New triterpene constituents, foliasalacins A1-A4, B1-B3, and C, from the leaves of Salacia chinensis

Article abstract of DOI:10.1248/cpb.56.915

Four dammarane-type, three lupane-type, and an oleanane-type triterpenes named foliasalacins A₁ (1), A₂ (2), A₃ (3), A₄ (4), B₁ (5), B₂ (6), B₃ (7), and C (8) were isolated from

Full text of DOI:10.1248/cpb.56.915

July 2008
Chem. Pharm. Bull. 56(7) 915—920 (2008)
915
New Triterpene Constituents, Foliasalacins A1—A4, B1—B3, and
C, from the Leaves of Salacia chinensis
Masayuki YOSHIKAWA,* Yi ZHANG, Tao WANG, Seikou NAKAMURA, and Hisashi MATSUDA
Kyoto Pharmaceutical University; Misasagi, Yamashina-ku, Kyoto 607–8412, Japan.
Received January 21, 2008; accepted April 9, 2008; published online April 14, 2008
Four dammarane-type, three lupane-type, and an oleanane-type triterpenes named foliasalacins A1 (1), A2
(2), A3 (3), A4 (4), B1 (5), B2 (6), B3 (7), and C (8) were isolated from the leaves of Salacia chinensis LINN. collected
in Thailand. The structures of new triterpene constituents (1—8) were characterized on the basis of chemical
and physiochemical evidence.
Key words Salacia chinensis; Hippocrateaceae; foliasalacin; dammarane type triterpene; lupane type triterpene; oleanane type
triterpene
During the course of our characterization studies on bioac- for the signals due to the side chain part (C-23—27, 31). As
1
tive constituents from Salacia species,1—13) we have reported shown in Fig. 1, the H–1H correlation spectroscopy (1H–1H
the isolation and absolute stereostructure elucidation of thir- COSY) experiment on 1 indicated the presence of partial
teen megastigmane glycosides, foliasalaciosides A1, A2, B1, structures written in bold lines, and in a heteronuclear multi-
B2, C, D, E1, E2, E3, F, G, H, and I, and seven new phenolic ple-bond correlation (HMBC) experiment, long-range corre-
glycosides, foliachinenosides A1, A2, A3, B1, B2, C, and D, lations were observed between the following protons and car-
from the leaves of Salacia chinensis LINN. (Hippocrateaceae) bons: H-5 and C-1, 7; H3-18 and C-8, 13—15; H3-19 and C-
together with twenty known constituents.14—16) As a continu- 1, 5, 9, 10; H3-21 and C-17, 20, 22; H2-26 and C-24, 25, 27;
ing study on the leaves of S. chinensis, we have isolated four H3-27 and C-24—26; H3-28 and C-3—5, 29; H3-29 and C-
dammarane-type, three lupane-type, and an oleanane-type 3—5, 28; H3-31 and C-23—25. Next, the stereochemistry of
triterpenes named foliasalacins A1 (1), A2 (2), A3 (3), A4 (4), the tetracyclic carbon skeleton structure (C-1—19, 28—30)
B1 (5), B2 (6), B3 (7), and C (8) from the less polar fraction in 1 was clarified using nuclear Overhauser enhancement
of the leaves. This paper deals with the isolation and struc- spectroscopy (NOESY) experiment, which showed NOE cor-
ture elucidation of these eight new triterpenes.
relations between the following proton pairs: Ha-1 and H-3,
The dried leaves of S. chinensis, which were collected at H-9; Hb-1 and H3-19; H-3 and H-5, H3-28; H-5 and H-9; H-
Nakhon Si Thammarat province, Thailand, were finely cut
and extracted with methanol (MeOH) to furnish a methanolic
extract (13.0%). The MeOH extract was partitioned into
an EtOAc–H2O (1 : 1, v/v) mixture to furnish an EtOAc-
soluble fraction (4.1%) and an aqueous phase as previ-
ously reported.14—16) From the EtOAc-soluble fraction,
foliasalacins A1 (1, 0.00038%), A2 (2, 0.00018%), A3 (3,
0.00038%), A4 (4, 0.00011%), B1 (5, 0.00073%), B2 (6,
0.00076%), B3 (7, 0.00070%), and C (8, 0.00005%), were
isolated using normal-, and reverse-phase silica gel column
chromatography, and finally HPLC (Chart 1).
Structures of Dammarane-Type Triterpenes, Folia-
salacins A1, A2, A3, and A4 Foliasalacin A1 (1), [a]D26
ꢀ33.1° (CHCl3), was isolated as a white powder. The IR
spectrum of 1 showed absorption bands at 3424 and
1646 cmꢁ1 ascribable to hydroxyl and olefin functions. The
electron ionization (EI) MS of 1 exhibited a molecular ion
peak at m/z 458, and the high resolution (HR) EI-MS analy-
sis revealed the molecular formula of 1 to be C31H54O2. The
1H- (CDCl3) and 13C-NMR (Table 1) spectra17) of 1 showed
signals assignable to eight methyls [d 0.77, 0.85, 0.87, 0.96,
0.97, 1.12, 1.65 (1.647) (3H each, all s, H3-29, 19, 18, 30, 28,
21, 27), 1.02 (1.019, 3H, d, Jꢂ6.7 Hz, H3-31)], a methine
bearing an oxygen function [d 3.20 (1H, dd, Jꢂ4.8, 11.7 Hz,
H-3)], a terminal double bond [d 4.68 (4.678, 2H, m, H2-
26)], together with ten methylenes, five methines, and six
quaternary carbons. The spectral data of 1 were similar to
those of a dammarane triterpene with an unusual and extra
Chart 1. Structures of New Foliasalacines from the Leaves of Salacia chi-
methyl group at the 24-position, carnaubadiol (9),18) except nensis
∗ To whom correspondence should be addressed. e-mail: myoshika@mb.kyoto-phu.ac.jp
© 2008 Pharmaceutical Society of Japan

916
Vol. 56, No. 7
9 and H3-18; H-13 and H3-21, H3-30; H-17 and H3-18. On tion in 1 was certificated to be S* orientation. Finally, the
the basis of above mentioned evidence, 1 was presumed to be stereostructure of the 24-position in 1 was determined to be
the 24-isomer of 9. By comparing the chemical shifts of the S* by the application of the reported NMR method.20,21)
20—22 carbons of 1 [dC 25.5 (C-21), 39.1 (C-22), 75.3 (C- Namely, the configuration at the 24-position in 1 was charac-
20)] with those of the 20-epimers of dammarane type com- terized by comparison of the Dd values of the side chain pro-
1
pounds, dammarenediol I (10, 20R) [dC 23.5 (C-21), 41.8 (C- tons (H-26—27, H-26—31, and H-27—31) in the H-NMR
22), 75.8 (C-20)]19) and dammarenediol II (11, 20S) [dC 24.9 (CDCl3) spectrum of 1 with those of known compounds,
(C-21), 40.5 (C-22), 75.4 (C-20)],19) which measured in the codisterol (12) [(24S)-methylcholesta-5,25-dien-3b-ol], epi-
same solvent (CDCl3) as 1, the stereostructure of the 20-posi- codisterol (13) [(24R)-methylcholesta-5,25-dien-3b-ol], and
leucastrin (14) [(3S,17S,20S,24S)-3,20-dihydroxy-24-methyl-
protost-25-ene]. As shown in Table 2, the Dd values of the
26- and 27-protons, the 26- and 31-protons, and the 27- and
31-protons in 1 were approximated to those of codisterol (12)
and leucastrin (14), thus the configuration at the 24-position
in 1 was elucidated to be S* orientation. On the basis of this
Table 1. 13C-NMR Data for 1—4
Position
1
2
3
4
1
2
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
31
39.1
27.4
79.0
39.0
55.9
18.3
35.2
40.4
50.7
37.1
21.6
24.7
42.3
50.4
31.2
27.6
49.5
16.5
16.2
75.3
25.5
39.1
28.9
41.7
149.9
109.6
18.8
28.0
15.4
15.5
20.0
39.1
27.4
79.0
39.0
55.9
18.3
35.3
40.4
50.6
37.1
21.5
25.4
42.2
50.0
31.1
27.6
49.3
16.4
16.2
75.7
23.8
40.2
28.4
41.7
149.9
109.6
18.8
28.0
15.4
15.5
20.0
39.2
27.4
78.9
39.0
55.7
18.2
36.3
40.9
51.4
37.3
21.3
24.9
43.5
50.5
74.0
38.7
45.3
9.1
16.4
152.2
107.8
32.3
33.6
41.0
149.8
109.6
18.9
28.0
15.4
15.7
19.8
39.1
27.4
79.0
39.0
55.9
18.3
35.2
40.4
50.7
37.1
21.6
24.8
42.4
50.4
31.2
27.5
49.8
16.5
16.2
75.4
25.4
39.4
28.4
156.5
34.0
21.94
21.96
28.0
15.4
15.5
106.2
1
evidence and comparison of the H- and 13C-NMR data of 1
with those of 9, foliasalacin A1 (1) was characterized to be
the 24-isomer of carnaubadiol (9).
Foliasalacin A2 (2), [a]D25 ꢀ22.0° (CHCl3), was isolated
as a white powder. The IR spectrum of 2 showed absorp-
tion bands at 3423 and 1647 cmꢁ1 assignable to hydroxyl
and olefin functions, respectively. Its molecular formula
Fig. 1. Selected 1H–1H COSY, HMBC, and NOE Correlations of 1—4
Measured in CDCl3 at 125 MHz.
Chart 2

July 2008
917
Table 2. Comparison of 1H Chemical Shifts of Compounds of 1—3, 12—
14
H3-28; H-5 and H-9; H-9 and H3-18; H-13 and H-15, H3-30;
H-15 and H3-30; H3-18 and Ha-17, so that the stereostruc-
ture of 3 including the 3b and 15a-hydroxyl groups was
clarified. On the other hand, the stereostructure of the 24-po-
sition was presumed to be S* by the same NMR method as
that for 1 and 2 (Table 2). Those findings led us to formulate
the structure of 3 as shown.
H
1
2
3
12
13
14
26
27
31
4.678
1.647
1.019
4.680
1.647
1.016
4.688
1.647
1.020
4.658
1.635
0.990
4.654
1.649
0.984
4.674
1.646
1.014
Foliasalacin A4 (4), [a]D27 ꢀ25.9° (CHCl3), was also ob-
tained as a white powder. The IR spectrum of 4 showed ab-
sorption bands at 3422 and 1647 cmꢁ1 ascribable to hydroxyl
and olefin functions, respectively. Its molecular formula,
C31H54O2, was determined from the molecular ion peak at
Dd
26–27
26–31
27–31
3.031
3.659
0.628
3.033
3.664
0.631
3.131
3.668
0.627
3.023
3.668
0.645
3.005
3.670
0.665
3.028
3.660
0.632
1
m/z 458 and by HR-EI-MS measurement. The H- (CDCl3)
Measured in CDCl3 at 500 MHz.
and 13C-NMR (Table 1) spectra17) of 4 showed signals assign-
C31H54O2, the same as that of 1, was determined from the able to eight methyls [d 0.78, 0.85, 0.89, 0.96, 0.98, 1.16 (3H
molecular ion peak at m/z 458 and by HR-EI-MS measure- each, all s, H3-29, 19, 18, 30, 28, 21), 1.04, 1.04 (3H each,
1
ment. The H- (CDCl3) and 13C-NMR (Table 1) spectra17) of both d, Jꢂ6.9 Hz, H3-26, 27)], a methine bearing an oxygen
2 showed signals assignable to eight methyls [d 0.78, 0.85, function [d 3.20 (1H, dd, Jꢂ4.2, 11.0 Hz, H-3)], a terminal
0.88, 0.97, 0.98, 1.10, 1.65 (1.647) (3H each, all s, H3-29, 19, double bond [d 4.69, 4.75 (1H each, both br s, H2-31)], to-
18, 30, 28, 21, 27), 1.02 (1.016, 3H, d, Jꢂ6.7 Hz, H3-31)], a gether with ten methylenes, five methines, and five quater-
1
methine bearing an oxygen function [d 3.20 (1H, dd, Jꢂ5.2, nary carbons. The proton and carbon signals in the H- and
11.6 Hz, H-3)], a terminal double bond [d 4.68 (4.680, 2H, 13C-NMR spectra of 4 were superimposable on those of fo-
m, H2-26)], together with ten methylenes, five methines, and liasalacin A1 (1), except for the signals due to the 24—27-
six quaternary carbons. The proton and carbon signals in the and 31-positions in the side chain. By comparison of the
1H- and 13C-NMR spectra of 2 were superimposable on those chemical shift values of the 20—23 carbons in the 13C-NMR
of 1, except for the signals due to the 20—22-positions. The of 4 with those of 1, the stereostructure at the 20-position in
1H–1H COSY, HMBC, and NOESY experiments on 2 4 was clarified to be the same as that of 1. Furthermore, as
(shown in Fig. 1) indicated that 2 was the 20-isomer of 1. By shown in Fig. 1, long-range correlations were observed be-
comparing the chemical shifts of the 20—22 carbons of 2 tween the following protons and carbons: H2-26 and C-24,
with those of the 20-epimers of dammarane type triterpenes, 25, 27; H3-27 and C-24—26; H2-31 and C-23—25, the struc-
dammarenediol I (10, 20R) and dammarenediol II (11, ture of the side chain part was determined as shown. On the
20S),19) the stereostructure of the 20-position in 2 was eluci- basis of above-mentioned evidence and detail examination of
dated as R* form. On the other hand, the 24-position in 2 was various NMR data as shown in Fig. 1, the structure of folia-
confirmed to be S* orientation by the same method21) as that salacin A4 (4) was characterized.
for 1 (the Dd values of H-26—27, H-26—31, and H-27—31
Structures of Lupane-Type Triterpenes, Foliasalacins
of 2 were shown in Table 2). Consequently, the structure of 2 B1 and B2 Foliasalacin B1 (5) was obtained as a white pow-
was elucidated as shown.
der with positive optical rotation ([a]D29 ꢀ9.4° in CHCl3),
Foliasalacin A3 (3), [a]D27 ꢀ31.4° (CHCl3), was isolated as and showed absorption bands at 3422 and 1717 cmꢁ1 due to
a white powder. The molecular formula, C31H52O2, was de- hydroxyl and carbonyl functions in the IR spectrum. The mo-
termined by EI and HR-EI-MS measurement. The 1H- lecular formula, C30H50O2, of 5 was determined from the EI-
(CDCl3) and 13C-NMR (Table 1) spectra17) of 3 showed sig- MS [m/z 442 (M)ꢀ], and by HR-EI-MS analysis. The H-
1
nals ascribable to seven methyls [d 0.78, 0.86, 0.95, 0.98, (CDCl3) and 13C-NMR (Table 3) spectra17) of 5 showed seven
1.06, 1.65 (1.647) (3H each, all s, H3-29, 19, 18, 28, 30, 27), methyls [d 0.75, 0.94, 0.94, 1.03, 1.08, 1.08 (3H each, all s,
1.02 (1.020, 3H, d, Jꢂ6.7 Hz, H3-31)], two methines bearing H3-28, 25, 27, 24, 23, 26), 0.97 (3H, d, Jꢂ6.8 Hz, H3-30)], a
an oxygen function [d 3.21 (1H, dd, Jꢂ4.9, 11.6 Hz, H-3], methene bearing an oxygen function [d 3.41 (1H, dd, Jꢂ8.1,
4.26 (1H, dd, Jꢂ8.6, 8.6 Hz, H-15), two terminal double 11.1 Hz), 3.82 (1H, dd, Jꢂ4.5, 11.1 Hz), H2-29], a carbonyl
bonds {d 4.69 (4.688, 2H, m, H2-26), [4.70 (1H, m), 4.71 function [dC 218.3 (C-3)], together with ten methylenes, five
1
(1H, br s), H2-21]}, together with nine methylenes, five me- methines, and four quaternary carbons. The H–1H COSY
thines, and five quaternary carbons. As shown in Fig. 1, the experiment on 5 indicated the presence of partial structures
1H–1H COSY experiment on 3 indicated the presence of par- written in bold lines (Fig. 2), and in HMBC experiment, the
tial structure written in bold lines, and in the HMBC experi- long-range correlations were observed between H-1 and C-3,
ment, long-range correlations were observed between the fol- 5; H-2 and C-3, 10; H3-23 and C-3—5, 24; H3-24 and C-3—
lowing proton and carbon pairs: H-5 and C-1, 7; H-15 and C- 5, 23; H3-25 and C-1, 5, 9, 10; H3-26 and C-7—9, 14; H3-27
13, 17, 18, H3-18 and C-8, 13—15; H3-19 and C-1, 5, 9, 10; and C-8, 13—15; H3-28 and C-16—18, 22; H2-29 and C-19,
H2-21 and C-17, 20, 22; H2-26 and C-24, 25, 27; H3-27 and 20, 30; H3-30 and C-19, 20, 29. The relative stereostructure
C-24—26; H3-28 and C-3—5, 29; H3-29 and C-3—5, 28; of 5 was determined on the NOESY experiment, which
H3-31 and C-23—25. The above-mentioned evidence indi- showed NOE correlations between H-1a and H-2a; H-1b
cated that 3 was a dammarane-type triterpene with the 24- and H-2b, H3-25; H-2b and H3-24, H3-25; H-5 and H-9, H3-
methyl and the 20- and 25-exo-methylenes at the side chain. 23; H-9 and H3-27; H-12a and H2-29, H3-30; H-13 and H3-
In the NOESY experiment, NOE correlations were observed 26, H3-28; H-18 and H3-27, H2-29, H3-30; H-19 and H3-28.
between Ha-1 and H-3, H-9; Hb-1 and H3-19; H-3 and H-5, Finally, reduction of 5 with NaBH4 in anhydrous MeOH gave

918
Vol. 56, No. 7
Table 3. 13C-NMR Data of 5—8 and Related Compounds (5a and 6a)
Position
5
5a
6
6a
7
8
1
2
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
39.5
34.2
218.3
47.3
54.8
19.7
33.6
40.8
49.4
36.8
21.5
27.2
38.0
43.1
27.3
35.4
43.1
47.4
43.6
38.0
23.1
40.1
26.7
21.0
15.9
15.8
14.4
17.6
64.5
18.0
38.7
27.4
79.0
38.9
55.2
18.3
34.3
40.9
50.0
37.1
20.9
27.2
37.9
43.0
27.3
35.5
43.1
47.5
43.6
38.0
23.1
40.1
28.0
15.4
16.1
16.0
14.4
17.6
64.5
18.0
39.6
34.2
218.3
47.4
54.9
19.7
33.6
40.8
49.4
36.8
21.4
26.9
37.9
43.1
27.3
35.4
42.9
47.2
39.2
37.9
21.9
40.5
26.7
21.1
15.8
15.9
14.3
18.1
68.2
10.3
38.7
27.4
79.0
38.9
55.2
18.3
34.3
40.9
50.0
37.1
20.8
26.9
38.0
42.9
27.3
35.5
43.0
47.2
39.2
37.8
21.9
40.6
28.0
15.4
16.0
16.1
14.4
18.1
68.4
10.3
39.5
34.1
218.3
47.3
54.8
19.7
33.7
40.8
49.3
36.8
21.5
27.0
37.8
43.1
27.3
35.3
43.0
48.6
43.5
42.0
23.8
39.7
26.7
21.0
16.0
15.8
14.4
17.8
181.8
17.1
38.8
27.3
79.0
38.8
55.0
18.6
37.9
42.4
50.5
37.4
21.7
25.1
133.6
50.7
67.0
46.2
36.2
133.4
39.0
33.3
35.1
39.0
28.0
15.5
16.3
18.1
13.8
24.2
32.3
24.1
Fig. 3
positive optical rotation ([a]D26 ꢀ17.2° in CHCl3). The mo-
lecular formula, C30H50O2, was determined from the EI-MS
1
[m/z 442 (M)ꢀ] and by HR-EI-MS measurement. The H-
(CDCl3) and 13C-NMR (Table 3) spectra17) of 6 [d 0.78 (3H,
s, H3-28), 0.80 (3H, d, Jꢂ6.8 Hz, H3-30), 1.22, 1.59 (1H
each, both m, H2-21), 1.95 (1H, m, H-19), 3.42 (2H, m, H2-
29); dC 10.3 (C-30), 18.1 (C-28), 21.9 (C-21), 39.2 (C-19),
68.2 (C-29)] were very similar to those of 5, except for the
protons of 19-, 21-, and 28—30-positions. Finally, the reduc-
tion of 6 with NaBH4 afforded a known compound (20S)-lu-
pane-3b,29-diol (6a)22) (Fig. 3). On the basis of this evidence
and detail NMR analysis (Fig. 2), the stereostructure of fo-
liasalacin B2 (6) was determined as shown.
Measured in CDCl3 at 125 MHz.
Foliasalacin B3 (7) was isolated as a white powder with
negative optical rotation ([a]D27 ꢁ26.4° in CHCl3). The EI-
MS of 7 exhibited a molecular ion peak at m/z 456, and the
HR-EI-MS analysis revealed the molecular formula of 7 to
be C30H48O3. The 1H- (CDCl3) and 13C-NMR (Table 3) spec-
tra of 7 showed seven methyls [d 0.76, 0.93, 0.94, 1.03, 1.08,
1.08 (3H each, all s, H3-28, 27, 25, 24, 23, 26), 1.15 (3H, d,
Jꢂ6.9 Hz, H3-30)], two carbonyl functions [dC 181.8 (C-29),
218.3 (C-3)], together with ten methylenes, five methines,
and four quaternary carbons. The planar and relative stere-
ostructures of 7 were determined by various NMR experi-
ment as shown in Fig. 2.17) By comparison of the chemical
shift values of the 28- and 30-protons in 7 with known com-
pounds, 20(R)- and 20(S)-3b-hydroxylupan-29-oic acid (15,
16) [(20R): 0.74 (3H, s, H3-28), 1.15 (3H, d, Jꢂ6.5 Hz, H3-
30); (20S): 0.77 (3H, s, H3-28), 1.05 (d, Jꢂ6.5 Hz, H3-30)],22)
the stereostructure of the 20-position in 7 was clarified to be
R* orientation. Finally, 7 was derived by oxidation of 5 with
chromium trioxide (CrO3) in pyridine, so that the stereostruc-
ture of foliasalacin B3 (7) was clarified as shown.
Structure of Oleanane-Type Triterpene, Foliasalacin C
Foliasalacin C (8) was obtained as a white powder with nega-
tive optical rotation ([a]D28 ꢁ25.1° in CHCl3) and the IR
spectrum of 8 showed absorption bands at 3422 and
1636 cmꢁ1 due to hydroxyl and olefin functions. The molecu-
lar formula, C30H50O2, was determined from the EI-MS [m/z
442 (M)ꢀ] and by HR-EI-MS analysis. The 1H- (CDCl3) and
13C-NMR (Table 3) spectra17) of 5 showed eight methyls [d
0.70, 0.77, 0.86, 0.90, 0.94, 0.98, 1.07, 1.17 (3H each, all s,
Fig. 2. Selected 1H–1H COSY, HMBC, and NOE Correlations of 5, 7 and
8
a known compound, (20R)-lupane-3b,29-diol (5a)22) (Fig. 3). H3-30, 24, 25, 26, 29, 24, 28, 27)], two methines bearing an
Thus, the stereostructure of 5 was characterized as shown. oxygen function [d 3.23 (1H, dd, Jꢂ4.1, 11.0 Hz, H-3), 4.13
Foliasalacin B2 (6) was isolated as a white powder with (1H, dd, Jꢂ8.3, 8.3 Hz, H-15)], a tetra-substituted double

July 2008
919
(88 : 12, v/v)] to furnish foliasalacins A3 (3, 9.1 mg, 0.00020%) and B3 (7,
31.8 mg, 0.00070%). Fraction 10-2-4 (817 mg) was subjected to HPLC
[MeOH–H2O (92 : 8, v/v)] and HPLC [MeOH–H2O (88 : 12, v/v)] to furnish
foliasalacins A3 (3, 2.1 mg, 0.00005%) and C (8, 2.1 mg, 0.00005%). Frac-
tion 10-2-5 (204 mg) was purified by HPLC [MeOH–H2O (92 : 8, v/v)] and
bond [dC 133.4 (C-18), 133.6 (C-13)], together with ten
methylenes, two methines, and five quaternary carbons. The
1H–1H COSY experiment on 8 indicated the presence of par-
tial structures written in bold lines, and in the HMBC experi-
ment, long-range correlations were observed between the fol- finally HPLC [MeOH–H2O (88 : 12, v/v)] to afford foliasalacins A1 (1,
17.0 mg, 0.00038%), A2 (2, 8.2 mg, 0.00018%), A4 (4, 4.9 mg, 0.00011%),
and B1 (5, 16.8 mg, 0.00037%). Fraction 11 (4.2 g) was subjected to re-
versed-phase silica gel column chromatography [150 g, MeOH–H2O
(70 : 30→80 : 20→90 : 10, v/v)→MeOH→CHCl3] to afford five fractions
lowing proton and carbon pairs: H2-11 and C-13; H2-12 and
C-18; H2-22 and C-18; H3-23 and C-3—5, 24; H3-24 and C-
3—5, 23; H3-25 and C-1, 5, 9, 10; H3-26 and C-7—9, 14;
H3-27 and C-8, 13—15; H3-28 and C-16—18, 22; H2-29 and
C-19—21, 30; H3-30 and C-19—21, 29. On the basis of
above mentioned evidence, 8 was elucidated to be an olean-
13-ene-type triterpene with the 3- and 15-hydroxyl groups.
The stereostructures of the 3- and 15-positions in 8 were de-
termined on the NOESY experiment, which showed NOE
correlations between the following proton pairs: Ha-1 and
Ha-2, H-3, H-9; Ha-2 and H-3; H-3 and H-5, H3-23; H-9
and Ha-12, H3-27; Ha-11 and Ha-12; Ha-12 and Ha-19;
H-15 and H3-26, H3-28; Ha-19 and H3-29. Consequently, the
3- and 15-hydroxyl functions were elucidated to be b and a-
configurations, respectively, and the stereostructure of fo-
liasalacin C (8) was characterized as shown in Fig. 2.
[Fr. 11-1 (45 mg), Fr. 11-2 (54 mg), Fr. 11-3 (40 mg), Fr. 11-4 (799 mg), Fr.
11-5 (1960 mg)]. Fraction 11-4 (799 mg) was separated by HPLC
[MeOH–H2O (92 : 8, v/v)] to give sixteen fractions [Fr. 11-4-1 (5.0 mg), Fr.
11-4-2 (9.1 mg), Fr. 11-4-3 (7.1 mg), Fr. 11-4-4 (55.9 mg), Fr. 11-4-5
(18.5 mg), Fr. 11-4-6 (107.7 mg), Fr. 11-4-7 (17.7 mg), Fr. 11-4-8 (29.2 mg),
Fr. 11-4-9 (34.5 mg), Fr. 11-4-10 (54.7 mg), Fr. 11-4-11 (64.5 mg), Fr. 11-4-
12 (78.6 mg), Fr. 11-4-13 (32.2 mg), Fr. 11-4-14 (15.7 mg), Fr. 11-4-15
(18.1 mg), Fr. 11-4-16 (16.2 mg)]. Fractions 11-4-13 and 11-4-16 were iden-
tified as foliasalacins B1 (5, 16.2 mg, 0.00036%) and B2 (6, 32.2 mg,
0.00072%), respectively. Fraction 11-4-7 (17.7 mg) was purified by HPLC
[MeOH–H2O (88 : 12, v/v)] to furnish foliasalacin A3 (3, 5.8 mg, 0.00013%).
Fraction 11-4-14 (15.7 mg) was purified by HPLC [MeOH–H2O (88 : 12,
v/v)] to furnish foliasalacin B2 (6, 1.9 mg, 0.00004%).
Foliasalacin A1 (1): A white powder; [a]D26 ꢀ33.1° (cꢂ0.85, CHCl3); IR
1
(KBr) nmax 3424, 2941, 2872, 1705, 1646, 1456, 1377, 756 cmꢁ1; H-NMR
(500 MHz, CDCl3) d 0.73 (1H, dd, Jꢂ2.0, 11.7 Hz, H-5), 0.77, 0.85, 0.87,
Experimental
0.96, 0.97, 1.12 (3H each, all s, H3-29, 19, 18, 30, 28, 21), 0.95 (1H, m, H-
General Experimental Procedures The following instruments were 1a), 1.02 (3H, Jꢂ6.7 Hz, H3-31), 1.32 (1H, m, H-9), 1.63 (1H, m, H-1b),
used to obtain physical data: specific rotations, Horiba SEPA-300 digital po- 1.64 (1H, m, H-13), 1.65 (3H, br s, H3-27), 1.70 (1H, m, H-17), 3.20 (1H,
larimeter (lꢂ5 cm); CD spectra, JASCO J-720WI spectrometer; UV spectra, dd, Jꢂ4.8, 11.7 Hz, H-3), 4.68 (2H, m, H2-26); 13C-NMR data (125 MHz,
Shimadzu UV-1600 spectrometer; IR spectra, Shimadzu FTIR-8100 spec- CDCl3) dC: see Table 1; EI-MS m/z 458 (M)ꢀ (0.4), 440 (5), 422 (4), 379
trometer; EI-MS and high-resolution MS, JEOL JMS-GCMATE mass spec- (4), 141 (43), 123 (100); HR-EI-MS m/z 458.4132 [Calcd for C31H54O2
trometer; 1H-NMR spectra, JEOL EX-270 (270 MHz) and JNM-LA500
(500 MHz) spectrometers; 13C-NMR spectra, JEOL EX-270 (68 MHz) and
(M)ꢀ, 458.4124].
Foliasalacin A2 (2): A white powder; [a]D25 ꢀ22.0° (cꢂ0.21, CHCl3); IR
JNM-LA500 (125 MHz) spectrometers with tetramethylsilane as an internal (KBr) nmax 3423, 2933, 2870, 1647, 1338, 887 cmꢁ1
;
1H-NMR (500 MHz,
standard; and HPLC detector, Shimadzu RID-6A refractive index and SPD- CDCl3) d 0.73 (1H, dd, Jꢂ2.2, 11.9 Hz, H-5), 0.78, 0.85, 0.88, 0.97, 0.98,
10Avp UV–VIS detectors. HPLC column, Cosmosil 5C18-MS-II (Nacalai
1.10 (3H each, all s, H3-29, 19, 18, 30, 28, 21), 0.97 (1H, m, H-1a), 1.02
Tesque Inc., 250ꢃ4.6 mm i.d.) and (250ꢃ20 mm i.d.) columns were used for (3H, Jꢂ6.7 Hz, H3-31), 1.31 (1H, m, H-9), 1.69 (1H, m, H-1b), 1.69 (1H, m,
analytical and preparative purposes, respectively.
H-17), 1.65 (3H, br s, H3-27), 1.71 (1H, m, H-13), 3.20 (1H, dd, Jꢂ5.2,
The following experimental conditions were used for chromatography: or- 11.6 Hz, H-3), 4.68 (2H, m, H2-26); 13C-NMR data (125 MHz, CDCl3) dC:
dinary-phase silica gel column chromatography, Silica gel BW-200 (Fuji see Table 1; EI-MS m/z 458 (M)ꢀ (2), 440 (35), 422 (50), 379 (69), 141
Silysia Chemical, Ltd., Aichi, Japan, 150—350 mesh); reversed-phase silica (88), 123 (100); HR-EI-MS m/z 458.4120 [Calcd for C31H54O2 (M)ꢀ,
gel column chromatography, Chromatorex ODS DM1020T (Fuji Silysia 458.4124].
Chemical, Ltd., Aichi, Japan, 100—200 mesh); TLC plates and precoated
TLC plates with Silica gel 60F254 (Merck, 0.25 mm) (ordinary phase) and
Foliasalacin A3 (3): A white powder; [a]D27 ꢀ31.4° (cꢂ0.58, CHCl3); IR
1
(KBr) nmax 3422, 2933, 2870, 1705, 1636, 1215, 887, 754 cmꢁ1; H-NMR
Silica gel RP-18 F254S (Merck, 0.25 mm) (reversed phase); reversed-phase (500 MHz, CDCl3) d 0.74 (1H, dd, Jꢂ2.2, 11.6 Hz, H-5), 0.78, 0.86, 0.95,
HPTLC, with Silica gel RP-18 WF254S (Merck, 0.25 mm); and detection was 0.98, 1.06 (3H each, all s, H3-29, 19, 18, 28, 30), 0.94 (1H, m, H-1a), 1.02
achieved by spraying with 1% Ce(SO4)2–10% aqueous H2SO4 followed by (3H, Jꢂ6.7 Hz, H3-31), 1.28 (1H, dd, Jꢂ2.8, 11.9 Hz, H-9), 1.65 (3H, br s,
heating.
H3-27), 1.68 (1H, m, H-1b), 2.21 (1H, m, H-17), 3.21 (1H, dd, Jꢂ4.9,
Plant Material The dried leaves of S. chinensis were collected at 11.6 Hz, H-3), 4.26 (1H, dd, Jꢂ8.6, 8.6 Hz, H-15), 4.69 (2H, m, H2-26),
Nakhon Si Thammarat province, Thailand in 2006 and identified by one of 4.70 (1H, m, Ha-21), 4.71 (1H, br s, Hb-21); 13C-NMR data (125 MHz,
authors (Rajamangala University of Technology Srivijaya, Pongpiriyadacha CDCl3) dC: see Table 1; EI-MS m/z 456 (M)ꢀ (6), 438 (14), 420 (13), 395
Y.). A voucher of the plant is on file in our laboratory (2006. Thai-06).
Extraction and Isolation The dried leaves of S. chinensis LINN. (5.8 kg)
were finely cut and extracted 3 times with methanol (MeOH) under reflux
(20), 306 (40), 205 (100); HR-EI-MS m/z 456.3973 [Calcd for C31H52O2
(M)ꢀ, 456.3967].
Foliasalacin A4 (4): A white powder; [a]D27 ꢀ25.9° (cꢂ0.20, CHCl3); IR
for 3 h. Evaporation of the solvent under reduced pressure provided a (KBr) nmax 3422, 2933, 2872, 1647, 889, 803, 754 cmꢁ1
;
1H-NMR
methanolic extract (756 g, 13.0%). The MeOH extract (712 g) was parti- (500 MHz, CDCl3) d 0.73 (1H, dd, Jꢂ2.2, 11.9 Hz, H-5), 0.78, 0.85, 0.89,
tioned into an EtOAc–H2O (1 : 1, v/v) mixture to furnish an EtOAc-soluble
fraction (222 g, 4.1%) and an aqueous phase. The EtOAc fraction (200 g)
was subjected to ordinary-phase silica gel column chromatography [3.8
0.96, 0.98, 1.16 (3H each, all s, H3-29, 19, 18, 30, 28, 21), 0.99 (1H, m, H-
1a), 1.04, 1.04 (3H each, both d, Jꢂ6.9 Hz, H3-26, 27), 1.31 (1H, m, H-9),
1.70 (1H, m, H-1b), 1.71 (1H, m, H-17), 3.20 (1H, dd, Jꢂ4.2, 11.0 Hz, H-
kg, hexane–EtOAc (40 : 1→10 : 1→5 : 1→1 : 1, v/v)→CHCl3–MeOH–H2O 3), 4.69, 4.75 (1H each, both br s, H2-31); 13C-NMR data (125 MHz, CDCl3)
(10 : 3 : 1, v/v/v, lower layer)→MeOH] to give sixteen fractions [Fr. 1 (0.7 g), dC: see Table 1; EI-MS: m/z 458 (M)ꢀ (4), 440 (44), 422 (43), 379 (43), 190
Fr. 2 (1.3 g), Fr. 3 (28.3 g), Fr. 4 (0.9 g), Fr. 5 (9.0 g), Fr. 6 (14.9 g), Fr. 7 (34), 141 (100); HR-EI-MS m/z 458.4117 [Calcd for C31H54O2 (M)ꢀ,
(3.2 g), Fr. 8 (10.7 g), Fr. 9 (9.1 g), Fr. 10 (6.2 g), Fr. 11 (4.2 g), Fr. 12 458.4124].
(13.8 g), Fr. 13 (4.1 g), Fr. 14 (43.2 g), Fr. 15 (16.9 g), Fr. 16 (26.3 g)]. Frac-
Foliasalacin B1 (5): A white powder; [a]D29 ꢀ9.4° (cꢂ0.79, CHCl3); IR
tion 10 (6.2 g) was subjected to Sephadex LH-20 column chromatography (KBr) nmax 3422, 2936, 2870, 1717, 756 cmꢁ1; 1H-NMR (500 MHz, CDCl3)
[200 g, MeOH–CHCl3 (1 : 1, v/v)] to give two fractions [Fr. 10-1 (2400 mg), d 0.75, 0.94, 0.94, 1.03, 1.08, 1.08 (3H each, all s, H3-28, 25, 27, 24, 23,
Fr. 10-2 (3600 mg)]. Fraction 10-2 (3600 mg) was subjected to reversed- 26), 0.97 (3H, d, Jꢂ6.8 Hz, H3-30), 1.29 (1H, m, H-18), 1.33 (1H, m, H-5),
phase silica gel column chromatography [120 g, CH3CN–H2O (75 : 25→ [1.37 (1H, m), 1.68 (1H, m), H2-21], 1.37 (1H, m, H-9), 1.37 (1H, m, H-
85 : 15→90 : 10→100 : 5, v/v)→CH3CN→CHCl3] to give nine fractions [Fr. 12a), 1.40 (1H, m, H-1a), 1.68 (1H, m, H-12b), 1.70 (1H, m, H-13), 1.77
10-2-1 (150 mg), Fr. 10-2-2 (164 mg), Fr. 10-2-3 (192 mg), Fr. 10-2-4 (1H, m, H-19), 1.92 (1H, m, H-1b), 2.43 (1H, ddd, Jꢂ4.3, 7.3, 15.6 Hz, H-
(817 mg), Fr. 10-2-5 (204 mg), Fr. 10-2-6 (70 mg), Fr. 10-2-7 (49 mg), Fr. 2a), 2.49 (1H, ddd, Jꢂ7.7, 9.5, 15.6 Hz, H-2b), [3.41 (1H, dd, Jꢂ8.1,
10-2-8 (159 mg), Fr. 10-2-9 (583 mg)]. Fraction 10-2-3 (192 mg) was puri- 11.1 Hz), 3.82 (1H, dd, Jꢂ4.5, 11.1 Hz), H2-29]; 13C-NMR data (125 MHz,
fied by HPLC [MeOH–H2O (92 : 8, v/v)] and finally HPLC [MeOH–H2O CDCl3) dC: see Table 3; EI-MS m/z 442 (M)ꢀ (63), 427 (23), 424 (24), 411

920
Vol. 56, No. 7
tion mixture as described above to give (20S)-lupane-3b,29-diol (6a, 5.3 mg,
94.6%). The obtained compound 6a was identified by comparison of their
physical data ([a]D, 1H-NMR, MS) with reported values.
(11), 409 (16), 383 (41), 205 (100); HR-EI-MS m/z 442.3815 [Calcd for
C30H50O2 (M)ꢀ, 442.3811].
Foliasalacin B2 (6): A white powder; [a]D26 ꢀ17.2° (cꢂ1.70, CHCl3); IR
(KBr) nmax 3415, 2935, 2870, 1717, 754 cmꢁ1; 1H-NMR (500 MHz, CDCl3)
d 0.78, 0.95, 0.95, 1.03, 1.08, 1.08 (3H each, all s, H3-28, 25, 27, 24, 23,
26), 0.80 (3H, d, Jꢂ6.8 Hz, H3-30), [1.22 (1H, m), 1.59 (1H, m), H2-21],
1.24 (1H, m, H-18), 1.32 (1H, m, H-5), 1.36 (1H, m, H-12a), 1.37 (1H, m,
H-9), 1.42 (1H, m, H-1a), 1.68 (1H, m, H-12b), 1.72 (1H, m, H-13), 1.92
(1H, m, H-1b), 1.95 (1H, m, H-19), 2.40 (1H, ddd, Jꢂ4.3, 7.3, 15.6 Hz, H-
2a), 2.49 (1H, ddd, Jꢂ7.7, 9.5, 15.6 Hz, H-2b), 3.42 (2H, m, H2-29); 13C-
NMR data (125 MHz, CDCl3) dC: see Table 3; EI-MS m/z 442 (M)ꢀ (64),
427 (19), 424 (27), 411 (7), 409 (12), 383 (31), 205 (100); HR-EI-MS m/z
442.3818 [Calcd for C30H50O2 (M)ꢀ, 442.3811].
(20S)-Lupane-3b,29-diol (6a): A white powder; [a]D30 ꢁ2.0° (cꢂ0.05,
CHCl3; lit: [a]D20 ꢁ5.8°); 13C-NMR data (125 MHz, CDCl3) dC: see Table 3;
EI-MS: m/z 444 (M)ꢀ (13), 426 (21), 207 (100), 189 (93).
Acknowledgments This research was supported by the 21st COE pro-
gram and Academic Frontier Project from the Ministry of Education, Cul-
ture, Sports, Science and Technology of Japan.
References and Notes
1) Yoshikawa M., Murakami T., Shimada H., Matsuda H., Yamahara J.,
Tanabe G., Muraoka O., Tetrahedron Lett., 38, 8367—8370 (1997).
2) Yoshikawa M., Murakami T., Yashiro K., Matsuda H., Chem. Pharm.
Bull., 46, 1339—1340 (1998).
3) Matsuda H., Murakami T., Yashiro K., Yoshikawa M., Chem. Pharm.
Bull., 47, 1725—1729 (1999).
4) Yoshikawa M., Nishida N., Shimoda H., Takada M., Kawahara Y.,
Matsuda H., Yakugaku Zasshi, 121, 371—378 (2001).
5) Yoshikawa M., Morikawa T., Matsuda H., Tanabe G., Muraoka O.,
Bioorg. Med. Chem., 10, 1547—1554 (2002).
6) Yoshikawa M., Ninomiya K., Shimoda H., Nishida N., Matsuda H.,
Biol. Pharm. Bull., 25, 72—76 (2002).
Foliasalacin B3 (7): A white powder; [a]D27 ꢁ26.4° (cꢂ0.97, CHCl3); IR
(KBr) nmax 2936, 2869, 1707, 1460, 1381, 1229, 1115 cmꢁ1 1H-NMR
;
(500 MHz, CDCl3) d 0.76, 0.93, 0.94, 1.03, 1.08, 1.08 (3H each, all s, H3-
28, 27, 25, 24, 23, 26), 1.15 (3H, d, Jꢂ6.8 Hz, H3-30), 1.44 (1H, m, H-18),
1.32 (1H, m, H-5), 1.41 (1H, m, H-9), 1.52 (1H, m, H-12a), 1.43 (1H, m, H-
1a), 1.56 (1H, m, H-12b), 1.73 (1H, m, H-13), 1.78 (1H, m, H-19), 1.92
(1H, m, H-1b), 2.42 (1H, ddd, Jꢂ4.8, 7.6, 15.8 Hz, H-2a), 2.48 (1H, m, H-
2b); 13C-NMR data (125 MHz, CDCl3) dC: see Table 3; EI-MS: m/z 456
(M)ꢀ (21), 441 (11), 438 (19), 423 (10), 383 (100), 358 (3), 221 (23), 205
(55), 163 (61); HR-EI-MS m/z 456.3601 [Calcd for C30H50O2 (M)ꢀ,
456.3603].
Foliasalacin C (8): A white powder; [a]D28 ꢁ25.1° (cꢂ0.11, CHCl3); IR
(KBr) nmax 3422, 2941, 2870, 1636, 756 cmꢁ1; 1H-NMR (500 MHz, CDCl3)
d 0.76 (1H, m, H-5), 0.70, 0.77, 0.86, 0.90, 0.94, 0.98, 1.07, 1.17 (3H each,
all s, H3-30, 24, 25, 26, 29, 23, 28, 27), 0.96 (1H, m, H-1a), 1.25 (1H, m, H-
11a), 1.44 (1H, m, H-9), 1.47 (1H, m, H-11b), 1.58 (1H, m, H-2b), 1.60
(1H, m, H-19b), 1.66 (1H, m, H-2a), 1.70 (1H, m, H-1b), 1.94 (1H, m, H-
12b), 2.25 (1H, dd, Jꢂ2.7, 14.5 Hz, H-19a), 2.67 (1H, m, H-12a), 3.23
(1H, dd, Jꢂ4.1, 11.0 Hz, H-3), 4.13 (1H, dd, Jꢂ8.3, 8.3 Hz, H-15); 13C-
NMR data (125 MHz, CDCl3) dC: see Table 3; EI-MS: m/z 442 (M)ꢀ (18),
424 (18), 409 (16), 406 (6), 391 (6), 255 (7), 234 (29), 203 (100), 189 (34);
HR-EI-MS m/z 442.3807 [Calcd for C30H50O2 (M)ꢀ, 442.3811].
7) Yoshikawa M., Shimoda H., Nishida N., Takada M., Matsuda H., J.
Nutr., 132, 1819—1824 (2002).
8) Yoshikawa M., FOOD Style 21, 6, 72—78 (2002).
9) Morikawa T., Kishi A., Pongpiriyadacha Y., Matsuda H., Yoshikawa
M., J. Nat. Prod., 66, 1191—1196 (2003).
10) Kishi A., Morikawa T., Matsuda H., Yoshikawa M., Chem. Pharm.
Bull., 51, 1051—1055 (2003).
11) Yoshikawa M., Pongpiriyadacha Y., Kishi A., Kageura T., Wang T.,
Morikawa T., Matsuda H., Yakugaku Zasshi, 123, 871—880 (2003).
12) Matsuda H., Yoshikawa M., Morikawa T., Tanabe G., Muraoka O., J.
Trad. Med., 22, 145—153 (2005).
13) Yoshikawa M., Xu F., Nakamura S., Wang T., Matsuda H., Tababe G.,
Muraoka O., Heterocycles, 75 (2008), in press.
14) Nakamura S., Zhang Y., Pongpiriyadacha Y., Wang T., Matsuda H.,
Yoshikawa M., Heterocycles, 75, 131—143 (2008).
15) Zhang Y., Nakamura S., Pongpiriyadacha Y., Matsuda H., Yoshikawa
M., Chem. Pharm. Bull., 56, 547—553 (2008).
NaBH4 Reduction of Foliasalacin B1 (5) A solution of foliasalacin B1
(5) (5.5 mg) in dehydrated MeOH (1.0 ml) was treated with sodium borohy-
dride (NaBH4, 1.0 mg) and the mixture was stirred at room temperature for
1 h. The reaction mixture was quenched in acetone, and then removal of the
solvent under reduced pressure yielded a reaction mixture, which was puri-
fied by normal-phase silica gel CC [500 mg, hexane–EtOAc (3 : 1, v/v)] to
furnish (20R)-lupane-3b,29-diol (5a, 5.1 mg, 92.6%). The obtained com-
pound 5a was identified by comparison of their physical data ([a]D, 1H-
NMR, MS) with reported values.
16) Nakamura S., Zhang Y., Wang T., Matsuda H., Yoshikawa M., Hetero-
cycles, 75 (2008), in press.
1
17) The H- and 13C-NMR spectra of 1—5, were assigned with the aid of
(20R)-Lupane-3b,29-diol (5a): A white powder; [a]D30 ꢁ4.0° (cꢂ0.48,
CHCl3; lit: [a]D20 ꢁ14.1°); 13C-NMR data (125 MHz, CDCl3) dC: see Table
3; EI-MS: m/z 444 (M)ꢀ (20), 426 (18), 207 (100), 189 (84).
distortionless enhancement by polarization transfer (DEPT), homocor-
relation spectroscopy (1H–1H COSY), heteronuclear multiple-quantum
coherence (HMQC), and HMBC experiments.
18) Cysne J. B., Braz-Filho R., Assuncao M. V., Andrade U., Daniel E.,
Silveira E. R., Pessoa O. D. L., Magn. Reson. Chem., 44, 641—643
(2006).
19) Asakawa J., Kasai R., Yamasaki K., Tanaka O., Tetrahedron, 33,
1935—1939 (1977).
20) Catalan C. A. N., Thompson J. E., Kokke W. C. M. C., Djerassi C.,
Tetrahedron, 41, 1073—1084 (1985).
21) Miyaichi Y., Segawa A., Tomimori T., Chem. Pharm. Bull., 54, 1370—
1379 (2006).
CrO3–Pyridine Oxidation of Foliasalacin B1 (5) A solution of fo-
liasalacin B1 (5) (3.9 mg) in pyridine (0.5 ml) was treated with chromium tri-
oxide (CrO3, 2.0 mg)–pyridine (0.5 ml) mixture, and the mixture was stirred
at room temperature for 2.0 h. Removal of the solvent under reduced pres-
sure to a residue, which was purified by HPLC [MeOH–H2O (92 : 8, v/v)] to
give foliasalacin B3 (7) (1.0 mg, 24.8%). The obtained 7 was identified by
1
comparison of their physical data ([a]D, H-NMR, 13C-NMR, MS) with the
values of isolated foliasalacin B3 (7).
NaBH4 Reduction of Foliasalacin B2 (6) A solution of foliasalacin B2
(6) (5.6 mg) in dehydrated MeOH (1.0 ml) was treated with NaBH4 (1.0 mg)
and the mixture was stirred at room temperature for 1 h. Workup of the reac-
22) Eric A., Masimo P., Robert C. S., J. Chem. Soc. Perkin Trans. 1, 1985,
2051—2056 (1985).