Thioglycosides and Thiosugars

Black mustard (Brassica nigra Koch) contains a glucoside, sinigrin, which is hydrolyzed by enzymes present in the plant to allyl isothiocyanate, 

Almond emulsin does not hydrolyze the glucoside, but mustard-seed emulsin contains an enzyme, myrosin, which catalyzes the hydrolysis. It seems probable that the linkage is beta and indeed enzymic hydrolysis produces jS-glucose. However, silver nitrate and silver carbonate produce a-glucose, presumably as a result of a Walden inversion (70), The hydrolytic action of sodium hydroxide leads to thioses (1-thiosugars). 

Many of the plants of Cruciferae produce sinigrin and other sulfur-containing glycosides. These compounds comprise the so-called mustard-oil glycosides and are described in more detail elsewhere (8,69). 

Synthetic thioglucosides are prepared by the action of thiophenol on acetylglycosyl bromides in the presence of sodium hydroxide (71,72). They are extremely resistant to acid hydrolysis, and this resistance probably explains the lack of hydrolysis by almond emulsin (71,73). By treatment of sugar thiols with mercuric chloride, thioglycosides also may be synthesized (Chapter V)  

Many aromatic l-thio-j -D-glucosides have been tested as antimalarials. Some show a slight positive action, but the effect is too small to be of value (74). 

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