Scheme 1. (a) Galan and McGarrigle's thiourea-catalyzed glycosylation reaction;3 (b) Schreiner's THP-protection of alcohols;6 (c) original proposal with catalyst acting as a double hydrogen-bond donor to alcohol;3 (d) analogue of Pápai2 proposal with catalyst acting as a Brønsted acid and accepting a H-bond from the alcohol.