Scheme 4. Mechanistic studies on glycosylation: α/β-5a doesn't epimerize under reaction conditions. 13 is a viable catalyst (84% yield of 5a). Reaction of D₂O with 3a gives addition of C–D and C–O bonds to same face of 3a. Schreiner's catalyst and thiouracil give the same outcomes in glycosylation of CD₃OD.