Indoxyl sulfate esters

Indfcan (Metabolic Indican). iH-lndol-3-ol hydrogen sulfate ester indot-3-yl Sulfate 3-indoxylsulfuric acid. C.H,NO,S mol wt 2]3,23. C 45.06%, H 3.31%, N 6.57%, O 30.01%, S 15.04%. Unstable as the free acid. Occurs in urine of mammals, also in blood plasma. Prepn of potassium salt from potassium indoxyl and potassium bisul fate Baeyer, Ber. 14, 1745 (1881) from chlorosulfonic acid and N-acetylindoxyl in pyridine Schwenk, Jolles, Biochem. Z. 69, 467 (1915) by persulfate oxidation of indole Boy-land el aL, Biochem. J. 62, 546 (1956). 

By 1909 the chemical nature of the royal purple pigment dibromoindogotin (see scheme) had been established and by 1897 synthetic indigo production had already begun. Ancient indigo dyeing utilized the precursors, sulfate esters of indoxyl or of substituted indoxyl, metabolites of tryptophan (see Fig. 

The sulfate group can be transferred easily, i.e. in exergonic reactions, to phenols and alcohols. These sulfuric esters have long been known as detoxication and excretion forms of various foreign substances and metabolic products. They include phenol sulfuric acid, indoxyl sulfuric acid (indican), and estrone sulfuric acid. The sulfuric esters of carbohydrates arise presumably in a similar manner (Chapt. XVII-7). 

---