INDOLINE DERIVATIVES

1322639 Derivatives of 5,6-dihydroxyindoline- 2-carboxylic acid F HOFFMANN-LA ROCHE & CO AG 29 Oct 1971 [30 Oct 1970] 50334/71 Headings C2B and C2C The invention comprises compounds of Formula I and their salts, wherein R 1 is benzoyl, phenylalkanoyl or phenylsulphonyl (any of which may be alkyl-, alkoxy- or halo-substituted), alkenoyl, alkynoyl, alkoxyalkanoyl, alkoxycarbonyl, phenylalkoxycarbonyl, carbamyl, alkylcarbamyl, phenylthio or nitrophenylthio, R 2 is OH, alkoxy or amino (possibly alkyl-substituted); R 3 , R 4 are each H or alkyl, or R 3 -R 4 is alkylene; and R 5 , R 6 are each H, halogen, alkyl or alkoxy, the aliphatic groups of R 1 -R 6 containing up to 18 carbon atoms. These compounds are prepared by hydrolysing the corresponding boric acid derivatives, esterifying or amidating the carboxylic acids, hydrolysing or amidating the esters, hydrolysing the 5,6-diacyloxy compounds, or by N-acylation. Solutions of the boric acid derivatives are formed by reacting a compound of the above formula wherein R 1 is H (Ia) with boric acid (or salts of either reagent may be used) at pH at least 7, and reacting the product with an agent introducing an N-acyl group. Compound I where R 1 is benzyloxycarbonyl, t-alkoxycarbonyl or phenylthio may be converted to compounds Ia by acid hydrolysis or by other methods described in the Specification. Therapeutic compositions having hypotensive and antipyretic activity and for treating diseases due to dopamine deficiency, e.g. Parkinson's disease, comprise compounds of Formula I, and may be administered orally, parenterally or rectally.