Example 1

3-(4-(5-Methyl-l,3,4-oxadiazol-2-yl)phenoxy)-5-(l-methyl-2-oxopyrrolidin-3- yloxy)-iV-(thiazol-2-yl)benzainide

4-(Dimethylamino)pyridine (DMAP) (0.149 g), N-(3-Dimethylaminopropyl)-N’- ethylcarbodiimide hydrochloride (EDCI.HC1) (0.524 g) were added to a solution of 3-

( 1 -Methoxypropan-2-yloxy)-5-(4-(5 -methyl- 1 ,3,4-oxadiazol-2-yl) phenoxy) benzoic acid (0.5 g) (Intermediate 1) in dry DCM under nitrogen at 0-5 ⁰C. 2-Aminothiazole (0.134 g) was added and the mixture was stirred for 16 h at room temperature. It was diluted with commercially available DCM. Organic phase was washed with dil HCl, saturated solution of NaHCO₃, water, brine, dried over Na₂SO₄, filtered and concentrated in vacuo to get the crude residue. The residue was chromatographed using silica gel as stationary phase and MeOH: CHCl₃ gradient as mobile phase up to yield the product (0.3 g) as a white solid.

¹H NMR (DMSO-<4_, 400 MHz) δ ppm: 1.92-2.01 (m, 1 H), 2.59 (s, 3 H), 2.60-2.65 (m,

I H), 2.79 (s, 3 H), 3.31-3.34 (m, 1 H), 3.36-3.44 (m ,1 H), 5.15 (t, J = 7.6 Hz, 1 H),

7.08 (s, 1 H), 7.24 (d, J= 8.8 Hz, 2 H), 7.27-7.29 (m, 1 H), 7.40 (s, 1 H), 7.54 (s, 1 H),

7.62 (s, 1 H), 7.99 (d, J = 8.8 Hz, 2 H), 12.60 (bs, 1 H); ESI-MS mix (relative intensities): 492.03 (M+H)⁺ (100 %), 514.02 (M+Na)⁺(15 %); UPLC Purity: 93.59 %, Rettime: 3.59 min.

Intermediate 1: 3-(4-(5-Methyl-l,3,4-oxadiazol-2-yl)phenoxy)-5-(l-methyl-2-oxo pyrrolidin -3-yloxy)benzoic acid

A solution of Methyl 3-(4-(5-methyl-l,3,4-oxadiazol-2-yl)phenoxy)-5-(l-methyl- 2-oxopyrrolidin-3-yloxy)benzoate (7 g) (Intermediate 2) in a mixture of THF and methanol (1 :1 ratio) was treated with a solution of sodium hydroxide (2 g) in water and the reaction mixture was stirred for 1 h at room temperature. The resulting solution was concentrated under vacuum to remove THF and methanol, diluted with water, and washed with EtOAc. The aqueous phase was cooled and acidified with 0.1 N HCl and extracted with DCM, combined organic extracts washed with brine, dried over Na₂SO₄ and concentrated in vacuo to give the product (3.5 g) as white solid.

¹H NMR (CDCl_3, 400 MHz) δ ppm: 2.20-2.27 (m, 1 H), 2.59-2.67 (m, 1 H), 2.77 (s, 3 H), 2.95 (s, 3 H), 3.38-3.44 (m, 1 H), 3.49-3.54 (m, 1 H), 4.96 (t, J = 7.2 Hz, 1 H), 6.93-6.95 (m, 1 H), 7.07 (d, J= 8.8 Hz, 2 H), 7.32-7.34 (m, 1 H), 7.52 (d, J= 8.8 Hz, 2 H), 9.96-9.98 (m, 2 H); ESI-MS (relative intensities): 431.9 (M+ Na)⁺ (70%).

Intermediate 2: Methyl 3-(4-(5-methyl-l,3,4-oxadiazol-2-yl)phenoxy)-5-(l-methyl-2- oxo- pyrrolidin-3-yloxy)benzoate

To a stirred mixture of Methyl 3-hydroxy-5-(l-methyl-2-oxopyrrolidin-3-yloxy) benzoate (15 g) (Intermediate 3), N,N-dimethylglycine hydrochloride (2.3 g), copper (II) iodide (1 g) in dry 1,4-dioxane was added 2-(4-iodophenyl)-5 -methyl- 1,3,4- oxadiazole (15.4 g) (Intermediate 4) under nitrogen. The reaction mixture was refluxed for 24 h. The reaction mixture was cooled, quenched with water and extracted with DCM. Combined organic washings were washed with water, brine, dried over Na₂SO₄, filtered and concentrated in vacuo to get the crude product. The crude product was purified by column chromatography using silica gel as stationary phase and ethyl acetate: petroleum ether (9:1) as mobile phase to give the product (7 g) as thick liquid. ¹H NMR (DMSO-<4, 400 MHz) δ ppm: 1.91-1.98 (m, 1 H), 2.49-2.54 (m, 1 H), 2.56 (s, 3 H), 2.77 (s, 3 H), 3.34-3.41 (m, 2 H), 3.81 (s, 3 H), 5.12 (t, J= 7.6 Hz, 1 H), 7.13- 7.15 (m, 2 H), 7.22 (d, J = 8.8 Hz, 2 H), 7.42 (s, 1 H), 7.97 (d, J = 8.8 Hz, 2 H); ESI- MS (relative intensities): 423.9 (M+H)⁺ (100%), 446.2 (M+ Na)⁺ (30%).

Intermediate 3: Methyl 3-hydroxy-5-(l-methyl-2-oxopyrrolidin-3-yloxy)benzoate

To a stirred solution of Methyl 3, 5-dihydroxybenzoate (20 g) [CAS No. 2150- 44-9] in dry DMF was added potassium carbonate (48 g) and the suspension stirred at ambient temperature under nitrogen. To this 3-Bromo-l-methyl-pyrrolidin-2-one (4Og) (Intermediate 5) [J. Med. Chem., 1987, 30, 1995-98] was added in three equal portions in 4 h intervals at room temperature and stirred overnight at ambient temperature. It was then quenched with water. The aqueous suspension was extracted with DCM. The combined extracts were washed with water, brine, dried over Na₂SO₄, and filtered, concentrated under reduced pressure to get the thick liquid residue. The crude product was purified by column chromatography using silica gel as stationary phase and ethyl acetate: petroleum ether as a mobile phase to yield the product as white solid (15 g).¹H NMR (CDCl₃, 400 MHz) δ ppm: 2.08-2.10 (m, 1 H), 2.60-2.67 (m, 1 H), 3.04 (s, 3 H), 3.40-

3.43 (m, 1 H), 3.48-3.51 (m, 1 H), 3.87 (s, 3 H), 4.91 (t, J = 7.2 Hz, 1 H), 6.59- 6.61 (m, 1 H), 7.07-7.09 (m, 1 H), 7.09-7.13 (m, 1 H), 8.02 (s, 1 H); ESI-MS (relative intensities): 287.9 (M+ Na)⁺ (30%).

Example 68…. S CONFIGURATION

(S)-3-(4-(5-Methyl-l,3,4-oxadiazol-2-yI)phenoxy)-5-((l-methyl-2-oxopyrrolidin-3- yl) oxy)-N-(thiazol-2-yl)benzamide

To a stirring solution of S-(-)-3-[4-(5-Methyl-l,3,4-oxadiazol-2-yl)phenoxy]-5- [(l-methyl-2-oxo-pyrrolidin-3-yl)oxy]benzoic acid (3.5 g) (Intermediate 13) in dry DCM in single necked round bottomed flask fitted with stop cock with N_2(g) balloon, 4- (dimethylamino)pyridine (2.24 g) followed by N-(3-Dimethy lam inopropy I)-N⁵– ethylcarbodiimide hydrochloride (EDCI. HCl) (3.3 g) were added at room temperature. After stirring at the same temperature for 15 min, 2-aminothiazole (0.94 g) was added and stirring was continued for 16 h. Progress of reaction was monitored by TLC. After completion, reaction mixture was diluted with DCM (200 mL), washed with dil HCl (20 mL, 0.05 Ν), saturated sodium bicarbonate solution, water and brine, dried over anhydrous sodium sulphate, filtered and concentrated under vacuum to get crude brown solid (3.5 g). The crude brown solid was purified by solvent trituration.

1H ΝMR (CDCl₃, 400 MHz) δ ppm: 2.13-2.22 (m, 1 H), 2.62 (s, 3 H), 2.56-2.64 (m, 1 H), 2.93 (s, 3 H), 3.39-3.43 (m, 1 H), 3.48-3.53 (m ,1 H), 4.92 (t, J= 7.2 Hz, 1 H), 7.01 (s, 1 H), 7.04 (t, J= 2 Hz, 1 H), 7.21 (d, J = 8.8 Hz, 2 H), 7.26 (s, 1 H), 7.36 (s, 1 H), 7.44 (s, 1 H), 7.99 (d, J = 8.8 Hz, 2 H); ESI MS m/z (relative intensities): 492.1 (M+H)⁺ (100 %), 513.8 (M+Νa)⁺ (10 %); UPLC Purity: 98.13 %, Ret. time: 3.577 min. Chiral Purity by HPLC: 97.31 %, Ret. time: 22.93 min. % ee: 94.62 %

Intermediate 13: S-(-)-3-[4-(5-Methyl-l, 3, 4-oxadiazol-2-yl)phenoxy]-5-[(l-methyl-2- oxo-pyrro- lidin-3-yl)oxy] benzoic acid

Sodium hydroxide (pallets, 1.5 g) was added to a stirring mixture of (.S)-(-)-Methyl 3- [4-(5-methyl-l,3,4-oxadiazol-2-yl)phenoxy]-5-[(l-methyl-2-oxo-pyrrolidin-3-yl)oxy] benzoate (5.3g) (Intermediate 14) in MeOH:H₂O (1:1) at room temperature. The reaction was monitored by TLC. After completion, methanol was evaporated from the reaction mixture and water was added. The aqueous layer was washed with EtOAc, acidified with dil. HCl (0.05 N) to obtain solid. The solid obtained was filtered, washed with water, dried under suction or vacuum to get pure white solid (3.5 g).

1H NMR (CDCl₃, 400 MHz) δ ppm: 2.17-2.22 (m, 1 H), 2.62 (s, 3 H), 2.58-2.66 (m, 1 H), 2.93 (s, 3 H), 3.39-3.43 (m, 1 H), 3.48-3.53 (m ,1 H), 4.99 (t, J= 7.2 Hz, 1 H), 6.89 (t, J = 2.4 Hz, 1 H), 7.07 (d, J = 8.8 Hz, 2 H), 7.28 (s, 1 H), 7.53 (s, 1 H), 7.95 (d, J = 8.8 Hz, 2 H); ESI MS m/z (relative intensities): 410 (M+H)⁺ (100 %); UPLC Purity: 97.85 %, Ret. time: 3.136 min. Chiral Purity by HPLC: 99.59 %, Ret. Time: 57.46 min. % ee: 99.18 %

Intermediate 14: (S) -(-) -Methyl 3-[4-(5-methyl-l,3,4-oxadiazol-2-yl)phenoxy]-5-[(l- methyl-2-oxo- pyrrolidin-3-yl) oxyjbenzoate

Sodium hydride suspension (0.71 g, 50 %) was added to a stirring solution of (£)-(-)- methyl 3 -(4-(5 -methyl- 1 ,3,4-oxadiazol-2-yl)phenoxy)-5-((2-oxopyrrolidin-3- yl)oxy)benzoate (5.5 g) (Intermediate 15) in dry DMF taken in a round bottomed flask fitted with anhydrous CaCl₂ guard tube at room temperature. The reaction mixture was stirred at the same temperature for 15 min. Methyl iodide (0.91 mL) was added and stirred till the reaction completion. The reaction mixture was quenched with ice-water, extracted with DCM. All organic layers were combined, washed with water, brine, dried over sodium sulphate, filtered and concentrated in vaccuo to get the thick liquid product. The liquid was triturated with EtOAc: hexane to get the white solid product (5.3 g).

¹H NMR (CDCl₃, 400 MHz) δ ppm: 2.14-2.21 (m, 1 H), 2.58-2.63 (m, 1 H), 2.64 (s, 3 H), 2.93 (s, 3 H), 3.39-3.43 (m, 1 H), 3.48-3.53 (m , 1 H), 3.89 (s, 3 H), 4.99 (t, J = 7.2 Hz, 1 H), 6.99 (t, J = 2 Hz, 1 H), 7.07 (d, J= 8.8 Hz, 2 H), 7.35 (s, 1 H), 7.53 (s, 1 H), 7.99 (d, J = 8.8 Hz, 2 H); ESI MS m/z (relative intensities): 424.1 (M+H)⁺ (100 %); UPLC Purity: 96.1 1 %, Ret. time: 3.68 min. Chiral Purity by HPLC: 92.05 %, Ret. Time: 39.33 min.

Intermediate 15: (S) -(-) -Methyl 3-(4-(5-methyl-l,3,4-oxadiazol-2-yl)phenoxy)-5-((2- oxo pyrrolidin-3-yl)oxy) benzoate

To a stirring mixture of Methyl 3-hydroxy-5-[4-(5-methyl-l,3,4-oxadiazol-2- yl)phenoxy] benzoate (7 g) (Intermediate 7) and (/?)-(+)-3-hydroxy-2-pyrrolidinone (Intermediate 16) (2.4g) in dry THF (200 mL) taken in round bottomed flask fitted with anhydrous CaCl₂ guard tube, triphenyl phosphine (1 1.3 g) was added. Diisopropyl azodicarboxylate (DIAD) (6.2 mL) in dry THF (10 mL) was added drop wise to the above reaction mixture. The reaction was stirred at room temperature. Reaction was monitored by TLC for completion. After completion, reaction mixture was concentrated under vacuum to remove the solvents. Diluted with DCM and coated over silica gel and chromatographed to furnish the product as white solid (6 g). ¹H NMR (CDCl₃, 400 MHz) δ ppm: 2.26-2.33 (m, 1 H), 2.62 (s, 3 H), 2.64-2.71 (m, 1 H), 3.40-3.47 (m, 1 H), 3.51-3.55 (m, 1 H), 3.89 (s, 3 H), 4.89 (t, J= 7.6 Hz, 1 H), 6.07 (bs, 1 H), 6.99 (t, J= 2.4 Hz, 1 H), 7.11 (d, J= 8.8 Hz, 2 H), 7.36 (s, 1 H), 7.51 (s, 1 H), 8.03 (d, J = 8.8 Hz, 2 H); ESI MS m/z (relative intensities): 410.1 (M+H)⁺ (100 %); UPLC Purity: 98.35 %, Ret. time: 3.47 min. Chiral Purity by HPLC: 95.31 %, Ret. Time: 47.97 min. ee: 90.62 %.

Intermediate 16: (R)-(+)-3-Hydroxy-2-pyrrolidinone

To a stirring mixture of 4-Nitrobenzoic acid (21.5 g) and (5)-(-)-3-hydroxy-2- pyrrolidinone (11.8 g) (Intermediate 17) in dry THF (360 mL) taken in a round bottomed flask fitted with anhydrous CaCl₂ guard tube, triphenyl phosphine (61.2 g) was added. To this reaction mixture, diisopropyl diazodicarboxylate (DIAD) (34 mL) was added drop wise in three portions at room temperature. The reaction was stirred at room temperature. The progress of the reaction was monitored by TLC (developing agents: UV, I₂, as well as aqueous acidic KMnO₄). After completion, reaction mixture was concentrated under vacuum to obtain residue. Methanol (360 mL) was added to the residue followed by potassium carbonate (10 g) at room temperature. The reaction was stirred at room temperature. The progress of the reaction was monitored by TLC (developing agents: UV, I₂, as well as aqueous acidic KMnO₄). After completion, reaction mixture was diluted with CHCl₃ and filtered through celite. Celite bed was successively washed with 1 % MeOH:CHCl₃. The filtrates were combined and concentrated to dryness to remove solvents. The residues were partitioned between EtOAc: dil. HCl (200 mL, 9:1) and stirred for 15 min. Layers were separated, aq. layer was washed with EtOAc thrice until all organic impurities were washed out. The aq. Layer was concentrated to dryness to remove the water and solid residues were obtained. The residues obtained were washed with 1-2 % MeOH: CHCl₃ (3 x 100 mL), dried over sodium sulfate, filtered trough cotton, concentrated to get brown thick liquid product.

¹U NMR (CDCl₃, 400 MHz) δ ppm: 2.03-2.13 (m, 1 H), 2.46-2.54 (m, 1 H), 3.28-3.35 (m, IH), 3.38-3.48 (m, 1 H), 4.50 (t, J = 8.4 Hz, 1 H), 4.55 (bs, 1 H), 7.02 (bs, 1 H); [α]_D²⁵: + 68, c = l, CHCl₃

Intermediate 17: (S)-(-)-3-hydroxy-2-pyrrolidinone

Cone. H₂SO₄ (14.8 g, 8 mL) was added drop wise over 5 min to the stirring solution of (5)-(-)-4-Amino-2-hydroxybutyric acid (15 g) [CAS No. 40371-51-5] in MeOH (95 rnL) under dry conditions using anhydrous CaCl₂ guard tube. After refluxing for 4 h, the reaction mixture was allowed to cool to room temperature and diluted with water (15 mL). Potassium carbonate (24 g) was added in portions to the reaction mixture and stirred overnight (20 h). Reaction mixture was diluted with CHCl₃, filtered through celite. Celite bed was thoroughly washed with 1 % MeOHiCHCl₃. The filtrates were combined and evaporated to dryness to obtain thick liquid residue. The residue was subjected to aging using 1-2 % MeOHiCHCl₃ and then filtered. Organic layers were combined, dried over anhydrous sodium sulphate, filtered and concentrated to obtain the white solid. (1 1.8 g)

¹H NMR (CDCl₃, 400 MHz) δ ppm: 2.03-2.13 (m, 1 H), 2.48-2.55 (m, 1 H), 3.30-3.35

(m, IH), 3.36-3.50 (m, 1 H), 4.34 (t, J = 8.4 Hz, 1 H), 6.51 (bs, 1 H); [α]_D²⁵: + 98, c =

1, CHCl₃

Following examples (Example 70-76) were prepared by using similar procedure as that of example lwith suitable modifications as are well within the scope of a skilled person