Reaction Steps
Separation of the enantiomers comprising cis-N-[2-(4-bromophenoxy)cyclopentyl]propane-2-sulfonamide (1.586 g, 4.38 mmol) was carried out by chiral chromatography. Column: Chiralpak® AD-H, 2.1×25 cm, 5 μm; Mobile phase: 75:25 carbon dioxide:methanol; Flow rate: 65 g/min. The first-eluting compound was enantiomer N-[(1R,2S)-2-(4-bromophenoxy)cyclopentyl]propane-2-sulfonamide (767 mg, 2.12 mmol, 48%) and the second-eluting peak provided desired product N-[(1S,2R)-2-(4-bromophenoxy)cyclopentyl]propane-2-sulfonamide upon removal of solvent in vacuo. Yield: 758 mg, 2.09 mmol, 48%. The absolute stereochemistry of these enantiomers was assigned by analogy to their higher homologues (see Example 7). The title compound, synthesized in the following step, proved significantly more potent than its enantiomer (prepared in the same way from N-[(1R,2S)-2-(4-bromophenoxy)cyclopentyl]propane-2-sulfonamide. On this basis, the (1S,2R) configuration was assigned to N-[(1S,2R)-2-(4-bromophenoxy)cyclopentyl]propane-2-sulfonamide. MS (APCI) m/z 364.2 (M+1). 1H NMR (500 MHz, CDCl3) δ 1.35 (d, J=6.8 Hz, 3H), 1.38 (d, J=6.8 Hz, 3H), 1.64 (m, 1H), 1.79-1.98 (m, 4H), 2.12 (m, 1H), 3.13 (septet, J=6.8 Hz, 1H), 3.86 (m, 1H), 4.59 (m, 1H), 4.63 (d, J=9.5 Hz, 1H), 6.78 (d, J=9.0 Hz, 2H), 7.39 (d, J=9.1 Hz, 2H). Data for N-[(1R,2S)-2-(4-bromophenoxy)cyclopentyl]propane-2-sulfonamide: MS (APCI) m/z 362.2, 364.2 (M+1). 1H NMR (500 MHz, CDCl3) δ 1.35 (d, J=6.8 Hz, 3H), 1.38 (d, J=6.8 Hz, 3H), 1.58-1.68 (m, 1H), 1.78-1.97 (m, 4H), 2.12 (m, 1H), 3.13 (septet, J=6.8 Hz, 1H), 3.86 (m, 1H), 4.59 (m, 1H), 4.64 (d, J=9.5 Hz, 1H), 6.78 (d, J=9.1 Hz, 2H), 7.39 (d, J=9.0 Hz, 2H).
