Reactivity tuning

Premathilake, H. D. Demchenko, A. V. In Reactivity Tuning in Oligosaccharide Assembly, Fraser-Reid, B., Lopez, J. C., Eds. Topics in Current Chemistry 301 Springer Berlin, 2011, pp. 189-221. 

Cheung, M K, Douglas, N L, Hinzen, B, Ley, S V, Pannecoucke, X, One-pot synthesis of tetra- and pentasaccharides from monomeric building blocks using the principles of orthogonality and reactivity tuning, Synlett, 257-260, 1997. 

Similar to the reactivity tuning of sialyl donors mentioned above, it was found that the modification of the C5 acetamido group or its substitution by other functionalities also raises the reactivity of the C8 hydroxyl of sialic acid. Boons and co-workers originally synthesized iV,iV-diacetyl sialyl acceptor 144, which was applied to the sialylation with lV,lV-diacetyl sialyl donor 93 in MeCN at —40 °C. In comparison to iV-acetyl sialyl acceptor 145, the sialylation produced Q -(2-8)-disialic acid 146 in raised yield (50%, aip = 2/1) (O Scheme 40) [94,95]. 

L. Huang, Z. Wang, and X. Huang, One-pot oligosaccharide synthesis Reactivity tuning by postsynthetic modification of aglycone, Chem. Commun., (2004) 1960-1961. 

D. K. Baeschlin, L. G. Green, M. G. Hahn, B. Hinzen, S. J. Ince, and S. V. Ley, Rapid assembly of oligosaccharides 1,2-diacetal-mediated reactivity tuning in the coupling of glycosyl fluorides, Tetrahedron Asymmetry, 11 (2000) 173-197. 

Huang L, Wang Z, Hnang X. One-pot oligosaccharide synthesis reactivity tuning by post-synthetic modification of aglycon. Chem Commun 2004 1960-1961. 

Douglas et al. [19]. discovered that the cyclohexane-1,2-diacetal (CDA) protection group (e.g., 48) (Fig. 5.13) as weU as the octahydro-2,2 -bi-2H-pyran-2,2 -diyl (dispoke) group (e.g., 47) had a reactivity tuning effect between that of the fully... 

Notes and discussion. This reaction demonstrates the use of V-iodosuccinimide (NIS) in conjunction with catalyticsilyl triflate (in this case trimethylsilyl triflate). These are currently the most commonly used conditions for the activation of phenyl selenoglycosides. It is also an excellent example of reactivity tuning, and as mentioned previously, this is one of the major applications of phenyl selenogly coside donors. In this system the butane diacetal and Chloroacetyl protecting groups disarm the acceptor electronically and conformationally. Variation of the triflate may be required in order to optimise to reaction conditions if applied to a different system. 

Scheme 6.1 Oligosaccharide assembly traditional concept (left) and by reactivity tuning of glycosyl donors (right).

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