3.1.12. *1,7-bis(4-Hydroxy-3-methoxyphenyl)-4,4-dimethylheptane-3,5-diol* (**21**)

To a solution of compound **20** (110 mg, 0.27 mmol) in MeOH (3 mL) was added NaBH4 (30 mg, 0.81 mmol) at 0 ◦C. The resulting mixture was allowed to stir at room temperature for 2 h, and then H2O (3 mL) was added. The aqueous layer was separated and extracted with CH2Cl2 (3 × 6 mL). The combined organic extracts were washed brine, dried over MgSO4, filtered and concentrated to give the crude residue, which was purified by flash chromatography on silica gel with EtOAc/*n*-hexane/ (1:1) to afford compound **21** (34 mg, 31% yield) as a colorless oil. 1H-NMR (CDCl3) δ 6.86 (d, *J* = 8.0 Hz, 2H), 6.74–6.71 (m, 4H), 5.63 (s, 2H), 3.89 (s, 6H), 3.59–3.56 (m, 2H), 3.11 (s, 2H), 2.85–2.71 (m, 2H), 2.61–2.55 (m, 2H), 1.81–1.72 (m, 4H), 0.90 (s, 6H); 13C-NMR (CDCl3) δ 146.5, 143.7, 134.1, 134.0, 120.9, 114.3, 111.1, 78.7, 55.9, 40.3, 33.9, 32.8, 21.0; HRMS [ESI]<sup>+</sup> calculated for C23H32NaO6: 427.4928 [M + Na]+; found: 427.4933.
