C2-Oxyanion Neighboring Group Participation: Transition State Structure for the Hydroxide-Promoted Hydrolysis of 4-Nitrophenyl alpha-D-Mannopyranoside
Gaetano Speciale, Marco Farren-Dai, Fahimeh S Shidmoossavee, Spencer J Williams, Andrew J Bennet
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY | AMER CHEMICAL SOC | Published : 2016
The hydroxide-catalyzed hydrolysis of aryl 1,2-trans-glycosides proceeds through a mechanism involving neighboring group participation by a C2-oxyanion and rate-limiting formation of a 1,2-anhydro sugar (oxirane) intermediate. The transition state for the hydroxide-catalyzed hydrolysis of 4-nitrophenyl α-d-mannopyranoside in aqueous media has been studied by the use of multiple kinetic isotope effect (KIE) measurements in conjunction with ab initio theoretical methods. The experimental KIEs are C1-2H (1.112 ± 0.004), C2-2H (1.045 ± 0.005), anomeric 1-13C (1.026 ± 0.006), C2-13C (0.999 ± 0.005), leaving group oxygen 2-18O (1.040 ± 0.012), and C2-18O (1.044 ± 0.006). The transition state for t..View full abstract
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Awarded by Natural Sciences and Engineering Council of Canada (NSERC)
Awarded by Australian Research Council
A.J.B. thanks the Natural Sciences and Engineering Council of Canada (NSERC) for financial support (Discovery Grant 121348-2012). S.J.W. thanks the Australian Research Council for financial support (FT130100103; DP120101396). M.F.-D. thanks NSERC for a graduate scholarship (PGS-M). The authors thank Prof. Vern Schramm and Dr. Zhen Wang (Albert Einstein College of Medicine) for providing computational training to M.F.-D.