Photochemical reaction of phenanthrenequinone with some new aurones derived from khellin and visnagin

Article abstract of DOI:10.1081/SCC-120003624

Phenanthrenequinone 2 and aurones 5a-h are potentially capable of undergoing an interesting photochemical reaction leading to the formation of the adducts 6a-h. The structures of the 1,4-dioxine derivatives 6a-h were firmly established on the basis of analytical data and spectroscopic evidences.

Full text of DOI:10.1081/SCC-120003624

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PHOTOCHEMICAL REACTION OF
PHENANTHRENEQUINONE WITH SOME NEW AURONES
DERIVED FROM KHELLIN AND VISNAGIN
A. A. Nada a , M. F. Zayed a , N. Khir El Din a , M. M. T. El-Saidi a & E. Hefny a
a National Research Centre , Dokki, Cairo, Egypt
Published online: 17 Aug 2006.
To cite this article: A. A. Nada , M. F. Zayed , N. Khir El Din , M. M. T. El-Saidi & E. Hefny (2002) PHOTOCHEMICAL REACTION
OF PHENANTHRENEQUINONE WITH SOME NEW AURONES DERIVED FROM KHELLIN AND VISNAGIN, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 32:9, 1293-1302, DOI: 10.1081/SCC-120003624
To link to this article: http://dx.doi.org/10.1081/SCC-120003624
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SYNTHETIC COMMUNICATIONS, 32(9), 1293–1302 (2002)
PHOTOCHEMICAL REACTION OF
PHENANTHRENEQUINONE WITH SOME
NEW AURONES DERIVED FROM
KHELLIN AND VISNAGIN
*
A. A. Nada, M. F. Zayed, N. Khir ElDin,
M. M. T. El-Saidi, and E. Hefny
National Research Centre, Dokki, Cairo, Egypt
ABSTRACT
Phenanthrenequinone 2 and aurones 5a–h are potentially
capable of undergoing an interesting photochemical reaction
leading to the formation of the adducts 6a–h. The structures
of the 1,4-dioxine derivatives 6a–h were firmly established on
the basis of analytical data and spectroscopic evidences.
The naturally occurring furocoumarin khellin 1a and visnagin 1b show
remarkable pharmacological properties.1–4 Khellin for example, has
attracted interest, being an antispasmodic and a coronary vasodilator of
promise, in the treatment of angina pectoris and bronchial asthma.5 Their
photoreactions have been extensively studied.
The photoreactions of phenanthrenequinone 2 have also been exten-
sively studied (vide infra). Thus, it appeared of interest to us to synthesize
some derivatives having the furochromone moiety and to carry out the
*Corresponding author.
1293
Copyright & 2002 by Marcel Dekker, Inc.
www.dekker.com

1294
NADA ET AL.
photoreactions of these compounds with phenanthrenequinone to obtain an
insight into the photoreaction behavior of these products and to produce
compounds with wider medicinal spectra and of new potentialities.6,7
Thus, khellinone 3a8 and visnaginone 3b9 were prepared by the action
of alkali on khellin 1a and visnagin 1b, respectively. Condensation of khel-
linone 3a with the p-chlorobenzaldehyde, p-nitrobenzaldehyde, p-methoxy-
benzaldehyde and 2,4-dimethoxy benzaldehyde produced the corresponding
chalcones 4a–d respectively. Similarly, chalcones 4e–h were produced by
condensation of visnaginone 3b with the respective aldehyde.
The chalcone structures 4a–h were assigned to the products by analyt-
ical and spectroscopic evidences as well as by analogy.10 Thus, the IR spec-
tra of the reaction products revealed the presence of C¼O absorption at
1
’1730 cmÀ1, and OH absorption at ’3460 cmÀ1 (cf. Exp.). The H NMR
spectrum of compound 4g taken as a representative example, showed two

PHENANTHRENEQUINONE AND AURONES
1295
singlets at d ¼ 3.70, 4.20 ppm, due to the two methoxyl groups. And a singlet
appeared at 6.75 ppm for visnagin proton, 6.90 and 7.60 ppm due to two
doublets for AB system, J ¼ 6 Hz for the aromatic protons of the 1,4-
disubstituted ring. While two doublets at 6.85 and 7.80 ppm, J ¼ 2 Hz for
the furan ring, 7.50 ppm due to one doublet for b-olefinic proton, a doublet
at 7.70 ppm due to a-olefinic proton and a signal at 12.85 ppm due to OH
1
proton. The H NMR spectra of chalcone structures 4a–h were confirmed
(cf. Exp.).
The preparation of aurones 5a–h was carried out via oxidation treat-
ment of compounds 4a–h utilizing hydrogen peroxide in alkaline medium.
Analytical and spectroscopic evidences characterized the resulting aurones
5a–h. In the mass spectra, molecular ion peaks observed for all the aurones
5a–h showed m/z ¼ [Mþ] corresponding to the molecular weight of the prod-
ucts. The IR spectrum of compound 5a reveals the presence of absorption
bands at 1700 cmÀ1 due to the frequency of the carbonyl group of the
coumaranone ring and at 1650 cmÀ1 due to conjugated unsaturated
ketone. Its mass spectrum, taken as a representative example showed an
1
ion peak at m/e ¼ 356.5 [Mþ]. The H NMR spectrum of this compound
showed two singlets at d ¼ 4.16 and 4.21 ppm due to two methoxy protons
and a singlet centered at d ¼ 6.85 ppm due to the CHR0 group. The two
doublets 7.30 and 8.05 ppm are due to the two CH protons of the furan
ring, J ¼ 2 Hz. The aromatic protons appeared as two doublets at d ¼ 7.60
and 7.95 ppm, 4H; AB system, J ¼ 6 Hz for the 1,4-disubstituted benzene
1
ring. The IR and H NMR spectrum of compounds 5a,c,e,f–h are given in
the experimental section. Moreover, compounds 5a–h are insoluble in alkali
and give negative ferric chloride reaction. It gave a deep red color with
concentrated sulfuric acid.10
Phenanthrenequinone 2 and aurones 5a–h are potentially capable of
undergoing an interesting photochemical reaction leading to the formation
of the adducts 6a–h. This reaction is carried out in a Pyrex vessel using high-
pressure Hg lamp (Philips HPK 125 W) in toluene as a solvent. The progress
of the reaction was followed by thin layer chromatography on silica plates.
The products obtained were separated by column chromatography on a
silica gel column. The 1,4-dioxine structure 6a–h was assigned to the prod-
ucts according to analytical and spectroscopic evidences.
Information found in the literature regarding the photochemical reac-
tion of phenanthrenequinone 2 with olefins is not in full agreement. Some
papers11,12 proved the formation of 1,4-dioxine derivatives 7, while others13
assigned the ketooxetane structure 8 to some of these adducts. However, it
was reported that both addition products (dioxine and oxetanes) were
produced simultaneously in other reactions.14–17 Stilbene, alicyclic olefins,
furocoumarines and xanthotoxin were investigated in these photoreactions.

1296
NADA ET AL.
The 1,4-dioxine derivatives 6a–h were obtained from the photochemi-
cal reaction of 2 and aurones 5a–h. This structure was firmly established on
1
the basis of analytical data, IR, H NMR and 13C NMR. The IR spectrum
of 6f, taken as a representative example, reveals the presence of an absorp-
tion band at 3460 due to hydroxyl group and at 1660 due to (C¼O) group.
The 1H NMR of this compound showed a singlet at d ¼ 4.03 ppm due to the
methylene protons. The two doublets for the bridgehead methine protons
overlapped in a complex pattern center at d ¼ 4.61ppm and the singlet at
4.37 ppm is due to the OCH3 protons. The aromatic protons of the
1,4-disubstituted benzene ring appeared as two doublets at d ¼ 7.25 and
8.12 ppm as AB system, J ¼ 6 Hz, whereas the 8 H of the phenanthrene
appeared as two triplets at 7.50 and 7.63 ppm and two doublets at 7.75
and 7.68 ppm. A signal appeared at d ¼ 7.55 ppm (1H) due to the aromatic
visnagin proton.
Moreover, compounds 6c,f,g were analyzed by 13C NMR using Bruker
AM-500, for further confirmation. The 13C NMR spectrum of compound 6f
taken as a representative example, showed in a clear pattern the assignment
of all carbon atoms in these molecules (cf. Experimental). Interestingly, the
bridged carbon atoms of these molecules were obtained in the range of
d ꢀ130 and 131 ppm.
Further evidence for the proposed structure comes from the mass
spectral data. The 1,4-dioxine derivatives 6a–h were characterized by a simi-
lar fragmentation pattern. The mass spectra of these photoadducts showed
clearly a loss of benzylic group substituents and hydroxyl group. The m/z
equals the composition of Mþ-C(OH)CH2C6H5( p)X and dominates the

PHENANTHRENEQUINONE AND AURONES
1297
electron impact and spectrum chart. The spectra of these compounds
revealed the presence of the biphenyl moiety at m/z ¼ 152 and the phenan-
threnequinone fragment at m/z ¼ 208. The formation of the 1,4-dioxine
derivatives 6a–h could be explained by assuming that the photoexcited phe-
nanthrenequinone reacted with aurones in a stepwise fashion most probably
via a biradical intermediate. The latter is stabilized to give 6. The reduction
of aurones may be achieved by hydrogen abstraction from the solvent.
EXPERIMENTAL
All melting points uncorrected were determined on an Electrothermal
Engineering LKD 6891apparatus. Nuclear magnetic resonance (NMR)
spectra were recorded on Bruker AM-500 spectrometers with 5-mm dual
frequency 1H-13C for compound 6c,f,g. The proton spectra were acquired at
500.14 MHz on the AM-500. CF3COOD was used as a solvent, unless
otherwise noted. The internal standard residual COOH signal in CF3COOD
at 11.5 ppm. The chemical shifts were reported in delta (d) units (ppm)
upfield from CF3COOD. The multiplicity patterns are s ¼ singlet,
1
d ¼ doublet, t ¼ triplet, m ¼ multiplet. For compounds 5a–h the H NMR
1
spectra were recorded on JEOL EX 270 NMR system for H NMR (NRC,
Cairo, Egypt). Typical conditions: spectral width ¼ 4000 Hz for 1H and a
flip angle of 45ꢁC. The chemical shifts are recorded in d ppm. Deuterated
dimethyl sulfoxide, which was, used as a solvent, referring to the internal
standard residual (CD3)2 signal in (CD3)2 SO2 at 2.50 ppm. 13C NMR spec-
tra were acquired at 125.76 MHz on the AM-500. Analytical thin layer
chromatography (TLC) was conducted by using plastic-backed, Fluka
DC-Alufolien Kieslgel, 0.2 mm silica plates. Preparative chromatographic
separations was carried out using column chromatography on silica gel G.
Mesh size 0.2–0.5 mm, 37–70 mesh (ASTM) E Merch, Darmstadt through
elution with toluene–ethylacetate (6 : 1v/v), in a suitable condition. Infrared

1298
NADA ET AL.
(IR) spectra were recorded on Zeiss Infrared spectrophotometer IMR 16
and were reported in wave numbers (cmÀ1).
Low resolution EI mass spectra (LRMS) were obtained using a
Shimadzu GC/MS-QP 1000 EX spectrometers at electron energy ¼ 70 eV.
The microanalysis were carried out at the microanalytical center, NRC,
Cairo. The microanalysis for the new compounds were in good agreement
with calculated values [C, H, ꢂ0.1]. Photolysis experiments were carried out
in Pyrex vessels using high-pressure lamps (Philips HPK 125 W) in toluene
as solvent and control experiments were carried out in the dark under
identical conditions.
The Preparation of Chalcones 4a–h
Generalprocedure: To a solution of 3a or 3b (0.01mole) in 30 ml
aqueous potassium hydroxide (50%); a solution of the appropriate aldehyde
(0.02 mole) in ethanol (30 ml) was added. After stirring at room temperature
for 12 h, the solution was neutralized with dilute acetic acid (10%). The
separated product was collected, washed with water and crystallized. 4a:
m.p. 128ꢁC; brownish crystals (from MeOH); 99% yield; nmax (cmÀ1
)
(KBr) 3450 (OH); dH (CDCl3) 4.10 (s, 3H, OCH3), 4.15 (s, 3H, OCH3),
7.40 and 7.85 (2d, 4H; AB system, J ¼ 6 Hz, aromatic protons of 1,4-
disubstituted benzene ring), 7.45–7.70 (4H; 1H, a-olefinic proton; 1H, b-
olefinic proton and 2H furan in a complex pattern), 12.6 (s, 1H, OH
proton); m/z 358 (Found: C, 63.61; H, 4.18. C19H15O5Cl requires C,
63.59; H, 4.18%). 4b: m.p. 185ꢁC; orange crystals (from MeOH); 99%
yield; nmax (cmÀ1) (KBr) 3460 (OH); m/z 369 (Found: C, 61.78; H, 4.08.
C19H15O7N requires C, 61.78; H, 4.06%). 4c: m.p. 124ꢁC; orange crystals
(from benzene); 98% yield; nmax (cmÀ1) (KBr) 3470 (OH); dH [(CD3)2SO]
3.75 (s, 3H, OCH3), 3.85 (s, 3H, OCH3), 3.95 (s, 3H, OCH3), 4.05 (s, 3H,
OCH3), 6.60 (s, 1H, aromatic proton), 7.10 (d, 1H, b-olefinic proton), 7.25
(d, 1H; J ¼ 2 Hz furan proton), 7.55 (s, 1H, aromatic protons), 7.65 (d, 1H;
J ¼ 2 Hz for furan proton), 7.70 (d, 1H, a-olefinic proton), 7.90 (s, 1H,
aromatic proton), 10.15 (s, 1H, OH proton); m/z 354 (Found: C, 67.81;
H, 5.08. C20H18O6 requires C, 67.79; H, 5.08%). 4d: m.p. 105ꢁC; reddish
crystals (from benzene); 95% yield; nmax (cmÀ1) (KBr) 3455 (OH); m/z 384;
(Found: C, 65.62; H, 5.20. C21H20O7 requires C, 65.62; H, 5.20%). 4e: m.p.
127ꢁC; orange crystals (from MeOH); 95% yield; nmax (cmÀ1) (KBr) 3435
(OH); m/z 328.5; (Found: C, 65.77; H, 3.93. C18H13O4Cl requires C, 65.75;
H, 3.95%). 4f: m.p. 250ꢁC; yellow crystals (from MeOH-benzene); 99%
yield; nmax (cmÀ1) (KBr) 3450 (OH); m/z 339 (Found: C, 63.73; H, 3.99.
C18H13O6N requires C, 63.71; H, 3.98%). 4g: m.p. 105ꢁC; yellow crystals

PHENANTHRENEQUINONE AND AURONES
1299
(from benzene); 97% yield; nmax (cmÀ1) (KBr) 3460 (OH); dH (CDCl3) 3.70
(s, 3H, OCH3), 4.20 (s, 3H, OCH3), 6.75 (s, 1H; visnagin proton), 6.90 and
7.60 [(2d, 4H; AB system, J ¼ 6 Hz) aromatic protons of 1,4-disubstituted
benzene ring], 6.85 and 7.80 (2d, 2H; J ¼ 2 Hz, furan ring), 7.5 (d, 1H,
b-olefinic proton), 7.70 (d, 1H, a-olefinic proton), 12.85 (s, 1H, OH
proton); m/z 324 (Found: C, 70.37; H, 4.93. C19H16O5 requires C, 70.37;
H, 4.93%). 4h: m.p. 135ꢁC; orange crystals (from benzene); 96% yield; nmax
(cmÀ1) (KBr) 3460 (OH); m/z 354 (Found: C, 67.73; H, 5.08. C20H18O6
requires C, 67.79; H, 5.08%).
The Preparation of Aurones 5a–h
Generalprocedure: To a sodium hydroxide solution (20 ml, 10%), a
solution of the chalcone derivatives 4a–h (1g) in pyridine (10 ml) was added.
Hydrogen peroxide solution (15 ml, 20 vol. %) was gradually added to the
externally cooled alkaline solution and the reaction mixture was left in the
refrigerator for 4 days. The precipitated material was filtered, washed with
water, dried and crystallized from a suitable solvent. 5a: m.p. 235ꢁC; yellow
crystals (from benzene); 65% yield; nmax (cmÀ1) (KBr) 1700 (C¼O), 1650
(conjugated unsaturated ketones); dH [(CD3)2SO] 4.16 (s, 3H, OCH3), 4.21
(s, 3H, OCH3), 6.85 (s, 1H, for CHR0), 7.30 (d, 1H, furan proton, J ¼ 2 Hz),
7.60 and 7.95 [(2d, 4H; AB system, J ¼ 6 cps) for aromatic protons of 1,4-
disubstituted benzene ring], 8.05 (d, 1H, furan proton, J ¼ 2 Hz); m/z 365.5
(Found: C, 63.95; H, 3.64. C19H13O5Cl requires C, 63.95; H, 3.64%). 5b:
m.p. 304ꢁC; yellow crystals (from benzene); 85% yield; nmax (cmÀ1) (KBr)
1700 (C¼O), 1655 (conjugated unsaturated ketones); m/z 367 (Found: C,
62.14; H, 3.56. C19H13O7N requires C, 62.12; H, 3.54%). 5c: m.p. 155ꢁC;
brown crystals (from MeOH); 75% yield; nmax (cmÀ1) (KBr) 1710 (C¼O),
1650 (conjugated unsaturated ketones); m/z 352 (Found: C, 68.18; H, 4.54.
C20H16O6 requires C, 68.18; H, 4.54%). 5d: m.p. 185ꢁC; brownish crystals
(from benzene); 75% yield; nmax (cmÀ1) (KBr) 1700 (C¼O), 1650 (conju-
gated unsaturated ketones); m/z 382 (Found: C, 65.94; H, 4.69. C21H18O7
requires C, 65.96; H, 4.71%). 5e: m.p. 188ꢁC; yellow crystals (from
benzene); 65% yield; nmax (cmÀ1) (KBr) 1700 (C¼O), 1655 (conjugated
unsaturated ketones); m/z 362.5 (Found: C, 66.15; H, 3.36. C18H11O4Cl
requires C, 66.15; H, 3.36%). 5f: m.p. 275ꢁC; orange crystals (from
benzene); 95% yield; nmax (cmÀ1) (KBr) 1705 (C¼O), 1645 (conjugated
unsaturated ketones); dH (CDCl3) 4.45 (s, 3H, OCH3), 6.75 (s, 1H, visnagin
proton), 7.00 (d, 1H; J ¼ 2 Hz furan proton), 7.55 (d, 1H; J ¼ 2 Hz furan
proton), 8.00 and 8.30 [(2d, 4H; AB system, J ¼ 6 Hz) aromatic protons of
1,4-disubstituted benzene ring], 8.10 (s, 1H, CHR0); m/z 337 (Found: C,

1300
NADA ET AL.
64.09; H, 3.26. C18H11O6N requires C, 64.09; H, 3.26%). 5g: m.p. 201ꢁC;
orange crystals (from benzene); 70% yield; nmax (cmÀ1) (KBr) 1705 (C¼O),
1650 (conjugated unsaturated ketones); dH [(CD3)2SO] 3.85 (s, 3H, OCH3),
4.30 (s, 3H, OCH3), 6.75 (s, 1H, CHR0), 7.05 and 7.93 [(2d, 4H; AB system,
J ¼ 6 Hz) aromatic protons of 1,4-disubstituted benzene ring], 7.30 (d, 1H,
furan proton, J ¼ 2 Hz), 7.35 (s, 1H, visnagin proton), 8.00 (d, 1H, furan
proton, J ¼ 2 Hz); m/z 322 (Found: C, 70.80; H, 4.34. C19H14O5 requires C,
70.80; H, 4.34%). 5h: m.p. 205ꢁC; orange crystals (from benzene); 70%
yield; nmax (cmÀ1) (KBr) 1695 (C¼O), 1645 (conjugated unsaturated
ketones); dH [(CD3)2SO] 3.75 (s, 3H, OCH3), 3.80 (s, 3H, OCH3), 4.35 (s,
3H, OCH3), 6.65 (d, 1H, furan proton, J ¼ 2 Hz), 6.70 (s, 1H, visnagin
proton), 7.00 (s, 1H, CHR0 proton), 7.40 (s, 1H, aromatic proton), 7.30
and 8.15 [(2d, 4H; AB system, J ¼ 6 Hz) aromatic protons 1,4-disubstituted
benzene ring], 7.95 (d, 1H, furan proton, J ¼ 2 Hz); m/z 352 (Found: C,
68.20; H, 4.56. C20H16O6 requires C, 68.18; H, 4.51%).
Photoreaction of Phenanthrenequinone 2 with Aurones 5a–h
Generalprocedure: To a suspension of 0.2 g phenanthrenequinone 2 in
toluene (200 ml) contained in a Pyrex photoreactor (>313 nm), 0.35 g of
aurone 5a was added. The mixture was exposed to UV light (HPK 125 W
lamp). TLC followed the course of the reaction until the reaction mixture
indicated substantial reaction of starting material (48 h). The solvent was
evaporated and the product was separated using a column prepared
by packing slurry of silica gel (30 g) is toluene. The column was eluated
with toluene/ethyl acetate (1: 1 v/v) whereby the photoaddition product
6a was separated. In a similar manner, the photochemical reactions of
phenanthrenequinone 2 with aurone 5b–h were carried out whereby com-
pounds 6b–h were likewise separated. 6a: m.p. 380ꢁC; brown crystals; 20%
yield; nmax (cmÀ1) (KBr) 3400 (OH); m/z 564.5; (Found: C, 70.15; H, 3.72.
C33H21O7Cl requires C, 70.15; H, 3.72%). 6b: m.p. 285ꢁC; orange crystals;
60% yield; nmax (cmÀ1) (KBr) 3420 (OH); m/z 575; (Found: C, 68.86; H,
3.65. C33H21O9 requires C, 68.86; H, 3.65%). 6c: m.p. 294ꢁC; brown
crystals; 15% yield; nmax (cmÀ1) (KBr) 3400 (OH); dH (CF3COOD), 3.99
(s, 3H, OCH3), 4.00 (s, 3H, OCH3), 4.02 (s, 3H, OCH3), 4.08–4.12 (4H, two
methylene protons and two bridgehead methine protons in a complex pat-
tern), 7.25 and 8.10 [(2d, 4H; AB system, J ¼ 6 Hz) aromatic protons 1,4-
disubstituted benzene ring], 7.75 and 7.85 (2d, 4H), 7.53 and 7.70 (2t, 4H,
phenanthrene protons); m/z 559 (Found: C, 72.98; H, 4.11. C34H23O8
requires C, 72.98; H, 4.11%). 6d: m.p. 275ꢁC; brown crystals; 20% yield;
n
max (cmÀ1) (KBr) 3420 (OH); m/z 590 (Found: C, 71.20; H, 4.42. C35H26O9

PHENANTHRENEQUINONE AND AURONES
1301
requires C, 71.18; H, 4.40%). 6e: m.p. 370ꢁC; brown crystals; 20% yield;
nmax (cmÀ1) (KBr) 3400 (OH); m/z 534.5; (Found: C, 71.88; H, 3.59.
C32H19O6Cl requires C, 71.84; H, 3.55%). 6f: m.p. 380ꢁC; orange crystals;
65% yield; nmax (cmÀ1) (KBr) 3400 (OH); dH (CF3COOD) 4.03 (s, 2H,
methylene proton), 4.37 (s, 3H, OCH3), 4.61(2d, bridgehead methine pro-
tons overlapped in a complex pattern), 7.25 and 8.12 (2d, 4H; AB system,
J ¼ 6 Hz) aromatic protons 1,4-disubstituted benzene ring), 7.55 (s, 1H,
visnagin proton), 7.50 and 7.63 (2t, 4H; 7.75 and 7.68 (2d, 4H, phenenthrene
protons); 13C NMR: 58.9 (OCH3), 98.0 (CH2), [123.5, 127.0, 130.1, 130.9,
132.8, 134.2] (12C phenanthrenequinone), [130.9, 131.2] (2C-H), [99.7,
102.5, 103.2, 158.0, 158.5, 158.5] (6C visnagin-phenyl ring), [123.5, 123.5,
127.8, 127.8, 145.6, 147.7] (6C visnagin 1,4-disubstituted phenyl ring), 145.6
(2C-O phenanthrenequinone), 165.4 (O-CCH2), 165.1 (C-OH); m/z 545
(Found: C, 70.45; H, 3.48. C32H19O8 require C, 70.45; H, 3.48%). 6g:
m.p. 385ꢁC; brown crystals; 15% yield; nmax (cmÀ1) (KBr) 3400 (OH); dH
(CF3COOD) 3.94 (s, 3H, OCH3), 3.98 (s, 3H, OCH3), 3.95 (s, 2H, methylene
proton), 4.04 and 4.6 (2d, bridgehead methine protons), 7.26 (s, 1H, visna-
gin proton), 7.25 and 8.15 [(2d, 4H; AB system, J ¼ 6 Hz) aromatic protons
1,4-disubstituted benzene ring], 7.67 and 7.5 (2t, 4H), 7.7 and 7.95 (2d, 4H,
phenanthrene protons); 13C NMR: 57.6 (OCH3), [129.9, 130.2, 132.7, 132.9,
132.3, 136.0] (12C phenanthrenquinone), [132.7, 132.9] (2C-H), [107.6,
107.6, 158.7, 158.7] (visnagin-phenyl ring), [111.3, 129.8, 136.0] (visnagin
1,4-disubstituted phenyl ring), 145.7 (2C-O phenanthrenequinone), 160.0
(O-CCH2), 160.3 (C-OH); m/z 530 (Found: C, 74.71; H, 4.15. C33H22O7
requires C, 74.71; H, 4.15%). 6h: m.p. 370ꢁC; brown crystals; 22% yield;
n
requires C, 72.85; H, 4.28%).
max (cmÀ1) (KBr) 3410 (OH); m/z 560 (Found: C, 72.85; H, 4.28. C34H24O8
There was a minor variation in the yield percentage of 6 due to the ring
substitution in 5 (15–22% yield). However, a major variation was observed
in both 6b and 6f (’60% yield).
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Received in Japan December 4, 2000