Synthesis of (S)-(+)-decursin and its analogues as potent inhibitors of melanin formation in B16 murine melanoma cells

Article abstract of DOI:10.1016/j.ejmech.2010.09.006

We report the synthesis of a novel series of highly potent melanin inhibitors which were obtained through structural modification of an anticancer compound S-(+)-decursinol. The in vitro inhibitory potencies of the newly synthesized compounds were evaluated against α-MSH induced melanin production in B16 murine melanoma cells. Among the compounds evaluated, compounds 2, 3, 6b, 7a, 7b, 8a and 8b emerged as highly potent inhibitors of melanin production. Besides, these compounds demonstrated significantly low cytotoxicity.

Full text of DOI:10.1016/j.ejmech.2010.09.006

European Journal of Medicinal Chemistry 45 (2010) 5567e5575
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis of (S)-(þ)-decursin and its analogues as potent inhibitors of melanin
formation in B16 murine melanoma cells
,
,
Kyeong Lee a 1, Jee-Hyun Lee b 1, Shanthaveerappa K. Boovanahalli a, Yongseok Choi c, Soo-Jin Choo d,
Ick-dong Yoo d, Dong Hee Kim e, Mi Young Yun f, Gye Won Lee g, Gyu-Yong Song b
,
*
a College of Life Science and Biotechnology, Dongguk University-Seoul, Seoul 100-756, Korea
b College of Pharmacy, Chungnam University, Daejeon 305-764, Korea
c College of Life Science and Biotechnology, Korea University, Seoul 136-713, Korea
d Korea Research Institute of Bioscience and Biotechnology, Daejeon 706-000, Korea
e College of Oriental Medicine, Daejeon University, Daejeon 305-806, Korea
f Department of Health Welfare, Byuksung College, Gimje 576-711, Korea
g Department of Pharmaceutical Engineering, Konyang University, Gimje 320-711, Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
We report the synthesis of a novel series of highly potent melanin inhibitors which were obtained
Received 29 June 2010
Received in revised form
1 September 2010
Accepted 2 September 2010
Available online 17 September 2010
through structural modification of an anticancer compound S-(þ)-decursinol. The in vitro inhibitory
potencies of the newly synthesized compounds were evaluated against
a-MSH induced melanin
production in B16 murine melanoma cells. Among the compounds evaluated, compounds 2, 3, 6b, 7a, 7b,
8a and 8b emerged as highly potent inhibitors of melanin production. Besides, these compounds
demonstrated significantly low cytotoxicity.
Ó 2010 Elsevier Masson SAS. All rights reserved.
Keywords:
(þ)-Decursinol
(þ)-Decursin
(þ)-Decursinol angelate
Melanin inhibitors
1. Introduction
of cosmetic whitening agents. In this context, several inhibitors of
melanin production have been reported in the literature [7e17].
Melanin is a heterogeneous biopolymer that is synthesized by
specialized cells known as melanocytes, dendritic cells that
comprise a relatively minor portion of the cells present in the
dermaleepidermal border of the skin. Melanin plays a vital role in
protecting human skin from the harmful effects of sunlight, toxic
drugs, and chemicals. However, increased levels of melanin
synthesis can cause diverse hyperpigmentary disorders such as
melasma, freckles, age spots or liver spots, and actinic damage,
resulting in the accumulation of excessive levels of epidermal and
dermal pigmentation [1e6]. Consequently, inhibition of abnormal
deposition of melanin is expected to provide therapeutic means for
the treatment of dermatological disorders and in the development
Angelica gigasNakai has been traditionally known as a medicinal
plant in East Asia. Recently, Park et al. reported the significant
inhibition of isobutylmethylxanthine-induced melanogenesis by
ethanolic extract of A.gigas in B16 melanoma cells [18]. (þ)-Decur-
sinol (1), (þ)-decursin (2) and (þ)-decursinol angelate (3) are novel
cancer chemotherapeutic candidates isolated fromA.gigasNakai and
were shown to display diverse range of interesting biological
properties. In view of their remarkable biological activities, decur-
sin and decursinol angelate have recently attracted considerable
attention of global researchers (Fig. 1) [19e25]. Based on these
findings, we hypothesized that decursin and their analogues may
elicit potent inhibition of melanin production. Moreover, to the best
of our knowledge, there have been no reports on the structure
activity relationship (SAR) studies of decursin analogues as melanin
inhibitors. These key findings prompted us to investigate a series of
decursin analogues for their potential to inhibit melanin produc-
tion in B16 melanoma cells. Herein, we report discovery of a novel
series of decursinol analogues as potent melanin inhibitors iden-
tified by preliminary SAR studies of 1.
* Corresponding author. Tel.: þ82 42 8215926; fax: þ82 42 8236566.
E-mail address: gysong@cnu.ac.kr (G.-Y. Song).
1
These authors equally contributed to this work.
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.09.006

5568
K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
O
O
O
O
O
O
O
O
O
O
O
O
b
a
HO
O
H3CO
HO
O
OH
O
11
10
9
1
: (+)-Decursinol
2
: (+)-Decursin
3
: (+)-Decursinol angelate
O
O
O
Fig. 1. Structure of (þ)-decursinol, (þ)-decursin and (þ)-decursinol angelate.
c
d
Br
O
12
2. Chemistry
13
The synthesis of (þ)-decursin, (þ)-decursinol angelate and their
analogues 4e8 and 13 was accomplished according to the synthetic
protocols as outlined in Schemes 1 and 2. The key starting material
1 was efficiently obtained from A.gigas by following our previously
developed method [26]. As shown in Scheme 1, DCC mediated
coupling of 1 with appropriate acids in presence of DMAP in
dichloromethane afforded compounds 2e4 and 6e8 in excellent
yields. Compounds 5aec were prepared in good yield by reacting 1
with appropriate acid chlorides in presence of catalytic amount of
pyridine in dichloromethane. Demethylation of compounds 7b, 7e,
7h, 7k and 7n was accomplished using BBr3 to obtain compounds
7c, 7f, 7i, 7l and 7o, respectively in good yield, which underwent
further acetylation by reaction with acetyl chloride to provide
corresponding acetylated compounds 7d, 7g, 7j, 7m and 7p,
respectively. Scheme 2 describes the synthesis of compound 13.
Cinnamic acid 9 underwent esterification, followed by DIBALH
mediated reduction to produce 11, which upon subsequent
bromination furnished 12. Reaction of 12 with 1 at e30 ꢀC in DMF in
presence of NaH afforded 13 in good yield.
Scheme 2. Reagents and conditions: (a) Concentrated H2SO4, MeOH, Reflux, 12 h; (b)
DIBALH in toluene 1 M solution, Dichloromethane, e78 ꢀC to rt, MeOH, Rochelle’s salt,
6 h; (c) PBr3, Diethyl ether, e3 ꢀC, 4 h; (d) (þ)-Decursinol, NaH, DMF anhydrous,
e20 ꢀC, 3 h.
inhibition of melanin production (Table 1). Arbutin [27], p-hydroxy-
phenyl b-D-glucopyranoside, a well-known skin-whitening agent
was used as a reference compound for a comparison, which showed
moderate inhibition (41%) without cytotoxicity.
In order to define the key structural requirements for melanin
inhibitory activity, our structure activity relationship studies
centered on the derivatisation of hydroxyl group present at 7-posi-
tion of (þ)-decursinol (1), to its corresponding ester and ether
derivatives. Accordingly, we first investigated the effect of the
natural products (þ)-decursinol (1) having free hydroxyl group,
(þ)-decursin (2) and (þ)-decursinol angelate (3) with ester groups.
Interestingly, esters 2 and 3 demonstrated significant inhibition of
melanin formation (71% and 74.5%, respectively) without exhibiting
cytotoxicity. On the other hand, compound 1 without any side chain
on ether linkage demonstrated poor inhibitory activity, suggesting
that alkyl-ester linkage is optimal for potency. Encouraged by these
results, we prepared various alkenyl substituted carboxylic acid
derivatives 4aee. Although compounds 4a and 4c exhibited appre-
ciably high inhibitory activity (71.5% and 79.4%, respectively), dis-
played cytotoxicity as well (16.4% and 39.5%, respectively).
Compound 4b exhibited moderate inhibition (58%) and compounds
4dee were found to be inactive. Replacement of alkenoyl groups by
alkanoyl substitutions was investigated by synthesizing analogues
5aec. Of the three compounds, 5b and 5c are the most potent
melanin inhibitors with 76.5% and 79.3% inhibition, respectively,
3. Results and discussion
The newly synthesized compounds were evaluated for their
potential to inhibit melanin formation in B16 murine melanoma
cells and the results are tabulated in Table 1. All the assays were
performed under standard assay conditions by following the
previously described assay protocol. Cell viability, as measured by
the MTT assay, showed that most of the compounds had no
significant cytotoxicity at their effective concentrations for the
O
O
O
R
O
O
8a: R = H
8b: R = OCH3
g
O
O
O
O
O
O
O
O
O
O
O
d
a
O
O
R
OH
R
2: R = -CH=C(CH3)2
1: (+)-decursinol
3: R = -cis-C(CH3)=CHCH3
7a: R = -H
4a: R = -trans-C(CH3)=CHCH3
4b: R = -C(CH3)=CH2
4c: R = -CH=CHCH2CH3
4d: R = -CH2CH=CH2
4e: R = -CH2CH2CH=CH2
O
7b: R = -2-OCH3
7c: R = -2-OH
7d: R = -2-OAc
7e: R = -3-OCH3
7f: R = -3-OH
7g: R = -3-OAc
7h: R = -4-OCH3
7i: R = -4-OH
7j: R = -4-OAc
e
b
c
f
e
e
e
e
O
O
f
O
O
O
O
O
O
R
O
R
f
5a: R = -CH3
6a: R = -3-pyridyl
6b: R = -2-thienyl
6c: R = -2-furanyl
5b: R = -(CH2)3CH3
5c: R = -(CH2)8CH3
7k: R = -3,4-(OCH3)2
7l: R = -3,4-(OH)2
f
7m: R = -3,4-(OAc)2
7n: R = -3,4,5-(OCH3)3
7o: R = -3,4,5-(OH)3
7p: R = -3,4,5-(OAc)3
f
Scheme 1. Reagents and conditions: (a) Alkenyl substituted carboxylic acid, DCC, 4-DMAP, Dichloromethane, 5e12 h, rt; (b) Alkanoyl chloride, Pyridine, Dichloromethane, rt,
6e12 h; (c) 3-Aryl-Acrylic acid, DCC, 4-DMAP, Dichloromethane, rt, 5e12 h; (d) Substituted Cinnamic acid, DCC, 4-DMAP, Dichloromethane, rt 6e12 h; or Substituted Cinnamic acid,
SOCl2, DMF (catalytic), Benzene, Reflux, 5e12 h, then Pyridine, Dichloromethane, rt, 6e12 h; (e) BBr3, Dichloromethane, 0 ꢀC, 5 h; (f) Acetyl chloride, Pyridine, Dichloromethane, rt,
8 h; (g) Phenyl- or 2-Methoxy-phenyl- propionic acid, DCC, 4-DMAP, Dichloromethane, 5e12 h, rt.

K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
5569
Table 1
melanin in B16 murine melanoma cells and assessed for their cyto-
toxicity. Preliminary SAR studies involving structural modification of
(þ)-decursinol led to the identification of highly potent melanin
inhibitors having no cytotoxicity represented bycompounds 2, 3, 6b,
7a, 7b, 8a and 8b, which demonstrated appreciably high inhibitory
activity than that of reference compound arbutin. These compounds
could serve as valuable leads for the treatment of dermatological
disorders and in the development of cosmetic whitening agents.
Melanin inhibitory activity and cytotoxicity of compounds 1e8 and 13 in B16F10
murine melanoma cells.a
O
O
O
R
O
Compounds
R
% Inhibition at Cytotoxicity
100 (%)
m
M
1
2
3
H
12.2 ꢂ 6.9
71.0 ꢂ 12.0
74.5 ꢂ 2.7
71.5 ꢂ 10.2
58.1 ꢂ 10.6
79.4 ꢂ 2.8
ꢃ8.1 ꢂ 4.3
36.4 ꢂ 8.0
ꢃ5.7 ꢂ 8.0
76.5 ꢂ 4.4
79.3 ꢂ 3.5
53.5 ꢂ 14.2
71.6 ꢂ 9.8
33.0 ꢂ 1.9
72.1 ꢂ 1.6
63.7 ꢂ 1.6
76.8 ꢂ 1.5
65.9 ꢂ 9.1
37.9 ꢂ 9.4
73.8 ꢂ 10.2
80.7 ꢂ 3.6
40.3 ꢂ 7.4
66.4 ꢂ 11.2
76.1 ꢂ 9.1
42.4 ꢂ 7.4
43.5 ꢂ 0.5
30.7 ꢂ 11.5
1.4 ꢂ 14.4
5. Experimental
eCOCH]C(CH3)2
ꢃ9.7 ꢂ 11.5
ꢃ2.4 ꢂ 10.6
16.4 ꢂ 0.9
58.4 ꢂ 0.5
39.5 ꢂ 0.6
0.6 ꢂ 3.5
eCOciseC(CH3)]CHCH3
eCOtranseC(CH3)]CHCH3
eCOC(CH3)]CH2
eCOCH]CHCH2CH3
eCOCH2CH]CH2
eCOCH2CH2CH]CH2
eCOCH3
eCO(CH2)3CH3
5.1. Chemistry
4a
4b
4c
4d
4e
5a
5b
5c
6a
6b
6c
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
8a
8b
13
The reactions were monitored by TLC on silica gel GF254.
Detection was effected by examination under UV light. Silica gel
Column chromatography was performed on silica gel (250e400
mesh, Silicycle). 1H and 13C NMR spectra were performed on a JEOL
JNM-AL 400 spectrometer. Melting points were recorded on
a Yamako MD-S3. Low resolution mass spectra were acquired using
a PE SCIX API 2000 MS/MS. Optical rotations were measured in
a 1.0 dm tube with JASCO DIP-370 polarimeter in CHCl3 and MeOH.
Elemental analyses were performed on a Thermo Fisher Scientific
(Flash EA 1112 series).
ꢃ0.4 ꢂ 2.7
3.7 ꢂ 5.1
10.4 ꢂ 1.3
28.2 ꢂ 1.8
5.0 ꢂ 13.0
ꢃ15.4 ꢂ 1.8
ꢃ1.4 ꢂ 7.0
0.8 ꢂ 11.9
ꢃ5.1 ꢂ 11.0
74.2 ꢂ 10.6
63.1 ꢂ 6.9
14.5 ꢂ 2.2
47.9 ꢂ 11.8
31.4 ꢂ 10.7
ꢃ3.5 ꢂ 11.1
65.8 ꢂ 7.2
58.0 ꢂ 1.6
ꢃ1.4 ꢂ 7.1
67.6 ꢂ 3.9
49.4 ꢂ 2.0
4.1 ꢂ 9.8
eCO(CH2)8CH3
eCOCH]CH-3-Pyridyl
eCOCH]CH-2-Thienyl
eCOCH]CH-2-Furanyl
eCOCH]CHePhenyl
eCOCH]CHeC6H4eOCH3-2
eCOCH]CHeC6H4eOH-2
eCOCH]CHeC6H4eOAc-2
eCOCH]CHeC6H4eOCH3-3
eCOCH]CHeC6H4eOH-3
eCOCH]CHeC6H4eOAc-3
eCOCH]CHeC6H4eOCH-4
eCOCH]CHeC6H4eOH-4
eCOCH]CHeC6H4eOAc-4
5.2. (þ)-Decursinol (1) [26]
White solid, mp: 177.6 ꢀC, Rf ¼ 0.20 (2:1 n-hexaneeethyl
acetate); ½a 2D5
ꢁ
þ12.3 (c ¼ 3, CHCl3); 1H NMR (400 MHz, CDCl3): dH
eCOCH]CHeC6H3e(OCH3)2-3,4
eCOCH]CHeC6H3e(OH)2-3,4
eCOCH]CHeC6H3e(OAc)2-3,4
7.57 (1H, d, J ¼ 9.6 Hz, H-4), 7.17 (1H, s, H-5), 6.77 (1H, s, H-10), 6.21
(1H, d, J ¼ 9.6 Hz, H-3), 3.87 (1H, q, J ¼ 5.6 Hz, H-7), 3.11 (1H, dd,
J ¼ 5.6, 17.2 Hz, H-6a), 2.83 (1H, dd, J ¼ 5.6, 17.2 Hz, H-6b), 1.93 (1H,
d, J ¼ 6.8 Hz, OH-7), 1.39 (3H, s, CH3-8), 1.36 (3H, s, CH3-8); 13C NMR
(100 MHz, acetone-d6) dC; 160.9(C-2), 157.6(C-9a), 154.9(C-10a),
144.3(C-4), 130.0(C-5), 118.6(C-5a), 113.3(C-3), 113.3(C-4a), 104.2
(C-10), 79.2(C-8), 69.1(C-7), 31.3(C-6), 25.9(CH3-8), 21.2(CH3-8);
ESI-MS: m/z ¼ 247 [M þ H]þ. Anal. Calc. for C14H14O4: C, 68.28; H,
5.73; Found: C, 68.22; H, 5.71.
eCOCH]CHeC6H2e(OCH3)3-3,4,5 18.8 ꢂ 8.7
eCOCH]CHeC6H2e(OH)3-3,4,5
59.2 ꢂ 5.9
42.9 ꢂ 3.1
54.8 ꢂ 7.2
ꢃ0.6 ꢂ 0.6
6.1 ꢂ 10.4
ꢃ12.53 ꢂ 7.8
ꢃ6.2 ꢂ 2.4
eCOCH]CHeC6H2e(OAc)3-3,4,5 35.4 ꢂ 2.6
eCOCH2CH2ePhenyl
62.8 ꢂ 1.7
68.9 ꢂ 0.5
33.8 ꢂ 1.9
41.0 ꢂ 4.0
eCOCH2CH2eC6H4eOCH3-2
eCH2CH]CH-Phenyl
Arbutin (evaluated at 500 mM)
a
Values are means of three experiments.
however showed moderate cytotoxicity (10.4% and 28.2%, respec-
tively). We then explored the effect of various acrylic acid derivatives
represented by analogues 6aec and 7aep. Interestingly, this modi-
fication yielded highly potent melanin inhibitors 6b, 7a and 7b,
which displayed highly potent melanin inhibitory activity without
cytotoxicity (71.6%, 72.1% and 63.7%, respectively). On the other
hand, compounds 7c, 7d, 7f, 7g, 7i, and 7j which potently sup-
pressed the melanin formation, were also found to be cytotoxic and
all of other derivatives exhibited poor inhibitory activity. Based on
these results, we prepared further modified analogues 8aeb and 13.
Compounds with saturated carboxylic acids 8a and 8b possessing
significantly low cytotoxicity greatly inhibited the production of
melanin with 62.8% and 68.9% inhibition, respectively. However,
compound 13 having ether linkage showed poor inhibitory activity,
in addition did not show any cytotoxicity. These results strongly
suggested that the hydroxyl group or replacement of hydroxyl group
with an ether moiety caused significant loss of activity, and that the
presence of ester substitution is essential for effective inhibition of
melanin formation.
5.3. General method for the synthesis of compounds (2e3, 4aee)
The mixture of alkenyl substituted carboxylic acid (4.06 mmol),
DCC (8.12 mmol) and 4-DMAP (1.62 mmol) were dissolved in
anhydrous dichloromethane. (S)-(þ)-Decursinol (1, 4.06 mmol)
was added thereto to react together with stirring to room
temperature for 5e12 h. The mixture was washed with dichloro-
methane, filtrated and concentrated in vacuo. The residue was
purified by flash silica gel column chromatography.
5.3.1. (S)-(þ)-Decursin (2)
Yield 64.0%, white solid, mp: 93e94 ꢀC, Rf ¼ 0.35 (2:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ132.7 (c ¼ 3, CHCl3); 1H NMR (400 MHz,
CDCl3): dH 7.58(1H, d, J ¼ 9.6 Hz, H-4), 7.16(1H, s, H-5), 6.78(1H, s,
H-10), 6.22(1H, d, J ¼ 9.6 Hz, H-3), 5.66(1H, s, H-20), 5.08(1H, t,
J ¼ 4.8 Hz, H-7), 3.19(1H, dd, J ¼ 4.8, 17.2 Hz, H-6a), 2.86(1H, dd,
J ¼ 4.8, 17.2 Hz, H-6b), 2.14(3H, d, J ¼ 1.0 Hz, CH3-30), 1.88(3H, d,
J ¼ 1.0 Hz, 3H-40), 1.38(3H, s, CH3-8), 1.36(3H, s, CH3-8); 13C NMR
(100 MHz, CDCl3) dC 165.7(C-10), 161.2(C-2), 158.4(C-30), 156.4
(C-9a), 154.1(C-10a), 143.1(C-4), 128.6(C-5), 115.9(C-5a), 115.5(C-20),
113.2(C-3), 112.8(C-4a), 104.7(C-10), 76.6(C-8), 69.1(C-7), 27.9(C-6),
27.4(C-40), 25.0(CH3-8), 23.1(CH3-8), 20.3(CH3-30); ESI-MS: m/
z ¼ 329 [M þ H]þ. Anal. Calc. for C19H20O5: C, 69.50; H, 6.14. Found:
C, 69.23; H, 6.12.
4. Conclusions
In summary, a novel series of (þ)-decursinol analogues were
prepared and evaluated for their ability to inhibit the production of

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K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
5.3.2. (S)-(þ)-Decursinol angelate (3)
(400 MHz, CDCl3): dH 7.58(1H, d, J ¼ 9.6 Hz, H-4), 7.15(1H, s, H-5),
6.79(1H, s, H-10), 6.23(1H, d, J ¼ 9.6 Hz, H-3), 5.86(1H, m, H-30),
5.17(2H, m, H-4a0, H-4b0), 5.06(1H, t, J ¼ 4.8 Hz, H-7), 3.19(1H, dd,
J ¼ 4.8, 17.2 Hz, H-6a), 3.09(2H, m, 2H-20), 2.85(1H, dd, J ¼ 5.2,
17.2 Hz, H-6b), 1.37(3H, s, CH3-8), 1.35(3H, s, CH3-8); 13C NMR
(100 MHz, CDCl3) dC 170.8(C-10), 161.1(C-2), 156.2(C-9a), 154.1(C-
10a), 143.0(C-4), 129.6(C-30), 128.5(C-5), 119.0(C-40), 115.5(C-5a),
113.3(C-3), 112.8(C-4a), 104.7(C-10), 76.6(C-8), 70.4(C-7), 39.0(C-
Yield 56.3%, white solid, mp: 93e94 ꢀC, Rf ¼ 0.35 (2:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ93.0 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3) dH 7.57(1H, d, J ¼ 9.6 Hz, H-4), 7.15(1H, s, H-5), 6.79(1H, s,
H-10), 6.23(1H, d, J ¼ 9.2 Hz, H-3), 6.10(1H, q, J ¼ 7.6 Hz, H-30), 5.12
(1H, t, J ¼ 4.4 Hz, H-7), 3.22(1H, dd, J ¼ 4.8, 17.2 Hz, H-6a), 2.89(1H,
dd, J ¼ 4.8, 17.2 Hz, H-6b), 1.88(3H, d, J ¼ 6.8 Hz, 3H-40), 1.83(3H, s,
CH3-20), 1.39(3H, s, CH3-8), 1.38(3H, s, CH3-8); 13C NMR (100 MHz,
CDCl3) dC 167.1(C-10), 161.2(C-2), 156.4(C-9a), 154.1(C-10a), 143.1
(C-4), 139.5(C-30), 128.6(C-5), 127.3(C-20), 115.8(C-5a), 113.2(C-3),
112.8(C-4a), 104.6(C-10), 77.1(C-8), 70.0(C-7), 27.9(C-6), 25.0
(CH3-8), 23.1(CH3-8), 20.5(CH3-20), 15.7(C-40); ESI-MS: m/z ¼ 329
[M þ H]þ. Anal. Calc. for C19H20O5: C, 69.50; H, 6.14. Found: C, 69.47;
H, 6.11.
20), 27.7(C-6), 24.9(CH3-8), 22.9(CH3-8); ESI-MS: m/z
¼
315
[M þ H]þ. Anal. Calc. for C18H18O5: C, 68.78; H, 5.77. Found: C,
68.64; H, 5.76.
5.3.7. (7S)-(þ)-Pent-4-enoic acid acid 8,8-dimethyl-2-oxo-6,7-
dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (4e)
Yield 81.0%, light orange-yellow solid, mp: 94e95 ꢀC, Rf ¼ 0.51
5.3.3. (7S)-(þ)-trans-2-Methyl-but-2-enoic acid 8,8-dimethyl-2-
oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (4a)
Yield 43.9%, white solid, mp: 93e94 ꢀC, Rf ¼ 0.48 (2:1 n-hex-
(2:1 n-hexaneeethyl acetate); ½a D25
ꢁ
þ62.6 (c ¼ 3, CHCl3); 1H NMR
(400 MHz, CDCl3): dH 7.58(1H, d, J ¼ 9.6 Hz, H-4), 7.14(1H, s, H-5),
6.79(1H, s, H-10), 6.23(1H, d, J ¼ 9.6 Hz, H-3), 5.79e5.71(1H, m,
H-40), 5.05e4.95(3H, m, H-7, H-5a0, H-5b0), 3.17(1H, dd, J ¼ 4.8,
17.2 Hz, H-6a), 2.83 (1H, dd, J ¼ 5.2, 17.2 Hz, H-6b), 2.43(2H, m,
2H-30), 2.35(2H, t, J ¼ 6.4 Hz, 2H-20), 1.37(3H, s, CH3-8), 1.35(3H, s,
CH3-8); 13C NMR (100 MHz, CDCl3) dC 172.4(C-10), 161.2(C-2), 156.3
(C-9a),154.1(C-10a), 143.0(C-4), 136.2(C-40), 128.5(C-5),115.7(C-5a),
115.7(C-50), 113.3(C-3), 112.8(C-4a), 104.7(C-10), 76.4(C-8), 70.1
(C-7), 33.4(C-20), 28.7(C-30), 27.7(C-6), 24.9(CH3-8), 23.0(CH3-8);
ESI-MS: m/z ¼ 329 [M þ H]þ. Anal. Calc. for C19H20O5: C, 69.50; H,
6.14. Found: C, 69.47; H, 6.13.
aneeethyl acetate); ½a D25
ꢁ
þ68.9 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.59(1H, d, J ¼ 9.6 Hz, H-4), 7.16(1H, s, H-5), 6.81(2H, m,
H-10, H-30), 6.22(1H, d, J ¼ 9.6 Hz, H-3), 5.08(1H, t, J ¼ 4.8 Hz, H-7),
3.21(1H, dd, J ¼ 4.8, 17.2 Hz, H-6a), 2.89(1H, dd, J ¼ 4.8, 17.2 Hz,
H-6b),1.80(3H, s, CH3-20),1.76(3H, m, 3H-40), 1.35(3H, s, CH3-8),1.31
(3H, s, CH3-8); 13C NMR (100 MHz, CDCl3) dC 167.1(C-10), 121.2(C-2),
156.4(C-9a), 154.1(C-10a), 143.1(C-4), 138.3(C-30), 128.6(C-5), 128.1
(C-20), 115.8(C-5a), 113.2(C-3), 112.8(C-4a), 104.6(C-10), 76.6(C-8),
70.1(C-7), 27.7(C-6), 25.0(CH3-8), 23.0(CH3-8), 14.4(CH3-20), 11.9
(C-40); ESI-MS: m/z ¼ 329 [M þ H]þ. Anal. Calc. for C19H20O5: C,
69.50; H, 6.14. Found: C, 69.41; H, 6.11.
5.4. General method for the synthesis of compounds (5aec)
5.3.4. (7S)-(þ)-2-Methyl-acrylic acid 8,8-dimethyl-2-oxo-6,7-
dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (4b)
A solution of (S)-(þ)-decursinol (1, 0.406 mmol) in anhydrous
dichloromethane was added to pyridine (0.812 mmol) and alkanoyl
chloride (0.812 mmol). The mixture was stirred to room tempera-
ture for 6e12 h and the solvent was removed in vacuum. The
residue was purified by flash silica gel column chromatography.
Yield 93.3%, white solid, mp: 80e81 ꢀC, Rf ¼ 0.52 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ80.5 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.56(1H, d, J ¼ 9.6 Hz, H-4), 7.14(1H, s, H-5), 6.78(1H, s,
H-10), 6.21(1H, d, J ¼ 9.6 Hz, H-3), 6.05(1H, s, H-3a0), 5.56(1H, s,
H-3b0), 5.07(1H, t, J ¼ 5.2 Hz, H-7), 3.20(1H, dd, J ¼ 4.8, 16.8 Hz,
H-6a), 2.88(1H, dd, J ¼ 5.6, 17.2 Hz, H-6b), 1.90(3H, s, CH3-20), 1.38
(3H, s, CH3-8), 1.37(3H, s, CH3-8); 13C NMR (100 MHz, CDCl3) dC
166.5(C-10), 161.2(C-2), 156.3(C-9a), 154.1(C-10a), 143.0(C-4), 135.8
(C-30), 128.6(C-5), 126.4(C-20), 115.7(C-5a), 113.3(C-3), 112.8(C-4a),
104.6(C-10), 76.6(C-8), 70.5(C-7), 27.7(C-6), 25.0(CH3-8), 22.9
(CH3-8), 18.1(CH3-20); ESI-MS: m/z ¼ 315 [M þ H]þ. Anal. Calc. for
C18H18O5: C, 68.78; H, 5.77. Found: C, 68.59; H, 5.75.
5.4.1. (7S)-(þ)-Acetic acid acid 8,8-dimethyl-2-oxo-6,7-dihydro-
2H,8H-pyrano[3,2-g]chromen-7-yl-ester (5a)
Yield 89.8%, white solid, mp: 125e126 ꢀC, Rf ¼ 0.38 (1:1 n-
hexaneeethyl acetate); ½a D25
ꢁ
þ61.7 (c ¼ 3, CHCl3); 1H NMR
(400 MHz, CDCl3): dH 7.57(1H, d, J ¼ 9.6 Hz, H-4), 7.15(1H, s, H-5),
6.79(1H, s, H-10), 6.22(1H, d, J ¼ 9.6 Hz, H-3), 5.05(1H, t, J ¼ 4.8 Hz,
H-7), 3.18(1H, dd, J ¼ 4.0,17.2 Hz, H-6a), 3.00(1H, dd, J ¼ 4.8,17.4 Hz,
H-6b), 2.04(3H, s, 3H-20), 1.42(3H, s, CH3-8), 1.37(3H, s, CH3-8); 13C
NMR (100 MHz, CDCl3) dC 170.4(C-10), 161.2(C-2), 156.2(C-9a), 154.1
(C-10a), 143.1(C-4), 128.6(C-5), 115.5(C-5a), 113.3(C-3), 112.8(C-4a),
104.7(C-10), 76.4(C-8), 70.1(C-7), 27.7(C-6), 24.8(CH3-8), 23.1
(CH3-8), 21.0(C-20); ESI-MS: m/z ¼ 289 [M þ H]þ. Anal. Calc. for
C16H16O5: C, 66.66; H, 5.59. Found: C, 66.52; H, 5.58.
5.3.5. (7S)-(þ)-Pen-2-enoic acid 8,8-dimethyl-2-oxo-6,7-dihydro-
2H,8H-pyrano[3,2-g]chromen-7-yl-ester (4c)
Yield 92.1%, light yellow solid, mp: 58e59 ꢀC, Rf ¼ 0.40 (2:1
n-hexaneeethyl acetate); ½a D25
ꢁ
þ91.3 (c ¼ 3, CHCl3); 1H NMR
(400 MHz, CDCl3): dH 7.58(1H, d, J ¼ 9.6 Hz, H-4), 7.15(1H, s, H-5),
7.02(1H, m, H-30), 6.79(1H, s, H-10), 6.22(1H, d, J ¼ 9.6 Hz, H-3), 5.80
(1H, d, J ¼ 15.6 Hz, H-20), 5.11(1H, t, J ¼ 4.8 Hz, H-7), 3.20(1H, dd,
J ¼ 4.8, 17.2 Hz, H-6a), 2.88 (1H, dd, J ¼ 4.8, 17.2 Hz, H-6b), 2.19(2H,
m, 2H-40), 1.39(3H, s, CH3-8), 1.36(3H, s, CH3-8), 1.04(3H, t,
J ¼ 7.6 Hz, 3H-50); 13C NMR (100 MHz, CDCl3) dC 165.9(C-10), 161.2
(C-2), 156.3(C-9a), 154.1(C-10a), 152.1(C-30), 143.1(C-4), 128.6(C-5),
119.6(C-20), 115.7(C-5a), 113.2(C-3), 112.8(C-4a), 104.6(C-10), 76.6
(C-8), 69.8(C-7), 27.7(C-6), 25.2(C-40), 24.9(CH3-8), 23.1(CH3-8), 11.9
(C-50); ESI-MS: m/z ¼ 329 [M þ H]þ. Anal. Calc. for C19H20O5: C,
69.50; H, 6.14. Found: C, 69.43; H, 6.11.
5.4.2. (7S)-(þ)-Pentanoic acid acid 8,8-dimethyl-2-oxo-6,7-
dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (5b)
Yield 90.7%, light yellow solid, mp: 55e56 ꢀC, Rf ¼ 0.39 (2:1
n-hexaneeethyl acetate); ½a D25
ꢁ
þ79.0 (c ¼ 3, CHCl3); 1H NMR
(400 MHz, CDCl3): dH 7.57(1H, d, J ¼ 9.6 Hz, H-4), 7.14(1H, s, H-5),
6.78(1H, s, H-10), 6.22(1H, d, J ¼ 9.6 Hz, H-3), 5.04(1H, t, J ¼ 5.2 Hz,
H-7), 3.18(1H, dd, J ¼ 4.8, 16.8 Hz, H-6a), 2.83(1H, dd, J ¼ 4.8,
16.8 Hz, H-6b), 2.31(2H, t, J ¼ 7.6 Hz, 2H-20), 1.58(2H, m, 2H-30), 1.37
(3H, s, CH3-8), 1.35(3H, s, CH3-8), 1.37e1.25(2H, m, 2H-40), 0.87(3H,
t, J ¼ 7.2 Hz, 3H-50); 13C NMR (100 MHz, CDCl3) dC 173.2(C-10), 161.2
(C-2), 156.3(C-9a), 154.1(C-10a), 143.1(C-4), 128.5(C-5), 115.6(C-5a),
113.3(C-3),112.8(C-4a),104.7(C-10), 76.5(C-8), 69.9(C-7), 34.0(C-20).
27.7(C-6), 26.9(C-30), 24.9(CH3-8), 23.0(CH3-8), 22.1(C-40), 13.6
(C-50); ESI-MS: m/z ¼ 331 [M þ H]þ. Anal. Calc. for C19H22O5: C,
69.07; H, 6.71. Found: C, 68.93; H, 6.68.
5.3.6. (7S)-(þ)-But-3-enoic acid acid 8,8-dimethyl-2-oxo-6,7-
dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (4d)
Yield 90.2%, white solid, mp: 78e79 ꢀC, Rf ¼ 0.65 (1:1
n-hexaneeethyl acetate); ½a D25
ꢁ
þ71.0 (c ¼ 3, CHCl3); 1H NMR

K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
5571
5.4.3. (7S)-(þ)-Decanoic acid acid 8,8-dimethyl-2-oxo-
6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (5c)
5.5.3. (7S)-(þ)-3-(2-Furanyl)-acrylic acid acid 8,8-dimethyl-2-oxo-
6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (6c)
Yield 93.0%; yellow Oil; Rf
¼
0.49 (2:1 n-hexaneeethyl
Yield 73.6%, light orange solid, mp: 96 ꢀC, Rf ¼ 0.62 (1:1
acetate); ½a 2D5
ꢁ
þ43.8 (c ¼ 3, CHCl3); 1H NMR(400 MHz, CDCl3): dH
n-hexaneeethyl acetate); ½a D25
ꢁ
þ62.4 (c ¼ 3, CHCl3); 1H NMR
7.57(1H, d, J ¼ 9.2 Hz, H-4), 7.14(1H, s, H-5), 6.78(1H, s, H-10),
6.22(1H, d, J ¼ 9.2 Hz, H-3), 5.04(1H, t, J ¼ 4.8 Hz, H-7), 3.17(1H,
dd, J ¼ 4.8, 16.8 Hz, H-6a), 2.83(1H, dd, J ¼ 4.8, 17.2 Hz, H-6b),
2.32(2H, t, J ¼ 8.0 Hz, 2H-20), 1.61(2H, m, 2H-30), 1.40(3H, s,
CH3-8), 1.37(3H, s, CH3-8), 1.33e1.22(12H, m, 2H-40, 2H-50, 2H-60,
2H-70, 2H-80, 2H-90), 0.88(3H, t, J ¼ 7.2 Hz, 3H-100); 13C NMR
(100 MHz, CDCl3) dC 173.2(C-10), 161.2(C-2), 156.3(C-9a), 154.1
(C-10a), 143.1(C-4), 128.5(C-5), 115.6(C-5a), 113.3(C-3), 112.8(C-4a),
104.7(C-10), 76.5(C-8), 69.9(C-7), 34.3(C-20), 31.8(C-30), 29.3(C-40),
29.2(C-50), 29.1(C-60), 29.0(C-70), 27.7(C-6), 24.9(CH3-8), 24.6
(C-80), 23.1(CH3-8), 22.6(C-90), 14.0(C-100); ESI-MS: m/z ¼ 401
[M þ H]þ. Anal. Calc. for C24H32O5: C, 71.97; H, 8.05. Found: C,
71.87; H, 8.03.
(400 MHz, CDCl3): dH 7.64(1H, s, H-60), 7.58(1H, d, J ¼ 9.6 Hz, H-
4), 7.56(1H, d, J ¼ 16.0 Hz, H-30), 7.41(1H, d, J ¼ 1.6 Hz, H-70),
7.17(1H, s, H-5), 6.82(1H, s, H-10), 6.55(1H, d, J ¼ 1.6 Hz, H-80),
6.23(1H, d, J ¼ 9.6 Hz, H-3), 6.13(1H, d, J ¼ 16.0 Hz, H-20), 5.17
(1H, t, J ¼ 4.4 Hz, H-7), 3.23(1H, dd, J ¼ 4.4, 17.6 Hz, H-6a), 2.92
(1H, dd, J ¼ 4.4, 17.6 Hz, H-6b), 1.42(3H, s, CH3-8), 1.38(3H, s,
CH3-8); 13C NMR (100 MHz, CDCl3) dC 166.3(C-10), 161.3(C-2),
156.3(C-9a), 154.1(C-10a), 144.8(C-40), 144.5(C-60), 143.1
(C-4), 135.8(C-30), 128.7(C-5), 117.0(C-20), 115.6(C-5a), 113.3(C-3),
112.9(C-70), 112.9(C-4a), 107.2(C-80), 104.7(C-10), 76.6(C-8), 70.0
(C-7), 27.8(C-6), 24.8(CH3-8), 23.3(CH3-8); ESI-MS: m/z ¼ 367
[M þ H]þ. Anal. Calc. for C21H18O6: C, 68.85; H, 4.95. Found: C,
68.82; H, 4.94.
5.5. General method for the synthesis of compounds (6aec)
5.6. General method for the synthesis of compounds (7aep)
The mixture of aryl-acrylic acid (0.812 mmol), DCC
(0.812 mmol) and 4-DMAP (0.162 mmol) were dissolved in anhy-
drous dichloromethane. (S)-(þ)-Decursinol (1, 0.406 mmol) was
added thereto to react together with stirring to room temperature
for 5e12 h. The mixture was washed with dichloromethane, fil-
trated and concentrated in vacuo. The residue was purified by flash
silica gel column chromatography.
Two drops of N,N-dimethyl formamide and thionyl chloride
(20.3 mmol) were added to a solution of cinnamic acid (6.09 mmol)
in 20 ml of anhydrous benzene. After refluxing for 5e12 h at
70e80 ꢀC, the reaction solution was cooled to room temperature
and concentrated under reduced pressure to obtain cinnamoyl
chloride. (S)-(þ)-Decursinol (1, 4.06 mmol) was added to a solution
of cinnamoyl chloride and pyridine (12.2 mmol) in anhydrous
dichloromethane at room temperature. After stirring for 2e5 h, the
reaction mixture was concentrated under reduced pressure. The
residue was purified by flash silica gel column chromatography to
obtain cinnamoyl- or methoxy-cinnamoyl decursin derivatives (7a,
7b, 7e, 7h, 7k and 7n).
5.5.1. (7S)-(þ)-3-(3-Pyridyl)-acrylic acid acid 8,8-dimethyl-2-oxo-
6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (6a)
Yield 96.7%, white solid, mp: 105 ꢀC, Rf ¼ 0.24 (1:1 n-hex-
aneeethyl acetate);
½
a 2D5
ꢁ
þ48.5 (c
¼
3, CHCl3); 1H NMR
(400 MHz, CDCl3): dH 8.72(1H, d, J ¼ 2.2 Hz, H-50), 8.60(1H, dd,
J ¼ 1.5, 4.9 Hz, H-70), 7.81(1H, d, J ¼ 8.4 Hz, H-90), 7.67(1H, d,
J ¼ 16.0 Hz, H-30), 7.58(1H, d, J ¼ 9.6 Hz, H-4), 7.32(1H, dd,
J ¼ 4.8, 8.0 Hz, H-80), 7.18(1H, s, H-5), 6.83(1H, s, H-10), 6.49(1H,
d, J ¼ 16.4 Hz, H-20), 6.24(1H, d, J ¼ 9.6 Hz, H-3), 5.21(1H, t,
J ¼ 4.8 Hz, H-7), 3.26(1H, dd, J ¼ 4.8, 17.2 Hz, H-6a), 2.95(1H, dd,
J ¼ 4.8, 17.2 Hz, H-6b), 1.44(3H, s, CH3-8), 1.39(3H, s, CH3-8); 13C
NMR (100 MHz, CDCl3) dC 165.6(C-10), 161.2(C-2), 156.3(C-9a),
154.2(C-10a), 151.2(C-50), 149.8(C-70), 143.1(C-4), 142.1(C-30), 134.2
(C-90), 129.8(C-40), 128.7(C-5), 123.7(C-80), 119.5(C-20), 115.5(C-5a),
113.4(C-3), 112.9(C-4a), 104.8(C-10), 76.5(C-8), 70.5(C-7), 27.8(C-
6), 24.9(CH3-8), 23.4(CH3-8); ESI-MS: m/z ¼ 378 [M þ H]þ. Anal.
Calc. for C22H19 NO5: C, 70.02; H, 5.07; N, 3.71. Found: C, 69.92;
H, 5.05; N, 3.70.
A
solution of methoxy-cinnamoyl decursin derivatives
(0.49 mmol) in anhydrous dichloromethane (5 ml) was added to
boron tribromide solution in dichloromethane
1
M
(1.47e2.46 mmol) in ice bath. The mixture was stirred to room
temperature for 5 h. The reaction solution was purified by silica gel
short-column chromatography and re-purified by C18 column
chromatography to obtain hydroxy-cinnamoyl decursin derivatives
(7c, 7f, 7i, 7l and 7o).
A
solution of hydroxy-cinnamoyl decursin derivatives
(0.51 mmol) in anhydrous dichloromethane was added to pyridine
(0.76e2.29 mmol) and acetyl chloride (0.76e2.29 mmol). The
mixture was stirred to room temperature for 8 h and the solvent
was removed in vacuum. The residue was purified by flash silica gel
column chromatography to obtain acetoxy-cinnamoyl decursin
derivatives (7d, 7g, 7j, 7m and 7p).
5.5.2. (7S)-(þ)-3-(2-Thienyl)-acrylic acid acid 8,8-dimethyl-2-oxo-
6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (6b)
5.6.1. (7S)-(þ)-3-Phenyl-acrylic acid acid 8,8-dimethyl-2-oxo-6,7-
dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (7a)
Yield 48.0%, white solid, mp: 149 ꢀC, Rf ¼ 0.67 (1:1 n-hex-
aneeethyl acetate);
½
a 2D5
ꢁ
þ33.0 (c
¼
3, CHCl3); 1H NMR
Yield 49.3%, white solid, mp: 136e137 ꢀC, Rf ¼ 0.40 (1:1 n-
(400 MHz, CDCl3): dH 7.77(1H, d, J ¼ 15.6 Hz, H-30), 7.58(1H, d,
J ¼ 9.2 Hz, H-4), 7.38(1H, d, J ¼ 4.8 Hz, H-60), 7.25(1H, d,
J ¼ 3.6 Hz, H-80), 7.17(1H, s, H-5), 7.04(1H, dd, J ¼ 3.6, 4.8 Hz, H-
70), 6.83(1H, s, H-10), 6.23(1H, d, J ¼ 9.6 Hz, H-3), 6.20(1H, d,
J ¼ 15.6 Hz, H-20), 5.18(1H, t, J ¼ 4.8 Hz, H-7), 3.23(1H, dd,
J ¼ 4.8, 17.2 Hz, H-6a), 2.92(1H, dd, J ¼ 4.8, 17.2 Hz, H-6b), 1.42
(3H, s, CH3-8), 1.38(3H, s, CH3-8); 13C NMR (100 MHz, CDCl3) dC
166.1(C-10), 161.2(C-2), 156.3(C-9a), 154.1(C-10a), 143.1(C-4), 139.1
(C-40), 138.2(C-30), 131.4(C-60), 128.9(C-70), 128.6(C-5), 128.1(C-80),
115.9(C-20), 115.6(C-5a), 113.3(C-3), 112.9(C-4a), 104.7(C-10), 76.6
(C-8), 70.1(C-7), 27.8(C-6), 24.9(CH3-8), 23.3(CH3-8); ESI-MS: m/
z ¼ 383 [M þ H]þ. Anal. Calc. for C21H18O5S: C, 65.95; H, 4.74; S,
8.38; Found: C, 65.90; H, 4.74; S, 8.36.
hexaneeethyl acetate); ½a D25
ꢁ
þ42.0 (c ¼ 3, CHCl3); 1H NMR
(400 MHz, acetone-d6): dH 7.88(1H, d, J ¼ 9.6 Hz, H-4), 7.70(3H, m,
H-30, H-50, H-90), 7.43(4H, m, H-5, H-60, H-70, H-80), 6.75(1H, s, H-10),
6.56(1H, d, J ¼ 16.0 Hz, H-20), 6.21(1H, d, J ¼ 9.2 Hz, H-3), 5.24(1H, t,
J ¼ 4.6 Hz, H-7), 3.34(1H, dd, J ¼ 4.6, 17.6 Hz, H-6a), 2.99(1H, dd,
J ¼ 4.4, 17.6 Hz, H-6b), 1.43(3H, s, CH3-8), 1.42(3H, s, CH3-8); 13C
NMR (100 MHz, acetone-d6) dC 166.4(C-10), 160.8(C-2), 157.1(C-9a),
155.0(C-10a), 146.1(C-30), 144.2(C-4), 135.0(C-40), 131.3(C-70), 130.2
(C-60), 130.2(C-80), 129.7(C-50), 129.7(C-90), 129.1(C-5), 118.4(C-20),
116.7(C-5a), 113.8(C-3), 113.7(C-4a), 104.5(C-10), 77.5(C-8), 70.8(C-
7), 28.2(C-6), 25.0(CH3-8), 23.6(CH3-8); ESI-MS: m/z
¼
377
[M þ H]þ. Anal. Calc. for C23H20O5: C, 73.39; H, 5.36. Found: C,
73.25; H, 5.38.

5572
K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
5.6.2. (7S)-(þ)-3-(2-Methoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7b)
H-70), 7.01(1H, s, H-50), 6.93(1H, dd, J ¼ 4.0, 8.4 Hz, H-80), 6.83(1H, s,
H-10), 6.40(1H, d, J ¼ 15.6 Hz, H-20), 6.23(1H, d, J ¼ 9.6 Hz, H-3), 5.19
(1H, t, J ¼ 4.8 Hz, H-7), 3.81(3H, s, OCH3-60), 3.24(1H, dd, J ¼ 4.8,
17.2 Hz, H-6a), 2.94(1H, dd, J ¼ 4.8, 17.2 Hz, H-6b), 1.44(3H, s,
CH3-8), 1.39(3H, s, CH3-8); 13C NMR (100 MHz, CDCl3) dC 166.2
(C-10), 161.2(C-2), 159.8(C-60), 156.3(C-9a), 154.1(C-10a), 145.8(C-30),
143.1(C-4), 135.3(C-40), 129.8(C-80), 128.7(C-5), 120.9(C-90), 117.5
(C-20), 116.5(C-70), 115.6(C-5a), 113.3(C-3), 112.9(C-50), 112.8(C-4a),
104.7(C-10), 77.2(C-8), 70.1(C-7), 55.2(OCH3-60), 27.87(C-6), 24.9
(CH3-8), 23.3(CH3-8); ESI-MS: m/z ¼ 407 [M þ H]þ. Anal. Calc. for
C24H22O6: C, 70.92; H, 5.46. Found: C, 70.77; H, 5.43.
Yield 81.8%, white solid, mp: 72 ꢀC, Rf ¼ 0.48 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ57.7 (c ¼ 3, CHCl3); 1H NMR (400 MHz,
CDCl3): dH 7.99(1H, d, J ¼ 16.4 Hz, H-30), 7.58(1H, d, J ¼ 9.6 Hz, H-4),
7.47(1H, d, J ¼ 6.4 Hz, H-90), 7.35(1H, t, J ¼ 7.8 Hz, H-70), 7.17(1H, s,
H-5), 6.96e6.89(2H, m, H-60, H-80), 6.80(1H, s, H-10), 6.50(1H, d,
J ¼ 16.0 Hz, H-20), 6.23(1H, d, J ¼ 9.6 Hz, H-3), 5.19(1H, t, J ¼ 5.0 Hz,
H-7), 3.87(3H, s, OCH3-50), 3.24(1H, dd, J ¼ 5.0, 17.2 Hz, H-6a), 2.94
(1H, dd, J ¼ 5.0, 17.2 Hz, H-6b), 1.43(3H, s, CH3-8), 1.39(3H, s, CH3-8);
13C NMR (100 MHz, CDCl3) dC 166.8(C-10), 161.3(C-2), 158.4(C-50),
156.4(C-9a), 154.1(C-10a), 143.1(C-4), 141.4(C-30), 131.8(C-70), 129.1
(C-90), 128.7(C-5), 122.9(C-80), 120.6(C-40), 117.7(C-20), 115.8(C-5a),
113.2(C-3), 112.8(C-4a), 111.0(C-60), 104.7(C-10), 77.1(C-8), 69.9
(C-7), 55.4(OCH3-50), 27.8(C-6), 25.0(CH3-8), 23.2(CH3-8); ESI-MS:
m/z ¼ 407 [M þ H]þ. Anal. Calc. for C24H22O6: C, 70.92; H, 5.46.
Found: C, 70.85; H, 5.45.
5.6.6. (7S)-(þ)-3-(3-Hydroxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7f)
Yield 88.1%, white solid, mp: 105 ꢀC, Rf ¼ 0.21 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ12.0 (c ¼ 1, CHCl3); 1H NMR(400 MHz,
acetone-d6): dH 8.61(1H, s, OH-60; disappeared after addition of
D2O), 7.86(1H, d, J ¼ 9.2 Hz, H-4), 7.62(1H, d, J ¼ 15.6 Hz, H-30), 7.44
(1H, s, H-5), 7.25(1H, t, J ¼ 7.8 Hz, H-80), 7.16(1H, d, J ¼ 7.6 Hz, H-90),
7.11(1H, s, H-50), 6.91(1H, d, J ¼ 8.4 Hz, H-70), 6.75(1H, s, H-10), 6.48
(1H, d, J ¼ 16.0 Hz, H-20), 6.21(1H, d, J ¼ 9.6 Hz, H-3), 5.22(1H, t,
J ¼ 4.6 Hz, H-7), 3.33(1H, dd, J ¼ 4.2, 17.2 Hz, H-6a), 2.98(1H, dd,
J ¼ 4.4,17.6 Hz, H-6b),1.43(3H, s, CH3-8),1.42(3H, s, CH3-8); 13C NMR
(100 MHz, acetone-d6) dC 166.4(C-10), 160.8(C-2), 158.6(C-60), 157.2
(C-9a),155.0(C-10a),146.2(C-30),144.3(C-4),136.4(C-40),130.8(C-80),
130.2(C-5),120.5(C-90), 118.5(C-70),118.3(C-20),116.8(C-5a),115.5(C-
50),113.8(C-3),113.7(C-4a),104.6(C-10), 77.5(C-8), 70.8(C-7), 28.2(C-
6), 25.0(CH3-8), 23.5(CH3-8); ESI-MS: m/z ¼ 393 [M þ H]þ. Anal.
Calc. for C23H20O6: C, 70.40; H, 5.14. Found: C, 70.29; H, 5.13.
5.6.3. (7S)-(þ)-3-(2-Hydroxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7c)
Yield 58.5%, white solid, m.p 106 ꢀC, Rf ¼ 0.39 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ16.3 (c ¼ 1, CHCl3); 1H NMR(400 MHz,
acetone-d6): dH 9.18(1H, s, OH-50; disappeared after addition of
D2O), 8.00(1H, d, J ¼ 16.4 Hz, H-30), 7.85(1H, d, J ¼ 9.6 Hz, H-4), 7.61
(1H, d, J ¼ 7.6 Hz, H-90), 7.43(1H, s, H-5), 7.25(1H, t, J ¼ 6.8 Hz, H-70),
6.95(1H, d, J ¼ 8.4 Hz, H-60), 6.88(1H, t, J ¼ 7.4 Hz, H-80), 6.74(1H, s,
H-10), 6.61(1H, d, J ¼ 16.0 Hz, H-20), 6.20(1H, d, J ¼ 9.6 Hz, H-3), 5.23
(1H, t, J ¼ 4.4 Hz, H-7), 3.33(1H, dd, J ¼ 4.4, 17.6 Hz, H-6a), 2.98(1H,
dd, J ¼ 4.4, 17.6 Hz, H-6b), 1.43(3H, s, CH3-8), 1.42(3H, s, CH3-8); 13
C
NMR (100 MHz, acetone-d6) dC 167.0(C-10), 160.8(C-2), 157.5(C-50),
157.2(C-9a), 155.1(C-10a), 144.3(C-4), 141.8(C-30), 132.5(C-70), 130.2
(C-90), 130.0(C-5), 122.0(C-80), 120.8(C-40), 118.0(C-20), 116.9(C-60),
116.9(C-5a), 113.8(C-3). 113.7(C-4a), 104.5(C-10), 77.6(C-8), 70.6
(C-7), 28.3(C-6), 25.0(CH3-8), 23.6(CH3-8); ESI-MS: m/z ¼ 393
[M þ H]þ. Anal. Calc. for C23H20O6: C, 70.40; H, 5.14. Found: C, 70.33;
H, 5.14.
5.6.7. (7S)-(þ)-3-(3-Acetoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7g)
Yield 87.0%, white solid, mp: 181 ꢀC, Rf ¼ 0.31 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ35.0 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
acetone-d6): dH 7.84(1H, d, J ¼ 9.6 Hz, H-4), 7.68(1H, d, J ¼ 16.0 Hz,
H-30), 7.55(1H, d, J ¼ 7.6 Hz, H-90), 7.45(3H, m, H-5, H-50, H-70), 7.18
(1H, dd, J ¼ 2.4, 7.6 Hz, H-80), 6.73(1H, s, H-10), 6.57(1H, d,
J ¼ 15.6 Hz, H-20), 6.19(1H, d, J ¼ 9.6 Hz, H-3), 5.23(1H, t, J ¼ 4.4 Hz,
H-7), 3.33(1H, dd, J ¼ 4.2,17.6 Hz, H-6a), 2.98(1H, dd, J ¼ 4.8,17.6 Hz,
H-6b), 2.25(3H, s, OAc-60), 1.43(3H, s, CH3-8), 1.42(3H, s, CH3-8); 13C
NMR (100 MHz, acetone-d6) dC 169.5(OC]O-60), 166.2(C-10), 160.8
(C-2), 157.1(C-9a), 155.0(C-10a), 152.3(C-60), 145.0(C-30), 144.2(C-4),
136.5(C-40), 130.7(C-80), 130.2(C-5), 126.5(C-90), 124.7(C-70), 122.1
(C-50), 119.5(C-20), 116.7(C-5a), 113.8(C-3), 113.7(C-4a), 104.6(C-10),
77.5(C-8), 71.0(C-7), 28.2(C-6), 25.0(CH3-8), 23.5(CH3-8), 20.8
(OCOCH3-60); ESI-MS: m/z ¼ 435 [M þ H]þ. Anal. Calc. for C25H22O7:
C, 69.12; H, 5.10. Found: C, 68.93; H, 5.08.
5.6.4. (7S)-(þ)-3-(2-Acetoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7d)
Yield 95.1%, white solid, mp: 61 ꢀC, Rf ¼ 0.47 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ8.7 (c ¼ 0.5, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.73(1H, d, J ¼ 16.0 Hz, H-30), 7.66e7.63(2H, m, H-90,
H-4), 7.43e7.39(1H, m, H-70), 7.25e7.23(2H, m, H-5, H-80), 7.11(1H,
d, J ¼ 6.8 Hz, H-60), 6.80(1H, s, H-10), 6.45(1H, d, J ¼ 16.4 Hz, H-20),
6.22(1H, d, J ¼ 9.6 Hz, H-3), 5.19(1H, t, J ¼ 4.8 Hz, H-7), 3.27(1H, dd,
J ¼ 4.4, 17.6 Hz, H-6a), 3.00(1H, dd, J ¼ 4.4, 17.6 Hz, H-6b), 2.31(3H, s,
OAc-50), 1.43(3H, s, CH3-8), 1.41(3H, s, CH3-8); 13C NMR (100 MHz,
CDCl3) dC 169.1(OC]O-50), 165.7(C-10), 161.2(C-2), 156.3(C-9a),
154.1(C-10a), 149.3(C-50), 143.1(C-4), 138.9(C-30), 131.5(C-70), 128.7
(C-5), 127.3(C-90), 126.7(C-80), 126.3(C-40), 123.1(C-60), 119.2(C-20)
115.5(C-5a), 113.3(C-3), 112.8(C-4a), 104.6(C-10), 77.2(C-8), 70.2
(C-7), 27.8(C-6), 24.8(CH3-8), 23.4(CH3-8), 20.7(OCOCH3-50);
ESI-MS: m/z ¼ 435 [M þ H]þ. Anal. Calc. for C25H22O7: C, 69.12; H,
5.10. Found: C, 69.03; H, 5.10.
5.6.8. (7S)-(þ)-3-(4-Methoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7h)
Yield 91.2%, white solid, mp: 68 ꢀC, Rf ¼ 0.20 (2:1 n-hexaneeethyl
acetate); ½a 2D5
ꢁ
þ21.9 (c ¼ 3, CHCl3); 1H NMR(400 MHz, CDCl3): dH
7.63(1H, d, J ¼ 16.0 Hz, H-30), 7.58(1H, d, J ¼ 9.6 Hz, H-4), 7.45(2H, d,
J ¼ 8.8 Hz, H-50, H-90), 7.17(1H, s, H-5), 6.85(2H, d, J ¼ 8.0 Hz, H-60, H-
80), 6.78(1H, s, H-10), 6.28(1H, d, J ¼ 16.0 Hz, H-20), 6.23(1H, d,
J ¼ 9.6 Hz, H-3), 5.18(1H, t, J ¼ 4.8 Hz, H-7), 3.82(3H, s, OCH3-70), 3.23
(1H, dd, J ¼ 4.4, 17.6 Hz, H-6a), 2.93(1H, dd, J ¼ 4.4, 17.6 Hz, H-6b),
1.43(3H, s, CH3-8), 1.39(3H, s, CH3-8); 13C NMR (100 MHz, acetone-
d6) dC; 166.7(C-10),162.6(C-70),160.8(C-2),157.2(C-9a),155.0(C-10a),
145.9(C-30), 144.2(C-4), 130.8(C-50), 130.8(C-90), 130.2(C-5), 127.6(C-
40), 116.8(C-5a), 115.6(C-20), 115.1(C-60), 115.1(C-80), 113.8(C-3), 113.7
(C-4a), 104.5(C-10), 77.5(C-8), 70.6(C-7), 55.7(OCH3-70), 28.3(C-6),
5.6.5. (7S)-(þ)-3-(3-Methoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7e)
Yield 90.9%, white solid, mp: 72 ꢀC, Rf ¼ 0.51 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ37.9 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.64(1H, d, J ¼ 16.0 Hz, H-30), 7.58(1H, d, J ¼ 9.6 Hz, H-4),
7.29(1H, d, J ¼ 8.4 Hz, H-90), 7.17(1H, s, H-5), 7.08(1H, d, J ¼ 8.0 Hz,

K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
5573
25.0(CH3-8), 23.5(CH3-8); ESI-MS: m/z ¼ 407 [M þ H]þ. Anal. Calc.
DMSO-d6): dH 9.63(1H, s, OH-70; disappeared after addition of D2O),
9.10(1H, s, OH-60; disappeared after addition of D2O), 7.90(1H, d,
J ¼ 9.6 Hz, H-4), 7.46(1H, s, H-5), 7.45(1H, d, J ¼ 15.2 Hz, H-30), 7.00
(1H, s, H-50), 6.99(1H, d, J ¼ 8.4 Hz, H-90), 6.81(1H, s, H-10), 6.71(1H,
d, J ¼ 8.4 Hz, H-80), 6.25(1H, d, J ¼ 9.6 Hz, H-3), 6.22(1H, d,
J ¼ 15.6 Hz, H-20), 5.14(1H, t, J ¼ 4.0 Hz, H-7), 3.24(1H, dd, J ¼ 4.0,
17.6 Hz, H-6a), 2.88(1H, dd, J ¼ 4.0,17.6 Hz, H-6b),1.35(3H, s, CH3-8),
1.31(3H, s, CH3-8); 13C NMR (100 MHz, CDCl3): dC 166.9(C-10), 162.3
(C-2), 156.6(C-9a), 154.0(C-10a), 147.0(C-70), 146.2(C-60), 144.2
(C-30), 143.9(C-4), 128.8(C-5), 126.8(C-40), 122.5(C-90), 116.0(C-5a),
115.3(C-80), 114.3(C-20), 114.1(C-3), 112.8(C-4a), 112.7(C-50), 104.7
(C-10), 76.8(C-8), 70.0(C-7), 27.8(C-6), 24.8(CH3-8), 23.3(CH3-8);
ESI-MS: m/z ¼ 409 [M þ H]þ. Anal. Calc. for C23H20O7: C, 67.64; H,
4.94. Found: C, 67.58; H, 4.95.
for C24H22O6: C, 70.92; H, 5.46. Found: C, 70.88; H, 5.49.
5.6.9. (7S)-(þ)-3-(4-Hydroxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7i)
Yield 82.3%, white solid, mp: 104 ꢀC, Rf ¼ 0.32 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ11.3 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.61(1H, d, J ¼ 16.0 Hz, H-30), 7.59(1H, d, J ¼ 9.6 Hz, H-4),
7.40(2H, d, J ¼ 8.8 Hz, H-50, H-90), 7.17(1H, s, H-5), 6.84(2H, d,
J ¼ 8.8 Hz, H-60, H-80), 6.83(1H, s, H-10), 6.26(1H, d, J ¼ 16.0 Hz,
H-20), 6.24(1H, d, J ¼ 9.6 Hz, H-3), 5.82(1H, s, OH-70; disappeared
after addition of D2O), 5.18(1H, t, J ¼ 4.6 Hz, H-7), 3.23(1H, dd,
J ¼ 4.6, 17.6 Hz, H-6a), 2.93(1H, dd, J ¼ 4.6, 17.6 Hz, H-6b), 1.43(3H, s,
CH3-8), 1.38(3H, s, CH3-8); 13C NMR (100 MHz, acetone-d6) dC 166.8
(C-10),160.8(C-2),160.7(C-70),157.2(C-9a),155.0(C-10a),146.2(C-30),
144.3(C-4), 131.0(C-50), 131.0(C-90), 130.2(C-5), 126.6(C-40), 116.8
(C-5a), 116.6(C-20), 114.8(C-60), 114.8(C-80), 113.7(C-3), 113.7(C-4a),
104.5(C-10), 77.5(C-8), 70.5(C-7), 28.2(C-6), 25.0(CH3-8), 23.5
(CH3-8); ESI-MS: m/z ¼ 393 [M þ H]þ. Anal. Calc. for C23H20O6: C,
70.40; H, 5.14. Found: C, 70.26; H, 5.13.
5.6.13. (7S)-(þ)-3-(3,4-Diacetoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7m)
Yield 84.5%, white solid, mp: 92 ꢀC, Rf ¼ 0.27 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ28.0 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.60(1H, d, J ¼ 16.0 Hz, H-30), 7.59(1H, d, J ¼ 9.6 Hz, H-4),
7.38e7.33(2H, m, H-50, H-90), 7.25e7.17(2H, m, H-5, H-80), 6.82(1H,
s, H-10), 6.35(1H, d, J ¼ 16.0 Hz, H-20), 6.23(1H, d, J ¼ 9.2 Hz. H-3),
5.19(1H, t, J ¼ 4.6 Hz, H-7), 3.24(1H, dd, J ¼ 4.6, 17.6 Hz, H-6a), 2.93
(1H, dd, J ¼ 4.6, 17.6 Hz, H-6b), 2.29(3H, s, OAc-60), 2.29(3H, s, OAc-
70), 1.42(3H, s, CH3-8), 1.38(3H, s, CH3-8); 13C NMR (100 MHz,
acetone-d6) dC 168.5(OC]O-60), 168.4(OC]O-70), 166.2(C-10), 160.8
(C-2),157.1(C-9a),155.0(C-10a),145.0(C-30),144.3(C-60),144.3(C-70),
143.7(C-4), 133.7(C-40), 130.2(C-5), 127.4(C-90), 124.9(C-80), 123.9
(C-50), 119.4(C-20), 116.7(C-5a), 113.8(C-3), 113.7(C-4a), 104.6(C-10),
77.5(C-8), 70.9(C-7), 28.2(C-6), 25.0(CH3-8), 23.6(CH3-8), 20.4
(OCOCH3-60), 20.4(OCOCH3-70); ESI-MS: m/z ¼ 493 [M þ H]þ. Anal.
Calc. for C27H24O9: C, 65.95; H, 4.91. Found: C, 65.88; H, 4.90.
5.6.10. (7S)-(þ)-3-(4-Acetoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7j)
Yield 63.3%, white solid, mp: 181 ꢀC, Rf ¼ 0.39 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ3.6 (c ¼ 0.3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.65(1H, d, J ¼ 16.0 Hz, H-30), 7.58(1H, d, J ¼ 9.6 Hz, H-4),
7.51(2H, d, J ¼ 8.4 Hz, H-50, H-90), 7.17(1H, s, H-5), 7.11(2H, d,
J ¼ 8.4 Hz, H-60, H-80), 6.83(1H, s, H-10), 6.37(1H, d, J ¼ 16.0 Hz,
H-20), 6.23(1H, d, J ¼ 9.2 Hz, H-3), 5.19(1H, t, J ¼ 4.8 Hz, H-7), 3.24
(1H, dd, J ¼ 4.8, 17.2 Hz, H-6a), 2.94(1H, dd, J ¼ 4.8, 17.2 Hz, H-6b),
2.30(3H, s, OAc-70), 1.39(3H, s, CH3-8), 1.35(3H, s, CH3-8); 13C NMR
(100 MHz, acetone-d6) dC 169.2(OC]O-70), 166.7(C-10), 160.8(C-2),
157.2(C-9a), 155.0(C-10a), 150.3(C-70), 145.1(C-30), 144.2(C-4), 130.2
(C-5), 129.2(C-40), 126.5(C-50), 126.5(C-90), 121.4(C-60), 121.4(C-80),
119.2(C-20), 116.8(C-5a), 113.8(C-3), 113.7(C-4a), 104.5(C-10), 77.5
(C-8), 70.6(C-7), 28.2(C-6), 25.0(CH3-8), 23.5(CH3-8), 20.7
(OCOCH3-70); ESI-MS: m/z ¼ 435 [M þ H]þ. Anal. Calc. for C25H22O7:
C, 69.12; H, 5.10. Found: C, 69.08; H, 5.09.
5.6.14. (7S)-(þ)-3-(3,4,5-Trimethoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7n)
Yield 52.9%, white solid, mp: 87 ꢀC, Rf ¼ 0.23 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ22.5 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.59(1H, d, J ¼ 16.0 Hz, H-30), 7.58(1H, d, J ¼ 10.0 Hz, H-4),
7.18(1H, s, H-5), 6.84(1H, s, H-10), 6.72(2H, s, H-50, H-90), 6.32(1H, d,
J ¼ 16.0 Hz, H-20), 6.24(1H, d, J ¼ 9.2 Hz, H-3), 5.20(1H, t, J ¼ 4.4 Hz,
H-7), 3.90(9H, s, OCH3-60, OCH3-70, OCH3-80), 3.25(1H, dd, J ¼ 4.4,
16.8 Hz, H-6a), 2.95(1H, dd, J ¼ 4.4, 16.8 Hz, H-6b), 1.45(3H, s,
CH3-8), 1.395(3H, s, CH3-8); 13C NMR (100 MHz, acetone-d6) dC
166.7(C-10), 160.8(C-2), 157.2(C-9a), 155.1(C-10a), 154.5(C-60), 154.5
(C-80), 146.5(C-30), 144.3(C-4), 141.3(C-70), 130.3(C-40), 130.2(C-5),
117.4(C-20), 116.8(C-5a), 113.8(C-3), 113.7(C-4a), 106.7(C-50), 106.6
(C-90), 104.6(C-10), 77.5(C-8), 70.6(C-7), 60.5(OCH3-70), 56.4
(OCH3-60), 56.4(OCH3-80), 28.3(C-6), 24.9(CH3-8), 23.7(CH3-8); ESI-
MS: m/z ¼ 467 [M þ H]þ. Anal. Calc. for C26H26O8: C, 66.94; H, 5.62.
Found: C, 66.81; H, 5.61.
5.6.11. (7S)-(þ)-3-(3,4-Dimethoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7k)
Yield 45.8%, white solid, mp: 83 ꢀC, Rf ¼ 0.35 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ41.5 (c ¼ 3, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.62(1H, d, J ¼ 16.0 Hz, H-30), 7.58(1H, d, J ¼ 9.6 Hz, H-4),
7.17(1H, s, H-5), 7.09(1H, d, J ¼ 8.4, H-90), 7.01(1H, s, H-50), 6.85(1H,
d, J ¼ 7.2 Hz, H-80), 6.84(1H, s, H-10), 6.28(1H, d, J ¼ 16.0 Hz, H-20),
6.24(1H, d, J ¼ 9.6 Hz, H-3), 5.20(1H, t, J ¼ 4.4 Hz, H-7), 3.91(3H, s,
OCH3-60), 3.90(3H, s, OCH3-70), 3.23(1H, dd, J ¼ 4.4, 16.8 Hz, H-6a),
2.96(1H, dd, J ¼ 4.4, 16.8 Hz, H-6b), 1.44(3H, s, CH3-8), 1.39(3H, s,
CH3-8); 13C NMR (100 MHz, CDCl3) dC 166.8(C-10), 160.8(C-2), 157.2
(C-9a), 155.0(C-10a), 152.6(C-60), 150.5(C-70), 146.4(C-30), 144.2(C-
4), 130.2(C-5), 127.9(C-40), 124.0(C-90), 116.8(C-5a),115.6(C-20), 113.8
(C-3), 113.7(C-4a), 112.1(C-80), 110.7(C-50), 104.6(C-10), 77.5(C-8),
70.5(C-7), 56.0(OCH3-60), 55.9(OCH3-70), 28.3(C-6), 25.0(CH3-8),
23.7(CH3-8); ESI-MS: m/z ¼ 437 [M þ H]þ. Anal. Calc. for C25H24O7:
C, 68.80; H, 5.54. Found: C, 68.70; H, 5.52.
5.6.15. (7S)-(þ)-3-(3,4,5-Trihydroxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7o)
Yield 18.2%, white solid, mp: 144 ꢀC, Rf ¼ 0.44 (5:1 chloroform-
methanol); ½a 2D5
ꢁ
þ24.4 (c ¼ 3, MeOH); 1H NMR(400 MHz, acetone-
d6): dH 8.16(2H, br, OH-60, OH-80; disappeared after addition of
D2O), 7.93(1H, br, OH-70; disappeared after addition of D2O), 7.84
(1H, d, J ¼ 9.6 Hz, H-4), 7.47(1H, d, J ¼ 15.6 Hz, H-30), 7.42(1H, s,
H-5), 6.73(1H, s, H-10), 6.72(2H, s, H-50, H-90), 6.22(1H, d,
J ¼ 16.0 Hz, H-20), 6.20(1H, d, J ¼ 9.6 Hz, H-3), 5.19(1H, t, J ¼ 4.8 Hz,
H-7), 3.31(1H, dd, J ¼ 4.8, 16.8 Hz, H-6a), 2.93(1H, dd, J ¼ 4.8,
16.8 Hz, H-6b), 1.42(3H, s, CH3-8), 1.41(3H, s, CH3-8); 13C NMR
5.6.12. (7S)-(þ)-3-(3,4-Dihydroxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7l)
Yield 93.2%, white solid, mp: 115 ꢀC, Rf ¼ 0.36 (1:2 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ19.3 (c ¼ 3, CHCl3); 1H NMR(400 MHz,

5574
K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
(100 MHz, acetone-d6) dC 166.7(C-10), 160.9(C-2), 157.2(C-9a), 155.0
(C-10a), 146.9(C-30), 146.6(C-60), 146.6(C-80), 144.3(C-4), 136.8(C-70),
130.2(C-5), 126.3(C-40), 116.9(C-5a), 115.0(C-20), 113.7(C-3), 113.7(C-
4a), 108.5(C-50), 108.5(C-90), 104.5(C-10), 77.6(C-8), 70.5(C-7), 28.3
(C-6), 25.0(CH3-8), 23.5(CH3-8); ESI-MS: m/z ¼ 425 [M þ H]þ. Anal.
Calc. for C23H20O8: C, 65.09; H, 4.75. Found: C, 65.05; H, 4.74.
130.4(C-90), 130.1(C-5), 129.1(C-70), 128.4(C-40), 121.0(C-80), 116.7
(C-5a), 113.7(C-3), 113.6(C-4a), 111.1(C-60), 104.5(C-10), 77.3(C-8),
70.6(C-7), 55.5(OCH3-50), 34.4(C-20), 30.3(C-30), 28.1(C-6), 25.0(CH3-
8), 23.4(CH3-8); ESI-MS: m/z ¼ 409 [M þ H]þ. Anal. Calc. for
C19H20O5: C, 69.50; H, 6.14. Found: C, 69.41; H, 6.15.
5.8. Method for the synthesis of compound (13)
5.6.16. (7S)-(þ)-3-(3,4,5-Triacetoxy-phenyl)-acrylic acid acid 8,8-
dimethyl-2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-
ester (7p)
A solutionof trans-cinnamic acid(9, 34.2 mmol)andconcentrated
sulfuric acid (5 drops) in MeOH (20 ml) was warmed to reflux over-
night. After cooling to room temperature, the solvent was removed
under the reduced pressure. The residue was purified by flash silica
gel column chromatography to obtain 3-phenyl-acrylic acid methyl-
ester (10). A solution of 3-phenyl-acrylic acid methyl-ester (10,
24.7 mmol) in dichloromethane anhydrous was cooled to ꢃ78 ꢀC
under the nitrogen gas. The mixture was slowly added to 1 M solu-
tion of diisobutylalluminum hydride (DIBALH) in hexane (74 mmol).
After stirring at 0 ꢀC for 1 h, the mixture was added with methanol
(22 ml) and stirred for 30 min to room temperature. The mixture was
added with aqueous saturated Rochelle’s salt (88 ml) and vigorously
stirred for 2 h. The reaction mixture was separated with dichloro-
methane, dried with sodium sulfate and the solvent was removed
under reduced pressure. The residue was purified by flash silica gel
column chromatography to obtain 3-phenyl-pro-2-pen-1-ol (11).
3-Phenyl-pro-2-pen-1-ol (11, 7.45 mmol) was dissolved in
dichloromethane anhydrous and added 1 M solution of boron tri-
bromide in dichloromethane (2.61 mmol) in ice bath. After stirring
1 h, the mixture was added ice water (50 ml) and stirred for 10 min.
The reaction mixture was separated using saturated sodium bicar-
bonate and diethyl ether. Organic layer was dried with sodium
sulfate and concentrated in vacuo. The residue was purified by flash
silica gel column chromatography to obtain (3-bromo-prophenyl)-
benzene (12). A solution of (þ)-decursinol (1, 0.41 mmol) in
N,N-dimethyl formamide anhydrous was cooledto ꢃ20 ꢀC andadded
to (3-bromo-prophenyl)-benzene (12, 0.609 mmol). After stirring to
ꢃ20 ꢀC for 24 h, the reaction mixture was fastly filtrated on silica gel
short-column chromatography using 5:1 n-hexaneeethyl acetate.
After the solvent was removed under the reduced pressure, the
residue was purified by silica gel column chromatography to obtain
(S)-(þ)-2,2-dimethyl-3(3-phenyl-allyloxy)-3,4-dihydro-4H-pyrano
[3,2-g]chromen-8-one (13).
Yield 19.5%, white solid, mp: 118 ꢀC, Rf ¼ 0.38 (1:2 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ8.7 (c ¼ 1, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 6.58(1H, d, J ¼ 9.6 Hz, H-4), 6.55(1H, d, J ¼ 17.2 Hz, H-30),
7.28e7.25(2H, s, H-50, H-90), 7.17(1H, s, H-5), 6.82(1H, s, H-10), 6.34
(1H, d, J ¼ 16.0 Hz, H-20), 6.23(1H, d, J ¼ 9.6 Hz, H-3), 5.18(1H, t,
J ¼ 4.8 Hz, H-7), 3.23(1H, dd, J ¼ 4.8, 17.6 Hz, H-6a), 2.92(1H, dd,
J ¼ 4.8, 17.6 Hz, H-6b), 2.29(9H, s, OAc-60, OAc-70, OAc-80), 1.41(3H, s,
CH3-8), 1.38(3H, s, CH3-8); 13C NMR (100 MHz, acetone-d6) dC 168.3
(OC]O-60), 168.3(OC]O-80), 167.4(OC]O-70), 166.0(C-10), 160.8
(C-2), 157.2(C-9a), 155.1(C-10a), 145.0(C-30), 144.3(C-4), 143.7(C-60),
143.7(C-80), 133.3(C-70), 132.6(C-40),130.2(C-5), 121.4(C-50), 121.4
(C-90), 120.4(C-20), 116.7(C-5a), 113.8(C-3), 113.8(C-4a), 104.6(C-10),
77.5(C-8), 71.1(C-7), 28.2(C-6), 25.0(CH3-8), 23.6(CH3-8), 20.4
(OCOCH3-60), 20.4(OCOCH3-80), 19.9(OCOCH3-70); ESI-MS: m/
z ¼ 551 [M þ H]þ. Anal. Calc. for C29H26O11: C, 63.27; H, 4.76. Found:
C, 63.22; H, 4.74.
5.7. General method for the synthesis of compounds (8aeb)
The mixture of phenylpropionic acid (0.812 mmol), DCC
(0.812 mmol) and 4-DMAP (0.162 mmol) was dissolved in anhy-
drous dichloromethane. (S)-(þ)-Decursinol (1, 0.406 mmol) was
added thereto to react together with stirring to room temperature
for 5e12 h. The mixture was washed with dichloromethane,
filtrated and concentrated in vacuo. The residue was purified by
flash silica gel column chromatography.
5.7.1. (7S)-(þ)-Phenylpropionic acid 8,8-dimethyl-2-oxo-6,7-
dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (8a)
Yield 76.8%, white solid, mp: 106 ꢀC, Rf ¼ 0.63 (1:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ55.05 (c ¼ 6, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.57(1H, d, J ¼ 9.6 Hz, H-4), 7.22(2H, d, J ¼ 7.6 Hz, H-50,
H-90), 7.19e7.12(3H, m, H-60, H-70, H-80), 7.10(1H, s, H-5), 6.78(1H, s,
H-10), 6.23(1H, d, J ¼ 9.6 Hz, H-3), 5.02(1H, t, J ¼ 4.8 Hz, H-7), 3.12
(1H, dd, J ¼ 4.8, 17.2 Hz, H-6a), 2.92(1H, t, J ¼ 7.6 Hz, H-6b), 2.74(2H,
dd, J ¼ 5.2, 17.6 Hz, 2H-30), 2.65(2H, t, J ¼ 7.2 Hz, 2H-20), 1.29(3H, s,
CH3-8), 1.29(3H, s, CH3-8); 13C NMR (100 MHz, acetone-d6) dC 172.4
(C-10), 160.8(C-2), 157.1(C-9a), 155.0(C-10a), 144.2(C-4), 141.3(C-40),
130.1(C-5), 129.1(C-60), 129.1(C-80), 129.0(C-50), 129.0(C-90), 126.9
(C-70), 116.7(C-5a), 113.8(C-3), 113.6(C-4a), 104.5(C-10), 77.3(C-8),
70.7(C-7), 36.0(C-20), 31.3(C-30), 28.1(C-6), 24.9(CH3-8), 23.4
(CH3-8); ESI-MS: m/z ¼ 379 [M þ H]þ. Anal. Calc. for C19H20O5: C,
69.50; H, 6.14, Found: C, 69.43; H, 6.13.
5.8.1. (S)-(þ)-8,8-Dimethyl-7-(3-phenyl-allyloxy)-6,7-dihydro-
2H,8H-pyrano[3,2-g]chromen-2-one(13)
Yield 32.7%, white solid, mp: 143 ꢀC, Rf ¼ 0.39 (2:1 n-hex-
aneeethyl acetate); ½a D25
ꢁ
þ 117.6 (c ¼ 1, CHCl3); 1H NMR(400 MHz,
CDCl3): dH 7.56(1H, d, J ¼ 9.6 Hz, H-4), 7.38e7.23(5H, m, H-50, H-60,
H-70, H-80, H-90), 7.15(1H, s, H-5), 6.76(1H, s, H-10), 6.59(1H, d,
J ¼ 16.0 Hz, H-30), 6.30e6.23(1H, m, H-20), 6.20(1H, d, J ¼ 9.6 Hz,
H-3), 4.34(1H, dd, J ¼ 6.0, 12.8 Hz, H-1a0), 4.21(1H, dd, J ¼ 6.0,
12.4 Hz, H-1b0), 3.59(1H, dd, J ¼ 5.2, 7.6 Hz, H-7), 3.07(1H, dd,
J ¼ 4.8, 16.0 Hz, H-6a), 2.85(1H, dd, J ¼ 7.2, 16.4 Hz, H-6b), 1.41(3H, s
CH3-8), 1.36(3H, s, CH3-8); 13C NMR (100 MHz, acetone-d6) dC 160.9
(C-2), 157.6(C-9a), 155.0(C-10a), 144.3(C-4), 132.7(C-40), 130.2(C-5),
129.4(C-30), 129.3(C-60), 129.3(C-80), 128.4(C-70), 127.3(C-50), 127.3
(C-90), 127.2(C-20), 118.1(C-5a), 113.5(C-3), 113.4(C-4a), 104.3(C-10),
78.6(C-7), 76.2(C-8), 20.7(C-10), 27.7(C-6), 26.0(CH3-8), 22.1
(CH3-8); ESI-MS: m/z ¼ 363 [M þ H]þ. Anal. Calc. for C23H22O4: C,
76.22; H, 6.12; Found: C, 76.20; H, 6.10.
5.7.2. (7S)-(þ)-2-Methoxy-phenylpropionic acid acid 8,8-dimethyl-
2-oxo-6,7-dihydro-2H,8H-pyrano[3,2-g]chromen-7-yl-ester (8b)
Yield 77.7%, Colorless oil, Rf ¼ 0.65 (1:1 n-hexaneeethyl acetate);
½
a 2D5
ꢁ
þ 48.4(c ¼ 10, CHCl3); 1H NMR(400 MHz, CDCl3): dH 7.57(1H, d,
J ¼ 9.6 Hz, H-4), 7.17(1H, t, J ¼ 9.8 Hz, H-70), 7.10(1H, s, H-5), 7.06(1H,
d, J ¼ 8.8 Hz, H-90), 6.83e6.80(2H, m, H-60, H-80), 6.78(1H, s, H-10),
6.23(1H, d, J ¼ 9.6 Hz, H-3), 5.01(1H, t, J ¼ 4.8 Hz, H-7), 3.76(3H, s,
OCH3-50), 3.13(1H, dd, J ¼ 4.4, 17.2 Hz, H-6a), 2.90(2H, t, J ¼ 7.4 Hz,
2H-30), 2.75(1H, dd, J ¼ 5.2,17.6 Hz, H-6b), 2.63(2H, t, J ¼ 8.0 Hz, 2H-
20), 1.31(6H, s, 2ꢄ CH3-8); 13C NMR (100 MHz, acetone-d6) dC 172.6
(C-10), 160.8(C-2), 158.3(C-50), 157.1(C-9a), 155.0(C-10a), 144.2(C-4),
5.9. Biology
5.9.1. Melanogenesis inhibition assay
B16 murine melanoma cells were obtained from the Korean Cell
Line Bank (Seoul, Korea). Cells were maintained in Dulbecco’s

K. Lee et al. / European Journal of Medicinal Chemistry 45 (2010) 5567e5575
5575
[5] E. Beradesca, N. Cameli, G. Primavera, M. Carrera, Dermatol. Surg. 32 (2006)
526e531.
[6] K. Yoshimura, K. Sato, E. Aiba-Kojima, D. Matsumoto, C. Machino, T. Nagase,
K. Gonda, I. Koshima, Dermatol. Surg. 32 (2006) 365e371.
[7] H. Matsuda, S. Nakashima, Y. Oda, S. Nakamura, M. Yoshikawa, Bioorg. Med.
Chem. 17 (2009) 6048e6053.
[8] C.W. Lee, E.-M. Son, H.S. Kim, P. Xu, T. Batmunkh, B.-J. Lee, K.A. Koo, Bioorg.
Med. Chem. Lett. 17 (2007) 5462e5464.
[9] Y. Tokiwa, M. Kitagawa, T. Raku, S. Yanagitanib, K. Yoshino, Bioorg. Med.
Chem. Lett. 17 (2007) 3105e3108.
modified Eagle’s medium (DMEM) supplemented with 10% heat-
inactivated fetal bovine serum (Invitrogen, Carlsbad, NM, USA) and
1% penicillin-streptomycin (10,000 U/ml and 10,000
mg/ml,
respectively) in 5% CO2 at 37 ꢀC. Extracellular melanin release was
measured as described previously [28]. Cells were incubated at
a density of 1 ꢄ 105 cells in six-well plates overnight. Alpha-MSH
(Sigma, St. Louis, MO, USA) was then added and cells were treated
with or without chemicals in phenol red free DMEM for 2 d.
Amounts of melanin in the media were measured at 405 nm.
[10] J.-S. Park, D.H. Kim, J.K. Lee, J.Y. Lee, D.H. Kim, H.K. Kim, H.-J. Lee, H.C. Kim,
Bioorg. Med. Chem. Lett. 20 (2010) 1162e1164.
[11] P. Thanigaimalai, T.A.L. Hoang, K.-C. Lee, S.-C. Bang, V.K. Sharma, C.Y. Yun,
E. Roh, B.-Y. Hwang, Y. Kim, S.-H. Jung, Bioorg. Med. Chem. Lett. 20 (2010)
2991e2993.
[12] M. Criton, V.L. Mellay-Hamon, Bioorg. Med. Chem. Lett. 18 (2008) 3607e3610.
[13] S. Okombi, D. Rival, S. Bonnet, A.-M. Mariotte, E. Perrierb, A. Boumendjel,
Bioorg. Med. Chem. Lett. 16 (2006) 2252e2255.
[14] P. Thanigaimalai, K.-C. Lee, S.-C. Bang, J.-H. Lee, C.-Y. Yun, E. Roh, B.-Y. Hwang,
Y. Kim, S.-H. Jung, Bioorg. Med. Chem. 18 (2010) 1555e1562.
[15] S. Nakashima, H. Matsuda, Y. Oda, S. Nakamura, F. Xu, M. Yoshikawa, Bioorg.
Med. Chem. 18 (2010) 2337e2345.
5.9.2. Cytotoxicity test
After treatment the cells with or without chemicals for 24 h,
5 mg/ml MTT in PBS was added to each well. Cells were incubated
at 37 ꢀC for 3 h and DMSO was added to dissolve the formazan
crystals. The absorbance was measured at 570 nm with a micro-
plate reader (Molecular Devices, USA).
[16] Y. Yamazaki, Y. Kawano, A. Yamanaka, S. Maruyama, Bioorg. Med. Chem. Lett.
19 (2009) 4178e4182.
Acknowledgements
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[18] L.V. NA, J.H. Koo, H.Y. Yoon, J. Yu, K.A. Kim, I.H. Choi, K.B. Kwon, K.S. Kwon,
H.U. Kim, J.W. Park, B.H. Park, Int. J. Mol. Med. 20 (2007) 763e767.
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[22] G.Y. Song, J.H. Lee, M. Cho, B.S. Park, D.E. Kim, S. Oh, Mol. Pharmacol. 72 (2007)
1599e1606.
This work was (partly) supported by the RIC program of MKE
(Ministry of Knowledge Economy) in Daejeon University and the
Priority Research Centers Program (2009-0093815) and Mid-Career
Researcher Program (2010-0000222) through the National
Research Foundation of Korea (NRF) funded by the Ministry of
Education, Science and Technology.
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