6-Bicycloaryl substituted (S)- and (R)-5,6-dihydro-2H-pyran-2-ones: Asymmetric synthesis, and anti-proliferative properties

Article abstract of DOI:10.1016/j.bmc.2008.10.069

(R)-Goniothalamin, is a member of styryl lactones, possesses selective cytotoxicity against cancer cell lines. In this work, replacement of styryl substituent with 2-naphthyl and 3-quinoyl gave new analogues which may have less conformational changes comp

Full text of DOI:10.1016/j.bmc.2008.10.069

Bioorganic & Medicinal Chemistry 17 (2009) 311–318
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
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6-Bicycloaryl substituted (S)- and (R)-5,6-dihydro-2H-pyran-2-ones:
Asymmetric synthesis, and anti-proliferative properties
Pınar Kasaplar a, Özgür Yılmazer b, Ali Çag˘ır a,
*
a
_
_
Izmir Institute of Technology, Faculty of Science, Department of Chemistry, Urla 35430, Izmir, Turkey
Izmir Institute of Technology, Biotechnology and Bioengineering Central Research Laboratories, Urla 35430, Izmir, Turkey
b
_
_
a r t i c l e i n f o
a b s t r a c t
Article history:
(R)-Goniothalamin, is a member of styryl lactones, possesses selective cytotoxicity against cancer cell
lines. In this work, replacement of styryl substituent with 2-naphthyl and 3-quinoyl gave new analogues
which may have less conformational changes compared to the lead compound. Anti-proliferative tests
indicated that 2-naphthyl substituted (R)-5,6-dihydro-2H-pyran-2-one has slightly better cytotoxicity
than (R)-goniothalamin. To clarify the effect of 2-naphthyl substituent additional aryl substituted (R)-
5,6-dihydro-2H-pyran-2-ones have been synthesized enantioselectively and tested against PC-3 and
MCF-7 cell lines.
Received 26 September 2008
Revised 26 October 2008
Accepted 30 October 2008
Available online 5 November 2008
Keywords:
(R)-Goniothalamin
Cytotoxic activity
Ó 2008 Elsevier Ltd. All rights reserved.
Conformationally constrained analogues
Cancer cell lines
1. Introduction
O
O
One of the important issues of medicinal chemistry is to design
compounds which selectively target the cancer cells preferably
with no or minimized activity against normal cells. Goniothalamin
(1), a naturally occurring styryl lactone, can be considered as a
good lead compound for this purpose. Goniothalamin was first iso-
lated from Cryptocarya caloneura in 1967,1 and later from the other
natural sources (Fig. 1).2–7
*
Michael acceptor
linker
1
Figure 1. Structure of goniothalamin (1).
Besides weak antibacterial and strong antifungal activity of 1,8
(R)-goniothalamin (1a) has shown significant cytotoxicity against
a variety of cancer cell lines like HeLa, HGC-27, MCF-7, T47D,
MDA-MB-231, Caov-3, HL-60, NCI ADR, NCI 460, UACC62, 786-0,
OVCAR03, PCO 3, and HT 29 in vitro.9–15 Pihie and coworkers have
shown that, 1a has no significant cytotoxicity toward non-malig-
nant cells,10 which implies that it has activity mainly in malignant
cells. Its tumoricidal and tumoristatic effects have also been re-
ported in vivo.16 Recent studies showed that several (S)-goniothal-
amin (1b) derivatives, enantiomer of 1a, also have similar cytotoxic
activity against several tumor cell lines (Fig. 2).17
Although the mechanism of action of the goniothalamin deriv-
atives is not fully understood yet, several studies demonstrated
that 1a is a potential genotoxic substance.18 Besides the caspase-
9 activation and loss of mitochondrial membrane potential of the
HL-60 leukemia cells,13 it is also responsible for an increase in
O
O
O
O
O
1a
1b
O
O
O
O
2
3
* Corresponding author. Tel.: +90 232 7507572; fax: +90 232 7507509.
E-mail address: alicagir@iyte.edu.tr (A. Çag˘ır).
Figure 2. Structures of (R)-goniothalamin (1a), (S)-goniothalamin (1b), (R)-gonio-
thalamin analogues having linker cis-C@C (2), and an ether (3).
0968-0896/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2008.10.069

312
P. Kasaplar et al. / Bioorg. Med. Chem. 17 (2009) 311–318
lated on the basis of chiral HPLC studies as reported above.
O
O
O
Through the synthesis, enantiomeric excesses of 3-phenoxyphenyl
substituted derivatives (13g, 14g, and 10) were almost same. On
the other hand, when the substituent has been changed to a bicy-
cloaryl group enantiomeric excess of the products fluctuated in all
steps. The most dramatic changes in enantiomeric excesses have
been observed during the synthesis of compounds 6 and 11.
Although these two compounds tended to yield racemic mixtures
in chromatography, enantiomeric enrichment was observed in
the synthesis of compounds 5 and 7–9. Enantiomeric enrichment
was first reported by Crooks et al.,26 and such enrichment pro-
cesses were reported for many different compounds,27 including
molecules having benzylic hydrogen on the chiral carbon.28
As a reference in cytotoxicity tests, racemic goniothalamin (1)
was prepared according to the literature, defined by Fatima et al.
in the absence of R-BINOL (59) with 36% overall yield. Product
was purified from SiO2 column and retention times of both
enantiomers were monitored in HPLC Chiracel AD-H Column (i-
propanol/hexane 1:9, 1 mL/min t1 = 7.65 min and t2 = 7.98 min).
Then (R)-goniothalamin (1a) was synthesized by same procedure
in the presence of R-BINOL starting from trans-cinnamaldehyde
with 38% overall yield and 65% ee. Enantiomers were monitored
in HPLC Chiracel AD-H Column under the same conditions and it
was seen that the ratio of the peaks was different than that of
racemic one and enantiomeric excess was calculated by using
the area under these signals. Cytotoxic properties of synthesized
compounds (1a and 4–10) were evaluated by MTT test on two
cancer cell lines (PC-3 prostate cancer and MCF-7 human breast
adenocarcinoma). Additional cytotoxicity tests for 1a, 4, and 11
were performed against two more cancer cell lines (DU-145,
metastatic human prostate adenocarcinomas; LNCAP, lymph
node metastasis of human prostate adenocarcinoma). As men-
tioned above, a Michael acceptor in lactone ring is crucial for
cytotoxicity, similarly compounds 14a–g have also a Michael
acceptor in their structures. Although they are not lactones they
may also possesses anti-proliferative property. To better under-
stand the importance of the lactone ring, compounds 14b–g
were also tested against PC-3 and MCF-7 cell lines. IC50 values
of all MTT tests are listed in Table 2.
It is found that, all of the lactone products have more potent
cytotoxicity over tested cell lines compared to their acrylate pre-
cursors. Interestingly, in case of acrylates there could not be found
any structure–activity relationship, while anti-proliferative effects
of lactone derivatives imply a structure dependent activity. Com-
pound 14e was the most active one among the tested acrylate
derivatives.
It is observed that, analogues 4 and 5 have slightly better
anti-proliferative properties compared to (R)-goniothalamin
which may be the result of either restriction of rotation around
the styrene part of the molecule or steric effect of additional
atoms in the 2-naphthyl and 3-quinoyl substituent. On the other
hand compound 11 is four and two times less cytotoxicity in PC-
3 and MCF-7 cells respectively, compared to its enantiomer 4.
This result was in agreement with those reported for (R)- and
(S)-goniothalamin.17
O
O
O
X
CH3
X
4 X=C
5 X=N
6 X=C
7 X=N
8
O
O
O
O
O
O
O
H3C
9
10
11
Figure 3. Structures of the proposed aryl substituted 5,6-dihydro-2H-pyran-2-ones
(4–11).
Bax (pro-apoptotic protein) levels,12,14 and for the activation of p53
tumor suppressor protein.16
Because of the interesting biological activities of 1a and 1b, sev-
eral asymmetric synthesis routes have been developed mainly in
the last decade.15,17,19–25 In this work, we represent the asymmet-
ric synthesis and biological activities of three new conformational-
ly constrained analogues of (R)- and (S)-goniothalamin (4, 5, and
11, Fig. 3) and five additional 6-aryl substituted (R)-5,6-dihydro-
2H-pyran-2-ones.
2. Results and discussion
Up to date, there is limited information about the activity struc-
ture relationship (SAR) of goniothalamin analogues. Two recently
published works made contributions to the literature in this man-
ner. de Fatima et al. showed that (R)-goniothalamin analogue, hav-
ing cis-double bond between the carbons in the linker part (2), was
2-fold less cytotoxic compared to 1a towards the tested cancer cell
lines except breast cell lines (MCF-7 and NCI ADR). In the same
study another (R)-goniothalamin analogue, having ether function-
ality in the linker part (3), has been synthesized and evaluated
against 8 different cancer cells. Although compound 3 shows 2–6
times lower cytotoxicity than 1a towards five of the selected can-
cer cells, 3 had comparatively better activity in the cell lines MCF-
7, OVCAR03, and PCO.15 It is believed that Michael acceptor and the
trans-oriented double bond in the linker parts were essential for
biological activity (Fig. 1). In this work, to better understand the
role of the linker part, 2-napthyl and 3-quinoyl structures are pro-
posed in the place of phenyl ring and trans-oriented linker part (4,
5, and 11). By this way, rotation around the single bond between
the phenyl ring and linker will be restricted and it may form fully
planar structure.
The enantioselective synthesis of target compounds has been
accomplished by method developed by de Fatima et al.15 As shown
in Table 1, asymmetric allylation of aldehydes (12a–g) gave (R)-
Sterically the most hindered analogue 10 has the weakest
activity among the tested lactones. 1-Naphthyl substituted (R)-
5,6-dihydro-2H-pyran-2-ones (6, 8, and 9) gave more promising
results. Especially compound 9 is 80 times more potent com-
pared to (R)-goniothalamin in PC-3 cells (IC50 = 50 nM), and 40
times more potent compared to (R)-goniothalamin in MCF-7
cells (IC50 = 440 nM). Structurally 1-naphthyl derivatives seem
much closer to the goniothalamin analogue which has a cis-
double bond in its linker domain (2). Contrarily it is discussed
above that compound 2 has diminished cytotoxicity compared
to 1a.
homoallylic alcohols (13a–g) in the presence of
l-oxobis(R-bina-
phthoxy) (isopropoxy)titanium complex. When S-BINOL was used
in the same reaction (S)-homoallylic alcohol (15) was produced.
The enantiomeric excesses of the alcohols were determined by
HPLC studies by employing Chiracel AD-H column (i-propanol/
hexane mixtures as eluent). Yields and enantiomeric excesses were
reported in Table 1. In the second step purified alcohols were acry-
lated in the presence of acryloylchloride and triethylamine to form
esters 14a–g and 16. Ring closing metathesis yielded the final
products 4–11. Enantiomeric excesses of all products were calcu-

P. Kasaplar et al. / Bioorg. Med. Chem. 17 (2009) 311–318
313
Table 1
Synthesis, conditions, yields and ee% of compounds 4–11.
O
O
i
OH
ii
iii
4-10
O
Ar
H
Ar
Ar
12a-g
13a-g
14a-g
O
O
iv
OH
ii
iii
11
O
Ar
H
Ar
Ar
12a
15
16
Conditions: (i) R-BINOL (10 mol%), Ti(Oi-Pr)4 (15 mol%), TiCl4 (5 mol%), allyltributyltin, ꢀ20 °C, 24 h. (ii) acryloyl chloride, Et3N, CH2Cl2, 0 °C; (iii) Grubbs’ catalyst, 60 °C, CH2Cl2,
(iv) S-BINOL (10 mol%), Ti(Oi-Pr)4 (15 mol%), TiCl4 (5 mol%), allyltributyltin, ꢀ20 °C, 24 h
Aldehydes
Ar
Alcohol (Yield, ee%)a
Ester (Yield, ee%)
Pyran-2-one (Yield, ee%)
12a
13a (59, 80)
14a (53, 79)
4 (88, 76)
12b
12c
13b, (48, 93)
13c, (41, 77)
14b, (54, 92)
14c, (69, 44)
5, (62, 97)
6, (75, 11)
N
N
12d
12e
13d, (21, 65)
13e, (19, 97)
14d, (56, 100)
14e, (62, 100)
7, (34, 95)
CH3
8, (60, 100)
12f
13f, (14, 72)
14f, (56, 66)
9, (87, 93)
CH3
O
12g
13g, (11, 76)
15, (26, 82)
14g, (76, 75)
16, (73, 81)
10, (91, 77)
11, (73, 43)
12a
a
Yields are reported based on purified products and ee% are determined by Chiral HPLC column.
3. Conclusion
4. Experimental
4.1. Chemistry part
4.1.1. General procedures
Reagents were commercial grade and were used as supplied.
Dichloromethane was distilled over calcium hydride. Reactions
were monitored by TLC using Merck TLC plates (Silicagel 60
F254). Chromatographic separations were performed using 70–
230 mesh silica gel. Solvents, required for SiO2 column chromatog-
raphy, were commercial grade and were used as supplied. Solvents,
required for HPLC, were spectrometric grade and were used as sup-
plied. 1H NMR and 13C NMR data were recorded on a Varian 400-
MR (400 MHz) spectrometer. Chemical shifts for 1H NMR and 13C
The enantioselective syntheses of nine new 6-aryl substi-
tuted (R)-5,6-dihydro-2H-pyran-2-ones were accomplished.
Cytotoxic activities of these compounds showed that, restric-
tion of the rotation around the single bond between the phe-
nyl ring and double bond somehow causes an enhancement in
the cytotoxicity. In addition, size of the substituent and the
stereochemistry in the lactone ring are also important, (R)
enantiomer has lower IC50 value for 2-naphthyl substituted
analogues. 1-Naphthyl substitution in the lactone ring dramat-
ically enhanced the activity. Any additional methyl substitution
in the naphthalene ring at position 2 and 4 produce highly
cytotoxic compounds.

314
P. Kasaplar et al. / Bioorg. Med. Chem. 17 (2009) 311–318
Table 2
anes, 1:6) furnished 253 mg of (R)-(+)-1-(quinolin-3-yl)-but-3-en-
IC50 (l
M) values for tested compoundsa
1-ol (13b) as a yellow solid with 48% yield. Rf = 0.22 (ethyl acetate/
hexanes, 1:1); ½a D30
ꢂ
+28.21 (c 2.53, EtOH); 1H NMR (400 MHz,
Entry
PC-3
MCF-7
DU-145
LNCAP
CDCl3) d 8.72 (s, 1H), 8.06 (s, 1H), 8.00 (d, 1H, J = 8.22 Hz), 7.71
(d, 1H, J = 8.22 Hz), 7.65–7.58 (m, 1H), 7.51–7.44 (m, 1H), 5.85–
5.72 (m, 1H), 5.14–5.06 (m, 2H), 4.93–4.87 (m, 1H), 4.15 (br s,
1H), 2.59–2.52 (m, 2H); 13C NMR (400 MHz, CDCl3) d 149.19,
147.15, 136.83, 133.66, 132.78, 129.20, 128.66, 127.71, 127.69,
126.70, 118.71, 71.06, 43.56; Enantiomeric excess was found as
93% with HPLC—Chiracel AD-H column (i-propanol/hexane 5:95,
1 mL/min t1 = 23.90 min ‘minor enantiomer’, t2 = 26.40 min ‘major
enantiomer’).
1a
4
5
6
7
4.0
3.0
2.5
0.8
19.0
12.0
3.2
2.6
32.5
2.6
0.44
>50.0
28.0
28.8
>50.0
13.2
10.4
33.1
>50.0
12.0
11.0
—
—
—
—
—
—
15.0
—
28.0
19.0
—
—
—
—
—
—
37.0
—
9.8
8
9
0.13
0.05
11
12.0
16.3
22.9
15.0
8.8
10
11
14b
14c
14d
14e
14f
14g
—
—
—
—
—
—
—
—
4.1.4. (R)-(+)-1-(Naphthalen-1-yl)-but-3-en-1-ol (13c)
45.0
>50.0
After the removal of solvent under vacuum, purification of
the crude by column chromatography on silica gel (ethyl ace-
tate/hexanes, 1:8) furnished 214 mg of (R)-(+)-1-(naphthalen-1-
yl)-but-3-en-1-ol (13c) as a light yellow solid with 41% yield.
—
—
a
Concentrations, that are needed to inhibit 50% of the cell growth, were deter-
mined from nonlinear regression analysis using the GraphPad Prism software
(r2 > 0.9).
Rf = 0.42 (ethyl acetate/hexanes, 1:4);
½
a 2D6
+84.35 (c 2.14,
ꢂ
CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.07 (d, 1H, J = 7.18 Hz),
7.92–7.87 (m, 1H), 7.79 (d, 1H, J = 8.08 Hz), 7.67 (d, 1H,
J = 7.18 Hz), 7.57–7.46 (m, 3H), 5.99–5.88 (m, 1H), 5.55–5.48
(m, 1H), 5.26–5.16 (m, 2H), 2.81–2.73 (m, 1H), 2.66–2.56 (m,
NMR are reported in d (ppm). CDCl3 peaks were used as reference
in 1H NMR (7.26 ppm) and 13C NMR (77.36 ppm), respectively.
Optical rotations were measured with Optical Digital Polarimeter
(SOLF) model WZZ-1S instrument. HPLC studies were performed
by employing Chiracel AD-H column (0.46 ꢁ 150 mm) on Agilent
1100 Series HPLC. GC-Mass spectra (EI) were measured on Agilent
6890N Network GC System equipped with a Quadrupole Mass
Spectrometer (EI).
1H), 2.37 (br s, 1H); 13C NMR (400 MHz, CDCl3)
d 139.34,
134.71, 133.68, 130.15, 128.87, 127.87, 125.94, 125.41,
125.36, 122.90, 122.76, 118.22, 69.88, 42.76. MS (EI) m/z calcu-
lated for M+ (C14H14O) = 198.1; found: 198 (2%), 179 (100%),
166, 157, 129; HPLC—Chiracel AD-H column was used and ee
was found as 77%, (i-propanol/hexane 5:95, 1 mL/min
t1 = 7.57 min
‘minor
enantiomer’,
t2 = 8.62 min
‘major
4.1.2. (R)-(+)-1-(Naphthalen-2-yl)-but-3-en-1-ol (13a)
enantiomer’).
In a 10 mL round-bottomed flask equipped with a magnetic stir-
ring bar and a condenser, 24.8 mg (14
dissolved in 2.6 mL of dichloromethane. To this solution, 117.8 mg
(120 L, 0.414 mmol) of Ti(Oi-Pr)4 was added under nitrogen
atmosphere. The resulting solution was allowed to warm up to
room temperature for 1 h. and then 61 mg (0.26 mmol) of silver
(I) oxide was added. The mixture was stirred for 5 h without any
exposure to direct day light. After dilution with 4.5 mL of dichloro-
methane, 150 mg (0.524 mmol) of R-BINOL was added and stirred
for 2 h. The resulting mixture was cooled down to ꢀ75 °C, and then
treated sequentially with 409 mg (2.62 mmol) of 2-naphthalde-
l
L, 0.131 mmol) of TiCl4 was
4.1.5. (R)-(+)-1-(Quinolin-4-yl)-but-3-en-1-ol (13d)
After the removal of solvent under vacuum, purification of the
crude by column chromatography on silica gel (ethyl acetate/hex-
anes, 1:6) furnished 73 mg of (R)-(+)-1-(quinolin-4-yl)-but-3-en-1-
ol (13d) as a colorless oil with 21% yield. Rf = 0.22 (ethyl acetate/
l
hexanes, 1:1); ½a D21
ꢂ
+67.08 (c 0.73, EtOH); 1H NMR (400 MHz,
CDCl3) d 8.71–8.65 (m, 1H), 8.06–8.00 (m, 1H), 7.97–7.91 (m,
1H), 7.65–7.58 (m, 1H), 7.55–7.45 (m, 2H), 5.94–5.83 (m, 1H),
5.52–5.46 (m, 1H), 5.18–5.10 (m, 2H), 4.30 (br s,1H), 2.74–2.65
(m,1H), 2.57–2.47 (m, 1H); 13C NMR (400 MHz, CDCl3) d 150.04,
149.94, 147.68, 133.94, 129.80, 128.98, 126.43, 125.31, 122.82,
118.50, 117.52, 68.78, 42.71; Enantiomeric excess was found as
65% with HPLC—Chiracel AD-H column (i-propanol/hexane 5:95,
1 mL/min t1 = 14.70 min ‘major enantiomer’, t2 = 17.09 min ‘minor
enantiomer’).
hyde and 953 mg (893 lL, 2.88 mmol) of allyltributyltin. The mix-
ture was stirred for 16 h and allowed to warm up to room
temperature. After the reaction was completed, the reaction mix-
ture was filtered through a short pad of Celite, then quenched with
saturated NaHCO3 solution, and extracted with 3ꢁ 30 mL of ethyl
acetate. The organic extracts were combined and dried over
MgSO4. After the removal of solvent under vacuum, purification
of the crude by column chromatography on silica gel (ethyl ace-
tate/hexanes, 1:8) furnished 309 mg of (R)-1-(naphthalen-2-yl)-
but-3-en-1-ol (13a) as a colorless foam with 59% yield. Rf = 0.65
4.1.6. (R)-1-(2-Methylnaphthalen-1-yl)-but-3-en-1-ol (13e)
After the removal of solvent under vacuum, purification of the
crude by column chromatography on silica gel (ethyl acetate/
hexanes, 1:8) furnished 104 mg of (R)-(+)-1-(2-methylnaphtha-
len-1-yl)-but-3-en-1-ol (13e) as a colorless oil with 19% yield.
(ethyl acetate/hexanes, 1:2); ½a D30
ꢂ
+52.7 (c 3.00, CH2Cl2); 1H NMR
(400 MHz, CDCl3) d 7.88-7.78 (m, 4H), 7.53–7.44 (m, 3H), 5.91–
5.77 (m, 1H), 5.23–5.12 (m, 2H), 4.90 (t, 1H, J = 6.3 Hz), 2.68–2.54
(m, 2H), 2.25 (s, 1H); 13C NMR (400 MHz, CDCl3) d 141.58,
134.68, 133.59, 133.28, 128.52, 128.28, 128.00, 126.44, 126.13,
124.83, 124.33, 118.81, 73.72, 44.04; MS (EI) m/z calculated for
M+ (C14H14O) = 198.1; found: 198 (2%), 179 (100%), 166, 157,
129; Enantiomeric excess was found as 80% with HPLC—Chiracel
AD-H column (i-propanol/hexane 10:90, 1 mL/min t1 = 5.51 min
‘major enantiomer’, t2 = 5.97 min ‘minor enantiomer’).
Rf = 0.34 (ethyl acetate/hexanes, 1:6); ½a D21
ꢂ
(could not be mea-
sured) (c 1.04, many different solvents were tried); 1H NMR
(400 MHz, CDCl3)
d 8.67 (d, 1H, J = 8.61 Hz), 7.81 (d, 1H,
J = 7.82 Hz), 7.51–7.39 (m, 2H), 7.29–7.24 (m, 1H), 5.96–5.84
(m, 1H), 5.64–5.57 (m, 1H), 5.21 (ddd, 1H, J = 17.21, 3.13 and
1.56 Hz), 5.17–5.12 (m, 1H), 3.60–2.96 (m, 1H), 2.76–2.67 (m,
1H), 2.56 (s, 3H), 2.20 (br s, 1H); 13C NMR (400 MHz, CDCl3) d
135.30, 135.08, 133.38, 132.99, 131.26, 129.49, 128.70, 128.03,
125.63, 125.50, 124.64, 117.90, 71.54, 41.21, 21.00; Enantiomeric
excess was found as 96% with HPLC—Chiracel AD-H column was
used and ee was found as 93%, (i-propanol/hexane 5:95, 1 mL/
min t1 = 3.70 min ‘minor enantiomer’, t2 = 4.50 min ‘major
enantiomer’).
4.1.3. (R)-(+)-1-(Quinolin-3-yl)-but-3-en-1-ol (13b)
After the removal of solvent under vacuum, purification of the
crude by column chromatography on silica gel (ethyl acetate/hex-

P. Kasaplar et al. / Bioorg. Med. Chem. 17 (2009) 311–318
315
4.1.7. (R)-(+)-1-(4-Methylnaphthalen-1-yl)-but-3-en-1-ol (13f)
After the removal of solvent under vacuum, purification of the
crude by column chromatography on silica gel (ethyl acetate/hex-
anes, 1:10) furnished 71 mg of (R)-(+)-1-(4-methylnaphthalen-1-
yl)-but-3-en-1-ol (13f) as a yellow oil with 14% yield. Rf = 0.24
1H), 5.16–5.00 (m, 2H), 2.85–2.63 (m, 2H); 13C NMR (400 MHz,
CDCl3) d 165.74, 137.64, 133.49, 133.45, 133.44, 131.28, 128.92,
128.65, 128.41, 128.01, 126.56, 126.45, 126.10, 124.62, 118.56,
75.86, 41.00;MS (EI) m/z calculated for M+ (C17H16O2) = 252.1;
found: 252 (2%), 224, 178, 156 (100%), 128, 68; Enantiomeric ex-
cess was found as 79% with HPLC—Chiracel AD-H column (i-propa-
nol/hexane 10:90, 1 mL/min t1 = 2.80 min ‘major enantiomer’,
t2 = 3,50 min ‘minor enantiomer’).
(ethyl acetate/hexanes, 1:6); ½a D20
ꢂ
+57.72 (c 0.71, CH2Cl2); 1H
NMR (400 MHz, CDCl3) d 8.14–8.03 (m, 2H), 7.58–7.51 (m, 3H),
7.34 (d, 1H, J = 7.43 Hz), 6.00–5.89 (m, 1H), 5.55–5.49 (m, 1H),
5.26–5.15 (m, 2H), 2.81–2.73 (m, 1H), 2.70 (s, 3H), 2.66–2.57 (m,
1H), 2.11 (br s, 1H); 13C NMR (400 MHz, CDCl3) d 137.51, 134.89,
134.04, 132.85, 130.37, 126.21, 125.67, 125.36, 124.98, 123.48,
122.55, 118.22, 69.96, 42.85, 19.58; Enantiomeric excess was
found as 72% with HPLC—Chiracel AD-H column (i-propanol/hex-
4.1.11. (R)-(+)-1-(Quinolin-3-yl)-but-3-enyl acrylate (14b)
Purification of the crude product by column chromatography on
silica gel (ethyl acetate/hexane, 1:8) gave 171 mg of (R)-(+)-1-
(quinolin-3-yl)-but-3-enyl acrylate (14b) as a yellow solid with
ane
5:95,
1 mL/min
t1 = 6.80 min
‘major
enantiomer’,
54% yield. Rf = 0.26 (ethyl acetate/hexanes, 1:4); ½a D18
ꢂ
+74.37 (c
t2 = 7.10 min ‘minor enantiomer’).
1.71, EtOH); 1H NMR (400 MHz, CDCl3) d 8.92 (d, 1H, J = 2.35 Hz)
8.11–8.06 (m, 2H), 7.79 (d, 1H, J = 8.22 Hz), 7.67 (ddd, 1H,
J = 8.22, 6.65, and 1.56 Hz), 7.55–7.48 (m, 1H), 6.43 (dd, 1H,
J = 17.61 and 1.56 Hz), 6.20–6.11 (m, 1H), 6.09–6.04 (m, 1H), 5.83
(dd, 1H, J = 10.56 and 1.56 Hz), 5.78–5.66 (m, 1H), 5.12–5.04 (m,
2H), 2.86–2.77 (m, 1H), 2.75–2.66 (m, 1H); 13C NMR (400 MHz,
CDCl3) d 165.08, 149.21, 147.74, 133.69, 132.48, 132.18, 131.35,
129.53, 129.13, 128.04, 127.77, 127.42, 126.82, 118.89, 73.34,
40.26; Enantiomeric excess was found as 92% with HPLC—Chiracel
AD-H column (i-propanol/hexane 1:99, 1 mL/min t1 = 19.50 min
‘major enantiomer’, t2 = 21.50 min ‘minor enantiomer’).
4.1.8. (R)-(+)-1-(3-Phenoxyphenyl)-but-3-en-1-ol (13g)
After the removal of solvent under vacuum, purification of the
crude by column chromatography on silica gel (ethyl acetate/hex-
anes, 1:14) furnished 72 mg of (R)-(+)-1-(3-phenoxyphenyl)-but-
3-en-1-ol (13g) as a colorless oil with 11% yield. Rf = 0.12 (ethyl
acetate/hexanes, 1:10); ½a D22
ꢂ
+31.66 (c 0.72, CH2Cl2); 1H NMR
(400 MHz, CDCl3) d 7.38–7.28 (m, 3H), 7.17–7.08 (m, 2H), 7.06–
7.00 (m, 3H), 6.92 (ddd, 1H, J = 8.22, 2.74 and 1.17 Hz), 5.86–5.74
(m, 1H), 5.19–5.15 (m, 1H), 5.15–5.13 (m, 1H), 4.74–4.68 (m,
1H), 3.43–2.57 (m, 2H), 2.23 (br d, 1H, J = 2.74 Hz); 13C NMR
(400 MHz, CDCl3)
d
157.33, 157.12, 146.00, 134.15, 129.72,
4.1.12. (R)-(+)-1-(Naphthalen-1-yl)-but-3-enyl acrylate (14c)
Purification of the crude product by column chromatography on
silica gel (ethyl acetate/hexane, 1:8) gave 186 mg of (R)-(+)-1-
(naphthalen-1-yl)-but-3-enyl acrylate (14c) with 69% yield.
129.70, 123.23, 120.58, 118.84, 118.64, 117.83, 116.30, 72.87,
43.79; Enantiomeric excess was found as 76% with HPLC—Chiracel
AD-H column (i-propanol/hexane 5:95, 1 mL/min t1 = 6.90 min
‘major enantiomer’, t2 = 7.80 min ‘minor enantiomer’).
Rf = 0.63 (ethyl acetate/hexanes, 1:4); ½a D26
ꢂ
+7.92 (c 2.12, EtOAc)
was detected for 73% ee in the second synthesis); 1H NMR
4.1.9. (S)-(ꢀ)-1-(Naphthalen-2-yl)-but-3-en-1-ol (15)
(400 MHz, CDCl3) d 8.16 (d, 1H, J = 8.27 Hz), 7.88 (d, 1H,
Catalyst was prepared by using S-BINOL instead of R-BINOL, and
same procedure was applied for aldehyde 12a. After the removal of
solvent under vacuum, purification of the crude by column chro-
matography on silica gel (ethyl acetate/hexanes, 1:8) furnished
133 mg of (S)-(ꢀ)-1-(naphthalen-2-yl)-but-3-en-1-ol (15) as a
light yellow solid with 26% yield. Rf = 0.42 (ethyl acetate/hexanes,
J = 8.27 Hz), 7.81 (d, 1H, J = 8.27 Hz), 7.61–7.44 (m, 4H), 6.71–
6.66 (m, 1H), 6.47 (dd, 1H, J = 17.46 and 1.84 Hz), 6.21 (dd, 1H,
J = 17.46 and 10.11 Hz), 5.89–5.74 (m, 2H), 5.15–5.04 (m, 2H),
2.87–2.81 (m, 2H); 13C NMR (400 MHz, CDCl3) d 165.59, 136.08,
134.04, 133.69, 131.21, 130.55, 129.15, 128.77, 128.73, 126.54,
125.89, 125.45, 124.11, 123.39, 118.23, 72.73, 40.60; Enantiomeric
excess was found as 44% with HPLC—Chiracel AD-H column (i-pro-
panol/hexane 5:95, 1 mL/min t1 = 3.21 min ‘major enantiomer’,
t2 = 4.22 min ‘minor enantiomer’).
1:4); ½a 2D6
ꢂ
ꢀ47.87 (c 1.32, CH2Cl2); 1H NMR (400 MHz, CDCl3) d
7.88–7.78 (m, 4H), 7.53–7.44 (m, 3H), 5.91–5.77 (m, 1H), 5.23–
5.12 (m, 2H), 4.90 (t, 1H, J = 6.3 Hz), 2.68–2,54 (m, 2H), 2.25 (s,
1H); 13C NMR (400 MHz, CDCl3) d 141.58, 134.68, 133.59, 133.28,
128.52, 128.28, 128.00, 126.44, 126.13, 124.83, 124.33, 118.81,
73.72, 44.04; MS (EI) m/z calculated for M+ (C14H14O) = 198,1;
found: 198 (2%), 179 (100%), 166, 157, 129; Enantiomeric excess
was found as 82% with HPLC—Chiracel AD-H column (i-propanol/
hexane 10:90, 1 mL/min t1 = 5.51 min ‘minor enantiomer’,
t2 = 5.95 min ‘major enantiomer’).
4.1.13. (R)-(ꢀ)-1-(Quinolin-4-yl)-but-3-enyl acrylate (14d)
Purification of the crude product by column chromatography on
silica gel (ethyl acetate/hexane, 1:8) gave 43 mg of (R)-(+)-1-(quin-
olin-4-yl)-but-3-enyl acrylate (14d) as a yellow oil with 56% yield.
Rf = 0.15 (ethyl acetate/hexanes, 1:4); ½a D28
ꢀ5.50 (c 2.30, CH2Cl2);
ꢂ
1H NMR (400 MHz, CDCl3) d 8.90 (d, 1H, J = 4.30 Hz) 8.18–8.07
(m, 2H), 7.73 (ddd, 1H, J = 8.22, 6.65, and 1.17 Hz), 7.60 (ddd, 1H,
J = 8.22, 7.04, and 1.17 Hz), 7.43 (d, 1H, J = 3.91 Hz), 6.62 (dd, 1H,
J = 7.43 and 5.48 Hz), 6.49 (dd, 1H, J = 17.22 and 1.56 Hz), 6.22
(dd, 1H, J = 17.22 and 10.56 Hz), 5.90 (dd, 1H, J = 10.56 and
1.17 Hz), 5.83–5.71 (m, 1H), 5.13–5.05 (m, 2H), 2.85–2.71 (m,
2H); 13C NMR (400 MHz, CDCl3) d 165.08, 150.07, 148.39, 145.45,
132.41, 131.67, 130.46, 129.28, 128.01, 126.88, 125.19, 122.91,
118.74, 117.83, 71.21, 40.01; Enantiomeric excess was found as
100% with HPLC—Chiracel AD-H column (i-propanol/hexane 1:99,
1 mL/min t1 = 11.50 min ‘single peak’).
4.1.10. (R)-(+)-1-(Naphthalen-2-yl)but-3-enyl acrylate (14a)
A solution of 302 mg (1.523 mmol) of 13a in 3.0 mL of dichloro-
methane was cooled down to 0 °C; then 248 mg of acryloyl chlo-
ride (223 lL, 2.74 mmol) and 554.6 mg of triethyl amine (770 lL,
5.48 mmol) were sequentially added. The mixture was warmed
to room temperature and stirred for 22 h under nitrogen atmo-
sphere. The resulting mixture was filtered through a short pad of
Celite, poured into water, and the product was extracted with 3ꢁ
25 mL of dichloromethane. The combined organic layer was con-
centrated under reduced pressure and purification of this residue
by column chromatography on silica gel (ethyl acetate/hexane,
1:8) gave 204.8 mg of (R)-1-(naphthalen-2-yl)but-3-enyl acrylate
4.1.14. (R)-(+)-1-(2-Methylnaphthalen-1-yl)-but-3-enyl acrylate
(14e)
(14a) with 53% yield. Rf = 0.63 (ethyl acetate/hexanes, 1:4); ½a D25
ꢂ
Purification of the crude product by column chromatography on
silica gel (ethyl acetate/hexane, 1:10) gave 81 mg of (R)-(+)-1-(2-
methylnaphthalen-1-yl)-but-3-enyl acrylate (14e) as a light yellow
+67.46 (c 2.05, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 7.88–7.70
(m, 4H), 7.53–7.41 (s, 3H), 6.44 (d, 1H, J = 17.3 Hz), 6.24–6.12 (m,
1H), 6.09–6.00 (m, 1H), 5.84 (d, 1H, J = 10.4 Hz), 5.80–5.67 (m,
oil with 62% yield. Rf = 0.47 (ethyl acetate/hexanes, 1:4); ½a D18
ꢂ

316
P. Kasaplar et al. / Bioorg. Med. Chem. 17 (2009) 311–318
+15.15 (c 0.80, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 8.51 (d, 1H,
J = 8.61 Hz), 7.82 (d, 1H, J = 7.82 Hz), 7.71 (d, 1H, J = 8.61 Hz),
7.54–7.48 (m, 1H), 7.46–7.41 (m, 1H), 7.29 (d, 1H, J = 8.22 Hz),
6.42 (dd, 1H, J = 17.22 and 1.56 Hz), 6.18 (dd, 1H, J = 17.22 and
10.56 Hz), 5.84–5.72 (m, 2H), 5.14 (ddd, 1H, J = 17.22, 3.13, and
1.56 Hz), 5.10–5.05 (m, 1H), 3.19–3.09 (m, 1H), 2.92–2.83 (m,
1H), 2.68 (s, 3H); 13C NMR (400 MHz, CDCl3) d 165.42, 134.28,
133.54, 133.27, 132.01, 131.08, 130.72, 129.34, 128.84, 128.53,
128.46, 125.73, 124.54, 117.92, 117.90, 72.83, 39.11, 20.92; Enan-
tiomeric excess was found as 100% with HPLC—Chiracel AD-H col-
umn (i-propanol/hexane 1:99, 0.7 mL/min t1 = 4.00 min single
peak).
4.1.18. (R)-(+)-5,6-Dihydro-6-(naphthalen-2-yl)pyran-2-one (4)
To a stirred solution of 80.2 mg of Grubbs’ catalyst (10 mol%) in
8 mL dichloromethane at 60 °C was added a solution of 205 mg
(0.812 mmol) of 14a in 90 mL of dichloromethane. The resulting
mixture was heated for 14 h. At the end of this period, the mixture
was cooled to room temperature and concentrated under reduced
pressure. The crude was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:8) furnished 159 mg (R)-5,6-
dihydro-6-(naphthalen-2-yl)pyran-2-one (4) with 92% yield.
Rf = 0.13 (ethyl acetate/hexanes, 1:4). ½a D20
ꢂ
+190.19 (c 1.59, CH2Cl2).
1H NMR (400 MHz, CDCl3) d 7.91–7.82 (m, 4H), 7.54–7.47 (m, 3H),
7.03–6.96 (m, 1H), 6.18 (d, 1H, J = 10.9 Hz), 5.63 (dd, 1H, J = 10.7,
and 5.2 Hz), 2.80–2.64 (m, 2H); 13C NMR (400 MHz, CDCl3) d
164.41, 145.19, 136.13, 133.59, 133.42, 128.46, 128.08, 126.87,
126.83, 125.53, 123.86, 122.13, 105.11, 79.65, 32.08; MS (EI) m/z
calculated for M+ (C15H12O2) = 224.1; found: 224 (50%), 178, 156
(100%), 128, 68; HPLC - Chiracel AD-H column (i-propanol/hexane
5:95, 1 mL/min t1 = 17.66 min ‘major enantiomer’, t2 = 18.27 min
‘minor enantiomer’).
4.1.15. (R)-(+)-1-(4-Methylnaphthalen-1-yl)-but-3-enyl acrylate
(14f)
Purification of the crude product by column chromatography
on silica gel (ethyl acetate/hexane, 1:12) gave 50 mg of (R)-(+)-
1-(4-methylnaphthalen-1-yl)-but-3-enyl acrylate (14f) as a light
yellow oil with 56% yield. Rf = 0.45 (ethyl acetate/hexanes, 1:8);
(½a 3D1
ꢂ
+13.33 (c 2.73, CH2Cl2) was detected for 78% ee in the sec-
ond synthesis); 1H NMR (400 MHz, CDCl3) d 8.21–8.16 (m, 1H),
8.07–8.03 (m, 1H), 7.60–7.52 (m, 2H), 7.48 (d, 1H, J = 7.04 Hz),
7.32 (dd, 1H, J = 7.43 and 0.78 Hz), 6.70–6.65 (m, 1H), 6.46 (dd,
1H, J = 17.22 and 1.56 Hz), 6.20 (dd, 1H, J = 17.22 and 10.56 Hz),
5.88–5.76 (m, 2H), 5.13 (dd, 1H, J = 3.13 and 1.56 Hz), 5.09–5.04
(m, 1H), 2.87–2.81 (m, 2H), 2.69 (d, 3H, J = 0.78 Hz); 13C NMR
4.1.19. (R)-(+)-6-(Quinolin-3-yl)-5,6-dihydro-2H-pyran-2-one
(5)
The crude product was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:6) furnished 80 mg of (R)-(+)-6-
(quinolin-3-yl)-5,6-dihydro-2H-pyran-2-one (5) as a yellow solid
with 62% yield. Rf = 0.11 (ethyl acetate/hexanes, 1:2).
½ ꢂ
a 2D2
(400 MHz, CDCl3)
d
165.36, 134.64, 133.96, 133.56, 132.84,
+205.76 (c 0.78, EtOH). 1H NMR (400 MHz, CDCl3) d 8.92 (d, 1H,
J = 1.96 Hz), 8.26 (s, 1H), 8.12 (d, 1H, J = 8.22 Hz), 7.85 (d, 1H,
J = 8.22 Hz), 7.78–7.72 (m, 1H), 7.62–7.55 (m, 1H), 7.06–6.99 (m,
1H), 6.20 (dd, 1H, J = 9.78 and 1.56 Hz), 5.73–5.66 (m, 1H), 2.79–
2.73 (m, 2H); 13C NMR (400 MHz, CDCl3) d 163.48, 148.26,
148.06, 144.56, 133.30, 131.18, 130.04, 129.28, 127.98, 127.45,
127.26, 121.83, 77.11, 31.52; Enantiomeric excess was found as
97% with HPLC—Chiracel AD-H column (i-propanol/hexane 5:95,
1 mL/min t1 = 27.46 min ‘minor enantiomer’, t2 = 33.19 min ‘major
enantiomer’).
130.85, 130.39, 128.56, 126.02, 125.92, 125.49, 124.92, 123.63,
117.87, 72.51, 40.32, 19.58; Enantiomeric excess was found as
66% with HPLC—Chiracel AD-H column (i-propanol/hexane 1:99,
1 mL/min t1 = 2.80 min ‘major enantiomer’, t2 = 3.16 min ‘minor
enantiomer’).
4.1.16. (R)-(+)-1-(3-Phenoxyphenyl)-but-3-enyl acrylate (14g)
Purification of the crude product by column chromatography on
silica gel (ethyl acetate/hexane, 1:12) gave 61 mg of (R)-(+)-1-(3-
phenoxyphenyl)-but-3-enyl acrylate (14g) as a light yellow oil
with 76% yield. Rf = 0.50 (ethyl acetate/hexanes, 1:8); ½a D21
ꢂ
+28.67
4.1.20. (R)-(+)-6-(Naphthalen-1-yl)-5,6-dihydro-2H-pyran-2-
one (6)
(c 0.43, CH2Cl2); 1H NMR (400 MHz, CDCl3) d 7.38–7.28 (m, 3H),
7.15–7.08 (m, 2H), 7.06–7.00 (m, 3H), 6.92 (ddd, 1H, J = 8.22,
2.35, and 0.78 Hz), 6.43 (dd, 1H, J = 17.22 and 1.56 Hz), 6.16 (dd,
1H, J = 17.22 and 10.17 Hz), 5.90–5.82 (m, 2H), 5.79–5.67 (m,
1H), 5.13–5.05 (m, 2H), 2.73–2.55 (m, 2H); 13C NMR (400 MHz,
CDCl3) d 165.21, 157.27, 156.94, 142.04, 132.92, 130.94, 129.71,
129.70, 128.41, 123.29, 121.22, 118.86, 118.23, 118.06, 116.80,
74.83, 40.72; Enantiomeric excess was found as 75% with HPLC—
Chiracel AD-H column (i-propanol/hexane 1:99, 1 mL/min
The crude product was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:8) furnished 125 mg of (R)-(+)-
6-(naphthalen-1-yl)-5,6-dihydro-2H-pyran-2-one (6) as a light
yellow solid with 75% yield. Rf = 0.14 (ethyl acetate/hexanes, 1:4).
½
a 2D3 +172.88 (c 1.25, CH2Cl2). 1H NMR (400 MHz, CDCl3) d 8.00–
7.82 (m, 3H), 7.71 (d, 1H, J = 7.14 Hz), 7.58–7.45 (m, 3H), 7.09–
ꢂ
6.99 (m, 1H), 6.25–6.17 (m, 2H), 2.84–2.78 (m, 2H); 13C NMR
(400 MHz, CDCl3)
d 164.54, 145.49, 134.07, 133.99, 130.16,
t1 = 4.50 min
enantiomer’).
‘minor
enantiomer’,
t2 = 4.80 min
‘major
129.41, 128.38, 126.85, 126.07, 125.61, 124.39, 122.72, 121.89,
76.71, 31.38; Enantiomeric excess was found as 11% with HPLC—
Chiracel AD-H column (i-propanol/hexane 5:95, 1 mL/min
t1 = 15.50 min ‘major enantiomer’, t2 = 19.50 min ‘minor
enantiomer’).
4.1.17. (S)-(ꢀ)-1-(Naphthalen-2-yl)-but-3-enyl acrylate (16)
Purification of the crude product by column chromatography on
silica gel (ethyl acetate/hexane, 1:8) gave 124 mg of (S)-(ꢀ)-1-
(naphthalen-2-yl)-but-3-enyl acrylate (16) with 73% yield.
4.1.21. (R)-(+)-6-(Quinolin-4-yl)-5,6-dihydro-2H-pyran-2-one
(7)
Rf = 0.63 (ethyl acetate/hexanes, 1:4); ½a D27
ꢀ54.79 (c 1.23, CH2Cl2);
ꢂ
1H NMR (400 MHz, CDCl3) d 7.88–7.70 (m, 4H), 7.53–7.41 (m, 3H),
6.44 (d, 1H, J = 17.3 Hz), 6.24–6.12 (m, 1H), 6.09–6.00 (m, 1H), 5.84
(d, 1H, J = 10.4 Hz), 5.80–5.67 (m, 1H), 5.16–5.00 (m, 2H), 2.85–
2.63 (m, 2H); 13C NMR (400 MHz, CDCl3) d 165.74, 137.64,
133.49, 133.45, 133.44, 131.28, 128.92, 128.65, 128.41, 128.01,
126.56, 126.45, 126.10, 124.62, 118.56, 75.86, 41.00; MS (EI) m/z
calculated for M+ (C17H16O2) = 252,1; found: 252 (2%), 224, 178,
156 (100%), 128, 68; Enantiomeric excess was found as 81% with
HPLC—Chiracel AD-H column (i-propanol/hexane 5:95, 1 mL/min
The crude product was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:8) furnished 9 mg of (R)-(+)-6-
(quinolin-4-yl)-5,6-dihydro-2H-pyran-2-one (7) as a light yellow
solid with 34% yield. Rf = 0.14 (ethyl acetate/hexanes, 1:1). (½a D26
ꢂ
+313.91 (c 0.63, CH2Cl2) was detected for 86% ee in the second syn-
thesis). 1H NMR (400 MHz, CDCl3) d 8.91 (d, 1H, J = 4.70 Hz), 8.15
(dd, 1H, J = 8.61 and 0.78 Hz), 8.01 (dd, 1H, J = 8.61 and 0.78 Hz),
7.72 (ddd, 1H, J = 8.22, 6.65 and 1.17 Hz), 7.61–7.55 (m, 2H),
5.96–5.85 (m, 1H), 5.57–5.52 (m, 1H), 5.27–5.21 (m, 2H), 2.82–
2.74 (m, 1H), 2.58–2.49 (m, 1H); 13C NMR (400 MHz, CDCl3) d
150.33, 149.20, 148.26, 133.73, 130.37, 129.06, 126.57, 125.35,
t1 = 3.21 min
enantiomer’).
‘major
enantiomer’,
t2 = 4.22 min
‘minor

P. Kasaplar et al. / Bioorg. Med. Chem. 17 (2009) 311–318
317
122.76, 119.21, 117.44, 68.85, 42.80, 29.67; Enantiomeric excess
was found as 95% with HPLC—Chiracel AD-H column (i-propanol/
hexane 5:95, 1 mL/min t1 = 6.42 min ‘major enantiomer’, t2 =
7,15 min ‘minor enantiomer’).
105.11, 79.65, 32.08; MS (EI) m/z calculated for M+
(C15H12O2) = 224.1; found: 224 (50%), 178, 156 (100%), 128, 68;
Enantiomeric excess was found as 43% with HPLC—Chiracel AD-H
column (i-propanol/hexane 5:95, 1 mL/min t1 = 17.52 min ‘minor
enantiomer’, t2 = 18.25 min ‘major enantiomer’).
4.1.22. (R)-(+)-6-(2-Methylnaphthalen-1-yl)-5,6-dihydro-2H-
pyran-2-one (8)
4.2. Cell viability assays
The crude product was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:8) furnished 38 mg of (R)-(+)-6-
(2-methylnaphthalen-1-yl)-5,6-dihydro-2H-pyran-2-one (8) as a
light yellow oil with 60% yield. Rf = 0.24 (ethyl acetate/hexanes,
4.2.1. MTT Test for compounds 1a, 4, and 11
Four cell lines including PC-3, DU145, LNCaP, and MCF-7 were
obtained from the ATCC (USA) culture collection. Cells were cul-
tured in RPMI-1640 (Invitrogen, USA) or DMEM (Invitrogen, USA)
supplemented with 5-10% fetal bovine serum (Sigma, USA), by
1:2). ½a 2D7
ꢂ
+136.79 (c 0.31, CH2Cl2). 1H NMR (400 MHz, CDCl3) d
8.22 (d, 1H, J = 8.61 Hz), 7.82 (dd, 1H, J = 7.82 and 1.57 Hz), 7.75
(d, 1H, J = 8.22 Hz), 7.50–7.40 (m, 2 H), 7.29 (d, 1H, J = 8.22 Hz),
7.06 (ddd, 1H, J = 9.78, 6.26, and 1.96 Hz), 6.30 (dd, 1H, J = 13.30
and 4.30 Hz), 6.23 (ddd, 1H, J = 9.78, 2.74, and 1.17 Hz), 3.27–
3.15 (m, 1H), 2.56 (s, 3 H), 2.55–2.44 (m, 1H); 13C NMR
additions of 100 IU/mL penicillin and l lg/mL streptomycin. Cells
were grown in humidified atmosphere with 5% CO2 at 37 °C. Cyto-
toxic effects of compounds were analyzed by MTT assay which is
based on the cellular reduction of the tetrazolium salt 3-(4,5-
dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide (MTT, Sig-
ma Chemicals) to a purple formazan product by mitochondrial
dehydrogenases of viable cells. Cell proliferation was determined
(400 MHz, CDCl3)
d 164.28, 145.70, 133.91, 133.11, 131.03,
129.74, 129.35, 129.32, 128.94, 126.20, 124.89, 124.46, 121.48,
76.58, 29.48, 20.84; Enantiomeric excess was found as 100% with
HPLC—Chiracel AD-H column (i-propanol/hexane 5:95, 1 mL/min
t1 = 21.14 min ‘single peak’).
by adding 0.5 lg/mL per well, prepared as a sterile stock-solution
of 5 mg/mL in Dulbeccos-phosphate-buffered saline (Gibco), di-
luted 1:10 in medium prior to use. Medium was removed 4 h later
4.1.23. (R)-(+)-6-(4-Methylnaphthalen-1-yl)-5,6-dihydro-2H-
pyran-2-one (9)
and blue formazan crystals solubilized in 200 lL 100% dimethyl-
sulfoxate (DMSO) per well. Amounts of blue formazan product
were quantified at 570–690 nm using a microplate reader (Versa-
max, Tunable Microplate Reader, USA). For all cell lines, strong cor-
relations between numbers of cells present and amounts of MTT
formazan product were observed. Each cell type was incubated
with various doses of 1a, 4, and 11 for 72 h at 37 °C and subjected
to MTT assays to measure IC50 values. The data were obtained from
three independent assays using two wells for each assay. Cell via-
bility was calculated as% cell viability.
The crude product was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:8) furnished 27 mg of (R)-(+)-6-
(4-methylnaphthalen-1-yl)-5,6-dihydro-2H-pyran-2-one (9) as a
light yellow solid with 87% yield. Rf = 0.15 (ethyl acetate/hexanes,
1:4). ½a 2D8
ꢂ
+114.64 (c 0.21, CH2Cl2). 1H NMR (400 MHz, CDCl3) d
8.10–8.03 (m, 1H), 8.01–7.95 (m, 1H), 7.61–7.52 (m, 3H), 7.35 (d,
1H, J = 7.04 Hz), 7.06–6.99 (m, 1H), 6.24–6.15 (m, 2H), 2.83–2.76
(m, 2H), 2.71 (s, 1H); 13C NMR (400 MHz, CDCl3) d 164.38,
145.27, 135.44, 132.83, 131.96, 130.03, 126.18, 126.10, 125.64,
125.14, 123.88, 123.01, 121.59, 76.79, 31.08, 19.61; Enantiomeric
excess was found as 93% with HPLC—Chiracel AD-H column (i-pro-
panol/hexane 5:95, 1 mL/min t1 = 14.96 min ‘major enantiomer’,
t2 = 17.64 min ‘minor enantiomer’).
4.2.2. MTT Test for compounds 5–10 and 14b–14g
Human Prostat Cancer (PC-3) cell line was kindly provided by
Assoc. Prof. Kemal S. Korkmaz (Ege University, Engineering Faculty,
Department of Bioengineering), human breast cancer (MCF-7) cell
line was obtained from Og˘uz Bayraktar. PC-3 cells were maintained
in Dulbecco’s modified Eagle’s medium (DMEM) containing 5% fe-
4.1.24. (R)-(+)-6-(3-Phenoxyphenyl)-5,6-dihydro-2H-pyran-2-
one (10)
tal bovine serum (FBS), 1
lin, MCF-7 cell line was maintained in Roswell Park Memorial
Institute-1640 (RPMI-1640) containing 15% FBS (BIO-IND), 1 g/
lg/mL streptomycin/100 IU/mL penicil-
The crude product was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:8) furnished 35 mg of (R)-(+)-6-
(3-phenoxyphenyl)-5,6-dihydro-2H-pyran-2-one (10) as a yellow
l
mL streptomycin/100 IU/mL penicillin incubated at 37 °C in the
dark with 5% CO2 humidified incubator and passaged when they
reached 80–85% confluency. Cells used in experiments were main-
tained from 10th to 20th passages.
solid with 91% yield. Rf = 0.30 (ethyl acetate/hexanes, 1:2). ½a D29
ꢂ
+115.0 (c 0.34, CH2Cl2). 1H NMR (400 MHz, CDCl3) d 7.39–7.30
(m, 3H), 7.17–6.92 (m, 7H), 6.12 (ddd, 1H, J = 9.78, 2.35, and
1.56 Hz), 5.45–5.37 (m, 1H), 2.70–2.55 (m, 2H); 13C NMR
To investigate the cytotoxic activity of the compounds, 95 ll of
(400 MHz, CDCl3)
d
163.80, 157.57, 156.75, 144.74, 140.39,
cell suspension was inoculated into 96-well microculture plates at
1ꢁ 104 cells density per well in culture media containing FBS, pen-
icillin/streptomycin. Compounds were dissolved in dimethyl sulf-
oxide (DMSO) (Sigma, USA), filter sterilized, diluted at the
appropriate concentrations with the culture medium. In all wells,
1% DMSO concentration was fixed. Dilutions of compounds were
freshly prepared before each experiment. After 24 h cultivation
for cell attachment, extracts were added at final concentrations
130.03, 129.80, 123.53, 121.61, 120.69, 118.99, 118.74, 116.40,
78.77, 31.52; Enantiomeric excess was found as 77% with HPLC—
Chiracel AD-H column (i-propanol/hexane 5:95, 1 mL/min
t1 = 14.99 min ‘minor enantiomer’, t2 = 16.82 min ‘major
enantiomer’).
4.1.25. (S)-(ꢀ)-6-(Naphthalen-2-yl)-5,6-dihydro-2H-pyran-2-
one (11)
50, 25, 1, 0.5, 0.1, 0.05, and 0.01 lM for triplicate assay. Cells were
The crude product was purified by column chromatography on
silica gel (ethyl acetate/hexanes, 1:8) furnished 78 mg of (S)-(ꢀ)-6-
(naphthalen-1-yl)-5,6-dihydro-2H-pyran-2-one (11) as a colorless
treated with the extracts for 48 h and cytotoxic effects were deter-
mined by tetrazolium (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl
tetrazolium bromide) (Sigma, USA) based colorimetric assay. This
method depends on the cleavage of tetrazolium salt to purple for-
solid with 73% yield. Rf = 0.13 (ethyl acetate/hexanes, 1:4). ½a D20
ꢂ
ꢀ175.38 (c 0.78, CH2Cl2). 1H NMR (400 MHz, CDCl3) d 7.91–7.82
(m, 4H), 7.54–7.47 (m, 3H), 7.03–6.96 (m, 1H), 6.18 (d, 1H,
J = 10.9 Hz), 5.63 (dd, 1H, J = 10.7 and 5.2 Hz), 2.80–2.64 (m, 2H);
13C NMR (400 MHz, CDCl3) d 164.41, 145.19, 136.13, 133.59,
133.42, 128.46, 128.08, 126.87, 126.83, 125.53, 123.86, 122.13,
mazan crystals by mitochondrial enzymes of metabolically active
29
cells.
Briefly, 4 h before the end of incubation period, medium
of the cells was removed and wells were washed by pre-warmed
phosphate-buffered saline (PBS) to remove any trace of compounds
and to prevent color interference while optical density determina-

318
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tion. MTT stock-solution (5 mg/mL) was diluted at 1:10 ratio into
complete culture media, 100 l of MTT dilution was added into
each well and incubated at 37 °C in humidified atmosphere. After
3.5 h plates were centrifuged at 1800 rpm for 10 min at room tem-
perature to avoid accidental removal of formazan crystals. Crystals
were dissolved with 100 ll DMSO. The absorbance was deter-
mined at 540 nm. Results were represented as percentage cell
viability.
l
Acknowledgments
We thank to Assoc. Prof. Dr. Kemal S. Korkmaz from Ege Univer-
sity, and Biotechnology and Bioengineering Research Central Re-
search Laboratories at Izmir Institute of Technology for their help
in evaluation of MTT tests. This work was supported by TUBITAK
(The Scientific and Technological Research Council of Turkey, Pro-
ject No. 105T429).
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