Sugar thiocyanates synthesis

Z. Pakulski, D. Pierozynski, and A. Zamojski, Reaction of sugar thiocyanates with Grignard reagents. New synthesis of thio glycosides, Tetrahedron, 50 (1994) 2975-2992. 

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... 

OZTs from keto sugars. An original approach for the synthesis of OZTs from carbohydrate-based a-hydroxyketones was recently published by Silva et al.4Sa who investigated the reactivity of carbohydrate-based a-hydroxyketone in the presence of thiocyanic acid. 

This article collates information on the reactivity of sugar isothiocyanates and isomeric thiocyanates, and illustrates some of the chemical properties that have contributed to the synthesis of nucleoside analogs,1719 and thio and deoxy sugars. 

The classical, Fischer7 synthesis of sugar isothiocyanates involves treatment of an acylated glycosyl halide with an inorganic thiocyanate in a polar solvent. Depending on the reactivity of the halide and the reaction conditions, either a thiocyanate or an isothiocyanate is formed directly. 

In an article that collates information not extensively treated before, Z. J. Witczak (West Lafayette) describes the synthesis, chemistry, and preparative applications of monosaccharide thiocyanates and isothiocyanates the thiocyanate anion is an ambident nucleophile of great synthetic versatility in approaches to nucleoside analogs and to thio and deoxy sugars. 

Thio-D-xylopyranose has been the sugar of this type most thoroughly investigated. Its synthesis was reported in 1961, independently and simultaneously from three different laboratories. With sodium thiocyanate, l,2-0-isopropylidene-5-0-p-tolylsulfonyl-a-D-xylofuranose (211) gives a thiocyanate that reacts with sodium sulfide to give l,2-0-isopropylidene-5-thio-a-D-xylofuranose (212). A better synthesis is the treatment of 211 with sodium thiosulfate, followed by reduction of the resultant Bunte salt with sodium boro-hydride. The same compound 212 is obtained by nucleophilic replacement of the 5-sulfonyloxy group in 211 by treatment with potassium thioacetate followed by deacetylation to 212, or by the reaction of 211 with sodium a-toluenethioxide, followed by scission of the resultant S-benzyl compound with sodium in liquid ammonia. 

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]

Tronchet s group has extended its studies of the 1,3-dipolar cycloaddition of phenylacetylene to nitrile oxide derivatives of sugars to include the synthesis of 5-phenylisoxazole derivatives of 1,2-substituted 3-azido-3-deoxy-, 3-amino-3-deoxy-, and S-trifluoroacetamido-S-deoxy-a-D-xy/o-tetrofuranose, and 3-acet-amido-3-deoxy-a-D-r/6o-tetrofuranose (171). 2-Amino-2-deoxy-D-glucose reacted with substituted-phenyl thiocyanates to yield condensed imidazolidine derivatives (172), and a j/ /ro-benzimidazoline prepared from l,2 5,6-di-(9-... 

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