GPR40/FFAR1 is a G protein-coupled receptor predominantly expressed in pancreatic β-cells and activated by long-chain free fatty acids, mediating enhancement of glucose-stimulated insulin secretion. A novel series of substituted 3-(4-aryloxyaryl)propanoic acid derivatives were prepared and evaluated for their activities as GPR40 agonists, leading to the identification of compound 5, which is highly potent in in vitro assays and exhibits robust glucose lowering effects during an oral glucose tolerance test in nSTZ Wistar rat model of diabetes (ED₅₀ = 0.8 mg/kg; ED₉₀ = 3.1 mg/kg) with excellent pharmacokinetic profile, and devoid of cytochromes P450 isoform inhibitory activity

Synthesis of compound 5 is depicted in Scheme 1a.

The reductive amination1 of commercially available 3-thiophene-aldehyde (3) and isopropyl amine using sodium triacetoxyborohydride resulted in secondary amine intermediate 4. Compound 4 on further reductive amination under similar conditions with aldehyde intermediate, (S)-3-(4-((3-formylbenzyl)oxy)phenyl)hex-4-ynoic acid (8), afforded 2d in high yields. The aldehyde intermediate, 8 was obtained from (S)-3-(4-hydroxyphenyl)hex-4-ynoic acid (6) as shown in Scheme 1b. Acid 6 was synthesized via 5-step reported procedure using commercially available 4-hydroxybenzaldehyde and Meldrum’s acid.2 Resolution of racemic acid 6 was accomplished via diastereomeric salt formation with (1S,2R)-1-amino-2-indanol followed by salt break with aqueous acid to furnish compound 6. Treatment of 6 with of 40% aqueous tetrabutylphosphonium hydroxide (nBu4POH) in THF, followed by addition of 3-formyl benzyl bromide (7), afforded aldehyde intermediate 8. Compound 2d was further converted to its corresponding calcium salt (5) in two-step sequence with excellent chemical purity.

Scheme 1a. Synthesis of Compounds 2d and 5. Reagent and Conditions: (a) CH(CH3)2NH2, NaB(OAc)3H, CH3COOH, dry THF, 0 ᵒC to r.t., 16 h; (b) Comp 8, NaB(OAc)3H, CH3COOH, dry THF, 0 ᵒC to r.t., 16 h; (c) NaOH, MeCN/H2O, r.t., 3 h; (d) CaCl2, MeOH/H2O, r.t., 16 h.

BASE

(S)-3-(4-((3-((isopropyl(thiophen-3- ylmethyl)amino)methyl)benzyl)oxy)phenyl)hex-4-ynoic acid (1.557 g, 3.34 mmol, 43.0 % yield) as wax solid.

1H NMR (400 MHz, DMSO-d6): δ = 12.35 (br s, 1H), 7.44 (q, J = 3.2 Hz, 2H), 7.32 – 7.24 (m, 6H), 7.04 (d, J = 4.8 Hz, 1H), 6.94 (d, J = 8.4 Hz, 2H), 5.06 (s, 2H), 3.93 (d, J = 2.4 Hz, 1H), 3.51 (d, J = 8.8 Hz, 4H), 2.84 (sept, J = 6.4 Hz, 1H), 2.57 (d, J = 8 Hz, 2H), 1.77 (d, J = 2.4 Hz, 3H), 1.01 (d, J = 6.4 Hz, 6H);

13C NMR and DEPT: DMSO-d6, 100MHz):- δ = 172.35 (C), 157.63 (C), 142.13 (C), 141.44 (C), 137.42 (C), 133.93 (C), 128.73 (CH), 128.64 (CH), 128.43 (CH), 127.99 (CH), 127.73 (CH), 126.28 (CH), 122.21 (CH), 115.10 (CH), 81.16 (C), 78.52 (C), 69.69 (CH2), 52.90 (CH2), 48.64 (CH), 48.49 (CH2), 43.44 (CH2), 33.15 (CH), 17.92 (CH3), 3.66 (CH3);

MS (EI): m/z (%) = 462.35 (100) (M+H) + ;

IR (KBr): ν = 3433, 2960, 2918, 2810, 1712, 1608, 1510, 1383, 1240, 1174, 1109, 1018 cm-1 .

CA SALT

calcium (S)-3-(4-((3-((isopropyl(thiophen-3-yl methyl)amino)methyl)benzyl)oxy)phenyl)hex-4-ynoate (1.51 g, 1.536 mmol, 46% yield) as white powder. mp: 124.5 o C;

1H NMR (400 MHz, DMSO-d6): δ = 7.43 – 7.42 (m, 2H), 7.28 – 7.24 (m, 6H), 7.04 (d, J = 4.4 Hz, 1H), 6.89 (d, J = 8.4 Hz, 2H), 5.02 (s, 2H), 4.02 (s, 1H), 3.50 (d, J = 7.2 Hz, 4H), 2.84 – 2.77 (sept, J = 6.4 Hz, 1H), 2.43 (dd, J1 = 6.8 Hz, J2 = 7.2 Hz, 1H), 2.28 (dd, J1 = 6.8 Hz, J2 = 7.2 Hz, 1H), 1.73 (s, 3H), 0.99 (d, J = 6.4 Hz, 6H);

13C NMR and DEPT (100 MHz, DMSO-d6): δ = 177.78 (C), 157.23 (C), 142.11 (C), 141.4 (C), 137.46 (C), 135.81 (C), 128.83 (CH), 128.62 (CH), 128.40 (CH), 127.94 (CH), 127.69 (CH), 126.26 (CH), 122.18 (CH), 114.77 (CH), 83.18 (C), 77.32 (C), 69.66 (CH2), 52.89 (CH2), 48.59 (CH), 48.48 (CH2), 46.86 (CH2), 33.52 (CH), 17.88 (CH3), 3.78 (CH3);

MS (EI): m/z (%) = 462.05 (100) (M+H)+ ;

ESI-Q-TOF-MS: m/z [M+H]+ calcd for [C28H31NO3S + H]+ : 462.6280; found: 462.4988;

IR (KBr): ν = 3435, 2960, 2918, 2868, 2818, 1608, 1550, 1508, 1440, 1383, 1359, 1240 cm-1 ;

HPLC (% Purity) = 99.38%; Calcium Content (C56H60CaN2O6S2) Calcd.: 4.17%. Found: 3.99%.

 COMPD Ca salt

Calcium (S)-3-(4-((3-((isopropyl(thiophen-3-yl methyl)amino)methyl)benzyl)oxy)phenyl)hex-4-ynoate

Identification of an Orally Efficacious GPR40/FFAR1 Receptor Agonist

Early process development and salt selection for AMG 837, a novel GPR40 receptor agonist, is described. The synthetic route to AMG 837 involved the convergent synthesis and coupling of two key fragments, (S)-3-(4-hydroxyphenyl)hex-4-ynoic acid (1) and 3-(bromomethyl)-4′-(trifluoromethyl)biphenyl (2). The chiral β-alkynyl acid 1 was prepared in 35% overall yield via classical resolution of the corresponding racemic acid (±)-1. An efficient and scalable synthesis of (±)-1 was achieved via a telescoped sequence of reactions including the conjugate alkynylation of an in situ protected Meldrum’s acid derived acceptor prepared from 3. The biaryl bromide 2 was prepared in 86% yield via a 2-step Suzuki−Miyaura coupling−bromination sequence. Chemoselective phenol alkylation mediated by tetrabutylphosphonium hydroxide allowed direct coupling of 1 and 2 to afford AMG 837. Due to the poor physiochemical stability of the free acid form of the drug substance, a sodium salt form was selected for early development, and a more stable, crystalline hemicalcium salt dihydrate form was subsequently developed. Overall, the original 12-step synthesis of AMG 837 was replaced by a robust 9-step route affording the target in 25% yield.