Reaction Steps
Methyl 2-(4-(methylsulfonyl)benzyl)-4-(3-oxo-2,3-dihydroisoxazol-5-yl)piperidine-1-carboxylate (1 g, 2.54 mmol) was subjected to chiral preparative HPLC in two steps (first using Column: Chiralcel OJ (250×50), 20 μm particle size, mobile phase: Heptane/IPA/FA 30/70/0.1, flow rate 120 mL/min and then using Column: Chiralpak AD (250×50), 20 μm particle size, mobile phase: Heptane/EtOH/FA 40/60/0.1, flow rate 120 mL/min) to yield (2R,4S)-Methyl 2-(4-(methylsulfonyl)benzyl)-4-(3-oxo-2,3-dihydroisoxazol-5-yl)piperidine-1-carboxylate (231 mg, 23%), Chiral purity 99.5% ee, Optical rotation [α]D20=+10.1 (acetonitrile, c=1), 1H NMR (600 MHz, cdcl3) δ 1.87-1.97 (m, 3H), 2.02-2.11 (m, 1H), 2.68 (dd, 1H), 2.88 (dd, 1H), 2.96-3.06 (m, 4H), 3.12-3.22 (m, 1H), 3.60 (s, 3H), 3.96-4.02 (m, 1H), 4.27-4.35 (m, 1H), 5.74 (s, 1H), 7.30 (d, 2H), 7.82 (d, 2H); (2S,4R)-methyl 2-(4-(methylsulfonyl)benzyl)-4-(3-oxo-2,3-dihydroisoxazol-5-yl)piperidine-1-carboxylate (225 mg, 22.5%), Chiral purity 98.4% ee, Optical rotation [α]D20=−11.4 (acetonitrile, c=1), 1H NMR (600 MHz, cdcl3) δ 1.86-1.97 (m, 3H), 2.02-2.10 (m, 1H), 2.67 (dd, 1H), 2.87 (dd, 1H), 2.96-3.05 (m, 4H), 3.12-3.20 (m, 1H), 3.59 (s, 3H), 3.95-4.02 (m, 1H), 4.27-4.34 (m, 1H), 5.74 (s, 1H), 7.29 (d, 2H), 7.81 (d, 2H) and trans-methyl 2-(4-(methylsulfonyl)benzyl)-4-(3-oxo-2,3-dihydroisoxazol-5-yl)piperidine-1-carboxylate (185 mg, 18.5%)
