The present invention relates to processes and intermediates useful in the preparation of of (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol- 3-yl)acetic acid of Formula (la) or salts thereof, an SlPl receptor modulator that is useful in the treatment of SlPl receptor-associated disorders, for example, diseases and disorders mediated by lymphocytes, transplant rejection, autoimmune diseases and disorders, inflammatory diseases and disorders (e.g. , acute and chronic inflammatory conditions), cancer, and conditions characterized by an underlying defect in vascular integrity or that are associated with angiogenesis such as may be pathologic (e.g. , as may occur in inflammation, tumor development and atherosclerosis).

BACKGROUND OF THE INVENTION

SlPl receptor agonists have been shown to possess at least immunosuppressive, antiinflammatory, and/or hemostatic activities, e.g. by virtue of modulating leukocyte trafficking, sequestering lymphocytes in secondary lymphoid tissues, and/or enhancing vascular integrity. Accordingly, SlPl receptor agonists can be useful as immunosuppressive agents for at least autoimmune diseases and disorders, inflammatory diseases and disorders (e.g. , acute and chronic inflammatory conditions), transplant rejection, cancer, and/or conditions that have an underlying defect in vascular integrity or that are associated with angiogenesis such as may be pathologic (e.g., as may occur in inflammation, tumor development, and atherosclerosis) with fewer side effects such as the impairment of immune responses to systemic infection.

The sphingosine-1 -phosphate (SIP) receptors 1-5 constitute a family of G protein- coupled receptors containing a seven-transmembrane domain. These receptors, referred to as SlPl to S1P5 (formerly termed endothelial differentiation gene (EDG) receptor-1, -5, -3, -6, and -8, respectively; Chun et al., Pharmacological Reviews, 54:265-269, 2002), are activated via binding by sphingosine-1 -phosphate, which is produced by the sphingosine kmase-catalyzed phosphorylation of sphingosine. SlPl, S1P4, and S1P5 receptors activate Gi but not Gq, whereas S1P2 and S1P3 receptors activate both Gi and Gq. The S1P3 receptor, but not the SlPl receptor, responds to an agonist with an increase in intracellular calcium.

In view of the growing demand for S 1P1 agonists useful in the treatment of S 1P1 receptor-associated disorders, the compound (R)-2-(7-(4-cyclopentyl-3- (trifluoromethyl)benzyloxy)-l ,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid of Formula

(la):

has emerged as an important new compound, see PCT patent application, Serial No.

PCTVUS2009/004265 hereby incorporated by reference in its entirety. Accordingly, new and efficient routes leading to (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l, 2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid of Formula (la), salts, and intermediates related thereto are needed. The processes and compounds described herein help meet these and other needs.

Example 7: Preparation of (i?)-2-(7-(4-Cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)) and L-Arginine Salt of (_JR)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)).

Method 1

Preparation of (/?)-2-(7-(4-Cyclopentyl-3-(trifluoromethyl)benzyloxy)-l ,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)) and L-Arginine Salt Thereof.

Step A: Preparation of (i?)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4- tetrahydrocyclopenta [b] indol-3-yl)acetic acid.

To a solution of rac-ethyl 2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetate (20.00 g, 41.19 mmol) in acetonitrile (185 ml) in a 500 mL three-neck RBF equipped with magnetic stir bar, N₂ inlet, thermocouple, and condenser was added potassium phosphate buffer (15 ml, 1.0 M, pH = 7.80) and followed by addition of lipase B, Candida antarctica, immobilized recombinant from yeast (1.0 g, 5865 U/g, 5865 U). The resultant yellow suspension was stirred at about 40 °C under N₂ for 16 hours. To the mixture, 1 M citric acid was added to adjust the pH to 3.96 which was then filtered on a Whatman filter cup. The solids were washed with ACN (3 x 15 mL). The combined filtrate and washings were concentrated at about 30 °C under vacuum to give an orange residue, which was partitioned between EtOAc (60 mL) and brine (60 mL). The layers were separated and the aqueous layer was extracted with EtOAc (2 x 40 mL). The combined organic layers were washed with H₂0 (2 x 80 mL), brine (2 x 80 mL), dried over Na₂S0₄, decanted, and concentrated at 30 °C under vacuum to give an orange oil, which was dried under vacuum at room temperature overnight to give a light orange oil (22.203 g) containing (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l ,2,3,4-tetrahydrocyclopenta|¾]indol-3- yl)acetic acid. The crude was assayed to be 41.41 wt % (9.194 g) with 99.42% ee.

Step B: Preparation of L-Arginine Salt of (i?)-2-(7-(4-Cyclopentyl-3- (trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)).

To the crude (21.837 g) (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid (41.41 %w/w; 9.043 g, 19.77 mmol) containing the (5)-isomer as the ester impurity in a 200 mL round bottom flask was added IPA (150.72 mL). The mixture was heated at 60 °C under N₂ till the oily residue dissolved completely. The resultant orange solution was heated at about 60 °C for 5 min. Seeds of L-arginine salt of (R)-2- (7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3- yl)acetate (362 mg) were added. The seeds were suspended in the orange solution. A 2.27 M aqueous solution of L-arginine (8.709 mL, 3.44 g, 19.77 mmol) pre-warmed to about 60 °C was added into the mixture dropwise over 30 min. A light yellow precipitate formed gradually during the addition. The suspension was stirred for about an additional 30 min. The temperature of the suspension was allowed to drop at about 0.4 °C per minute to room temperature. The mixture was agitated occasionally at room temperature overnight. The suspension was filtered and the cake was washed with IP A (3 6 mL) and EtOAc (3 x 15 mL). The filter cake was dried at room temperature under vacuum overnight to give L-arginine salt of (R)-2-(7-(4- cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetate as a white solid (11.631 g, 44.7%): HPLC 99.38 Area %, 99.6 % ee. TGA, PXRD, PLM, SEM and DSC indicated the solid as a non-solvated, crystalline compound with an average aggregates size of 18.05 microns and a melting point of 202.69 °C.

Ή NMR (400 MHz, DMSO-d₆) δ ppm 1.53-1.80 (m, 8H), 1.81-1.92 (m, 2H), 1.93-2.13 (m, 3H), 2.19 (dd, J= 15.12, 8.18 Hz, 1H), 2.46 (dd, J= 15.12, 6.61 Hz, 1H), 2.57-2.77 (m, 3H), 3.03-3.19 (m, 2H), 3.21-3.35 (m, 2H), 3.39-3.51 (m, 1H), 5.13 (s, 2H), 6.70 (dd, J= 8.75, 2.40 Hz, 1H), 6.93 (d, J= 2.40 Hz, 1H), 7.23 (d, 7= 8.75 Hz, 1H), 7.64 (d, J= 8.08 Hz, 1H), 7.72 (d, 7= 8.08 Hz, 1H), 7.74 (s, 1 H), 7.10-8.70 (br. s, 6H), 10.49 (s, 1H). LCMS m/z calcd for C32H40F3N5O5: 631.69, found: 632.1 (M_salt+H)⁺, 458.3 (100, (M_acid+H)⁺).

Method 2

Preparation of (l?)-2-(7-(4-Cyclopentyl-3-(trifluoromethyl)benzyloxy)-l ,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)).

Additional procedures to prepare (R)-2-(7-(4-Cyclopentyl-3- (1xiiluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)) using other lipases were utilized, for example, the following were shown to hydrolyze rac-ethyl 2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l ,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetate to (R)-2-(7-(4-Cyclopentyl-3- (trifluoromethyl)benzyloxy)-l ,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)). General hydrolysis conditions and % enantiomeric excess (% ee) are shown below for the following enzymes, lipase B Candida Antarctica, lipase Mucor miehei (MML), and P. fluorescens.

5% DMF inP. fluorescens 7.5 30 C 19-20 phosphate Buffer

Free enzyme (i.e., non-immoblized)

Each of the above enzymes provided the desired (R)-2-(7-(4-Cyclopentyl-3- (trifluoromethyl)benzyloxy)-l ,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid (Compound of Formula (la)) with varying degrees of % ee.

Example 8: Preparation of L-Arginine Salt of (l?)-2-(7-(4-Cyclopentyl-3- (trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid.

Method 1

(R)-2-(7-(4-Cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid (174.7 mg, 0.381 mmol) was dissolved in EPA (1.57 mL) and L-arginine (66.4 mg, 0.381 mmol) was added as a solution in water (263 μΕ,). The homogeneous solution was warmed to 40 °C. After 15 min at this temperature, a precipitate had formed. The reaction mixture was warmed to 70 °C causing the precipitate to dissolve. The heat bath was turned off. A precipitate began to form at 40 °C and the reaction mixture was allowed to cool to about 28 °C before collecting the solids by filtration. The solids were washed with 14% water in EPA to give the L-arginine salt of (R)-2-(7-(4-cyclopentyl-3- (1riiluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid (130 mg).

Method 2

Example 8: Preparation of L-Arginine Salt of (i?)-2-(7-(4-Cyclopentyl-3- (trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid.

Step A: Preparation of l-Cyclopentyl-2-(trifluoromethyl)benzene (Compound of Formula (lib)).

To a 50 L three-neck round-bottom flask equipped with a mechanical stirrer, thermocouple, and nitrogen inlet, was added dry THF (35 L) and cooled to 0-5 °C. To the flask was added Iron (III) chloride (2.7 kg, 0.15 eq) portion wise over 30-60 min. and stirred for 15- 30 min. resulting in a clear greenish solution. Under a nitrogen atmosphere in a dry 100 gallon glass lined reactor was added THF (87.5 L) and magnesium turnings (4.05 kg, 1.5 eq), and cooled to 0-5 °C. To the THF and magnesium mixture was added the solution of FeCl₃ in THF at a rate to maintain the internal temperature below 10 °C. To the resulting yellow/green mixture was added TMEDA (15.5 kg, 1.2 eq) at a rate to maintain the internal temperature below 20 °C. The resulting reaction mixture was heated to 40-45 °C for 1 hour and a mixture of 1 bromo-2-

(trifluoromethyl) benzene (25 kg, 1.0 eq) and bromocyclopentane (19.9 kg, 1.2 eq) was added to the reaction mixture at a rate to maintain an internal temperature below 25 °C. The resulting reaction mixture was allowed to stir at room temperature overnight and subsequently cooled to an internal temperature of 0-5 °C. To the resulting mixture was added 6 N HC1 (100 L, 1.5 h) at such a rate as to maintain the internal temperature below 15 °C (caution, very exothermic). After the quench, MTBE (200 L) was added and the reactor contents was stirred for 30 min. The phases were separated and the aqueous layer back extracted with MTBE (75 L). The combined organic layers were washed with H₂0 (50 L), brine (50 L) and dried (MgS0₄). The mixture was filtered through an in-line (1 micron) filter cartridge followed by an additional in-line (0.45 micron) filter cartridge into a clean dry reactor. The solvent was evaporated under vacuum (jacket < 30 °C) and co-evaporated with heptanes (2 x 25 L) to provide a viscous liquid. The viscous liquid was dissolved in heptanes (100 L) and passed through a silica plug (25 kg). The silica plug was eluted with heptanes (TLC, R_f ~ 0.8, silica gel, heptanes) and the fractions containing the product were evaporated to provide the title compound as a yellow liquid, 11.7 kg (49.2%), purity as determined by HPLC was 94.1%. Ή NMR conforms to reference standard.

Step B: Preparation of 4-(Chloromethyl)-l-cyclopentyl-2-(trifluoromethyl)benzene (Compound of Formula (He)).

To a 100 gallon glass lined reactor equipped with a stirrer was added concentrated sulphuric acid (48.6 L) and cooled to an internal temperature between about -5 to -10 °C under an atmosphere of N₂. To the sulfuric acid was added thionyl chloride (26.99 kg, 2 eq) at a rate to maintain the internal temperature below -5 °C. To the resulting mixture 1,3,5-trioxane (15.3 kg, 1.5 eq) was added portion wise at a rate to maintain the internal temperature below -5 °C. After the addition of 1,3,5-trioxane, l-cyclopentyl-2-(trifluoromethyl) benzene (24.0 kg) was added drop wise over a period of approximately 2-3 hours. The reaction mixture was stirred at 0 °C for approximately 3-4 hours, allowed to warm to room temperature overnight and subsequently cooled to an internal temperature of 0-5 °C. To the resulting mixture was added water (316 L) drop wise over a period of approximately 5-6 hours (Note: Very exothermic). After the quench with water, the resulting aqueous mixture was extracted with MTBE (243 L and 123 L). The combined organics were washed with saturated NaHC0₃ (100 L), brine (100 L), water (100 L), brine (100 L), and dried (MgS0₄). The mixture was filtered through an in-line (1 micron) filter cartridge followed by an additional in-line (0.45 micron) filter cartridge into a clean dry reactor. The solvent was evaporated under vacuum (jacket < 30 °C) and further evaporated under vacuum at 35-40 °C. The resulting oil was distilled under high vacuum to provide the title compound as a yellow liquid, 24.8 kg (83%), purity as determined by HPLC was 99.47%. Ή

NMR conforms to reference standard.

Step C: Preparation of Ethyl 2-(2-Morpholinocyclopent-2-enylidene)acetate (Compound of Formula (Kg), Whe

Cyclopentanone (22.00 kg), morpholine (22.88 kg) and cyclohexane (43.78 kg) were charged to a 400 L glass-lined reactor equipped with overhead agitation, jacket temperature control, a nitrogen inlet, and a Dean-Stark trap. The reactor contents were heated to about 85 °C to 95 °C for approximately 26 h while removing water using the Dean-Stark trap. The reaction to form the enamine (i.e., 4-cyclopentenylmorpholine, Compound of Formula (lie) wherein R¹ and R² together with the nitrogen atom form a morpholine ring) is deemed complete when the morpholine amount is verified to be < 3% by GC peak area.

The reactor contents were cooled to about 60 °C and ethyl glyoxalate (Compound of Formula (ΠΤ) wherein R³ is ethyl; 58.74 kg, 50% solution in toluene) was added to the mixture slowly so as to maintain an internal temperature of < 80 °C. The reactor contents were heated to about 85 °C to 95 °C for at least 25 hours while removing water using the Dean-Stark trap. The reaction was deemed complete when the eneamine (i.e., 4-cyclopentenylmorpholine) amount by GC was verified to be less than 0.5% by GC peak area. The cyclohexane/toluene mixture was distilled under vacuum, ethanol (261.80kg) was charged to the reactor, and the resulting solution was again distilled under vacuum. Ethanol (34.76 kg) and water 44.00 kg) were charged to the reactor and the reactor contents stirred at 25 °C. The mixture was stirred further for 6 h at about 0-5 °C.

The resulting product slurry was collected by filtration, washed with aqueous ethanol (34.76 kg ethanol dissolved in 176.00 kg water). The filter-cake was further washed with water (110.00 kg), dried initially at approximately 36 °C for 1 hour under vacuum and subsequently at approximately 50 °C under vacuum for 17 h. The title compound was obtained as a tan solid (23.48 kg, 37.8% yield).

Step D: Preparation of Ζί/ZEthyl 2-(7-(Benzyloxy)-l,2-dihydrocyclopenta[b]indol- 3(4H)-ylidene)acetate

To a 400 L glass-lined reactor equipped with overhead agitation, jacket temperature control, and a nitrogen inlet was added (4-(benzyloxy)phenyl)hydrazine hydrochloride (21.08 kg, 1.000 mole equiv.), ethyl 2-(2-mo holinocyclopent-2-en lidene)acetate (22.02 kg, 1.104 mole equiv.), ethanol (51.2 kg, 2.429 mass equiv.), and acetic acid (36.8 kg, 1.746 mass eq.). After the reactor contents are allowed to stand for 10 minutes, agitation and then heating to 60°C to 65°C (60°C target) was started. While stirring at that temperature, samples of the reaction mixture were taken over intervals of approximately 30 minutes and analyzed by HPLC for (4-

(benzyloxy)phenyl)hydrazine, ethyl 2-(2-morpholinocyclopent-2-enylidene)acetate, and hydrazone content. When (4-(benzyloxy)phenyl)hydrazine HPLC % area was < 1, TFA (11.6 kg, 101.7 mol, 1.200 mole equiv., 0.550 mass equiv.) was charged over approximately 1 hour while the stirred reaction mixture was maintained at 60°C ± 5°C with reactor jacket cooling. As stirring at 60°C to 65°C was continued, the hydrazone and imine content of the reaction mixture was monitored by HPLC. After stirring at 60°C to 65°C for at least 12 hours the imine content of the reaction mixture was < 5% area by HPLC, and the stirred reaction mixture was cooled to 20°C to 25°C over approximately 3 hours. Stirring was maintained at that temperature to allow isomerization of the Z isomer to the desired E isomer. The E isomer crystallizes from the reaction mixture. The Z isomer and E isomer % area content of the reaction mixture was monitored by HPLC during this period of stirring at 20°C to 25°C, which was continued until the Z-isomer content of the reaction mixture was < 15% area by HPLC.

The stirred reaction mixture was cooled (0°C to 5°C) over at least 2 hours and then filtered. The reactor was charged with ethanol (27.4 kg, 1.300 mass equiv.), which was stirred and chilled to 0°C to 5°C and then used in two approximately equal portions to slurry-wash the product filter cake twice. The reactor was charged with ethanol (13.8 kg, 0.655 mass equiv.), which was stirred and chilled to 0°C to 5°C and then used to wash the product filter cake by displacement. The reactor was charged with USP purified water (100 kg, 4.744 mass equiv.), and the temperature was adjusted to 20°C to 25°C. The USP purified water was then used in three approximately equal portions to wash the product filter cake three times, the first two by reslurrying and the third by displacement. The reactor was charged with ethanol (16.4 kg, 0.778 mass equiv.), stirred and chilled to 0°C to 5°C, and then used to wash the product filter cake by displacement. The washed product filter cake was dried under full vacuum first with a jacket temperature of 35°C for 1 hour and then with a jacket temperature of 50°C. While drying continues with a jacket temperature of 50°C, the product solids are turned over every 1 hour to 3 hours, and product samples are analyzed for loss on drying (LOD) every >4 hours. When LOD was < 1%, the product was cooled to < 30°C. The yield of the title compound was 13.06 kg (37.59 mol, 44.7%). Step E: Preparation of Ethyl 2-(7-Hydroxy-l,2,3,4-tetrahydrocyclopenta[b]indol-3- yl)acetate.

To a 200 liter Hastelloy reactor was added ethyl 2-(7-(benzyloxy)-l ,2- dihydrocyclopenta[b]indol-3(4H)-ylidene)acetate (E/Z mixture, 12 kg), 10% Pd/C (50% wet with H₂0; 1.80 kg) and ethyl acetate (108 kg). The suspension was degassed 3x with N₂ and triethylamine (1.76 kg) was added. To the resulting mixture was added formic acid (3.34 kg) while maintaining the internal temperature at below 35 °C. The reaction progression was followed by HPLC to monitor the complete consumption of starting material (i.e., E/Z mixture of ethyl 2-(7-(benzyloxy)-l ,2-dihydrocyclopenta[b]indol-3(4H)-ylidene)acetate) and the debenzylated intermediate. After approximately 30 minutes an additional amount of formic acid (0.50 kg) was added and the combined peak area of ethyl 2-(7-(benzyloxy)-l ,2- dihydrocyclopenta[b]indol-3(4H)-ylidene)acetate and the related debenzylated intermediate was determined to be < 1 % area by HPLC. The reactor contents were filtered through a 1.2 μιη cartridge filter followed by an in-line 0.2 μπι inline polishing filter. To the filtrate was added water (60 kg) and the biphasic mixture was partitioned. The organics were separated and concentrated under vacuum at approximately 60°C ± 5°C to a minimum stir volume, ethyl acetate (21.6 kg) was added and the mixture was further concentrated under vacuum to a minimum stir volume. Once again ethyl acetate (16.8 kg) was charged to the crude mixture and the resulting solution was heated to approximately 60 °C. Heptanes (37.2 kg) were charged maintaining the internal temperature at 60 °C. The solution was slowly cooled to approximately 0 to 5 °C and approximately 2-3 hr to facilitate crystallization. The slurry was filtered, the filter cake was reslurried in heptanes (27.12 kg) and ethyl acetate (7.08 kg). The resulting suspension was filtered and the solids dried under vacuum at approximately 40 ± 5 °C (until the loss on drying (LOD) is < 1%) to afford the title compound (6.23 kg, 70.3 % yield) as a solid.

Step F: Preparation of ( ft^-Ethyl 2-(7-(4-Cyclopentyl-3- (trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetate (Compound of Formula (Ilk), Wher

To a 50 liter glass reactor containing ethyl 2-(7 -hydroxy- 1 ,2,3, 4- tetrahydrocyclopenta[b]indol-3-yl)acetate (2.000 kg, 1.000 equiv.) was added cesium carbonate

(3.266 kg, 1.300 equiv.) and acetonitrile (15.720 kg) under nitrogen. To the resulting mixture was added 4-(chloromethyl)-l-cyclopentyl-2-(trifluoromethyl)benzene (2.228 kg, 1.100 equiv.) over approximately one hour while maintaining the stirred reactor contents at 40°C ± 5°C. After the addition of 4-(chloromethyl)-l-cyclopentyl-2-(trifluoromethyl)benzene the reactor contents were heated to 65°C ± 5°C with stirring until the concentration of ethyl 2-(7-hydroxy-l , 2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetate in the reaction mixture was less than 2.0 % area by

HPLC. The reaction mixture was cooled to 50°C ± 5°C and filtered under nitrogen through a fine filter cloth with suction to remove cesium salts (Note: ethyl 2-(7-(4-cyclopentyl-3-

(trifluoromethyl)benzyloxy)-l ,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetate may precipitate below 30 °C). The filter cake was washed with fresh hot (50°C ± 5 °C) acetonitrile (5.658 kg divided in approximately three equal portions). The filtrates were returned to the reactor. The combined filtrates were concentrated by vacuum distillation with a jacket temperature of 60°C ± 10°C. To the reactor was added ethyl alcohol (3.156 kg) and once again concentrated with stirring by vacuum distillation with a jacket temperature of 60°C ± 10 °C. Once again, ethyl alcohol (3.156 kg) was added to the reactor and the contents were concentrated by vacuum distillation with a jacket temperature of 60 °C ± 10 °C to a reactor volume of approximately 14 L. The stirred reactor contents were cooled to 0 °C ± 5°C and the temperature maintained for 4 hours to facilitate the crystallization of the product. The resulting slurry was filtered. The filter cake was washed with cold 0 °C ± 5 °C ethyl alcohol (2 x 3.156 kg). The filter cake was dried under vacuum at 35 °C ± 5 °C until the weight loss over >1 hour was <2% to provide 3.0943 kg (81.0% yield) of the title compound as a solid.

Step G: Preparation of (!?)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)- l,2,3,4-tetrahydrocyclo

A 1.0 M buffer solution was prepared containing potassium phosphate monobasic (29.1 g, 0.0335 equiv.) in USP purified water (213 g) and potassium phosphate dibasic (368.2 g, 0.331 equiv.) in USP purified water (2.107 g). To a 50 liter glass reactor was added ethyl 2-(7-(4- cyclopentyl-3-(trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetate

(3.094 kg, 1.000 equiv.), Lipase B, Candida antarctica, immobilized (88.18 g, 293250 units/kg of ethyl ester starting material) and acetonitrile (22.32 kg). To the stirred contents of the reactor was added the previously prepared 1.0 M potassium phosphate buffer. The resulting mixture was stirred under nitrogen at a temperature of 40°C ± 5°C until the (R)-2-(7-(4-cyclopentyl-3-

(rrifluoromethyl)benzyloxy)-l ,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid concentration was >35% area as determined by HPLC (Note: although the reaction usually is complete after about 10 hours, the reaction mixture may be held at 40°C ± 5°C overnight). The stirred reactor contents were cooled to 25 °C ± 5°C and the pH was adjusted to between 4 and 5 by addition of a solution of citric acid (278.5 g, 0.228 equiv.) dissolved in USP purified water (1.454 kg). The reactor contents were filtered to remove immobilized lipase and phosphate and citrate salts. The reactor and solids were washed with acetonitrile (4.827 kg) and the combined filtrates were added backed into the reactor. The stirred reactor contents were concentrated to a volume of 1.0 L to 2.0 L by vacuum distillation at a jacket temperature of 55 °C ± 5°C. To the reactor was added ethyl acetate (5.582 kg) and USP purified water (6.188 kg). The contents were stirred at 20°C ± 5°C for at least 10 minutes and a solution of sodium chloride (1 kg) in USP purified water (1 kg) was added to facilitate phase separation. After phase separation was complete, the lower aqueous layer was drained. A solution of sodium chloride (5.569 kg) in USP purified water (12.38 kg) was divided in two approximately equal portions and the ethyl acetate phase was washed (2x). The ethyl acetate phase was transferred into a carboy and the reactor was rinsed with ethyl acetate (838.5 g) and added to the carboy containing the ethyl acetate phase. The reactor was washed sequentially with USP purified water (12.38 kg), acetone (4.907 kg), and ethyl acetate (838.5 g) and the ethyl acetate mixture from the carboy was transferred back to the reactor and concentrated with stirring to a volume of 1 L to 2 L by vacuum distillation at a jacket temperature of 55°C ± 5°C. To the reactor was added 2-propanol (14.67 kg) and after stirring the resulting mixture was concentrated to a volume of 1 L to 2 L by vacuum distillation at a jacket temperature of 55°C ± 5°C. To the reactor was added 2-propanol (7.333 kg) and heated with stirring at 60°C ± 5°C until the contents dissolved. The stirred reactor contents were cooled to 20°C ± 5°C and filtered through a medium-porosity fritted-glass filter to remove any inorganic solids to provide a 2-propanol solution containing 1.3188 kg of the title compound.

Step H: Preparation of L-Arginine Salt of (i?)-2-(7-(4-Cyclopentyl-3- (trifluoromethyl)benzyloxy)-l ,2,3_?4-tetrahydrocyclopenta [b] indol-3-yl)acetic acid

(Compound of For

To a 50 liter glass reactor containing the 2-propanol solution prepared in Step G of (R)- 2-(7-(4-cyclopen1yl-3-(trifluoromethyl)ben2yloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3- yl)acetic acid (1.3188 kg, 1.000 equiv.) was added an additional amount of 2-propanol (6.3389 kg) to adjust the total volume to approximately 16.7 L/kg of (R)-2-(7-(4-cyclopentyl-3- (trifluoromethyl)benzyloxy)-l,2,3,4-tetrahydrocyclopenta[b]indol-3-yl)acetic acid. The reactor contents were stirred and heated to 60 °C ± 5 °C. To the reactor was added seed material (L- arginine salt of (R)-2-(7-(4-cyclopentyl-3-(trifluoromethyl)benzyloxy)-l , 2,3,4- tetrahydrocyclopenta[b]indol-3-yl)acetic acid, 26.4 g, 0.0145 equiv.). The reactor contents were stirred for approximately 5 minutes at 60 °C ± 5 °C and a solution of L-arginine (502.5 g, 1.000 equiv.) in USP purified water (1.27 kg) preheated to 60°C ± 5°C was added over approximately

1 hour while maintaining the stirred reactor contents at 60°C ± 5°C. The stirring of the reactor contents at 60°C ± 5°C was maintained for approximately 1 hour and then allowed to cool at an approximate rate of 0.2°C/min to 1.0°C/min. to a temperature of 25°C ± 5°C. Once at approximately 25°C the contents of the reactor were stirred for approximately 1 hour maintaining the temperature of 25°C ± 5°C. The resulting slurry was filtered and the filter cake was washed with 2- propanol (6.2511 kg divided in three approximately equal portions) and with ethyl acetate (13.560 kg divided in six approximately equal portions. The filter cake was dried under vacuum at 40°C ± 5°C (until the weight loss over >1 hour is <2%) to provide 1.657 kg of the title compound (32.9% yield) as a crystalline solid.

HPLC purity: 99.64 Area %; Enantiomeric purity: 99.3%; DSC melting onset temperature 203.46 °C; TGA Weight Loss out to ~1 10 °C was 0.05%. NMR confirms the structure of the L-salt.

Five additional lots of the L-arg salt have been prepared using substantially this same synthetic method as described above, the DSC melting onset temperatures for a sample from each of the lots is as follows: 203.96 °C, 203.00 °C, 203.11 °C, 203.79 °C and 203.97 °C; the TGA Weight Loss out to ~1 10 °C for a sample from each of the lots is as follows: 0.04%, 0.04%, 0.03%, 0.10%, and 0.12%.