Stereoselective sulfoxidation of α-mannopyranosyl thioglycosides: the exo-anomeric effect in action

Abstract

As a consequence of the exo-anomeric effect, and in contrast to their β-anomers, α-thioglycosides undergo stereoselective oxidation to give very predominantly the R-sulfoxides, as revealed by X-ray crystallography.

References

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17. Crystal data for 20: C₁₄H₂₄O₆S, M= 320.39, monoclinic, a= 11.282(7), b= 9.766(10), c= 15.555(12)Å, β= 99.73(6)°, V= 1689(2)ų; P2₁, Z= 4 (two independent molecules per asymmetric unit), µ= 0.22 mm^–1. Of 3381 reflections measured at room temperature, 3163 independent reflections were used in refinement on F². Final agreement factors for 390 least-squares parameters for 1887 data with I > 2 σ(I)(with values for all independent reflections in parentheses): R= 0.0412 (0.0830), R_w= 0.0984 (0.1217), GOF = 1.032 (1.131). For 22: C₁₅H₂₀O₆S, M= 328.37, monoclinic, a= 5.1509(2), b= 12.9187(4), c= 11.4762(5), β= 95.554(2)°, V= 760.07(8)ų, P2₁, Z= 2. µ= 0.24 mm^–1. Of 2613 reflections measured at T= 173 K, there were 1718 independent reflections used in refinement against F² with 1551 having I > 2σ(I). Final agreement factors for 199 least-squares parameters (with values for all independent reflections in parentheses): R= 0.0864 (0.1039), wR2 = 0.2847 (0.2582), GOF = 2.415 (2.414). CCDC 182/1088. The crystallographic data is available as a .cif file: see http://www.rsc.org/suppdata/cc/1998/2763/.