“…The residue was purified by column chromatography (basic alumina, gradient elution, 100% CH 2 Cl 2 to 10% MeOH–CH 2 Cl 2 ) to provide (−)-kopsinine ( 5 , 2.6 mg, 82% over two steps) as a white solid identical in all respects with authentic material: For natural (−)-kopsinine 5 : [α] D 23 −56 ( c 0.15, CHCl 3 ); for ent -(+)-kopsinine 5 : [α] D 23 +57 ( c 0.84, CHCl 3 ) vs lit. [α] D 23 −76.9 ( c 2.09, CHCl 3 ) 15a and [α] D 23 −69±3 ( c 0.856, CHCl 3 ) 15c for natural (−)- 5 ; 1 H NMR (600 MHz, CDCl 3 (passed through a basic alumina)) δ 7.16 (d, J = 7.3 Hz, 1H), 6.98 (t, J = 7.6 Hz, 1H), 6.75 (t, J = 7.4 Hz, 1H), 6.66 (d, J = 7.7 Hz, 1H), 3.76 (s, 3H), 3.34 (q, J = 8.3 Hz, 1H), 3.12 (d, J = 13.5 Hz, 1H), 2.92–3.01 (m, 3H), 2.89 (t, J = 9.6 Hz, 1H), 2.79 (t, J = 11.7 Hz, 1H), 2.64 (t, J = 11.2 Hz, 1H), 1.87–1.96 (m, 2H), 1.52–1.62 (m, 2H), 1.35–1.45 (m, 2H), 1.19–1.34 (m, 4H); 13 C NMR (150 MHz, CDCl 3 ) δ 174.8, 149.1, 140.7, 126.6, 121.6, 119.7, 110.8, 68.4, 66.7, 57.9, 52.0, 50.7, 47.6, 43.8, 36.5, 34.8, 33.92, 33.88, 32.1, 31.8, 17.1; IR (film) υmax 2922, 1726, 1458, 1203, 741, 670 cm −1 ; HRMS (ESI) m/z 339.2067 [(M+H) + , C 21 H 26 N 2 O 2 requires 339.2067].…”