Molecules 2011, 16
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J = 5.2 Hz, -OCH2CH2OCH2O-), 3.21 (1H, dd, J = 12.4, 4.0 Hz, H-3α), 2.89-2.85 (3H, m, H-18,
-NCH2CH2O-), 1.14 (3H, s, CH3), 0.98 (3H, s, CH3), 0.92 (3H, s, CH3), 0.90 (6H, s, CH3),
13
0.78 (3H, s, CH3), 0.74 (3H, s, CH3). C-NMR (75 MHz, CDCl3): δ 177.13, 143.49, 122.44, 89.21,
78.74, 72.21, 69.84, 69.29, 55.11, 47.48, 46.81, 45.71, 41.62, 41.22, 41.10, 39.24, 38.64, 38.37, 36.90,
33.71, 32.95, 32.66, 32.23, 30.57, 28.02, 27.50, 27.04, 25.73, 23.50, 23.30, 22.83, 18.22, 16.94, 15.53,
15.23. ESI-MS: m/z [M + H]+ 574.5, [M + Na]+ 596.7.
3.10. Synthesis of (2-{2-[(triphenylmethyl)amino]ethoxy}methyl olean-12-en-28-oate (12a)
To a solution of 11a (63.4 mg, 0.11 mmol) in CH2Cl2 (2.0 mL) was added DIPEA (91.3 μL,
0.55 mmol) and trityl chloride (92.1 mg, 0.33 mmol). The reaction mixture was stirred at room
temperature for 3 h before it was concentrated in vacuo. The residue was purified by column
chromatography on silica gel (hexane-EtOAc = 6:1) to afford product 12a (77.0 mg, 85.4%) as a white
solid. 1H-NMR (400 MHz, CDCl3): δ 7.47 (6H, d, J = 7.6Hz, o-H of Ph), 7.27 (6H, t, J = 7.6 Hz, m-H
of Ph), 7.18 (3H, t, J = 7.2 Hz, p-H of Ph), 5.30-5.22 (3H, m, H-12, -COOCH2O-), 3.73 (2H, t,
J = 4.8 Hz, -NCH2CH2O-), 3.60 (2H, t, J = 5.2 Hz, -OCH2CH2OCH2O-), 3.53 (2H, t, J = 4.8 Hz,
-OCH2CH2OCH2O-), 3.21 (1H, dd, J = 10.8, 4.4 Hz, H-3α), 2.86 (1H, dd, J = 13.6, 4.0 Hz, H-18),
2.36 (2H, br s, -NCH2CH2O-), 1.13 (3H, s, CH3), 0.98 (3H, s, CH3), 0.91 (3H, s, CH3), 0.90 (3H, s, CH3),
0.89 (3H, s, CH3), 0.77 (3H, s, CH3), 0.72 (3H, s, CH3). 13C-NMR (75 MHz, CDCl3): δ 177.04,
145.99 (3C), 143.53, 128.58 (6C), 127.69 (6C), 126.13 (3C), 122.41, 89.33, 78.83, 71.31, 70.51, 69.66,
69.31, 55.11, 47.50, 46.78, 45.74, 42.95, 41.62, 41.10, 39.24, 38.64, 38.34, 36.92, 33.71, 32.98, 32.68,
32.20, 30.57, 28.02, 27.52, 27.09, 25.75, 23.50, 23.30, 22.83, 18.22, 16.94, 15.50, 15.23. ESI-MS:
m/z [M + H]+ 816.7.
3.11. Cleavage at Site A of 12a with TiCl4
To a solution of 12a (10.6 mg, 0.013 mmol) in CH2Cl2 (1.0 mL) was added TiCl4 (5 μL,
0.045 mmol) dropwise. The reaction mixture was stirred at room temperature for 0.5 h before it was
poured into water (1 mL) and extracted with CH2Cl2. The organic layer was washed with a saturated
solution of NaHCO3, dried over Na2SO4 and concentrated in vacuo. The residue was purified by
column chromatography on silica gel (hexane-acetone = 5:1) to afford product 1a (5.3 mg, 89.6%) as a
1
white solid. H-NMR (300 MHz, pyridine-d5): δ 5.49 (1H, br s, H-12), 3.44 (1H, m, H-3α),
3.29 (1H, dd, J = 13.5, 3.6 Hz, H-18), 1.29 (3H, s, CH3), 1.24 (3H, s, CH3), 1.02 (9H, s, CH3),
0.95 (3H, s, CH3), 0.90 (3H, s, CH3). 13C-NMR (75 MHz, pyridine-d5): δ 180.20, 144.88, 122.61,
78.13, 55.88, 48.18, 46.72, 46.55, 42.23, 42.06, 39.82, 39.44, 39.01, 37.44, 34.29, 33.35 (2C), 33.24,
31.03, 28.85, 28.39, 28.16, 26.25, 23.89, 23.85, 23.76, 18.86, 17.49, 16.62, 15.63. ESI-MS: m/z
[M−H]− 455.3.
3.12. Cleavage at Site B of 12a with TFE
A mixture of 12a (25.0 mg, 0.031 mmol) and a solution of AcOH/TFE/CH2Cl2 (1.0 mL,
v/v/v = 1:2:7) was stirred at room temperature for 2 h before it was quenched with a saturated solution
of NaHCO3 (0.4 mL). The water layer was extracted with CH2Cl2, dried over Na2SO4 and concentrated