1.3- Diselenides special

The diaryl diselenides are solids of well-defined crystalline form, the benzyl compounds being slowly decomposed by light. The following methods have been used for their preparation, but some are only applicable to special cases ... 

Amino acid 78 and its y-glutamyl derivative are other components of the major pool of seleno compounds in accumulator plants, while selenomethionine (79) is the major compound in microorganisms like yeast, which is not specialized in selenium utilization. Se-Methylselenocysteine 5e-oxide (80), which is found in marine algae, tends to spontaneously decompose with the formation of pyruvate and ammonia via aminoacrylic acid and methaneselenic acid (81). The latter reacts with sulfhydryls or selenols to selenodisulfldes and diselenides. 

Preparation from Disulphides, Diselenides, and Ditellurides.—The use of disulphides as sulphenylating agents towards alkenes and carbanions continue to offer a distinctive alternative to the use of sulphenyl halides for the same purpose. Although reaction conditions are more severe, cleaner results are usually obtained. The special case of the conversion of disulphides into corresponding sulphides is covered in the later section on Reactions of Disulphides. 

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