Molecules 2018, 23, 1552
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and concentrated under reduced pressure. After column chromatography (silica gel, hexane/EtOAc
9:1) compound 10 was obtained as a colorless crystalline solid (8.7 g, 95%). m.p. = 106–108 ◦C (lit.:
110–111 ◦C) [15]; [α]2D0 = +64.3◦ (c 0.345, CHCl3) (lit.: +61.0◦ (c 0.5, CHCl3)) [15]; Rf = 0.28 (silica gel,
hexane/EtOAc, 9:1); IR (KBr): 3444br, 2950s, 2932s, 2858s, 1636w, 1464m, 1388m, 1362w, 1254m, 1102s,
1
1076m, 1064m, 1050m, 1006m, 836m, 774m cm−1; H NMR (400 MHz, CDCl3): δ = 5.19 (dd, J = 3.6,
3.6 Hz, 1H, H-12), 3.55 (d, J = 10.5 Hz, 1H, H-28a), 3.22 (d, J = 10.6 Hz, 1H, H-28b), 3.21–3.16 (m, 1H, H-3),
2.06–1.95 (m, 1 H, H-18), 1.94–1.77 (m, 3 H, H-16a + H-11a + H-11b), 1.78–1.65 (m, 2H, H-19a + H-2a),
1.65–1.24 (m, 11H, H-15a + H-1a + H-6a + H-7a + H-9 + H-22a + H-15b + H-6b + H-7b + H-22b + H-21a),
1.24–1.12 (m, 2H, H-16b + H-21b), 1.16 (s, 3H, H-27), 1.12–0.96 (m, 2H, H-19b + H-2b), 0.95–0.87 (m, 1H,
H-1b), 0.93 (s, 3H, H-26), 0.93 (s, 3H, H-23), 0.91 (s, 3H, H-30), 0.89 (s, 9H, H-33), 0.89 (s, 3H, H-24),
0.89 (s, 3H, H-29), 0.75 (s, 3H, H-25), 0.71 (m, 1H, H-5), 0.03 (s, 6H, H-31) ppm; 13C NMR (100 MHz,
CDCl3):
δ = 144.3 (C-13), 122.6 (C-12), 79.6 (C-3), 69.9 (C-28), 55.4 (C-5), 47.8 (C-9), 46.6 (C-19),
42.5 (C-18), 41.9 (C-14), 40.0 (C-8), 39.5 (C-4), 38.8 (C-1), 37.1 (C-17), 37.0 (C-10), 34.3 (C-21), 33.4 (C-29),
32.8 (C-22), 31.2 (C-20), 31.1 (C-7), 28.7 (C-30), 27.8 (C-15), 26.1 (C-33), 26.1 (C-24), 25.7 (C-2), 23.8 (C-27),
23.7 (C-11), 22.2 (C-16), 18.7 (C-6), 18.3 (C-32), 16.9 (C-26), 16.3 (C-25), 15.7 (C-23),
−
3.6 (C-31a),
−4.7 (C-31b) ppm; MS (ASAP): m/z (%) = 425.5 ([M − Me2BuSiOH + H]+, 100), 557.6 ([M + H]+, 24).
(3β) 3-{[(1,1-Dimethylethyl)dimethylsilyl]oxy}-28-{[(trifluoromethyl)sulfonyl]oxy}-urs-12-en (11)
◦
Compound
9
(1.0 g, 1.8 mmol) was dissolved in DCM (50 mL). At 0 C, pyridine (0.3 mL,
3.71 mmol) and trifluoromethanesulfonic anhydride (0.45 mL, 2.7 mmol) were added slowly.
The reaction mixture was stirred for 15 min at 0 ◦C. Then NaHCO3 (20 mL, aq, satd.) was added, and
the mixture was washed with 2 M hydrochloric acid. The organic phase was dried over magnesium
sulfate, filtered, and the solvent was removed under reduced pressure to yield 11 as a colorless
amorphous solid (1.13 g, 91%). Rf = 0.46 (silica gel, hexane) 1H NMR (500 MHz, CDCl3)
:
δ = 5.17
(dd, J = 3.5, 3.5 Hz, 1H, H-12), 4.19 (d, J = 9.2 Hz, 1H, H-28a), 3.72 (d, J = 9.3 Hz, 1H, H-28b), 3.18 (dd,
J = 11.2, 4.6 Hz, 1H, H-3), 2.06–1.94 (m, 1H, H-16a), 1.94–1.89 (m, 2H, H-11a + H-11b), 1.89–1.69 (m, 1H,
H-15a), 1.69–1.62 (m, 1H, H-22a), 1.63–1.31 (m, 7H, H-2a + H-1a + H-7a + H-6a + H-9 + H-21a + H-2b),
1.31–1.15 (m, 7H, H-19 + H-18 + H-22b + H-6b + H-7b + H16b + H-21b), 1.11 (s, 3H, H-27), 1.09–1.02 (m,
1H, H-15b), 1.00 (s, 3H, H-26), 0.99–0.94 (m, 1H, H-1b), 0.94 (s, 3H, H-23), 0.94 (s, 3H, H-30), 0.91 (s, 3H,
H-24), 0.88 (s, 9H, H-33), 0.88 (m, 1H, H-20), 0.81 (d, J = 5.4 Hz, 3H, H-29), 0.75 (s, 3H, H-25), 0.73–0.68 (m,
1H, H-5), 0.03 (s, 6H, H-31) ppm; 13C NMR (125 MHz, CDCl3): δ = 137.2 (C-13), 127.0 (C-12), 118.8 (q,
J = 319.8 Hz, C-34), 84.3 (C-3), 79.6 (C-28), 55.4 (C-5), 53.7 (C-18), 47.8 (C-9), 42.1 (C-14), 40.2 (C-8),
39.5 (C-4), 39.4 (C-19), 39.3 (C-20), 39.0 (C-1), 37.9 (C-17), 36.9 (C-10), 35.2 (C-22), 32.9 (C-7), 30.2 (C-21),
28.7 (C-24), 27.8 (C-2), 26.1 (C-33), 25.8 (C-15), 23.6 (C-11), 23.5 (C-27), 23.0 (C-16), 21.3 (C-30), 18.6 (C-6),
18.3 (C-32), 17.2 (C-29), 16.6 (C-26), 16.3 (C-23), 15.9 (C-25),
−3.6 (C-31a), −4.7 (C-31b) ppm; MS (ASAP):
m/z (%) = 557.5.2 ([M-Me2BuSiOH + H]+, 14), 407.5 ([M-HOTf-Me2BuSiOH + H]+, 100).
(3β) 3-{[(1,1-Dimethylethyl)dimethylsilyl]oxy}-olean-12-en-28-methansulfonate (12)
◦
Compound 10 (5 g, 9.0 mmol) was dissolved in DCM (200 mL). At 0 C triethylamine (4 mL,
28.7 mmol) and methanesulfonyl chloride (0.76 mL, 9.87 mmol) were added. The reaction mixture was
stirred for an hour at room temperature and quenched by adding water (50 mL) and 2 M hydrochloric
acid (20 mL). The organic phase was separated. The aqueous phase was extracted with DCM (50 mL).
The combined organic extracts were washed with brine and dried over magnesium sulfate. Purification
by column chromatography (silica gel, hexane/EtOAc, 9:1) afforded 12 as a colorless crystalline solid
(5.31 g, 91%). m.p. = 71–74 ◦C; [α]2D0 = +66.4◦ (c 0.320, CHCl3); Rf = 0.25 (silica gel, hexane/EtOAc,
9:1); IR (KBr): 3444br, 2952s, 2930s, 2856s, 1638w, 1460m, 1386m, 1358s, 1254m, 1176s, 1100m, 1072m,
1004m, 954s, 838s, 776m, 530m cm−1; 1H NMR (500 MHz, CDCl3): δ = 5.23 (dd, J = 3.5, 3.5 Hz, 1H, H-12),
4.18 (d, J = 9.3 Hz, 1H, H-28a), 3.78 (d, J = 9.3 Hz, 1H, H-28b), 3.18 (dd, J = 11.1, 4.5 Hz, 1H, H-3), 2.98 (s,
3H, H-34), 2.06–1.84 (m, 3H, H-16a + H-11a + H-11b), 1.85–1.74 (m, 1H, H-2a), 1.70–1.43 (m, 11H, H-1a +
H-15a + H-19a + H-21a + H-6a + H-15b + H-7a + H-22a + H-9+ H-21b + H-6b), 1.42–1.33 (m, 4H, H-16a