Kaohsiung Medical University Institutional Repository:Item 310902000/14146

Synthesis and Evaluation of the Cytotoxicities of Neoflavenes

Sie-Rong Lia( ), Hsing-Ming Chenb( ), Po-Yuan Chenc( ), Jui-Chi Tsaia( ), Liang-Yeu Chena( ), Eng-Chi Wangc* ( ), Yi-Ting Huangd( ), Yun-Chen Weid( ) and Pei-Jung Lud* ( ) a

Institute of Pharmaceutical Sciences, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C. b

School of Medical and Health Sciences, Fooyin University, Kaohsiung 831, Taiwan, R.O.C. c

Faculty of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan, R.O.C.

d

Institute of Clinical Medicine, National Cheng Kung University, Tainan, Taiwan, R.O.C.

The synthesis of neoflavene and neoflavenes with methoxy substituents at different positions are de-scribed. As starting materials, various salicylaldehydes were run through sequential reactions such as O-allylation, Grignard reaction, oxidation, Wittig reaction, and ring-closing metathesis to yield the target neoflavenes in good yield. Among the prepared neoflavenes, 7-methoxy-4¢-methoxyneoflavene (6e) and 8-methoxy-4¢-methoxyneoflavene (6f) exhibiting potential cell toxicities against various cells were dis-closed. In particular, 6f which exhibited an IC50value of 6.5± 2.0 and 5.1 ± 1.1 mM against gastric carci-noma and lung carcicarci-noma cells in vitro was found, respectively. Meanwhile, the structure and activity rela-tionship of our synthesized neoflavenes is further discussed briefly.

Keywords: Neoflavenes; Ring-closing metathesis; Cytotoxicities.

INTRODUCTION

Neoflavenes, which chemically belong to 4-phenyl-2H-chromenes or 4-phenyl-2H-1-benzopyrans, were origi-nally isolated from natural sources1and were only paid lit-tle attention about their biological activities in current re-search.2Moreover, even some strategies for the syntheses of neoflavenes have been developed,3-7but their drawbacks include tedious reaction conditions, low yield, and com-mercially unavailable starting materials. Since the Grubbs’ catalyst was discovered in 1995, the ring-closing metathe-sis (RCM) has been widely employed in various aspects in organic synthesis.8In particular, some heterocyclic com-pounds which were difficult to prepare, can be synthesized by RCM.

Furthermore, before our previous study,9the syn-thesis of neoflavenes which utilized RCM, has never been reported in current literature reports. In this our ex-tended study, we would like to report a brief, efficient, and straightforward synthetic approach to the neoflavene skel-eton and neoflavenes with methoxy substituents at various positions from commercially available salicylaldehydes. Our synthetic strategy is depicted in Scheme I. In addition,

the cytotoxic activities of the prepared neoflavenes against various cells such as human esophageal carcinoma cells, cervical carcinoma cells, etc., are also investigated (Table 1).

RESULTS AND DISCUSSION

As in the general procedure, a mixture of salicylalde-hydes (1) and allyl bromide in acetonitrile in the presence of K2CO3was heated to reflux to give 1-allyloxybenzalde-hydes (2a-g) in 95-98% yields. Subsequently, 2a-g were respectively reacted with arylmagnesium chloride to give (2-allyloxyphenyl)arylmethanol 3a-g in 91-96% yields. Compound 3a was used as a model for the oxidation under various conditions, such as Dess-Martin oxidation,10Swern oxidation,11and MnO2to give 4a in 89%, 92% and 90% yield, respectively. For the reason of easy handling and economic concerns, MnO2was chosen for oxidizing 3a-g to give compounds 4a-g in 90-96% yields. Then, com-pounds 4 were reacted with methylenetriphenylphosphane which had been generated from methyltriphenylphospho-nium bromide and potassium tert-butoxide in situ, to un-dergo the Wittig reaction to give dienes 5a-g in 92-98%

* Corresponding author. Fax: +886-7-3125339 (E. C. Wang); +886-6-3028162 (P. J. Lu); E-mail: [email protected]; [email protected]

yields. Subsequently, the dienes which were obtained were respectively subjected to RCM using Grubbs’ catalyst (II) to produce the desired neoflavenes (6a-g) in 90-93% yields. The structure elucidation of neoflavenes (6a-g) was con-firmed by spectral data such as1H-NMR,13C-NMR, EI-MS, and HRMS. Furthermore, the cytotoxicity studies of the prepared neoflavenes were investigated and depicted as follows. Eight cell lines including human esophageal carci-noma (CE81T), cervical carcicarci-noma (Hela), oral squamous carcinoma (SAS), gastric carcinoma (AGS), lung carci-noma (A549), renal cell carcicarci-noma (786-O), hepatocellular carcinoma (SKHep) and prostate cancer (PC3) were used for cytotoxicity screening in vitro. The IC50results are sum-marized in Table 1.

As shown in Table 1, two of the prepared compounds

6e and 6f exhibited inhibitory effects on various cells and

had significant activity in human esophageal carcinoma (CE81T), cervical carcinoma (Hela), oral squamous carci-noma (SAS), gastric carcicarci-noma (AGS), lung carcicarci-noma (A549), hepatocellular carcinoma (SKHep) and prostate cancer (PC3). Conversely, compound 6a-d, and 6g did not have conspicuous signals in this test. In the present studies, regarding the activity against individual cell lines, com-pound 6f exhibited the highest cytotoxic activity among our synthesized neoflavenes. The IC50(mM) of 6f toward CE81T, Hela, SAS, AGS, A549, RCC 786-O SKHep and PC3 are 10.8± 1.6, 10.7 ± 4.2, 13.2 ± 4.3, 6.5 ± 2.0, 5.1 ± 1.1, 10.6± 2.2, 9.9 ± 2.0, and 15.4 ± 5.4, respectively. Com-pared to 6f, the second potent compound was compound 6e which showed similar cytotoxicities in seven examined

Scheme I Synthetic strategy of neoflavenes from salicylaldehydes

Table 1. The cytotoxicities of neoflavene analogues

Cell lines CE 81T Hela SAS AGS A549 RCC 786-O SKHep PC-3

Compds IC50 (mM) IC50 (mM) IC50 (mM) IC50 (mM) IC50 (mM) IC50 (mM) IC50 (mM) IC50 (mM) 6a ND ND ND ND ND ND ND ND 6b ND ND ND 15.9± 4.2 ND ND ND ND 6c ND ND ND ND ND ND ND ND 6d ND ND ND ND 12.4± 0.7 ND ND ND 6e 09.8± 1.8 11.0 ± 3.6 13.2 ± 1.6 9.1 ± 2.7 08.9± 0.8 ND 9.6± 1.7 15.8 ± 3.9 6f 10.8± 1.6 10.7 ± 4.2 13.2 ± 4.3 6.5 ± 2.0 05.1± 1.1 10.6 ± 2.2 9.9 ± 2.0 15.4 ± 5.4 6g ND ND ND ND 25.5± 3.8 ND ND ND * ND: Not Detected

cancer cell lines, but no cytotoxicity to the renal carcinoma RCC786-O cells.

CONCLUSION

Mainly based on RCM, neoflavene and neoflavenes with methoxy substituents at different positions were syn-thesized. The prepared neoflavenes 6a, 6b, 6c, and 6g, which all have no methoxy group at the 4¢-position in the structure, exhibited almost no cytotoxicity to the examined cancer cell lines. The neoflavene derivative 6d, which has a 4¢-methoxy group but no methoxy group at the 7-position, or 8-position, showed cytotoxicity to A549 but no cyto-toxicity to the other cancer cell lines examined. Thus, the basic requirement for common cyctoxic activities must have a methoxy group at the 4¢-position on the structure of neoflavenes (6e-f). In addition, the methoxy group pre-sented at 8- and 7-positions (compound 6f, 6e) enhanced the cytotoxic activities, respectively.

EXPERIMENTAL

Melting points (Yanaco micro melting-point appara-tus) were uncorrected.1H-NMR and13C-NMR spectra were obtained on a Varian Gemini-200 or Varian Unity plus 400 Spectrometer. Chemical shifts are indicated in parts per million with respect to TMS. Elemental analyses were re-corded on a Heraeus CHN-O rapid analyzer. Mass spectra were recorded on a Chem/hp/middle spectrometer con-nected to a Hewlett Packard series II model gas-liquid chromatograph. HRMS spectra were performed on a JEOL JMS SX/SX 102A instrument. Silica gel (230-400 mesh) for column chromatography and precoated silica gel plates (60 F-254) for TLC were purchased from E. Merck Co. UV light (254 nm) was used to detect spots on TLC plates after development.

General procedure for the preparation of 2-allyloxy-benzaldehydes (2a-c)

As a general procedure, the solution of 2-hydroxy-benzaldehyde (1a-c) (100 mmol) in dry acetonitrile (80 mL) was stirred and anhydrous K2CO3(16.59 g, 120 mmol), allyl bromide (14.52 g, 120 mmol) in sequence were added, under dry nitrogen. The reaction mixture which was ob-tained was heated to reflux for 4 hr. Work-up as in the usual procedure, and purified by silica-gel column chromatogra-phy with ethyl acetate/n-hexane (1/15) as eluent, to yield pure 2a-c, respectively.

2-Allyloxybenzaldehyde (2a)12

(15.40 g, 95%) was obtained as colorless liquid, Rf=

0.16 (ethyl acetate: n-hexane = 1: 15),1H-NMR (CDCl3, 400 MHz)d 4.65 (dt, J = 5.2 Hz, 1.2 Hz, 2H, OCH2CH=CH2), 5.34 (ddt, J = 10.4 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH=CHaHb), 5.45 (ddt, J = 17.2 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH=CHaHb), 6.01 (ddt, J = 17.2 Hz, 10.4 Hz, 5.2 Hz, 1H, OCH2CH=CH2), 6.97 (dd, J = 8.8 Hz, 0.8 Hz, 1H, ArH), 7.02 (td, J = 8.8 Hz, 0.8 Hz, 1H, ArH), 7.52 (td, J = 7.6 Hz, 1.6 Hz, 1H, ArH), 7.83 (dd, J = 7.6 Hz, 1.6 Hz, 1H, ArH), 10.53 (s, 1H, CHO); 13 C-NMR (CDCl3, 100 MHz) d 69.04, 112.76, 117.93, 120.73, 124.96, 128.27, 132.28, 135.75, 160.83, 189.62; EI-MS (70 eV) m/z (rel. intensity, %) 163 ([M+1]+, 100), 162 (M+, 24), 161 (54), 133 (24), 121 (76), 120 (19), 105 (18), 92 (26); HRMS calcd for C10H10O2: 162.0681. Found: 162.0680.

2-Allyloxy-4-methoxybenzaldehyde (2b)13

(18.24 g, 95%) was obtained as colorless crystal, mp 37-38°C, Rf= 0.33 (ethyl acetate: n-hexane = 1: 6),1 H-NMR (CDCl3, 200 MHz)d 3.85 (s, 3H, OCH3), 4.62 (dt, J = 5.2, 1.4 Hz, 2H, OCH2CH=CH2), 5.33 (dd, J = 10.6, 1.4 Hz, 1H, OCH2CH=CH2), 5.45 (dd, J = 17.4, 1.2 Hz, 1H, OCH2CH=CH2), 6.04 (ddt, J = 17.4, 10.6, 5.2 Hz, 1H, OCH2CH=CH2), 6.43 (d, J = 2.0 Hz, 1H, ArH), 6.54 (dd, J = 8.8, 2.0 Hz, 1H, ArH), 7.81 (d, J = 8.8 Hz, 1H, ArH), 10.35 (s, 1H, CHO);13C-NMR (CDCl3, 100 MHz)d 55.56, 69.11, 98.97, 106.00, 118.06, 119.20, 130.44, 132.23, 162.62, 165.99, 188.24; EI-MS (70 eV) m/z (rel. intensity, %) 193 ([M+1]+, 30), 192 (M+, 35), 164 (28), 163 (54), 151 (100), 150 (91), 135 (45), 122 (27) , 95 (28); HRMS calcd for C11H12O3: 192.0786. Found: 192.0784.

2-Allyloxy-3-methoxybenzaldehyde (2c)14

(18.82 g, 98%) was obtained as colorless liquid, Rf= 0.26 (ethyl acetate: n-hexane = 1: 6),1H-NMR (CDCl3, 200 MHz)d 3.86 (s, 3H, OCH3), 4.62 (dt, J = 6, 1.2 Hz, 2H, OCH2CH=CH2), 5.33 (dd, J = 10.2, 1.2 Hz, 1H, OCH2CH=CH2), 5.45 (dd, J = 17.4, 1.2 Hz, 1H, OCH2CH=CH2), 6.04 (ddt, J = 17.4, 10.2, 6 Hz, 1H, OCH2CH=CH2), 7.10 (m, 2H, ArH), 7.37 (dd, J = 6.2 ,3.2 Hz, 1H, ArH), 10.41 (s, 1H, CHO); 13C-NMR (CDCl3, 100 MHz) d 55.89, 75.03, 113.34, 117.87, 118.86, 123.99, 129.97, 133.01, 151.05, 152.85, 190.18; EI-MS (70 eV) m/z (rel. intensity, %) 193 ([M+1]+, 100), 192 (M+, 54), 175 (17), 166 (20), 164 (29), 163 (55), 151 (83), 136 (17), 131 (20), 122 (20); HRMS calcd for C11H12O3: 192.0781. Found: 192.0783.

General procedure for the preparation of (2-allyloxy-phenyl)aryl methanol (3a-g)

To a stirred solution of 1-allyloxybenzaldehyde (2) (30 mmol) in THF (100 mL) was added phenyl-magnesium

chloride (2.0 M in THF) (36 mmol) in drops. And then the reaction mixture was continually stirred for 2 hr at room temperature. The resulting solution was concentrated in vacuo, and the residue which was obtained was purified by column chromatography on silica gel (ethyl acetate: n-hex-ane = 1: 15) to give pure 3a-g.

(2-Allyloxyphenyl)phenylmethanol (3a)

(6.62 g, 92%) was obtained as colorless crystals, mp 50-51°C, Rf= 0.10 (ethyl acetate: n-hexane = 1: 15),1 H-NMR (CDCl3, 400 MHz)d 3.30 (br d, J = 5.6 Hz, 1H, OH), 4.49 (dt, J = 5.2 Hz, 1.2 Hz, 2H, OCH2CH=CH2), 5.12 (ddt, J = 10.4 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH=CHaHb), 5.28 (ddt, J = 17.2 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH=CHaHb), 5.92 (ddt, J = 17.2 Hz, 10.4 Hz, 5.2 Hz, 1H, OCH2CH=CH2), 6.07 (d, J = 5.6 Hz, 1H, ArCH(OH)Ph), 6.84 (d, J = 8.4 Hz, 1H, ArH), 6.93 (d, J = 7.4 Hz, 1H, ArH), 7.18-7.48 (m, 7H, ArH);13C-NMR (CDCl3, 100 MHz)d 69.00, 72.28, 112.11, 117.54, 120.99, 126.50, 127.07, 127.86, 128.07, 128.55, 132.44, 132.91, 143.44, 155.68; EI-MS (70 eV) m/z (rel. intensity, %) 240 (M+, 12), 200 (13), 199 (100), 197 (10), 194 (10), 182 (13), 181 (83), 153 (13), 152 (27), 121 (90), 107 (11), 105 (30), 77 (37); HRMS calcd for C16H16O2: 240.1145. Found: 240.1147.

(2-Allyloxy-4-methoxyphenyl)phenylmethanol (3b)

(7.73 g, 95%) was obtained as colorless liquids, Rf= 0.08 (ethyl acetate: n-hexane = 1: 19),1H-NMR (CDCl3, 200 MHz)d 3.10 (br d, J = 3.6 Hz, 1H, OH), 3.73 (s, 3H, OCH3), 4.44 (dt, J = 5.2, 1.4 Hz, 2H, OCH2CH=CH2), 5.21 (ddt, J = 10.2, 1.4, 1.4 Hz, 1H, OCH2CH=CHaHb), 5.29 (ddt, J = 17.2, 1.4, 1.4 Hz, 1H, OCH2CH=CHaHb), 5.91 (ddt, J = 17.2, 10.2, 5.2 Hz, 1H, OCH2CH=CCHaHb), 5.99 (d, J = 5.6 Hz, 1H, ArCH(OH)Ph), 6.41 (s, 1H, ArH), 6.42 (m, 1H, ArH), 7.22 (m, 6H, ArH);13C-NMR (CDCl3, 50 MHz) d 55.21, 68.79, 71.54, 99.80, 104.38, 117.47, 125.03, 126.32, 126.83, 127.93, 128.38, 132.66, 143.59, 156.47, 160.01; EI-MS (70 eV) m/z (rel. intensity, %) 271 ([M+1]+, 3), 270 (M+, 12), 229 (35), 227 (12), 211 (43), 168 (15), 165 (53), 164 (100), 152 (25), 151 (56), 137 (22), 106 (37), 77 (15); HRMS calcd for C17H18O3: 270.1250. Found: 270.1253.

2-Allyloxy-3-methoxy-phenyl)phenylmethanol (3c)

(7.81 g, 96%) was obtained as colorless liquids, Rf= 0.27 (ethy lacetate: n-hexane = 1: 9),1H-NMR (CDCl3, 200 MHz)d 3.16 (br d, J = 4.6 Hz, 1H, OH), 3.80 (s, 3H, OCH3), 4.21 (ddt, J = 11.8, 5.8, 1.2 Hz, 1H, OCHaHbCH=CH2), 4.35 (ddt, J = 11.8, 5.8, 1.2 Hz, 1H, OCHaHbCH=CH2), 5.15 (dd, J = 10.2, 1.2 Hz, 1H, OCH2CH=CHcis-gemH), 5.22 (dd, J = 17.2, 1.2 Hz, 1H, OCH2CH=CHHtrans-gem), 5.89 (ddt, J = 17.2, 10.2, 5.8 Hz, 1H, OCH2CH=CH2), 6.03 (d, J = 4.6 Hz, 1H, ArCH(OH)Ph), 6.83 (dd, J = 7.8, 1.8 Hz, 1Hz, ArH), 6.99 (m, 2H, ArH), 7.28 (m, 5H, ArH);13 C-NMR (CDCl3, 50 MHz) d 55.63, 71.99, 73.46, 111.75, 117.50, 119.67, 123.91, 126.31, 127.01, 128.02, 133.89, 137.62, 143.74, 144.99, 152.45; EI-MS (70 eV) m/z (rel. intensity, %) 271 ([M+1]+, 3), 270 (M+, 14), 251 (18), 229 (52), 212 (39), 211 (100), 170 (23), 196 (83), 152 (18), 151 (21), 141 (49), 115 (17), 105 (30), 77 (25); HRMS calcd for C17H18O3: 270.1250. Found: 270.1253.

(2¢-Allyloxyphenyl)-(4²-methoxyphenyl)methanol (3d)

(7.77 g, 96%) was obtained as colorless liquids, Rf= 0.30 (ethyl acetate: n-hexane = 1: 6),1H-NMR (CDCl3, 400 MHz) d 3.19 (br d, J = 5.2 Hz, 1H, OH), 3.71 (s, 3H, OCH3), 4.44 (dt, J = 5.2 Hz, 1.6 Hz, 2H, OCH2CH=CHaHb), 5.18 (ddt, J = 10.4 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CCHaHb), 5.28 (ddt, J = 17.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.91 (ddt, J = 17.2 Hz, 10.4 Hz, 5.2 Hz, 1H, OCH2CH=CH2), 6.00 (d, J = 5.2 Hz, 1H, ArCH(OH)Ph), 6.80 (d, J = 8.8 Hz, 2H, ArH), 6.80 (dd, J = 7.6, 1.2 Hz, 1H, ArH), 6.92 (td, J = 7.2, 1.2 Hz, 1H, ArH), 7.18 (ddd, J = 7.6, 7.2, 1.6 Hz, 1H, ArH), 7.26 (d, J = 8.8 Hz, 2H, ArH), 7.30 (dd, J = 7.2, 1.6 Hz, 1H, ArH); 13C-NMR (CDCl3, 100 MHz) d 55.01, 68.66, 71.36, 111.74, 113.33, 117.31, 120.76, 127.32, 127.69, 128.24, 132.46, 132.84, 135.55, 155.31, 158.50; EI-MS (70 eV) m/z (rel. intensity, %) 270 (M+, 1), 230 (16), 229 ([M-41]+, 100), 224 (18), 211 (19), 168 (13), 135 (26), 122 (24), 121 (79); ESI-HRMS calcd for C17H18O3Na [M+Na]+: 293.1154. Found: 293.1155.

(2¢-Allyloxy-4¢-methoxyphenyl)-(4²-methoxyphenyl)-methanol (3e)

(8.54 g, 95%) was obtained as colorless crystal, mp 46-47°C, Rf= 0.14 (ethyl acetate: n-hexane = 1: 6),1 H-NMR (CDCl3, 400 MHz)d 2.95 (br d, J = 4.0 Hz, 1H, OH), 3.76 (s, 3H, OCH3), 3.77 (s, 3H, OCH3), 4.48 (dt, J = 5.2, 1.6 Hz, 2H, OCH2CH=CH2), 5.24 (ddt, J = 10.4, 1.6, 1.6 Hz, 1H, OCH2CH=CCHaHb), 5.31 (ddt, J = 17.2, 1.6, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.94 (ddt, J = 17.2, 10.4, 5.2 Hz, 1H, OCH2-CH=CH2), 5.86 (br d, J = 4.0 Hz, 1H, ArCH(OH)Ph), 6.43 (d, J = 2.4 Hz, 1H, ArH), 6.45 (dd, J = 8.0, 2.4 Hz, 1H, ArH), 6.84 (d, J = 8.8 Hz, 2H, ArH), 7.13 (d, J = 8.0 Hz, 1H, ArH), 7.28 (d, J = 8.8 Hz, 2H, ArH); 13 C-NMR (CDCl3, 100 MHz)d 55.16, 55.28, 68.83, 71.32, 99.82, 104.32, 113.41, 117.58, 125.23, 127.66, 128.27, 132.73, 135.77, 156.53, 158.56, 160.03; EI-MS (70 eV) m/z (rel. intensity, %) 300 (M+, 25), 259 (94), 241 (23), 198

(16), 191 (23), 164 (22), 152 (30), 151 (100), 137 (26), 135 (55); ESI-HRMS calcd for C18H20O4Na [M+Na]+: 323.1259. Found: 323.1256.

(2¢-Allyloxy-3¢-methoxyphenyl)-(4²-methoxyphenyl)-methanol (3f)

(8.36 g, 93%) was obtained as colorless liquid, Rf= 0.17 (ethyl acetate: n-hexane = 1: 6),1H-NMR (CDCl3, 400 MHz)d 3.02 (br s, 1H, OH), 3.76 (s, 3H, OCH3), 3.82 (s, 3H, OCH3), 4.27 (ddt, J = 12.0, 5.6, 1.6 Hz, 1H, OCHaHbCH=CH2), 4.33 (ddt, J = 12.0, 5.6, 1.6 Hz, 1H, OCHaHbCH=CH2), 5.16 (ddt, J = 10.4, 1.6, 1.6 Hz, 1H, OCH2CH= CHaHb), 5.25 (ddt, J = 17.2, 1.6, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.92 (ddt, J = 17.2, 10.4, 5.6 Hz, 1H, OCH2CH=CH2), 6.00 (br s, 1H, ArCH(OH)Ph), 6.83 (d, J = 8.4 Hz, 2H, ArH), 6.84 (dd, J = 8.0, 1.6 Hz, 1H, ArH), 6.96 (dd, J = 8.0, 1.6 Hz, 1H, ArH) 7.04 (t, J = 8.0 Hz, 1H, ArH), 7.27 (d, J = 8.4 Hz, 2H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.15, 55.64, 71.61, 73.46, 111.60, 113.46, 117.53, 119.44, 123.97, 127.67, 133.97, 135.97, 137.83, 144.91, 152.50, 158.66; EI-MS (70 eV) m/z (rel. intensity, %) 300 (M+, 1), 284 (14), 283 ([M-17]+, 100), 282 (8), 260 (6), 242 (6), 151 (7); ESI-HRMS calcd for C18H20O4Na [M+Na]+: 323.1259. Found: 323.1261.

(2¢-Allyloxy-3¢-methoxyphenyl)-(2²-methoxyphenyl)-methanol (3g)

(8.17 g, 91%) was obtained as colorless crystal, mp 121-122°C, Rf= 0.20 (ethyl acetate: n-hexane = 1: 6), 1

H-NMR (CDCl3, 400 MHz)d 3.22 (d, J = 4.8 Hz, 1H, OH), 3.78 (s, 3H, OCH3), 3.83 (s, 3H, OCH3), 4.07 (ddt, J = 12.4, 5.6, 1.2 Hz, 1H, OCHaHbCH=CH2), 4.50 (ddt, J = 12.4, 5.6, 1.2 Hz, 1H, OCHaHbCH=CH2), 5.16 (ddt, J = 10.4, 1.6, 1.2 Hz, 1H, OCH2CH=CHcis-gemH), 5.27 (ddt, J = 17.2, 1.6, 1.2 Hz, 1H, OCH2CH=CHHtrans-gem), 5.99 (ddt, J = 17.2, 10.4, 5.6 Hz, 1H, OCH2CH=CH2), 6.42 (d, J = 4.8 Hz, 1H, ArCH(OH)Ph), 6.83-6.93 (m, 4H, ArH), 7.02 (t, J = 7.6 Hz, 1H, ArH), 7.21-7.25 (m, 2H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.27, 55.67, 66.79, 73.59, 110.36, 111.49, 117.17, 119.64, 120.47, 123.71, 127.74, 128.42, 131.32, 134.25, 136.88, 145.24, 152.38, 156.65; EI-MS (70 eV) m/z (rel. intensity, %) 301 ([M+1]+, 3), 300 (M+, 21), 284 (17), 283 (100), 251 (5), 241 (6), 211 (9), 147 (6); ESI-HRMS calcd for C18H20O4Na [M+Na]+: 323.1259. Found: 323.1256.

General procedure for the preparation of 2-allyloxy-benzophenones (4a-g)

To (2-allyloxyphenyl)phenylmethanol (3a-g) (20 mmol) dissolved in anhydrous dichloromethane (85 mL)

was added MnO2(17.39 g, 200 mmol) and stirred at room temperature for 5 hr. After the end of reaction, the mixture was filtered, and the filtration was concentrated in vacuo. The residue which was obtained was purified from sil-ica-gel column chromatography to give pure 4a-g.

2-Allyloxybenzophenone (4a)15

(4.31 g, 90%) was obtained as colorless liquid, Rf= 0.15 (ethyl acetate: n-hexane = 1: 15),1H-NMR (CDCl3, 200 MHz)d 4.44 (dt, J = 5.2 Hz, 1.2 Hz, 2H, OCH2CH= CH2), 4.98 (ddt, J = 10.4 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH= CHaHb), 5.04 (ddt, J = 17.2 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH=CHaHb), 5.70 (ddt, J = 17.2 Hz, 10.4 Hz, 5.2 Hz, 1H, OCH2CH=CH2), 6.96 (d, J = 8.0 Hz, 1H, ArH), 7.05 (td, J = 7.6 Hz, 0.8 Hz, 1H, ArH), 7.36-7.57 (m, 5H, ArH), 7.78-7.83 (m, 2H, ArH);13C-NMR (CDCl3, 50 MHz)d 68.92, 112.76, 116.81, 120.79, 128.10, 129.22, 129.57, 129.74, 131.86, 132.32, 132.68, 138.11, 156.34, 196.50; EI-MS (70 eV) m/z (rel. intensity, %) 239 ([M+1]+, 54), 238 (M+, 21), 223 (35), 209 (45), 197 (67), 195 (35), 194 (71), 181 (76), 121 (66), 115 (45), 106 (40), 105 (100), 77 (95); HRMS calcd for C16H14O2: 238.0988. Found: 238.0990.

(2-Allyloxy-4-methoxyphenyl)phenylmethanone (4b)16

(4.86 g, 91%) was obtained as colorless liquid, Rf= 0.17 (ethyl acetate: n-hexane = 1: 19),1H-NMR (CDCl3, 200 MHz)d 3.85 (s, 3H, OCH3), 4.12 (dt, J = 5.6, 1.8 Hz, 2H, OCH2CH=CH2), 4.97 (ddt, J = 17.2, 1.8, 1.8 Hz, 1H, OCH2CH=CHaHb), 5.03 (ddt, J = 10.8, 1.8, 1.8 Hz, 1H, OCH2CH=CHaHb), 5.69 (ddt, J = 17.2, 10.8, 5 Hz, 1H, OCH2CH=CH2), 6.48 (d, J = 2.2 Hz, 1H, ArH), 6.57 (dd, J = 8.4, 2.2 Hz, 1H, ArH), 7.46 (m, 4H, ArH), 7.71 (m, 2H, ArH);13C-NMR (CDCl3, 50 MHz)d 55.45, 68.88, 99.81, 105.09, 116.85, 121.84, 127.94, 129.44, 132.08, 132.16, 132.23, 139.14, 158.48, 163.31, 195.73; EI-MS (70 eV) m/z (rel. intensity, %) 269 ([M+1]+, 56), 268 (M+, 98), 267 (28), 254 (12), 253 (60), 211 (19), 191 (15), 175 (16), 163 (23), 105 (100), 77 (22); HRMS calcd for C17H16O3: 268.1094. Found: 268.1096. (2-Allyloxy-3-methoxyphenyl)phenylmethanone (4c)

(4.81 g, 90%) was obtained as colorless liquid, Rf= 0.21 (ethyl acetate: n-hexane = 1: 19),1H-NMR (CDCl3, 200 MHz)d 3.86 (s, 3H, OCH3), 4.41 (d, J = 5.8 Hz, 2H, OCH2CH=CH2), 4.98 (dd, J = 10.2, 1.0 Hz, 1H, OCH2CH= CHaHb), 5.03 (dd, J = 17.2, 1.0 Hz, 1H, OCH2CH=CHaHb), 5.72 (ddt, J = 17.2, 10.2, 5.8 Hz, 1H, OCH2CH=CH2), 6.93 (dd, J = 2.2, 1.8 Hz, 1H, ArH), 7.03 (dd, J = 7.8, 1.8 Hz, 1H, ArH), 7.11 (t, J = 7.8 Hz, 1H, ArH), 7.46 (m, 3H, ArH),

7.81 (m, 2H, ArH);13C-NMR (CDCl3, 50 MHz)d 55.68, 74.41, 114.18, 117.06, 120.25, 123.87, 127.99, 129.58, 132.78, 133.38, 134.26, 137.51, 145.40, 152.59, 195.99; EI-MS (70 eV) m/z (rel. intensity, %) 269 ([M+1]+, 38), 268 (M+, 69), 267 (22), 253 (33), 240 (21), 239 (30), 227 (69), 225 (40), 222 (20), 213 (32), 212 (100), 184 (57), 151 (34), 105 (34), 77 (36); HRMS calcd for C17H16O3: 268.1094. Found: 268.1096. (2¢-Allyloxyphenyl)-(4²-methoxyphenyl)methanone (4d)

(5.09 g, 95%) was obtained as colorless liquid, Rf= 0.32 (ethyl acetate: n-hexane = 1: 6),1H-NMR (CDCl3, 400 MHz)d 3.83 (s, 3H, CH3), 4.47 (dt, J = 4.8 Hz, 1.6 Hz, 2H, OCH2CH=CH2), 5.07 (ddt, J = 10.8 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.08 (ddt, J = 17.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.79 (ddt, J = 17.2 Hz, 10.8 Hz, 4.8 Hz, 1H, OCH2CH=CH2), 6.89 (d, J = 8.8 Hz, 2H, ArH), 6.95 (d, J = 8.0 Hz, 1H, ArH), 7.02 (t, J = 7.6 Hz, 1H, ArH), 7.35 (dd, J = 7.6, 1.6 Hz, 1H, ArH), 7.41 (ddd, J = 8.0, 7.6, 1.6 Hz, 1H, ArH), 7.80 (d, J = 8.8 Hz, 2H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.32, 68.84, 112.65, 113.30, 116.78, 120.66, 129.27, 129.55, 130.74, 131.30, 132.04, 132.42, 155.86, 163.36, 195.01; EI-MS (70 eV) m/z (rel. intensity, %) 269 ([M+1]+, 100), 268 (M+, 8), 238 (8), 224 (16), 161 (8), 148 (19), 147 (7), 135 (31), 77 (8); ESI-HRMS calcd for C17H17O3[M+H]+: 269.1178. Found: 269.1177.

(2 ¢-Allyloxy-4¢-methoxyphenyl)-(4²-methoxyphenyl)-methanone (4e)17

(5.66 g, 95%) was obtained as colorless liquid, Rf= 0.22 (ethyl acetate: n-hexane = 1: 6),1H-NMR (CDCl3, 400 MHz)d 3.81 (s, 6H, 2 ´ OCH3), 4.42 (dt, J = 4.8, 1.6, 2H, OCH2CH=CH2), 5.03 (ddt, J = 16.8, 1.6, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.04 (ddt, J = 10.8, 1.6, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.74 (ddt, J = 16.8, 10.8, 4.8 Hz, 1H, OCH2CH=CH2), 6.47 (d, J = 2.4 Hz, 1H, ArH), 6.53 (dd, J = 8.4, 2.4 Hz, 1H, ArH), 6.87 (d, J = 8.8 Hz, 2H, ArH), 7.36 (d, J = 8.4 Hz, 1H, ArH), 7.75 (d, J = 8.8 Hz, 2H, ArH); 13 C-NMR (CDCl3, 100 MHz)d 55.27, 55.31, 68.82, 99.76, 104.87, 113.09, 116.78, 122.17, 131.51, 131.62, 131.86, 132.19, 157.86, 162.70, 162.97, 194.26; EI-MS (70 eV) m/z (rel. intensity, %) 299 ([M+1]+, 38), 298 (M+, 19), 268 (64), 254 (100), 253 (51), 241 (53), 214 (54), 211 (75), 148 (79), 135 (79); ESI-HRMS calcd for C18H19O4[M+H]+: 299.1283. Found: 299.1285.

(2 ¢-Allyloxy-3¢-methoxyphenyl)-(4²-methoxyphenyl)-methanone (4f)

(5.67 g, 95%) was obtained as colorless liquid, Rf=

0.26 (ethyl acetate: n-hexane = 1: 6),1H-NMR (CDCl3, 400 MHz)d 3.83 (s, 3H, OCH3), 3.88 (s, 3H, OCH3), 4.43 (dt, J = 6.0 Hz, 1.6 Hz, 2H, OCH2CH=CH2), 5.02 (ddt, J = 10.4 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.08 (ddt, J = 17.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.78 (ddt, J = 17.2 Hz, 10.4 Hz, 6.0 Hz, 1H, OCH2CH=CH2), 6.90 (d, J = 8.8 Hz, 2H, ArH), 6.90 (dd, J = 8.0 Hz, 1.6 Hz, 1H, ArH), 7.02 (dd, J = 8.0 Hz, 1.6 Hz, 1H, ArH), 7.12 (t, J = 8.0 Hz, 1H, ArH), 7.81 (d, J = 8.8 Hz, 2H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.29, 55.72, 74.60, 113.35, 113.73, 117.21, 120.16, 123.98, 130.38, 132.20, 133.59, 134.79, 145.14, 152.66, 163.51, 194.68; EI-MS (70 eV) m/z (rel. intensity, %) 299 ([M+1]+, 100), 298 (M+, 14), 257 (29), 242 (46), 239 (26), 214 (61), 151 (63), 135 (94), 122 (39), 77 (57); ESI-HRMS calcd for C18H18O4Na [M+Na]+: 321.1103. Found: 321.1101.

(2 ¢-Allyloxy-3¢-methoxyphenyl)-(2²-methoxyphenyl)-methanone (4g)

(5.73 g, 96%) was obtained as colorless liquid, Rf= 0.25 (ethyl acetate: n-hexane = 1: 6),1H-NMR (CDCl3, 400 MHz)d 3.68 (s, 3H, OCH3), 3.85 (s, 3H, OCH3), 4.30 (dt, J = 6, 1.6 Hz, 2H, OCH2CH=CH2), 5.00 (ddt, J = 10.4 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.04 (ddt, J = 17.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.66 (ddt, J = 17.2, 10.4, 6.0 Hz, 1H, OCH2CH=CH2), 6.91 (d, J = 8.4 Hz, 1H, ArH), 6.97 (t, J = 7.6 Hz, 1H, ArH), 7.01-7.10 (m, 3H, ArH), 7.43 (td, J = 8.4, 2, Hz, 1H, ArH), 7.50 (dd, J = 7.6, 2 Hz, 1H, ArH); 13C-NMR (CDCl3, 100 MHz) d 55.67, 55.89, 74.54, 111.57, 114.85, 117.08, 120.10, 121.13, 123.89, 129.75, 130.55, 132.84, 133.62, 135.90, 146.34, 152.67, 158.49, 195.49; EI-MS (70 eV) m/z (rel. intensity, %) 299 ([M+1]+, 42), 298 (M+, 19), 267 (38), 257 (38), 242 (56), 151 (96), 135 (100), 122 (30), 92 (34), 77 (59); ESI-HRMS calcd for C18H19O4 [M+H]+: 299.1283. Found: 299.1285.

General procedure for the preparation of 1-allyloxy-2-(phenylvinyl)benzene (5a-g)

Under the protection of dried nitrogen, to methyltri-phenylphosphonium bromide (7.15 g, 20 mmol) dissolved in anhydrous THF (50 mL) and cooled at 0°C was added potassium tert-butoxide (2.25 g, 20 mmol) in portion. The resulting mixture was stirred at 0°C for 15 min. Then, the reaction solution turned yellow and was added in drops to the solution of 2-allylbenzophenones (4a-g) (15 mmol) in THF (5 mL). The resulting solution was stirred for 3 hr at 0 °C. Finally, the solution was quenched with saturated NH4Cl aq. solution. After concentration in vacuo to remove

THF, the mixture which was obtained was extracted with EtOAc (20 mL´ 5). The organic layer was combined and washed with brine and then dried with anhydrous MgSO4. After filtration, the filtrate was concentrated in vacuo. The obtained residue was purified by silica-gel column chroma-tography (ethyl acetate: n-hexane = 1: 15) to give pure

5a-g.

1-Allyloxy-2-(phenylvinyl)benzene (5a)

(3.25 g, 92%) was obtained as colorless liquid, Rf= 0.65 (ethyl acetate: n-hexane = 1: 15),1H-NMR (CDCl3, 400 MHz)d 4.33 (dt, J = 5.2 Hz, 1.6 Hz, 2H, OCH2CH= CH2), 4.97-5.03 (m, 2H, OCH2CH=CH2), 5.33, 5.68 (each d, J = 1.6 Hz, 1H, Ar(Ph)C=CH2), 5.62 (ddt, J = 17.2 Hz, 10.4 Hz, 5.2 Hz, 1H, OCH2CH=CH2), 6.86 (dd, J = 8.0 Hz, 0.8 Hz, 1H, ArH), 6.99 (td, J = 8.0 Hz, 0.8 Hz, 1H, ArH), 7.20-7.31 (m, 7H, ArH);13C-NMR (CDCl3, 100 MHz)d 68.96, 112.79, 115.47, 116.44, 120.85, 126.43, 127.18, 127.94, 128.90, 131.30, 131.55, 132.97, 141.45, 147.33, 156.04; EI-MS (70 eV) m/z (rel. intensity, %) 237 ([M+1]+, 7), 236 (M+, 3), 221 (25), 208 (20), 207 (20), 195 (67), 168 (25), 167 (93), 166 (31), 165 (74), 152 (33), 145 (100), 115 (17); HRMS calcd for C17H16O: 236.1196. Found: 236.1198.

2-Allyloxy-4-methoxy-1-(1-phenylvinyl)benzene (5b)

(3.80 g, 95%) was obtained as colorless liquid, Rf= 0.60 (ethyl acetate: n-hexane = 1: 19),1H-NMR (CDCl3, 400 MHz)d 3.79 (s, 3H, OCH3), 4.30 (dt, J = 4.8, 1.6 Hz, 1H, OCH2CH=CH2), 4.98 (ddt, J = 18.0 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 4.99 (ddt, J = 11.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.30, 5.60 (each d, J = 1.6 Hz, 1H, Ar(Ph)C=CH2), 5.60 (ddt, J = 18.0 Hz, 11.2 Hz, 4.8 Hz, 1H, OCH2CH=CH2), 6.45 (d, J = 2.4 Hz, 1H, ArH), 6.51 (dd, J = 8.4 Hz, 2.4 Hz, 1H, ArH), 7.25 (m, 6H, ArH); 13 C-NMR (CDCl3, 50 MHz) d 55.26, 68.83, 100.27, 104.57, 115.05, 116.45, 124.16, 126.47, 127.07, 127.86, 131.68, 132.73, 141.81, 146.97, 156.96, 160.48; EI-MS (70 eV) m/z (rel. intensity, %) 267 ([M+1]+, 33), 266 (M+, 99), 265 (100), 252 (12), 251 (46), 238 (14), 237 (27), 236 (71), 235 (16), 225 (12), 223 (10), 197 (20), 165 (11); HRMS calcd for C18H18O2: 266.1307. Found: 266.1305.

2-Allyloxy-1-methoxy-3-(1-phenylvinyl)benzene (5c)

(3.84 g, 96%) was obtained as colorless liquid, Rf= 0.44 (ethyl acetate: n-hexane = 1: 19),1H-NMR (CDCl3, 400 MHz)d 3.83 (s, 3H, OCH3), 4.21 (dt, J = 5.6, 1.6 Hz, 1H, OCH2CH=CH2), 4.97 (ddt, J = 10.4 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH=CHaHb), 5.02 (ddt, J = 17.2 Hz, 1.2 Hz, 1.2 Hz, 1H, OCH2CH=CHaHb), 5.32, 5.67 (each d, J = 1.6 Hz, 1H, Ar(Ph)C=CH2), 5.66 (ddt, J = 17.2 Hz, 10.4 Hz, 5.6 Hz, 1H, OCH2CH=CH2), 6.86 (dd, J = 7.6 Hz, 1.6 Hz, 1H, ArH), 6.90 (dd, J = 8.4 Hz, 1.6 Hz, 1H, ArH), 7.04 (dd, J = 8.4 Hz, 7.6 Hz, 1H, ArH), 7.27 (m, 5H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.68, 73.54, 111.83, 115.69, 116.77, 122.99, 123.65, 126.60, 127.29, 127.96, 134.15, 136.51, 141.33, 145.46, 146.81, 152.91; EI-MS (70 eV) m/z (rel. intensity, %) 267 ([M+1]+, 1), 266 (M+, 4), 265 (4), 251 (10), 248 (12), 238 (12), 235 (12), 226 (17), 225 (100), 219 (21), 198 (13), 197 (43), 183 (13), 182 (34), 181 (18), 169 (13), 166 (25), 165 (44), 154 (21), 153 (26), 152 (20), 145 (22); HRMS calcd for C18H18O2: 266.1301. Found: 266.1304.

1-(Allyloxy)-2-[1-(4-methoxyphenyl)vinyl]benzene (5d)

(3.83 g, 96%) was obtained as colorless crystal, mp 41-42°C, Rf= 0.59 (ethyl acetate: n-hexane = 1: 9),1 H-NMR (CDCl3, 400 MHz)d 3.77 (s, 3H, OCH3), 4.35 (dt, J = 4.8 Hz, 1.6 Hz, 2H, OCH2CH=CH2), 5.02 (ddt, J = 10.4 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.05 (ddt, J = 17.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.22, 5.60 (each d, J = 1.6 Hz, 1H, Ar(Ph)C=CH2), 5.67 (ddt, J = 17.2 Hz, 10.4 Hz, 4.8 Hz, 1H, OCH2CH=CH2), 6.79 (d, J = 8.8 Hz, 2H, ArH), 6.87 (d, J = 7.6 Hz, 1H, ArH), 6.97 (t, J = 7.6 Hz Hz, 1H, ArH), 7.23 (d, J = 8.8 Hz, 2H, ArH), 7.20-7.30 (m, 2H, ArH); 13C-NMR (CDCl3, 100 MHz) d 55.18, 68.93, 112.78, 113.29, 113.74, 116.43, 120.81, 127.54, 128.77, 131.24, 131.74, 133.04, 133.97, 146.55, 155.99, 158.96; EI-MS (70 eV) m/z (rel. intensity, %) 267 ([M+1]+, 31), 266 (M+, 26), 251 (14), 238 (15), 237 (21), 225 (15), 197 (29), 176 (19), 175 (100), 147 (37). HRMS calcd for C18H18O2: 266.1307. Found: 266.1306.

2-Allyloxy-4-methoxy-1-[1-(4-methoxyphenyl)vinyl]-benzene (5e)

(4.36 g, 98%) was obtained as colorless liquid, Rf= 0.57 (ethylacetate: n-hexane = 1: 9),1H-NMR (CDCl3, 400 MHz)d 3.79 (s, 3H, OCH3), 3.82 (s, 3H, OCH3), 4.35 (dt, J = 4.8 Hz, 2.0 Hz, 1H, OCH2CH=CH2), 5.04 (ddt, J =10.4 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.04 (ddt, J = 17.6 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.20, 5.54 (each d, J = 1.6 Hz, 1H, Ar(Ph)C=CH2), 5.63 (ddt, J = 17.6, 10.4, 4.8 Hz, 1H, OCH2CH=CH2), 6.46 (d, J = 2.4 Hz, 1H, ArH), 6.52 (dd, J = 8.0, 2.4 Hz, 1H, ArH), 6.80 (d, J = 8.8 Hz, 2H, ArH), 7.18 (d, J = 8.0 Hz, 1H, ArH), 7.24 (d, J = 8.8 Hz, 2H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.24, 55.32, 68.95, 100.38, 104.59, 113.26, 113.46, 116.54,

124.45, 127.63, 131.67, 132.89, 134.41, 146.23, 156.99, 158.92, 160.39; EI-MS (70 eV) m/z (rel. intensity, %) 297 ([M+1]+, 22), 296 (M+, 45), 281 (47), 267 (38), 266 (100), 253 (21), 227 (55), 212 (24), 175 (28), 169 (23); ESI-HRMS calcd for C19H21O3[M+H]+: 297.1491. Found: 297.1489.

2-Allyloxy-3-methoxy-1-[1-(4-methoxyphenyl)vinyl]-benzene (5f)

(4.27 g, 96%) was obtained as colorless liquid, Rf= 0.46 (ethyl acetate: n-hexane = 1: 9),1H-NMR (CDCl3, 400 MHz)d 3.77 (s, 3H, OCH3), 3.83 (s, 3H, OCH3), 4.24 (dt, J = 5.6 Hz, 1.6 Hz, 1H, OCH2CH=CH2), 4.99 (ddt, J = 10.4 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.06 (ddt, J = 17.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.21, 5.60 (each d, J = 1.6 Hz, 1H, Ar(Ph)C=CH2), 5.72 (ddt, J = 17.2 Hz, 10.4 Hz, 6.0 Hz, 1H, OCH2CH=CH2), 6.80 (d, J = 8.8 Hz, 2H, ArH), 6.85 (dd, J = 8.0 Hz, 1.6 Hz, 1H, ArH), 6.89 (dd, J = 8.4 Hz, 1.6 Hz, 1H, ArH), 7.04 (dd, J = 8.0 Hz, 1H, ArH), 7.24 (d, J = 8.8 Hz, 2H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.14, 55.71, 73.63, 111.73, 113.33, 113.90, 116.72, 122.97, 123.62, 127.74, 133.88, 134.27, 136.76, 145.52, 146.10, 152.92, 159.04; EI-MS (70 eV) m/z (rel. intensity, %) 297 ([M+1]+, 44), 296 (M+, 100), 295 (52), 282 (17), 281 (49), 267 (17), 266 (38), 265 (54), 255 (18), 175 (21); ESI-HRMS calcd for C19H20O3Na [M+Na]+: 319.1310. Found: 319.1307.

2-Allyloxy-1-methoxy-3-[1-(2-methoxy-phenyl)vinyl]-benzene (5g)

(4.31 g, 97%) was obtained as colorless liquid, Rf= 0.52 (ethyl acetate: n-hexane = 1: 9),1H-NMR (CDCl3, 400 MHz)d 3.62 (s, 3H, OCH3), 3.81 (s, 3H, OCH3), 4.22 (dt, J = 5.6 Hz, 1.6 Hz, 1H, OCH2CH=CH2), 5.04 (ddt, J = 10.4 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.12 (ddt, J = 17.2 Hz, 1.6 Hz, 1.6 Hz, 1H, OCH2CH=CHaHb), 5.59, 5.62 (each d, J = 2.0 Hz, 1H, Ar(Ph)C=CH2), 5.80 (ddt, J = 17.2 Hz, 10.4 Hz, 6.0 Hz, 1H, OCH2CH=CH2), 6.80-6.84 (m, 2H, ArH), 6.81 (d, J = 7.2 Hz, 1H, ArH), 6.89 (td, J = 7.2 Hz, 0.8 Hz, 1H, ArH), 6.96 (dd, J = 8.4 Hz, 7.2 Hz, 1H, ArH), 7.21 (d, J = 7.2 Hz, 1H, ArH), 7.22 (td, J = 7.2 Hz, 1.6 Hz, 1H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.37, 55.73, 73.14, 111.21, 111.22, 116.47, 119.31, 120.33, 122.23, 123.31, 128.33, 130.39, 131.74, 134.58, 137.31, 143.82, 145.14, 152.79, 156.81; EI-MS (70 eV) m/z (rel. intensity, %) 297 ([M+1]+, 1), 296 (M+, 3), 265 (21), 256 (18), 255 (100), 225 (14), 175 (27), 152 (12), 122 (24), 121 (70); ESI-HRMS calcd for C19H20O3Na [M+Na]+: 319.1310.

Found: 319.1307.

General procedure for the preparation of neoflavenes (6a-g)

To 1-allyloxy-2-(arylvinyl)benzenes (5a-g) (5 mmol) dissolved in dichloromethane (100 mL) was added Grubbs’ catalyst (5% mol), and the reaction mixture was stirred at room temperature for 4 hr. Then, the mixture was concen-trated in vacuo to remove the solvent. The residue was puri-fied by silica gel column chromatography (ethyl acetate: n-hexane = 1: 15) to give pure 6a-g.

Neoflavene (4-Phenyl-2H-chromene) (6a)18

(0.95 g, 91%) was obtained as colorless liquid, Rf= 0.62 (ethyl acetate: n-hexane = 1: 15),1H-NMR (CDCl3, 400 MHz)d 4.86 (d, J = 4.0 Hz, 2H, H-2), 5.80 (t, J = 4.0 Hz, 1H, H-3), 6.84 (td, J = 8.0 Hz, 1.2 Hz, 1H, ArH), 6.90 (dd, J = 8.0 Hz, 1.2 Hz, 1H, ArH), 7.00 (dd, J = 8.0 Hz, 1.6 Hz, 1H, ArH), 7.15 (td, J = 8.0 Hz, 1.6 Hz, 1H, ArH ), 7.37 (m, 5H, ArH); 13C-NMR (CDCl3, 100 MHz) d 65.24, 116.16, 119.89, 121.12, 125.80, 127.74, 128.33, 128.58, 129.19, 130.03, 137.11, 154.68, 186.22; EI-MS (70 eV) m/z (rel. intensity, %) 208 (M+, 75), 207 (100), 179 (21), 178 (32), 152 (15), 132 (11), 131 (33); HRMS calcd for C15H12O1: 208.0888. Found: 208.0886. 7-Methoxyneoflavene (7-Methoxy-4-phenyl-2 H-chromene) (6b)19

(1.07 g, 90%) was obtained as colorless liquid, Rf= 0.61 (ethyl acetate: n-hexane = 1: 19),1H-NMR (CDCl3, 400 MHz)d 3.76 (s, 3H, OCH3), 4.81 (d, J = 4.0 Hz, 2H, H-2), 5.63 (t, J = 4.0 Hz, 1H, H-3), 6.40 (dd, J = 8.4 Hz, 2.4, 1H, ArH), 6.48 (d, J = 2.4 Hz, 1H, ArH), 6.92 (d, J = 8.4 Hz, 1H, ArH), 7.34 (m, 5H, ArH);13C-NMR (CDCl3, 100 MHz) d 55.26, 65.46, 101.88, 106.81, 116.81, 116.90, 126.63, 127.65, 128.28, 128.50, 136.93, 138.43, 156.01, 160.52; EI-MS (70 eV) m/z (rel. intensity, %) 239 ([M+1]+, 16), 238 (M+, 96), 237 (100), 223 (32), 194 (22), 165 (17), 161 (26); HRMS calcd for C16H14O2: 238.0994. Found: 238.0991.

8-Methoxyneoflavene (8-Methoxy-4-phenyl-2 H-chromene) (6c)

(1.10 g, 92%) was obtained as colorless crystal, mp 66-68°C (n-hexane + ethyl acetate) [lit.2070-71°C], Rf= 0.24 (ethyl acetate: n-hexane = 1: 19),1H-NMR (CDCl3, 400 MHz)d 3.92 (s, 3H, OCH3), 4.92 (d, J = 4.0 Hz, 2H, H-2), 5.83 (t, J = 4.0 Hz, 1H, H-3), 6.66 (dd, J = 7.2 Hz, 2.0 Hz, 1H, ArH), 6.83 (m, 2H, ArH), 7.35-7.42 (m, 5H, ArH); 13

118.20, 119.89, 120.45, 124.35, 127.66, 128.21, 128.52, 137.08, 138.28, 143.53, 148.00; EI-MS (70 eV) m/z (rel. intensity, %) 239 ([M+1]+, 17), 238 (M+, 100), 237 (57), 223 (20), 207 (17), 195 (17), 167 (16), 165 (28), 161 (20); HRMS calcd for C16H14O2: 238.0988. Found: 238.0991.

4¢-Methoxyneoflavene (4-(4-Methoxyphenyl)-2H-chromene) (6d)

(1.09 g, 92%) was obtained as colorless crystal, mp 93-94°C (n-hexane + ethyl acetate) [lit.389-92°C], Rf= 0.58 (ethyl acetate: n-hexane = 1: 9),1H-NMR (CDCl3, 400 MHz)d 3.84 (s, 3H, OCH3), 4.82 (d, J = 4.0 Hz, 2H, H-2), 5.75 (t, J = 4.0 Hz, 1H, H-3), 6.85 (td, J = 7.6 Hz, 1.2 Hz, 1H, ArH), 6.89 (dd, J = 8.0 Hz, 1.2 Hz, 1H, ArH), 6.93 (d, J = 8.8 Hz, 2H, ArH), 7.02 (dd, J = 7.6 Hz, 1.6 Hz, 1H, ArH), 7.15 (ddd, J = 8.0 Hz, 7.6 Hz, 1.6 Hz, 1H, ArH), 7.27 (d, J = 8.8 Hz, 2H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.28, 65.21, 113.73, 116.15, 119.17, 121.10, 123.90, 125.82, 129.11, 129.72, 130.59, 136.61, 154.78, 159.25; EI-MS (70 eV) m/z (rel. intensity, %) 239 ([M+1]+, 16), 238 (100), 237 (66), 223 (31), 207 (39), 195 (20), 194 (18), 167 (16), 165 (35), 152 (14). HRMS calcd for C16H14O2: 238.0994. Found: 238.0996.

7-Methoxyneoflavene (7-Methoxy-4-(4-methoxy-phenyl)-2H-chromene) (6e)

(1.25 g, 93%) was obtained as colorless crystal, mp 102-104°C (n-hexane + ethyl acetate) [lit.3101-103°C], Rf = 0.58 (ethyl acetate: n-hexane = 1: 9),1H-NMR (CDCl3, 200 MHz)d 3.79 (s, 3H, OCH3), 3.85 (s, 3H, OCH3), 4.82 (d, J = 4.0 Hz, 2H, H-2), 5.62 (t, J = 4.0 Hz, 1H, H-3), 6.42 (dd, J = 8.4 Hz, 2.6 Hz, 1H, ArH), 6.49 (d, J = 2.6 Hz, 1H, ArH), 6.92 (d, J = 8.8 Hz, 2H, ArH), 6.96 (d, J = 8.4 Hz, 1H, ArH), 7.27 (d, J = 8.8 Hz, 2H, ArH);13C-NMR (CDCl3, 50 MHz)d 55.27, 55.33, 65.53, 101.92, 106.85, 113.74, 116.19, 117.13, 126.69, 129.68, 130.88, 136.53, 156.15, 159.26, 160.53; EI-MS (70 eV) m/z (rel. intensity, %) 269 ([M+1]+, 18), 268 (M+, 100), 267 (74), 253 (32), 237 (17), 225 (15), 165 (22), 161 (16), 153 (19), 152 (19). HRMS calcd for C17H16O3: 268.1099. Found: 268.1099.

8-Methoxy-4¢-methoxyneoflavene (8-Methoxy-4-(2-methoxy-phenyl)-2H-chromene) (6f)

(1.21 g, 90%) was obtained as colorless crystal, mp 68-69°C (n-hexane + ethyl acetate), Rf= 0.26 (ethyl ace-tate: n-hexane = 1: 9),1H-NMR (CDCl3, 400 MHz)d 3.80 (s, 3H, OCH3), 3.87 (s, 3H, OCH3), 4.85 (d, J = 4.0 Hz, 2H, H-2), 5.75 (t, J = 4.0 Hz, 1H, H-3), 6.65 (dd, J = 6.8 Hz, 2.4 Hz, 1H, ArH), 6.76-6.82 (m, 2H, ArH), 6.89 (d, J = 8.8 Hz, 1H, ArH), 7.24 (d, J = 8.8 Hz, 1H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.03, 55.85, 65.24, 111.82, 113.51, 118.12, 119.02, 120.32, 124.51, 129.55, 130.53, 136.50, 143.55, 147.91, 159.09; EI-MS (70 eV) m/z (rel. intensity, %) 269 ([M+1]+, 19), 268 (M+, 100), 267 (33), 253 (45), 238 (12), 237 (17), 235 (12), 225 (14), 210 (13) , 165 (16); ESI-HRMS calcd for C17H17O3[M+H]+: 269.1178. Found: 269.1177.

8-Methoxy-2¢-methoxyneoflavene (8-Methoxy-4-(2-methoxyphenyl)-2H-chromene) (6g)

(1.21 g, 90%) was obtained as colorless crystal, mp 123-124°C (n-hexane + ethyl acetate), Rf= 0.30 (ethyl ace-tate: n-hexane = 1: 9),1H-NMR (CDCl3, 400 MHz)d 3.70 (s, 3H, OCH3), 3.87 (s, 3H, OCH3), 4.96 (d, J = 4.0 Hz, 2H, H-2), 5.75 (t, J = 4.0 Hz, 1H, H-3), 6.34 (dd, J = 7.6 Hz, 1.6 Hz, 1H, ArH), 6.71 (t, J = 7.6 Hz, 1H, ArH), 6.77 (dd, J = 8.0 Hz, 1.6 Hz, 1H, ArH), 6.93 (d, J = 8.0 Hz, 1H, ArH), 6.97 (t, J = 7.6 Hz, 1H, ArH), 7.17 (dd, J = 7.6 Hz, 1.6 Hz, 1H, ArH), 7.33 (td, J = 8.0 Hz, 1.6 Hz, 1H, ArH);13C-NMR (CDCl3, 100 MHz)d 55.38, 55.93, 65.61, 110.81, 111.62, 117.97, 120.19, 120.52, 121.00, 124.35, 127.28, 129.13, 130.84, 134.07, 142.71, 147.74, 157.08; EI-MS (70 eV) m/z (rel. intensity, %) 269 ([M+1]+, 18), 268 (M+, 100), 267 (11), 254 (11), 253 (43), 238 (18), 237 (48), 221 (9), 206 (9), 165 (13); ESI-HRMS calcd for C17H16O3Na [M+Na]+: 291.0997. Found: 291.1000.

Cytotoxic assays

The cytotoxic potential of all synthesized neoflavenes was evaluated against a panel of human cancer cell lines us-ing an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenylte-trazolium bromide) assay.21Cancer cells were treated as in-dicated for 48 hr in medium containing 10% FBS. Then, 20 ml MTT (2 mg/mL) was added to the cultures and incubated during the final 1.5 hr. The resultant tetrazolium salt was then dissolved by the addition of dimethyl sulfoxide. Color was measured spectrophotometrically in a microtitter plate reader at 570 nm and used as a relative measure of viable cell number. The number of viable cells following treat-ment was compared to solvent and untreated control cells and used to determine the percent of control growth as (Abtreaded/Abcontrol)´ 100, where Ab represents the mean absorbance (n = 6). The concentration that killed 50% of cells (IC50) was determined from the linear portion of the curve by calculating the concentration of agent that re-duced absorbance in treated cells, compared to control cells, by 50%.

ACKNOWLEDGEMENT

We are grateful to NSC Taiwan for financial support.

Received February 19, 2008.

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