Sulfoxides biologically active, structure

Structure-variation showed that the benzothiophene ring system, which is oxidized to the sulfoxide/sulfone, is absolutely necessary for the activity. Substituents at position 3 (R ) of the benzothiophene diminish the biological activity, whereas aryl amides are very similar in activity compared to alkyl amides but have a slightly yellow colour. Alkyl esters show no enhanced activity compared to amides, but are less stable. 

Among the homodetic, polycyclic, biologically-active tryptophan peptides, the toxins of the Amanita phalloides represent a special case [see reference 427) and 349) for a review]. In fact, the poisonous components of this deathcap, the phallotoxins and amatoxins (Fig. 9), both contain a cycloheptapeptide structure with an additional intramolecular covalent bond connecting the p-sulfur atom of a L-cysteine residue with the carbon atom in position 2 of the indole ring of a L-tryptophan residue. In the amatoxins the thioether bridge is oxidized to the sulfoxide (Fig. 9). 

Additionally, a number of biologically significant molecules have in their structure a chiral nonracemic sulfinyl group. Among these molecules (Fig. 1), it is worth noting the new immunosuppressive thiaspirane sulfoxide Nuphar alkaloid type la and lb,13 the gastric antisecretory omeprazole 2,14 the new potassium channel activators of Rhone Poulenc aprikalim 3,15 the cyclic hexapeptide waiakeamide 4,16 the ACAT inhibitor 5,17 and the potent human immunodeficiency virus type 1 protease inhibitor 6.18... 

---