Claims
- 1. A process for preparing 5,6-dihydroxy-2-amino-1,2,3,4-tetrahydronaphthalene of the formula (I): ##STR7## or an acid addition salt thereof, wherein: R.sub.1, R.sub.2 and R.sub.3, which are each the same or different, are hydrogen or lower alkyl;
- which process comprises:
- a) condensing 2,3-dialkoxybenzaldehyde with pyruvic acid in an aqueous/alcoholic system in the presence of an inorganic base, to obtain 2-keto-4-(2,3-dialkoxyphenyl)butenoic acid;
- b) transforming the ketone at the 2-position into an amino or alkylamino group with simultaneous reduction of the double bond, to give, respectively, 2-amino or 2-alkylamino-4-(2,3-dialkoxyphenyl)butyric acid;
- c) transforming 2-amino- or 2-alkylamino-4-(2,3-dialkoxyphenyl)butyric acid into 4-[2-(2,3-dialkoxyphenyl)ethyl]-N-alkyl-2,5-oxazolidindione;
- d) intramolecularly cyclizing N-carboxyanhydride to give 5,6-dialkoxy-2-amino or 2-alkylamino-1-tetralone;
- e) reducing the ketone to give salified 5,6-dialkoxy-2-amino or 2-alkylamino-1,2,3,4-tetrahydronaphthalene and, optionally;
- f) effecting O-dealkylation to give salified, 5,6-dihydroxy-2-amino or 2-alkylamino-1,2,3,4-tetrahydronaphthalene, and, optionally; and
- g) transforming the resulting salt into the free base, or into another acid addition salt.
- 2. The process of claim 1, wherein in step a) a water/ethanol system is used and the inorganic base is potassium hydroxide.
- 3. The process of claim 1, wherein in step c), 4-(2,3-dialkoxyphenyl)-2-alkylamino butyric acid is first reacted with a chloroformate, to give the corresponding 2-N-alkyl-N-alkoxy-carbonylamino compound, which is subsequently cyclized to the corresponding cyclic N-carboxy anhydride.
- 4. The process of claim 1, wherein R.sub.1 is methyl.
Priority Claims (1)
Number |
Date |
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MI94A0802 |
Apr 1994 |
ITX |
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Parent Case Info
This application is a Division of application Ser. No. 08/962,706 filed on Nov. 3, 1997, now U.S. Pat. No. 5,936,125, which is a divisional application of application Ser. No. 08/722,227, which was filed as international application PCT/EP95/01406, filed Apr. 13, 1995, now U.S. Pat. No. 5,710,336.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
5221770 |
Bertolini et al. |
Jun 1993 |
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Divisions (2)
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Number |
Date |
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Parent |
962706 |
Nov 1997 |
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Parent |
722227 |
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