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Effect of 2‑O‑Benzoyl para-Substituents on Glycosylation Rates

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journal contribution
posted on 29.06.2018, 18:32 by Lulu Teressa Poulsen, Mads Heuckendorff, Henrik H. Jensen
From a series of competition experiments, we have explored the degree to which various para-substituents (CN, Br, H, OMe, pyrrolidino) of a 2-O-benzoyl functionalized glucosyl donor of the thioglycoside type affect the rate of glycosylation under N-iodosuccinimide/triflic acid activation. As expected, electron-withdrawing groups were found to decrease the rate of glycosylation, whereas electron-donating groups resulted in the opposite outcome, underscoring the influence on the reaction rate exerted by a participating group. On this basis, a Hammett linear free-energy relationship was established (R2 = 0.979, ρ = 0.6), offering fundamental insight into the magnitude of anchimeric assistance in glycosylation chemistry.