WO2013189920A1

WO2013189920A1 - New compound based on cinchona alkaloïds for use in asymmetric michael addition

Info

Publication number: WO2013189920A1
Application number: PCT/EP2013/062605
Authority: WO
Inventors: Célal ATES; Alain Merschaert; Eugene SIEW
Original assignee: Ucb Pharma S.A.
Priority date: 2012-06-19
Filing date: 2013-06-18
Publication date: 2013-12-27

Abstract

The present invention relates to compound of formula (1) and its use as a catalyst in the asymmetric Michael addition reactions.

Description

New compound based on Cinchona Alkaloids for use in asymmetric Michael addition

It is a known fact that enantiomerically pure chemical entities can be key Active Pharmaceutical Ingredients (API) in the pharmaceutical industry. The reason for this is that such enantiomerically pure API's have often a better potency, efficacy and less side effects than if they are included in the corresponding racemic mixture.

Whilst they are often obtained via resolution of the corresponding racemic mixture, implementing such resolution process in large scale manufacturing of these enantiomerically pure API's may have some drawbacks. For example, the non-desired enantiomer generally needs to be eliminated from the reaction media and/or costly equipments are needed.

There is therefore an increasing need to develop new processes of manufacture of chemical Active Pharmaceutical Ingredients (API) which are enantioselective. A number of enantioselective reactions are described in the literature. One of the most powerful functional bond-forming reaction which allows the construction of enantioselective highly functional carbon skeletons is the Michael Addition.

Such reaction can involve the use of organocatalysts amongst which organocatalysts based on Cinchona alkaloids have been reported in international patent application WO 2005/121 1 137 to achieve excellent performances. Unfortunately, the use of such catalysts is generally limited to small scale synthesis in part due to the large amounts of catalyst loading required (2-20%) and the challenges in recycling the catalyst.

Hence there is a need to develop new organocatalysts which could be used, for example in the Michael Addition reaction, and that could also be implemented in large scale manufacturing. This would therefore allow the use of this type of reaction in large scale manufacturing of enantiomerically pure compounds.

In one aspect, the present invention relates to compound of formula 1 , 4,4',4"-[benzene-

1 ,3,5-triyltris(methanediyloxy{(S)-[(2R)-5-ethenyl-1-azabicyclo[2.2.2]oct-2- yl]methanediyl})]triquinolin-6-ol.

1

Compound of formula 1 according to the invention comprises three Cinchona alkaloid based moieties, i.e. o-desmethylquinidine 3, which are linked to a central molecule (herein after referred to as an "anchor molecule"), in this case a 1 ,3,5- tris(methyl)benzene, via o-alkylation.

Cinchona alkaloid based compounds have been used as catalysts in a variety of phase-transfer catalytic reactions and have proven to be extremely efficient as described by Sang-Sup Jew et al. in Chemical Communications, 2009, 7090-7103.

Hyeung-geun Park et al., in Tetrahedron Letters 42 (2001 ) 4645-4648, have also described catalysts comprising three Cinchona alkaloid moieties linked to an anchor molecule by N-alkylation. The catalysts have been shown as being useful in phase- transfer alkylation of imines.

Compound 1 can be obtained by reacting commercially available quinidine 2, (S)- [(2R)-5-ethenyl-1-azabicyclo[2.2.2]oct-2-yl](6-methoxyquinolin-4-yl)methanol, with sodium hydride, thereby affording deprotonated quinidine 2a, which itself reacts with 1 ,3,5- tris(bromomethyl)benzene 4 followed by reaction with sodium ethanethiolate to give compound of formula 1 as shown in the following scheme 1.

Scheme 1 Compound of formula 1 according to the present invention is particularly useful as a catalyst.

The term "catalyst" as used herein means, when referring to a particular chemical reaction, a substance, usually used in small amounts relative to the reactants, that modifies and increases the rate of a reaction without being consumed in the process.

Compound of formula 1 is particularly useful as a catalyst in the asymmetric

Michael addition of dimethyl malonate to compounds of formula 5 to afford compounds of formula 6, both wherein R is aryl or heteroaryl, as shown in the following scheme.

solvent, dimethyl malonate

Catalyst

Scheme 2

The term "aryl" as used herein, refers to an unsaturated aromatic carbocyclic group of from 4 to 14 carbon atoms having a single ring (e.g. phenyl) or multiple condensed rings (e.g. naphthyl). The "aryl" groups may be unsubstituted or substituted by 1 to 4 substituents independently selected from halogen, C 1.4 alkyl or C1.4 alkoxy as defined herein. Preferred aryl groups according to the present invention are phenyl, para- fluorophenyl, para-tolyl and para-nitrophenyl. The term "heteroaryl" as used herein represents an aryl group as defined here above wherein one or more of the carbon atoms have been replaced by one or more heteroatoms selected from O, S or N. Example of heteroaryl according to the present invention is furyl.

Examples of solvents used according to the present invention are ethers, for example tetrahydrofuran (THF), alcohols, for example methanol, dichloromethane and dimethylformamide (DMF). Preferred solvent is THF.

Generally, an excess of dimethylmalonate, for example about 3 molar equivalents with respect to the alkenyl, are necessary to achieve total conversion of the nitro aryl or heteroaryl alkenyl 5 within a reasonable timeframe.

Reaction according to Scheme 2 is generally performed at a temperature comprised between about -40^°C and about 0^°C, preferably at a temperature of about - 20°C.

Compound of formula 6 according to the present invention are obtained with an enantiomeric excess of at least about 90%.

It will be apparent to the person skilled in the art that specific values of enantiomeric excess vary depending on the R substituent. For example, an enantiomeric excess of about 96% is obtained when R is furyl.

The term "enantioselectivity" as used herein refers to the preferential formation in a chemical reaction of one enantiomer over the other and is quantitatively expressed by the "enantiomeric excess".

The term "enantiomeric excess" as used herein refers to the amount of an enantiomer with respect to another. It can be calculated as follows:

% ee = [( [A] - [B] ) : ( [A] + [B] )] x 100,

where [A] is the concentration of one of the enantiomers, and [B] is the concentration of the other enantiomer. A 100% ee means that there is a single enantiomer and in this case the optical purity of the compound will be 100%. The concentration of each of the enantiomers is, of course, expressed on the same basis, and can be expressed on either a weight or molar basis because the enantiomers have the same molecular weight.

International patent application WO 2005/121 137 describes the synthesis and use in asymmetric Michael and aldol additions of bifunctional C/ncfrona-alkaloid-based catalysts such as o-desmethyl quinidine 3, 4-[(S)-[(2R)-5-ethenyl-1-azabicyclo[2.2.2]oct-2- yl](hydroxy)methyl]quinolin-6-ol.

Li Deng et al. in J. Am. Chem. Soc. 2004, 126, 9906-9907 describe the enantioselective asymmetric 1 ,4 addition of dimethylmalonate to trans-p-nitrostyrene, in the presence of O-desmethyl quinidine and other derivatives of quinidine 2 or quinine.

We have surprisingly shown that the Michael addition of dimethyl malonate to trans-p-nitrostyrene 5a (compound of formula 5, wherein R is phenyl), in THF , in the presence of a catalytic amount of compound of formula 1 , affords corresponding compound 6a, (-)-methyl 2 carbomethoxy-4-nitro-3-phenyl-butyrate, with an enantiomeric excess which is at least about 7% greater than with a catalytic amount of o-desmethyl quinidine 3, and about 75% greater than with a catalytic amount of quinidine 2, under the same reaction conditions.

This suggests that the increased rigidity of compound 1 with respect to quinidine 2 and O-desmethylquinidine 3, combined with the presence of free hydroxyl groups on the catalyst is key for the enantioselectivity.

Scheme 3

We have also shown that some functional features of the compound itself are key to achieve the reaction and/or obtain the desired enantiomeric excess.

Compounds of formula 7, 4,4',4"-[benzene-1 ,3,5-triyltris(methanediyloxy{(S)-[(2R)- 5-ethenyl-1 -azabicyclo[2.2.2]oct-2-yl]methanediyl})]tris(6-methoxyquinoline), and 8, (2R,2'R,2"R)-1 , 1 ', 1 "-(benzene-1 ,3,5-triyltrimethanediyl)tris{5-ethenyl-2-[(S)-hydroxy(6- methoxyquinolin-4-yl)methyl]-1-azoniabicyclo[2.2.2]octane} tribromide, shown in Scheme 4, have been prepared and their use as catalysts in the above reaction has been compared with use of compound of formula 1. Compound of formula 7 is structurally substantially similar to compound of formula 1 and can be prepared in a substantially similar manner by O-alkylation of 1 ,3,5- tris(bromomethyl)benzene with quinidine 2, in the presence of a base.

Compound of formula 8 is prepared by N-alkylation of quinidine 2 with 1 ,3,5- tris(bromomethyl)benzene.

Scheme 4

We have surprisingly shown that when performing the reaction according to Scheme 3, compound of formula 1 allows obtention of compound of formula 6a with an increased enantiomeric excess (ee = 93%) compared to the same reaction performed in the presence of compound of formula 7 (ee = 7%).

We have also shown that compound of formula 8 has no effect on the Michael addition according to the present invention.

Therefore, compound of formula 1 is unique in its structure and its effect in the catalysis of the 1 ,4-Michael addition of dimethyl malonate to frans-p-nitrostyrene 5a.

Hence, in a further aspect, the present invention relates to the use of compound of formula 1 as a catalyst in the Michael addition of dimethyl malonate to nitro aryl or NITRO heteroaryl alkenyls 5.

In particular, the present invention relates to a process of manufacture of compound of formula 6 which process comprises reacting compound of formula 5 with dimethyl malonate, in the presence of catalytic amounts of compound of formula 1 , in a solvent at a temperature comprised between -40^°C and 0^°C. In a particular embodiment, the present invention relates to a process of manufacture of compound of formula 6a (compound of formula 6 wherein R is phenyl), comprising reaction trans-p-styrene 5a with dimethylmalonate in tetrahydrofuran at a temperature of about -20°C, in the presence of a catalytic amount of compound of formula 1.

Generally, more than 1 molar equivalent of dimethylmalonate with respect to trans- β-nitrostyrene are necessary to achieve the total conversion of frans-p-nitrostyrene.

Preferably, the process according to the present invention is performed with about 3 molar equivalents of dimethylmalonate.

Generally between about 3 and about 10 mol% of compound of formula 1 with respect to frans-p-nitrostyrene are used. Preferably about 3.33 mol% of compound of formula 1 with respect to frans-p-nitrostyrene are used.

In addition to providing an improved enantioselectivity as set out above, compound of formula 1 has the advantage that it can be recycled and therefore reused in a further reaction.

A number of catalyst recycling strategies are possible, including supporting the catalyst on a solid phase, supporting the catalyst on a polymeric anchor so that it can be precipitated and retaining the catalyst using a membrane.

Amongst these techniques, membrane filtration, and in particular membrane nanofiltration, has both the advantages of preserving elevated catalytic activity/availability, as the catalyst is homogeneously supported, and the simplicity to be implemented in a continuous production scheme, due to the absence of phase changes required when recycling the catalyst. Furthermore membrane filtration separates solutes based on their hydrodynamic sizes, which are a function of the solutes' molecular weights, charges and affinities with the solvent.

Dijkstra et al. in Accounts Chemical Research, vol. 35, n°9, 2002, 798-810, describe various membrane filtration techniques, including membrane nanofiltration, and its application in various chemical reactions.

In a further embodiment according to the present invention, the product obtained as a results of the Michael addition described here above in Scheme 2 and Scheme 3 is recycled according to the setup of Figure 1. This is particularly advantageous as generally it is difficult to separate homogeneous catalysts from the product of reaction at the end of the reaction, which is one of the major drawbacks of the use of homogenous catalysts in large-scale manufacturing.

In one particular embodiment, a batch diafiltration process was developed to separate the desired product 6 from compound of formula 1. Compound of formula 1 in a solution of THF is retained by asymmetric crosslinked polyimide membranes resistant to THF with a molecular weight cutoff, referred to as MWCO, ranging from 150-900 Daltons. Example of such membranes are DuraMem® 500 membrane coupon commercially available at EVONIK-MET.

Figure 1 shows the setup for such diafiltration process and can be described as follows.

Nitrogen gas is used to pressurise the fluid held in the M1 retentate tank (RT1 ) at a pressure comprised between about 18 Barg and 20 Barg. This pressure drives filtration through the DuraMem® 500 membrane held in the M1 membrane unit. The recirculating pump prevent membrane fouling in M1. The catalyst is retained in solution in the M1 retentate tank (RT1 ) by the membrane while the product and reagent are flushed through with the permeate from M1. This permeate is sent to M2, which holds a tighter DuraMem® 300 membrane, that produces a pure solvent stream as its permeate and a concentrated solution of the product and reagent as the retentate when placed under a pressure of about 15 Barg. The pure solvent stream is sent back to T1 to be reused (recycled) in M1. T1 and T2 are buffer tanks which facilitate movement of fluids in the process. The dotted lines denote control loops used to maintain the levels in T1 , T2 and RT1 by controlling the corresponding pumps.

"Barg" as used herein represents the unity for the measured pressure with reference to atmospheric pressure i.e. pressure (Barg) = measure pressure (Bar) - atmospheric pressure (Bar).

The following acronyms are further used in Figure 1 : LC means Level Controller; PRV means Pressure Relief Valve; PI means Pressure Indicator; Tl means Temperature Indicator; RCP means Recirculating Pump.

Retention of a compound in the membrane and hence, separation/rejection of the product, is generally measured by the following formula: /, permeate

R, = 1 - _

/, retentate

Wherein,

Rj is the retention of solute / on the membrane.

Cj, permeate '^{s tne} concentration of solute / in the permeate .

Cj retentate '^{s tne} concentration of solute / in the retentate

The closer the retention is to 1 the better the compound, in particular the catalyst, is retained on the membrane and therefore the better the separation between the compound, in particular the catalyst, and the product is.

Retention of compound of formula 1 according to the present invention is about 1 , for example about 0.97. The retention of compounds of formula 2, 3, 7 and 8 was also measured.

Whereas compound of formula 8 has a retention of about 1 , it does not allow the reaction to proceed as set out here above in the specification.

Hence only compound of formula 1 advantageously combines the features of catalysing the Michael addition as set out hereabove in the specification with the possibility of being retained by the membrane, and thus being recycled.

Retention of compound 7, quinidine 2 and o-desmethyl quinidine 3, which catalyse the Michael addition set out above with a lower enantioselectivity, i.e. lower enantiomeric excess, than compound of formula 1 , have much lower retentions of respectively about 0.54, about 0.37 and about 0.40.

Furthermore, compound of formula 1 according to the present invention is resilient despite the long filtration process. Comparison of reactions performed using fresh catalyst with those performed using recycled catalyst shows that activity of the catalyst is largely unchanged and that the enantiomeric excess is preserved.

Hence, compound of formula 1 according to the present invention has major advantages over substantially similar catalysts described in the literature: it provides a high degree of enantioselectivity of the reaction in which it is used, in particular the Michael addition as set out here above in the specification, combined with a good recyclability. Compound of formula 1 therefore ideally combines the features generally encountered separately in homogeneous and heteregenous catalysts.

In a further aspect, the present invention relates to a process of preparation of compound of formula 6 comprising the following steps:

(i) reacting compound of formula 5 with dimethyl malonate, in the presence of catalytic amounts of compound of formula 1 , in a solvent at a temperature comprised between about -40°C and 0°C;.

(ii) on complete conversion of compound of formula 5 under step(i), charging the reaction mixture into a membrane unit employing an asymmetric crosslinked polyimide membrane and flushing compound 6 and dimethyl malonate out with a flow of solvent equivalent to the flow of the permeate stream;

(iii) Separating compound of formula 6 from dimethylmalonate by liquid column chromatography or crystallization or any other method apparent to the person skilled in the art.

Preferred membrane is DuraMem® 500 membrane coupon commercially available at EVONIK-MET.

Compound of formula 1 is generally retained in solution in the retentate by the membrane.

Pressure at which step (ii) is performed is comprised between about 18 Barg and 20 Barg.

In a particular embodiment according to the present invention, it has been shown that by retaining the compound of formula 1 in solution in the retentate using a membrane, increased loading of said compound are possible. This generally cannot be achieved with other homogeneous catalysts which have to be eliminated from the reaction media after the reaction has been performed.

The term "loading" as used herein when referring to a compound/catalyst means the number of moles of compound/catalyst retained in solution in the retentate using the membrane divided by the number of moles of compound of formula 5.

One advantage of the increase in loading is that it allows reduction of the reaction time. For example, it has been shown that when the loading of compound of formula 1 is multiplied by 3, the reaction time of the Michael addition of dimethyl malonate to trans-β- nitro styrene 5 according to the present invention, is divided by 3, while the enantiomeric excess remains substantially unchanged.

Increasing the loading of compound of formula 1 also allows the decrease of the quantity of dimethyl malonate necessary to perform the reaction with about the same conversion of trans-p-nitro styrene, while maintaining the enantiomeric excess and the reaction time to about the same level.

Both these advantages represent an important gain in terms of costs and productivity if such a process is implemented on large scale.

In a further particular embodiment according to the present invention, the batch dialfiltration is coupled with a solvent recovery step downstream by employing a tighter membrane M2.

Compound 1 remains in M1 , where reaction can occur, while the more permeable compound 6 and dimethyl malonate can be flushed out into M2 using for example a stream of THF. A tighter DuraMem® 300 membrane is used downstream in M2 to enrich compound 6 in solution while producing pure THF for recycle in M1.

This additional solvent recovery step is particularly advantageous as it allows the reduction of the solvent consumption by a factor of about 18.

Hence in a further aspect, the present invention relates to a process of preparation of compound of formula 6 comprising the following steps:

(i) reacting compound of formula 5 with dimethyl malonate, in the presence of catalytic amounts of compound of formula 1 , in a solvent at a temperature comprised between about -40°C and 0°C;

on complete conversion of compound of formula 5 under step (i), charging the reaction mixture into a membrane unit employing asymmetric crosslinked polyimide membrane and flushing compound 6 and dimethyl malonate out with a flow of solvent equivalent to the flow of the permeate stream;

(iii) simultaneously, feeding the permeate stream containing compound 6 and dimethylmalonate into a membrane unit employing a tighter asymmetric crosslinked polyimide membrane which retains the compound 6 and dimethylmalonate, producing a stream of recovered solvent which can be reused back in the first membrane unit and a concentrated stream containing only compound 6 and dimethylmalonate;

(iv) separating compound of formula 6 from dimethyl malonate by liquid column chromatography or crystallization or any other method apparent to the skilled in the art.

Preferred asymmetric crosslinked polyimide membrane under step (i) is a DuraMem® 500 and preferred asymmetric crosslinked polyimide membrane under step (iii) is DuraMem® 300, both commercially available from EVONIK-MET. Examples

The following examples are provided for illustrative purposes only and are not intended, nor should they be construed, as limiting the invention in any manner. Those skilled in the art will appreciate that routine variations and modifications of the following examples can be made without exceeding the spirit or scope of the invention.

H and ³C NMR spectra were recorded on a Bruker instrument (both at 400MHz). Data for H NMR was recorded as follow: chemical shift (δ, ppm), multiplicity (s, singlet; d, doublet; t, triplet; q, quartet; m, multiplet), coupling constant (Hz), integration. Data for ³C NMR was reported in terms of chemical shift (δ, ppm). Exact mass spectra were recorded on a Waters Q-TOF.

High pressure liquid chromatography (HPLC) analyses were performed using a Waters Alliance 2695 instrument equipped with a quaternary pump. Reactions were monitored after HPLC separation using a Xbridge C18 column (3.5μηι beads, 4.6 x 50mm) at UV detection at 230nm.

All commercially available solvents and reagents were used as received unless otherwise stated. Preparative thin layer chromatography was performed on PLC Silica gel plates with of 1 mm thickness from Merck. Flash chromatography was performed using Silica Gel 60 from Merck. 1. Preparation of compounds of formula 1 , 3, 7 and 8

1.1. Compound 1-4, 4 ', 4"-f benzene- 1 , 3, 5-triyltris(methanediyloxy{(S) -i(2R)-5- ethenyl-1-azabicvclo[2.2.2loct-2-yllmethanediyl})ltriguinolin-6-ol To a solution of quinidine 2 (10g) in dried DMF (70ml) under nitrogen pressure, NaH (3.4g, 60wt% suspension in mineral oil) was added in small portions. The resulting mixture was stirred at room temperature for 2h. A solution of 1 ,3,5- tris(bromomethyl)benzene (2.75g, 97wt%) in dried DMF (10ml) was slowly added to the mixture using a syringe under stirring. The reaction was quenched with deionized water (200ml) after 19h. Dichloromethane (400ml) was added to the mixture and then washed with deionized water (2 x 200ml). The organic phase was then removed and dried in vacuo yielding 16.6g of a brown oil.

Sodium ethanethiolate (18g, 90wt%) was added to this oil along with dried DMF (180ml) and the mixture was stirred under nitrogen pressure and under reflux (1 10°C). The reaction was left to cool to room temperature after 24h and then quenched with deionized water (180ml). The pH of the mixture was adjusted to 1 using HCI (1 M) and washed with ethyl acetate (2 x 250ml + 100ml). The aqueous layer pH was then adjusted to 8 using ammonium hydroxide and washed with dichloromethane (3 x 250ml). The organic layers were collected and washed with deionized water (2 x 500ml) before drying in vacuo. 4.1g of a dry brown solid was obtained. Isolated yield = 53%.

1 H NMR (400MHz, (CD3)2SO) of 1 : δ 10.20 (br, 1 H), 8.62 (d, J = 4.3Hz, 1 H), 7.92 (dd, J = 3.4Hz, 8.9Hz, 1 H), 7.50 (br, 1 H), 7.39 (s, 1 H), 7.32 (d, J = 9.0Hz, 1 H), 7.20 (d, J =

14.5Hz, 1 H), 5.79-6.00 (m, 1 H), 5.12 (br, 1 H), 4.95 (d, J = 17.0Hz, 1 H), 4.85 (d, J = 10.3Hz, 1 H), 4.33 (dd, J = 6.4Hz, 1 1.8Hz, 2H), 3.16 (br, 1 H), 2.99 (br, 1 H), 2.73 (br, 2H), 2.60 (br, 1 H), 2.1 1-2.27 (m, 1 H), 1.78-2.00 (m, 1 H), 1.67 (br, 1 H), 1.40-1.56 (m, 2H), 1.03-1.38 (m, 1 H); HRMS m/z for (M+3H+) = 349.2, (M + 2H+) = 523.8, (M + H+) = 1045.7

1.2. Compound 7- 4,4'A"-[benzene- 1 , 3, 5-triyltris(methanediyloxy{(SH(2R)-5-ethenyl- 1 -azabicyclo[2.2.21oct-2-yllmethanediyl}) ltris(6-methoxyciuinoline)

To a solution of quinidine 2 (4.0g) in dried DMF (30ml) under nitrogen pressure, NaH (1 -36g, 60wt% suspension in mineral oil) was added in small portions. The mixture was stirred at room temperature for 2h. A solution of 1 ,3,5-tris(bromomethyl)benzene (1.1 g, 97wt%) in dried DMF (10ml) was then slowly added to the mixture using a syringe under stirring. The reaction was quenched with deionized water after 5h.

The pH of the mixture was adjusted to 1 by adding HCI (0.1 M) and washed with n- hexane (300ml). The pH of the aqueous phase was then adjusted to 14 by adding solid NaOH. Ethyl acetate (1 L) was added to dissolve all particulates in the mixture and the aqueous phase removed. The organic phase was washed with 2.5L deionized water. Normal phase preparative chromatography used to purify product on a Kromasil column using a mobile phase containing dichloromethane:methanol (89: 1 1 v/v 1.1 % ammonium hydroxide). Isolated yield 42%.

1 H NMR (400MHz, (CD3)2SO) of 7: δ 8.69 (d, J = 4.1 Hz, 1 H), 7.96 (d, J = 7.9, 1 H),

7.50 (br, 1 H), 7.44 (d, J = 2.6Hz, 6.9Hz, 1 H), 7.40 (dd, J = 2.6Hz, 6.9Hz, 1 H), 7.15 (s, 1 H), 5.88-6.00 (m, 1 H), 5.17 (br, 1 H), 4.95 (d, J = 17.4Hz, 1 H), 4.86 (d, J = 10.4Hz, 1 H), 4.32 (dd, J = 12.7Hz, 23.2Hz, 2H), 3.79-3.85 (m, 3H), 3.03-3.14 (m, 1 H), 2.83- 2.93 (m, 1 H), 2.60-2.70 (m, 1 H), 2.41-2.50 (m, 1 H), 2.10-2.20 (m, 1 H), 2.08(br, 1 H), 1.79-1.89 (m, 1 H), 1.64 (br, 1 H), 1.35-1.59 (m, 3H); HRMS m/z for (M + H+) = 1087.6

1.3. Compound 8- (2R.2'R.2"R)-1.1 '.1 "-(benzene-1.3.5-triyltrimethanediyl)tris{5- ethen yl-2-[( S) -hydroxy ( 6-methoxyauinolin-4-yl) meth yll- 1 - azoniabicyclo[2.2.21octane} tribromide

To a mixture of quinidine 2 (3.3g) and 1 ,3,5-tris(bromomethyl)benzene (1.2g, 97wt%), a solvent mixture of ethanol/DMF/chloroform (30ml 5:6:2 by vol) was added. The mixture was stirred under reflux (100°C) for 18h. The mixture was then cooled to room temperature and ether added to it until the solution turned colourless. A precipitate was filtered off and washed with a solvent mixture of ether/acetone (750ml 1 :2 vol/vol). The precipitate was then dried in vacuo to afford a dry brown powder (2.8g). Isolated yield = 63%

1 H NMR (MHz, (CD3)2SO) of 8: δ 8.85 (d, J = 4.6Hz, 1 H), 8.26 (br, 1 H), 8.06 (d, J = 9.7Hz, 1 H), 7.80-7.84 (m, 1 H), 7.55 (dd, J = 2.1 Hz, 9.7Hz, 1 H), 7.45-7.50 (m, 1 H), 6.75-6.87 (m, 1 H), 6.62 (s, 1 H), 5.97-6.10 (m, 1 H), 5.10-5.19 (m, 2H), 4.81-4.95 (m„ 1 H), 3.69-3.81 (m, 2H), 3.44 (s, 3H), 3.15-3.26 (m, 1 H), 2.89 (s, 2H), 2.31-2.47 (m, 1 H), 2.08 (br, 2H), 1.93 (br, 1 H), 1.65-1.80 (m, 2H), 1.10-1.24 (m, 1 H); HRMS m/z for (M3+) = 363. 1.4. Compounds 2 and 3

Quinidine 2 is commercially available and was purchased from Sigma-Aldrich.

O-desmethylquinidine 3 is prepared according to the procedure described by Li Deng et al. in J. Am. Chem. Soc. 2004, 126, 9906-9907.

2. Michael addition of nitro aryl and heteroaryl alkenyl 5 in the presence of compound 1 solvent, dimethyl malonate

Compound 1

6

Compound 5 (0.4mmol), naphthalene (30mg), compound 1 (3.33mol%) and THF (0.4ml) were placed in a cylindrical tube and stirred using Teflon-coated stir-bars at -20°C for 30min. After that, dimethyl malonate (158mg) was added to start the reaction. The following table summarizes the results obtained with various R substituents. Enantiomeric excess is as defined in the present patent application.

Table 1

Entry R Conversion 24h^a / % Time / day Yield^c / % ee^d / %

1

90.1 3 62 93.5

2

92.5 3 81 93.6

3

76.1 5 62 92.7

4

100 1 88 95.2 Entry R Conversion 24h^a / % Time / day YielcT / % ee^d / %

5

O 93.6 3 92 96.0 a Determined by HPLC analysis under comparison with a naphthalene internal standard after 24h. ^bTotal time taken for the reactions, which were run with 0.4mmol of trans^-nitrostyrene and 3mol eq. of dimethyl malonate at -20°C until compound 5 was consumed as determined by

HPLC analysis at λ = 230nm. ^c Isolated yield of 6. ^ Determined by chiral HPLC analysis.

(-)-Methyl 2 carbomethoxy-4-nitro-3-phenyl-butyrate 6a, Entry 1. This product was obtained as a light yellow oil in 62% yield after flash chromatography (elution gradient: Ethyl acetate / isohexane = ¼ by volume) and 93.5% ee determined by HPLC analysis [Daicel chiralcel OD-H, isohexane: I PA, 70:30, 0.9ml/min, column temperature = 24°C, λ = 220nm, t (minor) = 1 1.7min, t (major) = 13.1 min]

(-)-Methyl 2 carbomethoxy-4-nitro-3-(4-fluoro-phenyl)-butyrate 6b, Entry 2. This product was obtained as a colourless oil in 81 % yield after flash chromatography (elution gradient: Ethyl acetate / iso-hexane = ¼ by volume) and 93.6% ee determined by HPLC analysis [Daicel chiralcel AD-H, isohexane: I PA, 70:30, 1.0ml/min, column temperature = 22°C, λ = 220nm, t (minor) = 12.2min, t (major) = 7.4min] from a reaction catalyzed with compound 1 (3.33mol%) at -20°C for 3 days.

(-)-Methyl 2 carbomethoxy-4-nitro-3-(4-methylphenyl)-butyrate 6c, Entry 3. This product was obtained as an off-white solid in 62% yield after preparative thin layer chromatography (elution gradient: Ethyl acetate / iso-hexane = ¼ by volume, R_f = 0.14) and 92.7% ee determined by HPLC analysis [Daicel chiralcel OD-H, isohexane: I PA, 85:15, 1.0ml/min, column temperature = 18°C, λ = 220nm, t (minor) = 20.0min, t (major) = 22.4min] from a reaction catalyzed with compound 1 (3.33mol%) at -20°C for 5 days.

(-)-Methyl 2 carbomethoxy-4-nitro-3-(4-nitro-phenyl)-butyrate 6d, Entry 4. This product was obtained as a yellow solid in 88% yield after preparative thin layer chromatography (elution gradient: Ethyl acetate / iso-hexane = ¼ by volume, R_f = 0.17) and 95.2% ee determined by HPLC analysis [Daicel chiralcel OD-H, isohexane: I PA, 50:50, 0.9ml/min, column temperature = 28°C, λ = 220nm, t (minor) = 10.3min, t (major) = 15.6min] from a reaction catalyzed with compound 1 (3.33mol%) at -20°C for 1 day; H NMR (400 MHz, CDCI₃) δ 8.23 (dt, J = 2.8Hz, 8.8Hz, 2H), 7.48 (dt, J = 2.7Hz, 8.6Hz, 2H), 4.91-5.02 (m, 2H), 4.35-4.44 (m, 1 H), 3.90 (d, J = 8.8Hz, 1 H), 3.81 (s, 3H), 3.64 (s, 3H); 3C NMR (400MHz, CDCI₃) δ 167.5, 166.7, 147.8, 143.6, 133.3, 132.5, 129.2, 124.2, 77.0, 54.1 , 53.4, 53.1 , 42.7; HRMS m/z (M + NH⁴⁺) = 344

(-)-Methyl 2 carbomethoxy-4-nitro-3-(2-furyl)-butyrate 6e, Entry 5. This product was obtained as a light yellow in 92% yield after preparative thin layer chromatography (elution gradient: Ethyl acetate / iso-hexane = ¼ by volume, R_f = 0.20) and 96.0% ee determined by HPLC analysis [Daicel chiralcel OD-H, isohexane:IPA, 60:40, 1.0ml/min, column temperature = 22°C, λ = 220nm, t (minor) = 6.4min, t (major) = 15.0min] from a reaction catalyzed with compound 1 (3.33mol%) at -20°C for 3 days. Michael addition of trans-B-nitrostyrene 5a to dimethylmalonate in the presence of compound 1, 2, 3, 7 or 8-comparative examples

Trans-3-nitrostyrene 5a (60mg, 0.4mmol), dimethyl malonate (158mg, 1.2mmol), naphthalene (30mg) and the compound 1 , 2, 3, 7 or compound 1 were placed in cylindrical tubes. THF (0.4ml) was then added to each tube and the resulting mixture stirred at -20°C using a Teflon-coated stir bar. The mixtures were sampled every 24h for HPLC analysis at 230nm. The reaction solutions were purified using preparative thin layer chromatography to produce a purified product for chiral analysis.

Table 2

Entry Compound/ Conversion 24h^a / Yield^b /

Loading / mol% ee^c / % Catalyst % %

1 1 3.33 90.1 62 93.5

2 2 10 45.0 52 18.9

3 3 10 98.7 82 86.3

4 7 3.33 40.7 44 6.7

5 8 3.33 No reaction / / ^aDetermined by HPLC analysis under comparison with a naphthalene internal standard after

24h. b Isolated yield for the reactions, which were run with 0.4mmol of trans^-nitrostyrene and 3mol eq. of dimethyl malonate at -20°C until all nitrostyrene was consumed as determined by HPLC analysis at λ = 230nm. ^c Determined by chiral HPLC analysis.

4. Membrane diafiltration and recycling of compound 1

The setup shown in Figure 1 is used. A membrane stage employing a DURAMEM 500 membrane coupon, purchased from Evonik-MET (UK), is used to support the compound 1 in solution in M1. Compound 1 remains in M1 , where reaction occurs, while the more permeable product and dimethyl malonate are flushed out into M2 using a stream of THF. A tighter DURAMEM 300 membrane is used downstream in M2 to enrich compound 6 in solution while producing pure THF for recycle in M1.

The Michael addition reaction is carried out at -20°C in a separate vessel. At the end of the reaction, the solution contains compound 1 , compound 6 and excess dimethyl malonate.

The solution is poured into the membrane unit M1 which comprises a feed tank, a crossflow membrane coupon holder and a circulation pump. The membrane coupon holder and the recirculation pump are key a successful process. The circulation pump recirculates the solution across the membrane in the membrane holder which ensures good liquid mixing in the system. Coupled with the small aperture in the membrane holder which forces high velocity flow across the membrane, sufficient turbulence is generated to prevent fouling of the membrane by both compound 1 and compound 6.

During separation, the system is pressurized using nitrogen to about 20 Barg.

Solvent loss in M1 is balanced by controlled feed of fresh solvent (THF) into M1 supplied using a metering pump. Compound 1 is retained in M1 while compound 6 is flushed out. Retention of compound 1 is compared with retention of compounds 2, 3, 7 and 8 at different pressures. Results are summarized in the following tables 3, 4 and 5. Flux, indicated in the following tables, means the volumetric flow of permeate from membrane divided by the filtration area of the the membrane. Table 3 Retention at 5Bar using DURAMEM 500 and DURAMEM 300 from Evonik-MET with their corresponding fluxes

Table 5 Retention at 18 Bar (unless otherwise stated) using DURAMEM 500 and DURAMEM 300 from Evonik-MET with their corresponding fluxes.

DM500 DM300

Compound/Catalyst

Flux / I m^"2 h^"1 Retention / - Flux / I m^"2 h^"1 Retention / -

Quinidine 2 97.8^a 0.339^a 42.2^b 0.803^b

O-demethylquinidine 3 60.0 0.561 30.6 0.764 DM500 DM300

Compound/Catalyst

Flux / I m^"2 h^"1 Retention / - Flux / I m^"2 h^"1 Retention / -

7 92.2^C 0.714^c 23.0^C 0.906^c

1 20.7 0.979 17.5 1.000

8 51.9 0.982 21.9 1.000

"Performed at 14Bar. Performed at 20Bar. "Performed at 16Bar

5. Solvent recycling

Due to the large solvent requirement for the separation, a solvent recovery procedure was implemented. The permeate from M1 is fed into M2 which holds a tighter DuraMem® 300 membrane at about 15 Barg. Pressure in M2 is controlled using a back pressure regulator. The permeate which is largely pure THF is reused and fed back into M1 , while the retentate from M2 is a concentrated solution containing the pure adduct. 6. Variation in Loading of Compound 1

Procedure described in example 2 is applied to compound of formula 5a. Loading of compound of formula 1 and quantity of dimethylmalonate are varied. Table 6 shows the results obtained. Table 6 Effect of Loading of Compound 1 on reaction performance

^a Determined by HPLC analysis under comparison with a naphthalene internal standard after 24h. Total time taken for the reaction until all nitrostyrene was consumed as determined by HPLC analysis at λ = 230nm. ⁰ Determined by chiral HPLC analysis. ^d 1 mol eq. of dimethyl malonate 7. Effect of recycling of compound 1 on enantiomeric excess

Compound of formula 1 has been recycled according to the procedure described in example 4. The recycled compound is used to perform the Michael addition on compound of formula 5a described in example 2. Results are shown in Table 7 below.

Table 7 Effect of catalyst recycling on reaction performance

Catalyst recycled from diafiltration process Determined by HPLC analysis under comparison with a naphthalene internal standard after 24h. Total time taken for the reaction until all nitrostyrene was consumed as determined by HPLC analysis at λ = 230nm. ⁰ Determined by chiral HPLC analysis.

Claims

A compound of formula 1 for use as a catalyst in the Michael addition of dimethyl malonate to compound of formula 5, wherein R is an aryl or an heteroaryl.

A process of preparation of compound of formula 6 which process comprises reacting compound of formula 5 with dimethyl malonate, in the presence of catalytic amounts of compound of formula 1 , in a solvent at a temperature comprised between -about 40^°C and about 0^°C.

The process according to Claim 3 which further comprises charging the reaction mixture into a membrane unit employing asymmetric crosslinked polyimide membrane and flushing compound 6 and dimethylmalonate out with a flow of solvent equivalent to the flow of the permeate stream.

5. The process according to Claim 4 wherein the compound of formula 1 is retained in solution by DuraMem® 500 membrane.

6. The process according to Claim 5 wherein the Retention of compound of formula 1 in the membrane is about 1.

7. The process according to Claim 4 which further comprises feeding the permeate stream containing compound 6 and dimethylmalonate into another membrane unit employing a tighter asymmetric crosslinked polyimide membrane and recycling the solvent recovered from the permeate stream in the first membrane.

8. The process according to any one of Claim 3 to 7 wherein compound of formula 5 is trans-p-styrene 5a and compound of formula 6 is (-)-Methyl 2 carbomethoxy-4- nitro-3-phenyl-butyrate 6a.

9. The process according to any one of claims 3 to 8 wherein the solvent is tetrahydrofuran (THF).

10. The process according to any one of claims 3 to 9 wherein the temperature is about -20°C.

1 1. The process according to any one of claims 3 to 10 wherein the amount of compound of formula 1 is comprised beween about 3 and about 10 mol%.

12. The process according to the present invention wherein the amount of compound of formula 1 is about 3.33 mol%.