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Helvetica Chimica Acta – Vol. 98 (2015)
(m, 1 H); 3.96 – 3.84 (m, 1 H); 3.77 (s, 6 H); 2.82 – 2.55 (m, 2 H); 1.74 – 1.62 (m, 2 H); 1.24 (d, J ¼ 6.2,
3 H). 13C-NMR (75 MHz, CDCl3): 160.8, 160.7; 141.0, 140.9; 138.4, 138.0; 128.4, 128.3; 127.8, 127.7; 127.6;
107.4, 107.3; 98.3, 98.2; 72.5, 72.4; 70.6, 70.3; 69.2; 55.2; 44.4, 44.3; 42.9, 42.5; 19.6, 19.3. ESI-MS: 353
([M þ Na]þ).
(4R)-4-(Benzyloxy)-1-(3,5-dimethoxyphenyl)pentan-2-one (7). To stirred soln. of IBX (0.173 g,
0.618 mmol) in dry DMSO (0.5 ml) and dry CH2Cl2 (2 ml) was added a soln. of 6 (0.102 g, 0.309 mmol) in
dry CH2Cl2 (2 ml) at r.t., and the mixture was stirred for 3 h at r.t. After completion of the reaction, the
mixture was filtered, diluted with H2O (5 ml), and extracted into CH2Cl2 (2 ꢁ 10 ml). The combined org.
layer was washed with brine (5 ml), dried (Na2SO4), and evaporated to give crude 7, which was purified
by CC (hexanes/AcOEt 9 :1) to afford pure 7 (0.090 g, 90%). Colorless liquid. [a]3D4 ¼ ꢀ98.3 (c ¼ 0.9,
CHCl3). IR (neat): 2931, 1713, 1600, 1461, 1152, 1062, 743, 697. 1H-NMR (300 MHz, CDCl3): 7.32 – 7.17
(m, 5 H); 6.31 – 6.23 (m, 3 H); 4.55 – 4.35 (m, 2 H); 4.06 – 3.93 (m, 1 H); 3.72 (s, 6 H); 3.57 (s, 2 H); 2.76
(dd, J ¼ 15.8, 7.3, 1 H); 2.41 (dd, J ¼ 15.8, 5.2, 1 H); 1.18 (d, J ¼ 6.2, 3 H). 13C-NMR (75 MHz, CDCl3):
205.9; 161.0; 138.5; 136.0; 128.3; 127.6; 127.5; 107.4; 99.2; 71.7; 70.9; 55.5; 55.1; 48.7; 19.9. ESI-MS: 329
([M þ H]þ).
(4R)-1-(3,5-Dimethoxyphenyl)-4-hydroxypentan-2-one (8). To a stirred soln. of 7 (0.070 g,
0.213 mmol) in dry CH2Cl2 (5 ml) was added a soln. of TiCl4 (0.47 ml, 0.426 mmol) in anh. CH2Cl2
(5 ml) under N2 at 08, and the mixture was stirred at this temp. for 2 h. On completion (TLC), the mixture
was diluted with H2O (10 ml) and extracted with CH2Cl2 (2 ꢁ 10 ml). The combined org. extracts were
washed with aq. NaHCO3 soln. and dried (Na2SO4), and the solvent was removed under reduced
pressure. The crude residue was purified by CC (hexanes/AcOEt 7:3) to afford 8 (0.040 g, 80%). Viscous
liquid. [a]2D5 ¼ þ2.00 (c ¼ 0.1, MeOH). IR (neat): 2921, 2851, 1716, 1598, 1461, 1218, 772, 670. 1H-NMR
(300 MHz, CDCl3): 6.36 (t, J ¼ 2.0, 1 H); 6.32 (d, J ¼ 2.0, 2 H); 4.21 – 4.13 (m, 1 H); 3.77 (s, 6 H); 3.60 (s,
2 H); 2.64 – 2.49 (m, 2 H); 1.14 (d, J ¼ 6.0, 3 H). 13C-NMR (75 MHz, CDCl3): 208.9; 161.0; 135.6; 107.4;
99.1; 63.8; 55.2; 50.9; 49.5; 22.3. ESI-MS: 239 ([M þ H]þ).
(4R)-1-(3,5-Dihydroxyphenyl)-4-hydroxypentan-2-one (1) [4]. I2 (216 mg, 1.701 mmol) was added to
a mixture of Al powder (31 mg, 1.148 mmol) in anh. benzene (3 ml). The mixture was heated at reflux for
0.5 h and cooled to 08, then Bu4NI (2 mg) and 8 (15 mg, 0.063 mmol) in benzene (2 ml) were added. The
mixture was stirred for 15 min at 08, then the reaction was quenched with 2n HCl (5 ml) at 08, and the
mixture extracted with AcOEt (3 ꢁ 10 ml). The org. phase was washed with sat. aq. NaHCO3 soln. (3 ml)
and brine (5 ml), dried (Na2SO4), and concentrated in vacuo. The residue was purified by CC (hexanes/
AcOEt 3 :7) to afford 1 (9.9 mg, 75%). Colorless solid. [a]2D5 ¼ þ13.2 (c ¼ 0.22, MeOH). IR (KBr): 3496,
1
3262, 2924, 1517, 1154, 996, 770. H-NMR (300 MHz, CD3OD): 6.16 (t, J ¼ 2.0, 1 H); 6.80 (d, J ¼ 2.0,
2 H); 4.19 – 4.14 (m, 1 H); 3.56 (s, 2 H); 2.65 – 2.51 (m, 2 H); 1.27 (d, J ¼ 6.1, 3 H). 13C-NMR (75 MHz,
CD3OD): 209.8; 159.8; 137.6; 109.1; 102.3; 65.0; 51.6; 51.4; 23.4. HR-ESI-MS: 211.0974 ([M þ H]þ,
C11H15Oþ4 ; calc. 211.0965).
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