Syntheses and structural characterization of water‐soluble selenium reagents for the redox control of protein disulfide bonds

A new class of water‐soluble redox reagents ( 1–4 ) that contain selenium as the active site was developed for the purpose of the redox control of protein structures. The X‐ray crystallographic analyses revealed that trans‐3,4‐dihydroxy‐1‐selenolane (DHS red ) ( 1 ) and its Se‐oxide (DHS ox ) ( 2 ) have two axial hydroxy groups on the selenolane five‐membered ring, whereas trans‐1,2‐diselenane‐4,5‐diol (DST ox ) ( 3 ), a selenium analog of oxidized dithiothreitol (DTT ox ), has two equatorial hydroxy groups on the diselenane six‐membered ring. According to the vicinal 3 J HH coupling constants observed for 1–3 , it was suggested that they adopt similar structures in solution to those in the solid state. Diselenothreitol (DST red ) ( 4 ), a selenium analog of dithiothreitol (DTT red ), was also synthesized, but it was too air sensitive to be isolated. The reactions of 1–4 with DTT ox and DTT red indicated that the oxidizing power of DHS ox ( 2 ) exceeds by far that of DTT ox , while the reducing power of DST red ( 4 ) exceeds that of DTT red .