Synthesis of spinochalcone B and analogues

Article abstract of DOI:10.1080/00397910600634316

An efficient synthesis of spinochalcone B and its analogues is achieved from readily available 2H-pyran. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600634316

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Synthesis of Spinochalcone B and Analogues
Yong Rok Lee a , Xue Wang a & Byung So Kim b
a School of Chemical Engineering and Technology, Yeungnam University ,
Gyeongsan, Korea
b Division of Chemical Industry , Yeungnam College of Science and
Technology , Daegu, Korea
Published online: 20 Aug 2006.
To cite this article: Yong Rok Lee , Xue Wang & Byung So Kim (2006) Synthesis of Spinochalcone B and
Analogues, Synthetic Communications: An International Journal for Rapid Communication of Synthetic Organic
Chemistry, 36:14, 2017-2025
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Synthetic Communicationsw, 36: 2017–2025, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600634316
Synthesis of Spinochalcone B and Analogues
Yong Rok Lee and Xue Wang
School of Chemical Engineering and Technology, Yeungnam University,
Gyeongsan, Korea
Byung So Kim
Division of Chemical Industry, Yeungnam College of Science and
Technology, Daegu, Korea
Abstract: An efficient synthesis of spinochalcone B and its analogues is achieved from
readily available 2H-pyran.
Keywords: Aldol reaction, benzopyran, spinochalcone B
There are many compounds containing a benzopyran moiety (chromenes) that
are widely distributed in nature.[1] They have shown several biological prop-
erties such as antitumor, insecticide, antifungal, antimalarial, and antioxidant
activities.[2] They are also used as versatile intermediates in organic and
natural product synthesis.[3] We are currently interested in the synthesis of
natural products with benzopyran skeletons.[4] Recently, we reported a
simple and convenient methodology for the preparation of 2H-pyrans
utilizing Knoevenagel-electrocyclic reactions (Scheme 1).[5]
As an application of this methodology, we report herein on the synthesis
of spinochalcone B (1) and its analogues 2–6 (Fig. 1). Spinochalcone B (1)
was isolated from the roots of Tephrosia spinos (Fig. 1).[6] Although there
are currently a number of methods available to synthesize benzopyrans, no
synthetic approaches to 1–6 have been reported.
Received in Japan October 20, 2005
Address correspondence to Yong Rok Lee, School of Chemical Engineering and
Technology, Yeungnam University, Gyeongsan 712-749, Korea. Tel.: 82-53-810-
2529; Fax: 82-53-810-4631; E-mail: yrlee@yu.ac.kr
2017

2018
Y. R. Lee, X. Wang, and B. S. Kim
Scheme 1.
Our retrosynthetic strategy was depicted in Scheme 2. Spinochalcone
B (1) and its analogues 2–6 could be prepared from benzopyran 7 by an
aldol reaction. The compound 7 could be prepared by first acylation and
then aromatization from 2H-pyran 8.
Based on the methodology developed by our group, starting material 8 was
readily prepared from 1,3-cyclohexanedione and citral in the presence of
10 mol% of ethylenediamine diacetate in a 67% yield.[5a] To synthesize
compound 7, base-catalyzed reactions of 8 with ethyl acetate were first
attempted. Reactions of 8 with ethyl acetate in the presence of a base such as
sodium hydride (NaH), lithium diisopropylamide (LDA), or lithium hexamethyl-
disilazide (LiHMDS) gave no expected products. Fortunately, reaction of 2 with
ethyl cyanoformate using LDA at 2788C for 6 h gave b-keto ester 9 in a 70%
yield.[7] Oxidation of 9 with DDQ in refluxing dioxane for 2 h afforded the
aromatic compound 10 in a 49% yield.[8] To introduce the chalcone moiety, the
ester 10 was saponified using 2.5 M aqueous NaOH in methanol to give 11 in a
98% yield. Treatment of 11 with excess methyl lithium (4 equiv) at 608C for
4 h in toluene gave 7 in a 75% yield.[9] To complete the total synthesis, the
aldol reaction was next attempted. Reaction of 7 with benzaldehyde in methanolic
KOH at 608C for 24 h afforded 1 in an 86% yield. The spectroscopic data of our
synthetic material were in agreement with those reported for the natural product.[6]
Next, the synthesis of analogues of 1 was achieved from 7 by aldol
reaction as shown in Scheme 3. Reaction of 7 with p-tolualdehye in methano-
lic KOH at 608C for 48 h gave 2 in a 46% yield. Similarly, treatment of
Figure 1. Spinochalcorie B and its derivatives.

Synthesis of Spinochalcone B and Analogues
2019
Scheme 2.
7 with other aldehydes such as 4-methoxybenzaldehyde, m-tolualdehyde,
3-methoxybenzaldehyde, and 2,4-dimethylbenzaldehyde afforded products
3–6 in 49, 45, 40, and 53% yields, respectively.
In conclusion, a new route to biologically interesting spinochalcone B (1)
and its derivatives 2–6 has been developed from readily available 2H-pyran 8.
Scheme 3.

2020
Y. R. Lee, X. Wang, and B. S. Kim
The overall yield of 1 was 22% in five steps, and that of 2–6 was 12, 12, 11,
10, and 13% in five steps, respectively.
EXPERIMENTAL
All experiments were carried out under a nitrogen atmosphere. Merck
precoated silica-gel plates (Art. 5554) with fluorescent indicator were used
for analytical TLC. Flash-column chromatography was performed using
silica gel 9385 (Merck). Melting points were determined in capillary tubes
on a Fisher-Johns apparatus and are uncorrected. 1H NMR spectra were
recorded on a Bruker model ARX (300-MHz) spectrometer in CDCl3 using
7.26 ppm as the solvent chemical shift. 13C NMR spectra were recorded on
a Bruker model ARX (75-MHz) spectrometer in CDCl3 using 77.0 ppm as
the solvent chemical shift. IR spectra were recorded on a Jasco FTIR 5300
spectrophotometer. HRMS mass spectra were carried out on JEOL JMS-700
spectrometer by Korea Basic Science Institute.
2-Methyl-2-(4-methylpen-3-enyl)-5-oxo-2,6,7,8-tetrahydro-
2H-chromene-6-carboxylic Acid Ethyl Ester (9)
A solution of n-BuLi (2.5 M, 1.8 mL, 4.50 mmol) in hexane at 2788C wad
addred to a stirred solution of diisopropylamine (0.492 g, 4.87 mmol) in
30 mL of dry THF. After stirring at the same temperature for 30 min,
compound 8 (1.0 g, 4.06 mmol) in THF (2 mL) were added through a
cannula. After 1 h, ethyl cyanoformate (0.805 g, 8.12 mmol) in THF (1 mL)
was added. The reaction mixture was stirred at the same temperature for
5 h, then warmed to room temperature and quenched by addition of aqueous
NH4Cl solution. The mixture was extracted with ethyl acetate (3 ꢀ 50 mL).
The combined organic layers were washed with brine, dried over MgSO4,
and evaporated under reduced pressure. The residue was purified by flash-
1
column chromatography on silica gel to give 9 (0.905 g, 70%). H NMR
(300 MHz, CDCl3) d 6.42 (1H, d, J ¼ 10.1 Hz), 5.19 (1H, d, J ¼ 10.1 Hz),
5.07–5.03 (1H, m), 4.25–4.17 (2H, m), 3.39–3.31 (1H, m), 2.56–1.97 (7H,
m), 1.75–1.68 (1H, m), 1.65 (3H, s), 1.55 (3H, s), 1.35 (3H, s), 1.26 (3H, t,
J ¼ 7.0 Hz); IR (neat) 2970, 2928, 1738, 1654, 1593, 1414, 1366, 1351,
1327, 1305, 1263, 1211, 1161, 1071, 1019, 901 cm21; HRMS: m/z (Mþ)
calcd. for C19H26O4: 318.1831; found: 318.1832.
5-Hydroxy-2-methyl-2-(4-methylpen-3-enyl)-2H-chromeme-
6-carboxylic Acid Ethyl Ester (10)
A mixture of 9 (0.80 g, 2.51 mmol) and DDQ (1.141 g, 5.03 mmol) in dioxane
(30 mL) was heated under reflux for 2 h. The resulting mixture was cooled in

Synthesis of Spinochalcone B and Analogues
2021
an ice bath and solids were removed by filtration through Celite. The filtrate
was evaporated under reduced pressure and purified by flash-column chrom-
atography on silica gel to give 10 (0.390 g, 49%). 1H NMR (300 MHz,
CDCl3) d 11.2 (1H, s), 7.59 (1H, d, J ¼ 8.8 Hz), 6.72 (1H, d, J ¼ 10.0 Hz),
6.29 (1H, d, J ¼ 8.8 Hz), 5.49 (1H, d, J ¼ 10.0 Hz), 5.08–5.03 (1H, m),
4.32 (2H, q, J ¼ 7.1 Hz), 2.11–2.03 (2H, m), 1.80–1.57 (2H, m), 1.63 (3H,
s), 1.54 (3H, s), 1.38 (3H, s), 1.33 (3H, t, J ¼ 7.1 Hz); 13C NMR (75 MHz,
CDCl3) d 170.7, 159.6, 158.6, 132.2, 130.8, 127.5, 124.2, 116.9, 109.3,
108.6, 105.8, 80.1, 61.4, 41.9, 27.3, 26.1, 23.0, 18.0, 14.7; IR (neat) 2924,
2854, 1747, 1666, 1620, 1458, 1373, 1332, 1267, 1089, 765 cm21; HRMS:
m/z (Mþ) calcd. for C19H24O4: 316.1675; found: 316.1673.
5-Hydroxy-2-methyl-2-(4-methylpent-3-enyl)-2H-chromene-
6-carboxylic Acid (11)
An aqueous solution of sodium hydroxide (2.5 M, 3.7 mL, 9.20 mmol) was
added to a solution of the ester 10 (0.30 g, 0.92 mmol) in methanol (5 mL)
at room temperature. The reaction mixture was then heated at reflux for
12 h. After cooling, methanol was evaporated under reduced pressure, and
water (10 mL) was added. The resultant solution was acidified with 2 N-HCl
to pH ꢀ2 and extracted with ethyl acetate (3 ꢀ 20 mL). The combined
organic extracts were washed with brine, dried over MgSO4, and concentrated
in vacuo. The dark brown crude product was purified by flash column chrom-
1
atography to afford 11 (0.260 g, 98%). Mp 83–848C; H NMR (300 MHz,
CDCl3) d 10.9 (1H, s), 7.64 (1H, d, J ¼ 8.8 Hz), 6.72 (1H, d, J ¼ 10.1 Hz),
6.33 (1H, d, J ¼ 8.8 Hz), 5.51 (1H, d, J ¼ 10.1 Hz), 5.08–5.04 (1H, m),
2.11–2.04 (2H, m), 1.80–1.60 (2H, m), 1.64 (3H, s), 1.55 (3H, s), 1.40
(3H, s); IR (KBr) 3200–2400, 1657, 1464, 1379, 1343, 1271, 1179, 1105,
1086, 1065, 904, 821, 797 cm21; HRMS: m/z (Mþ) calcd. for C17H20O4:
288.1362; found: 288.1365.
1-[5-Hydroxy-2-methyl-2-(4-methylpen-3-enyl)-2H-chromen-
6-yl]ethanone (7)
MeLi (1.6 M, 2.0 mL, 3.12 mmol) was added to a solution of the ester 11
(0.22 g, 0.78 mmol) in toluene (5 mL) at room temperature. The reaction
mixture was then heated at 608C for 4 h. After cooling, water (10 mL) was
added. The solution was acidified with 2 N-HCl and was stirred for 30 min.
The resultant was extracted with ethyl acetate (3 ꢀ 20 mL). The combined
organic extracts were washed with brine, dried over MgSO4, and concentrated
in vacuo. The crude product was purified by flash-column chromatography to
afford 7 (0.169, 75%). 1H NMR (300 MHz, CDCl3) d 12.8 (1H, s), 7.49 (1H, d,
J ¼ 8.8 Hz), 6.72 (1H, d, J ¼ 10.0 Hz), 6.30 (1H, d, J ¼ 8.8 Hz), 5.50 (1H, d,

2022
Y. R. Lee, X. Wang, and B. S. Kim
J ¼ 10.1 Hz), 5.09–5.03 (1H, m), 2.53 (3H, s), 2.11–2.03 (2H, m), 1.82–1.62
(2H, m), 1.63 (3H, s), 1.54 (3H, s), 1.39 (3H, s); 13C NMR (75 MHz, CDCl3) d
203.0, 160.4, 159.9, 132.1, 127.4, 124.2, 116.7, 114.1, 109.3, 108.5, 80.5,
42.0, 27.5, 26.5, 26.1, 23.1, 18.0; IR (neat) 2970, 2926, 1622, 1487, 1427,
1389, 1368, 1273, 1188, 1123, 1088, 976, 909, 804 cm21; HRMS: m/z
(Mþ) calcd. for C18H22O3: 286.1569; found: 286.1567.
Spinochalcone B (1)
Potassium hydroxide (0.236 g, 4.20 mmol) and benzaldehyde (0.067 g,
0.63 mmol) were added to a solution of 7 (0.12 g, 0.42 mmol) in methanol
(10 mL) and water (2 mL) at room temperature. The reaction mixture was
stirred at 608C for 24 h. Methanol was evaporated under reduced pressure,
and 2 N-HCl solution (20 mL) was added. Extraction with ethyl acetate
(3 ꢀ 50 mL), washing with brine, drying over MgSO4, and removal of the
solvent followed by flash-column chromatography on silica gel gave 1
1
(0.135 g, 86%). Mp 116–1178C; H NMR (300 MHz, CDCl3) d 13.67 (1H,
s), 7.86 (1H, d, J ¼ 15.5 Hz), 7.70 (1H, d, J ¼ 8.9 Hz), 7.64–7.62 (2H, m),
7.55 (1H, d, J ¼ 15.5 Hz), 7.42–7.39 (3H, m), 6.77 (1H, d, J ¼ 10.0 Hz),
6.35 (1H, d, J ¼ 8.9 Hz), 5.52 (1H, d, J ¼ 10.1 Hz), 5.10–5.04 (1H, m),
2.13–2.05 (2H, m), 1.83–1.62 (2H, m), 1.63 (3H, s), 1.55 (3H, s), 1.42
(3H, s); 13C NMR (75 MHz, CDCl3) d 192.3, 161.4, 160.7, 144.6, 135.2,
132.4, 131.2, 131.0, 129.4, 128.9, 127.4, 124.2, 120.7, 116.8, 114.4, 109.6,
108.6, 80.8, 42.1, 27.6, 26.1, 23.1, 18.1; IR (KBr) 2970, 2924, 1640, 1586,
1485, 1451, 1426, 1358, 1283, 1227, 1184, 1113, 1047, 978, 908, 862,
760 cm21; HRMS: m/z (Mþ) calcd. for C25H26O3: 374.1882; found:
374.1884.
Compound (2)
Potassium hydroxide (0.196 g, 3.50 mmol) and p-tolualdehyde (0.063 g,
0.53 mmol) were added to a solution of 7 (0.10 g, 0.35 mmol) in methanol
(10 mL) and water (2 mL) at room temperature. The reaction mixture was
stirred at 608C for 48 h. Methanol was evaporated under reduced pressure
and 2 N-HCl solution (20 mL) was added. Extraction with ethyl acetate
(3 ꢀ 50 mL), washing with brine, drying over MgSO4, and removal of the
solvent followed by flash-column chromatography on silica gel gave 2
1
(0.063 g, 46%). H NMR (300 MHz, CDCl3) d 13.65 (1H, s), 7.83 (1H, d,
J ¼ 15.4 Hz), 7.69 (1H, d, J ¼ 8.8 Hz), 7.64–7.62 (2H, m), 7.53–7.41 (3H,
m), 7.20 (2H, d, J ¼ 8.8 Hz), 6.78 (1H, d, J ¼ 10.0 Hz), 6.35 (1H, d,
J ¼ 8.8 Hz), 5.52 (1H, d, J ¼ 10.0 Hz), 5.10–5.05 (1H, m), 2.38 (3H, s),
2.13–2.05 (2H, m), 1.84–1.63 (2H, m), 1.63 (3H, s), 1.54 (3H, s), 1.42
(3H, s); 13C NMR (75 MHz, CDCl3) d 192.4, 161.3, 160.6, 144.7, 141.6,

Synthesis of Spinochalcone B and Analogues
2023
132.5, 132.4, 131.1, 130.1, 129.0, 127.4, 124.2, 119.6, 116.8, 114.3, 109.6,
108.5, 80.8, 42.1, 27.6, 26.1, 23.1, 22.0, 18.1; IR (neat) 2925, 1628, 1582,
1425, 1358, 1283, 1228, 1183, 1113, 981, 797 cm21; HRMS: m/z (Mþ)
calcd. for C26H28O3: 388.2038; found: 388.2041.
Compound (3)
Potassium hydroxide (0.213 g, 3.80 mmol) and p-anisaldehyde (0.078 g,
0.57 mmol) were added to a solution of 7 (0.11 g, 0.38 mmol) in methanol
(10 mL) and water (2 mL) at room temperature. The reaction mixture was
stirred at 608C for 48 h. Methanol was evaporated under reduced pressure
and 2 N-HCl solution (20 mL) was added. Extraction with ethyl acetate
(3 ꢀ 50 mL), washing with brine, drying over MgSO4, and removal of the
solvent followed by flash-column chromatography on silica gel gave 3
1
(0.076 g, 49%). H NMR (300 MHz, CDCl3) d 13.78 (1H, s), 7.84 (1H, d,
J ¼ 15.4 Hz), 7.69 (1H, d, J ¼ 8.8 Hz), 7.59 (2H, d, J ¼ 8.8 Hz), 7.42 (1H,
d, J ¼ 15.4 Hz), 6.92 (2H, d, J ¼ 8.8 Hz), 6.77 (1H, d, J ¼ 10.0 Hz), 6.30
(1H, d, J ¼ 8.8 Hz), 5.52 (1H, d, J ¼ 10.0 Hz), 5.10–5.04 (1H, m), 3.84
(3H, s), 2.15–2.04 (2H, m), 1.83–1.61 (2H, m), 1.63 (3H, s), 1.55 (3H, s),
1.40 (3H, s); 13C NMR (75 MHz, CDCl3) d 192.3, 162.1, 161.3, 160.5,
144.5, 132.3, 131.0, 130.8, 128.0, 127.3, 124.2, 118.2, 116.8, 114.8, 114.4,
109.6, 108.4, 80.7, 55.8, 42.1, 27.6, 26.1, 23.1, 18.1; IR (neat) 2967, 2924,
1631, 1567, 1508, 1477, 1424, 1359, 1287, 1234, 1174, 1112, 1034, 981,
831 cm21; HRMS: m/z (Mþ) calcd. for C26H28O4: 404.1988; found:
404.1987.
Compound (4)
Potassium hydroxide (0.179 g, 3.20 mmol) and m-tolualdehyde (0.058 g,
0.48 mmol) were added to a solution of 7 (0.091 g, 0.32 mmol) in methanol
(10 mL) and water (2 mL) at room temperature. The reaction mixture was
stirred at 608C for 48 h. Methanol was evaporated under reduced pressure,
and 2 N-HCl solution (20 mL) was added. Extraction with ethyl acetate
(3 ꢀ 50 mL), washing with brine, drying over MgSO4, and removal of the
solvent followed by flash-column chromatography on silica gel gave 4
1
(0.056 g, 45%). H NMR (300 MHz, CDCl3) d 13.65 (1H, s), 7.83 (1H, d,
J ¼ 15.4 Hz), 7.69 (1H, d, J¼ 8.8 Hz), 7.53 (1H, d, J ¼ 15.4 Hz), 7.44 (1H,
s), 7.42 (1H, d, J ¼ 7.5 Hz), 7.32–7.22 (2H, m), 6.78 (1H, d, J ¼ 10.0 Hz),
6.35 (1H, d, J ¼ 8.8 Hz), 5.52 (1H, d, J ¼ 10.0 Hz), 5.10–5.05 (1H, m),
2.39 (3H, s), 2.14–2.06 (2H, m), 1.84–1.63 (2H, m), 1.64 (3H, s), 1.56 (3H,
s), 1.42 (3H, s); 13C NMR (75 MHz, CDCl3) d 192.3, 161.4, 160.7, 144.8,
139.1, 135.2, 132.4, 131.9, 131.2, 129.4, 129.3, 127.4, 126.3, 124.2, 120.5,
116.8, 114.4, 109.6, 108.5, 80.8, 42.1, 27.6, 26.1, 23.1, 21.8, 18.1; IR (neat)

2024
Y. R. Lee, X. Wang, and B. S. Kim
2925, 1628, 1585, 1474, 1425, 1357, 1292, 1242, 1111, 981, 902, 852,
780 cm21; HRMS: m/z (Mþ) calcd. for C26H28O3: 388.2038; found: 388.2041.
Compound (5)
Potassium hydroxide (0.190 g, 3.40 mmol) and m-anisaldehyde (0.069 g,
0.51 mmol) were added to a solution of 7 (0.096 g, 0.34 mmol) in methanol
(10 mL) and water (2 mL) at room temperature. The reaction mixture was
stirred at 608C for 48 h. Methanol was evaporated under reduced pressure
and 2 N-HCl solution (20 mL) was added. Extraction with ethyl acetate
(3 ꢀ 50 mL), washing with brine, drying over MgSO4, and removal of
the solvent followed by flash column chromatography on silica gel gave 5
1
(0.054 g, 40%). H NMR (300 MHz, CDCl3) d 13.62 (1H, s), 7.80 (1H, d,
J ¼ 15.4 Hz), 7.68 (1H, d, J ¼ 8.8 Hz), 7.51 (1H, d, J ¼ 15.4 Hz), 7.29 (1H,
t, J ¼ 7.0 Hz), 7.22 (1H, d, J ¼ 7.0 Hz), 7.13 (1H, s), 6.95 (1H, d,
J ¼ 7.0 Hz), 6.78 (1H, d, J ¼ 10.0 Hz), 6.34 (1H, d, J ¼ 8.8 Hz), 5.52 (1H,
d, J ¼ 10.0 Hz), 5.09–5.05 (1H, m), 3.85 (3H, s), 2.15–2.05 (2H, m),
1.82–1.63 (2H, m), 1.64 (3H, s), 1.55 (3H, s), 1.42 (3H, s); 13C NMR
(75 MHz, CDCl3) d 192.2, 161.4, 160.7, 160.3, 144.5, 136.6, 132.4, 131.2,
130.3, 127.4, 124.2, 121.6, 121.0, 116.8, 116.7, 114.3, 113.9, 109.6, 108.6,
80.8, 55.8, 42.1, 27.6, 26.1, 23.1, 18.1; IR (neat) 2967, 2924, 1639, 1586,
1485, 1450, 1359, 1296, 1258, 1113, 1051, 850 cm21; HRMS: m/z (Mþ)
calcd. for C26H28O4: 404.1988; found: 404.1987.
Compound (6)
Potassium hydroxide (0.196 g, 3.50 mmol) and 2,4-dimethylbenzaldehyde
(0.071 g, 0.53 mmol) were added to a solution of 7 (0.10 g, 0.35 mmol) in
methanol (10 mL) and water (2 mL) at room temperature. The reaction
mixture was stirred at 608C for 48 h. Methanol was evaporated under
reduced pressure, and 2 N-HCl solution (20 mL) was added. Extraction with
ethyl acetate (3 ꢀ 50 mL), washing with brine, drying over MgSO4, and
removal of the solvent followed by flash column chromatography on silica
1
gel gave 6 (0.074 g, 53%). H NMR (300 MHz, CDCl3) d 13.71 (1H, s),
8.14 (1H, d, J ¼ 15.4 Hz), 7.72 (1H, d, J ¼ 8.8 Hz), 7.46 (1H, d,
J ¼ 15.4 Hz), 7.14–7.02 (2H, m), 7.11 (1H, s), 6.78 (1H, d, J ¼ 10.0 Hz),
6.32 (1H, d, J ¼ 8.8 Hz), 5.50 (1H, d, J ¼ 10.0 Hz), 5.09–5.05 (1H, m),
2.44 (3H, s), 2.35 (3H, s), 2.15–2.05 (2H, m), 1.82–1.63 (2H, m), 1.64
(3H, s), 1.56 (3H, s), 1.42 (3H, s); 13C NMR (75 MHz, CDCl3) d 192.4,
161.4, 160.6, 136.2, 135.9, 134.0, 132.4, 131.7, 131.3, 131.2, 130.4, 127.4,
127.3, 124.2, 121.4, 116.8, 114.4, 109.6, 108.5, 80.8, 42.1, 27.6, 26.1, 23.1,
21.4, 19.8, 18.1; IR (neat) 2924, 1640, 1584, 1439, 1358, 1276, 1238, 1184,
1111, 977, 906, 847, 806 cm21; HRMS: m/z (Mþ) calcd. for C27H30O3:
402.2195; found: 402.2196.

Synthesis of Spinochalcone B and Analogues
ACKNOWLEDGMENT
2025
This research was supported by the Yeungnam College of Science & Technol-
ogy Research Grants in 2005.
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Mitchell, H. J. J. Am. Chem. Soc. 2000, 122, 9939; (b) Nicolaou, K. C.;
Pfefferkorn, J. A.; Mitchell, H. J.; Roecker, A. J.; Cao, G.-Q.; Affleck, R. L.;
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