* All experimental methods are cited from the reference, please refer to the original source for details. We do not guarantee the accuracy of the content in the reference.
With potassium permanganate; In water; at 75.0℃; for 2.33333h;
General procedure: The powdered potassium permanganate (3.3g, 20.90mmol) Dissolved in water (50mL), It was then dropped into an aqueous solution of methylpyrazine within 20 minutes. The reaction was stirred at 75 C for 2 hours. TLC monitoring until the end of the reaction. Cool, filter, wash with 50 mL of water, adjust the filtrate to pH 1.5 with nitric acid, slowly raise the temperature to 50 C for 10 minutes, then cool, extract with 3 × 20 mL of ethyl acetate, remove water with anhydrous sodium sulfate, and distill under reduced pressure And dry. The product is untreated and ready for use. Other methylpyrazines include 2,3-dimethylpyrazine, 2,6-dimethylpyrazine, 2,3,5-trimethylpyrazine and 2,3,5,6-tetramethylpyrazine The azine is carried out as 2,6-dimethylpyrazine.
4
5.6-dimethyl-pyrazine-dicarboxylic acid-(2.3)[ No CAS ]
With sodium hydroxide; In methanol; for 2.0h;Heating / reflux;
5,6-dimethyl-pyrazine-2-carboxylic acid: To a solution of 2,3-diaminopropionic acid (1.0 g, 9.6 mmol) in methanol (20 mL) was added butane-2,3-dione (728 muL; 11.5 mmol) and NaOH (1.4 g; 56.6 mmol). The mixture was refluxed for 2 h and then cooled to room temperature while air was bubbled through for 1 hour. The white precipitate was filtered and the gelatinous product was concentrated under vacuum. The crude product was taken up in dichloromethane, washed with 10% citric acid, dried over MgSO4 and filtered. The solvent was removed under reduced pressure to give 5,6-dimethyl-pyrazine-2-carboxylic acid as a volatile solid. The compound was used as is in the next step.
With potassium carbonate; In ethanol; dichloromethane; pyrographite;
Concentrated sulphuric acid (43.6 g.) is added to a suspension of <strong>[13515-06-5]5,6-dimethylpyrazine-2-carboxylic acid</strong> (99.4 g.) in ethanol (600 cc.) and the mixture is heated under reflux for 13 hours. A solution is obtained which, after cooling, is poured onto ground ice (360 g.). Methylene chloride (400 cc.), followed by potassium carbonate (300 g.), are then added. The aqueous phase is then separated off by decantation, after which it is extracted with methylene chloride (2 * 100 cc.). The organic phases are combined, dried over sodium sulphate and evaporated to dryness under reduced pressure. The residue obtained is taken up in methylene chloride (300 cc.) and the insoluble product is filtered off. The filtrate is again dried over sodium sulphate in the presence of decolorising charcoal, filtered and then evaporated to dryness under reduced pressure. This gives ethyl 5,6-dimethylpyrazine-2-carboxylate (95 g.) in the form of an orange oil. 5,6-Dimethylpyrazine-2-carboxylic acid can be prepared in the following manner:
((3S,4R,6aR,6bS,8aS,14bR)-8a-((4-chlorobutoxy)carbonyl)-3-hydroxy-4,6a,6b,11,11,14b-hexamethyl-1,2,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,14,14a,14b-icosahydropicen-4-yl)methyl 5,6-dimethylpyrazine-2-carboxylate[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
36%
With dmap; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; In dichloromethane; at 20.0℃; for 12.3333h;
5,6-dimethylpyrazine acid (about 0.27 mmol, prepared as Example 2), EDCI (0.35mmol) and DMAP (0.027mmol) were dissolved in dry methylene chloride (20mL), the chlorinated hederagenin(152 mg, 0.27 mmol, prepared as Example 4) was then dissolved in dichloromethane (20 ml). It was dropped into 5,6-dimethylpyrazine acid solution within 20 minutes, and stirred at room temperature for 12 hours. It was then diluted with dichloromethane (20 mL), washed with saturated aqueous NaCl solution, dried over anhydrous sodium sulfate, concentrated and purified by column chromatography to obtain a white powder, H-23. Yield: 36% (afterchromatograph with DCM / MeOH, 1% -2%) as a white powder, m.p .: 123.6 C.
4-(((4aS,6aS,6bR,9R,10S,12aR)-10-hydroxy-9-(hydroxymethyl)-2,2,6a,6b,9,12a-hexamethyl-1,2,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,12b,13,14b-icosahydropicene-4a-carbonyl)oxy)butyl 5,6-dimethylpyrazine-2-carboxylate[ No CAS ]
With dmap; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; In dichloromethane; at 20.0℃; for 12.0h;
5,6-dimethylpyrazine acid (248 mg, about 2 mmol, prepared as Example 2), 4-chloro-1-butanol (2.4mmol), EDCI (2.4mmol) and DMAP (0.2mmol) were added to dry methylene chloride (20mL), stir at room temperature for 12 hours, then dilute with dichloromethane (20mL), The saturated aqueous NaCl solution was washed, dried over anhydrous sodium sulfate, and purified by column chromatography to obtain an oily liquid. The hederagenin(236mg, 0.5mmol), K2CO3 (207mg, 1.5mmol) and oily liquid were added to DMF (20mL), The mixture was stirred at 85 C for 4 hours. It was then diluted with ethyl acetate (20 mL), washed with saturated aqueous NaCl solution, dried over anhydrous sodium sulfate, concentrated and purified by column chromatography to obtain a white powder, H-17. Yield: 27% (after chromatograph with DCM / MeOH, 1% -2%) as a white powder, m.p .: 134.7 C.
2-hydroxyethyl (4aS,6aS,6bR,9R,10S,12aR)-10-hydroxy-9-(hydroxymethyl)-2,2,6a,6b,9,12a-hexamethyl-1,3,4,5,6,6a,6b,7,8,8a,9,10,11,12,12a,12b,13,14b-octadecahydropicene-4a(2H)-carboxylate[ No CAS ]
2-(((4aS,6aS,6bR,9R,10S,12aR)-10-hydroxy-9-(hydroxymethyl)-2,2,6a,6b,9,12a-hexamethyl-1,2,3,4,4a,5,6,6a,6b,7,8,8a,9,10,11,12,12a,12b,13,14b-icosahydropicene-4a-carbonyl)oxy)ethyl 5,6-dimethylpyrazine-2-carboxylate[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
25%
With dmap; 1-ethyl-(3-(3-dimethylamino)propyl)-carbodiimide hydrochloride; In dichloromethane; at 20.0℃; for 12.3333h;
5,6-Dimethylpyrazine acid (0.27 mmol, prepared as Example 2), EDCI (0.35mmol) And DMAP (0.027 mmol) were dissolved in dry methylene chloride (20 mL). The compound hederagenin alcohol (140 mg, 0.27 mmol, prepared as Example 3) was dissolved in dichloromethane (20 mL). This solution was dropped into 5,6-methylpyrazine acid solution within 20 minutes, and stirred at room temperature for 12 hours. The reaction mixture was then diluted with dichloromethane (20 mL), washed with saturated aqueous NaCl solution, dried over anhydrous sodium sulfate, and purified by column chromatography to obtain a white powder, H-11. Yield: 25% (after chromatograph with DCM / MeOH, 1% -2%) as a white powder, m.p .: 146.2 C.
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