POLYMORPHS OF 5-BROMO-6-CHLORO-3-INDOXYL CAPRYLATE

Abstract

Polymorphs of 5-bromo-6-chloro-3-indoxyl caprylate characterized by the powder diffraction patterns as defined in FIG. 1 and FIG. 2.

Claims

1. 5-Bromo-6-chloro-3-indoxyl caprylate characterized by a powder diffraction pattern as defined in FIG. 1.

2. 5-Bromo-6-chloro-3-indoxyl caprylate according to claim 1 having a melting point of 63° C.±1° C. determined by DSC at a scan rate of 10.0 K/m in according to ASTM D 3418.

3. 5-Bromo-6-chloro-3-indoxyl caprylate characterized by a powder diffraction pattern as defined in FIG. 2.

4. 5-Bromo-6-chloro-3-indoxyl caprylate according to claim 3 having a melting point of 60° C.±1° C. determined by DSC at a scan rate of 10.0 K/m in according to ASTM D 3418.

5. Method of making 5-bromo-6-chloro-3-indoxyl caprylate according to claim 1 or 3, comprising: Subjecting 5-bromo-6-chloro-1H-indol-3-ol to esterification in order to obtain crude 5-bromo-6-chloro-3-indoxyl caprylate and crystallizing the crude 5-bromo-6-chloro-3-indoxyl caprylate from petroleum ether.

6. A system for detecting an esterase, comprising 5-bromo-6-chloro-3-indoxyl caprylate as defined in claim 1 or 3, or 5-bromo-6-chloro-3-indoxyl caprylate obtained in the method according to claim 5.

7. A method of detecting the presence or absence of an esterase, comprising contacting a test sample that may comprise an esterase with a compound defined in claim 1 or 3 or with a system as defined in claim 5.

Description

BRIEF DISCUSSION OF THE FIGURES

[0011] The present invention will become more apparent by reference to the following description taken in conjunction with the following figures, in which:

[0012] FIG. 1 is a powder diffraction pattern of a polymorph of 5-bromo-6-chloro-3-indoxyl caprylate (y-axis: intensity; x-axis: position [° 2Theta] [copper (Cu)]);

[0013] FIG. 2 is a powder diffraction pattern of another polymorph of 5-bromo-6-chloro-3-indoxyl caprylate (y-axis: intensity; x-axis: position [° 2Theta] [copper (Cu)]);

[0014] FIG. 3 is a comparison of the powder diffraction patterns of FIG. 1 and FIG. 2;

[0015] FIG. 4 is a DSC scans of the first and the second polymorph in comparison (y-axis: power; x-axis: temperature and scan rate of 10 K/min); a is the first run of the polymorph characterized by the powder diffraction pattern of FIG. 1 and b the second run thereof; c is the first run of the polymorph characterized by the powder diffraction pattern of FIG. 2 and d the second run thereof;

[0016] FIG. 5 is a SEM (Scanning Electron Microscope) recording of 5-bromo-6-chloro-3-indoxyl caprylate of FIG. 1 at a magnification of 497:1;

[0017] FIG. 6 is a SEM recording of 5-bromo-6-chloro-3-indoxyl caprylate of FIG. 2 at a magnification of 199:1.

DETAILED DESCRIPTION

[0018] In the following detailed description of the present invention, specific details are set forth in order to provide a more thorough understanding of the invention. In other instances, well-known features have not been described in detail to avoid obscuring the invention.

First Aspect of the Invention

[0019] Although not limited thereto, the compound of formula I may be e.g. prepared by esterification of 5-bromo-6-chloro-1H-indol-3-ol with caprylic acid chloride according to known methods.

[0020] In one embodiment, the compound of formula I obtained in the esterification of 5-bromo-6-chloro-1H-indol-3-ol is an amorphous powder.

[0021] In another embodiment, the compound of formula I obtained in the esterification of 5-bromo-6-chloro-1H-indol-3-ol is semi-crystalline.

[0022] In still another embodiment, the compound of formula I obtained in the esterification of 5-bromo-6-chloro-1H-indol-3-ol is a mixture of amorphous powder and crystals.

[0023] Desirably, the compound of formula I obtained after esterification, i.e. crude 5-bromo-6-chloro-3-indoxyl caprylate, has to be purified in order to be suitable for the targeted application. A preferred purification method is crystallization.

[0024] The term “crystallization” as used in this disclosure is synonymously used with the term “re-crystallization”.

[0025] It has been unexpectedly discovered that 5-bromo-6-chloro-3-indoxyl caprylate, when subjected to a crystallization step according to the present invention, may be isolated in the form of at least two polymorphs.

[0026] Preferably, the solvent used for the crystallization is an aprotic and non-polar solvent.

[0027] The term “aprotic” is used in this disclosure in its common meaning, i.e. the solvent is not capable to dissociate upon forming protons.

[0028] The term “non-polar” is used in this disclosure in its common meaning, i.e. the molecules of the solvent do not possess a permanent dipole moment.

[0029] Preferably, the aprotic and non-polar solvent comprises or consists of one or more hydrocarbons.

[0030] Suitable hydrocarbons are pentanes, hexanes, heptanes, octanes, nonanes and still higher alkanes and mixtures of two or more thereof.

[0031] Preferably, hydrocarbons are pentanes, hexanes, heptanes, octanes, and nonanes and mixtures of two or more thereof.

[0032] In a further preferred embodiment, the solvent is selected from a petroleum ether.

[0033] The term “petroleum ether” as used in this disclosure denotes a mixture of different alkanes such as pentanes, hexanes and heptanes, preferably a mixture of pentanes and hexanes.

[0034] In one embodiment, the aprotic and non-polar solvent, preferably the petroleum ether, has a boiling point in the range of from 40 to 100° C.

[0035] In another embodiment, the aprotic and non-polar solvent, preferably the petroleum ether, has a boiling point in the range of from 25 to 80° C.

[0036] After crystallization in the solvent, crystalline 5-bromo-6-chloro-3-indoxyl caprylate may be isolated according to known methods, e.g. by filtration and subsequent drying.

[0037] In one embodiment, 5-bromo-6-chloro-3-indoxyl caprylate obtained in the crystallization method according to the present invention is in the form of a microcrystalline and compact form. FIG. 5 shows a SEM (Scanning Electron microscope) recording of this polymorph.

[0038] This polymorph has a melting point of 63° C.±1° C. determined using a differential scanning calorimeter (DSC) at a scan rate of 10.0 k/min according to ASTM D 3418.

[0039] This polymorph of 5-bromo-6-chloro-3-indoxyl caprylate is characterized by a powder diffraction pattern as defined in FIG. 1.

[0040] In another preferred embodiment, 5-bromo-6-chloro-3-indoxyl caprylate is obtained after crystallization in the form of a cotton-like and voluminous form. FIG. 6 shows a SEM recording of this polymorph.

[0041] This polymorph has a melting point of 60° C.±1° C. determined using a differential scanning calorimeter (DSC) at a scan rate of 10.0 k/min according to ASTM D 3418.

[0042] This polymorph of 5-bromo-6-chloro-3-indoxyl caprylate is characterized by a powder diffraction pattern as defined in FIG. 2.

[0043] FIG. 3 shows a comparison of the respective powder diffraction patterns.

[0044] Without being bound by theory, it is believed that the polymorph characterized by the powder diffraction diagram of FIG. 2 is the thermodynamically stable form since the polymorph characterized by the powder diffraction pattern defined in FIG. 1 can be converted into the polymorph characterized by the powder diffraction pattern of FIG. 2 by melting. FIG. 4 shows this when the polymorph characterized by the powder diffraction pattern according to FIG. 1 is heated in a DSC in order to determine the melting point (curve a), and subsequently is cooled down and re-melted and solidified (curve b). Accordingly, the polymorph characterized by the powder diffraction pattern of FIG. 1 probably represents a metastable polymorph.

[0045] In one embodiment, 5-bromo-6-chloro-3-indoxyl caprylate characterized by a powder diffraction pattern as defined in FIG. 1 can be obtained by cooling down a petroleum ether solution saturated with the compound of formula I to a temperature of from 24° C. to 26° C. and isolating the formed crystals. Preferably, this cooling down is performed slowly.

[0046] In another embodiment, 5-bromo-6-chloro-3-indoxyl caprylate characterized by a powder diffraction pattern as defined in FIG. 2 can be obtained by cooling down a saturated petrol ether solution to a temperature below 24° C. to 26° C. and isolating the formed crystals. Preferably, this cooling down is performed fast.

[0047] Accordingly, the first aspect also encompasses a method of making 5-bromo-6-chloro-3-indoxyl caprylate characterized by a powder diffraction method defined in FIG. 1 or FIG. 2, comprising: Subjecting 5-bromo-6-chloro-1H-indol-3-ol to esterification in order to obtain crude 5-bromo-6-chloro-3-indoxyl caprylate and crystallizing the crude 5-bromo-6-chloro-3-indoxyl caprylate from petroleum ether.

[0048] Characteristic peaks of the polymorph characterized by the powder diffraction pattern defined in FIG. 1 are recorded in Table 1:

TABLE-US-00001 TABLE 1 Pos. Height FWHM Left d-spacing Rel. Int. [°2Th.] [cts] [°2Th.] [Å] [%] 5.5376 25513.71 0.1151 15.95935 50.55 7.5584 1169.66 0.1023 11.69648 2.32 8.4187 3754.91 0.1279 10.50313 7.44 10.2075 942.16 0.1023 8.66613 1.87 11.0389 37076.81 0.1407 8.01525 73.46 12.0703 2093.44 0.0640 7.33259 4.15 12.7692 3265.13 0.1279 6.93279 6.47 13.6869 1630.47 0.1151 6.46991 3.23 14.5860 3266.43 0.1151 6.07309 6.47 15.0550 369.01 0.2047 5.88492 0.73 16.0015 1256.40 0.1023 5.53890 2.49 16.7875 50473.18 0.1407 5.28129 100.00 17.8347 957.92 0.1023 4.97348 1.90 18.7199 792.65 0.1535 4.74025 1.57 19.2462 3044.08 0.1023 4.61181 6.03 19.5344 2105.44 0.0640 4.54441 4.17 19.8926 2160.67 0.0895 4.46338 4.28 20.3976 1099.47 0.1151 4.35400 2.18 20.7706 1214.26 0.1279 4.27665 2.41 21.0192 1346.51 0.1023 4.22661 2.67 21.3302 8489.90 0.1279 4.16570 16.82 22.2201 1949.07 0.1279 4.00084 3.86 22.6480 2250.79 0.0640 3.92621 4.46 23.2283 1476.95 0.0895 3.82942 2.93 23.7132 2091.51 0.1023 3.75219 4.14 24.7074 20723.83 0.1279 3.60342 41.06 25.3948 1542.02 0.1279 3.50742 3.06 25.8847 3151.10 0.1023 3.44214 6.24 26.4467 1433.38 0.1535 3.37025 2.84 27.3052 1319.69 0.1023 3.26620 2.61 27.7696 3047.14 0.0768 3.21263 6.04 28.1095 2379.87 0.1535 3.17455 4.72 28.5271 1520.60 0.1023 3.12903 3.01 28.9194 16338.76 0.1663 3.08747 32.37 29.7498 612.81 0.1535 3.00315 1.21 30.4293 629.40 0.2558 2.93762 1.25 31.7195 661.72 0.1023 2.82102 1.31 32.4181 1070.99 0.1279 2.76180 2.12 32.8161 6893.78 0.1535 2.72921 13.66 33.1576 1789.13 0.1023 2.70188 3.54 33.7673 2229.99 0.1151 2.65447 4.42 34.4493 1485.39 0.1279 2.60347 2.94 34.6259 1676.34 0.1023 2.59060 3.32 35.9047 800.50 0.1535 2.50121 1.59 36.2823 2385.33 0.1279 2.47604 4.73 37.0742 788.63 0.1791 2.42495 1.56 38.4596 7133.31 0.1151 2.34073 14.13 39.2177 393.67 0.1535 2.29721 0.78 39.7913 1541.51 0.1279 2.26541 3.05 40.4590 266.97 0.1535 2.22955 0.53

[0049] Characteristic peaks of the polymorph characterized by the powder diffraction pattern defined in FIG. 2 are recorded in Table 2:

TABLE-US-00002 TABLE 2 Pos. Height FWHM Left d-spacing Rel. Int. [°2Th.] [cts] [°2Th.] [Å] [%] 6.5175 102212.90 0.1023 13.56213 100.00 6.6308 39277.21 0.0512 13.33060 38.43 8.9286 961.50 0.1535 9.90439 0.94 11.5021 16055.72 0.1407 7.69349 15.71 12.6789 9837.40 0.1407 6.98193 9.62 12.9985 17456.36 0.1279 6.81096 17.08 14.3767 6993.04 0.1023 6.16100 6.84 14.6039 5406.42 0.1535 6.06566 5.29 15.6513 6558.35 0.1279 5.66204 6.42 16.9316 4373.57 0.1279 5.23667 4.28 17.3772 2092.36 0.1151 5.10337 2.05 18.0760 1412.13 0.1279 4.90764 1.38 18.5533 2070.24 0.1023 4.78244 2.03 19.0140 2054.71 0.1535 4.66760 2.01 19.2918 6812.08 0.1279 4.60099 6.66 20.3781 8838.61 0.1023 4.35812 8.65 20.8525 3360.93 0.1151 4.26003 3.29 21.0979 2391.37 0.1023 4.21103 2.34 21.3976 2304.30 0.1023 4.15273 2.25 21.6361 4231.65 0.1407 4.10749 4.14 22.3646 9474.15 0.1663 3.97532 9.27 23.0879 7568.22 0.1791 3.85238 7.40 23.6352 1811.11 0.1279 3.76440 1.77 24.0357 1351.87 0.1279 3.70257 1.32 24.6134 6944.84 0.1407 3.61696 6.79 25.1249 9121.06 0.1535 3.54448 8.92 25.3109 9316.60 0.0780 3.51594 9.11 25.3814 8236.42 0.0640 3.50924 8.06 25.9218 3656.63 0.0768 3.43730 3.58 26.1124 6242.41 0.0640 3.41263 6.11 26.4193 12612.88 0.1919 3.37368 12.34 26.8802 3176.88 0.1663 3.31687 3.11 27.3671 961.55 0.1535 3.25896 0.94 27.8189 3565.15 0.1535 3.20705 3.49 28.3266 1594.11 0.1535 3.15071 1.56 28.7231 1066.77 0.1535 3.10812 1.04 29.4019 3810.05 0.0768 3.03789 3.73 29.8329 1048.47 0.1535 2.99498 1.03 30.4091 1351.44 0.1279 2.93952 1.32 31.3182 1482.25 0.1535 2.85624 1.45 31.9404 5329.56 0.0936 2.79969 5.21 32.0017 5909.08 0.0768 2.79678 5.78 32.7997 2862.93 0.1791 2.73053 2.80 33.6102 1511.81 0.2303 2.66652 1.48 34.2052 974.97 0.1279 2.62149 0.95 34.5399 2345.48 0.1791 2.59685 2.29 35.0704 1472.83 0.2047 2.55877 1.44 35.8845 2007.99 0.0895 2.50257 1.96 36.2983 1993.39 0.1279 2.47498 1.95 36.9614 420.85 0.2558 2.43209 0.41

Second Aspect of the Invention:

[0050] According to a second aspect, the present invention relates to a system for detecting an esterase.

[0051] The systems that use chromogenic compounds such as the compound of formula I are typically plates for bacteriology filled with an aqueous culture media composed by classic ingredients like agar and various organic or salt nutrients suitable to the growth of the microorganisms comprising said esterase. Such systems are known in the art.

[0052] Accordingly, the present invention further relates to a system for detecting an esterase, comprising a polymorph of 5-bromo-6-chloro-3-indoxyl caprylate as defined in the first aspect.

[0053] In a preferred embodiment, said esterase is produced by Salmonella species.

Third Aspect of the Invention

[0054] According to a third aspect, the present invention relates to a method of detecting the presence or absence of an esterase. The basic principles of such method are as discussed above in the BACKGROUND section.

[0055] Accordingly, the present invention relates to a method of detecting the presence or absence of an esterase, comprising contacting a test sample that may comprise an esterase with a polymorph as defined in the first aspect or with a system as defined in the third aspect.

[0056] The test sample may be a bacterium such as Salmonella species or a substrate comprising a bacterium.