A-mannoside linkage

Results of the conformational analysis of the biantennary tetrasaccharide by NMR and GESA calculations showed no changes for the a-(l-3) and the a-(l-6) bonds in comparison to the corresponding linear trisaccharides, which proves that the two a-mannosidic linkages are independent of each other (Table 6) [30],... 

Much information is yet needed before we know how a Man-T distinguishes GDPMan from other sugar nucleotides, and what structural features are correlated with the ability of closely-related Man-T to form different a-mannosidic linkages or to transfer Man-P (as can different members of the Ktrlp family (section 8.4.2)). 

The potential of the mannuronate ester donors in the formation of the p-mannosidic linkage has been demonstrated with the construction of a mannuronic acid alginate pentamer using a convergent orthogonal glycosylation.64... 

Scheme 9.12 Reverse use of a polymer support for the synthesis of P-mannoside linkage. The synthetic helper arm (MPEG), together with other polymer-bound by products, is removed from the desired product by simple precipitation.

Other human O-glycosylation deficiencies that are not detectable by IEF of ApoC-III affect oligosaccharides in O-mannosidic linkage to a-dystroglycan in Walker-Warburg syndrome and muscle-eye-brain disease [2, 32], and fucosylated N- and... 

Ichishima, E., Arai, M., Shigematsu, Y., Kumagai, H., and Sumida-Tanaka, R. (1981). Purification of an acidic a-D-mannosidase from Aspergillus saitoi and specific cleavage of 1,2-a-D-mannosidic linkage in yeast mannan. Biochim. Biophys. Acta, 658,45-53. 

EC 3.2.1.101 mannan endo-1,6-a-mannosidase Random hydrolysis of 1,6-a-D-mannosidic linkages in unbranched 1,6-mannans... 

By utilizing the Ouchterlony technique of two-dimensional, agar-gel diffusion, Slodki and his colleagues investigated the interaction of con A with O-phosphonomannans.363 They suggested a possible correlation between the extent of precipitate formation with con A and the content of a-D-(l— 2)-mannosidic linkages. 

Dehydrative glycosylation, which utilizes reducing sugar as a donor, was developed by Gin et al. [69]. Seeberger et al. demonstrated that this reaction can be applied to the formation of )5-mannosidic linkages [70] (O Scheme 22). 

An interesting twist on the orthoester approach was uncovered by Fraser-Reid and coworkers in which it was revealed that a 4-pentenyl orthobenzoate 123, on activation with ytterbium triflate in dichloromethane, was able to selectively glycosylate the primary hydroxyl group in a mannopyranosyl 2,6-diol 122. Treatment with a 2-O-benzoyl mannosyl trichloroacetimidate 126 in diethyl ether with the same promoter then introduced a second y-mannosidic linkage to the remaining secondary hydroxyl group (Scheme 22).30 This selectivity pattern was central to the development of a very efficient synthesis of a branched pentadecamannan 129. 

Figure 10-6 The pentasaccharide core of all asparagine glycoproteins contains a /9-mannoside linkage.

---