Title of Invention

"A PHTHALEIN AND A METHOD FOR PREPARING THE SAME"

Abstract The invention converns high purity phthalein derivatives enabling their use for medical applications or in the field of biotechnology, as well as their preparation method whereby a phathalic anhydride derivative is condensed with a naphthol or phenol derivative in an organic acid ester and the crystals of the resulting condensate are converted by action of a strong acid or one of its precursors in anhydrous medium.
Full Text FILED OF THE INVENTION
The present invention relates to high purity phthaleins and to the method for preparing them. It relates more particularly to high purity fluorescein.
In the present description, the term "high purity phthalein" is intended to mean a phthalein containing at most 1% by weight, preferably at most 0.5% by weight, of impurities.
BACKGROUND OF THE INVENTION
Phthaleins are molecules having the following xanthene unit:

(Formula Removed)
These products are useful as dyes in various industries, in particular the textile industry, the paper industry, printing, .reprography, the food industry, the cosmetics industry and the pharmaceutical industry. Phthaleins are, currently, the subject of a considerable resurgence of interest in the health field, for their diagnostic use, in particular in the context of medical imaging and in the field of the biotechnology for labeling biological molecules (nucleic acids, proteins, lipoproteins, membrane lipids) and following the intracellular or extracellular biochemical activity of biological molecules.
For example, fluorescein is a phthalein commonly used in ophthalmology for performing retinal angiography by fluorescence. The diagnostic advantage of fluorescein angiography is currently increased by the appearance of new medicinal products for treating vascular patholo-
gies of the retina and of the choroid and the availability of a new generation of retinographs that make it possible to perform digital fluorescence imaging that has higher performance levels and gives greater resolution than the former systems of acquisition on photographic emulsions.
In parallel, the quality and safety requirements of the new international pharmaceutical standards (ICH: International Commission of Harmonization, ICH Q Topic Q3A 1999) have considerably increased. The same is true with regard to the use of phthaleins in biotechnologies that require reagents of increasingly high quality. In order to satisfy the current requirements, the level of purity of the phthaleins used in the pharmaceutical field or that of biotechnology must necessarily be very high. By way of example, in the publication "Effective differences in the formulation of intravenous fluorescein and related side effects", Am. J. Ophthalmol. 78, 2: 217-221, 1974, L. Yannuzzi showed a correlation between the purity of phthaleins, in particular that of fluorescein, and the tolerance of these substances when they are administered to humans by injection.
STATEMENT OF THE INVENTION
The present invention relates to a phthalein of general formula (I):
(Formula Removed)
in which Rl, R2, R3, R4 and R5, which are identical to or different from one another, are chosen from the group comprising the following radicals or groups: hydrogen, hydroxyl, halogen, acetyl, amino, phosphate, nitro, sulfonate, carboxyl, alkylcarboxyl having from 2 to 30 carbon atoms, alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, alkyloxy having from 1 to 30 carbon atoms, haloalkyl having from 1 to 30 carbon atoms, hydroxyalkyl having from 1 to 30 carbon atoms, alkyl ester having from 2 to 40 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, carboxyalkyl having from 2 to 30 carbon atoms, aminoalkyl having from 1 to 30 carbon atoms, sulfoalkyl having from 1 to 30 carbon atoms, aryl, aryloxy, arylalkyl, haloaryl, aryl ester, succinimidyl ester, isothiocyanate, maleimide, iodoacetamide, haloacet-amide, chiorosulfonic, purine or pyrimidine bases, monosaccharides, preferably hexoses or pentoses, oligosides and polyosides, polypeptides, proteins and phospholipids,
R3 and R5 are not hydrogen when Rl is a group -CH2-CH2-COOH, R2 is a hydroxyl group and R4 is a group -COOH,
these phthaleins containing no more than 1% by weight, preferably no more than 0.5% by weight, and even more preferably not more than 0.2% by weight, of residual impurities.
DETAILED DESCRIPTION OF THE INVENTION
The high purity phthaleins according to the invention have the general formula (I):
in which Rl, R2, R3, R4 and R5, which are identical to
or differnt from one another, are chosen from the group comprising one following radicals oc groups: hydrogen, hydroxyl, halogen, acetyl, amino, phosphate, nitro, sulfonate, carboxyl, alkylcarboxyl having from 2 to 30 carbon atoms, alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, alkyloxy having from 1 to 30 carbon atoms, haloalkyl having from 1 to 30 carbon atoms, hydroxyalkyl having from 1 to 30 carbon atoms, alkyl ester having from 2 to 40 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, carboxyalkyl having from 2 to 30 carbon atoms, aminoalkyl having from 1 to 30 carbon atoms, sulfoalkyl having from 1 to 30 carbon atoms, aryl, aryloxy, arylalkyl, haloaryl, aryl ester, succinimidyl ester, isothiocyanate, maleimide, iodoacetamide, haloacet-amide, chlorosulfonic, purine or pyrimidine bases, monosaccharides, preferably hexoses or pentoses, oligosides and polyosides, polypeptides, proteins and phospholipids,
R3 and R5 not each representing hydrogen when Rl represents a group -CH2-CH2-COOH, R2 represents a hydroxyl group and R4 represents a group -COOH, these phthaleins containing no more than 1% by weight, preferably no more than 0.5% by weight, and even more preferably not more than 0.2% by weight, of residual impurities.
A phthalein that is particularly advantageous, in particular for ophthalmic applications, is fluorescein having such a purity.
It is known practice to prepare the phthaleins of formula (I) by condensation of a phthalic anhydride derivative and of a phenol derivative having a free ortho-position with respect to a hydroxyl group.
This condensation is carried out by heating at the melting temperature of a mixture of the phthalic anhydride and of the phenol derivative, in the desired
proportions.
This condensation can optionally be carried out in a dilution solvent. It can also be carried out in the presence of a catalyst.
In the absence of solvent, during the heating, the reaction medium rapidly thickens and has a tendency to harden. Within the reaction medium, areas where the temperature is too high and areas where the temperature is not high enough then form.
In the areas where the temperature is too high, the reactants and/or the reaction product are degraded and, in the areas where the temperature is not high enough, the reaction is not complete. The product obtained is of mediocre quality since it contains by-products that are very difficult to remove.
In order to improve this known method, the addition of an inert solvent or the use of a catalyst has been considered.
Thus, US patent 1,931,049 describes the addition to the reaction medium of an inert solvent consisting of a benzene-based or aliphatic hydrocarbon, more particularly ortho-dichlorobenzene. However, the condensation reaction is then incomplete, and generate intermediate products that are subsequently difficult to remove. Therefore the method described in US patent 1,931,049 does not make it possible to obtain a high purity phthalein according to the definition of the present application. Moreover, higher aliphatic hydrocarbons are not miscible with the reaction medium; consequently, they introduce no improvement in terms of thermal transfer and impair the elimination of the water formed, thereby slowing down the reaction, which takes place exclusively in a hydrophobic medium.
Regarding the catalysts that are used to improve the reaction yield, these are concentrated sulfuric acid, anhydrous zinc chloride and tin chloride.
The German patent DE 360691, describes the use of an aromatic sulfonic acid as a catalyst, in particular benzenesulfonic acid, alone or combined with one of the abovementioned three catalysts.
It so happens, however, that the addition of these catalysts leads to a reaction product that sets and hardens with entrapment of impurities, which can no longer be eliminated from the desired product.
In order to eliminate both the generated by-products and the impurities, isolation and purification methods have been developed, but none have made it possible to substantially improve the quality of phthaleins.
A conventional method consists in basifying the phthalein in an aqueous medium so as to dissolve it, and then in acidifying it so as to allow it to precipitate. These two steps are repeated successively in an attempt to eliminate the impurities. However, this method does not bring about a noticeable improvement in the purity of the product since, while the impurities dissolve with the phthalein during the basifying step, they precipitate again with the phthalein during the acidification step. In addition, this purification method has the drawback of producing a considerable amount of salts which are difficult and expensive to subsequently eliminate.
US patent 1,965,842 describes the purification of phthaleins, derived from hydroxybenzene, by direct extraction of the by-products with dichlorobenzene alone or in a mixture with other solvents. This direct extraction of the crude product with the solvent in question does not, however, make it possible to obtain
extensive elimination of impurities, which remain partly trapped in the phthalein crystals.
None of the purification methods described in the prior art makes it possible to reach a level of purity that is sufficient to allow the pharmaceutical use of phthaleins.
Given the advantage of these molecules for medical diagnosis, the production of high purity phthaleins is a real medical need and would satisfy a high demand, in particular for pharmaceutical applications in ophthalmology, for diagnosis, in particular in medical imaging, or in the field of biotechnological applications (for example, as dye to label molecules).
The inventors have, to their credit, at the end of extensive research, found that it is possible to obtain high purity products by the condensation of a phthalic anhydride with a phenol or naphthol derivative in a specific solvent which consists of an organic acid ester.
They have also found that the use of organic acid esters as solvents makes it possible to carry out this condensation with an excellent yield, greater than 75%.
Specifically, these solvents have the particularity
firstly, of leading to specific crystallization of the phthalein that derives from the condensation and of excluding, from the generated crystals, all the impurities that remain dissolved in the reaction medium, and secondly, of allowing a complete condensation that is predominant, to detrimental and unwanted side reactions, which results in the total consumption of the reactants and minimizes the formation of by-products.

The method in accordance with the invention thus makes it possible to obtain high purity phthaleins with a yield that is satisfactory from an industrial point of view.
More particularly, the invention is related to a method for preparing phthaleins, from which the residual impurities have been removed, having general formula (I):
(Formula Removed)
in which Rl, R2, R3, R4 and R5, which are identical to or different from one another, are chosen from the group comprising the following radicals or groups: hydrogen, hydroxyl, halogen, acetyl, amino, phosphate, nitro, sulfonate, carboxyl, alkylcarboxyl having from 2 to 30 carbon atoms, alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, alkyloxy having from 1 to 30 carbon atoms, haloalkyl having from 1 to 30 carbon atoms, hydroxyalkyl having from 1 to 3 0 carbon atoms, alkyl ester having from 2 to 40 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, carboxyalkyl having from 2 to 3 0 carbon atoms, aminoalkyl having from 1 to 30 carbon atoms, sulfoalkyl having from 1 to 30 carbon atoms, aryl, aryloxy, arylalkyl, haloaryl, aryl ester, succinimidyl ester, isothiocyanate, maleimide, iodoacetamide, haloacet-amide, chlorosulfonic, purine or pyrimidine bases, monosaccharides, preferably hexoses or pentoses, oligosides and polyosides, polypeptides, proteins and
phosphatepids,
R3 and R5 are not hydrogen when Rl is a
group -CH2-CH2-COOH, R2 is a hydroxyl group and R4 is a
group -COOH,
by condensation of a phthalic anhydride derivative of
formula (II) with a phenol or naphthol compound of
formula (III)
(Formula Removed)
in which Rl, R2, R3, R4 and R5 have the same meanings
as above,
in a solvent consisting of an organic acid ester.
Particularly advantageously, the starting compound (III), which is condensed with the phthalic anhydride (II), is chosen from the group comprising in particular resorcinol, orcinol, naphthol, pyrogallol, alkylamino-phenol and arylaminophenol.
When resorcinol is used as starting product, the method in accordance with the invention makes it possible to prepare fluorescein.
Advantageously, the solvent used in the method in accordance with the invention is an organic acid ester of formula (IV)
(Formula Removed)
in which R6 is chosen from the group comprising the following radicals or groups: hydrogen, alkyl having from 1 to 3 0 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, haloalkyl having from 1 to 30 carbon
atoms, hydroxyalkyl having from 1 to 3 0 carbon atoms, nitroalkyl having from 1 to 3 0 carbon atoms, aryl, aryloxy, alkylaryl, arylalkyl, substituted arylalkyl, haloaryl, aryl ester, alkyl ester having from 2 to 40 carbon atoms, and alkyloxy having from 1 to 3 0 carbon atoms, R7 representing one of the following groups: alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, haloalkyl having from 1 to 3 0 carbon atoms, hydroxyalkyl having from 1 to 30 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, aryl, aryloxy, alkylaryl, arylalkyl, substituted arylalkyl, haloaryl, aryl ester, alkyl ester having from 2 to 40 carbon atoms, or alkyloxy having from 1 to 30 carbon atoms.
Particularly advantageously, the abovementioned solvent is chosen from the group comprising methyl, ethyl, propyl or butyl benzoates, methyl, ethyl, propyl or butyl heptanoates, methyl, ethyl, propyl or butyl octanoates, methyl, ethyl, propyl or butyl laurates, methyl, ethyl, propyl or butyl myristates and methyl, ethyl, propyl or butyl palmitates, and mixtures thereof.
The solvent is chosen according to its boiling point, so as to make it possible to carry out the condensation reaction at a temperature of between 150°C and 250°C.
The condensation reaction can be carried out at atmospheric pressure or under a pressure that is adjusted according to the difference that exists between the temperature corresponding to the boiling point of the solvent and the temperature necessary to carry out the reaction, in particular under a pressure greater than atmospheric pressure when the boiling point of the compound (IV) is lower than the reaction temperature.
The condensation reaction can be carried out in the
presence of a catalyst chosen from the group comprising in particular Lewis acids, such as ZnCl2 or A1C13, Bronsted acids such as H2S04, polyphosphoric acid, or salts thereof.
Advantageously, the catalyst used is an alkali metal salt of hydrogen sulfate. Particularly advantageously, the catalyst used is potassium hydrogen sulfate (KHSO4) or sodium hydrogen sulfate. The use of hydrogen sulfate as catalyst makes it possible to obtain an excellent yield for the condensation reaction and has the advantage, unlike other catalysts, of making it possible to obtain complete condensation of the reactants, of being able to be completely eliminated from the phthalein obtained, and of not inducing the formation of tars in the reaction medium.
At the end of the condensation reaction, a crude product is obtained, the organic purity of which is already much higher than that of the products obtained with the methods of the prior art, since it is equal to or greater than 95%.
However, this purity is not yet sufficient to allow pharmaceutical use, in particular by injection. Furthermore, as shown above, the purification methods described in the prior art do not result in a process that makes it possible to notably improve this purity.
At the end of extensive research, surprisingly and unexpectedly, the inventors have found a method that considerably increases the purity of crude phthaleins resulting from the condensation reaction, by treating them with a strong acid or one of its precursors in an anhydrous organic medium.
According to an advantageous embodiment, the method in accordance with the invention consequently comprises, after the condensation reaction, a step consisting in
acidifying the product resulting from the condensation, in an anhydrous organic medium, by addition of a strong acid or one of its precursors, chosen from the group comprising in particular sulfuric acid, hydrochloric acid, hydrobromic acid, hydrofluoric acid, hydriodic acid, polyphosphoric acid, pyrophosphate (P205) , and mixtures thereof. This acidification is carried out until the phthalein crystals resulting from the condensation are converted to phthalein crystals having a different structure.
The effect of this acidification step is to convert the crude phthalein that is insoluble and dispersed in the organic medium into a form that has a different crystalline structure and is slightly soluble in this same medium. This conversion is very rapid, and takes place via an intermediate solubilization phase during which the impurities are released and completely eliminated from the phthalein crystals. This new purification method is very advantageous since it requires very little solvent and yields to a very high purity in a very short time.
According to the method of the present invention, this purification step is carried out by dispersing the crude phthalein resulting from the condensation, in an anhydrous solvent, preferably in an alcohol, a ketone, an ether or a halogenated solvent, that is either used alone or as a mixture, even more preferably in absolute ethanol or acetone, alone or as a mixture.
The dispersion of crude phthalein thus obtained is acidified by the addition of a strong acid or one of its precursors, chosen from the group comprising in particular sulfuric acid, hydrochloric acid, hydrobromic acid, hydrofluoric acid, hydriodic acid, polyphosphoric acid, pyrophosphate (P205) , and mixtures thereof.
According to a particularly advantageous embodiment, the acidification is carried out either by sparging gaseous hydrochloric acid into the phthalein dispersion, or by adding hydrochloric acid dissolved beforehand in an organic solvent.
According to another advantageous embodiment of the method in accordance with the invention, the product obtained after acidification is washed with a washing solution chosen from the group comprising water, polar solvents such as alcohols or ketones, or slightly polar solvents such as ethers and halogenated solvents, used pure or as a mixture.
At the end of the purification step, the phthaleins thus treated have a purity of greater than 98%, preferably greater than 99%, more preferably greater than 99.5%, and even more preferably of 99.8%.
The phthaleins thus obtained have the suitable quality to prepare other phthaleins of formula (I) by chemical modification of the groups Rl, R2, R3, R4 and R5 according to the conventional methods of the art, in particular to obtain phthaleins that can be used for labeling biological molecules (nucleic acids, proteins, lipoproteins, membrane lipids) and in the field of biotechnological applications (for example, for the labeling of molecules and of their intracellular or extracellular biochemical activity).
The invention is particularly suitable for preparing very high purity fluorescein, i.e. such that its content of each of the by-products of the reaction is less than or equal to 0.2%, and preferably less than or equal to 0.1%, the sum of the contents of each of these by-products being less than or equal to 0.5%.
The method for preparing a fluorescein having the abovementioned purity comprises the following
successive steps:
condensing phthalic anhydride with resorcinol, in a solvent which is an ester of an aliphatic or aromatic organic acid, preferably methyl benzoate, in the presence of a catalyst chosen from the group of Bronsted acids,
suspending the red-colored crystals obtained in the preceding step in an anhydrous solvent chosen from the group comprising alcohols such as absolute ethanol, ketones such as acetone, ethers, halogenated solvents, or mixtures thereof, acidifying the suspension obtained, by the addition of a strong acid or one of its precursors, chosen from the group comprising sulfuric acid, hydrochloric acid, hydrobromic acid, hydrofluoric acid, hydriodic acid, polyphosphoric acid, pyrophosphate (P2O5) , or mixtures thereof, until yellow-colored crystals are obtained,
washing the crystals thus obtained with a washing solution chosen from the group comprising water, alcohols, ketones, ethers and halogenated solvents, pure or as a mixture, until red-colored crystals are obtained.
An X-ray diffraction analysis of the red-colored fluorescein crystals is represented in Figure 1 ; an X-ray diffraction analysis of the yellow-colored fluorescein crystals is represented in Figure 2 ; these X-ray-diffraction analysis being obtained on the following equipment: Philips 1729 generator. Philips 1050 goniometer, Cu Kα radiation, Gonio acquisition software and Rayon processing software, under the following operating conditions:
Voltage : 40 mV
Intensity : 40 mA
Number of points : 4 000
Number of passages : 10
Acquisition period : 250 ms
Start angle (°0) : 3.000
End angle (°6) : 23,000
Standard : silicon
According to an advantageous embodiment of the method for preparing fluorescein, the catalyst used for the condensation reaction is the hydrogen sulfate of an alkali metal, preferably potassium hydrogen sulfate or sodium hydrogen sulfate.
According to another advantageous embodiment of the method for preparing fluorescein, the acidification is carried out by sparging gaseous hydrochloric acid into the fluorescein suspension or by the action, on this fluorescein, of hydrochloric acid in solution in an anhydrous organic solvent, preferably chosen from the group comprising alcohols, ketones, ethers and halogenated solvents, used alone or as a mixture, even more preferably isopropanol, absolute ethanol or acetone, pure or as a mixture.
Advantageously, the washing step is carried out with a mixture of water, of ethanol and of acetone.
By means of this method in accordance with the invention, it is possible to prepare fluorescein having a purity of greater than or equal to 99.7%, which provides unquestionable advantages, in particular for pharmaceutical uses in diagnosis, especially in medical imaging or else in the field of biotechnological applications.
The inventors have demonstrated a novel crystallographic form of fluorescein being yellow-colored crystals. This novel crystallographic form is identified by the X-ray diffraction analysis given in figure 2, which was determined under the conditions mentioned above.
They have also demonstrated a novel crystallographic form of the following compounds: 4',5'-dihydroxy-fluorescein and 4',5'-dimethylfluorescein.
Thus, the invention relates to the yellow-colored fluorescein crystals for which the X-ray diffraction analysis is given in figure 2.
The invention also relates to the yellow-colored 4',5'-dihydroxyfluorescein crystals for which the X-ray diffraction analysis is given in figure 4.
It also relates to the dark red-colored 4',5'-dimethylfluorescein crystals for which the X-ray diffraction analysis is given in figure 6.
All these spectra were determined with the equipment and under the conditions mentioned above.
The invention will be described in more detail with the aid of the following examples which are not limiting but relate to advantageous embodiments.
EXAMPLES
EXAMPLE 1: Preparation of high purity fluorescein
Synthesis of fluorescein:
A mixture comprising 55 g of resorcinol, 30 g of phthalic anhydride, 2 g of potassium hydrogen sulfate and 500 ml of methyl benzoate is brought to 200°C for 6 hours. After cooling, the red crystals of crude fluorescein are washed with acetone and dried.
Mass obtained = 51.8 g (78%).
These crystals are analyzed by X-ray crystallography under the following operating conditions:
Equipment
Philips 1729 generator Philips 1050 goniometer CU Kcx radiation Gonio acquisition software Rayon processing software
Conditions
Voltage : 40 mV
Intensity : 40 mA
Number of points : 4000
Number of passages : 10
Acquisition period : 2 50 ms
Start angle (°0) : 3.000
End angle (°8) : 23.000
Standard : silicon
The radiocrystallogram of figure 1 is obtained, for which the peaks are identified below:
(Table Removed)
Wavelength: 1.54051 A
Purification of crude fluorescein:
50 g of crude fluorescein obtained in the previous step
are stirred into 1000 ml of ethanol/acetone mixture.
Concentrated sulfuric acid is added to this mixture,
until complete conversion of the red crystals to yellow
crystals is obtained.
The yellow crystals obtained are analyzed by X-ray
crystallography as above. The X-ray diffraction
analysis of figure 2 is obtained, for which the peaks
are identified below:
(Table Removed)
Wavelength: 1.54051 A
These crystals are filtered off and then washed with an ethanol/acetone/water (40/40/20) mixture. The washing turns the yellow fluorescein crystals to red fluorescein crystals, which have a higher purity.
Purity by HPLC: 99.8%
EXAMPLE 2; Preparation of high purity 4',5'-dimethy1-fluorescein
Synthesis of 4',5'-dimethylfluorescein
A mixture comprising 62 g of 2-methylresorcinol, 30 g of phthalic anhydride, 2 g of potassium hydrogen sulfate and 500 ml of ethyl laurate is brought to 200°C for 3 hours. After cooling, the crude product is filtered and washed with acetone and then dried. The product obtained is a dark orange powder.
Mass obtained = 49.7 g (69%)
These crystals are analyzed by X-ray crystallography in the same way as in example 1. The X-ray diffraction analysis of figure 3 is obtained, for which the peaks are identified below.
(Table Removed)
Wavelength: 1.54051 A
Purification of 4',5'-dimethylfluorescein
40 g of crude 4',5'-dimethylfluorescein are added to
800 ml of ethanol/acetone mixture. Concentrated
sulfuric acid is added to this mixture, until complete
conversion of dark orange-colored crystals to yellow-
colored crystals is obtained.
The yellow crystals obtained are analyzed by X-ray
crystallography as above. The X-ray diffraction
analysis of figure 4 is obtained, for which the peaks
are identified below.
(Table Removed)
Wavelength: 1.54051 A
After filtration and recrystallization from an acetone/ water mixture or washing in ethanol/acetone/water, the yellow-colored crystals turn to dark orange-colored crystals.
EXAMPLE 3: Preparation of 4',5'-dihydroxyfluorescein
Synthesis of 4',5'-dihydroxyfluorescein
A mixture comprising 63 g of pyrogallol, 30 g of phthalic anhydride, 2 g of potassium hydrogen sulfate and 500 ml of ethyl myristate is brought to 200°C for 3 hours. After cooling, the crude product is filtered and washed with acetone and then dried. The product obtained is a grayish-brown- or anthracite-colored powder.
Mass obtained = 43.5 g (59.7%)
The crystals obtained are analyzed by X-ray crystallography as above. The X-ray diffraction analysis of figure 5 is obtained, the peaks of which are identified below.
(Table Removed)
Wavelenth: 1.54051 A
Purification, of 4' , 5' -dihydroxyfluorescein
40 g of crude 4',5'-dihydroxyfluorescein are added to 8 00 ml of ethanol/acetone mixture. Concentrated sulfuric acid is added to this mixture, until complete conversion of grayish-brown- or anthracite-colored crystals to reddish-brown- or mahogany-colored crystals is obtained.
The crystals obtained are analyzed by X-ray crystallography as above. The X-ray diffraction analysis of figure 6 is obtained, for which the peaks are identified below:
(Table Removed)
Wavelength: 1.54 051 A
After filtration and washing in water, the reddish-brown- or mahogany-colored crystals turn to grayish-brown- or anthracite-colored crystals.







WE CLAIM:
1. A phthalein of general formula (I):
(Formula Removed)
in which Rl, R2, R3, R4 and R5, which are identical to or different from one another, are selected from the group comprising the following radicals or groups: hydrogen, hydroxyl, halogen, acetyl, amino, phosphate, nitro, sulfonate, carboxyl, alkylcarboxyl having from 2 to 30 carbon atoms, alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, alkyloxy having from 1 to 30 carbon atoms, haloalkyl having from 1 to 30 carbon atoms, hydroxyalkyl having from 1 to 30 carbon atoms, alkyl ester having from 2 to 40 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, carboxyalkyl having from 2 to 30 carbon atoms, aminoalkyl having from 1 to 30 carbon atoms, sulfoalkyl having from 1 to 30 carbon atoms, aryl, aryloxy. arylalkyl, haloaryl, aryl ester, succinimidyl ester, isothiocyanate, maleimide, iodoacetamide, haloacetamide, chiorosulfonic, purine or pyrimidine bases, monosaccharides, preferably hexoses or pentoses, oligosides and polyosides, polypeptides, proteins, phospholipids,
R3 and R5 are not hydrogen when Rl is a group -CH2-CH2-COOH, R2 is a hydroxyl group and R4 is a group -COOH,
these phthaleins containing no more than 1% by weight, preferably no more than 0.5% by weight, and even more preferably not more than 0.2% by weight, of residual impurities.
2. A phthalein as claimed in claim 1, wherein the phthalein consists of fluorescein.
3. A method for preparing phthaleins as claimed in claim 1, from which the residual impurities have been removed, having the general formula (I)
(Formula Removed)
(I) in which Rl, R2, R3, R4 and R5, which are identical to or different from one another, are selected from the group comprising the following radicals or groups: hydrogen, hydroxyl, halogen, acetyl, amino, phosphate, nitro, sulfonate, carboxyl, alkylcarboxyl having from 2 to 30 carbon atoms, alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, alkyloxy having from 1 to 30 carbon atoms. haloalkyl having from 1 to 30 carbon atoms, hydroxyalkyl having from 1 to 30 carbon atoms, alkyl ester having from 2 to 40 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, carboxyalkyl having from 2 to 30 carbon atoms, aminoalkyl having from 1 to 30 carbon atoms, sulfoalkyl having from 1 to 30 carbon atoms, aryl, aryloxy. arylalkyl, haloaryl, aryl ester, succinimidyl ester, isothiocyanate, maleimide, iodoacetamide, haloacetamide, chiorosulfonic, purine or pyrimidine bases. monosaccharides, preferably hexoses or pentoses, oligosides and polyosides, polypeptides, proteins, phospholipids;
R3 and R5 are not hydrogen when Rl is a group -CH2-CH2-COOH, R2 is a hydroxyl group and R4 is a group -COOH,
Wherein a phenolic anhydride derivative of formula (II) in which R4 and R5 have the same meaning as above,
(Formula Removed)
is condensed with a compound selected from the group comprising resorcinol, orcinol,
naphthol, pyrogallol, alkylaminophenol, arylaminophenol, and a compound of
formula (III), wherein Rl, R2 and R3 have the same meaning as above.
the condensation being carried out in a solvent consisting of an organic acid ester, and
wherein the method is optionally carried out in the presence of a catalyst;
said method results in the production of phthalein of formula (I).
4. The method as claimed in either of claim 3, wherein the solvent is an organic acid
ester of formula (IV)
(Formula Removed)
in which R6 is chosen from the group comprising the following radicals or groups: hydrogen, alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, haloalkyl having from 1 to 30 carbon atoms, hydroxyalkyl having from
1 to 30 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, aryl, aryloxy, aikylaryl, arylalkyl, substituted arylalkyl, haloaryl, aryl ester, alkyl ester having from
2 to 40 carbon atoms, and alkyloxy having from 1 to 30 carbon atoms, R7 is representing one of the following groups: alkyl having from 1 to 30 carbon atoms, cycloalkyl having from 3 to 12 carbon atoms, haloalkyl having from 1 to 30 carbon atoms, hydroxyalkyl having from 1 to 30 carbon atoms, nitroalkyl having from 1 to 30 carbon atoms, aryl, aryloxy, aikylaryl, arylalkyl, substituted arylalkyl, haloaryl, aryl ester, alkyl ester having from 2 to 40 carbon atoms, or alkyloxy having from 1 to 30 carbon atoms.

5. The method as claimed in one of claims 3 and 4, wherein the organic acid ester is selected from the group comprising methyl, ethyl, propyl or butyl benzoate, methyl, ethyl, propyl or butyl heptanoate, methyl, ethyl, propyl or butyl octanoate, methyl, ethyl, propyl or butyl laurate, methyl, ethyl, propyl or butyl myristate or methyl, ethyl, propyl or butyl palmitate, and mixtures thereof.
6. The method as claimed in one of claims 3 to 5, wherein the condensation reaction is carried out at between 150°C and 250°C, optionally under pressure.
7. The method as claimed in one of claims 3, wherein the catalyst is selected from the
group comprising in particular Lewis acids, such as ZnCl2 or Aldl3, Bronsted acids
like H2SO4 or polyphosphoric acid, preferably an alkali metal hydrogen sulfate, and
more preferably potassium hydrogen sulfate (KHSO4) or sodium hydrogen sulfate
(NaHS04).
8. A phthalein compound and a method for preparing phthaleins substantially such as
herein described in the foregoing examples.



Documents:

2229-delnp-2005-abstract.pdf

2229-delnp-2005-Assignment-(11-12-2009).pdf

2229-delnp-2005-claims.pdf

2229-delnp-2005-Correspondence-Others-(11-12-2009).pdf

2229-delnp-2005-correspondence-others.pdf

2229-delnp-2005-correspondence-po.pdf

2229-delnp-2005-description (complete).pdf

2229-delnp-2005-drawings.pdf

2229-delnp-2005-Form-1-(11-12-2009).pdf

2229-delnp-2005-form-1.pdf

2229-delnp-2005-form-13.pdf

2229-delnp-2005-form-18.pdf

2229-delnp-2005-Form-2-(11-12-2009).pdf

2229-delnp-2005-form-2.pdf

2229-delnp-2005-form-26.pdf

2229-delnp-2005-form-3.pdf

2229-delnp-2005-form-5.pdf

2229-delnp-2005-pct-210.pdf

2229-delnp-2005-petition-137.pdf


Patent Number 238666
Indian Patent Application Number 2229/DELNP/2005
PG Journal Number 9/2010
Publication Date 26-Feb-2010
Grant Date 16-Feb-2010
Date of Filing 26-May-2005
Name of Patentee LABORATORIES SYNTH-INNOVE.,
Applicant Address 2 BIS, RUE DUPONT DE I EURE - 75020 PARIS.
Inventors:
# Inventor's Name Inventor's Address
1 TRAN-GUYON JOANNE 5 RUE MARCEL PAGNOL, 78180 MONTIGNY LE BRETONNEUX, FRANCE.
2 SCHERNINSKI FRANCOIS 5 RUE DES GONCOURT, 75011 PARIS, FRANCE.
PCT International Classification Number C07D 493/10
PCT International Application Number PCT/FR2003/003205
PCT International Filing date 2003-10-28
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 02/13528 2002-10-29 France