Isothiocyanates imidazolidine-2-thiones

The stereoselective formation of imidazolidine thiones via the rearrangement of chiral thiocyanates has recently been reported. Heating allylic thiocyanates such as 255 at 80 °C produced El-mixtures of diastereomeric isothiocyanates 256a in 92%... 

Treatment of imidazolidine-2-thione (729) with isothiocyanate (730) afforded (731) in high yield (75S675). 

Even though the most widely used preparation is still the reaction of alkali isothiocyanates or alkyl and aryl isothiocyanates with a-amino carboxylic acid derivatives, the reaction of dithiocarbamic acid esters (CCX) with a-amino carboxylic acids (CCXI) has certain advantages especially in the synthesis of heterocyclically substituted imidazolidin-4-one-2-thiones (221). 

The same group prepared N-(/S-D-glucopyranosyl)oxazolidine-2,4-diones [146] and N-(/l-D-glucopyranosyl)imidazolidine-2,4-diones [147] by desulfurization-condensation of glucosyl isothiocyanate with a-hydroxyacids and J -substituted a-aminoacids, respectively, in the presence of silver triflu-oroacetate and triethylamine. 4-Glucosyl-l,2,4-oxadiazolidine-5-thiones were also prepared by reaction of protected glucosyl isothiocyanates with an ox-aziridine ring [148]. 

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. 

A soln. of ca. 20% excess 1-naphthyl isothiocyanate in pyridine containing collidine added to an aq. soln. of 2-amino-2-deoxy-D-glucose hydrochloride, and the product isolated after a few min. at room temp. -> 5-hydroxy-1-naphthyl-4-(D-araZ>mo-tetrahydroxybutyl)imidazolidine-2-thione. Y 77%. F. e., also bicyclic products, s. J. E. Scott, Carbohydrate Res. 14, 389 (1970). 

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