Glycosyl thiocyanates

From Glycosyl Thiocyanates by Reaction with Grignard Reagents. 183... 

Acylated glycosyl thiocyanates are made by treatment of acylated glycopyranosyl halides with potassium thiocyanate.30 Reaction at —40° with a Grignard reagent affords alkyl or aryl 1-thioglycosides.54... 

Kochetkov and coworkers have reported [154—156] an efficient approach for the synthesis of 1,2-cis pyranosides employing 1,2-trcms-glycosyl thiocyanates as glycosyl donors and tritylated sugar derivatives as glycosyl acceptors (Scheme 4.5). This... 

The glycosyl thiocyanates can be transformed into thioglycosides through cleavage to the thioaldose by treatment with sodium methoxide under mild conditions followed by alkylation, or by a Grignard reaction which directly gives the thioglycoside (mannose-a-D-thiocyanate was inert) (O Scheme 38) [138]. 

Miiller and Wilhelms applied the Fischer glycosyl thiocyanate method to the preparation of 6-deoxy-6-thiocyano-D-glucose and further explored the synthesis of l-D-glucosyl-2-thiourea. These workers have examined the question of the isomerization of thiocyanates and isothiocyanates, and have made some observations which should prove exceedingly useful. 

In the area of deoxyhexose-based disaccharides, the isomalto di- and tri-saccharide compounds devoid of oxygen at C-2 have been produced by standard methods. 3-O-a-D-Fucopyranosyl-D-glucose has been synthesized with 0-2 of the fucose unit carrying a methyl group,and 6-O-a-L-rhamnopyranosyl-D-glucose has been prepared as a fully substituted glycosyl thiocyanate and used in the synthesis of a rhamnoglucan polysaccharide. ... 

A new route to 1,2-tronr-glycosyl thiocyanates, such as the glucose derivative 5, involved opening of 1,2-anhydrosugars with ammonium thiocyanate and phase transfer catalyzed reaction of glycosyl halides with < -ethyl-S potassium dithiocarbonate proved to be an efficient new method for the preparation of the known 5-glycosyl xanthates 6. ... 

---