Sugar thiourea synthesis

An impressive number of papers has appeared in the past few years based on the use of sugar thioureas as intermediates in the synthesis of the naturally occurring potent trehalase inhibitor trehazolin (251) and of several isomers.52 396-404 The key reaction step involved the cyclization of an A,iV-disubstituted a-D-glucopyranosyl-aminocyclitol (a-D-glucopyranosyl-... 

The synthesis of imidazo[2,l-h]thiazolium-3-olate zwitterions such as (100) from sugar thiourea derivatives, and their cycloaddition reactions to form imidazo[l,2-fl]pyridin-4-ones such as (101) (Scheme 10) have been detailed. ... 

C. Saitz-Barria, A. Torres-Pinedo, and F. Santoyo-Gonzalez, Synthesis of bridged thiourea calix-sugar, Synlett, 12 (1999) 1891-1894. 

The synthesis of pyranoid sugar derivatives having an episulfide group fused to the ring involves requirements of molecular geometry more critical than for episulfides on an acyclic chain. Conversion of an epoxide in a locked-ring system to an episulfide by the action of thiourea or thiocyanate ion is diflicult, because reactions of this type involve a trans-fused, cyclic intermediate (91), formation of which requires a [Pg.179]

The equilibrium mixture of these two compounds can be directly used for the preparation of sugar-derived thioureas by coupling with alkyl and aryl amines [47]. This was the first example in the literature of a thio carbamate acting as a latent isothiocyanate for the synthesis of thioureas. 

Fernandez-Bolanos JG, Lopez 0, Maya I (2003) Synthesis of O-unprotected sugar isothiocyanates and their transformation into thioureas and cyclic isoureas. In Pan-dalai S (ed) Recent Developments in Carhohydrate Research, Transworld Research Network, Trivandrum, India, p 81... 

The synthesis of p-o-glucopyranosyl-thioureas has been reported. N -Glucosylated sugar urea and thiourea derivatives such as 42 were synthesized by PhsP-induced condensation of the corresponding protected 6-azido-sugar with tetra-O-acetyl-p-D-glucopyranosyl isothiocyanate followed by either hydrolysis (HOAc, H2O) or thiolysis (H2S, silica gel), respectively, then deprotection. Acetylation of such doubly substituted thiourea derivatives led to various re-gioisomeric N- and S-acetylated derivatives. ... 

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. ... 

The most widely used synthons for the synthesis of thiooligosaccharides are the 1-thioglycoses and their synthesis has been widely studied. Approaches for the synthesis of 1,2-tra -thioglycoses include nucleophilic sulfur substitutions at the anomeric center of the glycosyl halides with either pscwdo-thiourea derivatives or other thionucleophiles [9, 10]. More recently, phase-transfer catalysis [11] and mild Lewis acid catalysed glycosidation of peracetylated sugars with thioacetic acid [12] have been applied. 

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