Full text of DOI:10.1016/0031-9422(71)85036-7

1 9 7 1 , Vol. 1 0 ,
1 6 2 1 t o 1 6 2 6 .
Prin t ed in En glan d.
STRUCTURE OF SABANDININ AND OTHER
COUMARINS ISOLATED FROM THE ROOTS OF
A. G. G O N ZAL E Z
University of La Laguna, Department of Organic Chemistry,
lnstituto de Investigaciones Quimicas
C.S.I.C., Tenerife, Canary Islands, Spain
and
and 1.
R.
Escuela de Ingenieria
Industrial de Las
de Gran
Canary Islands, Spain
(Received 14 August 1970)
Abstract-Gravelliferone methyl ether (I), xanthyletin, furopinnarin (IV), pinnarin (VI), benahorin (VII),
limettin, luvangetin, bergapten
L.
and a new coumarin sabandinin (X) were isolated from the roots of
by degradative studies.
The structures of I, IV and VII were
INTRODUCTION
L. fil. (Rutaceae), endemic to the Canary Islands, is an excellent source of
we examined the benzene-soluble fraction of the alcoholic
coumarins.
extract of the roots and succeeded in isolating xanthyletin, luvangetin, thamnosin,
pinnarin (IV), furopinnarin (VI) and sabandin, the last three compounds being new.
Of the three possible structures then suggested for
the spectroscopic
formula XI best agreed with
The present communication reports the coumarins isolated from the petroleum-soluble
fraction of the steam-distilled alcoholic extract of the roots, which by column chromato-
graphy on alumina yielded gravelliferone methyl ether (I), xanthyletin, furopinnarin (IV),
pinnarin (VI), limettin, luvangetin, benahorin
bergapten
and finally a new
coumarin which, due to its close relationship to sabandin, we have called sabandinin (X).
RESULTS AND DISCUSSION
The first coumarin eluted, gravelliferone methyl ether (I) (NMR: Table was recently
who proposed structure I based on
isolated from
L. by Reisch et
elementary and spectroscopic analyses. We found that acid treatment of I gave a mixture
of four coumarins which were separated by chromatography on alumina. NMR showed
three of them to be isomers of I. The fourth one was identified as
herniarin (II), also isolated by Reisch et
from
graveolens L., its NMR spectrum
Part XVII in the series “New Sources of Natural Coumarins”. for Part XVI, see R.
and A. G. Anal. Quim. (in press).
A. G.
and R.
Anal. Fis. Quim.
803 (1965);
649 (1963); R.
981 (1966);
Fis. Quim.
and A. G.
and A. G.
765 (1963);
641 (1968);
91 (1969).
R.
R.
A.
Anal. Quim. 66, 167 (1970).
9,833 (1970).
E.
MA A.
and F.
Anal. Quim. (in press).
J . R EISCH, K.
E.
an d I. NOVAK, Tetrahedron Letters 4395 (1968).
1621

1622
A. G. GO N ZAL E Z, R.
and I. J AR AI Z
OCH,
C
OCH,
l x
X
(Table
being in accord with formula II. It thus represents a contribution to the structure
of gravelliferone methyl ether. Hydrogenation of I over
ferone methyl ether (III) (NMR: Table 1).
yielded
The next coumarins isolated, xanthyletin, furopinnarin (IV), pinnarin (VI), limettin
and luvangetin, were identified by direct comparison with authentic samples. In the mass
spectrum of pinnarin (see Experimental) the intensity of the molecular peak
274) is
78
indicating the great stability of this coumarin.
Acid treatment of furopinnarin gave
of
bergapten (V), which thus confirms the proposed
(IV).

1624
A. G.
G
ONZALEZ, R.
and I. JARAIZ
Between pinnarin and limettin we eluted an oily substance with a yellow-ochre
which crystallized from as large quadrangular plates of m.p. 88-90”
identified as benahorin (VII) (NMR: Table 1). For this compound, recently isolated from
the twigs of L. fil., we proposed the structure
Acid treatment of this furocoumarin under
psoralen (VII) based on spectroscopic studies.
stronger conditions than those used for the degradation of gravelliferone methyl ether and
furopinnarin, gave xanthotoxin (VIII) in 20% yield (NMR: Table 1). This confirms the
structure suggested for benahorin, an isomer of furopinnarin. In the mass spectrum of VII
the base peak is given by the molecular ion, which proves that the molecule is very stable.
Hydrogenation with
343 nm characteristic of dihydrofurocoumarins. In its NMR spectrum (Table 1) the doublet
attributed to the H-4 appears at slightly displaced with respect to the corresponding
one in benahorin 1.54) due to the deshielding caused by hydrogenating the ring.
gave tetrahydrobenahorin (IX) which has
absorption at
Finally, light petroleum-benzene (1: eluted a mixture of two coumarins, one of them
being identified by TLC as bergapten (V) (NMR: Table 1). As their separation proved to be
difficult, the mixture was first hydrogenated with
alumina, separating dihydrobergapten from the new coumarin sabandinin (X) which had
not undergone any alteration. It has the empirical formula m.p. very
soft greenish yellow fluorescence and shows the typical absorption of a simple
coumarin. The chemical shifts (Table 1) are in agreement with the structure of
and then chromatographed on
8-methylenedioxycoumarin (X), the singlet at
being characteristic of the H-6 in a
coumarin with substituents OR on the adjacent C atoms. The NMR signals
for H-4
recently
and
for H-5, present in the isomer
isolated by Herz et
from Artemisia dracunculoides Pursh, confirm our assignations for
H-4 and H-6 in sabandinin.
From the mother liquors of limettin and luvangetin, we obtained a compound of blue
fluorescence and m.p.
the i.r. spectrum of which is that of a simple coumarin
with free hydroxyl groups (
3520, 1695, 1572, 826 cm-‘). Its
absorptions indicate
that probably bears a substituent and
structure is now under investigation,
an OR group (see Experimental). Its complete
EXPERIMENTAL
The m.ps, determined on a Kofler block, are uncorrected. Solvent used for recrystallizing coumarins was
light petroleum unless otherwise stated. The spectra were obtained in and the
i.r. spectra in nujol. The NMR spectra were run in with TMS as internal standard. Column chromato-
graphy was carried out on alumina Merck, activity II-III, TLC on silica gel Merck, and PC on
No. 1, ascending technique.
Extraction and Chromatography of Coumarins
The cortex (1.46 kg) of the roots of
L. fil. was extracted with boiling
and the extract
steam-distilled. The composition of the essential oils thus obtained is published elsewhere.* The remaining
residue was first extracted with light petroleum and then with benzene, the results of the latter being
published
tographed on alumina
The viscous oil
g) obtained from the extract with light petroleum was
kg) eluting withlight petroleum, mixturesof light petroleum-benzene,andbenzene.
Methyl Ether (I)
Eluted with light petroleum, blue
fluorescence, m.p. 70” (from
Found: C, 76.98;
7.75.
297
for
M+-Me), 285
285 sh
(mol. wt. 312); C, 76.92; H, 7.75%. MS: M+ 312 (95%); prominent ions m/e
M+
269
CO, Me).
nm(3.14).
(log
223
245 sh
298 sh
332 (4.36);
1720, 1620, 1573,
1268, 1196, 1122, 1025, 988,905,
cm-r. NMR: Table 1.
W.
S. V.
and P. S. SANTHANAM, Phytochem. 9,891 (1970).

1625
Sabandinin and other coumarins isolated from the roots of
Acid Treatment of I:
Gravelliferone methyl ether
for 1 hr at 100”. The solution was cooled, diluted with
(IZ)
g) dissolved in
(5 ml) was treated with
(3 drops)
and extracted with ether. After washing the
organic layer with
and aq.
the solvent was evaporated and the residue chromatographed,
yielding four compounds, one of them identified as
fluorescence. NMR: Table 1.
(II) showing blue
Tetrahydrogravelliferone Methyl Ether (ZZZ)
Hydrogenation of I with
at room temp. under atm. press. gave the tetrahydro derivative
fluorescence which did not crystallize. (log 225 244 sh
298 sh 334 (446); 268 (3.28). 1710, 1617, 1582, 1275, 1255,
NMR: Table 1:
(III) as viscous oil of
255 sh
284 sh
Xanthyletin, Furopinnarin (IV), Pinnarin (VI), Limettin and Luvangetin
They were identified by direct comparison with authentic samples (mixed m.p.,* TLC, PC,
i.r.,
NMR). MS of pinnarin (VI):
M+-Me), 247
205
274 (78%; mol. wt. required for
274); prominent ions m/e 259
231
M+-CO, -Me), 219 M+-CO, -CH=
NMR of IV and VI: Table 1.
Acid Treatment of Furopinnarin
Bergapten (V)
IV (102
was treated as mentioned above for I. Chromatography yielded bergapten (50 mg) identified
by direct comparison with authentic material (mixed m.p., TLC, PC;
NMR: Table 1.
and i.r. spectra superposable).
Benahorin (VII)
Oily substance eluted with light petroleum-benzene (1: 2) between the fractions which contained pinnarin
and those with limettin. Sparingly soluble in light petroleum, it crystallized with difficulty, after several days,
from
containing traces of
m.p.
and was identified by comparing it with an authentic
sample.’ Found: C, 71.73; H, 5.57.
for
(mol. wt. 284): C,
H, 5.67%. MS:
241
284 (100%); prominent ions m/e 269
Me, CO). I,, (log
1720, 1580, 1278, 1168, 1104, 1058, 1002, 834, 765
Acid Treatment of VII: Xanthotoxin
Benahorin
monitoring the reaction by TLC. Chromatography of the residue yielded, besides starting material,
toxin (50 mg) identified by direct comparison with an authentic sample (mixed m.p., TLC, PC;
i.r. spectra superposable). Greenish yellow
Me), 257
313 (409);
226
251
264
236
NMR: Table 1.
261
280 nm
g) was treated as described above for I, but heating the mixture for 2 hr at
and
and
fluorescence, m.p. 146-147”. NMR: Table 1.
Tetrahydrobenahorin
VII (0.25 g) dissolved in
(50 ml) was hydrogenated with 10%
(0.20 g) at room temp. under
fluorescence and m.p.
atm. press. yielding the tetrahydro derivative (IX), of strong pale blue
(from
254
Found: C,
264 333 sh
H, 7.08.
343 (4.48);
required: C, 70.81: H, 690%.
249 260 278
NMR: Table 1.
(log
230
(3.46).
1715, 1567,
1345, 1278, 1242, 1142, 1106, 1082, 1020,993, 978, 830, 765
from Bergapten (V)
Light petroleum-benzene (1: 5) eluted a crystalline product which by TLC was shown to consist of two
Separation of Sabandinin
compounds of greenish yellow fluorescence, one of them identified as bergapten (TLC, PC). As they
over
could not be separated by column chromatography, the mixture (70 mg) was hydrogenated in
10%
at room temp. and atm. press. On chromatography of the resulting product, light
benzene (1: 2) eluted sabandinin
dihydrobergapten (with hydrogenated
the second compound of the original mixture, and benzene eluted
ring). The latter had intense blue
fluorescence and m.p.
and i.r. spectra
166” and was compared with an authentic sample (mixed
TLC, PC;
Sabandinin (X)
193-194” (ivory plates). Found: C,
H,
required: C,
330 sh (4.00)
1098, 1045, 942, 878, 830, 810
H, 364%.
(log 202
212 sh
238
257 sh
317
230 270
1725, 1622, 1580, 1395, 1300, 1247, 1210,
NMR:
Table 1.
Recrystallized from benzene, furopinnarin (m.p. 128-129”) and pinnarin (m.p. 173-174”) give some-
what higher m.ps than those published earlier (124-125” and

1626
A. G.
R.
and I. JARAIZ
Hydroxycoumarin,
From the mother liquors of limettin and luvangetin was obtained a colorless compound (8
of m.p.
221,
130-132” (from benzene) and blue
242 sh, 296 sh, 262 nm.
fluorescence which by TLC and PC was shown to be
1194,
780
Acknowledgements-The authors thank Prof. J.
methyl ether and Dr. Seibl, for the mass spectra of the remaining compounds, Dr. J. L.
for running the NMR spectra, and Dr. of the Centro de Quimica Organica,
Madrid, for carrying out the elementary analyses. This study was performed with the financial support
granted by the Excmo. Insular de Gran to one of us (R.E.R.).
for the mass spectrum of