synthesis, 10 and reactivity based chemoselective glycosylation. 11,12Recently, we have developed a pre-activation based chemoselective one-pot glycosylation method, where a thioglycosyl donor is activated in the absence of an acceptor. 13 Upon completion of the activation, addition of a thioglycosyl acceptor will lead to the formation of a disaccharide containing a thioaryl aglycon, ready for the next round of pre-activation and Xuefei.huang@utoledo.edu. || These authors have contributed equally to this work. It is a challenging task to assemble Lewis antigens 1 and 2 in one pot. It is well known that 4-hydroxyl group of glucosamine derivatives has very low nucleophilicity. 18 In addition, fucosylation on 3-OH needs to be carried out with high α selectivity for efficient one pot synthesis. The in situ anomerization procedure for introducing α fucosyl linkage 19,20 is not applicable since the reaction condition cannot be extended to β glycosylations. Furthermore, the rate of glycosylation using in situ anomerization procedure is low requiring room temperature overnight, which is undesirable for multiple sequential glycosylations in one pot. NIH Public AccessTo overcome these difficulties, we designed building blocks 3 to 8 with glucosamine diol 6 serving as a key compound. Keeping C3 hydroxyl group of 6 unprotected reduces steric hinderance to C4 hydroxyl group thus increasing its nucleophilicity. In addition, this allows fucosylation on C3-OH immediately following β-glycosylation of C4-OH without the need to remove C-3 protective group. The N-Phth moiety in 6 is crucial to ensure exclusive regioselectivity for β-galactosylation of 4-OH, as smaller Troc, 21 azido or acetamido groups 22 on C-2 led to regio-isomers. Diol 8 was examined initially as the lactoside acceptor with its axial 4-OH assumed...

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