Helvetica Chimica Acta Vol. 86 (2003)
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Part of the CHCl3-soluble fraction (15 g out of 177 g) was separated by column chromatography (silica gel)
(600 g, 230 400 mesh), gradient hexane/AcOEt ! AcOEt/MeOH 9 :1): seven fractions. Repeated column
chromatography (silica gel or Sephadex LH-20) of Fr. 2 (40% AcOEt/hexane), Fr. 3 (40% AcOEt/hexane),
Fr. 4 (50% AcOEt/hexane), and Fr. 5 and Fr. 6 (75% AcOEt/hexane) yielded betulinic acid [13] (26 mg) (Fr. 2),
6b-hydroxy-3,O-didehydrobetulinic acid [3] (106 mg) (Fr. 3), ursolic acid [2] (1.20 g) (Fr. 3 6), compound 1
(1.2 mg) (Fr. 3), 6b-hydroxybetulinic acid [6][7] (135 mg), 6a-hydroxy-3,O-didehydrobetulinic acid [3]
(35 mg), sumaresinolic acid [8] (23 mg) (Frs. 4 and 5), and 2,3-di-O-acetylmaslinic acid [9] (10 mg).
(6b)-4,6-Dihydroxy-3,4-secolup-20(29)-ene-3,28-dioic Acid 3,4-Lactone ( Viburolide; 1). Colorless solid.
1H-NMR(400 MHz, CDCl 3): Table. 13C-NMR(50 MHz, CDCl 3): Table. MS: 486 (13.8, M ), 468 (48.7), 395
(48), 259 (64.5), 201 (49.2), 187 (64.3), 175 (67.9), 147 (57), 133 (77.7), 107 (100), 81 (69), 69 (58.8), 43 (27.5), 41
(51.6). EI-HR-MS: 486.3335 (M , C30H46O5 ; calc. 486.3335).
Benzyl Betulinate ( Benzyl (3b)-3-Hydroxylup-20(29)-en-28-oate; 2). 1H-NMR(CDCl 3): 7.28 7.34
(m, PhCH2); 5.07, 5.13 (each d, J 12.3, PhCH2); 4.70 (d, J 2.0, HbÀC(29)); 4.57 (br. s, HaÀC(29)); 3.15
(dd, J 11.2, 5.1, HaÀC(3)); 3.00 (ddd, J 11.2, 11.2, 4.6, HbÀC(19)); 1.65 (br. s, Me(30)); 0.93, 0.92, 0.78, 0.74,
0.73 (5s, Me(23), Me(24), Me(25), Me(26), Me(27)). HR-FAB-MS: 547.4151 ([M H] , C37H55O3 ; calc.
547.4172).
Benzyl 20,29-Dihydrobetulinate ( Benzyl (3b)-3-Hydroxylupan-28-oate; 3). To a soln. of 2 (1.00 g) in
AcOH/dioxane 1:3 (20 ml) was added 10% Pt/C (200 mg). After the usual degassing, the mixture was heated to
508 and hydrogenated (H2, 1 atm) for 48 h. The mixture was filtered through a Celite pad and the residue washed
with CHCl3. The filtrate and washings were evaporated: essentially pure 3 (998 mg, quant.). Colorless solid.
M.p. 201 2028. 1H-NMR(400 MHz, CDCl 3): 7.28 7.34 (m, PhCH2); 5.10, 5.06 (each d, J 12.3, PhCH2); 3.16
(dd, J 11.2, 4.9, HaÀC(3)); 0.94, 0.90, 0.81, 0.79, 0.73 (5s, Me(23), Me(24), Me(25), Me(26), Me(27)); 0.733
(d, J 5.6) and 0.719 (d, J 5.8, Me(29), Me(30)). HR-FAB-MS: 549.4343 ([M H] , C37H57O3 ; calc.
549.4308).
Benzyl 3,O-Didehydro-20,29-dihydrobetulinate ( Benzyl 3-Oxolupan-28-oate; 4). To a soln. of 3 (500 mg)
in CH2Cl2 (15 ml) was added PCC (350 mg). After stirring for 16 h, the mixture was diluted with Et2O and
filtered through a Celite pad. The residue was washed several times with Et2O. The filtrate and washings were
evaporated, and the residue was chromatographed (silica gel (15 g, 230 400 mesh), AcOEt/hexane 1 :49): 4
(171 mg, 34.4%). Colorless needles (from MeOH). M.p. 148 1508. 1H-NMR(400 MHz, CDCl 3): 7.28 7.34
(m, PhCH2); 511, 5.06 (each d, J 12.3, PhCH2); 1.09, 1.00, 0.91, 0.89, 0.75 (5s, Me(23), Me(24), Me(25),
Me(26), Me(27)); 0.82, 0.72 (each d, J 6.8, Me(29), Me(30)). 13C-NMR(100 MHz, CDCl 3; key signals): 218.1
(s, C(3)); 176.0 (s, C(28)); 65.6 (t, PhCH2); 47.3 (s, C(4)). HR-FAB-MS: 547.4167 ([M H] , C37H55O3 ; calc.
547.4152).
4-Hydroxy-3,4-secolupane-3,28-dioic Acid 28-(Benzyl Ester) 3,4-Lactone (5). To a soln. of 4 (30 mg) in
CH2Cl2 (10 ml) was added mCPBA (50 mg) and NaHCO3 (30 mg). The mixture was stirred for 36 h at r.t. until a
white cloudy suspension formed. The latter was filtered through a Celite pad, and the residue was washed with
CH2Cl2. The combined filtrate and washings were washed with 10% NaHSO3 soln., dried (MgSO4), and
evaporated, and the residue chromatographed (silica gel (5.0 g, 230 400 mesh), CHCl3): 5 (20 mg, 65%).
Colorless solid. M.p. 192 1948 (MeOH). 1H-NMR(400 MHz, CDCl 3): 7.28 7.34 (m, PhCH2); 5.11, 5.06 (each
d, J 12.3, PhCH2); 2.59 (ddd, J 14.3, 12.6, 4.4, HaÀC(2)); 2.46 (ddd, J 14.3, 6.2, 3.3, HbÀC(2)); 2.24
(m, HÀC(19)); 1.44, 1.35, 1.02, 0.89, 0.76 (5s, Me(23), Me(24), Me(25), Me(26), Me(27)); 0.82, 0.72 (each
d, J 6.8, Me(29), Me(30)). 13C-NMR(100 MHz, CDCl 3): 175.9 (s, C(28)); 175.1 (s, C(3)); 86.1 (s, C(4)); 65.6
(t, PhCH2). HR-FAB-MS: 563.4115 ([M H] , C37H55O4; calc. 563.4101).
6-Dehydroxy-20,20-dihydroviburolide (4-Hydroxy-3,4-secolupane-3,28-dioic Acid 3,4-Lactone; 6). To a
soln. of 5 (10 mg) in AcOEt (10 ml) was added 10% Pd/C (10 mg). After the usual degassing, the mixture was
hydrogenated (H2, 1 atm) overnight. The mixture was filtered through a Celite pad and the residue washed with
CHCl3. The filtrate and washings were evaporated, and the residue was chromatographed (silica gel (5.0 g, 230
1
400 mesh), CHCl3): 6 (8.3 mg, 98%). Colorless solid. M.p. 216 2188 (MeOH). H-NMR(400 MHz, CDCl 3):
2.61 (ddd, J 14.1, 10.0, 4.4, HaÀC(2)); 2.47 (ddd, J 14.3, 6.1, 3.4, HbÀC(2)); 2.24 (m, HÀC(13), CH2(16),
HÀC(19)); 1.87 (br. dd, J 7.1, 3.6, HbÀC(22)); 1.82 (m, HbÀC(1)); 1.80 (m, HÀC(20)); 1.71 (m, HÀC(5));
1.70 (m, HbÀC(12)); 1.62 (m, CH2(21)); 1.55 (m, HaÀC(1)); 1.50 (m, HaÀC(11)); 1.48 (m, HaÀC(15)); 1.45
(s, Me(23)); 1.42 1.40 (m, 5 H, CH2(6), CH2(7), HÀC(9), HbÀC(11)); 1.39 (m, HÀC(18)); 1.36 (s, Me(24));
1.30 (m, HaÀC(22)); 1.22 (m, HbÀC(15)); 1.20 (m, HaÀC(12)); 1.05 (s, Me(25)); 0.96 (s, Me(26)); 0.94
(s, Me(27)); 0.84 (d, J 6.8, Me(29)); 0.74 (d, J 6.7, Me(30)). Key NOESY (CDCl3): HbÀC(2)/HbÀC(1),
HaÀC(2), Me(24), and Me(25), Me(23)/HÀC(5), HÀC(13)/HbÀC(12) and Me(26), Me(24)/Me(25), Me(27)/
HaÀC(16) and HÀC(18), Me(29)/HÀC(19) and Me(30), Me(30)/HÀC(19) and Me(29). Major HMBC: C(1)/