Synthesis and Characterization of a Hyodeoxycholic Acid Conjugate

Following general procedure A, reaction of hyodeoxycholic acid (0.050 g, 0.127 mmol) with di-tert-butyl butane-1,4-diylbis((3-aminopropyl)carbamate) (6a) (0.026 g, 0.0637 mmol), PyBop (0.073 g, 0.140 mmol) and DIPEA (0.067 mL, 0.382 mmol) in DMF (2 mL) afforded di-tert-butyl butane-1,4-diylbis((3-((R)-4-((3R,5R,6S,8S,9S,10R,13R,14S,17R)-3,6-dihydroxy-10,13-dimethylhexadecahydro-1H-cyclopenta[a]phenanthren-17-yl)pentanamido)propyl)carbamate) (0.056 g, 76%) as a clear colorless oil. Following general procedure C, a sub-sample of the product (0.047 g, 0.0408 mmol) was reacted with TFA in CH₂Cl₂ to afford, after chromatography, the di-TFA salt 7a (0.034 g, 71%) as a pale-yellow oil. [α ${]}_{\mathsf{D}}^{20.3}$ = +3 (c = 0.1, MeOH); R_f (RP-18, 10% aq. HCl:MeOH 1:3) 0.17; IR (ATR) ν_max 3339, 2941, 1635, 1455, 1202, 1139, 1027 cm⁻¹; ¹H NMR (DMSO-d₆, 400 MHz) δ 8.63 (4H, br s, NH₂-29), 8.01 (2H, t, J = 5.7 Hz, NH-25), 3.84–3.79 (2H, m, H-6), 3.35–3.27 (2H, m, H-3), 3.09 (4H, q, J = 6.3 Hz, H₂-26), 2.90–2.87 (8H, m, H₂-28, H₂-30), 2.11–2.08 (2H, m, H₂-23b), 1.99–-1.95 (2H, m, H₂-23a), 1.92–0.93 (56H, m, H₂-1, H₂-2, H₂-4, H-5, H₂-7, H-8, H-9, H₂-11, H₂-12, H-14, H₂-15, H₂-16, H-17, H-20, H₂-22, H₂-27, H₂-31), 0.87 (6H, d, J = 6.4 Hz, H₃-21), 0.83 (6H, s, H₃-19), 0.59 (6H, s, H₃-18); ¹³C NMR (DMSO-d₆, 100 MHz) δ 173.2 (C-24), 70.0 (C-3), 65.9 (C-6), 55.9 (C-14), 55.5 (C-17), 48.3 (C-5), 46.1 (C-30), 44.6 (C-28), 42.4 (C-13), 39.5 (C-9, obscured by solvent), 39.4 (C-12, obscured by solvent), 35.5, 35.4 (C-1, C-26), 35.0, 34.9 (C-7, C-8, C-10), 34.4 (C-20), 32.3 (C-23), 31.5 (C-22), 30.3 (C-4), 29.3 (C-2), 27.7 (C-16), 26.1 (C-27), 23.9 (C-15), 23.6 (C-19), 22.7 (C-31), 20.4 (C-11), 18.3 (C-21), 11.9 (C-18); (+)-HRESIMS [M + H]⁺ m/z 951.7873 (calcd for C₅₈H₁₀₃N₄O₆, 951.7872).