Three further 1,9-diarylnonanoid 3-O-glycosides from Erica cinerea

Article abstract of DOI:10.1016/j.tetlet.2013.01.117

In addition to the six diarylnonanoids and diarylnonanoid 3-O-glucosides previously reported from Erica cinerea, the multistep chromatographic processing of the acetone extract of the fresh aerial parts resulted in the isolation of three more representatives as glycosides derived from either (-)-ericanone or (-)-α-ericadione. From the spectroscopic data, the new structures were elucidated as (-)-(3S,7S)-ericanone 3-O-β-d-xylopyranoside, (-)-(3S,7S)-3″-hydroxyericanone 3-O-β-d-glucopyranoside, and (-)-(3S)-3″-hydroxy-α-ericadione 3-O-β-d-glucopyranoside respectively. In the ¹H and ¹³C NMR spectra run in CD ₃OD, the latter metabolite was as (-)-α-ericadione 3-O-β-d-glucopyranoside, also found as a permanent mixture of the major s-trans (70%) and the minor s-cis (30%) conformers. Such result - in connection with the protic solvent - seems to have never been reported earlier for α-alkadiones. Moreover, mild acid hydrolysis of such a glucoside led directly to the 3,4-dehydrated aglycone moiety accompanied by its 6,7-dehydrated tautomer, according to two successive dehydrations of the anticipated aglycone. Furthermore, although missing in this species, the postulated β-ericadione continues to be regarded as an essential intermediate at the crossroads of the biogenesis of most of the E. cinerea 1,9-diarylnonanoids.

Full text of DOI:10.1016/j.tetlet.2013.01.117

Tetrahedron Letters 54 (2013) 1873–1876
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Three further 1,9-diarylnonanoid 3-O-glycosides from Erica cinerea q
Mourad Kaouadji a, , Bachir Bennini b, Albert J. Chulia b
⇑
a Département de Chimie, Faculté des Sciences et Techniques, 123 Avenue A. Thomas, F-87060 Limoges Cedex, France
b Laboratoire de Pharmacognosie et de Phytochimie, Faculté de Pharmacie, 2 Rue Docteur Marcland, F-87025 Limoges Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
In addition to the six diarylnonanoids and diarylnonanoid 3-O-glucosides previously reported from Erica
cinerea, the multistep chromatographic processing of the acetone extract of the fresh aerial parts resulted
Received 3 November 2012
Revised 23 January 2013
Accepted 28 January 2013
Available online 4 February 2013
in the isolation of three more representatives as glycosides derived from either (ꢀ)-ericanone or (ꢀ)-
a-
ericadione. From the spectroscopic data, the new structures were elucidated as (ꢀ)-(3S,7S)-ericanone
3-O-b-
D
-xylopyranoside, (ꢀ)-(3S,7S)-300-hydroxyericanone 3-O-b-
D
-glucopyranoside, and (ꢀ)-(3S)-300-
hydroxy-
a
-ericadione 3-O-b-D
-glucopyranoside respectively. In the 1H and 13C NMR spectra run in
Keywords:
Ericaceae
Erica cinerea
1,9-Diarylnonanoids
CD3OD, the latter metabolite was as (ꢀ)-
nent mixture of the major s-trans (70%) and the minor s-cis (30%) conformers. Such result —in connection
with the protic solvent— seems to have never been reported earlier for -alkadiones. Moreover, mild acid
a-ericadione 3-O-b-D-glucopyranoside, also found as a perma-
a
hydrolysis of such a glucoside led directly to the 3,4-dehydrated aglycone moiety accompanied by its
6,7-dehydrated tautomer, according to two successive dehydrations of the anticipated aglycone.
Furthermore, although missing in this species, the postulated b-ericadione continues to be regarded as
an essential intermediate at the crossroads of the biogenesis of most of the E. cinerea 1,9-diarylnonanoids.
Ó 2013 Elsevier Ltd. All rights reserved.
(ꢀ)-(3S,7S)-Ericanone 3-O-b-
D-
xylopyranoside
(ꢀ)-(3S,7S)-300-Hydroxyericanone 3-O-b-
D-
glucopyranoside
(ꢀ)-(3S)-300-Hydroxy-
a-ericadione 3-O-b-D-
glucopyranoside
The previous phytochemical investigation of Erica cinerea L.
fresh aerial parts’ acetone extract afforded the linear 1,9-diarylno-
nanoid (3S,7S)-ericanone (1), the partly cyclized (3S)-3,7-anhydro-
To compound 3, obtained as a white amorphous powder, ½a D22
ꢁ
ꢀ18.2 (c 0.018, MeOH), was assigned the molecular formula
C
26H34O9 by HRESMS (found: 513.2095; calcd: 513.2100 for
MeOH
6,7-dehydroericanone (5), their corresponding 3-O-b-
2 and 6 as well as (3S,6E)-6,7-anhydroericanone 3-O-b-
(7) and (3S)- -ericadione 3-O-b-
-glucoside (8).1,2 Continuation of
D
-glucosides
[M+Na]+). As predicted by the coincident UV spectra (k
nm:
max
D
-glucoside
280) and the very close chromatographic mobilities (TLC and
HPLC), the 1H and 13C NMR data (Table 1) showed a close relation-
ship with ericanone 3-glucoside (2).1 The difference of 30 amu
(CH2O) between them, was reflected in the 1H and 13C NMR fea-
tures relative to the sugar region revealing one oxycarbon less
for 3. Thus, the glucosyl unit in 2 was replaced by a pentosyl in
3. Mild acid hydrolysis of the latter metabolite gave (ꢀ)-ericanone
(1) and xylose which was determined by GC analysis of the TMSi
derivative. The identical 1H and 13C NMR data of the ericanone part
in 2 and 3, and particularly the downfield shifts of one oxymethine
(H-3: d 4.16, br quint, J = 6.3 Hz; C-3: d 76.8) supported including
a
D
the multistep chromatographic process of the ethyl acetate soluble
part, yielded three extra linear 1,9-diarylnonanoid 3-O-glycosides
3, 4, and 9, unknown in the plant kingdom.3 On the basis of
spectroscopic evidence (UV, MS, and NMR), the newly reported
compounds were determined to be derived from either (3S,7S)-eri-
canone or (3S)-a-ericadione. With the unusual a-alkadione type
structure for a natural product, metabolite 9 was like 8, split into
the major s-trans (70%) and the minor s-cis (30%) conformers in
NMR protic solvent. Such a behavior which is also shared by com-
mercially 2,3-pentanedione, seems to have never been described
this position in an ether linkage with the b-D
-xylosyl unit (H-1000:
for
a
-diketones. Finally, given the striking relationship between
d 4.28, d, J = 7.8 Hz). In the HMBC spectrum virtually similar to that
of 2, the 3J cross-peaks displayed by H-3 with the anomeric C-1000 (d
104.1) and in turn by C-3 with the anomeric proton confirmed this
all these 1,9-diarylnonanoids, they are therefore biogenetically
regarded as deriving from a mutual 3-hydroxy-5,7-diketo type pre-
cursor, namely b-ericadione.
attachment. On the basis of spectral evidence for a b-
oside,4–9 compound 3 was identified as the newly reported erica-
none 3-O-b- -xylopyranoside. Laevorotatory as 1 and 2, this
metabolite must also have the (3S,7S)-configuration.
Contrary to ericanone 3-O-b- -xyloside (3), compound 4, the
D-xylopyran-
D
D
most polar in this series differed from the reference compound 2
q
Part 13 in the series Phytochemistry of the Ericaceae.
Corresponding author. Tel.: +33 5 55 43 58 34; fax: +33 5 55 43 59 10.
E-mail address: mourad.kaouadji@unilim.fr (M. Kaouadji).
only by the aglycone moiety and particularly by the outer aromatic
⇑
MeOH
max
ring(s) as indicated by the UV spectrum: k
284 nm. With the
0040-4039/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2013.01.117

1874
M. Kaouadji et al. / Tetrahedron Letters 54 (2013) 1873–1876
HO
6"'
OH
HO
3"'
O
HO
1"'
OR1
O
OH
O
O
1'
1'
1"
1"
R2
4"
3
5
9
1
7
5
7
9
1
3
4'
4"
OH
4'
HO
OH
HO
7
1
2
3
4
R1 = R2 = H
R1 =
R1 =
R1 =
β
β
β
-D-Glc; R2 = H
-D-Xyl; R2 = H
-D-Glc; R2 = OH
OH
4"
HO
HO
6"'
OH
1"
3"'
O
9
HO
1"'
7
O
O
O
H
1'
1"
R
1'
1
5
7
9
3
1
5
3
O
4"
OH
4'
4'
O
HO
RO
5 R = H
6 R =
8
9
R = H
R = OH
β
-D-Glc
molecular formula C27H36O11 given by HRESMS (found: 559.2171;
signal pairs of diagnostic value for H-3, C-5, and C-6, respectively.2
calcd: 559.2211 for [M+Na]+) and ½a D19
ꢁ
ꢀ14.5 (c 0.012, MeOH),
With respect to the a-dione minor s-cis conformer signals (H-3: d
compound 4 showed only one oxygen atom more when compared
to 2. This heteroatom was located on an aromatic ring, since a p-
hydroxyphenyl unit in 2 was replaced by a catechyl ring, as indi-
cated by the 1H and 13C NMR data (Table 1). Indeed, in agreement
with the apparent UV bathochromic shift of 4 nm with respect to
both metabolites 2 and 3, the resulting 1,3,4-trisubstituted aro-
matic ring was fully characterized by the particular ortho-dioxy
system with two O-bonded quaternary C at d 146.1 (C-300) and d
144.2 (C-400). According to the HMBC spectrum, the catechyl part
was linked to C-9 as supported by the 3J cross peaks recorded be-
tween H2-9 (d 2.64 and 2.48) and both C-200 (d 116.3) and C-600 (d
120.7), and between H-8 (d 1.67) and C-100 (d 134.4). The remaining
p-hydroxyphenyl was still attached to C-1 as shown by the main 3J
connectivities displayed by C-10 (d 135.0) with H-2a (d 1.87) and H-
2b (d 1.77). Ultimately, the 3-O-glucosyl linkage was evidenced as
mentioned above for 3. From these results, the novel (3S,7S)-300-
4.16, br quint, J = 6.5 Hz; C-5: d 206.1; C-6: d 206.9),10 those of
the major s-trans conformer were, as previously reported for 8,
shifted upfield: a scarcely discernible move for H-3 (d 4.10, br
quint, J = 6.5 Hz;
shift (
D
d ꢀ0.06) contrasting with a more pronounced
D
d ꢀ12.7) for both C-5 (d 193.4) and C-6 (d 194.2). Without
neglecting H-bond consequences, the chemical shift variation of
the carbonyls was so high because these groups were directly af-
fected by the torsion angle around the inter-carbonyl bond, in
terms of steric hindrance and anisotropy. To conclude, such a per-
manent conformational equilibrium in CD3OD —excluding a possi-
ble mixture of other different diones (b-,
c
- and/or d-)— was of
course supported by joint C-atoms —C-
a
,
a0 and C-b,b0— close to
the 5,6-dione bifunction for both conformers, namely C-3 (d
76.8), C-4 (d 44.8), C-7 (d 41.1), and C-8 (d 46.4).2
As previously reported, the
a-ericadione bifunction is unusual
in the natural open-chain polyketides —1,7-diarylheptanoids and
hydroxyericanone 3-O-b-
uted to laevorotatory 4.
D-glucopyranoside structure was attrib-
1,9-diarylnonanoids— and most likely in long-chain natural prod-
ucts in general in that it has an
a
-alkadione structural feature.2
In comparison with 8,2 glycoside 9 was also isolated as a viscous
mass from a methanol solution. With a lower mobility on silica gel
TLC, it exhibited a similar UV spectrum as well as quasi-coincident
1H and 13C NMR spectra in CD3OD (Table 1). Except for the variant
aromatic region, all other NMR signals were superimposable. They
really supported mixed conformers as for 8, split into the major s-
trans (70%) and the minor s-cis (30%). Owing to the molecular for-
mula C27H34O11 established by HRESMS (found: 557.2151; calcd:
557.2211 for [M+Na]+) indicating 16 amu more, glucoside 9 was
consequently considered as the oxy derivative of 8. Once again,
the only difference was the replacement of one p-hydroxyphenyl
unit in 8 by a catechyl ring attached to C-9 as reported above for
4. Hence, the new 1-(p-hydroxyphenyl)-9-(3,4-dihydroxyphenyl)-
In CD3OD, H-bonds between the protic solvent and each carbonyl
group must play a key role on the ongoing balance between the
major s-trans and the minor s-cis rotamers. The stability of the lat-
ter species is probably enhanced by the reduced repulsive effect
between the carbonyl oxygen atoms. However, no reference in
the literature relative to the NMR of simple a-alkadiones, suggests
mixed conformers for such products because the spectra are
usually run in CDCl3.9,11–15 In order to confirm clearly the above
mentioned protic solvent effect, the 13C NMR of available 2,3-pen-
tanedione was undertaken in CDCl3 and CD3OD respectively.16
Contrary to the expected five signals in the aprotic solvent, among
which the carbonyls belonging to the unique s-trans species (C-2: d
197.5; C-3: d 199.8), five more signals were exhibited in the protic
solvent. They suggested unambiguously mixed conformers in the
permanent ratio 70:30. Each one was characterized by a signal
pair: d 198.7 (C-2) and d 200.9 (C-3) for the major s-trans and d
3-hydroxynonan-5,6-dione 3-O-b-
D
-glucopyranoside structure
-ericadione 3-O-b- -gluco-
was assigned to 9. Named 300-hydroxy-
a
D
side, this metabolite was like 8 with the (3S)-configuration accord-
ing to ½a 2D2
ꢁ
ꢀ10.7 (c 0.075, MeOH). The mixed conformers for such
209.8 (C-2;
Dd +11.1) and d 211.8 (C-3; Dd +10.9) for the minor
a product were obviously characterized by the three distinct NMR
s-cis. This equilibrium was maintained without any change even

M. Kaouadji et al. / Tetrahedron Letters 54 (2013) 1873–1876
1875
Table 1
13C NMR (125 MHz) and 1H NMR (500 MHz) data for ericanone 3-xyloside (3), 300-hydroxyericanone 3-glucoside (4) and major s-trans-300-hydroxy-
CD3OD (d ppm; J Hz)
a-ericadione 3-glucoside (9) in
C/H
3
4
9
13C
1H
HMBC
13C
1H
HMBC
13C
1H
HMBC
1
2
31.4
38.6
2.59 m
1.80 br hext (7.0)
1.72 m
4.16 br quint (6.3)
2.81 dd (16.7; 7.3)
2.56 m
C-3; C-20,60
C-4; C-10
C-4; C-10
31.4
38.5
2.58 m
1.87 br hext (7.5)
1.77 m
4.20 br quint (6.4)
2.84 dd (16.8; 7.2)
2.56 m
C-3; C-20,60
C-4; C-10
31.4
38.4
2.64 m
1.87 m
1.79 m
4.10 br quint (6.5)
2.62 m
C-3; C-20,60
C-4; C-10
C-4; C-10
C-4; C-10
3
4
76.8
49.5
C-1; C-5; C-1000 76.4
49.2
C-1; C-5; C-1000
76.8
44.8
C-1; C-5; C-1000
2.50 dd (16.1; 6.4)
5
6
7
8
9
211.0
52.0
68.1
40.5
31.9
211.2
51.9
68.1
40.4
32.1
193.4
194.2
41.1
2.60 m
2.58 m
4.00 br quint (6.2)
1.65 dt (8.0; 6.1)
2.62 m
C-5; C-9
C-100
4.03 br quint (6.3)
1.67 dt (8.0; 6.3)
2.64 m
C-5; C-9
C-100
2.53 t (8.1)
2.77 m
2.73 t (7.3)
C-5
46.4
C-6; C-100
C-6; C-200; C-600
C-7; C-200,600
C-7; C-200,600
C-7; C-200; C-600 32.1
2.53 m
2.48 m
C-7; C-200; C-600
10
134.4a
135.0
134.7
130.7
116.1a
156.3
133.7
20,60 130.4b 6.97 d (8.4)
C-1; C-40
C-10
130.4 7.02 d (8.5)
116.1 6.67 d (8.5)
156.3
134.4
116.3 6.63 d (2.0)
146.1
C-1; C-40
C-10
7.02 d (8.5)
6.68 d (8.5)
C-1; C-40
C-10
30,50 116.1
6.65 d (8.4)
40
100
200
300
400
500
600
b-
1
2
3
4
5
156.4c
134.2a
130.3b 6.97 d (8.4)
C-9; C-400
C-100
C-9; C-400; C-600 116.4
6.63 d (2.0)
C-9; C-400
116.1
156.3c
116.1
6.64 d (8.4)
C-100
146.2
144.6
116.5a
144.2
6.64 d (8.4)
C-100
C-9; C-400
116.6 6.66 d (8.0)
120.7 6.50 dd (8.0; 2.0)
C-100; C-300
6.65 d (8.0)
6.50 dd (8.0; 2.0)
C-100; C-300
C-9; C-200; C-400
130.3b 6.97 d (8.4)
C-9; C-300; C-400 120.6
D
-Xylosyl or glucosyl moiety
104.1
75.0
77.7
71.6
65.6
4.28 d (7.8)
3.11 br t (8.3)
3.37 t (8.8)
3.56 m
3.89 dd (11.3; 5.5)
3.25 dd (11.3; 10.5)
C-3
103.6 4.33 d (7.8)
C-3
103.2
75.2
78.0
72.0
78.2
4.34 d (7.7)
C-3
75.2
78.0
71.6
77.8
3.14 dd (9.0; 7.8)
3.32 dd (9.0; 7.5)
3.28 m
3.19 br t (8.0)
3.36 br t (8.8)
3.35 m
3.26 ddd (9.5; 5.2; 2.3)
3.26 ddd (9.7; 5.3; 2.4)
6
62.8
3.86 dd (12.0; 2.3)
3.69 dd (12.0; 5.2)
62.8
3.88 dd (11.8; 2.4)
3.72 dd (11.8; 5.3)
a–c
Values with the same superscript in one column may be interchanged.
up to the limit of the solvent boiling point. Thereby, the protic sol-
vent’s indisputable impact on the stability of the -dione s-cis con-
to lead mainly to open-chain metabolites and only secondarily to
the partially cyclized 3,7-anhydro-6,7-dehydroericanone. The lat-
ter would most likely be issued from a route based on 6,7-enolisa-
tion followed by cylization consecutive to 3,7-dehydration.
Conversely, the whole open long-chain group would be generated
in four steps: a stereospecific reductive process of the 7-carbonyl
leading to ericanone, then to 6,7-anhydroericanone after 6,7-dehy-
dration, followed by 6,7-epoxidation and finally by rearrangement
a
former is well proved since the signals do not collapse, even at such
elevated temperature.
Finally, instead of releasing the anticipated 300-hydroxy-
a-erica-
dione aglycone (C21H24O6), mild acid hydrolysis of glucoside 9 led
directly to a mixture of species in the ratio 2:1 (C21H22O5 and
C
21H20O4), corresponding most likely to the major 3,4-dehydrated
product 10 or its tautomer and to its 6,7-dehydrated tautomer
11.17 Alike
-ericadione, both compounds were characterized in
of the resulting a-epoxyketone to provide either a- and/or b-erica-
a
dione. In spite of a detailed phytochemical investigation of E. cine-
rea and to be consistent with this proposal, attempts to isolate the
postulated b-ericadione and/or its keto-enol tautomer as well as
the GC–MS analysis by the lack of the molecular ion and the per-
manent base peak m/z 107 (hydroxybenzylium).2,18,19
the a-epoxyketone intermediate have remained unsuccessful.
Unlike more than 300 1,7-diarylheptanoids distributed in 15
less or more evolved plant families,20 only 18 representatives of
1,9-diarylnonanoids are known. Up to now, they are restricted in
the plant kingdom to the title Erica and the archaic Myristica
(Myristicaceae) only, two genera far apart from each other on the
plant evolution scale. The former contains two aglycones along
with seven glycosides whereas the latter produces also a total of
nine metabolites but only as aglycones.1
O
OH
O
HO
HO
OH
10
O
C
C
Acknowledgment
OH
OH
The authors are grateful to Région Limousin for supporting a
part of this work.
11
References and notes
The close relationship between all the E. cinerea 1,9-diarylnona-
noids seems a priori to suggest a mutual 3-hydroxy-5,7-diketo-
type precursor (b-ericadione) involved in two distinct pathways
1. Bennini, B.; Chulia, A. J.; Kaouadji, M.; Fondanèche, P.; Allais, D. P. Tetrahedron
Lett. 2011, 52, 1597–1600. and references cited therein.
2. Kaouadji, M.; Bennini, B.; Chulia, A. J. Tetrahedron Lett. 2012, 53, 3663–3667.

1876
M. Kaouadji et al. / Tetrahedron Letters 54 (2013) 1873–1876
3. Isolation procedure: The multistep chromatographic treatment of the previous
crude EtOAc extract (50 g) subjected to LH-20 CC packed in MeOH gave the
ahead fraction (4.9 g) reduced to 2.7 g after liquid–liquid partition with water.
The organic fraction was then subjected to polyamide MPLC eluted with the
mixture MeC6H5–Me2CO–MeOH (from 80:10:10 to 60:20:20) to provide
7.0 Hz, H-4a), 2.72 (m, H2-7), 2.64 (m, H-4b); 13C NMR (125 MHz, CD3OD) d:
206.9 (C-6), 206.1 (C-5), 103.5 (C-1000), 76.2 (C-3).
11. Levy, G. C.; Nelson, G. L. Carbon-13 Nuclear Magnetic Resonance for Organist
Chemists; Wiley Interscience: New York, 1972.
12. Mueller-Westerhoff, U. T.; Zhou, M. J. Org. Chem. 1994, 59, 4988–4992.
13. Suda, K.; Baba, K.; Nakajima, S.-i.; Takanami, T. Chem. Commun. 2002, 2570–
2571.
impure aglycones 1 and 5 in the ahead fractions and impure glycosides 2–4
1,2
and 6–9 in the last fractions.
Four fractions, issued from the previous step
were, after the usual work-up, selected for isolating these glycosides. Besides
surrounding absorbing materials for all, they were in the elution order, mainly
consisting of mixed 6–8, impure 9, mixed 2–3, and finally impure 4. The latter
glucoside (23 mg) was directly purified by reverse phase HPLC [Macherey–
Nagel NUCLEODUR 100-5 C18 ec (250 ꢂ 10 mm)] with 45% aq. MeOH. Minor
xyloside 3 (14 mg) was concentrated by repeated polyamide MPLC using a
gradient of the mobile phase MeC6H5–Me2CO–MeOH before being purified by
three successive semi-prep. reverse phase C18 HPLC eluted with the mixture
MeOH–H2O (from 40:60 to 60:40). Glucoside 9 (65 mg) was finally subjected to
14. Yamane, M.; Uera, K.; Narasaka, K. Bull. Chem. Soc. Jpn. 2005, 78, 477–
486.
15. AIST: RIO-DB/Spectral Database for Organic Compounds (SDBS).
16. 2,3-Pentanedione from Alfa Aesar: 13C NMR (100 MHz) d (CDCl3; 303 °K): 199.8
(C-3), 197.5 (C-2), 29.2 (C-4), 23.7 (C-1), 7.0 (C-5); d (CD3OD; from 303 °K up to
334 °K): 211.8 (C-3, s-cis), 209.8 (C-2, s-cis), 200.9 (C-3, s-trans), 198.7 (C-2, s-
trans), 30.4 (C-4, s-cis), 29.8 (C-4, s-trans), 23.7 (C-1, s-trans), 23.4 (C-1, s-cis),
7.9 (C-5, s-cis), 7.3 (C-5, s-trans).
17. Controlled acid hydrolysis of 300-hydroxy-
a-ericadione 3-glucoside (9): The sample
direct semi-prep. reverse phase HPLC [Merck LiChrospher 100 DIOL (10
l
m)
(8 mg) dissolved in MeOH (0.5 mL) was added to 3% HCl (10 mL). The mixture
was kept for 2 h at 35 °C and then cooled. Diluted with distilled water (25 mL),
the sample was extracted with EtOAc (3 ꢂ 10 mL). After the usual work-up, the
residue was subjected to LH-20 CC packed in MeOH to afford a mixture (3 mg)
of the major 10 and the minor 11.
250 ꢂ 10 mm] with the eluent mixture n-C6H14–iPrOH–MeOH in the ratio
72:08:20.
4. Suga, T.; Ohta, S.; Hirata, T.; Aoki, T. Chem. Lett. 1982, 895–898.
5. Sakurai, N.; Nagai, M.; Goto, T.; Inoue, T.; Xiao, P. Chem. Pharm. Bull. 1993, 41,
272–275.
6. Chen, J.; Gonzalez-Laredo, F.; Karchesy, J. J. Phytochemistry 2000, 53, 971–973.
7. Eskander, J.; Lavaud, C.; Pouny, I.; Soliman, H. S. M.; Abdel-Khalik, S. M.;
Mahmoud, I. I. Phytochemistry 2006, 67, 1793–1799.
18. 3,4-Anhydro-300-hydroxy- -ericadione (10): HRESMS for C21H22NaO5 [M+Na]+:
a
calcd 377.155945, found 377.135982; HRESMS for C21H23O5 [M+H]+: calcd
355.154000, found 355.154038; GC-EIMS (70 eV) m/z (%): 208 (5), 190 (12),
147 (8), 133 (24), 107 (100), 91 (18), 77 (45), 65 (12), 43 (92).
19. 1-(4-Hydroxyphenyl)-9-(3,4-dihydroxyphenyl)-non-3-en-6-yn-5-one (11):
HRESMS for C21H21O4 [M+H]+: calcd 337.143436, found 337.143097; GC-EIMS
(70 eV) m/z (%): 190 (5), 107 (100), 77 (25), 53 (5), 43 (43).
8. Liimatainen, J.; Karonen, M.; Sinkkonen, J. Phytochemistry 2012, 76, 178–183.
9. Breitmaier, E.; Voelter, W. Carbon-13 NMR Spectroscopy: High-Resolution
Methods and Applications in Organic Chemistry and Biochemistry, 3rd ed.; VCH:
Weinheim, 1987.
20. Lv, H.; She, G. Nat. Prod. Commun. 2010, 5, 1687–1708. and references cited
therein.
10. NMR signals with marked difference for the s-cis conformer of glucoside 9: 1
H
NMR (500 MHz, CD3OD) d: 4.16 (br quint, J = 6.5 Hz, H-3), 2.82 (dd, J = 16.8 and