2, 3-dihydroxyindoline

H-NMR and C-NMR spectroscopy (84TL6063) showed that 1-acetyl-2,3-dihydroxyindolines in CDCI3 solution exhibit the ring-chain equilib-... 

After studies of the structure and stereochemistry of betanidine and isobetanidine (ref. 36) the former was synthesised (ref.37). The indole component, the methyl ester of L-cyclodopa, 5,6-dihydroxyindoline-2-carboxylic acid, has been prepared (ref. 38) and the piperidine moiety, betalamic acid (ref.39) has been synthesised by another distinct route. 

Several studies have reported the chemical shifts of the ring protons in 5,6-dihydroxyindoline derivatives and these are tabulated in Table 5. 

Table 4. Ultraviolet spectral data for 5,6-dihydroxyindoline derivatives...

The most important preparative route to the aminochromes 137 is oxidation of primary or secondary catecholamines 134 (Scheme 28). Initial oxidation gives the o-quinones 135 that cyclize to the indoline 136 and further oxidation gives the aminochrome 137. The 5,6-dihydroxyindolines 136 are not usually isolated, but for some studies mild oxidation of the previously isolated indoline (Section III) is a convenient preparative route (84TL2993). 

Table 6.2 some 5,6-dihydroxyindoline derivatives that have been prepared... 

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