Sugar isothiocyanates

For the purpose of this chapter, three types of isothiocyanate derivatives of sugars are considered, depending on the location of the NCS group in the molecule glycosyl isothiocyanates, deoxyisothiocyanato sugars, and isothiocyanate conjugates. For a complete list of structures reported, see Tables I-III. 

2-Deoxy-ot-D-arabino- hexopyranosyl 4,6-Di-0-acetyl-3-bromo- 3-deoxy Amorphous 

2-Dcoxy-o -D-lyxo-hexopyranosyl 3,4.6-Ti i-O-acetyl Syrup l 129 CII2C12 50 

Methyl (a-D-glycero-D-galar.to-2- nonulopyranosyl)onate 5 - Ace l am ido -4,7,8,9 -telr a -O-acetyl-3.5 -di deoxy 95-99 17.06 MeOII 51. 

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A straightforward preparation of pyrimidinones and pyrimidinethiones 45 involved reaction of isocyanates or isothiocyanates with the readily available starting material 44, which had previously been described by the same authors. A particularly interesting application was the use of sugar isothiocyanates to give nucleosides. Nucleophilic displacements of the sulfur groups in the products were also reported <06EJO634>. 

The preparation and reactions of V-thiocarbonyl carbohydrate derivatives, such as sugar isothiocyanates, thioamides, thioureas, thiocarbamates and their conjugates have been the subject of valuable comprehensive as well as specialized accounts, which should be consulted for details.198... 

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. 

Isomerization of organic thiocyanates to isothiocyanates is also discussed in other articles.25 29 The first sugar isothiocyanate reported, namely, 2,3,4,6-tetra-O-acetyl-/3- D-glucopyranosyl isothiocyanate (2) was synthesized by Emil Fischer7 in 1914 by treatment of 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide (1) with silver thiocyanate in anhydrous xylene. It was also prepared by Muller and Wilhelms8 by thermal isomerization of the corresponding thiocyanate 3, obtained by treatment of 1 with potassium... 

The Fischer method7 for preparation of sugar isothiocyanates is general however, many modifications have been introduced, using, for example, nonpolar solvents and silver thiocyanate,29 33 lead thiocyanate,33 or ammonium thiocyanate,34 and potassium thiocyanate in acetonitrile in the presence of tetrabutylammonium hydrogensulfate.34 ... 

Another route to sugar isothiocyanates involves thermal isomerization of the corresponding thiocyanates. Ferrier and Vethaviyasar20,21 and, later, Guthrie and Williams22-23 reported the allylic rearrangement of unsaturated thiocyanates to isothiocyanates see formulas 9-14. 

Sugar Isothiocyanates as Intermediates in the Synthesis of Nucleoside Analogs... 

Ogura and Takahashi18,19 detailed the reaction of the sugar isothiocyanates 2, 30, 31, and 32 with ammonia and amines, as well as with various classes of hydrazines. The reaction of sugar isothiocyanates with various classes of amines,44"62 hydrazines,63 72 and hydrazides has been reported by... 

In a series of publications and patents,63 64 66"79 Wieniawski and coworkers reported the results of investigations of the reaction of sugar isothiocyanates with amines and various substituted hydrazides of heterocyclic acids. The reaction of isothiocyanate 2 with 2,6-diaminopyridine 81 was described,63 and the formation of dithioureide 82 as the sole product was observed. The... 

Sugar isothiocyanates 75 are also converted with azides and Iriphenylphosphorous into sugar carbodiimides 76." ... 

CHEMISTRY AND DEVELOPMENTS OF jV-THIOCARBONYL CARBOHYDRATE DERIVATIVES SUGAR ISOTHIOCYANATES, THIOAMIDES, THIOUREAS, THIOCARBAMATES, AND THEIR CONJUGATES... 

The chemistry of sugar isothiocyanates and their reactions has been the subject of a specialized article in this series by Witczak4 in 1986 with 143 references dating up to 1984. The reader is also referred to the earlier work of Goodman5 on ureido sugars for a thorough historical perspective. It should... 

The UV spectra of acetylated sugar isothiocyanates show a low-intensity absorption at 250-254 nm, which allows UV detection in the course of chromatographic separations.5070,78 The band is frequently overlapped when stronger chromophores (such as benzoyl groups) are present in the mole-... 

Coupling of Sugar Isothiocyanates with Amine Nucleophiles... 

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