Synthesis of 20S-protopanaxadiol 20-O-β-D-glucopyranoside, a metabolite of Panax ginseng glycosides, and compounds related to it

Article abstract of DOI:10.1007/s10600-006-0179-2

A preparative semi-synthetic method was developed to prepare 20S-protopanaxadiol 20-O-β-Dglucopyranoside (1), a metabolite of Panax ginseng glycosides. The 20-O-?-D-glucopyranosides of 20S-hydroxydammar-24- en-3,12-dione, 3β,20S-dihydroxydammar-24-en-12-one, and 3β,12α, 20S-trihydroxydammar-24-ene were synthesized for the first time.

Full text of DOI:10.1007/s10600-006-0179-2

Chemistry of Natural Compounds, Vol. 42, No. 4, 2006
SYNTHESIS OF 20S-PROTOPANAXADIOL
20-O-β-D-GLUCOPYRANOSIDE, A METABOLITE
OF Panax ginseng GLYCOSIDES, AND
COMPOUNDS RELATED TO IT
L. N. Atopkina and V. A. Denisenko
UDC 547.917+547.918+547.597
A preparative semi-synthetic method was developed to prepare 20S-protopanaxadiol 20-O-β-D-
glucopyranoside (1), a metabolite of Panax ginseng glycosides. The 20-O-β-D-glucopyranosides of
20S-hydroxydammar-24-en-3,12-dione, 3β,20S-dihydroxydammar-24-en-12-one, and 3β,12α,20S-
trihydroxydammar-24-ene were synthesized for the first time.
Key words: dammarane triterpenoids; glycosylation; Betula; Panax ginseng C. A. Meyer; 20S-protopanaxadiol 20-O-
β-D-glucopyranoside; 20S-hydroxydammar-24-en-3,12-dione20-O-β-D-glucopyranoside;3β,20S-dihydroxydammar-24-en-12-
one 20-O-β-D-glucopyranoside; 3β,12α,20S-trihydroxydammar-24-ene 20-O-β-D-glucopyranoside.
Extract of Panax ginseng C. A. Meyer root, which is constantly attracting attention to itself owing to the breadth and
varietyofits biological activity, contains triterpene glycosides, which havebeen thesubject ofnumerousinvestigations. Ginseng
glycosides are transformed byintestinal microflora in the gastro-intestinal tract into compounds with new biological properties.
In the last few years, the properties and mechanism of action of one of the main metabolites of ginseng glycosides,
20S-protopanaxadiol 20-O-β-D-glucopyranoside (1) (compound K), have been studied more frequently [1-13]. Glucoside 1
inhibits the growth of tumor cells and induces their apoptosis [3, 9, 10], decreases the toxicity of antitumor preparations [4],
possesses antimetastatic and immunomodulating activity [2, 11], and exhibits antiallergic [12] and anti-inflammatory [13]
properties. In most of these investigations, 1 was prepared by treating ginseng extract or the enriched glycoside fraction with
enzymes, bacteria, or intestinal microflora followed by chromatographic separation of the products of enzymatic hydrolysis.
Wepreviouslyprepared 1asoneofthecondensation productsof20S-protopanaxadiol(dammar-24-en-3β,12β,20S-triol)
(2)with 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosylbromide(α-acetobromoglucose) (3)underKoenig—Knorrreactionconditions
[14, 15]. Because all three hydroxyls of 3 were glycosylated, the main drawback was the lack of regioselectivity, which led to
the formation of a complicated and difficultlyseparated mixture of mono- and diglucosides. Regioselective glycosylation of the
3,12-diacetate of20S-protopanaxadiol (4) with one free hydroxyl on C-20 was unsuccessful [14], apparentlybecause the 20-OH
was sterically shielded by the 12β-OAc group.
The present article is a continuation of investigations on the synthesis of glycosides based on tetracyclic dammarane
triterpenoids. The goal was to develop a preparative semi-synthetic method for preparing 20S-protopanaxadiol 20-O-β-D-
glucopyranoside (1).
An attempt to synthesize 1 through regio- and stereoselective glycosylation of the tertiary hydroxyl on C-20 of
20S-hydroxydammar-24-en-3,12-dione (5) with subsequent reduction of both ketones on C-3 and C-12 into the glycosylation
product (6) did not give the desired result. Reaction of 5 with 3 in the presence of Ag O and 4Å molecular sieves in
2
dichloroethane gave the tetraacetateofthe diketone 20-O-β-D-glucopyranoside (6) (47% yield), reduction ofwhich with NaBH
4
in isopropanolselectivelyreducedonlyoneketoneon C-3andformedthetetraacetateof3β,20S-dihydroxydammar-24-en-12-one
20-O-β-D-glucopyranoside (7).
Pacific Institute of Bioorganic Chemistry, Far-East Division, Russian Academy of Sciences, 690022, Vladivostok, pr.
100 Let Vladivostoku, 159, fax 7-(4232)314050, e-mail: atopkina@mail.ru. Translated from Khimiya Prirodnykh Soedinenii,
No. 4, pp. 364-369, July-August, 2006. Original article submitted June 9, 2006.
0009-3130/06/4204-0452 ©2006 Springer Science+Business Media, Inc.
452

OR
OR
2
OR
3
R O
2
O
O
20
12
3
O
R O
1
R O
1
7, 8, 10
1, 2, 4, 17 - 21
5, 6, 9
OR
OR
3
OH
2
R O
2
R O
1
HO
R O
1
O
HO
14 - 16
11 - 13
22
AcOH C
AcOH C
2
HO HC
2
2
O
O
O
AcO
AcO
AcO
AcO
HO
HO
= GlcAc
= Glc
4
AcO
AcO
OH
Br
3
1:
5:
2:
4:
R = H; R = GlcAc4; R1 = H, R2 = GlcAc4; R1 = OAc, R2 = GlcAc4; R = Glc
R1 = R2 = H, R3 = Glc; R1 = R2 = R3 = H; R1 = R2 = Ac, R3 = H
6: 7: 8:
9:
10:
13:
16:
19:
11:
12:
15:
R1 = H, R2 = Glc;
R1 = R2 = Ac, R3 = GlcAc4;
17:
R1 = R2 = H, R3 = Glc;
R1 = Ac, R2 = H, R3 = GlcAc4
R1 = GlcAc4, R2 = H
14:
R1 = R2 = H;
18:
R1 = R3 = H, R2 = GlcAc4
R1 = H, R2 = GlcAc4;
R1 = R2 = H, R3 = GlcAc4;
20:
21:
R1 = R3 = H; R2 = Glc
R1 = R2 = Ac, R3 = GlcAc4;
R1 = Ac, R2 = GlcAc4; R3 = H;
-1
-1
7
The IR spectrum of contained absorption bands for carbonyl at 1700 cm and free hydroxyl at 3612 cm . The PMR
7
spectrum of exhibited a signal for the axial proton on C-3 at δ 3.19 ppm, which underwent a low-field shift and appeared at
13
8
7
6
δ 4.47 ppm in the PMR spectrum of , which was obtained by acetylation of . Compared with the C NMR spectrum of ,
7
that of had one of the two signals for carbonyl C atoms at δ 211.9 ppm, belonging to C-12, whereas the signal for the C-3
7
carbonyl at δ 216.9 ppm disappeared. Deacetylation of by MeONa (0.1 N) in MeOH gave free 3β,20S-dihydroxydammar-24-
10
en-12-one 20-O-β-D-glucopyranoside ( ), the spectroscopy, elemental analysis, and physicochemical propertiesofwhich were
identical to the general prosapogenin of natural dammarane glycosides with a 12-ketone in the aglycon [16].
9
Reduction of free 20S-hydroxydammar-24-en-3,12-dione 20-O-β-D-glucopyranoside ( ), obtained after removing the
6
11
protecting groups of , formed 3β,12α,20S-trihydroxydammar-24-ene (the 12-epimer of 20S-protopanaxadiol) ( ) instead of
1
11
the desired monoglucoside ( ). Acetylation of byAc O in pyridine at room temperature gave the pentaacetate of3β,12α,20S-
2
12
13
Therefore, the optimal version of the preparative synthesis of was, in our opinion, glycosylation of 12β,20S-
14 15
trihydroxydammar-24-ene 20-O-β-D-glucopyranoside ( ); at 90°C, its hexaacetate ( ).
1
3
dihdyroxydammar-24-en-3-one ( ) by with subsequent reduction by NaBH in isopropanol of the reaction products ( and
4
16
17
18
to simplify the chromatographic separation of and , the resulting mixture of and was treated with Ac O in pyridine
) to form a mixture of the two tetraacetates 20S-protopanaxadiol 20- and 12-O-β-D-glucopyranosides ( and ). In order
17 18 17 18
2
18
at 90°C for 2-3 h. Because the tertiary OH on C-20 in
hexaacetate of 20S-protopanaxadiol 20-O-β-D-glucopyranoside ( ) and the pentaacetate of 20S-protopanaxadiol 12-O-β-D-
20 19 20
was not acetylated, the treatment produced a mixture of the
19
glucopyranoside ( ), the chromatographic separation of which was facile. Deacetylation of and was effected using KOH
21
1
solution (10%) in MeOH and produced free and , respectively, in quantitative yields.
453

TABLE 1. 13C NMR Chemical Shifts of 1, 5-7, 9-12, and 21 (δ, ppm, TMS = 0)
C atom
1
5
6
7
9
10
11
12
21
1
2
39.19
28.05
77.83
39.34
56.14
18.55
34.95
39.86
50.09
37.14
30.56
69.96
49.30
51.21
30.74
26.42
51.39
15.81
16.14
83.08
22.13
35.96
22.98
125.75
130.69
25.54
17.54
28.47
16.14
17.18
39.03
33.77
216.75
47.37
55.13
19.66
33.27
40.12
52.74
37.13
39.27
213.22
56.27
54.79
30.86
24.61
45.90
15.57
15.53
73.17
26.38
37.96
22.46
124.80
131.57
25.73
17.68
26.57
21.05
17.34
39.26
33.79
216.91
47.36
55.17
19.77
33.76
40.45
53.88
37.30
39.87
211.19
55.62
56.25
31.69
23.77
41.07
15.24
15.83
82.17
23.45
38.77
23.53
124.26
131.68
25.65
17.67
26.70
20.99
16.73
170.58
170.17
169.55
169.06
38.60
27.16
78.61
38.93
55.76
18.36
34.40
40.50
54.57
37.63
39.76
211.88
55.53
56.25
31.67
23.73
40.99
15.56
16.13
82.18
23.33
38.80
23.52
124.28
131.63
25.67
17.67
27.98
15.27
16.77
170.63
170.22
169.55
169.04
39.16
33.97
215.97
47.26
54.79
19.86
33.83
40.55
53.94
37.26
39.16
210.76
56.41
56.16
32.23
24.46
42.48
15.41
15.78
81.25
22.44
40.07
23.90
125.67
130.80
25.71
17.70
26.63
21.00
16.80
38.82
27.89
77.53
39.31
55.94
18.64
34.61
40.70
54.73
37.67
39.93
211.06
56.24
56.05
32.12
24.39
42.38
15.77
16.14
81.15
22.26
40.38
23.76
125.56
130.63
25.57
17.56
28.38
15.98
16.79
39.26
28.08
77.86
39.40
56.40
18.62
35.80
40.71
45.98
37.00
30.33
67.51
45.80
49.21
31.77
25.02
46.60
15.40
16.45
82.87
21.58
37.00
22.77
126.07
130.58
25.57
17.60
28.48
16.17
19.84
38.51
24.05
80.87
37.91
55.96
18.17
35.21
40.40
45.28
36.72
29.25
68.22
45.35
48.97
31.52
23.70
45.48
15.08
16.25
83.44
22.59
37.08
23.33
124.55
131.55
25.71
17.79
28.01
16.61
19.18
170.95
170.74
170.32
169.54
169.47
21.35
20.88
20.72
20.65
20.65
38.83
28.02
77.79
39.32
56.13
18.47
34.77
39.76
50.06
37.25
27.71
77.38
46.54
52.01
31.10
26.96
53.91
15.50
16.14
72.82
26.68
36.29
22.76
126.37
130.36
25.59
17.50
28.49
16.06
17.14
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
CH3CO
CH3CO
20.84
20.60
20.60
20.58
20.82
20.61
20.61
20.61
13
The structures ofall prepared compounds wereprovedbyIR, PMR, and C NMR spectroscopy. Doublets for anomeric
protons of the sugars of acetylated glucosides (6-8, 12, 13, 19, and 20) appeared in PMR spectra in CDCl at δ 4.60-4.73 ppm
3
(J
= 7.8-8.0 Hz). Doublets for anomeric glucose protons in PMR spectra in C D N of free glucosides (1, 9-11, and 21) were
5 5
1′,2′
observed at δ 5.09-5.27 ppm (J
= 7.6-7.8 Hz). Chemical shifts and spin—spin coupling constants for anomeric glucose
1′,2′
protons were consistent with the trans-configuration of the glycoside bond in all glycosides. The site of attachment of the
13
glucose was confirmed by comparing C NMR spectra of 1, 5-7, 9-12, and 21 (Tables 1 and 2).
454

TABLE 2. 13C NMR Chemical Shifts of Sugars in 1, 6, 7, 9-12, and 21 (δ, ppm, TMS = 0)
C atom
Compound
1′
2′
3′
4′
5′
6′
1
6
7
98.05
94.61
94.57
98.42
98.31
98.19
95.15
100.23
74.92
72.01
71.93
75.67
75.53
75.11
71.90
75.08
79.10
73.22
73.21
79.20
79.06
78.77
72.59
78.23
71.45
69.00
68.94
71.83
71.72
71.78
68.83
70.99
78.07
71.59
71.53
77.98
77.83
77.47
71.65
78.18
62.68
62.66
62.64
62.88
62.78
62.96
62.47
62.40
9
10
11
12
21
EXPERIMENTAL
13
PMR and C NMR spectra of 1, 9-11, and 21 were recorded on a Bruker Avance-500 spectrometer at working
1
13
frequency 500 MHz for H and 125 MHz for C at 30°C in C D N; for 5-8, 12, 13, 19, and 20, in CDCl . Chemical shifts are
5
13
5
3
given on the δ scale relative to TMS. The multiplicity of the C signals was established using DEPT-135 experiments by the
standard method. Homonuclear 2D proton—proton correlation COSY-45 spectra and 2D heteronuclear HSQC and HMBC
n
correlation spectra were also recorded using standard methods. HMBC experiments were optimized for J ≈ 10 Hz.
HC
IR spectra were recorded on a Bruker Vector 22 spectrophotometer in CHCl solution. Optical rotation was determined on a
3
Perkin—Elmer 141 instrument in 10-cm cuvettes at 20°C. Melting points were measured on a Boetius stage. Column
chromatography was performed over KSK silica gel (120-150 mesh) using solvent systems hexane:acetone (15:1, 15:1→6:1,
10:1). The purity of compounds was monitored using TLC on Sorbfil plates (Russia) and hexane:acetone (3:2) and
C H :CHCl :CH OH (6:4:1, 3:2:1, 2:1:1). Development used H SO (10%) in ethanol with heating at 100-200°C. Elemental
6
6
3
3
2
4
analyses of all newly prepared compounds agreed with those calculated.
Betulafolientriol (3α,12β,20S-trihydroxydammar-24-ene, 22) was isolated from an extract of Betula pendula leaves
according to the literature method [14, 15], mp 195-196°C (acetone).
12β,20S-Dihydroxydammar-24-ene-3-one (14) was prepared on [14, 15], mp 196-198°C (acetone).
Oxidation of Betulafolientriol (22) into Diketone 5. Cooled absolute pyridine (25 mL) was stirred and treated with
CrO (3.4 g). After the yellowish-orange complex formed, a solution of 22 (1.67 g) in pyridine (12 mL) was added. The
3
mixture was stirred at room temperature for 20 h. The course of the reaction was monitored byTLC. The reaction mixture was
diluted with CHCl and passed through a layer of silica gel. Solvent was evaporated at reduced pressure. The solid was dried
3
and chromatographed over a column of silica gel with elution by hexane:acetone (15:1) to afford diketone 5 (1.17 g, 70.3%)
and monoketone 14 (0.33 g, 19.7%).
20
20S-Hydroxydammar-24-en-3,12-dione (5), mp 151-152°C (MeOH), [α]
+63.3° (c 0.9, CHCl ), lit. mp 152-
3
D
153.5°C [17]. PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.812 (3H, s, Me-30), 1.039 (3H, s, Me-19), 1.072 (3H, s,
3
Me-29), 1.106 (3H, s, Me-28), 1.119 (3H, s, Me-21), 1.228 (3H, s, Me-18), 1.621 (3H, s, Me-27), 1.688 (3H, s, Me-26), 2.29
(2H, d, J = 8.6, 2H-11), 2.49 (3H, m, 2H-2, H-17), 2.90 (1H, d, J = 10.2, H-13), 5.11 (1H, t, J = 7.1, 7.1, H-24).
Condensation of 5 with 3 in the Presence of Silver Oxide and 4Å Molecular Sieves. A mixture of 5 (2.4 g,
5 mmol), 3 (4.11 g, 10 mmol), Ag O (2.34 g, 10 mmol), and 4Å molecular sieves (2 g) in dichloroethane (30 mL) was stirred
2
at room temperature for 1 h; treated twice at 1-h intervals with additional portions of 3 (2.06 g, 5 mmol), Ag O (1.17 g,
2
5 mmol), and 4Å molecular sieves (1 g); stirred for 3 h until 3 disappeared in the reaction mixture (TLC monitoring); and
filtered to remove insoluble silver compounds and molecular sieves. Solvent was removed at reduced pressure. The solid was
dried, washed three times with hot water, dried, and chromatographed over a silica-gel column with elution by hexane:acetone
(15:1→6;1) to isolate diketone 5 (0.97 g, 40.4%) and glycoside 6 (1.86 g, 47.2%).
20S-(2′,3′,4′,6′-Tetra-O-acetyl-β-D-glucopyransoyloxy)dammar-24-en-3,12-dione (6). C H O , mp200-202°C
44 66 12
20
-1
(EtOH), [α]
+32.6° (c 0.7, CHCl ). IR spectrum (ν, cm ): 1704 (C=O), 1753 (CH C=O). PMR spectrum (500 MHz,
3 3
D
CDCl , δ, ppm, J/Hz): 0.741 (3H, s, Me-30), 1.034 (3H, s, Me-21), 1.038 (3H, s, Me-19), 1.067 (3H, s, Me-29), 1.096 (3H, s,
3
455

Me-28), 1.251 (3H, s, Me-18), 1.612 (3H, s, Me-27), 1.657 (3H, s, Me-26), 1.988 (6H, s, 2OAc), 2.028 (3H, s, OAc), 2.056 (3H,
s, OAc), 2.15 (1H, dd, J = 12.6, 4.1, H-11α), 2.23 (1H, t, J = 12.9, 12.9, H-11β), 2.47 (3H, m, 2H-2, H-17), 3.06 (1H, d, J = 9.7,
H-13), 3.66 (1H, ddd, J = 10.0, 6.8, 2.4, H-5′), 4.09 (1H, dd, J = 12.1, 2.5, H-6′), 4.16 (1H, dd, J = 12.1, 6.8, H-6′), 4.61 (1H,
d, J
= 7.8, H-1′), 4.94 (1H, dd, J = 9.5, 7.8, H-2′), 4.98 (1H, t, J = 9.6, 9.6, H-4′), 5.05 (1H, t, J = 7.1, 7.1, H-24), 5.19 (1H,
1′,2′
t, J = 9.5, 9.5, H-3′).
Reduction of 6. A suspension of NaBH (180 mg) in isopropanol (10 mL) was treated at room terperature with a
4
solution of 6 (680 mg) in isopropanol (35 mL), stirred for 30 min until the starting 5 disappeared in the reaction mixture (TLC
monitoring), treated dropwise with dilute (1:1) acetic acid, and poured onto ice. The resulting solid was filtered off and dried
to afford 7 (570 mg, 83.6%).
3β-Hydroxy-20S-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyloxy)dammar-24-en-12-one (7). C H O , mp199-
44 68 12
20
-1
200.5°C (MeOH), [α]
+21.3° (c 0.7, CHCl ). IR spectrum (ν, cm ): 1701 (C=O), 1752 (CH C=O), 3612 (OH).
3 3
D
PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.724 (3H, s, Me-30), 0.796 (3H, s, Me-29), 0.935 (3H, s, Me-19), 0.981 (3H,
3
s, Me-28), 1.028 (3H, s, Me-21), 1.197 (3H, s, Me-18), 1.604 (3H, s, Me-27), 1.651 (3H, s, Me-26), 1.977 (3H, s, OAc), 1.981
(3H, s, OAc), 2.020 (3H, s, OAc), 2.049 (3H, s, OAc), 2.15 (2H, d, J = 8.6, 2H-11), 2.45 (1H, td, J = 10.4, 10.4, 5.4, H-17), 3.01
(1H, d, J = 9.6, H-13), 3.19 (1H, dd, J = 11.1, 4.7, H-3α), 3.66 (1H, ddd, J = 10.1, 6.9, 2.5, H-5′), 4.07 (1H, dd, J = 12.1, 2.5,
H-6′), 4.15 (1H, dd, J = 12.1, 6.9, H-6′), 4.60 (1H, d, J
9.4, H-4′), 5.04 (1H, t, J = 7.0, 7.0, H-24), 5.18 (1H, t, J = 9.4, 9.4, H-3′).
= 7.9, H-1′), 4.93 (1H, dd, J = 9.4, 7.9, H-2′), 4.98 (1H, t, J = 9.4,
1′,2′
Acetylation of 7. Glucoside 7 (200 mg) in absolute pyridine (2 mL) was treated with absolute acetic anhydride (1 mL)
and left at room temperature for 1 d. The reaction mixture was poured into a cylinder with ground ice. The resulting precipitate
was filtered off, washed with icewater, and dried to afford 8.
3β-Acetoxy-20S-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyloxy)dammar-24-en-12-one(8). C H O , mp241-
46 70 13
20
-1
243°C (EtOH), lit. mp [16] 242-244°C, [α]
+25.4° (c 0.6, CHCl ). IR spectrum (ν, cm ): 1708 (C=O), 1730 (CH C=O),
3 3
D
1753 (CH C=O). PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.727 (3H, s), 0.864 (3H, s), 0.876 (3H, s), 0.966 (3H, s),
3
3
1.033 (3H, s), 1.204 (3H, s), 1.609 (3H, s), 1.657 (3H, s), 1.974 (3H, s, OAc), 1.980 (3H, s, OAc), 2.019 (3H, s, OAc), 2.038
(3H, s, OAc), 2.048 (3H, s, OAc), 2.15 (2H, m, 2H-11), 2.46 (1H, td, J = 10.2, 10.2, 5.5, H-17), 3.01 (1H, d, J = 9.6, H-13), 3.66
(1H, ddd, J = 10.1, 6.6, 2.5, H-5′), 4.08 (1H, dd, J = 12.1, 2.5, H-6′), 4.15 (1H, dd, J = 12.1, 6.6, H-6′), 4.47 (1H, dd, J = 11.2,
4.9, H-3α), 4.60 (1H, d, J
7.1, H-24), 5.18 (1H, t, J = 9.3, 9.3, H-3′).
= 7.7, H-1′), 4.93 (1H, dd, J = 9.6, 8.0, H-2′), 4.98 (1H, t, J = 9.6, 9.6, H-4′), 5.04 (1H, t, J = 7.1,
1′,2′
Glucosides 6 and 7 were deacetylated using MeONa (0.1 N) in MeOH at room temperature for 1-2 h.
20
20-O-β-D-Glucopyranosyl-20S-hydroxydammar-24-en-3,12-dione (9). C H O , amorph., [α]
+30.5° (c 0.9,
C H N). PMR spectrum (500 MHz, C D N, δ, ppm, J/Hz): 0.877 (3H, s, Me-30), 0.889 (3H, s, Me-19), 1.044 (3H, s, Me-29),
36 58
8
D
5
5
5 5
1.133 (3H, s, Me-28), 1.333 (3H, s, Me-18), 1.592 (3H, s, Me-21), 1.624 (3H, s, Me-26), 1.640 (3H, s, Me-27), 3.67 (1H, d,
J = 9.3, H-13), 3.92 (1H, m, H-5′), 4.03 (1H, t, J = 8.2, 8.2, H-2′), 4.24 (2H, m, H-3′, H-4′), 4.36 (1H, dd, J = 11.5, 5.3, H-6′),
4.51 (1H, dd, J = 11.8, 2.8, H-6′), 5.12 (1H, d, J
= 7.6, H-1′), 5.22 (1H, m, H-24).
1′,2′
20
20-O-β-D-Glucopyranosyl-3β,20S-dihydroxydammar-24-en-12-one (10). C H O , amorph., [α]
+27.3°
36 60
8
D
(c 1.2, C H N). PMR spectrum (500 MHz, C D N, δ, ppm, J/Hz): 0.891 (3H, s, Me-19), 0.910 (3H, s, Me-30), 1.041 (3H, s,
5
5
5 5
Me-29), 1.225 (3H, s, Me-28), 1.340 (3H, s, Me-18), 1.594 (3H, s, Me-21), 1.621 (3H, s, Me-26), 1.640 (3H, s, Me-27), 2.96
(1H, td, J = 9.4, 9.4, 4.6, H-17), 3.41 (1H, dd, J = 10.7, 5.4, H-3α), 3.65 (1H, d, J = 9.5, H-13), 3.92 (1H, m, H-5′), 4.03 (1H,
t, J = 8.1, 8.1, H-2′), 4.23 (1H, t, J = 8.8, 8.8, H-4′), 4.26 (1H, t, J = 8.8, 8.8, H-3′), 4.36 (1H, dd, J = 11.5, 5.1, H-6′), 4.51
(1H, dd, J = 11.5, 2.7, H-6′), 5.12 (1H, d, J
= 7.7, H-1′), 5.22 (1H, t, J = 7.1, 7.1, H-24).
1′,2′
Reduction of 9. A suspension of NaBH (70 mg) in isopropanol (10 mL) at room temperature was treated dropwise
4
with a solution of 9 (35 mg) in isorpopanol (7 mL) and stirred for 20 h. The excess of NaBH was destroyed byadding dropwise
4
dilute (1:1) acetic acid. The reaction mixture was poured onto ice and extracted with CHCl . The solvent was distilled off.
3
The solid was dried to afford 11 (30 mg, 85.3%).
20
20-O-β-D-Glucopyranosyl-3β,12α,20S-trihydroxydammar-24-ene (11). C H O , amorph., [α]
D
+24° (c 1.5,
36 62
8
C H N). PMR spectrum (500 MHz, C D N, δ, ppm, J/Hz): 0.934 (3H, s, Me-19), 1.007 (3H, s, Me-18), 1.078 (3H, s, Me-29),
5
5
5 5
1.252 (3H, s, Me-28), 1.432 (3H, s, Me-30), 1.604 (3H, s, Me-21), 1.643 (3H, s, Me-26), 1.655 (3H, s, Me-27), 3.43 (1H, dd,
J = 11.4, 4.7, H-3α), 3.92 (1H, ddd, J = 9.4, 5.2, 2.7, H-5′), 3.99 (1H, t, J = 8.0, 8.0, H-2′), 4.20 (1H, t, J = 8.9, 8.9, H-4′), 4.24
(1H, t, J = 8.9, 8.9, H-3′), 4.35 (1H, dd, J = 11.4, 5.5, H-6′), 4.53 (1H, dd, J = 11.4, 2.7, H-6′), 4.88 (1H, dd, J = 5.7, 2.9, H-12β),
5.09 (1H, d, J
= 7.7, H-1′), 5.29 (1H, t, J = 7.1, 7.1, H-24).
1′,2′
456

Acetylation of 11. a) Glucoside 11 (30 mg) in absolute pyridine (1 mL) was treated with absolute acetic anhdyride
(0.7 mL) and left at room temperatrure for 1 d. The reaction mixture was poured into a cylinder with ground ice and extracted
with CHCl . The solvent was distilled off. The solid was dried to afford 12.
3
b) A solution of 11 (30 mg) in absolute pyridine (1 mL) was treated with absolute acetic anhdyride (0.7 mL) and left
at 80-90°C for 5 h. The reaction mixture was poured into a cylinder with ground ice. The resulting precipitate was filtered off,
washed with icewater, dried, and crystallized from EtOH to afford 13.
3β-Acetoxy-12α-hydroxy-20S-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyloxy)dammar-24-ene (12). C H O ,
46 72 13
20
-1
mp 193-195°C (EtOH), [α]
+48.5° (c 0.4, CHCl ). IR spectrum (ν, cm ): 1726 (CH C=O), 1753 (CH C=O), 3469 (OH).
3 3 3
D
PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.852 (3H, s, Me-29), 0.856 (3H, s, Me-28), 0.895 (3H, s, Me-19), 0.939 (3H,
3
s, Me-18), 1.077 (3H, s, Me-30), 1.198 (3H, s, Me-21), 1.598 (3H, s, Me-27), 1.665 (3H, s, Me-26), 1.990 (3H, s, OAc), 2.017
(3H, s, OAc), 2.043 (3H, s, OAc), 2.046 (3H, s, OAc), 2.064 (3H, s, OAc), 3.65 (1H, ddd, J = 10.1, 5.7, 2.4, H-5′), 4.08 (1H,
dd, J = 12.2, 2.4, H-6′), 4.14 (1H, dd, J = 12.1, 5.7, H-6′), 4.28 (1H, m, H-12β), 4.49 (1H, dd, J = 11.1, 5.3, H-3α), 4.69 (1H,
d, J
= 7.9, H-1′), 4.92 (1H, dd, J = 9.8, 7.9, H-2′), 5.00 (1H, t, J = 9.8, 9.8, H-4′), 5.04 (1H, t, J = 6.9, 6.9, H-24), 5.23 (1H,
1′,2′
t, J = 9.6, 9.6, H-3′).
3β,12α-Diacetoxy-20S-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyloxy)dammar-24-ene (13).
C H O ,
48 74 14
20
-1
mp 174-176°C (EtOH), [α]
+49.9° (c 0.4, CHCl ). IR spectrum (ν, cm ): 1726 (CH C=O), 1753 (CH C=O).
3 3 3
D
PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.854 (3H, s, Me-29), 0.862 (3H, s, Me-28), 0.886 (3H, s, Me-19), 0.974 (3H,
3
s, Me-18), 1.036 (3H, s, Me-30), 1.170 (3H, s, Me-21), 1.599 (3H, s, Me-27), 1.653 (3H, s, Me-26), 1.980 (3H, s, OAc), 2.014
(3H, s, OAc), 2.038 (3H, s, OAc), 2.041 (3H, s, OAc), 2.046 (3H, s, OAc), 2.074 (3H, s, OAc), 3.65 (1H, ddd, J = 10.1, 6.6,
2.5, H-5′), 4.08 (1H, dd, J = 12.1, 2.5, H-6′), 4.15 (1H, dd, J = 12.1, 6.6, H-6′), 4.47 (1H, dd, 1H, J = 10.4, 5.8, H-3α), 4.63
(1H, d, J
= 8.0, H-1′), 4.95 (1H, dd, J = 9.6, 8.0, H-2′), 4.98 (1H, t, J = 9.6, 9.6, H-4′), 5.03 (1H, t, J = 6.9, 6.9, H-24), 5.16
1′,2′
(1H, dd, J = 6.0, 3.0, H-12β), 5.19 (1H, t, J = 9.6, 9.6, H-3′).
Synthesis of 20S-Protopanaxadiol 20- and 12-O-β-D-Glucopyranosides (1 and 21). A mixture of 14 (1.15 g,
2.5 mmol), 3 (2.06 g, 5 mmol), Ag O (1.17 g, 5 mmol), and 4Å molecular sieves (1 g) in dichloroethane (30 mL) was stirred
2
at room temperature for 1 h; treated twice at 1-h intervals with additional portions of 3 (2.06 g, 5 mmol), Ag O (1.17 g,
2
5 mmol), and 4Å molecular sieves (1 g); stirred for 3 h until 3 disappeared in the reaction mixture (TLC monitoring); and
filtered to remove insoluble silver compounds and molecular sieves. Solvent was removed at reduced pressure. The solid was
dried, washed three times with hot water to remove the excess of glucose derivatives, and dried to afford the crude product
(1.9 g). A suspension of NaBH (200 mg) in isopropanol (15 mL) was treated dropwise with a solution of the crude product
4
(1.9 g) in isopropanol (10 mL) and stirred at room temperature for 3 h until the reaction was complete (TLC monitoring). The
excess of NaBH was decomposed by adding dropwise dilute (1:1) acetic acid. The reaction mixture was poured into a cylinder
4
with ground ice and extracted with CHCl . The extracts were evaporated and dried. The solid was dissolved in absolute
3
pyridine (10 mL), treated with acetic anhydride (7 mL), held at 90°C for 3 h (TLC monitoring), and poured onto ice. The
resulting precipitate was filtered off, washed with cold water, and dried. The solid (1.48 g) was chromatographed over a
silica-gel column with elution by hexane:acetone (10:1) to afford 19 (0.32 g, 14.5%) and 20 (0.98 g, 45.7%).
3β,12β-Diacetoxy-20S-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyloxy)dammar-24-ene (19), mp 176-177°C
(EtOH), lit. mp [1] 177-178°C. PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.849 (6H, s), 0.878 (3H, s), 0.927 (3H, s),
3
0.968 (3H, s), 1.177 (3H, s), 1.595 (3H, s), 1.653 (3H, s), 1.977 (3H, s, OAc), 1.991 (3H, s, OAc), 2.023 (3H, s, OAc), 2.035
(3H, s, OAc), 2.049 (3H, s, OAc), 2.056 (3H, s, OAc), 3.65 (1H, ddd, J = 10.2, 5.3, 3.2, H-5′), 4.10 (1H, dd, J = 12.0, 3.2, H-6′),
4.13 (1H, dd, J = 12.2, 5.5, H-6′), 4.48 (1H, dd, J = 11.0, 5.00, H-3α), 4.67 (1H, d, J
10.7, 5.2, H-12α), 4.92 (1H, dd, J = 9.7, 8.0, H-2′), 4.99 (1H, t, J = 9.7, 9.7, H-4′), 5.01 (1H, m, H-24), 5.19 (1H, t, J = 9.5, 9.5,
= 7.7, H-1′), 4.83 (1H, td, J = 10.7,
1′,2′
H-3′).
3β-Acetoxy-20S-hydroxy-12β-(2′,3′,4′,6′-tetra-O-acetyl-β-D-glucopyranosyloxy)dammar-24-ene (20), mp 137-
140°C (EtOH), lit. mp [15] 137-140°C. PMR spectrum (500 MHz, CDCl , δ, ppm, J/Hz): 0.867 (6H, s), 0.886 (3H, s), 0.898
3
(3H, s), 0.970 (3H, s), 1.110 (3H, s), 1.643 (3H, s), 1.706 (3H, s), 1.989 (3H, s, OAc), 2.014 (3H, s, OAc), 2.034 (3H, s, OAc),
2.061 (3H, s, OAc), 2.093 (3H, s, OAc), 3.67 (1H, dt, J = 10.0, 3.7, 3.7, H-5′), 3.81 (1H, td, J = 10.7, 10.7, 5.00, H-12α), 3.95
(1H, s, OH), 4.21 (2H, d, J = 4.00, 2H-6′), 4.49 (1H, dd, J = 11.5, 4.7, H-3α), 4.73 (1H, d, J
= 8.0, H-1′), 4.91 (1H, dd,
1′,2′
J = 9.7, 8.0, H-2 ), 5.09 (1H, t, J = 9.7, 9.7, H-4′), 5.17 (1H, m, H-24), 5.21 (1H, t, J = 9.5, 9.5, H-3′).
Compounds 19 and 20 were deacetylated by KOH (10%) in methanol at room temperature.
457

20
20-O-β-D-Glucopyranosyl-3β,12β,20S-trihydroxydammar-24-ene (1). C H O ·1.5 H O, amorph., [α]
+31°
(c 0.5, C H N). PMR spectrum (500 MHz, C D N, δ, ppm, J/Hz): 0.900 (3H, s, Me-19), 0.956 (3H, s, Me-30), 0.997 (3H, s,
36 62
8
2
D
5
5
5 5
Me-18), 1.049 (3H, s, Me-29), 1.239 (3H, s, Me-28), 1.604 (3H, s, Me-27), 1.607 (3H, s, Me-26), 1.640 (3H, s, Me-21), 3.43
(1H, m, H-3α), 3.94 (1H, ddd, J = 9.15, 5.53, 2.64, H-5′), 4.02 (1H, t, J = 8.2, 8.2, H-2′), 4.18 (1H, t, J = 8.9, 8.9, H-4′), 4.18
(1H, m, H-12α), 4.25 (1H, t, J = 8.7, 8.7, H-3′), 4.34 (1H, dd, J = 11.7, 5.2, H-6′), 4.51 (1H, dd, J = 11.7. 2.4, H-6′), 5.21 (1H,
d, J
= 7.8, H-1′), 5.26 (1H, t, J = 6.8, 6.8, H-24).
1′,2′
20
12-O-β-D-Glucopyranosyl-3β,12β,20S-trihydroxydammar-24-ene (21). C H O ·H O, amorph., [α]
D
-6.5°
36 62
8
2
(c 0.75, C H N). PMR spectrum (500 MHz, C D N, δ, ppm, J/Hz): 0.770 (3H, s, Me-19), 0.827 (3H, s, Me-18), 0.842 (3H,
5
5
5 5
s, Me-30), 1.019 (3H, s, Me-29), 1.223 (3H, s, Me-28), 1.343 (3H, s, Me-21), 1.643 (3H, s, Me-26), 1.649 (3H, s, Me-27), 3.42
(1H, dd, J = 10.7, 5.6, H-3α), 4.00 (1H, ddd, J = 9.6, 5.0, 2.6, H-5′), 4.09 (1H, dd, J = 9.0, 7.8, H-2′), 4.21 (1H, t, J = 9.2, 9.2,
H-4′), 4.29 (1H, t, J = 8.8, 8.8, H-3′), 4.30 (1H, m, H-12α), 4.32 (1H, dd, J = 11.6, 5.0, H-6′), 4.47 (1H, dd, J = 11.6, 2.6, H-6′),
5.27 (1H, d, J
= 7.6, H-1′), 5.34 (1H, m, H-24).
1′,2′
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458