Oligosaccharide synthesis linker method

It has long been recognized that polymeric supports for oligosaccharide synthesis do not need to be insoluble.33 Wang et al. applied the sulfoxide glycosylation method to the synthesis of disaccharide 79 (Scheme 3.14). The key feature of this work was the base-labile linker. Sulfoxide 74 was used to glycosylate polyethylene glycol... 

Table 2. Major linkers used in one-phase (solution) oligosaccharide synthesis showing chemical structure of the linker, glycosylating agent, and removal methods used. 

The power of the HR-MAS method for on-resin analysis has been further underscored in the development of new linkers. Without this method, only indirect analytical data after removal from the resin was available. Direct assessment of the resin-bound linker greatly facilitated the introduction of a 4,5-dibromo octane- 1,8-diol linker that was converted into an octane-1,8-diol linker cleavable by olefin metathesis at the end of the synthesis.6 The disappearance and reappearance of the olefinic protons as well as the growing oligosaccharide chain was clearly visible in the H spectrum (Fig. 8.7).7... 

Nishimura and coworkers 29f> 297 described a novel method for the enzymatic synthesis of oligosaccharide derivatives employing an a-chymotrypsin sensitive linker. The synthesis of the water soluble GlcNAc-polymer 197, sensitive to a-chymotrypsin, is shown in Fig. 18-27. Oxazoline derivative 193 was coupled with 6-(N-benzyloxycarbonyl-L-phenylalanyl)-amino-hexanol-l (194) followed by N-depro-tection of the phenylalanine and subsequent condensation with 6-acrylamido caproic acid 195. De-O-acetylation gave the polymerizable GlcNAc derivative 196. Finally, copolymerization of acrylamide and monomer 196 in the presence of ammoniumper-sulphate (APS) and N,N,N, N -tetramethyl ethylene diamine (TMEDA) gave the... 

---