1402044-32-9Relevant academic research and scientific papers
Synthesis and characterization of sulfated gal-β-1,3/4-GlcNAc disaccharides through consecutive protection/glycosylation steps
Tu, Zhijay,Hsieh, Hsiao-Wu,Tsai, Chih-Ming,Hsu, Chia-Wei,Wang, Shy-Guey,Wu, Kuan-Jung,Lin, Kuo-I,Lin, Chun-Hung
supporting information, p. 1536 - 1550 (2013/07/26)
We have developed an expeditious procedure to yield large amounts of orthogonally protected Gal-β1,3/4-GlcNAc, which allowed for the systematic introduction of a sulfate group onto the C3/C6 positions of Gal and/or the C6 position of GlcNAc. In particular
Challenging deprotection steps during the synthesis of tetra- and pentasaccharide fragments of the LeaLex tumor-associated hexasaccharide antigen
Guillemineau, Micka?l,Auzanneau, France-Isabelle
, p. 8864 - 8878 (2013/01/15)
We report the convergent synthesis of two novel tetrasaccharide and two novel pentasaccharide fragments of the LeaLex TACA: the tetrasaccharides contain neither the galactose at the Lea nonreducing end nor the fucose at the Lex reducing end; the pentasaccharides only lack the galactose residue at the Lea nonreducing end. Two of the analogues were prepared as hexyl glycosides to be used in NMR experiments and as soluble inhibitors in binding studies and two as 6-aminohexyl glycosides to be conjugated to carrier proteins. Our strategy relied on stepwise extensions using excess monosaccharide glycosyl donors (trichloroacetimidates and thioglycosides) in sequential glycosylation reactions. The protecting groups were chosen to limit the number of deprotection steps required to obtain the final derivatives. While this strategy ensured that all glycosylation reactions proceeded in very good yields (70-84%), deprotection of the oligosaccharide intermediates was challenging. Global deprotection using Birch metal dissolving conditions did not remove the tert-butyldiphenylsilyl group, which indeed was incompatible with such reaction conditions. Attempts to remove the TBDPS with tetrabutylammonium fluoride was unsuccessful and led to a complex mixture of compounds that could not be separated. The desired hexyl and aminohexyl tetrasaccharides were finally obtained after four- and five-step deprotection sequences, respectively. Deprotection of the pentasaccharide intermediate to give the hexyl and aminohexyl analogues also led to unexpected results. Indeed, during Zemplén deacylation, a chloroacetamide chlorine atom was displaced by methoxide ions leading to the corresponding methoxyacetamide. Once the chloroacetamide was fully reduced to an acetamide the pentasaccharides were obtained in four and five steps, respectively.
