Sugar thiocyanates method

The second- and oldest-method for the preparation of thionocarbamates on carbohydrate scaffolds consists of the condensation of thiocyanic acid, generated in situ from potassium thiocyanate and a protic acid, with an anomeric-free sugar to form the thermodynamically more stable five-membered ring OZT as the major compound (Scheme 2).27,28... 

Iron. Excess iron in wines causes cloudiness, interferes with the color, and can impair flavor. The mechanism of ferric phosphate precipitation has been intensively studied, and numerous colorimetric methods have been developed. For routine purposes the color developed with thiocyanate is adequate (6,9), but many enologists prefer the orthophenanthro-line procedures (3, 4, 6, 22). Meredith et al. (Ill) obtained essentially the same results for iron using 2,4,6-tripyridyl-s-triazine (TPTZ) to develop the color. Atomic absorption spectrophotometry can be used but, as with copper, corrections for reducing sugar and ethanol are necessary (51). 

Related methods may be used to introduce amino functions. For example, thiocyanate 237, made from the 4,6-dimesylate, rearranges to the isothiocyanate 238,225 and 3,4-unsaturated 2-cyanates, easily made in situ from the corresponding carbamates, afford the A-bonded 4-isocyanates of the 2-enes.229 From both types of rearranged products aminodeoxy sugars may be accessed, and in this way perosamine peracetate (239) can be synthesized from the cyanate of a 3,4-unsaturated 2-ol, which is thermally rearranged prior to dihydroxylation and acetylation.229... 

Allylic rearrangement of thiocyanates to isothiocyanates has been demonstrated for monosaccharide derivatives, " - " opening up methods for sugar transformations but especially for s mthesizing amino-sugars. " For example, (165) gives (166) by way of the isothiocyanate resulting from thermal isomerization. " The allylic O-methanesulphonyl substituent in... 

This reagent reacts more rapidly with primary than with secondary alcohols. This property has been made use of to transform the primary hydroxy groups of sugars to salts, which then may be converted to halides (Cl, Br, I), azides, amines, thiols, thiocyanates, etc. by reaction with appropriate nucleophiles (eq 10). Arylalkyl ethers and thioethers may also be prepared by appropriate modification of this method. These reactions generally proceed with high stereoselectivity. Thus reaction of chiral 2-octanol with this reagent afforded 2-chlorooctane with complete inversion... 

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