3.3.4. Compound **10**

Colorless gum (4.5 mg, 19%); UV (MeOH) λmax (log ε) 237 (3.91), 324 (2.83) nm; IR (UATR) νmax 3413, 2986, 1747, 1709, 1281, 1198, 1169, 1078, 1026, 973, 712 cm<sup>−</sup>1; 1H NMR (800 MHz, CD3OD) δ<sup>H</sup> 1.40 (6H, d, *J* = 6.8 Hz, H-10), 3.91 (1H, sept, *J* = 6.8 Hz, H-9), 3.97 (1H, s, 6-OMe), 3.98 (3H, s, 7-OMe), 7.23 (1H, s, H-5), 7.47 (1H, d, *J* = 5.6 Hz, H-4), 7.51 (1H, s, H-8), 8.17 (1H, d, *J* = 5.6 Hz, H-3); 13C NMR (200 MHz, CD3OD) δ<sup>C</sup> 22.4 (2C, C-10, C-11), 31.9 (C-9), 56.4 (2C, 6-OMe, 7-OMe), 104.4 (C-8), 106.8 (C-5), 119.6 (C-4), 123.3 (C-8a), 135.1 (C-4a), 140.8 (C-3), 151.8 (C-7), 154.4 (C-6), 165.1 (C-1); (+)-LRESIMS *m*/*z* (rel. int.) 232 (100) [M + H]+; (+)-HRESIMS *m*/*z* 232.1333 (calcd for C14H18NO2, 232.1332).

#### *3.4. Synthesis of Papaverine* N*-oxide (12)*

Using a method previously reported by Bremner et al. [40], the free base of papaverine (**1b**, 0.50 g, 1.5 mmol) was dissolved in CHCl3 (10 mL) and treated portion wise with MCPBA (0.35 g, 2.4 mmol) over 5 min. After completion of the addition, the solution was stirred at room temperature for 19 h. The colorless precipitate that formed was filtered and the filtrate was extracted with 5% NaOH (3 × 25 mL). The CHCl3-soluble material was dried down then recrystallized from acetone to yield pure papaverine *N*-oxide (**12**, 310 mg, 58%).

Comparison of the 1H NMR and LRMS data of product **12** with literature values confirmed the compound [40], although the 1H NMR chemical shifts for two methoxyl signals had been incorrectly assigned to δ<sup>H</sup> 6.14 and 6.15; this being a typographical error. The 1H NMR data for papaverine *N*-oxide was initially reported in CDCl3 at 60 MHz; no 13C NMR data was reported in the original article [40], hence we recorded 1D and 2D NMR data for **12** in both CDCl3 and CD3OD, and report the full NMR assignments here for completeness.

#### Compound **12**

White amorphous solid (310 mg, 58%); 1H NMR (800 MHz, CDCl3) δ<sup>H</sup> 3.800*<sup>a</sup>* (3H, s, 12-OMe), 3.803*<sup>a</sup>* (3H, s, 13-OMe), 3.94 (3H, s, 7-OMe), 3.99 (3H, s, 6-OMe), 4.73 (2H, s, H-9), 6.73 (1H, d, *J* = 8.3 Hz, H-14), 6.80 (1H, dd, *J* = 8.3, 2.1 Hz, H-15), 7.01 (1H, d, *J* = 2.1 Hz, H-11), 7.03 (1H, s, H-5), 7.21 (1H, s, H-8), 7.42 (1H, d, *J* = 7.0 Hz, H-4), 8.16 (1H, d, *J* = 7.0 Hz, H-3); 13C NMR (200 MHz, CDCl3) δ<sup>C</sup> 31.8 (C-9), 56.00*<sup>b</sup>* (12-OMe), 56.01*<sup>b</sup>* (13-OMe), 56.2 (7-OMe), 56.3 (6-OMe), 103.1 (C-8), 106.1 (C-5), 111.4 (C-14), 112.3 (C-11), 120.4 (C-15), 121.1 (C-4), 124.9 (C-8a), 125.7 (C-4a), 130.1 (C-10), 135.3 (C-3), 145.8 (C-1), 147.9 (C-13), 149.3 (C-12), 151.3 (C-6), 151.8 (C-7); 1H NMR (800 MHz, CD3OD) δ<sup>H</sup> 3.747*<sup>b</sup>* (3H, s, 12-OMe), 3.748*<sup>b</sup>* (3H, s, 13-OMe), 3.91 (3H, s, 6-OMe), 3.96 (3H, s, 7-OMe), 4.79 (2H, s, H-9), 6.79 (1H, dd, *J* = 8.3, 1.8 Hz, H-15), 6.82 (1H, d, *J* = 8.3 Hz, H-14), 7.01 (1H, d, *J* = 1.8 Hz, H-11), 7.33 (1H, s, H-5), 7.38 (1H, s, H-8), 7.72 (1H, d, *J* = 7.0 Hz, H-4), 8.14 (1H, d, *J* = 7.0 Hz, H-3); 13C NMR (200 MHz, CD3OD) δ<sup>C</sup> 32.2 (C-9), 56.44*<sup>c</sup>* (12-OMe), 56.47*<sup>c</sup>* (13-OMe), 56.63*<sup>d</sup>* (7-OMe), 56.66*<sup>d</sup>* (6-OMe), 104.8 (C-8), 107.3 (C-5), 113.2 (C-14), 113.8 (C-11), 121.9 (C-15), 123.2 (C-4), 125.6 (C-8a), 129.1 (C-4a), 131.3 (C-10), 134.8 (C-3), 148.4 (C-1), 149.4 (C-13), 150.7 (C-12), 153.6 (C-7), 154.1 (C-6); (+)-LRESIMS *m*/*z* (rel. int.) 356 (100) [M + H]+. *a,b,c,d* Interchangeable signals.
