CZ307419B6 - A method of determining the enantiomeric purity of chiral sulfoxides using 1 H-NMR analysis - Google Patents

Abstract

The invention submitted  relates to a method of determining the enantiomeric purity of chiral sulfoxides usingH-NMR analysis utilizing urea of general formula I wherein R has the meaning described in the text as a chiral solvating agent.

Description

Technical field

The present invention relates to a method for determining the enantiomeric purity of chiral sulfoxides by 1 H-NMR analysis using urea based on binaphthalene as a chiral solvating agent.

BACKGROUND OF THE INVENTION

Optically pure chiral sulfoxides are useful in the field of enantioselective organic synthesis. See, e.g., Carreno, M. C. Chemical Reviews 1995, 95, 1717-1760; Walker, A.J. Tetrahedron-Asymmetry 1992, 3, 961-998; Solladie, G. Synthesis-Stuttgart 1981, 185-196; Posner, G. H. Accounts of Chemical Research 1987, 20, 72-78.

Chiral sulfoxides also play an important role in the pharmaceutical field. Chiral sulfoxides include, for example, platelet aggregation and adhesion inhibitor OPC-29030 (Morita, S .; Matsubara, J .; Otsubo, K .; Kitano, K .; Ohtani, T .; Kawano, Y .; Uchida, M. Tetrahedron- Asymmetry 1997, 8, 37073710; Matsugi, M .; Fukuda, N .; Muguruma, Y .; Yamaguchi, T .; Minamikawa, J .; Otsuka, S. Tetrahedron 2001, 57, 2739-2744).

OPC-29030 as well as CNS 5788 ion channel blocker (Padmanabhan, S .; Lavin, R. C .; Durant, G.J. Tetrahedron-Asymmetry 2000, 11, 3455-3457).

CNS 5788 and armodafinil analeptic (Loland, CJ; Mereu, M .; Okunola, OM; Cao, J .; Prisinzano, TE; Mazier, S .; Kopajtic, T .; Shi, L; Katz, J. L; Tanda, G .; Newman, AH Biological Psychiatry, 2012, 72, 405-413).

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and a large group of proton pump inhibitors, the so-called prazoles (Andersson, T .; Weidolf, L. Clinical Drug Investigation 2008, 28, 263-279). The most prominent representative of this group is esomeprazole (Olbe, L; Carlsson, E .; Lindberg, P. Nature Reviews Drug Discovery 2003, 2, 132139).

esomeprazole

Of the possible analytical techniques applicable to the enantiomeric purity determination, the measurement of NMR spectra, despite lower sensitivity, is preferred in terms of speed and simple sample preparation. Chiral solvating agents are used for this purpose. An extensive overview of this issue can be obtained, for example, from Wenzel, T.J. Discrimination of chiral compounds using NMR spectroscopy; Wiley: Hoboken, N.J., 2007.

The chiral solvating agent should provide the greatest possible resolution of the characteristic signals and should be useful in standard NMR solvents (optimally CDCl ₃ ).

Many chiral solvating agents for sulfoxides have been described in the literature. Among the materials useful in CDCl 3 as the most common solvent used for NMR, for example, a compound of the formula:

used in CDCl3 on sulfoxides of the type R-SO-CH3 with the results summarized in the following table:

-2GB 307419 B6

R Δ (ppm) for -SO-CH 3 octyl 0,053 heptyl 0.040 hexyl 0,048 pentyl 0,088 butyl 0,080 4-methylphenyl 0,048 3-methylphenyl 0,123 phenyl 0.052 2-pyridyl 0,044

(Toda, F .; Toyotaka, R .; Fukuda, H. Tetrahedron-Asymmetry 1990, 1, 303-306).

Another option is (S) -2-methoxyphenylacetic acid (Buist, PH; Marecak, D .; Holland, H. L; Brown, FM Tetrahedron-Asymmetry 1995, 6, 7-10), which was used in CDCl _3. for example, for sulfoxides of the type R-SO-CH3 with the results summarized in the following table:

R Δ (ppm) for -SO-CH 3 cyclohexyl 0.013 benzyl 0.016 4-methoxybenzyl 0.017 4-fluorobenzyl 0.020 4-cyanobenzyl 0.030

The substance most commonly used to determine the enantiomeric purity of sulfoxides is the compound of the formula:

(See Deshmukh, M .; Dunes, E .; Juge, S .; Kagan, B. Tetrahedron Letters 1984, 25, 3467-3470)

The measurement results for the CDC1 ₃ sulfoxides R-SO-CH3 are summarized in the following table:

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R Δ (Hz) for -SO-CH3 4-methylphenyl 6.5 4-nitrophenyl 4.4 4-hydroxymethylphenyl 5.7 4-hydroxyphenyl 8.1 n-octyl 4.4 tert-butyl 5.3 cyclohexyl 5.2 3-phenylpropyl 4.4 naphthalen-2-yl 10.0

Another preferred option, especially in terms of molecule simplicity, is 1,1'-binaphthalene-2,2'diol (Toda, F .; Sea, K.; Okada, J .; Node, M .; Itoh, A. Oomine, K .; Fuji, K. 5 Chemistry Letters 1988, 131-134 and Toda, F .; Sea, K .; Sato, A. Bulletin of the Chemical Society of Japan 1988, 61, 4167-4169), whose results when used on sulfoxides of the type R-SO-CH ₃ are summarized in the following table:

R Δ (ppm) for -SQ-CH 3 n-butyl 0.018 (3 eq. Of reagent) n-pentyl 0.020 (2 eq. Of reagent) n-hexyl 0.016 (2 eq. Reagents) n-heptyl 0.017 (2 eq. Of reagent) phenyl 0.013 (1 eq. Of reagent) 3-methylphenyl 0.017 (2 eq. Of reagent) 4-methylphenyl 0.013 (1 eq. Of reagent)

The same reagent has also been used to determine the enantiomeric purity of omeprazole, for example (Redondo, J .; Capdevila, A .; Latorre, I. Chirality 2010, 22, 472-478):

omeprazole, with the results of CDC1 ₃ measurements being summarized in the following table:

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signal Δ δ (ppm) 13-CH 0,055 8-CH 2 0.014 15-CH3 0.016 14-CH3 0.007

None of the above reagents are completely universal and there is still a need for new, more effective chiral solvating agents that are simple and allow the enantiomeric purity of a wide range of sulfoxides to be determined.

Description of the invention

The present invention provides a method for determining the enantiomeric purity of chiral sulfoxides by NMR comprising the addition of a compound of Formula I:

in which

R represents

C 1-6 alkyl optionally substituted by one or more substituents selected from halogen, nitro, cyano, carboxyl, aldehyde, hydroxyl, amino or C 1 -C ₆ alkoxy,

C 2-6 alkenyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl, aldehyde, hydroxyl, amino or C 1 -C ₆ alkoxy,

C ₂ 6 alkynyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl group, aldehyde group, hydroxyl group, amino or C-Cd alkoxy,

C ₃ -C 10 cycloalkyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl groups, aldehyde groups, hydroxyl groups, amino groups or _Ci-C6 alkoxy,

C ₃ _io cycloalkenyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl groups, aldehyde groups, hydroxyl groups, amino or C1-C6 alkoxy groups or

_C6-IO aryl optionally substituted with one or more substituents selected from C] -C ₆ alkyl optionally substituted with one or more halogen atoms, halogen, nitro,

The cyano, carboxyl, aldehyde, hydroxyl or C 1 -C ₆ alkoxy group, in the R- or 5k configuration of a chiral sulfoxide solution in a deuterated solvent, and 1 H-NMR analysis.

In a preferred embodiment, R in formula I is selected from the group consisting of 3,5bis (trifluoromethyl) phenyl, phenyl, 3,5-dimethylphenyl, cyclohexyl and hexyl.

In a also preferred embodiment, the deuterated solvent is deuterated chloroform.

Thus, in a preferred embodiment, the method of the invention uses a compound of formula I wherein R is hexyl, i.e. a compound of formula:

Thus, in a further preferred embodiment, a compound of formula I in which R represents cyclohexyl, i.e. a compound of formula:

Thus, in a further preferred embodiment, the method of the invention uses a compound of formula I wherein R is phenyl, i.e. a compound of formula:

Thus, in a further preferred embodiment, the method of the invention uses a compound of formula I wherein R is 3,5-dimethylphenyl, i.e. a compound of formula:

-6GB 307419 B6

Thus, in a further preferred embodiment, the process of the invention uses a compound of formula I wherein R is 3,5-bis (trifluoromethyl) phenyl, i.e. a compound of formula:

In this description

C | C ₆ alkyl represents linear or branched alkyl consisting of 1 to 6 carbon atoms;

_C2 _6 alkenyl represents a straight or branched alkenyl of 2 to 6 carbon atoms and containing one or more double bonds.

C ₂ _ ₆ alkynyl represents a linear or branched alkynyl composed of 2 to 6 carbon atoms and containing one or more triple bonds.

C 3-10 cycloalkyl represents a cyclic hydrocarbon radical having from 3 to 10 carbon atoms.

C ₃ .10 cycloalkenyl is a cyclic hydrocarbon radical having 3 to 10 carbon atoms and containing one or more double bonds, that is not aromatic.

_C6-IO aryl represents an aryl radical of from 6 to 10 carbon atoms.

The C 1 -C ₆ alkoxy group represents C _1-6 C ₆ alkyl attached from the rest of the molecule via an oxygen atom.

Ureas are known to form hydrogen bonds with polar functional groups (eg, carboxyl). In the case of the sulfoxide, it is believed that there is an interaction between the urea and the sulfoxide oxygen atom. Due to the presence of a bulky binaphthalene residue, the molecule will have to be arranged so that the substituents attached to the sulfoxide moiety allow sulfoxide-urea interaction, thereby enantioselective complexation of sulfoxides.

When substituents attached to urea drain electrons, the tendency to form a hydrogen bond is stronger. In order to verify the effect of the substituents on the ability to complex, we prepared five different derivatives of the above formula. Specifically, compounds bearing alkyl (hexyl), cycloalkyl (cyclohexyl), aryl (phenyl), aryl groups bearing electrondonomy groups (3,5 dimethylphenyl) and aryl groups bearing an electronception group (3,5-bis (trifluoromethyl) phenyl). The above theoretical assumption was confirmed, ie the compound bearing the electron acceptance of the 3,5 bis (trifluoromethyl) phenyl group interacts most strongly with the sulfoxides. At the same time, it has also been shown that all other ureas prepared are useful for determining enantiomeric purity by < 1 > -NMR analysis.

In order to determine the enantiomeric purity of the sulfoxide by 1 H-NMR analysis, the ligand must preferably interact with one of the two enantiomers. Because the ligand is enantiomerically pure, the complex formed by the interaction with the sulfoxide is a diastereomeric. Both diastereomeric complexes then have different chemical shifts in the 1 H-NMR spectrum. The difference in chemical shifts must be such that the ratio of the two enantiomers in the mixture can be read by integrating the newly formed signals.

The solvent selected for measurement has a significant effect on the above formation of diastereomeric complexes. It is true that the more polar the solvent, the more difficult the complex formation is because solvation with the solvent (both urea and sulfoxide) competes with the complex. Therefore, in some prior art cases, it is necessary to use carbon tetrachloride as a strongly non-polar, noncompetitive solvent. However, sulfoxides are polar and solubility problems may arise. The most common solvent used for 1 H-NMR measurement is deuterated chloroform. Therefore CDC1 ₃ was used for all measurements performed in this invention. Another most widely used solvent is deuterated dimethyl sulfoxide, which is in principle unusable as a sulfoxide for the measurements made in this invention. In no case tested chloroform had to be supplemented with carbon tetrachloride to reduce solvent polarity. Therefore, the compounds of this invention are readily useful in routine * HNMR measurements performed in CDCl3.

Another factor affecting the enantiomeric purity of sulfoxide by 1 H-NMR analysis is the concentration of the measured samples. The amount of sulfoxide used in the prior art is typically 10 mg sulfoxide per measurement or 1 mg sulfoxide per measurement in 0.5 mL CDCl 3. To compare the results, the measurements of this invention were performed with 10 mg of sulfoxide per measurement in 0.5 mL of CDCl3 and then the sample was diluted to an order of 0.5 mg of sulfoxide per measurement in 0.5 mL of CDCl3. The results of these measurements are shown in the Examples below. In selecting the optimum amount, it is to be understood that the use of the highest amount, i.e. 10 mg sulfoxide, requires the addition of an equimolar amount of urea, which is of the order of 50 mg. This, on the one hand, increases the consumption of the chiral solvating agent and also in some cases causes dissolution problems. The lowest amount to be used depends on whether a 1 H-NMR spectrum can be obtained, the integration of which makes it possible to evaluate the ratio of enantiomers in the mixture.

Another variable affecting the enantiomeric purity of sulfoxide by 1 H-NMR analysis is the amount of urea used. If the urea-sulfoxide interaction is strong enough, an amount less than equimolar is sufficient. The use of less than equimolar amounts of urea is preferred from the viewpoint of carrying out the experiment. On the one hand, the consumption of the urea in question is lower and, therefore, it is not necessary to accurately weigh the amount of substances. It is sufficient to gradually add urea to the sulfoxide solution until the signal splitting is such that the ratio of the two enantiomers can be determined from the spectrum by integration. In testing urea additions lower than equimolar, all ureas have been shown to provide signal splitting in the 1 H-NMR spectrum, with best results being obtained with urea bearing 3,5-bis (trifluoromethyl) phenyl residues where signal splitting is evident even with 0.05 molar equivalents.

Compared to the prior art, the method of determining the enantiomeric purity of the present invention is more advantageous in that it was not necessary to use a mixture of CDCl 3 with a less polar solvent in either case. For all sulfoxides tested, the 1 H-NMR spectrum was measured to allow enantiomer ratio determination.

-8EN 307419 B6

DETAILED DESCRIPTION OF THE INVENTION

NMR spectra measurements were performed on a Varian Mercury Plus 300 instrument with an operating frequency of 299.97 MHz for 1 H and 75.44 MHz for ¹³ C.

Starting substances:

The isocyanates were purchased from Sigma-Aldrich and used without further purification and (7 R) 1,1'-binaphthalene-2,2'-diamine was prepared according to a previously published procedure (Yamamoto, Y .; Sakamoto, A .; Nishioka) , T .; Oda, J .; Fukazawa, Y. Journal of Organic Chemistry 1991, 56, 1112-1119).

General procedure for the preparation of ureas of formula (I) - 1,1'-binaphthalene-2,2'-diamine was dissolved in anhydrous dichloromethane. To this solution was added the corresponding isocyanate, the reaction mixture was stirred at room temperature, and the progress of the reaction was monitored by TLC on silica gel (mobile phase dichloromethane).

(R) -2,2'-Bis [N - (3,5-bis (trifluoromethyl) phenyl) ureido] -1,1'-binaphthalene 1:

This material was prepared according to a previously published procedure (Stibor, L; Holakovsky, R .; Mustafina, A. R .; Lhotak, P. Collection of Czechoslovak Chemical Communications 2004, 69, 365-383) in 98% yield.

1 H-NMR (CDCl 3 δ: 8.05 (d, J = 8.9 Hz, 2H), 7.95 (d, J = 9.0 Hz, 2H), 7.85 (d, J = 8, 1 Hz, 2H), 7.51 (s, 4H), 7.46 (s, 2H), 7.40 (t, J = 7.6 Hz, 2H), 7.38 (s, 2H), 7 20 (t, J = 1.6 Hz, 2H), 6.98 (d, J = 8.1 Hz, 2H), 6.91 (s, 2H).

¹³ C-NMR (CDCl ₃ ) δ: 153.48, 139.38, 134.40, 132.90, 132.43, 132.09, 131.43, 130.12, 128.49, 127.60, 126.04, 125.39, 124.34, 122.82, 121.62, 118.82.

Melting point: 142 DEG-143 DEG C., (R) -2,2'-Bis (N-phenylureido) -1,1'-binaphthalene 2:

(2)

(6 R) -2,2'-Bis (N-phenylureido) -1,1'-binaphthalene was prepared according to the general procedure by reaction of (R) 1,1'-binaphthalene-2,2'-diamine ( 2 g, 7.03 mmol) with phenyl isocyanate (1.79 g, 15 mmol) in anhydrous dichloromethane (60 mL) for 24 h. A white precipitate formed from the reaction mixture, which was filtered off and dried under reduced pressure. Yield 3.45 g (94%).

1 H-NMR (CDCl 3) δ: 8.22 (d, J = 9.0 Hz, 2H), 7.93 (d, J = 9.0 Hz, 2H), 7.85 (d, J = 8) 0.1 Hz, 2H), 7.37 (t, J = 7.0 Hz, 2H), 7.18 (t, J = 7.0 Hz, 2H), 7.08-6.78 (m, 12H) 6.68 (s, 2H), 6.61 (s, 2H).

¹³ C-NMR (CDCl ₃ ) δ: 153.97, 137.39, 135.60, 132.83, 130.98, 129.68, 129.09, 128.34.127.19, 125.30, 125.17, 124.22, 122.31, 121.24, 121.02.

Melting point: 150-151 ° C, (R) -2,2'-bis [N - (3,5-dimethylphenyl) ureido] -1,1-t-binaphthalene 3:

(R) -2,2'-bis [N '- (3,5-dimethylphenyl) ureido] -1,1'-binaphthalene was prepared according to the general procedure for the reaction of (R) -1,1'-binaphthalene-2,2 1-diamine (2 g, 7.03 mmol) with 3,5-dimethylphenyl isocyanate (2.208 g, 15 mmol) in anhydrous dichloromethane (30 mL) for five days. A white precipitate formed from the reaction mixture, which was filtered off and crystallized from chloroform. Yield 2.00 g (98%).

¹ H-NMR (CDCl ₃ ) δ: 8.20 (d, J = 9.0 Hz, 2H), 7.88 (d, J = 9.0 Hz, 2H), 7.80 (d, J = 8.1 Hz, 2H), 7.33 (t, J = 7.0 Hz, 2H), 7.11 (t, J = 7.0 Hz, 2H), 6.92 (d, J = 8, 5 Hz, 2H), 6.80 (s, 2H), 6.70 (s, 2H), 6.55 (s, 2H), 6.50 (s, 4H), 2.04 (s, 12H) .

¹³ C-NMR (CDCl ₃ ) δ: 154.21, 138.73, 137.18, 135.63, 132.86, 130.93, 129.72, 128.28, 127.01, 126.18, 125.32, 125.18, 122.51, 122.35, 119.14,21.25.

Melting point: 189-190 ° C.

()) -2,2'-Bis (77-cyclohexylureido) -1,1'-binaphthalene 4:

(R) -2,2'-bis (N -cyclohexylureido) -1,1'-binaphthalene was prepared according to the general procedure by the reaction of (R) -1,1'-binaphthalene-2,2'-diamine (0.284 g, 1 mmol) with cyclohexyl isocyanate (0.626 g, 5 mmol)

-107 307419 B6 in anhydrous dichloromethane (9 mL) for five days. The reaction mixture was evaporated and dried under very low pressure to remove excess cyclohexyl isocyanate. Yield 0.508 g (95%).

1 H-NMR (CDCl 3) δ: 8.39 (d, J = 9.0 Hz, 2H), 7.97 (d, J = 9.0 Hz, 2H), 7.88 (d, J = 7) 9 Hz, 2H), 7.37 (t, J = 7.0 Hz, 2H), 7.20 (t, J = 7.7 Hz, 2H), 6.97 (d, J = 8.5 Hz, 2H), 6.15 (s, 2H), 4.66 (s, 2H), 3.28 (m, 2H), 1.83-0.77 (m, 20H).

¹³ C-NMR (CDCl ₃ ) δ: 155.25, 136.52, 133.05, 130.59, 129.61, 128.24, 126.96, 125.33, 124.84, 121.97, 119.55, 49.41, 33.49, 25.54, 24.97.

M.p .: 148-149 ° C.

(R) -2,2'-Bis (N-hexylureido) -1,1'-binaphthalene 5:

(5) (R) -2,2'-bis (N-hexylureido) -1,1-t-binaphthalene was prepared according to the general procedure by the reaction of (R) 1, T-binaphthalene-2,2'-diamine (0.284 g, 1 mmol) with hexyl isocyanate (0.508 g, 4 mmol) in anhydrous dichloromethane (9 mL) for five days. The reaction mixture was evaporated and dried under very low pressure to remove excess hexyl isocyanate. Yield 0.501 g (93%).

1 H-NMR (CDCl 3) δ: 8.19 (d, J = 9.0 Hz, 2H), 7.89 (d, J = 9.0 Hz, 2H), 7.82 (d, J = 8) 1 Hz, 2H), 7.34 (t, J = 7.5Hz, 2H), 7.12 (t, J = 7.6Hz, 2H), 6.92 (d, J = 8.4 Hz, 2H), 6.38 (s, 2H), 4.83 (s, 2H), 2.88 (dd, J = 6.6 Hz, 4H), 1.60 - 0.97 (m, 16H) 0.84 (t, J = 7.0 Hz, 6H).

¹³ C-NMR (CDCl 3) δ: 156.10, 136.33, 133.04, 130.67, 129.56, 128.21, 126.90, 125.41, 124.88, 122.20, 120 , 15, 40.51, 31.57, 29.94, 26.61, 22.67, 14.15.

Melting point: 123-124 ° C.

Examples of cleavage of signals of enantiomers of sulfoxides in the '-NMR spectrum in CDCl ₃

Phenyl (methyl) sulfoxide + 1 equivalent of urea of formula I

10 mg of sulfoxide in 0.5 ml of CDCl3 was used as the starting concentration except for the use of ureas whose solubility did not allow such a high concentration. Specifically, for R = cyclohexyl concentration was 6.67 mg sulfoxide in 0.5 ml CDC1 ₃ for R = phenyl, the concentration of 4 mg of the sulfoxide in 0.5 mL of CDCl ₃ and R = 3,5-dimethylphenyl concentration was 2.5 mg sulfoxide in 0.5 ml CDC1 _third The measurement results and all corresponding molar concentrations are given in the following table:

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R Δ (ppm) -CH 3 Δ (Hz) _-CH3 hexyl (c = 142.7mM) 0.01 3.06 cyclohexyl (c = 95, 1mM) 0,002 0.61 phenyl (c = 57.1mM) 0.005 1,27 3,5-dimethylphenyl (c = 35.7mM) 0.012 3.43 3,5-bis (trifluoromethyl) phenyl (c = 142.7mM) 0,058 17.15

Better results were obtained at higher concentrations but limited by the solubility of ureas. Urea bearing 3,5-bis (trifluoromethyl) phenyl residues gave the best results. When using this urea even at a concentration of 0.50 mg in 0.5 ml sulfoxide CDC1 ₃ (7 mM), rose cleavage of the methyl group signals of 0,012 ppm (3.66 Hz).

tert-butyl (methyl) sulfoxide + 1 equivalent of a urea of formula I concentration of 10 mg of the sulfoxide in 0.5 ml CDC1 ₃ (166,4mM)

R A (ppm) Δ (Hz) hexyl 0.05 (CH ₃ ) 0.015 (t-Bu) 15.17 (CH ₃ ) 4.61 (t-Bu) cyclohexyl * 0.023 (CH ₃ ) 0.01 (t-Bu) 7.03 (CH _3), 2.90 (t-Bu) phenyl ** 0.042 (CH ₃ ) 0.017 (t-Bu) 12.60 (CH _3), 5.00 (t-Bu) 3,5-dimethylphenyl *** 0.037 (CH ₃ ) 0.012 (t-Bu) 11.10 (CH _3), 3.80 (t-Bu) 3,5-bis (trifluoromethyl) phenyl 0.111 (CH ₃ ) 0.036 (t-Bu) 33.42 (CH3) 10.72 (t-Bu) * concentration of 5 mg sulfoxide in 0.5 ml CDCl3 (83.2mM) ** concentration of 4 mg sulfoxide in 0.5 ml CDCl ₃ (66.7mM) *** concentration 2.86 mg sulfoxide in 0.5 ml CDCl3 ( 47,5mM)

As in the previous case, better results were obtained at higher concentrations. Only in the case of urea bearing a 3,5-dimethylphenyl radicals at the highest concentration used (4 mg in 0.5 ml sulfoxide CDC1 ₃ (66.7 mM)) overlaps the signal of the methyl group of the methyl sulphoxide signal urea group. The tert-butyl methyl group cleavage at this concentration was 0.014 ppm (4.12 Hz). Only at the concentration indicated in the table was it possible to read the ratio of the two methyl group signals. Again, urea bearing 3,5-bis (trifluoromethyl) phenyl residues yielded the best results. Using this urea at a concentration of 0.50 mg sulfoxide in 0.5 mL CDCl 3 (8.2 mM), the cleavage of the methyl group signals reached 0.072 ppm (21.63 Hz).

- 12GB 307419 B6

Omeprazole + 1 urea equivalent of Formula I

concentration of 10 mg sulfoxide in 0.5 ml CDCl ₃ (57.9 mM):

R Δ δ (ppm) Δ δ (Hz) hexyl 0.130 (13-CH) 0.102 (8-CH 2) 0.018 (I7-OCH3) 0.004 (I6-OCH3) 0.069 (I5-CH3) 0.021 (I4-CH3) 39.09 (13-CH) 30.80 (8-CH 2) 5.52 (I7-OCH3) 1.45 (I6-OCH3) 20.72 (IS-CH3) 6.29 (I4-CH3) cyclohexyl 0.029 (13-CH) 0.087 (8-CH 2) 0.009 (I7-OCH3) 0.000 (I6-OCH3) 0.019 (IS-CH3) 0.036 (I4-CH3) 8.70 (13-CH) 26.30 (8-CH 2) 2.59 (I7-OCH3) 0.00 (I6-OCH3) 5.57 (I5-CH3) 10.62 (14-CH3) phenyl * 0.056 (13-CH) 0.189 (8-CH 2) 0.049 (I7-OCH3) 0.033 (I6-OCH3) 0.023 (I5-CH3) 0.022 (I4-CH3) 16.87 (14-CH) 56.87 (8-CH 2) 14.74 (I7-OCH3) 9.97 (I6-OCH3) 7.00 (I5-CH3) 6.44 (I4-CH3) 3,5-dimethylphenyl ** 0.021 (13-CH) 0.160 (8-CH 2) 0.019 (I7-OCH3) 0.014 (I6-OCH3) 6.56 (13-CH) 47.84 (8-CH 2) 5.68 (I7-OCH3) 4.09 (I6-OCH3) 3,5-bis (trifluoromethyl) phenyl 0.009 (13-CH) 0.209 (8-CH 2) 0.071 (I7-OCH3) 0.029 (I6-OCH3) 0.012 (14-CH3) 0.020 (I5-CH3) 2.58 (13-CH) 62.62 (8-CH 2) 21.03 (I7-OCH3) 8.60 (I6-OCH3) 3.45 (I4-CH3) 6.06 (I5-CH3)

* concentration of 6.67 mg omeprazole in 0.5 ml CDCl3 (38.6 mM) ** concentration of 3.33 mg omeprazole in 0.5 ml CDCl3 (19.3 mM), omeprazole CH3 signals are obscured by ligand CH3 signals

- 13 GB 307419 B6

As in the previous case, better results were obtained at higher concentrations. Again, urea bearing 3,5-bis (trifluoromethyl) phenyl residues yielded the best results. When using this urea even at a concentration of 0.50 mg in 0.5 ml sulfoxide CDC1 ₃ (3.6M) achieved signals split doublets CH ₂ group adjacent to a sulfoxide 0.209 ppm (62.62 Hz) as well as all the other at this concentration, the cleavage of the doublet signal of the CH ₂ group adjacent to the sulfoxide group was fully sufficient to evaluate the enantiomeric purity. Specifically, for hexyl 0.110 ppm (32.99 Hz), cyclohexyl 0.111 ppm (33.42 Hz), phenyl 0.181 ppm (54.20 Hz) and 3,5-dimethylphenyl 0.123 ppm (36.27 Hz).

Modafinil + 1 urea equivalent of Formula I

10mg sulfoxide in 0.5 ml CDC1 ₃ (73,2mM)

R Δ δ (ppm) Δδ (Ηζ) hexyl 0.221 (CH) 0.102 (NHz) 66.45 (CH) 30.44 (NH ₂ ) cyclohexyl 0.188 (CH) 0.075 (NHz) 56.64 (CH) 22.57 (NH ₂ ) phenyl 0.549 (CH) 0.026 (NH ₂ ) 164.64 (CH) 7.76 (NH ₂ ) 3,5-dimethylphenyl 0.432 (CH) 147.5 (CH) 3,5-bis (trifluoromethyl) phenyl 0.499 (CH) 0.055 (NH ₂ ) 0.064 (NH ₂ ) 149.70 (CH) 16.46 (NH ₂ ) 19.11 (NH ₂ )

As in the previous case, better results were obtained at higher concentrations. The best results were obtained by urea bearing phenyl residues. When using this urea even at a concentration of 0.50 mg in 0.5 ml sulfoxide CDC1 ₃ (3.6M), rose cleavage signals CH group adjacent to a sulfoxide 0.171 ppm (51.17 Hz), but also with other ureas have been at this concentration, the cleavage of the CH group signal adjacent to the sulfoxide group is sufficient to evaluate the enantiomeric purity. Specifically for hexyl 0.034 ppm (10.08 Hz), cyclohexyl 0.037 ppm (11.05 Hz), 3,5-bis (trifluoromethyl) phenyl 0.236 ppm (70.83 Hz) and 3,5-dimethylphenyl 0.094 ppm (28, 04 Hz).

For hexyl-bearing urea at higher concentrations (2.5 mg of modafmil in 0.5 ml of CDCl ₃ , i.e. up to 18.3 mM), the CH group signal partially overlaps with the urea NH signal, and therefore the enantiomeric purity is difficult to evaluate. However, one hydrogen signal from the amide group of modafmil can be used here, which is cleaved so that the enantiomeric purity can be readily determined (0.08 ppm, 24.02 Hz at the above concentration). The same situation is for cyclohexyl-bearing urea, where the first concentration at which the NH signals from urea and CH from modafmil do not overlap is 3.33 mg of modafmil in 0.5 ml of CDCl ₃ (ie 24.4 mM). in comparison to urea bearing hexyl, it does not allow the use of the modafmil NH2 signal at higher concentrations to determine enantiomeric purity. So in this case it is

The concentration above is the highest concentration that is useful for determining the enantiomeric purity of modafmil.

Because best results were obtained with urea 1 carrying 3.55 bis (trifluoromethyl) phenyl residues, this urea was used as a chiral solvating agent (in a 1: 1 molar ratio) for other sulfoxides. For all sulfoxide concentration was 10 mg of the sulfoxide in 0.5 ml CDC1 ₃ except 4-carboxyphenyl (methyl) sulfoxide, which has lower solubility and the starting concentration was 1.48 mg sulfoxide in 0.5 ml CDC1 ₃ (all molar equivalent concentrations are given in the table). The results of the measurements are given in the following 10 table:

Δ δ (ppm) Δδ (Ηζ) 4-methylphenyl (methyl) sulfoxide (c = 129.6mM) 0.014 (CH3-SO--) 0.043 (CH3-phenyl-) 4.00 (CH ₃ -SO-) 12.89 (CH ₃ -phenyl-) 4-nitrophenyl (methyl) sulfoxide (c = 108mM) 0.078 (CH ₃ ) 23.41 (CH ₃₎ 4-hydroxyphenyl (methyl) sulfoxide (c = 128mM) 0.051 (CH3) 15,31 (CH ₃₎ 4-carboxyphenyl (methyl) sulfoxide (c = 16.1 mM) 0.028 (CH ₃ ) 8.42 (CH ₃₎ 4-methoxyphenyl (methyl) sulfoxide (c = 117.5mM) 0.027 (CH3-SO-) 0.013 (CH 3 -O-) 8.08 (CH ₃ -SO-) 3.91 (CH ₃ -O-) 4-fluorophenyl (methyl) sulfoxide (c = 126.4mM) 0.054 (CH ₃ ) 16.30 (CH ₃₎ benzyl (methyl) sulfoxide (c = 129.7) 0.034 (CH ₃ ) 10.02 (CH ₃ ) cyclohexyl (methyl) sulfoxide (c = 136.8mM) 0.101 _(CH3) 30.33 (CH ₃₎ n-butyl (methyl) sulfoxide (c = 166,4mM) 0.104 (CH ₃ -SO-) 31.32 (CH ₃ -SO-) octyl (methyl) sulfoxide (c = 113.4mM) 0.097 (CH ₃ ) 28.98 (CHs) phenyl (tert-butyl) sulfoxide (c = 109.7mM) 0.004 _(CH3) 1.22 (CH ₃ )

The above experiment was performed once more at concentrations of 0.50 mg sulfoxide in

0.5 ml CDC1 ₃ with the following results (all the corresponding molar concentrations are presented in Table 15):

Δδ (ppm) Δδ (Ηζ) 4-methylphenyl (methyl) sulfoxide (c = 6.4mM) 0.015 (CH ₃ -SO-) 0 (CH ₃ -phenyl-) 4.51 (CH ₃ -SO-) 0 (CH ₃ -phenyl-) 4-nitrophenyl (methyl) sulfoxide (c = 5.3mM) 0.023 (CH ₃ ) 7.08 (CH ₃ ) 4-hydroxyphenyl (methyl) sulfoxide (c = 6.3mM) 0.036 (CH ₃ ) 10.77 (CH ₃₎

- 15GB 307419 B6

Δ δ (ppm) Δδ (Ηζ) 4-carboxyphenyl (methyl) sulfoxide (c = 5.4mM) 0.019 _(CH3) 5.87 (CH ₃ ) 4-methoxyphenyl (methyl) sulfoxide (c - 5.8mM) 0.025 (CH ₃ -SO-) 0.017 (CH ₃ -O-) 7.76 (CH ₃ -SO-) 5.11 (CH ₃ -O-) 4-fluorophenyl (methyl) sulfoxide (c = 6.2mM) 0.018 _(CH3) 5.26 (CH ₃₎ benzyl (methyl) sulfoxide (c = 6,4mM) 0.015 _(CH3) 4.31 (CH ₃ ) cyclohexyl (methyl) sulfoxide (c = 6.8mM) 0.064 (CH ₃ ) 19.25 (CH ₃₎ n-butyl (methyl) sulfoxide (c = 8.2mM) 0.069 (CH ₃ -SO-) 17.80 (CH ₃ -SO-) octyl (methyl) sulfoxide (c = 5.6mM) 0.047 (CH ₃ ) 13.46 (CH ₃₎

In the case of 4-methylphenyl (methyl) sulfoxide, the signal of the methyl group on the phenyl at the highest measured concentration was more cleaved than the methyl group next to the sulfoxide group, but with decreasing concentration this split decreased and at 1.11 mg sulfoxide in 0.5 ml.

CDCl 3 (14.4 mM) was no longer visible.

In the case of phenyl (tert-butyl) sulfoxide, the signal cleavage of the methyl groups of tert-butyl was lost at the first dilution to a concentration of 6.67 mg sulfoxide in 0.5 ml CDCl ₃ (i.e. 73.1 mM).

The above experiment was carried out at concentrations of 10 mg of the sulfoxide in 0.5 ml CDC1 ₃ with an amount of urea carrying 3,5-bis (trifluoromethyl) phenyl radicals, which was less than 1 molar equivalent. Already using 5 mole% of the signal splitting visible. The results of this experiment are summarized in the following table (all corresponding molar concentrations are shown in the table):

Δδ (ppm) Δ δ (Hz) 4-methylphenyl (methyl) sulfoxide (c = 129.6mM) 0.005 (CH ₃ -SO-) 0 (CH ₃ -phenyl-) 1.44 (CH ₃ -SO-) 0 (CH ₃ -phenyl-) 4-nitrophenyl (methyl) sulfoxide (c = 108mM) 0.004 _(CH3) 1.24 (CH ₃₎ 4-hydroxyphenyl (methyl) sulfoxide (c = 128mM) 0.003 _(CH3) 0.97 (CH ₃ ) 4-carboxyphenyl (methyl) sulfoxide (c = 16.1mM) 0.004 _(CH3) 1.37 (CH ₃ ) 4-methoxyphenyl (methyl) sulfoxide (c = 117.5 mM) 0.003 (CH ₃ -SO-) 0.004 (CH ₃ -O-) 0.95 (CH ₃ -SO-) 1.29 (CH ₃ -O-) 4-fluorophenyl (methyl) sulfoxide (c = 126.4mM) 0.004 _(CH3) 1.20 (CH ₃ )

- 16GB 307419 B6

Δ δ (ppm) Δ δ (Hz) benzyl (methyl) sulfoxide (c = 129.7mM) 0.002 _(CH3) 0.71 (CH ₃ ) cyclohexyl (methyl) sulfoxide (c = 136.8mM) 0,005 _(CH3) 1.29 (CH ₃ ) n-butyl (methyl) sulfoxide (c = 166,4mM) 0.006 (CH3-SO--) 1.89 (CH ₃ -SO-) octyl (methyl) sulfoxide (c = 113.4mM) 0,007 _(CH3) 1.87 (CH ₃ )

From the above table, it is evident that less than one molar equivalent of urea 1 is sufficient to determine the enantiomeric purity. Therefore, in determining the enantiomeric purity, urea 1 does not need to be accurately weighed prior to addition to the sulfoxide solution, and thus also consumes less urea 1.

Determination of the enantiomeric purity of the modafinil enantiomerically enriched mixtures by measuring NMR spectra in CDC1 ₃ using urea

Four mixtures of Λ-modafinil and S-modafinil were prepared in ratios of approximately 2: 8, 4: 6, 6: 4 and 8: 2 at a concentration of 73.2 mM (i.e. 10 mg sulfoxide in 0.5 ml CDCl 3) for these experiments. After addition of one molar equivalent of urea 1, the enantiomeric purity of the mixtures was read after 1 H-NMR measurement.

The ratio of enantiomers determined by Anmr HPLC enantiomer ratio * 80:20 82:18 43:57 44:56 62: 38 62:38 25: 75 25: 75 * Chiralcel OD column (Daicel); mobile phase hexane: ethanol 9: 1 plus 0.1% CF ₃ COOH; flow rate 0.5 ml / min; detection 254 nm

All of the ureas prepared, specifically bearing hexyl, cyclohexyl, phenyl, 3,5-dimethylphenyl and 3,5-bis (trifluoromethyl) phenyl as substituents, are useful as a chiral solvating agent for determining the enantiomeric purity of sulfoxide by ¹ H-NMR measurement.

Claims (5)

A method for determining the enantiomeric purity of chiral sulfoxides by NMR, comprising adding a compound of formula (I): (l) in which: R represents C 1-6 alkyl optionally substituted by one or more substituents selected from halogen, nitro, cyano, carboxyl, aldehyde, hydroxyl, amino or C 1 -C ₆ alkoxy, _C2 .6 alkenyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl groups, aldehyde groups, hydroxyl groups, amino groups or Ci-Ce alkoxy groups, C ₂ 6 alkynyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl groups, aldehyde groups, hydroxyl groups, amino or Ci-C ₆ alkoxy group, _Io _C3 cycloalkyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl groups, aldehyde groups, hydroxyl groups, amino or C | -CE alkoxy, C ₃ "io cycloalkenyl optionally substituted with one or more substituents selected from halogen, nitro, cyano, carboxyl groups, aldehyde groups, hydroxyl groups, amino groups or _Ci-C6 alkoxy groups or _Io _C6 aryl optionally substituted with one or more substituents selected from C | -C ₆ alkyl optionally substituted with one or more halogen atoms, halogen, nitro, cyano, carboxyl groups, aldehyde groups, hydroxyl groups or C | -C ₆ alkoxy groups in configuring the R- or Sk-solution of the chiral sulfoxide in the deuterated solvent and performing 1 H-NMR analysis. The process of claim 1 wherein R in Formula I is selected from the group consisting of 3,5-bis (fluoromethyl) phenyl, phenyl, 3,5-dimethylphenyl, cyclohexyl and hexyl. - 18 GB 307419 B6 The process according to claim 1 or 2, wherein the deuterated solvent is deuterated chloroform. Process according to any one of claims 1 to 3, characterized in that a molar equivalent of the compound of formula I is added to the chiral sulfoxide 5. Process according to any one of claims 1 to 3, characterized in that less than the molar equivalent of the compound of formula I is added to the chiral sulfoxide.