1.63 (3H, s, Me-27), 1.69 (3H, s, Me-26), 2.04 (3H, s, OAc), 3.60 (1H, td, J = 10.5, 10.5, 5.2, H-12α), 4.48 (1H, dd, J = 10.7,
5.7, H-3α), 5.16 (1H, t, J = 7.0, 7.0, H-24).
Oxidation of Monoacetate (9). Chromic anhydride (CrO , 3 g) was added with stirring to absolute pyridine (30 mL).
3
After the yellowish-orange complex formed, a solution of 9 (2.62 g) in pyridine (25 mL) was added dropwise with stirring at
room temperature for 10 h. The completion of the reaction was monitored using TLC. The reaction mixture was diluted with
CHCl and passed through a layer of silica gel. The solvent was distilled off at reduced pressure. The solid was dried to
3
constant weight (2.60 g) and chromatographed over a column of silica gel with elution by hexane:acetone (20:1) to afford 11
(2.15 g, 82.7%).
20
3β-Acetoxy-20S-hydroxydammar-24-en-12-one (11), C H O , amorph., [α]
IR spectrum (ν, cm ): 3416 (OH), 1722 (CH C=O), 1690 (C=O). PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.80 (3H,
+49.9° (c 0.6, CHCl ).
3
32 52
4
D
-1
3
3
s), 0.87 (3H, s), 0.88 (3H, s), 0.95 (3H, s), 1.12 (3H, s), 1.18 (3H, s), 1.62 (3H, s), 1.69 (3H, s), 2.05 (3H, s, OAc), 2.21 (1H,
t, J = 13.6, 13.6, H-11β), 2.28 (1H, dd, J = 14.4, 4.5, H-11α), 2.40 (1H, td, J = 10.6, 10.6, 7.0, H-17), 2.85 (1H, d, J = 10.3,
H-13), 4.48 (1H, dd, J = 11.6, 4.8, H-3α), 5.10 (1H, m, H-24).
3β,20S-Dihydroxydammar-24-en-12-one (2) was prepared by deacetylation of 11 by KOH (10%) in MeOH,
20
-1
C H O , mp 168-169°C (MeOH), [α]
+49.8° (c 1.0, CHCl ). IR spectrum (ν, cm ): 3608 (OH), 3416 (OH), 1690 (C=O).
3
30 50
3
D
PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.80 (3H, s, Me-30), 0.81 (3H, s, Me-29), 0.93 (3H, s, Me-19), 0.99 (3H, s,
3
Me-28), 1.11 (3H, s, Me-21), 1.18 (3H, s, Me-18), 1.62 (3H, s, Me-27), 1.69 (3H, s, Me-26), 2.21 (1H, t, J = 14.2, 14.2, H-11β),
2.28 (1H, dd, J = 14.5, 4.6, H-11α), 2.40 (1H, td, J = 10.5, 10.5, 7.0, H-17), 2.86 (1H, d, J = 10.2, H-13), 3.20 (1H, dd, J = 11.5,
4.8, H-3α), 5.10 (1H, m, H-24).
3,20-Di-O-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyl)dammar-24-en-3β,12β,20S-triol(6)wasprepared as before
[9], mp 120-125°C (hexane:acetone). PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.74 (3H, s), 0.85 (3H, s), 0.86 (3H,
3
s), 0.90 (3H, s), 0.96 (3H, s), 1.26 (3H, s), 1.60 (3H, s), 1.67 (3H, s), 2.00 (3H, s, OAc), 2.01 (3H, s, OAc), 2.02 (3H, s, OAc),
2.02 (3H, s, OAc), 2.03 (3H, s, OAc), 2.04 (3H, s, OAc), 2.05 (3H, s, OAc), 2.08 (3H, s, OAc), 3.07 (1H, dd, J = 11.6, 4.8,
H-3α), 3.53 (1H, td, J = 10.1, 10.1, 5.8, H-12α), 3.68 (2H, m, H-5′, H-5″), 4.11 (3H, m, H-6′, 2H-6″), 4.26 (1H, dd, J = 12.1,
5.8, H-6′, C-3), 4.53 (1H, d, J1′,2′ = 7.8, H-1′ of glucose C-3), 4.86 (1H, d, J1′′,2′′ = 7.8, H-1″ of glucose C-20), 4.90 (1H, dd,
J = 9.3, 7.8, H-2″ of glucose C-20), 5.02 (3H, m, H-2′, H-4′, H-4″), 5.08 (1H, m, H-24), 5.20 (1H, t, J = 9.6, 9.6, H-3″ of glucose
C-20), 5.23 (1H, t, J = 9.3, 9.3, H-3′ of glucose C-3).
Oxidation of Diglucoside 6. Chromic anhydride (500 mg) was added to cold absolute pyridine (5 mL) with stirring.
After the yellowish-orange complex formed, 6 (150 mg) in absolute pyridine (2 mL) was added dropwise with stirring at room
temperature for 10 h. The completeness of the reaction was monitored by TLC. The reaction mixture was diluted with CHCl
3
and passed over a layer of silica gel. The solvent was distilled at reduced pressure. The solid was dried to constant weight.
The dry solid (139 mg) was crystallized from MeOH to afford crystalline 7 (100 mg, 66.3%).
3,20-Di-O-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyl)-3β,20S-dihydroxydammar-24-en-12-one (7), C H O ,
58 86 21
20
-1
mp 232-234°C (MeOH), [α]
+11° (c 1.0, CHCl ). IR spectrum (ν, cm ): 1755 (CH C=O), 1704 (C=O). PMR spectrum
3 3
D
(500 MHz, CDCl , δ, ppm, J/Hz): 0.72 (3H, s, Me-30), 0.76 (3H, s, Me-29), 0.91 (3H, s, Me-28), 0.93 (3H, s, Me-19), 1.03 (3H,
3
s, Me-21), 1.19 (3H, s, Me-18), 1.61 (3H, s, Me-27), 1.66 (3H, s, Me-26), 1.98 (3H, s, OAc), 1.99 (3H, s, OAc), 2.00 (3H, s,
OAc), 2.02 (6H, s, 2OAc), 2.03 (3H, s, OAc), 2.05 (3H, s, OAc), 2.08 (3H, s, OAc), 2.45 (1H, td, J = 10.4, 10.4, 5.5, H-17),
3.01 (1H, d, J = 9.5, H-13), 3.06 (1H, dd, J = 11.8, 4.6, H-3α), 3.67 (2H, m, H-5′, H-5″), 4.08 (1H, dd, J = 12.1, 2.6, H-6″ of
glucose C-20), 4.11 (1H, dd, J = 12.1, 2.6, H-6′ of glucose C-3), 4.16 (1H, dd, J = 11.9, 6.8, H-6″ of glucose C-20), 4.24 (1H,
dd, J = 12.2, 5.6, H-6′ of glucose C-3), 4.53 (1H, d, J = 7.8, H-1′ of glucose C-3), 4.60 (1H, d, J = 7.8, H-1″ of glucose C-20),
4.93 (1H, dd, J = 9.5, 7.8, H-2″ of glucose C-20), 4.98 (1H, t, J = 9.8, 9.8, H-4″ of glucose C-20), 5.02 (1H, dd, J = 9.6, 8.1, H-2′
of glucose C-3), 5.03 (1H, t, J = 9.8, 9.8, H-4′ of glucose C-3), 5.04 (1H, t, J = 6.3, 6.3, H-24), 5.18 (1H, t, J = 9.3, 9.3, H-3″
of glucose C-20), 5.20 (1H, t, J 9.3, 9.3, H-3′ of glucose C-3).
Condensation of 2 with 2,3,4,6-Tetra-O-acetyl-α-D-glucopyranosylbromide (3) in the Presence of Ag O and
2
Molecular Sieves (4 Å).
Experiment 1. A mixture of 2 (1.24 g, 2.7 mmol), Ag O (1.17 g, 5 mmol), mol. sieves (1 g, 4 Å), and 3 (2.06 g,
2
5 mmol) in absolute CH Cl (25 mL) was stirred at room temperature until 3 disappeared (TLC monitoring). The mixture was
2
2
treated in two portions with more Ag O (2.34 g, 10 mmol) and 3 (4.11 g, 10 mmol), stirred for 6 h until 2 and 3 disappeared,
2
diluted with CHCl , and filtered toremove insoluble silver compounds andmolecular sieves. Thesolvent was removed in vacuo.
3
59