Isothiocyanates reaction with amino sugars

Another main subject of research of Garcia Gonzalez, with the collaboration of J. Femandez-Bolanos, was the reaction of amino sugars with isothiocyanic acid derivatives. 2-Amino-2-deoxy-D-glucose hydrochloride and potassium thiocyanate were shown to give rise to 4-(D-arabino-tetritol-l-... 

In carbohydrate chemistry, the most described method for the preparation of saccharidic thionocarbamates involves preliminary introduction of the amine function on a partially or non-protected saccharidic template. The condensation of amino sugars with carbon disulfide or thiophosgene leads to cyclization in 1,3-oxazolidine- or l,3-oxazine-2-thiones. This reaction involves the formation of an intermediate isothiocyanate, which reacts further with a 3- or y-located hydroxyl group. The viability and facility of this process depends on the saccharidic ring size and the inherent strain. Some major rules can be put into light from the cases studied 30... 

Derivatization with phenyl isothiocyanate (97, R = Ph) followed by HPLC was compared with IEC followed by the ninhydrin reaction for over ninety compounds. The former method was favored for speed, sensitivity and equipment versatility257. Phenylth-iocarbamyl derivatives of amino sugars and amino sugar alcohols (reaction 10) were... 

Glycosyl isothiocyanates have also been allowed to react with unprotected 2-amino-2-deoxyaldoses and 1-amino-1-deoxy-2-ketoses.68 This reaction leads to the formation of heterocyclic derivatives resulting from cy-clization involving the carbonyl group of the amino sugar moiety following the mechanistic pathway already discussed for similar condensation reactions with alkyl and aryl isothiocaynates. 

Deoxy-2-thioureido-sugars, e.g. 53 (R=Bz or CO2EO could be synthesized by direct condensation of amino-sugars with benzoyl or ethoxycarbonyl isothiocyanate, whereas similar reactions with aryl or alkyl isothiocyanates led to alditol-1-yl substituted heterocycles, e.g. 54 by way of 53 (R=Ph or Me). These monocyclic products further cyclize in dilute acetic acid to give 55... 

Thioamides can serve as surrogates for isothiocyanates in the Marckwald synthesis. For example, reaction of a-amino acetals 1278 with thioamides 1277 in the presence of HgClz affords amidine intermediates, which cyclize to form imidazoles under acidic conditions. This method has been applied to synthesize a variety of sugar imidazoles (Scheme 324) <2005HCA10, 2004HCA3035, 2004HCA719, 2000TA435>. 

The reaction of carbohy drate derivatives bearing amino groups with fluorescein isothiocyanate has been widely used to introduce a fluorescent dye into a sugar molecule. Several strategies have been proposed for the... 

The reaction of sugar isothiocyanates with aminosugars described above has also been studied with 1-amino (alkyl and arylamino)-l-deoxy-D-fructose 143 (Scheme 32). Thus, treatment of different 0-acylated sugar isoth-iocyanates with D-fructosamines 143 gave M-glycosyl-5-hydroxy-5-tetritolyl-imidazolidine-2-thiones 144 as pairs of diastereomers in almost quantitative yield [ 152]. The reaction times were shorter (15-20 min) for fructosamine or its M-methyl derivatives than in the cases of N-aryl derivatives (8-24 h). Acid-catalyzed dehydration of 144 with ethanolic TFA at rt led to 147 in 65-77% yield. These compounds can be considered simultaneously as M-nucleosides and acyclic C-nucleosides of imidazoline-2-thiones. 

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