DK175312B1 - Optically active ofloxacin derivs. - with increased antimicrobial activity and reduced toxicity - Google Patents

Abstract

derivs. of formula (VI) are new: X1 = halo; R1 = 1-4C alkyl; R3 = 1-3C alkyl. Also claimed are H-substd. benzoxazine derivs. of formula (X): each of X1 and X2 = halo, Q = H or a gp. of formula (a): R2 = substd. sulphonyl, alkoxycarbonyl or aralkyloxycarbonyl; Specifically claimed S(-)-9-fluoro-3-methyl-10-(4-methyl-1-piperazinyl)-7- oxo-2,3-dyhydro-7H -pyrido(1,2,3-de)(1,4) benzoazine-6-carboxylic acid (Ia) and the corresp. 10-(4-1-piperazinyl) cpd.

Description

----------- 1 DK 175312 B1 i

The invention relates to optically active benzoxazine derivatives and a process for their preparation which is useful for the preparation of optically active compounds of ofloxacin and its analogs.

Ofloxacin ((±) -9-fluoro-3-methyl-10- (4-methyl-1-piperazinyl) -7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de] [ 1-4] -benzoxazine-6-carboxylic acid) is known to be an excellent synthetic antimicrobial agent as described in Japanese Patent Application (OPI) No. 46986/82 (the term "OPI" is used herein to mean "unexamined" published patent application ").

Ofloxacin has an asymmetric carbon atom at the 3-position and is obtained as a racemate (specific rotation [α] D »0 °) by known methods. According to the present invention, optically active compounds of the racemic compound ofloxacin have been obtained and found that the 3S-methyl compound has an antimicrobial effect that is approx. two times greater than the effect of the (±) compound and an acute toxicity (LDS0) 20 weaker than the (±) compound, determined in mice by intravenous administration. On the other hand, according to the present invention, it has been found that the 3R-methyl-yl compound has an antimicrobial effect of approx.

1/10 to 1/100 times the effect of the (±) compound, while having an acute toxicity substantially equal to the toxicity of the (±) compound. That is, the 3-methyl form of ofloxacin has been found to have very desirable properties, i.e. a greater antimicrobial effect and reduced toxicity, and it is expected to be a very useful pharmaceutical in comparison to the (±) compound. Furthermore, the 3S-methyl compounds of ofloxacin in the free form have a remarkably high water solubility in comparison with the (t) compound, and they can be used as injectable preparations.

As a result of studies for that purpose

I DK 175312 B1 I

I i

In particular, to produce the 3S methyl form having the strong I

Most effective among the two ofloxacin isomers is now I

It has been found that compounds of formula I below

I (I) are useful as intermediates for the preparation of I

In the 5S-alkyl isomer ofloxacin and other isomers of pyrido-I

In benzoxazine derivatives with excellent antimicrobial I

In effect: I

I 'ΥΊ I

i ° (I) I

I I

I .i I

I 15 i

In which Xj ^ and X2, which may be the same or different, I

In each denotes a halogen atom, such as a fluorine or I

In the chlorine atom, with both X 1 and X 2 being preferably fluoro-S

For 20 more, an alkyl group having from 1 to 4 represents carbon I

In atoms such as a methyl, ethyl or propyl group, I

I, etc., preferably a methyl group, Q represents a hydro-I

In the genome, a -CH = C {COOEt) 2 group or a group of I

In the general formula:

I 25 I

I R2 I

I O I I

I 1- (CH,) I

30 I

wherein R 2 represents a substituted sulfonyl group, an I

In an alkoxycarbonyl group or an aralkyloxycarbonyl group

In pe, such as a p-toluenesulfonyl group, a benzenesulfonyl group

In group, a methanesulfonyl group, a t-butoxycarbonyl-I

group, a benzyloxycarbonyl group, a p-methoxybenzyl-I

Oxycarbonyl group, etc., preferably a substituted sulfonyl group, preferably a p-toluenesulfonyl group, and n represents an integer from 1 to 3, preferably 1 or 2.

It is an object of the invention to provide a novel intermediate of the above Formula I which is useful in the preparation of optically active ofloxacin and other pyridobenzoxazine derivatives.

The novel intermediates of the invention of formula (I) can be prepared by the method illustrated below.

15 20 25 1 35

I DK 175312 B1 I

I I

') PL +' "γι \ I

I 1 I 11 (CH.) I

° 'v ^ R 2 n i

I R1 I

I (II) (III) I

I 10 I

I 1ΥΊ ° i '2 I

I c> A 1- (ch ~) I 15 2 n I) Separation in I (v) in I optical isomers ^

I X1 o R2 2) Hydrolysis I

- * ^ p ,, · -

I (ΙΑ) I

I 25 I

I COOC2H5 I

"Y \ XXXI

I * · x2 \ i I

2 T i

^ * 1 Rl I

(IB) (IC) I

2

I 35 I

In the formulas, n, X 2, X 2, R 2, R 2 and R 3 are as defined above and X 3 is a carboxyl group or a reactive derivative thereof, e.g. an active ester, halide or acid anhydride of the carboxylic acid.

In the above process, the 3-alkyl-7,8-dihalo-2,3-dihydro-4H- [1,4] -benzoxane derivative (II) is condensed with a cyclic amino acid or a reactive derivative thereof (III) by amide bond formation to give compound (IV). The condensation reaction may be carried out by either the active ester method, the acid anhydride method or the DCC method, but generally the compound (II) and the acid chloride (III) wherein X3 is -COC1 are reacted in an organic solvent such as a halogenated hydrocarbon, f. eg. dichloromethane, in the presence of an acid acceptor, such as pyridine, triethylamine or potassium carbonate, at room temperature with stirring. The reaction product can be isolated and purified in the usual manner, such as crystallization, column chromatography, etc.

In this condensation reaction, separation of the diastereomeric mixture of compound (IV) can be readily accomplished when either one or the other of the two isomers of the cyclic amino acid or the reactive derivative thereof (III), i. an S compound or an R-25 compound is used. More specifically, derivatives (III) such as S- or R-proline, S- or R-pipecolic acid (piperidine-2-carboxylic acid), etc. are suitably used.

The most preferred compounds (III) include (S) -N-benzenesulfonylproline and (S) -N-p-toluenesulfonylproline.

The diastereomeric mixture of compound (IV) can be separated by fractional crystallization, chromatography using silica gel, etc. as a carrier, or a combination thereof, and 3S-alkyl-4-substituted-1,4-benzoxazine derivatives (IA) are obtained.

The diastereomer (IA) thus separated is lysed, usually under basic conditions, to I DK 175312 B1

I 6 I

To form a 3S-alkyl-7,8-dihalo-2,3-dihydro-4H-1

[1,4] benzoxazine (IB). IN

When the compound of formula (IB) is heated with I

In diethylethoxymethylene malonate, preferably at 130 L

At 5 140 * 0, the compound (IC) can be prepared. IN

In this connection, a 3S-9- I can be converted

In fluoro2,3-dihydro-3-methyl-10- (4-methyl-1-piperazinyl) - I

In 7-oxo7H-pyrido [1,2,3-d] [1,4] benzoxazine-6-carboxylic acid I

I as described in EP-206283-A. IN

The present invention is also illustrated

You guys using the following examples. IN

In Example 1 I

I 15 I

In Preparation of Diethyl [3S-7,8-Difluoro-3-methyl-2,3-di-I

hydro-4H- [1/4] benzoxazin-4-ylmethylene malonate

I - COOC-Hc I

In 20 V-

I I

I ° ^> CH3 ° ^ ch3

I 25 I

To 1.13 g of 3S-7,8-difluoro-2,3-dihydro-3-methyl-I

In 4H- [1,4] benzoxazine 1.58 g of diethylethoxymethylene-1

In 30 malonate and the mixture was stirred at 130 to 140 ° C in 1

For 70 minutes. The reaction mixture was exposed as such

I for column chromatography using 50 g of silica

In cachel and eluted with chloroform to give 2.47 g of I

In diethyl [3S-7,8-difluoro-3-methyl-2,3-dihydro-4H- [1,4] -1

In benzoxazin-4-yl] methylene malonate. IN

In [a] D = + 250.4ec (C = 4.275, CHCl3). IN

In NMR (CDCl 3) δ (ppm): I

7 DK 175312 B1 1.22 - 1.42 (9H, m), 3.90 - 4.44 <7H, m), 6.74 -6, Θ8 (2H, m), 7.78 [1H, s ).

Reference Example 1 5

Preparation of 3S-9-fluoro-2,3-dihydro-3-methyl-10- (4-methyl-1-piperazinyl) -7-oxo-7H-pyrido [1,2,3-de] - [1, The product obtained in Example 1 was dissolved in 5 ml of acetic anhydride and 10 ml of a mixture of acetic anhydride and concentrated sulfuric acid (2/1 by volume) under stirring and ice-cooling, then stirred at 50 to 60 ° C for 40 minutes. To the reaction mixture was added ice and an aqueous solution of sodium hydrogen carbonate, and the reaction product was extracted three times with portions of 150 ml of chloroform. The combined extract was washed with water, dried over anhydrous sodium sulfate and concentrated under reduced pressure. As a solid began to precipitate, a small amount of diethyl ether was added and the precipitate was collected by filtration. The precipitate was washed with a small amount of diethyl ether to give 1.32 g of ethyl 3S9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido [1,2,3 de] [l, 4] benzoxazine-6-carboxylate.

In 12 ml of acetic acid, 1.20 g of the obtained compound was dissolved and 25 ml of concentrated hydrochloric acid was added to the solution and then refluxed at 120 to 130 ° C for 90 minutes. After leaving the reaction mixture at room temperature, colorless, needle-like crystals were collected which were collected by filtration and washed successively with a small amount of water, ethanol and diethyl ether to give 0.96 g of 3S-9,10-difluoro-3- methyl 7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de] -35 [1,4] benzoxazine-6-carboxylic acid.

In 30 ml of diethyl ether, 324 mg of it was suspended

I DK 175312 B1 I

I I

In obtained compound, and a large surplus of boredri- I

In fluoride ethyl etherate was added and then red

You stirred at room temperature for 30 minutes to form I

In a chelate compound. The product was collected by file I

For 5 hours and washed with a small amount of diethyl ether to r I

To obtain 373 mg of a powder of 3S-9, 10-difluoro-3-I

In methyl 7-oxo-2,3-dihydro-7H-pyrido- [1,2,3-de] [1,4] benzene-1

In oxazine-e-carboxylic acid BF 2 chelate having a melting point I

For over 300 ° C. The powder was dissolved in 7 ml of dimethyl sulfide

In 10 oxide, and 136 mg of N-methylpiperazine and 228 mg of triethyl-I

I amine was added and then stirred at room temperature

For 17 hours. The reaction mixture was concentrated

In the right to dryness under reduced pressure, and to the solid I

To the substance was added 15 ml of 95% methanol and 0.31 ml of triethylamine. IN

The resulting mixture was refluxed for three hours. React> ~ * I

The reaction mixture was concentrated under reduced I

In pressure, the residue was filtered and washed successively

I with a small amount of ethanol and diethyl ether to obtain I

You see of 350 mg of a white powder. Recrystallization of I

In a solvent mixture of ethanol and concentrated I

In aqueous ammonia, 230 mg of the title compound gave I

In {3S-ofloxacin. IN

I 35 I

9 DK 175312 B1

Example 2

Preparation of 3S-7,8-difluoro-2,3-dihydro-3-methyl-4 - [(S) -N-para-toluene-sulfonylprolyl] -4H- [1,4] benzoxazine 5 [alpha]

A solution of an acid chloride prepared from 61.9 g (S) -Np-toluenesulfonyl proline and thionyl chloride in 350 ml of dried dichloromethane was added slowly and dropwise to a solution of 32.8 g (±) - 7,8-Difluoro-2,3-dihydro-3-methyl-4H- [1,4] benzoxazine and 28 ml of pyridine in 300 ml of dried dichloromethane at room temperature with stirring. Stirring was continued for an additional four hours at room temperature. The reaction mixture was washed successively with 10% hydrochloric acid, a saturated aqueous sodium bicarbonate solution and a saturated aqueous sodium chloride solution, and dried over anhydrous magnesium sulfate. The dichloromethane was removed by distillation and the oily residue was dissolved in 200 mg of ethyl acetate. To the solution was slowly and dropwise added 750 ml of n-hexane with stirring, whereby crystals of the 3R-methyl compound precipitated immediately. The precipitated crystals were separated by filtration and the filtrate was concentrated to dryness under reduced pressure. The residue was subjected to column chromatography using 500 g of silica gel and eluted with benzene / ethyl acetate (50/1 - 25/1 by volume) to give an oily product. The oily product was dissolved in 500 ml of ethanol and the solution was allowed to stand at room temperature for one day to precipitate crystals. The ethanol was distilled off and to the crystals thus obtained were added diethyl ether and n-hexane and then filtered. The solid was dried under reduced pressure to give 33.4 g of 3S-7,8-difluoro-2,3-dihydro-3-methyl-4 - [(S) -Np-toluene sulfonyl-prolyl ] 4H- [1,4] benzoxazine

I DK 175312 B1 I

I 10 I

I ((XA), where = x2 F, Rx = CH3, R2 = p-toluenesul-I

In phonyl, and n = 1), mp 107-108 ° C. IN

In [a] D = + 70.7 * (c = 0.953, chloroform). IN

In IR (cm -1): 1685, 1510, 1490. Elementary analysis

For C21H22F2N2 ° 4S: I

Calculated: (%) C 57.79 H 5.08 N 6.42 I

Found: (5) C 58.05 H 5.14 N 6.47. IN

I 10 I

In Example 3 I

In Preparation of 3S-7,8-difluoro-2,3-dihydro-I

I-3-methyl4H- [1,4-benzoxazoline (IB) -I

In 15 liters of ethanol, 32.8 g of compound I were dissolved

In the partition (IA) obtained in Example 2, and 300 ml of 1N sodium I

In hydroxide was added and refluxed for three liters

For hours. The ethanol was removed by distillation and the I

In oily residue was extracted with benzene. Ex- I

In the funnel was washed with a saturated aqueous sodium chloride

In id solution, dried over sodium sulfate and distilled I

I for the removal of benzene. The residue was exposed to carbon

In column chromatography using 200 g of silica gel I

I as the carrier and benzene as eluent to give I

12.7 g (yield: 91.4%) of 3S-7,8-difluoro-2,3-dihydro-3-

In methyl 4H- [1,4] benzoxazine as an oily product. IN

In [a] D = “5.6 * (c = 2.17, chloroform). IN

The absolute configuration of this connection

You were determined to be an S-configuration by X-ray

In 30 reanalysis on its hydrochloride. IN

I 35 I

11 DK 175312 B1

Reference Example 2

Preparation of 3 (S) -9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de] [1,4] benzoxazine-6-carboxylic acid 5 acid_

To 15.8 g of the 3S-benzoxazine derivative as obtained in Example 3 was added 24.0 g of diethylethoxymethylene malonate and the mixture was stirred at 130 to 140 ° C for 10 hours under reduced pressure. After cooling, the reaction mixture was dissolved in 50 ml of acetic anhydride and 80 ml of a mixture of acetic anhydride and concentrated sulfuric acid (2: 1 by volume) was added slowly and dropwise to the solution with stirring and ice-cooling. After continuing stirring for an additional hour at room temperature, the reaction mixture was stirred in a hot bath at a temperature of 50 to 60 ° C for 30 minutes. ice water was added to the reaction mixture and powdered potassium carbonate was added to neutralize. The mixture was extracted with chloroform and the extract was washed successively with a saturated aqueous sodium hydrogen carbonate solution and a saturated aqueous sodium chloride solution and dried over sodium sulfate. The chloroform was removed by distillation and to the residue was added diethyl ether. The crystals thus formed were collected by filtration to give 20.0 g of the ethyl ester of the title compound, mp 257-258 ° C.

[α] D = _6β »ιβ (c = 0.250, acetic acid).

In 150 ml of acetic acid, 19.5 g of the ester compound obtained above was dissolved and 400 ml of concentrated hydrochloric acid were added and then refluxed for three hours. After cooling, the precipitated crystals were collected by filtration, washed successively with water, ethanol and diethyl ether and dried to give 16.2 g of

I DK 175312 B1 I

I 12 I

In the counting compound having a melting point of 300 ° C or higher

In re. IN

In [α] D = -65.6 ° (C = 0.985, DMSO). IN

Reference Example 3 I

In Preparation of 3S-9-Fluoro-3-methyl-10- (4-methyl-1-piperidine)

In perazinyl) -7-oxo-2,3-dihydro-7H-pyrido [1,2,3-de] [1,4] -1

benzoxazine-6-carboxylic acid I

I 10 I

In I 600 ml of diethyl ether was suspended 14.3 g of I

In the carboxylic acid 1 reference Example 2 was obtained and 70 ml of I

In boron trifluoride diethyl etherate was added thereto, then I

stirred at room temperature for five hours. Superna- I

In the aqueous liquid was removed by decantation and diethyl I

In ether was added to the residue and then filtered

In court. The solid was washed with diethyl ether and I

dried. The product was dissolved in 100 ml of dimethyl sulfur

oxide, and 14.2 ml of triethylamine and 7.3 ml of N-methylpipera-I

In 20 zln was added to the solution. After the mixture was I

Stirred at room temperature for 18 hours, solution I

the agent removed by distillation. Diethyl ether was added

to the residue, and then filtered. It does

total yellow powder was suspended in 400 ml of 95% meth-I

25 anol and 25 ml of triethylamine were added. The mixture I

was heated to reflux for 25 hours. Solution I

the agent was distilled off under reduced pressure and re-I

the residue was dissolved in 500 ml of 10% hydrochloric acid and washed

three times with chloroform. The pH of the washed solution

30 value was set to 11 with an aqueous 4N sodium I

hydroxide solution and then to 7.3 with 1N hydrochloric acid. IN

The solution was extracted three times with portions of I

two liters of chloroform and the combined extract was dried

right over sodium sulfate. The chloroform was removed at 1

Distillation and the obtained crystals were recrystallized

lysed by ethanol / diethyl ether to give 12.0 g of I

DK 175312 B1 13 of the title compound having a melting point of 226-230eC (with decomposition).

[α] D = -76.9 ° (C = 0.655, 0.05N NaOH).

5 10 15 20 25 30 35!

Claims (5)

A compound according to claim 1, characterized in that both and X 2 are fluorine atoms, R 1 is a 1 methyl group and o is a hydrogen atom. A compound according to claim 1, characterized in that both X 1 and X 2 are fluorine atoms, R 1 is a methyl group and Q is a -CH = C (COOC 2 H 5) 2 group. A compound according to claim 1, characterized in that both X 1 and X 2 are fluorine atoms, is an I-methyl group and q is an N-para-toluenesulfonyl-proline-1 carbonyl group. DK 175312 B1 15 A process for the preparation of a substituted benzoxazine derivative according to claim 1 of formula (IC): 5 C00 Cohc xi \ \ 2 5 I-cooc2h5 OL 10 wherein X 2 and X 2 each represent a halogen atom, R 1 represents an alkyl group of 1-4 carbon atoms, characterized by reacting a 3S-3-alkyl-7,8-di -15 halogen2,3-dihydro-4H- [1,4] benzoxazine of formula (IB): ° nA ri with diethylethoxymethylene malonate of formula c2h5 and = c (cooc2h5) 2. 30 A process according to claim 5 for the preparation of a compound according to claim 1, characterized in that both and X 35