Preparing methods and uses of S-(-)-nadifloxacin and water soluble salt thereof
A technology of nafloxacin and water-soluble salt, which is applied in the field of preparation of S--nafloxacin water-soluble salt, can solve the problem of poor effect of racemate nafloxacin, and achieve low gastrointestinal side effects , stable yield, and reduced toxic and side effects
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[0033] Example 1: Preparation of (±)-5,6-difluoro-2-methyl-1,2,3,4-tetrahydroquinoline
[0034] The first step:: Preparation of 8-bromo-5,6-difluoro-2-methylquinoline
[0035]
[0036] Add 3,4-difluoro-6-bromobenzeneacetamide (160g, 0.64mol) and sodium m-nitrobenzene sulfonate (144g, 0.64mol) into a three-necked flask equipped with a stirring, condenser and dropping funnel. , Iron sulfate heptahydrate (18g, 0.03mol), boric acid (174g, 2.81mol), water (560ml) and concentrated hydrochloric acid (560ml), heated to reflux for 0.5 hours under stirring conditions, slowly add crotonaldehyde at the same temperature (79ml, 0.97mol), after about 1 hour dripping is completed, then reflux for 1 hour, while hot suction filtration, the filtrate is cooled to room temperature, add methanol (2300ml), and then use 25% sodium hydroxide solution under ice-water cooling Adjust the pH value to about 10 to completely precipitate crystals, filter with suction, and wash twice with 50% methanol solution ...
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[0040] Example 2: Preparation of S-(-)-5,6-difluoro-2-methyl-1,2,3,4-tetrahydroquinoline (Method 1)
[0041]
[0042] Add 98g (0.27mol) of L-2,3-dibenzoyltartaric acid to 200mL of ethyl acetate and stir to dissolve at room temperature. Add (±)-5,6-difluoro-2-methyl-1,2, 100g (0.55mol) of 3,4-tetrahydroquinoline, after dripping, stir at room temperature for 1hr, filter and collect the precipitated solid, wash with ethyl acetate, recrystallize with 70% ethanol, add 500mL water and 500mL ethyl acetate to the obtained solid In the solution, adjust pH=9-10 with 20% NaOH solution under stirring, divide the organic layer, wash with saturated NaCl solution, and dry with anhydrous sodium sulfate. After filtration, the filtrate was concentrated to dryness under reduced pressure to obtain 38 g of light yellow oil. Yield: 38%, m.p.: 29-30°C, [a] D 20 = -36.4 (C = 0.5, methanol), M+1: 184.09. Elemental analysis, calculated value (%): C, 65.56; H, 6.05; N, 7.65. Found: C, 65.67; H, 6.08; N, ...
Example Embodiment
[0043] Example 3: Preparation of S-(-)-5,6-difluoro-2-methyl-1,2,3,4-tetrahydroquinoline (Method 2)
[0044] Add 98g (0.27mol) of L-2,3-dibenzoyltartaric acid to 200mL of acetone and stir to dissolve at room temperature. Add (±)-5,6-difluoro-2-methyl-1,2,3 dropwise with stirring, 100g (0.55mol) of 4-tetrahydroquinoline, after dripping, stir at room temperature for 1hr, filter and collect the precipitated solid, wash with ethyl acetate, recrystallize with 70% ethanol, add the obtained solid to a mixed solution of 500mL water and 500mL ethyl acetate Under stirring, adjust pH=9-10 with 20% NaOH solution, divide the organic layer, wash with saturated NaCl solution, and dry with anhydrous sodium sulfate. After filtration, the filtrate was concentrated to dryness under reduced pressure to obtain 37.5 g of light yellow oil. Yield: 37.5%, m.p.: 29-30°C, [a] D 20 = -36.6 (C = 0.5, methanol), M+1: 184.09. Elemental analysis, calculated value (%): C, 65.56; H, 6.05; N, 7.65. Found: C, 65.65...
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