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Structure of salvigenolide, a novel diterpenoid with a rearranged neo-clerodane skeleton from salviafulgens
Tcnahebon Vd 41, No 16. pi 3213 to 3217.1985
muted IIItit
awwalo/t5
htua
s300+00
Q m5hcpaFm96Ld.
STRUCTURE OF SALVIGENOLIDE,
A NOVEL DITERF’ENOID WITH A REARRANGED
NEO-CLERODANE SKELETON FROM SALVIA
BALDOMERO ESQUIVEL,
JORGE CARDENAS,
MANUEL SORIAhO-GARCIA
Institute de Circuit0 Exterior,
Qufmica, Cludad
and
LYDIA
Unlversldad Unlversltaria,
FULGENS
ALFRED0 TOSCANO,
RODRIGUEZ-HAHN *
National Authoma Coyoach 04510,
de Mkxlco, Mkxlco, D
F
(Recewd m USA 21 January 1985)
Abstract - From the aerial parts of SU&U @&aS Cav (Labiatae) diterpenoid with a rearranged n&J-clerodane skeleton was isolated novel compound named salvigenolide, showed a six - seven A/B ring with a ti fussion A probable biogenetic route is proposed structure and relative stereochemistry as in 1, were established spectroscopic means and X-ray diffraction analysis
In recent studies
1
antifungal family over
years,
is well ’
Lag 6 clerodane
diterpenoids
In this diterpenoid &&cti
paper,
were isolated
paper we describe with a novel
Cav
(SC&VU,
Salvigenolide
plants
Benth
Fulgentes.
a furan
ring
1501,
The ‘Ii NktBspectrum ring
A singlet triplet
at 6 2 05 (31) at 6 5 3
shoved a longe-range
*
871 cm-‘),
Author
Epling) Its
I)
of
was ascribed
with
culinary
from Sathamti~odoh.a
acid
was studied of
isolated
product,
IR spectrum
and two new
salvigenolide
0,
from the aerial
mp 218-22O’C.
exhibited
functions
salvigenolide functions
to an acetate
This multiplicity, indicatedi’
to whom correspondence
or
MO-
a parts
new of -S&U
of Mexico
and showed molecular
the characteristic
(1771 and 1761 cm-‘),
absorption an ester
for
carbonyl
groups
18 19 - elide.
coupling
or
Labiatae
in our country
a shrub which grows in the valley
two y-lactone
of hydroxyl
(Table
and an a,B-unsaturated
skeleton,
as a crystalline
Cr2H2207 by mass spectrometry (3140.
species,
and stereochemistry
flu-clerodane
(1) was isolated
and the absence
In Mexico,
’
formula
(1743 cm-i)
and biological antitumor
hallucinogens’
of melisodoric
related
r
the largest
medicine,’
the structure
chemical
antifeedant,
family
which is one of
, a closely
of
show
of this
are used as folk
the structure
rearranged
section
which
from some plants
we described
he&h
S&xa
have been the subject
diterpenoids
by genus Sch~,
mainly
Some of these
In a previous Recently
family
have been isolated
represented, 3
of Labiatae
of bi and tricyclic
properties,
257 species
herbs
plants
A variety
a new This system Its by
should
and the fact that
(L). very
3213
co-n
that none of
for
a @substituted
in clerodane
group whose gaminal
the acetate
be addreaaad
showed signals
proton
furan
type diterpenoids was observed
the C-19 protons
(see
Table
‘*’ as I)
group must be bound to C-6 and 8 axial
a
B ESQUIVEL ef al
3214
A broad
singlet
These requirement8 function
at 6 6 0 was attributed are satisfied
of r
(see
The absence
oxygen at C-12 spectra
of clerodane the y-lactone
1 (Table
I) was ascribed showed that
to it,
133 2 observed
it
singlets
This fact rearranged
in the 13C N?JRspectrum of clerodane
due to C-5 and C-9.
and the analysis clerodane
singlet
to the C-20 vinylic
is bound to a fully
of
of 1 (Table
salvigenolide
II)
the data presented,
25 1 1.
23 t 24 93 t
26 1 t
c3
I40 8 (d)
14, 89 d
2, c4 t
142 8 d
to this
L3J 8 I
C.
133 rn(sl
133 64 I
44 98 d
46 3x91
46 75 I
16 08 I
49 62 I
C6
71 4Z(dl
7, 8,
75 5 d
7s 9 d
C?
JO 02(t)
30 19 t
30 69 t
2-3 9, t
c-a
39 32161
39 6 6
37 83 d
121 16 I
C9
135 22 I’.
*
133 5 (rP
134 6 I**
C 10
39 32(d)
39 4 d
c-11
133 2 (I)**
133 6 I**
133 87 I.’
C-12
75 11(d)
15 21 d
75 03 d
C ,3
I24 lS(sl
124 9 I
124 10 I
121 a,
108 54 d
108 63 d
20 ,,
d
salvigenolide
23 3 * 38 30 d 169 3 I 82 75 d s
C-14
106 44(d)
109 16 d
C-15
1.4 76(d)
145 1, d
144 69 d
I.5
t-16
140 Wld)
140 7 d
14, 10 d
I37 46 d
c 17
176 69(s)
I77 0 I
176 6 s
II,
t-n
166 44(s)
169 I
177 9 I
I66 18,
04 d 29 s
C-19
68 99(t)
69 23 t
69 09 t
66 8 t
C-26
15 7 (PI
IS 10 p
16 67 P
I4 28 9
169 3 I MYlQ
169 4 I 2019
double
1
(1) -
of
coupled
at 6 133 5 and bond
in the literature.7-11
u2t
c-5
protons
show
one at 6 48 3 which was assigned that
NMR
the carbonyl
of vinylic
skeleton
25 5 t**
for
in the’H
Two spr singlets
were assigned
suggested
observed
at 6 1 6 in the iii NMR spectrum
bond
described
oxygen
of a y-lactone
group with the alcoholic
frequently
The absence
double
bearing
proton
25 and 49% in the mass
C-17 was responsible
showed only
25 48(11
m B(P)
that
type diterpenoids
21 94(l)
C-22
the geminal
the lactone
(3H) observed
substituted
Cl
169 (11
of
methyl group
C-2
c-21
bound to a carbon
is
methyl group doublet. suggested
A broad
function
The 13C NMRspectra sp’
of a secondary
type diterpen0ids.l
group of
it
at m/e 81 and 95 in ratios
support l2 the existence
experimental)
proton
we assume that
The fragments
(v max 1760 CID-~)
spectra
to an allylic
by H-12 if
possesses
two
to C-5 a
Strncturc of salwgenohde
X-ray
diffraction
analysis
of a single
crystal
of salvigenolide
3215
revealed
the correct
structure
and relative stereochemistry as shown in 1 The molecular structure with numbering scheme is illustrated in Fig molecule comprises an unusual system of six-seven-five m-fused (5). 84 6 (4)" and 62 6 (6). -1 8 (5)". respectively
1
The
rings with JXVU
salvigenolide angles of -19 0
The cyclohexene ring takes a distorted sofa
conformation and the C(2)-C(3)-C(4)-C(5) part is nearly planar with a torsion angle of 3 5 (7)" The cycloheptene ring adopts a conformation of the chair type with an approximate mirror plane through the C-6 atom and their torsion angles in this ring are close to those of the cycloheptene ring in the triterpene 3f3-methoxy-21-ketod13-serratene13 bromobenzoate I4 respectively
and deacetyl dihydro
gaillardin p-
Both y-lactone rings have the envelope conformation with flaps at C(5) and C(17).
The furan ring is planar. within the limit of experimental error
The y-lactone
ring containing the 0 (5) atom and the acetate group at C(6) are oriented to minimize transannular repulsions between their oxygen atoms group is 102 S(5)'
The angle between normals to the planes of the ring and the
The acetate group at C(6) lies almost perpendicular to the cycloheptene ring
(torsion angle, C(21)-0(1)-C(6)-C(5) = 107 4 (5)") serving to bring this group well clear off the ring system
The molecules are held in the crystal by van der Waals forces
Fig
1
A molecule of salvigenolide showing the atom labelling
Catalytic hydrogenation of salvigenolide 1, gave the dihydroderivative 2
The configuration
shown for C-4, was deduced by comparison of the 13C NMR spectrum of 2 (Table II) with literature data for similar structures lo
Structure
ofsalngenohde
3217
mp 248-25O'C dec from EtOAc, loI%" -206 (c 0 21, MeGH),_ UV (MeOH) X, 210 nm (log E 4 66), IR 3464. 1752, 1679, 1659, 1502. 874. 811. 781 cm ', 'H and irC NMR see Tables I and II (Nujol) Addition of 4 2 mg of Eu(fod), produced downfield shifts of the signals ascribed to respectively H-6 (A6-2 85). 2H-19 (A6-2 75). H-7a (A&1 5). H-3 (A6-1 4). 3H-20 (A&O 5). and H-12 (Aa-0 7) MS (direct inlet) m/s (rel intensity) 356 (M+. 13 4). 327 (14). 326 (go). 95 (80). 91 (70). 81 (60). 79 (60). 77 (100 base peak) Cr0H2006 requires l4+ at m/z 356 (1 X-my N~U&WL~ detenmuratcon 06 .Sa$vqenoL.& C22Hrr07, space group P21212i with 2-4 and a-8 625(2), b-12 453(2). c-18 052(2)A, V-1938 9(4)i ' and the calculated density is 1 364 gem-r Intensities of 1500 indepgndent reflections were collected on a Nicolet R3 diffractometer using HoK, radiation (h-0 7107 A and 2Bma, - 45O) of which 1225 were considered to be observed The structure was solved by direct methods using SHBLXTL programs ia The trial struc[I>2 50(1)1 ture was refined by least-squares In the final refinement, anisotropic thermal factors were used for the non-hydrogen atoms and for the hydrogen atoms riding on the bonded carbon atoms with a fixed isotropic temperature factgr U-O 06 A The final R value is 0 050 The final difference map has no peaks greater than -0 2 eA-" and the isotropic extinction parameter is X-O 0029 I9 Achouikdgemti We are very grateful to Messrs R Villena. H Bojbrquer, L Velasco and A Cuellar for technical assistance We thank Dr T P Ramamoorthy. Botany Department, Instltuto de Biologla. UNAM, for botanical classification of the plant material REFERENCES AND NOTES 1
LCLX~JIOUJWL @.bn 1981, 12. 81, See for example (a) Camps. F , Coil. .J , Cortel. A Rev (b) Fayos. J , FernlndesGadea, F , Pascual. C , Perales. A , Piozzi. F , Rico, M , J &g Chem 1984, 49, 1789 and references cited therein, (c) Rodrfguez, B , Savona. G Hanson, J R In "Terpenoids and Steroids", The Chemical Society London Vol 11 and preceeding volumes Rev
Wagner. H
Ramamoorthy, T
6 7
Blount. J
Phy&xheru&y
9
Wagner, H
12 13
1977, 8, 16
Evot H
1964, 146, 141
, Arago'n, R ,
, Marroquin. J
Guti6rrez. M
S
, Watson, W
F
(in press)
Takahashi. S 22, 302
11
!$dn
Sy&
1, 1982, 2505 , Manchand, P S J them Sot Pedun Than6 Rodriguez-Hahn. L , MartLnez. G , Romo. J Rev LaXinoamen. Qu.231 1973, 4, 93 Esquivel. B , MBndez, A , Ortega, A , Soriano-GarcIa. H , Toscano. A , Rodriguez-Hahn. L
Ortega. A ,
a
10
PI
A , Gor&les, 1976, 30, 237
Dominguez, X P&w.& Mtica 5
Laaknoamen. P
Kurabayashi, M
,
Kitazawa, E
, Lotter, H , , Bruno, M , Savona, G , Pascual, C , Fujita, E , Uchida, I , Fujita, T Allen. F H , Trotter, J J Chem
Luteijn, J
,
,
Seitz, R
H , van Veldhuizer. A
,
Hers, W
,
Haruyama. H J
Chem
0%
de Groot. A
0%
Chem
Sot
Sot
P&/in
Phyxochemcs@
1983,
1978, 43, 3339 Red
1982, 19, 95
Phy&xhenu&y
Rodriguez. B J
Mug
, Ogiso, A
TJWU
1981, 20, 2259 1,
1974, 1547
(81, 1970, 721 Chem
Sot
14
Dullforce, T
15
A six-seven A/B ring system has been described as a solvolysis product derived from junceic acid, see Henderson, t4 S , Murray, R D H , MC Crindle. R , McMaster. D CAM J C~WI 1973, 51, 1322
16
The spectroscopic data and X-ray diffraction analysis of salvigenolide suggest a neo-clerodane type of stereochemistry according to the nomenclature proposed by Rogers, D , see Rogers, D , Una1.G G, Williams, D J , Levy, S V , Sim. G A , Joshi, B S , Ravindranath. K R J them Sot , Chem Commun 1979, 97
17
Kitazawa, E , Ogiso. A , Sato, A Tethahedmn Letter 1979, 1117
18
An integrated System for Solving, Refining and Sheldrick. G M (19gl) SHELXTL. revision 3 Displaying Crystal Structures from Diffraction Data. Unfv of Gbttingen, Federal Republic of Germany
19
A list of atomic parameters, bond distances and angles. anisotropic thermal parameters. torsion angles and Fo-Fc tables are deposited at the Cambridge Crystallographic Data Centre. U K
A
Sim, G
A , White. D
,
M
J
J
Kurabayashi. M
,
(8) 1971, 1399
Kuwano, H ,
Hata. T ,
Tamura. C
muted IIItit
awwalo/t5
htua
s300+00
Q m5hcpaFm96Ld.
STRUCTURE OF SALVIGENOLIDE,
A NOVEL DITERF’ENOID WITH A REARRANGED
NEO-CLERODANE SKELETON FROM SALVIA
BALDOMERO ESQUIVEL,
JORGE CARDENAS,
MANUEL SORIAhO-GARCIA
Institute de Circuit0 Exterior,
Qufmica, Cludad
and
LYDIA
Unlversldad Unlversltaria,
FULGENS
ALFRED0 TOSCANO,
RODRIGUEZ-HAHN *
National Authoma Coyoach 04510,
de Mkxlco, Mkxlco, D
F
(Recewd m USA 21 January 1985)
Abstract - From the aerial parts of SU&U @&aS Cav (Labiatae) diterpenoid with a rearranged n&J-clerodane skeleton was isolated novel compound named salvigenolide, showed a six - seven A/B ring with a ti fussion A probable biogenetic route is proposed structure and relative stereochemistry as in 1, were established spectroscopic means and X-ray diffraction analysis
In recent studies
1
antifungal family over
years,
is well ’
Lag 6 clerodane
diterpenoids
In this diterpenoid &&cti
paper,
were isolated
paper we describe with a novel
Cav
(SC&VU,
Salvigenolide
plants
Benth
Fulgentes.
a furan
ring
1501,
The ‘Ii NktBspectrum ring
A singlet triplet
at 6 2 05 (31) at 6 5 3
shoved a longe-range
*
871 cm-‘),
Author
Epling) Its
I)
of
was ascribed
with
culinary
from Sathamti~odoh.a
acid
was studied of
isolated
product,
IR spectrum
and two new
salvigenolide
0,
from the aerial
mp 218-22O’C.
exhibited
functions
salvigenolide functions
to an acetate
This multiplicity, indicatedi’
to whom correspondence
or
MO-
a parts
new of -S&U
of Mexico
and showed molecular
the characteristic
(1771 and 1761 cm-‘),
absorption an ester
for
carbonyl
groups
18 19 - elide.
coupling
or
Labiatae
in our country
a shrub which grows in the valley
two y-lactone
of hydroxyl
(Table
and an a,B-unsaturated
skeleton,
as a crystalline
Cr2H2207 by mass spectrometry (3140.
species,
and stereochemistry
flu-clerodane
(1) was isolated
and the absence
In Mexico,
’
formula
(1743 cm-i)
and biological antitumor
hallucinogens’
of melisodoric
related
r
the largest
medicine,’
the structure
chemical
antifeedant,
family
which is one of
, a closely
of
show
of this
are used as folk
the structure
rearranged
section
which
from some plants
we described
he&h
S&xa
have been the subject
diterpenoids
by genus Sch~,
mainly
Some of these
In a previous Recently
family
have been isolated
represented, 3
of Labiatae
of bi and tricyclic
properties,
257 species
herbs
plants
A variety
a new This system Its by
should
and the fact that
(L). very
3213
co-n
that none of
for
a @substituted
in clerodane
group whose gaminal
the acetate
be addreaaad
showed signals
proton
furan
type diterpenoids was observed
the C-19 protons
(see
Table
‘*’ as I)
group must be bound to C-6 and 8 axial
a
B ESQUIVEL ef al
3214
A broad
singlet
These requirement8 function
at 6 6 0 was attributed are satisfied
of r
(see
The absence
oxygen at C-12 spectra
of clerodane the y-lactone
1 (Table
I) was ascribed showed that
to it,
133 2 observed
it
singlets
This fact rearranged
in the 13C N?JRspectrum of clerodane
due to C-5 and C-9.
and the analysis clerodane
singlet
to the C-20 vinylic
is bound to a fully
of
of 1 (Table
salvigenolide
II)
the data presented,
25 1 1.
23 t 24 93 t
26 1 t
c3
I40 8 (d)
14, 89 d
2, c4 t
142 8 d
to this
L3J 8 I
C.
133 rn(sl
133 64 I
44 98 d
46 3x91
46 75 I
16 08 I
49 62 I
C6
71 4Z(dl
7, 8,
75 5 d
7s 9 d
C?
JO 02(t)
30 19 t
30 69 t
2-3 9, t
c-a
39 32161
39 6 6
37 83 d
121 16 I
C9
135 22 I’.
*
133 5 (rP
134 6 I**
C 10
39 32(d)
39 4 d
c-11
133 2 (I)**
133 6 I**
133 87 I.’
C-12
75 11(d)
15 21 d
75 03 d
C ,3
I24 lS(sl
124 9 I
124 10 I
121 a,
108 54 d
108 63 d
20 ,,
d
salvigenolide
23 3 * 38 30 d 169 3 I 82 75 d s
C-14
106 44(d)
109 16 d
C-15
1.4 76(d)
145 1, d
144 69 d
I.5
t-16
140 Wld)
140 7 d
14, 10 d
I37 46 d
c 17
176 69(s)
I77 0 I
176 6 s
II,
t-n
166 44(s)
169 I
177 9 I
I66 18,
04 d 29 s
C-19
68 99(t)
69 23 t
69 09 t
66 8 t
C-26
15 7 (PI
IS 10 p
16 67 P
I4 28 9
169 3 I MYlQ
169 4 I 2019
double
1
(1) -
of
coupled
at 6 133 5 and bond
in the literature.7-11
u2t
c-5
protons
show
one at 6 48 3 which was assigned that
NMR
the carbonyl
of vinylic
skeleton
25 5 t**
for
in the’H
Two spr singlets
were assigned
suggested
observed
at 6 1 6 in the iii NMR spectrum
bond
described
oxygen
of a y-lactone
group with the alcoholic
frequently
The absence
double
bearing
proton
25 and 49% in the mass
C-17 was responsible
showed only
25 48(11
m B(P)
that
type diterpenoids
21 94(l)
C-22
the geminal
the lactone
(3H) observed
substituted
Cl
169 (11
of
methyl group
C-2
c-21
bound to a carbon
is
methyl group doublet. suggested
A broad
function
The 13C NMRspectra sp’
of a secondary
type diterpen0ids.l
group of
it
at m/e 81 and 95 in ratios
support l2 the existence
experimental)
proton
we assume that
The fragments
(v max 1760 CID-~)
spectra
to an allylic
by H-12 if
possesses
two
to C-5 a
Strncturc of salwgenohde
X-ray
diffraction
analysis
of a single
crystal
of salvigenolide
3215
revealed
the correct
structure
and relative stereochemistry as shown in 1 The molecular structure with numbering scheme is illustrated in Fig molecule comprises an unusual system of six-seven-five m-fused (5). 84 6 (4)" and 62 6 (6). -1 8 (5)". respectively
1
The
rings with JXVU
salvigenolide angles of -19 0
The cyclohexene ring takes a distorted sofa
conformation and the C(2)-C(3)-C(4)-C(5) part is nearly planar with a torsion angle of 3 5 (7)" The cycloheptene ring adopts a conformation of the chair type with an approximate mirror plane through the C-6 atom and their torsion angles in this ring are close to those of the cycloheptene ring in the triterpene 3f3-methoxy-21-ketod13-serratene13 bromobenzoate I4 respectively
and deacetyl dihydro
gaillardin p-
Both y-lactone rings have the envelope conformation with flaps at C(5) and C(17).
The furan ring is planar. within the limit of experimental error
The y-lactone
ring containing the 0 (5) atom and the acetate group at C(6) are oriented to minimize transannular repulsions between their oxygen atoms group is 102 S(5)'
The angle between normals to the planes of the ring and the
The acetate group at C(6) lies almost perpendicular to the cycloheptene ring
(torsion angle, C(21)-0(1)-C(6)-C(5) = 107 4 (5)") serving to bring this group well clear off the ring system
The molecules are held in the crystal by van der Waals forces
Fig
1
A molecule of salvigenolide showing the atom labelling
Catalytic hydrogenation of salvigenolide 1, gave the dihydroderivative 2
The configuration
shown for C-4, was deduced by comparison of the 13C NMR spectrum of 2 (Table II) with literature data for similar structures lo
Structure
ofsalngenohde
3217
mp 248-25O'C dec from EtOAc, loI%" -206 (c 0 21, MeGH),_ UV (MeOH) X, 210 nm (log E 4 66), IR 3464. 1752, 1679, 1659, 1502. 874. 811. 781 cm ', 'H and irC NMR see Tables I and II (Nujol) Addition of 4 2 mg of Eu(fod), produced downfield shifts of the signals ascribed to respectively H-6 (A6-2 85). 2H-19 (A6-2 75). H-7a (A&1 5). H-3 (A6-1 4). 3H-20 (A&O 5). and H-12 (Aa-0 7) MS (direct inlet) m/s (rel intensity) 356 (M+. 13 4). 327 (14). 326 (go). 95 (80). 91 (70). 81 (60). 79 (60). 77 (100 base peak) Cr0H2006 requires l4+ at m/z 356 (1 X-my N~U&WL~ detenmuratcon 06 .Sa$vqenoL.& C22Hrr07, space group P21212i with 2-4 and a-8 625(2), b-12 453(2). c-18 052(2)A, V-1938 9(4)i ' and the calculated density is 1 364 gem-r Intensities of 1500 indepgndent reflections were collected on a Nicolet R3 diffractometer using HoK, radiation (h-0 7107 A and 2Bma, - 45O) of which 1225 were considered to be observed The structure was solved by direct methods using SHBLXTL programs ia The trial struc[I>2 50(1)1 ture was refined by least-squares In the final refinement, anisotropic thermal factors were used for the non-hydrogen atoms and for the hydrogen atoms riding on the bonded carbon atoms with a fixed isotropic temperature factgr U-O 06 A The final R value is 0 050 The final difference map has no peaks greater than -0 2 eA-" and the isotropic extinction parameter is X-O 0029 I9 Achouikdgemti We are very grateful to Messrs R Villena. H Bojbrquer, L Velasco and A Cuellar for technical assistance We thank Dr T P Ramamoorthy. Botany Department, Instltuto de Biologla. UNAM, for botanical classification of the plant material REFERENCES AND NOTES 1
LCLX~JIOUJWL @.bn 1981, 12. 81, See for example (a) Camps. F , Coil. .J , Cortel. A Rev (b) Fayos. J , FernlndesGadea, F , Pascual. C , Perales. A , Piozzi. F , Rico, M , J &g Chem 1984, 49, 1789 and references cited therein, (c) Rodrfguez, B , Savona. G Hanson, J R In "Terpenoids and Steroids", The Chemical Society London Vol 11 and preceeding volumes Rev
Wagner. H
Ramamoorthy, T
6 7
Blount. J
Phy&xheru&y
9
Wagner, H
12 13
1977, 8, 16
Evot H
1964, 146, 141
, Arago'n, R ,
, Marroquin. J
Guti6rrez. M
S
, Watson, W
F
(in press)
Takahashi. S 22, 302
11
!$dn
Sy&
1, 1982, 2505 , Manchand, P S J them Sot Pedun Than6 Rodriguez-Hahn. L , MartLnez. G , Romo. J Rev LaXinoamen. Qu.231 1973, 4, 93 Esquivel. B , MBndez, A , Ortega, A , Soriano-GarcIa. H , Toscano. A , Rodriguez-Hahn. L
Ortega. A ,
a
10
PI
A , Gor&les, 1976, 30, 237
Dominguez, X P&w.& Mtica 5
Laaknoamen. P
Kurabayashi, M
,
Kitazawa, E
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16
The spectroscopic data and X-ray diffraction analysis of salvigenolide suggest a neo-clerodane type of stereochemistry according to the nomenclature proposed by Rogers, D , see Rogers, D , Una1.G G, Williams, D J , Levy, S V , Sim. G A , Joshi, B S , Ravindranath. K R J them Sot , Chem Commun 1979, 97
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