*3.3. Deprotection of the N-Tosyl Regioisomer Mixture to Yield 13*

A 1:11 mixture of **12** and **11** (140 mg, 0.35 mmol) in a saturated solution of NaHCO3 (5 mL) and MeOH (50 mL) was heated to reflux for 2.5 h. The mixture was acidified with HCl (32% aqueous) to pH 6 then concentrated and subjected to flash chromatography (silica, 1:10 *v*/*v* MeOH/CH2Cl2 elution) to afford a 1:26 mixture of compounds **14** and **13** (59 mg, 68%). This material (59 mg) was pre-adsorbed to C18-bonded silica (1 g) overnight, then packed into a guard cartridge that was attached to a C18-bonded silica semi-preparative HPLC column. Application of the same reversed-phase HPLC purification method described above (Section 3.2) afforded **13** (15 mg, 11%, <sup>t</sup> R = 23.0–24.0 min) as an orange powder.

Compound **13**: Orange amorphous solid; 1H-NMR (500 MHz, DMSO-*d*6) δ<sup>H</sup> 3.31–3.33 (2H, m, H-2), 3.81–3.84 (2H, m, H-3), 6.57 (1H, d, *J* = 2.8 Hz, H-6), 7.13 (1H, d, *J* = 2.8 Hz, H-7), 9.05 (1H, brs, H-4), 12.76 (1H, brs, H-8); 13C-NMR (125 MHz, DMSO-*d*6) δ<sup>C</sup> 39.4 (C-3), 48.2 (C-2), 107.5 (C-6), 120.7 (C-5a), 125.4 (C-7), 132.9 (C-8a), 148.2 (C-4a), 169.8 (C-9), 174.1 (C-5); (+)-LRESIMS *m*/*z* (rel. int.) 253 (100) [M + H]+; (−)-LRESIMS *<sup>m</sup>*/*<sup>z</sup>* (rel. int.) 251 (100) [M − H]−; (+)-HRESIMS *<sup>m</sup>*/*<sup>z</sup>* 275.0104 [M + Na]<sup>+</sup> (calcd for C10H8N2NaO4S, 275.0097).
