M.
a l.
1480
from the
246 peak. Furthermore, there was a promi-
Wolff-Kishner reduction to give
acid
mp
Therefore, the
nent peak at m/z 146 (74%) apparently due to the
secondary retro-Diels-Alder cleavage of the m/z 218
fragment ion. These fragmentations resemble very closely
structure of rotungenic acid was established to be
acid (4).
those of rotundic acid (2). The
spectrum also
Rotundioic acid
mp
50”
indicated that it was closely related in structure to revealed a molecular ion at
corresponding
compound 2 except for the substitution mode of A ring to
(Table 1). The signal at was assigned to the
methyl group because it was observed at about
and retro-Diels-Alder fragmentation ions
at m/z 264 and 238 from the cleavage of the C-ring of
derivative. The m/z 238 ion suggested the presence
higher field than the
triterpenes possessing a
in most
group
and oleane of one carboxyl group in rings A/B. This fragmentation
There- and the IR and UV spectra (see Experimental) showed the
fore, the hydroxymethyl group giving a signal at
must be present in the
presence of similar groups in 5 to those in 3 and 4 except
for one additional carboxyl group instead of the
A further proof on the substitution was obtained from methyl group. Its
spectrum revealed thirty
spectrum of methyl rotungenate (9) carbon signals including characteristic signals due to two
signal (6 3.44, showed the
the
(Table 2). The
carboxyl groups (6 178.2 and
a trisubstituted
shift of SO.16 compared to that of methyl rotundate
attributed to the loss of a shielding effect by the equatrial bons (6 70.4 and 73.3). It afforded a
group. On the other hand, a W-type long
range coupling was observed between the signal and
double bond (6 125.6 and 137.6) and two alcoholic car-
acetate (14)
group (6 5.17:
which showed the presence of a
dd, 11.5 and 4.5 Hz;
in the ‘HNMR
H-l 8) suggested the
one (6 3.35) of the
indicated that compound 4 could be
signals. These data spectrum. A signal at
presence of a
urs-12-ene skeleton
ursolic acid, an epimer of barbinervic acid 6
structure was also elucidated chemically as follows.
Rotungenic acid (4) was oxidized with chromic
and the
These facts indicated that compound was related to 2
and 3 except for the exchanging of group to
In the NMR spectrum of5, the C-4 signal at
52.3 was shifted to downfield by 9 ppm from those of
dride in pyridine to give an 24-aldehyde
followed by
2 or 3, and the chemical shift was very similar to that
(653.0) of an oleane triterpene gypsogenic acid
possessing an equatorial carboxyl group at C-23. On the
other hand, the comparison of the spectrum with that of
Table 1.
c
spectral data
and
for com-
pounds
ilexgenin A (7)
having a C-24 axial carboxyl group
2
4
5
revealed significant differences in the chemical shifts of
the A and B ring carbons (Table 1). Therefore, one of the
carboxyl groups in 5 should be restricted to C-23 and the
structure 5 was also established as follows.
1
2
3
4
5
6
38.9
21.1
73.7
42.9
48.8
18.9
33.4
40.4
47.9
37.3
24. I
128.1
140.0
42.2
29.4
26.5
48.3
54.7
72.7
42.4
27.0
38.5
68.2
13.1
38.8
28.5
38.5
26.9
73.3
52.2
49.6
19.5
34.5
39.8
45.9
36.8
24.1
125.6
137.6
40.0
31.1
25.4
45.7
52.3
70.4
39.8
24.8
36.1
39.8
29.1
80.3
43.2
56.5
19.3
34.0
40.4
47.9
37.2
24.3
127.9
140.0
42.1
29.1
26.5
48.4
54.7
72.8
42.4
27.0
38.6
23.7
64.6
17.2
16.8
24.7
180.8
27.2
16.1
78.3
49.2
56.9
20.9
33.9
40.2
47.2
37.9
24.5
128.1.
139.9
42.2
29.1
26.5
48.3
54.7
72.7
42.2
27.0
38.4
24.2
Oxidation of the
silver oxide gave rotundioic acid
16 derived from 2 with
while reduction of 5
and 8 with lithium aluminium hydride afforded the same
tetraol 18. The spectral and chemical evidence elucidated
the structure of 5 as
8
9
dioic acid.
10
11
12
13
14
15
EXPERIMENTAL
Mps:
Concentrations were performed under red. pres.
at bath
not exceeding
NMR spectra were obtained
at 360 MHz and
NMR spectra at 25.2 MHz. All the com-
pounds were finally purified by HPLC on a
column using solvent system.
Plant material. The ripe fruits of the plant were collected at
Kagoshima University in March 1980.
17
18
19
20
21
22
23
24
25
26
27
28
29
30
isolation. The ripe fruits (2 kg) were extracted
with
added and the mixture extracted with
15 and g of extracts, respectively. The
fractionated by CC using a
give six fractions,
(3 10 1). After
to 500 ml,
was
to give
extract (5 g) was
solvent system to
and
178.2
9.8
17.3
16.8
24.9
180.7
27.2
16.0
13.8
14.4
24.6
178.3
26.9
14.8
13.9
17.1
24.5
180.6
27.0
16.8
350 mg,
(2%
2.5 g. III (3%
6 0 0 m g ,
600 mg.
7 5 0 m g a n d
matography of the fraction I afforded ursolic acid (1) (35 mg).
After rechromatography, the fraction
by repeated HPLC using 3040%
(125 mg) was separated
as the to
*Cited from ref.
Measured
give 2 (80 mg), 4 (8 mg) and 5 (4.5 mg). HPLC separation of the
fraction IV mg) with afforded mg)