Heptasaccharide, synthesis

Scheme 4.21 Mukaiyama s one-pot synthesis of phytoalexin-elicitor active heptasaccharide.

Scheme 1.7 Solid-phase synthesis of an immunogenic heptasaccharide by van Boom et al.

Scheme 5.2 (a) Monosaccharide building blocks 1-3 selected for solid phase synthesis of heptasaccharide 16 (b) attachment of the first carbohydrate onto phenolic polystyrene through a new photocleavable o-nitrobenzyl-type linker29 (Bn = benzyl, Bz = benzoyl, Fmoc = 9-fluoromethyloxycarbonyl, Ph = phenyl, py = pyridine, TBDPS =t-butyldiphenylsilyl). 

Ley and coworkers13-18 are responsible for setting much of the stage on which our work is played. Showcased by the synthesis of the heptasaccharide shown in Scheme... 

Unverzagt, C., Synthesis of a Bianteimary Heptasaccharide by Regioselective Glycosylations. Uwgew. Chem. Int. Ed. 1994,33,1102-1104. 

P. FOgedi, W. Birberg, P. J. Garegg, and A. Pilotti, Synthesis of a branched heptasaccharide having phytoalexin-elicitor activity, Carbokydr. Res 164 797 (1987). 

Synthesis of the dolichol-linked oligosaccharide. The reaction starts on the cytosolic side of the endoplasmic reticulum. Seven single-step reactions lead to the heptasaccharide that is linked to dolichol... 

The octasaceharide which carries an additional A -acetylglucosamine at the reducing end in comparison to the heptasaccharide was prepared by an independent synthesis. This compound shows a different conformational behavior than the heptasaccharide [122]. The minimum energy conformation, as calculated by the GESA program, shows the trisaccharide at the 6-position of the P-mannose bent back towards the reducing end. This particular effect is in qualitative agreement with the observation of the conformational difference between the tri- and the pentasaccharide described above. The NMR analysis of this octasaceharide confirms the calculated structure. One important fact for the correct prediction of the conformational data was the simultaneous treatment of all independent parameters in the optimization procedure (Table 8). 

Scheme 12.22. Synthesis of heptasaccharide 147 using the armed-disarmed glycosylation approach, byjona and co-workers [75],...

Nakabayashi, S., Warren, C.D., and Jeanloz, R.W. (1988) The preparation of a partially protected heptasaccharide-asparagine intermediate for glycopeptide synthesis. Carbohydr. Res. 174, 279-289. 

Nicolau, K. C., Winssinger, N., Pastor, J., and DeRoose, F. (1997) A general and highly efficient solid phase synthesis of oligosaccharides. Total synthesis of a heptasaccharide phytoalexin elicitor (HPE)../. Am. Chem. Soc. 119,449—450. 

The addition of a second, reducing end acceptor and a thiophilic promoter (NIS) resulted in trisaccharide formation. Yields as high as 84% for the overall process were reahzed, showcasing the efficiency of this strategy as well as the promoter compatibility, which can be a problem (Fig. 3). The method has been extended to branched structures as well (34). Takahashi has advanced the orthogonal OPG strategy in an impressive synthesis of the heptasaccharide phytoalexin elicitor (HPE) in 24% overall yield (35). 

An example of this strategy is the synthesis of the heptasaccharide (52) which has phytoelicitor activity [14]. As shown in the retrosynthetic analysis (Scheme 5.10), the heptasaccharide (52) is disconnected into the trisaccharide thioglycoside (53) and the simple D-glucose derivative (54). The trisaccharide block (53) is available from the glycosyl bromides (55,56) and the thioglycoside (57). 

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