Carbohydrates thioureas from

More recently, it has been reported that primary amines derived from cinchona alkaloids [75] as well as proline derivatives [76], combined with achiral Brpnsted or Lewis acids, may also efficiently catalyze the enantioselective Biginelli reaction. Alternatively, a carbohydrate-based bifnnctional primary amine-thiourea catalyst was developed for this transformation, with similar enantiocontrol [77]. 

A stereocontrolled general synthesis of C-nucleosides from non-carbohydrate materials has been described, illustrated in Scheme 9 for pseudo-uridine derivatives (69) (R = H, Me, CsHn, or Ph R = H) a branched-chain sugar derivative (69) (R = R = Me) was analogously prepared. 2-Thio-pseudouridine and pseudoisocytidine were also obtained from the intermediate (70) (R = R = H) using thiourea and guanidine respectively in place of urea, and this intermediate was also converted to the maleimido C-nucleoside, showdomycin. ... 

Fig. 12 Schematic representation of a mAb and an SIP fragment showing some common linkages for PS conjugation A a carbohydrate moiety conjugated through an A/ -ethylideneacetohydrazide B a lysine residue coupled via an amide bond ora thiourea C a pair of thiol groups from reduced disulphide bonds on cysteine residues coupled to a maleimide through a thioeter.

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