1H-indole-5,6-diol

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: TRP-2 catalyzes the tautomerization of DOPAchrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA). In the absence of TRP-2, DOPAchrome undergoes a spontaneous decarboxylation to form 5,6-dihydroxyindole (DHI).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To 0.81 g (0.004 mole) of N,O-bis(trimethylsilyl) acetamide is added, stirring at room temperature, 0.3 g (0.002 mole) of 5,6-dihydroxy indole. When dissolution is completed, 2 ml dichloromethane are added and the solution is passed through a column of silica 60, eluating with dichloromethane. The first fraction obtained is concentrated in a rotavapor, then vacuum-dried. Thus are obtained 0.42 g (yield: 71%) of white crytal of 5,6[di(trimethylsilyloxy]indole. When dissolution The first fraction obtained is concentrated in a rotavapor vacuum-dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To 0.81 g (0.004 mole) of N,O-bis(trimethylsilyl) acetamide is added, stirring at room temperature, 0.3 g (0.002 mole) of 5,6-dihydroxy indole. When dissolution is completed, 2 ml dichloromethane are added and the solution is passed through a column of silica 60, eluating with dichloromethane. The first fraction obtained is concentrated in a rotavapor, then vacuum-dried. Thus are obtained 0.42 g (yield: 71%) of white crytal of 5,6[di(trimethylsilyloxy]indole. When dissolution The first fraction obtained is concentrated in a rotavapor vacuum-dried

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: TRP-2 catalyzes the tautomerization of DOPAchrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA). In the absence of TRP-2, the DOPAchrome undergoes a spontaneous decarboxylation to form 5,6-dihydroxyindole (DHI).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The Bu'Lock et al article discloses oxidation often 2-3', 4'-dihydroxyphenylethyl amine derivatives, including dopa. For methyl dopa (described at page 2251), a 4.735×10-2M concentration of methyl dopa was reacted with a 0.1974M concentration of potassium ferricyanide, in the presence of sodium bicarbonate buffer at a 0.238M concentration. After 10 minutes 8 cc of a 20% zinc acetate solution was added to effect rearrangement of the dopachrome to the dihydroxymethylindole. The article indicates that a similar procedure was used for dopa. The reported 5,6-dihydroxyindole yield of one experiment, after purification, was 30%. However, the Bu'Lock article states that this yield could not be repeated. According to the article the solid light-brown residue obtained in subsequent experiments appeared to be polymeric. At page 2249 Bu'Lock et al hypothesized that their inability to repeat the sole successful experiment was attributable to the diluteness of the reaction medium. This later article by Bu'Lock et al supplements their prior article in Nature, 166:1036-7 (1950), which reported "an excellent yield" of 5,6-dihydroxyindole, and essentially negates their original findings. The reported 5,6-dihydroxyindole yield of one experiment, after purification However, the Bu'Lock article states that this yield could not obtained in subsequent experiments

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The Bu'Lock et al article discloses oxidation often 2-3', 4'-dihydroxyphenylethyl amine derivatives, including dopa. For methyl dopa (described at page 2251), a 4.735×10-2M concentration of methyl dopa was reacted with a 0.1974M concentration of potassium ferricyanide, in the presence of sodium bicarbonate buffer at a 0.238M concentration. After 10 minutes 8 cc of a 20% zinc acetate solution was added to effect rearrangement of the dopachrome to the dihydroxymethylindole. The article indicates that a similar procedure was used for dopa. The reported 5,6-dihydroxyindole yield of one experiment, after purification, was 30%. However, the Bu'Lock article states that this yield could not be repeated. According to the article the solid light-brown residue obtained in subsequent experiments appeared to be polymeric. At page 2249 Bu'Lock et al hypothesized that their inability to repeat the sole successful experiment was attributable to the diluteness of the reaction medium. This later article by Bu'Lock et al supplements their prior article in Nature, 166:1036-7 (1950), which reported "an excellent yield" of 5,6-dihydroxyindole, and essentially negates their original findings. The reported 5,6-dihydroxyindole yield of one experiment, after purification However, the Bu'Lock article states that this yield could not obtained in subsequent experiments

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: TRP-2 catalyzes the tautomerization of DOPAchrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA). In the absence of TRP-2, DOPAchrome undergoes spontaneous decarboxylation to form 5,6-dihydroxyindole (DHI).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: TRP-2 catalyzes the tautomerization of DOPAchrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA). In the absence of TRP-2, DOPAchrome undergoes a spontaneous decarboxylation to form 5,6-dihydroxyindole (DHI).

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: At the completion of the reaction, which will generally require from about 30 minutes to about 3 hours, preferably from about 45 minutes to about 2 hours, the reaction system may be acidified to a pH of about 5 or less, preferably about 4.5, by the addition of acetic acid. The reaction mixture is then extracted, preferably after filtration, with ether or dichloromethane one or more times, under a nitrogen gas atmosphere, to recover the product 5,6-dihydroxyindole. According to a particular feature of the invention, the isolated yield of 5,6-dihydroxyindole can be further increased by carrying out the isolation of the product 5,6-dihydroxyindole by adding to the acetic acid mixture a compound which will protect the hydroxy groups to give the product compound in a form which is more stable in air. For example, addition of acetic anhydride to the filtered mixture gives 5,6-diacetoxyindole on heating. It is also possible to form the borate ester ##STR8## by addition of boric acid to the acetic acid reaction mixture. Generally, any protecting group which is stable to acetic acid can be added to the filtered reaction mixture to give the protected 5,6-dihydroxyindole. on heating can be added to the filtered reaction mixture

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 11.4 g of benzyl 5,6-dihydroxy-2,3-dihydroindole-1-carboxylate, 60 ml of ethanol, 5.7 g of 10% palladium-on-charcoal, 5.7 ml of water and 23 ml of cyclohexene were mixed together, and the mixture was maintained at reflux for one hour. the mixture was maintained at reflux for one hour

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: TRP-2 catalyzes the tautomerization of DOPAchrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA). In the absence of TRP-2, the DOPAchrome undergoes a spontaneous decarboxylation to form 5,6-dihydroxyindole (DHI).

Conditions: temp:80.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: The reaction mixture is prepared in an autoclave by adding 0.04 mole (15 g) of 2-nitro-4,5-dibenzyloxyphenylacetonitrile, 1.5 g of palladium at a concentration of 10% on charcoal and 1.5 g of charcoal to 120 ml of ethanol containing 3 ml of water. These are heated to 80° C. for 2 hours, with stirring, under a hydrogen pressure of 4.105Pa. After cooling, the reaction mixture, which is treated in the same manner as previously, produces 5,6-dihydroxyindole in an equivalent yield. The reaction mixture is prepared in an autoclave After cooling the reaction mixture, which is treated in the same manner as previously,