Stepwise demethylation of fluorescent 6,7-dimethoxy-3-trifluoromethylcarbostyrils 5 leads to 6-hydroxy derivatives 6 and 6,7-dihydroxyderivative 7. Phenolate formation shifts excitation and emission maxima from 370 and 430 nm to 430 and 480 nm for the anion of 6 and as far as 500 and 580 nm for the dianion of 7. Dependence of fluorescence quantum yield on media and polar structure, varying from 0.02 to 0.51, is discussed. O-Alkylation of 6 with alkyl bromoacetate yields esters of type 8 in good yield. Reactive succinimidoyl (OSu) esters of type 11 were prepared after saponification to acids 9. With amino acids or their esters, peptides and aminoglucose, linking to labeled derivatives 13 or 15 could be achieved under mild conditions in slightly basic aqueous media.
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