3.1.14. (3*S*,4*S*)-4-methoxy-5,8-bis(methoxymethoxy)-1-oxo-3-pentylisochromane-7-carbaldehyde (**12a**)

A stirred solution of **7a** (185.1 mg, 0.469 mmol) in CH2Cl2 (10.0 mL) was cooled to −78 ◦C and a stream of ozone was passed through it for 30 min. At this time, ozone gas was bubbled into the reaction mixture until the color of the reaction mixture turned to blue. After completion of the reaction, the mixture was purged with oxygen gas for 30 min before being treated with PPh3 (246.2 mg, 0.939 mmol) and allowed to warm to room temperature. After stirring at the same temperature for 12 h, the mixture was concentrated under reduced pressure and the resultant mixture was purified with column chromatography (EtOAc:*n*-hexane = 1:4 to 2:3) to give diMOM benzaldehyde derivative **12a** (177.4 mg, 95%) as a white solid. m.p. 38–39 ◦C; 1H-NMR (400 MHz, CDCl3) δ 10.42 (1H, s), 7.83 (1H, s), 5.29 (2H, s), 5.2 (2H, s), 4.65 (1H, d, *J* = 1.0 Hz), 4.29 (1H, *J* = 1.0, 5.6, 8.3 Hz), 3.59 (3H, s), 3.50 (3H, s), 3.35 (3H, s), 2.06 (1H, m), 1.83 (1H, m), 1.70-1.50 (1H, overlapped), 1.44 (1H, m), 1.40-1.30 (4H, overlapped), 0.91 (3H, t, *J* = 7.1 Hz); 13C-NMR (125 MHz, CDCl3) δ 189.9, 161.4, 156.6, 150.6, 135.8, 132.5, 120.8, 116.9, 103.0, 95.4, 81.0, 68.7, 58.4, 57.8, 57.0, 31.9, 30.8, 25.2, 22.8, 14.3.; IR (KBr) 2957, 2929, 2859, 2829, 1730, 1691, 1379, 1155, 930 cm<sup>−</sup>1; HRMS (ESI) *m*/*z* (M + H)<sup>+</sup> calculated for (C20H29O8) <sup>+</sup> 397.1862, found 397.1866.
