Synthesis of small molecule inhibitors of the orphan nuclear receptor steroidogenic factor-1 (NR5A1) based on isoquinolinone scaffolds

Abstract

Three synthetic routes were developed for structure-activity relationship (SAR) studies of HTS-derived isoquinolinone inhibitor probes for the orphan nuclear receptor steroidogenic factor-1 (NR5A1). Among the new analogs reported herein, 31 and 32 have improved potency, lower cellular toxicity, and improved selectivity compared to the initial HTS-derived leads 1 and 2.

Figure 1

SF-1 inhibitors identified via ultra high throughput screening of the MLSCN library

Scheme 1

(a) peroxyacetic acid, CH₂Cl₂ (99%); (b) acetic anhydride, 140°C, 4 h, then concentrate; (c) NaOMe, MeOH (60%, 2 steps); (d) NaH, DMF, 30 min, then ethyl (±)-2-bromopropionate (80%); (e) Cs₂CO₃, DMF, tert-butyl bromoacetate (80%); (f) 2 M HCl in Et₂O and EtOH; (g) EDC, DMAP, CH₂Cl₂, 8 or 9 (45%, two steps)

Scheme 2

(a) iodobutane, acetone, K₂CO₃, 60°C, 4 h (60−85%); (b) 1.5 equiv H₂CrO₄, acetone, 1 h (98%); (c) 9, EDC, DMAP, CH₂Cl₂ (83%); (d) (i). O₃, CH₂Cl₂, −78°C, (ii) PPh₃, (iii). cat. I₂, CH₂Cl₂ (45%).

Scheme 3

(a) ethyl (±)-2-bromopropionate, K₂CO₃, acetone, 60 °C, 4 h. (b) (i) O₃, CH₂Cl₂, −78 °C (ii) Me₂S, 1 h, 23 °C. (c) tert-butyl glycine hydrochloride (17a), 3 equiv. Et₃N, AcOH to achieve pH 3 to 5, benzene, 100°C, sealed tube, 12 h (67%). (d) glycine (17b, 3 equiv), benzene, 100°C, 12 h, sealed tube (94%).

Scheme 4

(a) (i). TBSOTf, Et₃N, THF (ii) OsO₄ (2%), NMO, t-BuOH, acetone. (b) NaIO₄, acetone, H₂O, THF, t-BuOH (78% from 19). (c) glycine tert-butyl ester hydrochloride, benzene, Et₃N and AcOH until pH 3−5, 100°C sealed tube 12 h (21%). (d) 2 M HCl in Et₂O and EtOH, (99%) (e) 9, EDC, DMAP, CH₂Cl₂, (55%).

Figure 1

Titration curves for 32 vs. SF-1 (□), RORα(△), VP16 (▽), and the cytotoxicity assays (○). Data represent the mean of three independent experiments with the calculated standard deviation.