Synthesis and cytotoxic activity of γ-aryl substituted α-alkylidene-γ-lactones and α-alkylidene-γ-lactams

Article abstract of DOI:10.1016/j.bmc.2008.03.035

A series of 5-aryl-3-alkylidenedihydrofuran-2(3H)-ones 6a-g″ and 11a,b as well as 5-aryl-3-methylidenepyrrolidin-2-ones 10a-c and 12 were synthesized starting from 4-aryl-2-diethoxyphosphoryl-4-oxobutanoates 3a-g. Reaction sequence includes reduction or reductive amination of the carbonyl group, lactonization or lactamization step and finally the Horner-Wadsworth-Emmons olefination of aldehydes using thus obtained 5-aryl-3-diethoxyphosphoryl-3,4-dihydrofuran-2(5H)-ones 5a-g″ or 5-aryl-3-diethoxyphosphorylpyrrolidin-2-ones 9a-c. Furanones 6 and 11, as well as pyrrolidinones 10 and 12, were evaluated in vitro against mouse leukemia cell line L-1210 and two human leukemia cell lines HL-60 and NALM-6. Several of the obtained furanones proved to be very potent against all three cell lines with IC₅₀ values lower than 6 μM. Structure-activity relationships of these compounds, as well as 5-alkyl or 5-arylmethyl-3-methylidenedihydrofuran-2(3H)-ones 13a-e, previously obtained in our laboratory, are discussed.

Full text of DOI:10.1016/j.bmc.2008.03.035

Available online at www.sciencedirect.com
Bioorganic & Medicinal Chemistry 16 (2008) 4872–4882
Synthesis and cytotoxic activity of c-aryl substituted
a-alkylidene-c-lactones and a-alkylidene-c-lactams
a
a
a
b
´ _
Anna Albrecht, Jacek F. Koszuk, Jakub Modranka, Marek Rozalski,
Urszula Krajewska,b Anna Janecka,c Kazimierz Studzianc and Tomasz Janeckia,*
aInstitute of Organic Chemistry, Technical University of Ło´dz´, Zeromskiego 116, 90-924 Ło´dz´, Poland
bDepartment of Pharmaceutical Biochemistry, Faculty of Pharmacy, Medical University of Ło´dz´,
Muszyn´skiego 1, 90-151 Ło´dz´, Poland
cLaboratory of Biomolecular Chemistry, Medical University of Ło´dz´, Mazowiecka 6/8, 92-215 Ło´dz´, Poland
Received 6 February 2008; revised 4 March 2008; accepted 14 March 2008
Available online 17 March 2008
Abstract—A series of 5-aryl-3-alkylidenedihydrofuran-2(3H)-ones 6a–g00 and 11a,b as well as 5-aryl-3-methylidenepyrrolidin-2-ones
10a–c and 12 were synthesized starting from 4-aryl-2-diethoxyphosphoryl-4-oxobutanoates 3a–g. Reaction sequence includes reduc-
tion or reductive amination of the carbonyl group, lactonization or lactamization step and finally the Horner–Wadsworth–Emmons
olefination of aldehydes using thus obtained 5-aryl-3-diethoxyphosphoryl-3,4-dihydrofuran-2(5H)-ones 5a–g00 or 5-aryl-3-diethoxy-
phosphorylpyrrolidin-2-ones 9a–c. Furanones 6 and 11, as well as pyrrolidinones 10 and 12, were evaluated in vitro against mouse
leukemia cell line L-1210 and two human leukemia cell lines HL-60 and NALM-6. Several of the obtained furanones proved to be
very potent against all three cell lines with IC50 values lower than 6 lM. Structure–activity relationships of these compounds, as well
as 5-alkyl or 5-arylmethyl-3-methylidenedihydrofuran-2(3H)-ones 13a–e, previously obtained in our laboratory, are discussed.
ꢀ 2008 Elsevier Ltd. All rights reserved.
1. Introduction
line A, were found to have significant pharmacological
activities.1,11,12 Also, the a-alkylidene-c-lactam moiety
2 is present in natural13,14 and synthetic compounds
which exhibit moderate cytotoxic activity.15,16
a-Alkylidene-c-lactone skeleton 1 is the active constitu-
ent of many natural and synthetic compounds exhibiting
pronounced biological properties, such as antimicrobial,
cardiovascular, antifungal, anti-inflammatory and, in
particular, cytotoxic activity.1–5 It was demonstrated,
that compounds containing this moiety can act as the
Michael-type acceptors in the reaction with mercapto
groups of bionucleophiles, especially those present in
the cysteine residue.1,6 More recently it was shown that
a-methylidene-c-lactones 1 have an interesting photore-
activity potential and can form intramolecular photoad-
ducts with psoralens7 and intra or intermolecular
photoadducts with thymine.8–10 The biological activity
of these compounds is not restricted to the highly func-
tionalized sesquiterpene lactones. Many simple natural
or synthetic lactones of this structure, including tulipa-
a-Alkylidene-c-lactones and lactams are also valuable
synthetic intermediates wildly employed in organic syn-
thesis. Apart from being excellent Michael acceptors17,18
they can act as dipolarophiles in 1,3-dipolar cycloaddi-
tions,19 be partners in cross methathesis reactions20
and be utilized in the synthesis of many kinds of natural
products and biologically important substances.21,22
Not surprisingly, a variety of methodologies for their
synthesis have been reported in the literature and the
number of publications dedicated to this subject is stea-
dily increasing. The most common methodology is the
reaction of allyl derivatives, mainly metal derivatives
Keywords: a-Alkylidene-c-lactones; a-Alkylidene-c-lactams; Horner–
Wadsworth–Emmons olefination; 1H, 13C 31P NMR; Cytotoxic
activity.
*
Corresponding author. Tel.: +48 42 6313220; fax: +48 42 6365530 e-
mail: tjanecki@p.lodz.pl
0968-0896/$ - see front matter ꢀ 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2008.03.035

A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
4873
of 2-alkoxycarbonylallyl, with carbonyl compounds fol-
2. Chemistry
lowed by intramolecular cyclization.23–26 An interesting
variant of this method is the intramolecular Hosomi-
Sukurai reaction of 2-(ethoxycarbonyl)allylsilanes and
related functionalized allylsilanes with aldehydes.27
Another elegant approach is the Pd-catalyzed, homoge-
neous intramolecular alkoxy-carbonylation of propargyl
Target furanones 6a–g00 and pyrrolidinones 10a–c were
synthesized starting from the corresponding 4-aryl-
2-diethoxyphosphoryl-4-oxobutanoates 3a–g. These
substrates can be efficiently prepared from 1-aryl-2-bro-
moalkan-1-ones and ethyl diethoxyphosphorylacetate,
applying the methodology which has been recently
worked out in our laboratory.40 Oxobutanoates 3e–g
(R1 = Me) were used as mixtures of diastereomers in
close to 60:40 ratio.
or homopropargyl alcohols.28 Alkenylalumination of
29
oxiranes
and other methods were also devel-
oped.1,30–32 Several approaches to a-methylidene-c-lac-
tams were also reported.33,34
Quite recently, yet another methodology, which employs
the Wittig or Horner–Wadsworth–Emmons olefination
for the introduction of the alkylidene moiety onto c-lac-
tone or c-lactam ring has emerged as a very versatile and
promising tool.35 Using this approach we synthesized a
variety of 3-alkylidenedihydrofuran-2(3H)-ones,36,37 3-
methylidenepyrrolidin-2-ones16,38 as well as 4-methy-
lideneisoxazolidin-5-ones.39
Reduction of the carbonyl group in oxobutanoates 3a–g
followed by spontaneous lactonization of the initially
formed 5-aryl-2-diethoxyphosphoryl-4-hydroxybutano-
ates 4a–g, gave, after standard work up, crude 5-aryl-
3-diethoxyphosphoryl-3,4-dihydrofuran-2(5H)-ones 5a–
g, as mixtures of two diastereomers, in the ratios shown
in Table 1 (Scheme 1). These compounds were then puri-
fied and dihydrofuranones 5e–g also separated into sin-
gle diastereomers by column chromatography. Yields
1
Herein, we demonstrate further application of this meth-
odology, this time in the synthesis of a series of 5-aryl-3-
alkylidenedihydrofuran-2(3H)-ones 6a–g00, 11a,b as well
as 5-aryl-3-methylidenepyrrolidi-2-nones 10a–c, 12. Fur-
thermore, all target compounds were evaluated for their
cytotoxic activity against the mouse leukemia cell line L-
1210 and two human leukemia cell lines NALM-6 and
HL-60. Synthesis of 5-aryl substituted 3-methylidenefu-
ran-2-ones was particularly attractive in view of the
cytotoxicity evaluations of 5-alkyl and 5-arylmethyl
substituted 3-methylidenefuran-2-ones, performed re-
cently in our laboratory.16 According to these evalua-
tions 5-arylmethyl substituted methylidenefuranones
had remarkably higher cytotoxicities against NALM-6
cell line than their 5-alkyl analogs. Current investiga-
tions open up the opportunity to check whether the
presence of an aryl group connected directly to the lac-
tone ring would also enhance cytotoxicity. Therefore,
structure–activity relationships of the newly obtained
compounds, in comparison with 5-alkyl and 5-aryl-
methyl-3-methylidenedihydrofuran-2(3H)-ones, previ-
ously obtained in our laboratory, will be discussed.
are given in Table 1. Analysis of IR, H, 13C and 31P
NMR spectra of dihydrofuranones 5a–g confirmed their
structures unambiguously.
It is worth to stress that dihydrofuranones 5e–g were
formed as mixtures of only two, out of four possible dia-
stereomers. Reasonable explanation of this observation
was epimerization on the C3 carbon atom in the
strongly basic conditions of the reaction and the forma-
tion of more stable diastereomers with trans alignment
of phosphoryl and methyl groups. Careful analysis of
1
the well resolved signals of these stereoisomers in H
and 13C NMR spectra confirmed this supposition and
also allowed us to propose their relative configuration.
Particularly characteristic were the chemical shifts of
the protons of the methyl group and protons H5, as well
3
3
3
as coupling constants J(P-CH3), J(P-C5), J(H3–H4)
and J(H4–H5). These values are given in Table 2. Pro-
3
tons of the methyl groups of the minor diastereomers
adsorbed at the unexpectedly low frequency, for exam-
ple, in 5f the methyl protons of the major and minor dia-
stereomer had chemical shift 1.28 ppm and 0.76 ppm,
Table 1. Synthesis of 3,4-dihydrofuran-2(5H)-ones 5a–g00, methylidenedihydrofuran-2-ones 6a–g00, pyrrolidin-2-ones 9a–c and methylidenepyrroli-
din-2-ones 10a–c
Ar
R1
5
6
9
10
Yielda (%)
Diastereomers ratiob
Yielda (%)
6/7 ratio
Yielda (%)
Diastereomers ratioc
Yielda (%)
a
Ph
H
86
86
73
90
55
30
40
50
47
38
60:40
60:40
60:40
60:40
65:35
55
45
61d
30
66
65
52
51
61
66
>99:1
>99:1
60:40
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
77
92
58
—
—
70:30
60:40
60:40
—
79
65
59
—
—
b
4-BrC6H4
4-MeOC6H4
1-Naphthyl
Ph
H
c
H
d0
H
Me
e
—
e00
f0
f00
g
4-BrC6H4
Me
Me
55:45
55:45
—
—
—
—
—
—
4-MeOC6H4
g00
a Yield of isolated, pure product based on 3, 5 or 9, respectively.
b Taken from 31P NMR of the crude product.
c Taken from 1H NMR of the crude product.
d Overall yield for 6c and 7c.

4874
A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
Scheme 1.
Table 2. Selected chemical shifts and coupling constants for (r-3,t-4,t-5)-5e0–g0 and (r-3,t-4,c-5)-5e00–g00
d (1H) H5 (ppm)
d (1H) CH3 (ppm)
3J(P-CH3) (Hz)
3J(P-C5) (Hz)
3J(H3–H4) (Hz)
3J(H4–H5) (Hz)
(r-3,t-4,c-5)-5e0
(r-3,t-4,t-5)-5e00
4.86
1.28
1.2
(ꢀ90ꢁ)
13.9
(150–160ꢁ)
3.7
11.0
(150–160ꢁ)
3.9
6.6
(160–170ꢁ)
6.6
5.86
0.74
0
(110–120ꢁ)
(130–140ꢁ)
14.5
3.7
(120–130ꢁ)
11.0
3.5
(10–20ꢁ)
9.0
6.3
(r-3,t-4,c-5)-5f0
(r-3,t-4,t-5)-5f00
(r-3,t-4,c-5)-5g0
(r-3,t-4,t-5)-5g00
4.82
5.82
4.86
5.84
1.28
0.76
1.25
0.78
0
0
0
0
14.5
4.3
11.4
3.5
9.2
6.6
1
respectively. This anomaly can be rationalized by
assuming the cis arrangement of the methyl and aro-
matic groups in the minor diastereomers. In this
arrangement the methyl protons are placed in the shield-
ing area of the benzene ring. Furthermore, chemical
shifts of the H5 protons in the spectra of the minor dia-
stereomers were surprisingly high, for example, in 5f
these shifts were 5.82 and 4.82 ppm for the minor and
major diastereoisomers, respectively. This, in turn can
be explained by the deshielding effect of the diethoxy-
phosphoryl group exerted on the cis-oriented proton
H5. These observations allowed us to assign the r-3,t-
4,c-5 and r-3,t-4,t-5 configurations for the major and
minor diastereomers of 5e–g, respectively. Also, cou-
pling constants 3J(P-CH3), 3J(P-C5), 3J(H3–H4) and
3J(H4–H5) validated this assignment. Dihedral angles
estimated from these coupling constants, using Karplus
equation,41,42 had values given in parentheses in Table 2
and were in good agreement with the dihedral angles ta-
ken from the corresponding cochranes orbit size molec-
ular models of (r-3,t-4,c-5)-5e0–g0 and (r-3,t-4,t-5)-5e00–
g00, in which the diethoxyphosphoryl and aryl groups
were assumed to occupy pseudo-equatorial positions.
Data from the H and 13C NMR spectra of the diaste-
reomeric mixtures of dihydrofuranones 5a–d were less
useful for the configurational assignments. However,
based on the correlation described above, mainly desh-
ielding effect of the diethoxyphosphoryl group, the trans
configuration was assigned to the major diastereomers
in which proton H5 had higher chemical shift, for exam-
ple, for 5a these shifts were 5.71 ppm and 5.44 ppm for
the major and minor diastereomers, respectively.
Dihydrofuranones 5a–g00 were next used in the Horner–
Wadsworth–Emmons olefination of formaldehyde.
Reaction of these compounds with paraformaldehyde
in the presence of t-BuOK as a base gave, after standard
work-up, crude 5-aryl-3-methylidene-4,5-dihydrofuran-
2-ones 6a–g00, which were purified by column chroma-
tography (Scheme 1 and Table 1). Only the reaction of
furanone 5c gave the mixture of methylidenefuranone
6c and its rearrangement product 7c. Our efforts to sep-
arate this mixture were unsuccessful. Reason for the fac-
ile rearrangement of 6c are not fully understood.
Structures of all synthesized compounds were unequivo-
cally confirmed by their IR, H, and 13C spectra. As ex-
1
pected, methylidenedihydrofuranones 6e0–g00 were
obtained as single diastereomers with preserved trans
or cis configuration of the starting dihydrofuranones
Correctness of the above configurational assignments
was unambiguously confirmed by the NOE experiments
performed on both diastereoisomers of 5f. Obtained re-
sults are shown in Figure 1.
1
5e0–g00, for example, H NMR spectra of all cis-6e00–g00
revealed characteristic low-frequency absorption of the

A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
4875
the diagnostic deshielding effect of the carbonyl group
exerted on the cis-oriented vinyl proton.41,43 Opposite
E/Z stereochemistry observed for 11a and 11b (15:85
and >99:1, respectively), although surprising at first,
can be rationalized taking into account conjugating abil-
ity of the phenyl group. Inspection of the corresponding
molecular models revealed that in (Z)-11b thermo-
dynamically preferred coplanar arrangement of phenyl
and a,b-unsaturated lactone moieties causes severe steric
repulsions between phenyl and carbonyl groups. There-
fore, more stable (E) stereoisomer is formed exclusively.
In (Z)-11a the isopropyl group can adopt conformation
lacking significant steric interactions, due to free
rotation about the bond connecting this group to the
unsaturated system.
Figure 1. NOE experiments performed on diastereomeric dihydrof-
uranones 5f0 and 5f00.
methyl group (0.79–0.88 ppm) caused by the shielding
effect of the cis-oriented aryl group.
On the other hand, reductive amination of oxobutano-
ates 3a–c using methylamine along with titanium (IV)
isopropoxide, followed by addition of sodium borohy-
dride, standard work up and purification by column
chromatography, furnished pure 5-aryl-3-diethoxyphos-
phoryl-1-methylpyrrolidin-2-ones 9a–c in good to excel-
lent yields (Scheme 1 and Table 1). Disappointingly,
oxobutanoate 3d treated the same way gave only 20%
yield of the pyrolidinone 9d along with substrate and
other products which were difficult to separate. Also
oxobutanoates 3e–g did not give expected pyrrolidinon-
es but only difficult to analyze mixtures of products.
Pyrrolidinones 9a–c were obtained as mixtures of diaste-
3. Pharmacological results
All target compounds 6a,b,d–g00, 10a–c, 11a,b, 12 were
evaluated in vitro against mouse leukemia cell line
L-1210 and two human leukemia cell lines HL-60 and
NALM-6. Cytotoxic activity of these compounds is ex-
pressed as the concentration (lM) required to inhibit tu-
mor cell proliferation by 50% after a 48 h exposure of
the cells to a tested compound (IC50 values). Results are gi-
ven in Table 4. Cytotoxicities of 5-alkyl and 5-arylmethyl-
3-methylidene-dihydrofuran-2(3H)-ones 13a–e prepared
recently in our laboratory are also given for comparison.
Carboplatin was used as a reference compound.44
1
reomers in the ratios given in Table 1. IR, H, 13C and
31P NMR spectra of 9a–c confirmed their structures
but were not conclusive enough to attribute the relative
configurations to the major and minor diastereomers.
Olefination of formaldehyde using pyrrolidinones 9a–c
and NaH as a base gave, after work up and column
chromatography, expected 5-aryl-3-methylidenepyrroli-
din-2-ones 10a–c in good yields (Table 1).
Dihydrofuranone 5a and pyrrolidinone 9a were also
used in the olefination of isobutyraldehyde or benzalde-
hyde (Scheme 2). Applying standard procedure (NaH,
THF) and work up, followed by purification by column
chromatography, 3-alkylidene-5-phenyldihydrofuran-2-
ones 11a,b and 3-(2-methylpropylidene)-5-phenylpyrr-
olidin-2-one 12 were obtained in good yields as a
mixture of E and Z diastereoisomers or as single isomers
(Table 3). Configurational assignments were made using
Presented results are very encouraging because four of
the obtained furanones, 6d, 6e00, 6f0 and 6g0 showed
IC50 values against all three tested cell lines lower than
8.09 lM and can be considered highly potent according
to the Kupchan’s classification (IC50 6 15 lM).45
Several conclusions, which can be drawn from the data
given in Table 4 confirm the observations described in
our recent paper16 where cytotoxicities of 5-alkyl or 5-
arylmethylfuranones 13a–e and other 5-alkyl or 5-aryl-
methylfuran-2-ones and pyrrolidin-2-ones were tested.
These conclusions can be summarized as follows: (i)
the cytotoxicities of methylidenefuranones 6a–g00 are
much higher than methylidenepyrrolidin-2-ones 10a–c,
(ii) the activities of methylidenefuranone 6d and methy-
lidenepyrrolidin-2-one 10a are evidently higher than the
activities of alkylidenefuranones 11a,b and isopro-
Scheme 2.
Table 3. Synthesis of furanones 11a,b and pyrrolidinone 12
Compound
X
R2
Yielda (%)
E/Zb
11a
11b
12
O
i-Pr
Ph
88
50
59
15:85
>99:1
<1:99
O
NMe
i-Pr
a Yield of isolated, pure product based on 5a or 9a, respectively.
b Taken from 1H NMR of the crude product.

4876
A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
Table 4. Cytotoxic Activity of compounds 6a,b,d–g00, 10a–c, 11a,b, 12
and 13a–e
and 3-alkylidene-5-arylpyrrolidin-2-ones 10a–c, 12 was
achieved starting from easily available intermediates—
a
4-aryl-2-diethoxyphosphoryl-4-oxobutanoates
3a–g.
Compound
Cytotoxicity IC50 (lM)
Furthermore, 3-methyl substituted furanones 6e0–g00
were obtained as pure trans and cis stereoisomers. Rela-
tive configurations of all diastereomers were assigned
using 1H and 13C NMR analysis, including NOE exper-
iments. Several of the target 5-arylfuranones 6d,e00,f0,g0
proved to be highly potent against L-1210, HL-60 and
NALM-6 cell lines with the activity comparable to or
higher than 5-arylmethylfuranones 13d,e previously pre-
pared in our laboratory and much higher than the activ-
ity of 5-alkylfuranones 13a–c. Moreover, significant
differences in the cytotoxicities of trans-6f0,g0 and cis-
6f00,g00 were found, with trans isomers being eight times
more active than cis isomers.
L-1210
HL-60
NALM-6
6a
6b
1.4 0.12
1.3 0.10
4.3 0.24
28.0 1.92
4.0 0.21
1.55 0.05
7.5 0.33
3.65 0.35
14.2 2.12
>50
36.9 13.6
20.3 2.6
4.42 0.52
8.97 0.36
8.09 0.6
5.05 0.28
41.8 7.3
5.69 0.1
37.9 6.7
988.7 19.3
220.1 27.9
611.3 18.2
158.9 44.6
>1000
9.13 0.34
85.3 8.0
3.86 0.49
7.91 0.37
5.42 0.44
4.02 0.24
43.9 6.8
5.23 0.46
38.6 6.6
552.9 46.9
141.4 26.9
522.6 21.0
482.9 42.3
497 38.6
351.1 31.8
41.0 1.8
51.6 24.0
23.6 12.9
5.4 0.3
6d0
6e
6e000
6f
6f000
6g
6g00
10a
10b
10c
>50
>50
11a
11b
>50
>50
12
13ab
>50
81.3 6.8
77.4 6.5
39.5 17.3
99.4 31.5
42.7 11.1
46.3 1.8
2.9 0.1
5. Experimental
5.1. Chemistry
32.5 4.8
6.0 1.6
20.0 3.2
15.5 2.9
4.3 0.8
9.7 1.2
13bb
13cb
13db
13eb
Carboplatin 14
6.0 1.4
0.7 0.3
Organic solvents and reagents were purified by the
appropriate standard procedures. Column chromatog-
raphy was performed on FLUKAꢂ silica gel 60 (230–
400 mesh). IR spectra were recorded on Specord M 80
spectrometer. 1H NMR (250 MHz), 13C NMR
(62.9 MHz), and 31P NMR (101 MHz) spectra were re-
corded on a Bruker DPX-250 spectrometer with TMS
a IC50, 50% inhibitory concentration represents the mean from dose–
response curves of at least three experiments.
b Data taken from Ref. 16.
pylidenepyrrolidinone 12, respectively, (iii) cytotoxicities
of methylidenefuranones 6a,b,d–g00, against L-1210 cell
line are generally higher than against HL-60 or
NALM-6 cell lines.
1
as an internal standard for H NMR and 13C NMR,
and 85% H3PO4 as an external standard for 31P NMR.
31P NMR spectra were recorded using broad-band pro-
ton decoupling. NOE experiments were performed on
Bruker Avance II Plus (700 MHz) spectrometer.
Our studies also show that 5-aryl or 5-arylmethyl substi-
tuted furanones are more potent antiproliferative agents
than 5-alkyl analogs, for example, activities of 6a and
13d, which differ only by the methylene group (phenyl
and methylphenyl substituents, respectively), against
HL-60 and NALM-6 cell lines are very similar and
much higher than activities of 13a (methyl substituent)
against the same cell lines. This observation indicates
that the presence of an aryl substituent in position 5,
whether attached directly to the furanone ring or
through the methylene tether, is very important for the
activity. However, cytotoxicities of 5-aryl substituted
furanones 6a–g00 against HL-60 cell lines are generally
considerably higher than the cytotoxicities of 5-arylm-
ethylfuranones 13d,e. The highest cytotoxicity against
both, HL-60 and NALM-6 cell lines was found for 6d
having a bulk naphthyl ring in position 5. Comparison
of the cytotoxicities of the diastereomeric 4-methyl-5-
aryl substituted furanones 6f0 and 6f00 as well as 6g0
and 6g00 shows another, very interesting relationship:
trans-furanones 6f0,g0 are significantly more potent than
the cis stereoisomers 6f00,g00. Evidently, the spatial
arrangement of the substituents plays an important role
in the interaction with the bionucleophiles.
5.1.1. General procedure for the preparation of 5-aryl-3-
diethoxyphosphoryl-2-furanones (5a–g). To a stirred
solution of 2-dietoxyphosphoryl-4-oxoalkanoates (3a–
g) (5.0 mmol) in methanol (20 mL) potasium borohy-
dride (0.405 g, 7.5 mmol) was added at 0 ꢁC. Stirring
was continued for appropriate period of time. The
resulting mixture was acidified to pH 1.5 with concen-
trated HCl, then the water (15 mL) was added and
methanol was evaporated under reduced pressure. The
residue was extracted with chloroform (4· 20 mL).
The combined organic layers were washed with water
(20 mL) and dried (MgSO4). Evaporation of the solvent
under reduced pressure afforded a crude product which
was purified by column chromatography (CHCl3/ace-
tone, 98:2) affording pure product.
5.1.1.1. 3-Diethoxyphosphoryl-5-phenyl-dihydrofuran-
2(3H)-one (5a). Oil, yield = 86%; IR (film, cmꢁ1): 1772,
1516, 1168, 1024; 1H NMR (250 MHz, CDCl3):
d = 1.13–1.41 (m, 6H major and minor, (CH3CH2O)2
P(O)), 2.35–2.70 (m, 1H major and minor, H-3), 2.80–
3.20 (m, 1H major and minor, H-4), 3.20–3.49 (m, 1H ma-
jor and minor, H-4), 3.80–4.27 (m, 4H major and minor,
(CH3CH2O)2P(O)),
5.44
(dd,
3JHH = 6.5 Hz,
3JHH = 9.7 Hz, 1H minor, H-5), 5.71 (dd, 3JHH = 7.0 Hz,
3JHH = 8.9 Hz, 1H major, H-5), 7.34–7.37 (m, 5H major
and minor, H-Ar); 13C NMR (62.9 MHz, CDCl3):
4. Conclusions
Simple and effective synthesis of biologically important
3-alkylidene-5-aryldihydrofuran-2-ones 6a–g00, 11a,b
3
d = 16.05 (d, JPC = 5.9 Hz, CH3CH2O, CH3CH2O),

A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
4877
32.98 (d, 2JPC = 3.1 Hz, C-4), 33.04 (d, 2JPC = 4.4 Hz, C-
4), 39.83 (d, 1JPC = 152.1 Hz, C-3), 39.94 (d,
1JPC = 138.7 Hz, C-3), 62.65 (d, 2JPC = 6.2 Hz,
C-Ar), 129.85 (s, C-Ar), 130.05 (s, C-Ar), 159.61 (s, C-
Ar), 159.70 (s, C-Ar), 170.94 (d, JPC = 2.3 Hz, C-2),
2
171.13 (d, JPC = 4.4 Hz, C-2); 31P NMR (101 MHz,
2
2
CH3CH2O), 62.77 (d, JPC = 6.9 Hz, CH3CH2O), 63.13
(d, JPC = 6.9 Hz, CH3CH2O), 63.41 (d, JPC = 6.9 Hz,
CDCl3): d = 20.65 minor, 20.85 major; (40:60); Anal.
Calcd for C15H21O6P: C, 54.88; H, 6.45. Found: C,
54.78; H, 6.50.
2
2
3
CH3CH2O), 79.97 (d, JPC = 12.0 Hz, C-5), 80.16 (d,
3JPC = 3.1 Hz, C-5), 125.07 (s, 2· C-Ar), 125.44 (s, 2·
C-Ar), 128.34 (s, C-Ar, C-Ar), 128.43 (s, 2· C-Ar),
128.49 (s, 2· C-Ar), 138.10 (s, C-Ar), 138.32 (s, C-Ar),
5.1.1.4. 3-Diethoxyphosphoryl-5-(1-naphtyl)-dihydrofu-
ran-2(3H)-one (5d). Oil, yield = 90%; IR (film, cmꢁ1):
1776, 1512, 1392, 1368, 1260, 1164, 1028; 1H NMR
(250 MHz, CDCl3): d = 1.30–1.45 (m, 6H major and min-
or, (CH3CH2O)2P(O)), 2.42–2.70 (m, 1Hmajorand minor,
H-3), 3.05–3.50 (m, 2H major and minor, H-4), 4.10–4.45
(m, 4H major and minor, (CH3CH2O)2P(O)), 6.12 (dd,
2
170.98 (d, JPC = 2.3 Hz, C-2), 171.16 (d, 2JPC = 4.4 Hz,
C-2); 31P NMR (101 MHz, CDCl3): d = 20.84 minor,
21.08 major; (40:60); Anal. Calcd for C14H19O5P: C,
56.37; H, 6.42. Found: C, 56.41; H, 6.36.
3
5.1.1.2. 5-(4-Bromophenyl)-3-diethoxyphosphoryl-
dihydrofuran-2(3H)-one (5b). Oil, yield = 86%; IR (film,
cmꢁ1): 1770, 1512, 1168, 1020; 1H NMR (250 MHz,
CDCl3): d = 1.12–1.50 (m, 6H major and minor,
(CH3CH2O)2P(O)), 2.25–2.60 (m, 1H major and minor,
H-3), 2.82–3.10 (m, 1H major and minor, H-4), 3.10–
3.44 (m, 1H major and minor, H-4), 4.05–4.45 (m, 4H
major and minor (CH3CH2O)2P(O)), 5.40 (dd,
3JHH = 7.0 Hz, JHH = 8.2 Hz, 1H minor, H-5), 6.43 (t,
3JHH = 7.0 Hz, 1H major, H-5), 7.32–7.60 (m, 4H major
and minor, H-Ar), 7.70–7.95 (m, 3H major and minor,
H-Ar); 13C NMR (62.9 MHz, CDCl3): d = 16.23 (d,
3JPC = 4.9 Hz, CH3CH2O, CH3CH2O), 32.44 (d,
2JPC = 3.7 Hz, C-4, C-4), 39.36 (d, 1JPC = 141.5 Hz, C-3),
1
2
39.88 (d, JPC = 151.6 Hz, C-3), 62.66 (d, JPC = 6.9 Hz,
2
CH3CH2O), 62.84 (d, JPC = 6.9 Hz, CH32CH2O), 63.17
(d, JPC = 6.2 Hz, CH3CH2O), 63.53 (d, JPC = 6.2 Hz,
CH3CH2O), 77.60 (d, JPC = 4.9 Hz, C-5), 77.73 (d,
3
2
3JHH3 = 7.5 Hz, JHH = 10.0 Hz, 1H minor, H-5), 5.66
3
(t, JHH = 7.5 Hz, JHH = 10.0 Hz, 1H major, H-5),
7.20–7.23 (m, 2H major and minor, H-Ar), 7.51–7.60
3
3JPC = 1.9 Hz, C-5), 121.40 (s, C-Ar, C-Ar), 122.19 (s, C-
Ar), 122.26 (s, C-Ar), 125.09 (s, C-Ar), 125.16 (s, C-Ar),
125.69 (s, C-Ar), 125.83 (s, C-Ar), 126.38 (s, C-Ar),
126.50 (s, C-Ar), 128.74 (s, C-Ar), 128.76 (s, C-Ar),
128.79 (s, C-Ar), 128.87 (s, C-Ar), 129.20 (s, C-Ar),
129.34 (s, C-Ar), 133.47 (s, C-Ar), 133.52 (s, C-Ar),
133.88(s, C-Ar), 134.08(s, C-Ar), 171.36(d, 2JPC = 3.7 Hz,
C-2, C-2); 31P NMR (101 MHz, CDCl3): d = 20.36 minor,
20.89 major; (40:60); Anal. Calcd for C18H21O5P: C, 62.07;
H, 6.08. Found: C, 62.13; H, 6.00.
(m, 2H major and minor, H-Ar); 13C NMR
3
(62.9 MHz, CDCl3): d = 16.14 (d, JPC = 6.7 Hz,
CH3CH2O, CH3CH2O), 32.89 (d, JPC = 3.1 Hz, C-4),
2
33.11
(d,
2JPC = 3.1 Hz,
C-4),
39.88
(d,
1
1JPC = 153.97 Hz, C-3), 40.00 (d, JPC = 138.12 Hz, C-
3), 62.68 (d, JPC = 6.9 Hz, CH3CH2O), 62.93 (d,
2
2JPC = 6.2 Hz, CH3CH2O), 63.36 (d, JPC = 6.2 Hz,
CH3CH2O), 63.61 (d, JPC = 6.2 Hz, CH3CH2O), 79.24
2
2
3
3
(d, JPC = 11.9 Hz, C-5), 79.55 (d, JPC = 2.5 Hz, C-5),
122.37 (s, C-Ar), 122.50 (s, C-Ar), 126.90 (s, 2· C-Ar,
2· C-Ar), 127.24 (s, C-Ar), 131.73 (s, 2· C-Ar), 137.32
(s, C-Ar), 137.48 (s, C-Ar, C-Ar), 170.82 (d,
5.1.1.5. r-3-Diethoxyphosphoryl-t-4-methyl-c-5-phe-
nyl-dihydrofuran-2(3H)-one (5e0). Oil, yield = 55%; IR
2
1
2JPC = 2.3 Hz, C-2), 171.00 (d, JPC = 4.4 Hz, C-2); 31P
(film, cmꢁ1): 1776, 1456, 1256, 1160, 1024; H NMR
3
NMR (101 MHz, CDCl3): d = 20.44 minor, 20.46 ma-
jor; (40:60); Anal. Calcd for C14H18BrO5P: C, 44.58;
H, 4.81. Found: C, 44.54; H, 4.79.
(250 MHz, CDCl3): d = 1.28 (d, JHH = 6.4 Hz, 3H,
CH3), 1.29–1.41 (m, 6H, (CH3CH2O)2P(O)), 2.65–2.98
(m, 1H, H-4), 2.94 (dd, 3JHH = 11.0 Hz, 2JHP = 28.5 Hz,
1H, H-3), 4.09–4.37 (m, 4H, (CH3CH2O)2P(O)), 4.86 (d,
3JHH = 6.6 Hz, 1H, H-5), 7.33–7.40 (m, 5H, H-Ar); 13C
NMR (62.9 MHz, CDCl3): d = 15.93 (d, 3JPC = 1.24 Hz,
5.1.1.3. 3-Diethoxyphosphoryl-5-(4-methoxyphenyl)-
dihydrofuran-2(3H)-one (5c). Oil, yield = 73%; IR (film,
cmꢁ1): 1768, 1512, 1168, 1028; 1H NMR (250 MHz,
CDCl3): d = 1.20–1.45 (m, 6H major and minor,
(CH3CH2O)2P(O)), 2.25–2.60 (m, 1H major and minor,
H-3), 2.75–3.10 (m, 1H major and minor, H-4), 3.20–
3.40 (m, 1H major and minor, H-4), 3.81 (s, CH3O),
4.10–4.32 (m, 4H major and minor, (CH3CH2O)2P(O)),
5.37 (dd, 3JHH = 6.3 Hz, 3JHH = 10.1 Hz, 1H minor, H-
3
CH3), 16.15 (d, JPC = 5.0 Hz, CH3CH2O), 16.33 (d,
2
3JPC = 5.0 Hz, CH3CH2O), 41.97 (d, JPC = 2.5 Hz, C-
4), 47.03 (d, 1JPC = 150.9 Hz, C-3), 62.45 (d,
2
2JPC = 6.9 Hz, CH3CH2O), 63.37 (d, JPC = 6.9 Hz,
CH3CH2O), 87.16 (d, JPC = 13.9 Hz, C-5), 126.23 (s,
3
2· C-Ar), 128.50 (s, 2· C-Ar), 128.86 (s, C-Ar), 136.89
(s, C-Ar), 170.70 (s, C-2); 31P NMR (101 MHz, CDCl3):
d = 20.49; Anal. Calcd for C15H21O5P: C, 57.69; H, 6.78.
Found: C, 57.80; H, 6.79.
3
3
5), 5.66 (t, JHH = 6.3 Hz, JHH = 9.0 Hz, 1H major, H-
5), 6.81–7.01 (m, 2H major and minor, H-Ar), 7.18–7.33
(m, 2H major and minor, H-Ar); 13C NMR (62.9 MHz,
3
CDCl3): d = 16.03 (d, JPC = 5.6 Hz, CH3CH2O,
CH3CH2O), 32.94 (d, JPC = 3.9 Hz, C-4, C-4), 40.03
5.1.1.6. r-3-Diethoxyphosphoryl-t-4-methyl-t-5-phe-
nyl-dihydrofuran-2(3H)-one (5e00). Oil, yield = 30%; IR
2
1
1
1
(d, JPC = 151.58 Hz, C-3), 40.14 (d, JPC2 = 137.75 Hz,
C-3), 54.94 (s, CH3O), 62.45 (d, JPC = 6.2 Hz,
CH3CH2O), 62.70 (d, JPC = 6.9 Hz, CH3CH2O), 63.12
(film, cmꢁ1): 1776, 1456, 1252, 1164, 1028; H NMR
3
(250 MHz, CDCl3): d = 0.74 (d, JHH = 7.0 Hz, 3H,
2
CH3), 1.32–1.44 (m, 6H, (CH3CH2O) P(O)), 2.88 (dd,
2
2
2
2
(d, JPC = 6.2 Hz, CH3CH2O), 63.36 (d, JPC = 6.9 Hz,
CH3CH2O), 80.07 (d, JPC = 12.6 Hz, C-5), 80.30 (d,
3JHH = 3.9 Hz, JHP = 23.8 Hz, 1H, H-3), 3.15–3.28
(m, 1H, H-4), 4.08–4.27 (m, 4H (CH3CH2O)2P(O)),
3
3JPC = 2.5 Hz, C-5), 113.78 (s, 2· C-Ar), 113.83 (s, 2·
C-Ar), 126.83 (s, 2· C-Ar, 2· C-Ar), 127.21 (s, C-Ar,
3
5.86 (d, JHH = 6.6 Hz, 1H, H-5), 7.07–7.47 (m, 5H,
H-Ar); 13C NMR (62.9 MHz, CDCl3): d = 16.01 (s,

4878
A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
CH3), 16.19 (s, (CH3CH2O)2), 37.41 (s, C-4), 48.02 (d,
1JPC = 137.1 Hz, C-3), 62.79 (d, 2JPC = 6.9 Hz, CH3CH2
(101 MHz, CDCl3): d = 20.67; Anal. Calcd for
C16H23O6P: C, 56.14; H, 6.77. Found: C, 56.31; H,
6.92.
2
OP(O)), 63.58 (d, JPC = 6.9 Hz, CH3CH2OP(O)), 82.99
(d, 3JPC = 3.7 Hz, C-5), 125.22 (s, 2· C-Ar), 128.04 (s, C-
Ar), 128.35 (s, 2· C-Ar), 135.40 (s, C-Ar), 171.23 (s, C-
2); 31P NMR (101 MHz, CDCl3): d = 19.95; Anal. Calcd
for C15H21O5P: C, 57.69; H, 6.78. Found: C, 57.78; H,
6.81.
5.1.1.10. r-3-Diethoxyphosphoryl-t-4-methyl-t-5-(4-
methoxyphenyl)-dihydrofuran-2(3H)-one (5g00). Oil, yield
= 38%; IR (film, cmꢁ1): 1776, 1516, 1252, 1164, 1024;
1H NMR (250 MHz, CDCl3): d = 0.78 (d, 3JHH = 6.8 Hz,
3H, CH3), 1.31–1.42 (m, 6H, (CH3CH2O)2P(O)), 2.87
(dd, 3JHH = 3.5 Hz, 2JHP = 23.8 Hz, 1H, H-3), 3.11–3.25
(m, 1H, H-4), 3.80 (s, 3H, CH3O), 4.12–4.38 (m, 4H
5.1.1.7. c-5-(4-Bromophenyl)-r-3-diethoxyphosphoryl-t-
4-methyl-dihydrofuran-2(3H)-one (5f0). Oil, yield = 40%;
IR (film, cmꢁ1): 1780, 1252, 1160, 1024; 1H NMR
3
(CH3CH2O)2P(O)), 5.84 (d, JHH = 6.6 Hz, 1H, H-5),
3
(250 MHz, CDCl3): d = 1.28 (d, JHH = 6.2 Hz, 3H,
CH3), 1.27–1.41 (m, 6H, (CH3CH2O)2P(O)), 2.70–2.88
6.87–6.96 (m, 2H, H-Ar), 7.13–7.18 (m, 2H, H-Ar); 13C
NMR (62.9 MHz, CDCl3): d = 15.85 (s, CH3), 16.05 (d,
3
2
2
(m, 1H, H-4), 2.89 (dd, JHH = 11.3 Hz, JHP = 23.4 Hz,
1H, H-3), 4.12–4.38 (m, 4H, (CH3CH2O)2P(O)), 4.82 (d,
3JHH = 9.0 Hz, 1H, H-5), 7.20–7.26 (m, 2H, H-Ar), 7.49–
7.60 (m, 2H, H-Ar); 13C NMR (62.9 MHz, CDCl3):
3JCP = 3.6 Hz, (CH3CH2O)2), 37.39 (d, JPC = 1.8 Hz,
C-4), 47.68 (d, JPC = 137.8, C-3), 54.92 (s, CH3O),
1
62.62 (d, 2JPC = 7.5 Hz, CH3CH2O), 63.41 (d,
3
2JPC = 6.2 Hz, CH3CH2O), 82.84 (d, JPC = 4.3 Hz, C-
3
d = 15.91 (s, CH3), 16.14 (d, JPC = 5.6 Hz, CH3CH2O),
5), 113.61 (s, 2· C-Ar), 126.46 (s, 2· C-Ar), 127.19 (s, C-
16.23 (d, 3JPC = 5.6 Hz, CH3CH2O), 41.93 (d,
Ar), 130.53 (s, C-Ar), 171.19 (d, JCP = 3.14 Hz, C-2);
2
1
2JPC = 1.9 Hz, C-4), 46.88 (d, JPC = 150.9 Hz, C-3),
31P NMR (101 MHz, CDCl3): d = 20.10; Anal. Calcd
for C16H23O6P: C, 56.14; H, 6.77. Found: C, 56.19; H,
6.53.
62.46 (d, 2JPC = 6.2 Hz, CH3CH2O), 63.49 (d,
3
2JPC = 6.9 Hz, CH3CH2O), 86.32 (d, JPC = 14.5 Hz, C-
5), 122.87 (s, C-Ar), 127.88 (s, 2· C-Ar), 131.93 (s, 2· C-
Ar), 136.01 (s, C-Ar), 170.48 (s, C-2); 31P NMR
(101 MHz, CDCl3): d = 20.31; Anal. Calcd for
C15H20BrO5P: C, 46.05; H, 5.15. Found: C, 46.21; H, 5.07.
5.1.2. General procedure for the preparation of 5-aryl-3-
methylidene-2-furanones (6a–g). A solution of 5-aryl-3-
diethoxyphosphoryl-2-furanones (5a–g) (1.0 mmol) in
Et2O (5 mL) was added to a suspension of t-BuOK
(0.146 g, 1.2 mmol) in Et2O (3 mL), and the reaction
mixture was stirred at room temperature for 0.5 h. Next,
the paraformaldehyde (0.150 g, 5.0 mmol) was added
and the mixture was stirred for 1.5 h then the brine
(5 mL) was added, layers were separated, and water
layer was washed with Et2O (2· 10 mL). Combined or-
ganic extracts were dried (MgSO4) and evaporated to
give crude products which were purified by column
chromatography (CHCl3).
5.1.1.8. t-5-(4-Bromophenyl)-r-3-diethoxyphosphoryl-t-
4-methyl-dihydrofuran-2(3H)-one (5f00). Oil, yield = 50%;
IR (film, cmꢁ1): 1776, 1256, 1164, 1024; 1H NMR
3
(250 MHz, CDCl3): d = 0.76 (d, JHH = 7.2 Hz, 3H,
CH3), 1.32–1.49 (m, 6H, (CH3CH2O)2P(O)), 2.86 (dd,
2
3JHH = 3.4 Hz, JHP = 23.8 Hz, 1H, H-3), 3.13–3.21 (m,
1H, H-4), 4.11–4.33 (m, 4H (CH3CH2O)2P(O)), 5.82 (d,
3JHH = 6.3 Hz, 1H, H-5), 7.11–7.21 (m, 2H, H-Ar), 7.40–
7.72 (m, 2H, H-Ar); 13C NMR (62.9 MHz, CDCl3):
d = 15.85 (s, CH3), 16.19 (s, CH3CH2O), 37.22 (d,
1
2JPC = 4.4 Hz, C-4), 48.10 (d, JPC = 137.1 Hz, C-3),
5.1.2.1. 3-Methylene-5-phenyl-dihydrofuran-2(3H)-one
(6a)46,47. Oil, yield = 55% (lit. yield 88%49).
62.83 (d, 2JPC = 6.9 Hz, CH3CH2O), 63.65 (d,
2JPC = 6.9 Hz, CH3CH2O), 82.27 (d, 3JPC = 3.7 Hz, C-5),
121.91 (s, C-Ar), 126.91 (s, 2· C-Ar), 131.50 (s, 2· C-Ar),
134.45 (s, C-Ar), 170.95 (s, C-2); 31P NMR (101 MHz,
CDCl3): d = 19.59; Anal. Calcd for C15H20BrO5P: C,
46.05; H, 5.15. Found: C, 45.92; H, 5.12.
5.1.2.2. 5-(4-Bromophenyl)-3-methylene-dihydrofuran-
2(3H)-one (6b)47. Oil, yield = 45%; IR (film, cmꢁ1): 1772,
1252, 1136; 1H NMR (250 MHz, CDCl3): d = 2.86 (ddt,
3
2
4JHH = 2.8 Hz, JHH = 6.5 Hz, JHH = 17.0 Hz, 1H, H-
4),
3.40
(ddt,
4JHH = 2.8 Hz,
3JHH = 8.0 Hz,
3
5.1.1.9. r-3-Diethoxyphosphoryl-t-4-methyl-c-5-(4-
methoxyphenyl)-dihydrofuran-2(3H)-one (5g0). Oil, yield
= 47%; IR (film, cmꢁ1): 1772, 1252, 1172, 1028; 1H
2JHH = 17.0 Hz, 1H, H-4), 5.48 (dd, JHH = 6.5 Hz,
3JHH = 8.0 Hz, 1H, H-5), 5.71 (t, JHH = 2.8 Hz, 1H,
4
4
CH2@C), 6.32 (t, JHH = 2.8 Hz, 1H, CH2@C), 7.19–
3
NMR (250 MHz, CDCl3): d = 1.25 (d, JHH = 6.3 Hz,
7.24 (m, 2H, H-Ar), 7.50–7.54 (m, 2H, H-Ar); 13C
NMR (62.9 MHz, CDCl3): d = 36.15 (s, C-4), 77.17 (s,
C-5), 122.53 (s, C-Ar), 122.82 (s, CH2@C), 127.04 (s,
2· C-Ar), 131.99 (s, 2· C-Ar), 133.71 (s, C-Ar), 138.84
(s, CH2@C), 169.80 (s, C-2); Anal. Calcd for
C11H9BrO2: C, 52.20; H, 3.58. Found: C, 52.28; H,
3.62.
3H, CH3), 1.32–1.42 (m, 6H, (CH3CH2O)2P(O)), 2.75–
3.02 (m, 1H, H-4), 2.86 (dd, 3JHH = 11.4 Hz,
2JHP = 29.4 Hz, 1H, H-3), 3.82 (s, 3H, CH3O), 4.11–
3
4.40 (m, 4H (CH3CH2O)2P(O)), 4.86 (d, JHH = 9.2 Hz,
1H, H-5), 6.90–6.95 (m, 2H, H-Ar), 7.28–7.33 (m, 2H,
H-Ar); 13C NMR (62.9 MHz, CDCl3): d = 15.70 (s,
CH3), 16.09 (d, JPC = 5.6 Hz, CH3CH2O), 16.18 (d,
3
2
3JPC = 3.6 Hz, CH3CH2O), 41.75 (d, JPC = 1.8 Hz, C-
4), 47.03 (d, JPC = 151.0 Hz, C-3), 55.03 (s, CH3O),
5.1.2.3. 5-(4-Methoxyphenyl)-3-methylene-dihydrofu-
ran-2(3H)-one (6c) and 5-(4-methoxyphenyl)-3-methylfu-
ran-2(5H)-one (7c) (60:40). Oil, yield = 61%.
1
2
62.33 (d, JPC = 6.2 Hz, CH3CH2OP(O)), 63.30 (d,
2JPC = 6.2 Hz, CH3CH2OP(O)), 87.07 (d, 3JPC = 14.5 Hz,
C-5), 113.87 (s, 2· C-Ar), 127.84 (s, 2· C-Ar), 128.56 (s,
C-Ar), 130.58 (s, C-Ar), 170.62 (s, C-2); 31P NMR
5.1.2.3.1. 5-(4-Methoxyphenyl)-3-methylene-dihydro-
1
furan-2(3H)-one (6c)46,47. H NMR48 (250 MHz, CDCl3):
d = 2.91
(ddt,
4JHH = 2.9 Hz,
3JHH = 6.6 Hz,

A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
4879
4
2JHH = 17.0 Hz, 1H, H-4), 3.36 (ddt, JHH = 2.5 Hz,
5.1.2.9. r-5-(4-Methoxyphenyl)-t-4-methyl-3-methy-
lene-dihydrofuran-2(3H)-one (6g0)46,47. Oil, yield = 61%;
(lit. yield = 76%46).
3JHH = 7.9 Hz, JHH = 17.0 Hz, 1H, H-4), 3.81 (s, 3H,
CH3O), 5.47 (dd, JHH = 6.6 Hz, JHH = 7.9 Hz, 1H,
2
3
3
4
H-5), 5.68 (dd, JHH = 2.5 Hz, JHH = 2.9 Hz, 1H,
4
4
4
CH2@C), 6.30 (dd, JHH = 2.5 Hz, JHH = 2.9 Hz, 1H,
CH2@C), 6.86–6.93 (m, 2H, H-Ar), 7.24–7.27 (m, 2H,
H-Ar).
5.1.2.10. r-5-(4-Methoxyphenyl)-c-4-methyl-3-methy-
lene-dihydrofuran-2(3H)-one (6g00)26,46. White crystal,
mp 82 ꢁC; yield = 66%; (lit. yield = 13%46).
5.1.2.3.2. 5-(4-Methoxyphenyl)-3-methylfuran-2(5H)-one
1
(7c). H NMR48 (250 MHz, CDCl3): d = 3.18 (s, 3H,
CH3), 3.82 (s, 3H CH3O), 5.50 (d, JHH = 1.4 Hz, 1H,
5.1.3. General procedure for the preparation of 5-aryl-3-
diethoxyphosphorylpyrrolidin-2-ones (9a–c). To a stirred
solution of titanium (IV) isopropoxide (1.84 g,
6.5 mmol), 2 N solution of methyl amine in methanol
(3.25 mL, 6.5 mmol) was added, then 2-dietoxyphos-
phoryl-4-oxoalkanoate (3a–c) (5.0 mmol) in methanol
(20 mL) was added at room temperature. The reaction
mixture was stirred for 3 h, then sodium borohydride
(0.189 g, 5.0 mmol) was added in one portion. Stirring
was continued for 24 h. The water (15 mL) was added
and methanol was evaporated under reduced pressure.
The residue was extracted with chloroform (4·
20 mL). The combined organic layers were washed with
water (20 mL) and dried (MgSO4). Evaporation of the
solvent under reduced pressure afforded a crude product
which was purified by column chromatography (CHCl3/
acetone, 90:10) affording pure product.
3
3
H-5), 6.15 (d, JHH = 1.4 Hz, 1H, H-4), 6.86–6.93 (m,
2H, H-Ar), 7.24–7.27 (m, 2H, H-Ar).
5.1.2.4. 3-Methylene-5-(naphthalen-1-yl)-dihydrofu-
(6d)46.
ran-2(3H)-one
yield = 87%46).
Oil,
yield = 30%;
(lit.
5.1.2.5. t-4-Methyl-3-methylene-r-5-phenyl-dihydrofu-
ran-2(3H)-one (6e0)47. Oil, yield = 66%; IR (film, cmꢁ1):
1768, 1256, 1136; 1H NMR (250 MHz, CDCl3): d = 1.32
3
(d, JHH = 6.8 Hz, 3H, CH3), 2.91–3.01 (m, 1H, H-4),
4.90 (d, 3JHH = 7.7 Hz, 1H, H-5), 5.62 (d,
4
4JHH = 3.0 Hz, 1H, CH2@C), 6.31 (d, JHH = 3.0 Hz,
1H, CH2@C), 7.28–7.46 (m, 5H, H-Ar); 13C NMR
(62.9 MHz, CDCl3): d = 14.87 (s, CH3), 42.39 (s, C-4),
84.90 (s, C-5), 119.93 (s, CH2@C), 124.34 (s, 2· C-Ar),
127.76 (s, C-Ar), 127.78 (s, 2· C-Ar), 137.38 (s,
CH2@C), 139.49 (s, C-Ar), 169.02 (s, C-2); Anal. Calcd
for C12H12O2: C, 76.57; H, 6.43. Found: C, 76.41; H,
6.35.
5.1.3.1. 3-Diethoxyphosphoryl-1-methyl-5-phenylpyrr-
olidin-2-one (9a). Oil, yield = 77%; IR (film, cmꢁ1): 1688,
1392,1252, 1136, 1024; 1H NMR (250 MHz, CDCl3):
d = 1.22–1.67 (m, 6H, (CH3CH2O)2P(O) major and min-
or), 2.05–2.29 (m, 1H major and minor, H-4), 2.55–2.91
(m, 1H major and minor, H-4), 2.68 (s, 3H, CH3N)
3.04–3.14 (m, 1H major and minor, H-3), 4.12–4.35
(m, 4H major and minor, (CH3CH2O)2P(O)), 4.33–
4.67 (m, 1H major and minor, H-5), 7.21–7.43 (m, 5H
major and minor, H-Ar); 13C NMR (62.9 MHz,
5.1.2.6. c-4-Methyl-3-methylene-r-5-phenyl-dihydrofu-
(6e00)46.
ran-2(3H)-one
yield = 86%46).
Oil,
yield = 65%;
(lit.
5.1.2.7. r-5-(4-Bromophenyl)-t-4-methyl-3-methylene-
dihydrofuran-2(3H)-one (6f0)26,47. Oil, yield = 52%; IR
(film, cmꢁ1): 1772, 1256, 1132; 1H NMR (250 MHz,
CDCl3): d = 1.32 (d, JHH = 6.8 Hz, 3H, CH3), 2.82–
2.94 (m, 1H, H-4), 4.86 (d, JHH = 7.8 Hz, 1H, H-5),
3
CDCl3): d = 16.23 (d, JPC = 6.9 Hz, CH3CH2O), 16.33
(d, JPC = 6.9 Hz, CH3CH2O), 28.41 (s, CH3N), 28.55
3
3
2
(s, CH3N), 30.10 (d, JPC = 4.4 Hz, C-4), 30.83 (d,
3
1
2JPC = 4.4 Hz, C-4), 40.47 (d, JPC = 142.8 Hz, C-3),
40.58 (d, JPC = 150.3 Hz, C-3), 62.02 (d, JPC = 6.2 Hz,
4
1
2
5.60 (d, JHH = 3.0 Hz, 1H, CH2@C), 6.32 (d,
4JHH = 3.0 Hz, 1H, CH2@C), 7.20–7.57 (m, 2H, H-Ar),
7.48–7.57 (m, 2H, H-Ar); 13C NMR: 15.80 (s, CH3),
43.41 (s, C-4), 85.12 (s, C-5), 121.36 (s, CH2@C),
122.82 (s, C-Ar), 127.54 (s, 2· C-Ar), 131.99 (s, 2· C-
Ar), 137.46 (s, CH2@C), 140.03 (s, C-Ar), 169.75 (s, C-
2); Anal. Calcd for C12H11BrO2: C, 53.96; H, 4.15.
Found: C, 53.99; H, 4.31.
2
CH3CH2O), 62.12 (d, JPC = 6.9 Hz, CH3CH2O), 62.96,
63.06, 63.10, 63.14, 63.24 (C-5, CH3CH2OP(O)), 126.34
(s, 2· C-Ar), 126.92 (s, 2· C-Ar), 128.21 (s, C-Ar),
128.29 (s, C-Ar), 128.87 (s, 2· C-Ar), 128.97 (s, 2· C-
Ar), 140.01 (s, C-Ar), 140.08 (s, C-Ar), 169.69 (d,
2
2JPC = 5.0 Hz, C-2), 169.76 (d, JPC = 4.4 Hz, C-2); 31P
NMR (101 MHz, CDCl3): d = 24.81 minor, 25.00 ma-
jor; (30:70); Anal. Calcd for C15H22NO4P: C, 57.87;
H, 7.12. Found: C, 57.62; H, 7.33.
5.1.2.8. r-5-(4-Bromophenyl)-c-4-methyl-3-methylene-
dihydrofuran-2(3H)-one (6f00)26. Oil, yield = 51%; IR
(film, cmꢁ1): 1764, 1252, 1136; 1H NMR (250 MHz,
CDCl3): d = 0.88 (d, JHH = 7.1 Hz, 3H, CH3), 3.35–
3.51 (m, 1H, H-4), 5.57 (d, JHH = 8.3 Hz, 1H, H-5),
5.1.3.2. 5-(4-Bromophenyl)-3-diethoxyphosphoryl-1-
methylpyrrolidin-2-one (9b). Oil, yield = 92%; IR (film,
cmꢁ1): 1692, 1392,1256, 1132, 1024; 1H NMR
(250 MHz, CDCl3): d = 1.31–1.64 (m, 6H, (CH3CH2O)2-
P(O) major and minor), 2.00–2.32 (m, 1H major and
minor, H-4), 2.62 (s, 3H, CH3N minor), 2.67 (s, 3H,
CH3N major), 2.57–2.91 (m, 1H major and minor, H-
4), 3.01–3.20 (m, 1H, H-3 major and minor), 4.14–4.31
(m, 4H major and minor, (CH3 CH2O)2P(O)), 4.62–
4.66 (m, 1H, H-5 major and minor), 7.07–7.24 (m, 2H
H-Ar major and minor), 7.51–7.54 (m, 2H, H-Ar major
and minor); 13C NMR (62.9 MHz, CDCl3): d = 16.21 (d,
3
3
4
5.59 (d, JHH = 2.6 Hz, 1H, CH2@C), 6.34 (d,
4JHH = 2.6 Hz, 1H, CH2@C), 7.04–7.10 (m, 2H, H-Ar),
7.48–7.61 (m, 2H, H-Ar); 13C NMR (62.9 MHz,
CDCl3): d = 15.42 (s, CH3), 38.66 (s, C-4), 81.32 (s,
C-5), 122.11 (s, CH2@C), 122.35 (s, C-Ar), 127.60 (s,
2· C-Ar), 131.63 (s, 2· C-Ar), 135.34 (s, CH2@C),
139.63 (s, C-Ar), 170.18 (s, C-2); Anal. Calcd for
C12H11BrO2: C, 53.96; H, 4.15. Found: C, 54.11; H,
4.36.

4880
A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
3
4
(ddt, JHH = 2.6 Hz, JHH = 8.5 Hz, JHH = 17.2 Hz,
3
2
3JPC = 6.9 Hz, CH3CH2O), 16.31 (d, JPC = 6.7 Hz,
CH3CH2O), 29.46 (s, CH3N), 29.97 (s, CH3N), 30.12
3
1H, H-4), 4.52 (dd, JHH = 5.0 Hz, JHH = 8.5 Hz, 1H,
3
2
(d, JPC = 3.1 Hz, C-4), 30.87 (d, JPC = 3.4 Hz, C-4),
2
4
H-5), 5.36 (t, JHH = 2.6 Hz, 1H, CH2@C), 6.08 (t,
1
40.64 (d, JPC = 143.5 Hz, C-3), 40.68 (d, JPC
1
=
149.1 Hz, C-3), 62.64 (d, JPC = 6.2 Hz, CH3 CH2O),
4JHH = 2.6 Hz, 1H, CH2@C), 7.18–7.22 (m, 2H, H-Ar),
7.33–7.43 (m, 3H, H-Ar); 13C NMR (62.9 MHz,
CDCl3): d = 28.53 (s, CH3N), 34.79 (s, C-4), 61.40 (s,
C-5), 115.43 (s, CH2=C), 126.27 (s, 2· C-Ar), 128.18
(s, C-Ar), 129.02 (s, 2· C-Ar), 138.75 (s, CH2@C),
140.90 (s, C-Ar), 168.39 (s, C-2); Anal. Calcd for
C12H13NO: C, 76.98; H, 7.00. Found: C, 76.75; H, 7.22.
2
2
3
62.82 (d, JPC = 6.9 Hz, CH3CH2O), 62.56 (d, JPC
=
3.4 Hz, C-5), 63.36 (d, 2JPC = 6.2 Hz, CH3CH2O), 63.62
(d, JPC = 6.9 Hz, CH3CH2O), 122.38 (s, C-Ar), 122.51
2
(s, C-Ar), 126.92 (s, 2· C-Ar), 127.32 (s, C-Ar), 131.73
(s, 2· C-Ar), 137.30 (s, C-Ar), 137.46 (s, C-Ar), 169.58
2
2
(d, JPC = 4.4 Hz, C-2), 169.82 (d, JPC = 3.4 Hz, C-2);
31P NMR (101 MHz, CDCl3): d = 24.39 major and min-
or; Anal. Calcd for C15H21BrNO4P: C, 46.17; H, 5.42.
Found: C, 46.31; H, 5.57.
5.1.4.2. 5-(4-Bromophenyl)-1-methyl-3-methylenepyrr-
olidin-2-one (10b). Oil, yield = 65%; IR (film, cmꢁ1):
1688, 1484, 1392, 1076; H NMR (250 MHz, CDCl3):
1
4
3
2
d = 2.58 (ddt, JHH = 2.7 Hz, JHH = 5.1 Hz, JHH
17.3 Hz, 1H, H-4), 2.75 (s, 3H, CH3N), 3.22 (ddt,
=
5.1.3.3. 5-(4-Methoxyphenyl)-3-diethoxyphosphoryl-1-
methylpyrrolidin-2-one (9c). Oil, yield = 58%; IR (film,
cmꢁ1): 1684, 1398,1256, 1132, 1020; 1H NMR
(250 MHz, CDCl3): d = 1.32–1.41 (m, 6H, (CH3CH2O)2-
P(O) major and minor), 2.09–2.30 (m, 1H major and min-
or, H-4), 2.59 (s, 3H, CH3N minor), 2.65 (s, 3H, CH3N
major), 2.67–2.89 (m, 1H major and minor, H-4), 2.99–
3.19 (m, 1H, H-3 major and minor), 3.82 (s, 3H, CH3O
major and minor) 4.14–4.31 (m, 4H major and minor,
(CH3CH2O)2P(O)), 4.60–4.66 (m, 1H, H-5 major and
minor), 6.89–6.93 (m, 2 H H-Ar major and minor),
7.10–7.14 (m, 2H, H-Ar major and minor); 13C NMR
(62.9 MHz, CDCl3): d = 16.24 (d, 3JPC = 6.3 Hz,
3
2
4JHH = 2.4 Hz, JHH = 8.5 Hz, JHH = 17.3 Hz, 1H, H-
4), 4.47 (dd, JHH = 5.1 Hz, JHH = 8.5 Hz, 1H, H-5),
3
3
4
4
5.36 (dd, JHH = 2.4 Hz, JHH = 2.7 Hz, 1H, CH2@C),
4
4
6.08 (dd, JHH = 2.4 Hz, JHH = 2.7 Hz, 1H, CH2@C),
7.04–7.09 (m, 2H, H-Ar), 7.48–7.53 (m, 2H, H-Ar);
13C NMR (62.9 MHz, CDCl3): d = 28.52 (s, CH3N),
34.62 (s, C-4), 60.82 (s, C-5), 115.87 (s, CH2@C),
122.05 (s, C-Ar), 127.95 (s, 2· C-Ar), 132.19 (s, 2· C-
Ar), 138.20 (s, CH2@C), 139.97 (s, C-Ar), 168.30 (s, C-
2); Anal. Calcd for C12H12BrNO: C, 54.16; H, 4.54.
Found: C, 54.00; H, 4.55.
3
CH3CH2O), 16.33 (d, JPC = 6.4 Hz, CH3CH2O), 28.25
5.1.4.3. 5-(4-Methoxyphenyl)-1-methyl-3-methylene-
pyrrolidin-2-one (10c). Yellow crystal, mp 95 ꢁC,
yield = 59%; IR (film, cmꢁ1): 1684, 1512, 1436, 1284,
1080; 1H NMR (250 MHz, CDCl3): d = 2.60 (ddt,
2
(s, CH3N), 28.42 (s, CH3N), 30.15 (d, JPC = 3.4 Hz, C-
4), 30.97 (d, 2JPC = 3.9 Hz, C-4), 40.58 (d, 1JPC = 145.7 Hz,
C-3), 40.64 (d, JPC = 145.9 Hz, C-3), 55.16 (s, CH3O),
1
61.92 (d, 2JPC = 6.9 Hz, CH3CH2O), 62.07 (d,
4JHH = 2.7 Hz, JHH = 5.0 Hz, JHH = 17.3 Hz, 1H, H-
3
2
2JPC = 7.2 Hz, CH3CH2O), 62.56 (d, 3JPC = 3.3 Hz, C-5),
4
4), 2.73 (s, 3H, CH3N), 3.19 (ddt, JHH = 2.7 Hz,
2
2
63.00 (d, JPC = 6.5 Hz, CH3CH2OP(O)), 63.12 (d,
3JHH = 8.3 Hz, JHH = 17.3 Hz, 1H, H-4), 3.81 (s, 3H,
CH3O), 4.45 (dd, JHH = 5.0 Hz, JHH = 8.3 Hz, 1H, H-
2JPC = 7.6 Hz, CH3CH2OP(O)), 114.19 (s, 2· C-Ar),
114.29 (s, 2· C-Ar), 127.65 (s, C-Ar), 128.23 (s, C-Ar),
131.84 (s, 2· C-Ar), 131.98 (s, 2· C-Ar), 159.46 (s, C-Ar),
3
3
4
5), 5.34 (t, JHH = 2.7 Hz, 1H, CH2@C), 6.06 (t,
4JHH = 2.7 Hz, 1H, CH2@C), 6.87–6.92 (m, 2H, H-Ar),
7.09–7.12 (m, 2H, H-Ar); 13C NMR (62.9 MHz, CDCl3):
d = 28.41 (s, CH3N), 34.93 (s, C-4), 55.27 (s, CH3O), 60.90
(s, C-5), 114.36 (s, 2· C-Ar), 115.30 (s, CH2@C), 127.56 (s,
2· C-Ar), 132.82 (s, CH2@C), 138.96 (s, C-Ar), 159.49 (s,
C-Ar), 168.30 (s, C-2); Anal. Calcd for C13H15NO: C,
71.87; H, 6.96. Found: C, 72.03; H, 6.90.
2
159.52 (s, C-Ar), 169.44 (d, JPC = 3.2 Hz, C-2), 169.56
2
(d, JPC = 3.8 Hz, C-2); 31P NMR (101 MHz, CDCl3):
d = 24.67 minor, 24.78 major; (40:60); Anal. Calcd for
C16H24NO5P: C, 56.30; H, 7.09. Found: C, 56.21; H, 7.22.
5.1.4. General procedure for the preparation of 5-aryl-3-
methylidenepyrrolidin-2-ones (10a–c). A solution of
5-aryl-3-diethoxyphosphorylpyrrolidin-2-one (9a–c)
(1.0 mmol) in THF (5 mL) was added to a suspension
of NaH (0.033 g, 1.1 mmol) in THF (3 mL) at 0 ꢁC,
and the reaction mixture was stirred for 0.5 h. Next,
paraformaldehyde (0.330 g, 1.1 mmol) was added at
0 ꢁC and the mixture was stirred for 1.5 h at room tem-
perature. After cooling to 0 ꢁC, brine (5 mL) was
added, layers were separated, and water layer was
washed with CH2Cl2 (2· 10 mL). Combined organic
extracts were dried (MgSO4) and evaporated to give
crude product which was purified by column chroma-
tography (CHCl3).
5.1.5. General procedure for the preparation of 3-alkyl-
idene-5-aryl-2 furanones (11a–b). A solution of 3-
diethoxyphosphoryl-5-phenyl-2-furanone (5a) (0.300 g,
1.0 mmol) in THF (5 mL) was added to a suspension
of NaH (0.033 g, 1.1 mmol) in THF (3 mL), and the
reaction mixture was stirred at room temperature for
0.5 h. Next, appropriate aldehyde (1.1 mmol) was added
and the mixture was refluxed for 1.5 h. After cooling to
room temperature, brine (5 mL) was added, layers were
separated, and water layer was washed with CH2Cl2 (2·
10 mL). Combined organic extracts were dried (MgSO4)
and evaporated to give crude product which was puri-
fied by column chromatography (CHCl3).
5.1.4.1. 1-Methyl-3-methylene-5-phenylpyrrolidin-2-
one (10a)15,49. Oil, yield = 79%; IR (film, cmꢁ1): 1692,
1432, 1284, 1080; 1H NMR (250 MHz, CDCl3):
d = 2.64 (ddt,
2JHH = 17.2 Hz, 1H, H-4), 2.78 (s, 3H, CH3N), 3.23
5.1.5.1. (Z)-3-(2-Methylpropylidene)-5-phenyl-dihy-
drofuran-2(3H)-one (Z)-(11a). Oil, yield = 88%; IR (film,
1
4JHH = 2.6 Hz,
3JHH = 5.0 Hz,
cmꢁ1): 1756, 1364, 1200; H NMR (250 MHz, CDCl3):
3
d = 1.04 (d, JHH = 6.8 Hz, (CH3)2CH), 2.85 (ddd,

A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
4881
3
2
4
4), 2.70 (s, CH3N), 3.13 (ddd, JHH = 2.3 Hz,
4JHH = 3.0 Hz, JHH = 7.8 Hz, JHH = 16.0 Hz, 1H, H-
4
4), 3.28 (ddd, JHH = 3.0 Hz, JHH = 7.8 Hz, JHH
3
2
2
=
16.0 Hz, 1H, H-4), 3.70–3.86 (m, (CH3)2CH), 5.45 (dd,
3JHH = 8.6 Hz, JHH = 16.5 Hz, 1H, H-4), 4.04 (dq,
3
3JHH = 6.7 Hz, JHH = 9.9 Hz, 1H, (CH3)2CH), 4.44
(dd, JHH = 4.5 Hz, JHH = 8.6 Hz, 1H, H-5), 5.65 (dt,
3JHH = 7.8 Hz, JHH = 7.8 Hz, 1H, H-5), 5.69 (dt,
3
3
3
3
3
4JHH = 3.0 Hz, JHH = 10.0 Hz, 1H, CH@C), 7.30–7.43
4JHH = 2.3 Hz, JHH = 9.9 Hz, 1H, CH@C), 7.12–7.21
(m, 5H, H-Ar); 13C NMR (62.9 MHz, CDCl3):
d = 22.24 (s, CH3), 22.37 (s, CH3), 26.31 (s, (CH3)2CH),
37.77 (s, C-4), 77.80 (s, C-5), 121.99 (s, C-Ar), 125.30 (s,
2· C-Ar), 128.25 (s, C-Ar) 128.62 (s, 2· C-Ar), 140.05 (s,
CH@C), 150.82 (s, CH@C), 169.29 (s, C-2); Anal. Calcd
for C14H16O2: C, 77.75; H, 7.46. Found: C, 77.83; H,
7.55.
(m, 2H, H-Ar), 7.32–7.35 (m, 2H, H-Ar); 13C NMR
(62.9 MHz, CDCl3): d = 21.20 (s, (CH3)2CH), 23.63 (s,
CH), 26.48 (s, CH3N), 34.54 (s, C-4), 69.88 (s, C-5),
124.45 (s, CH2@C), 124.62 (s, 2· C-Ar), 126.26 (s,
CH2@C), 127.02 (s, 2· C-Ar), 139.62 (s, C-Ar), 142.36
(s, C-Ar), 167.28 (s, C-2); Anal. Calcd for C15H19NO:
C, 78.56; H, 8.35. Found: C, 78.73; H, 8.58.
5.1.5.2. (Z) and (E)-3-(2-Methylpropylidene)-5-phenyl-
5.2. Pharmacology
1
dihydrofuran-2(3H)-one (Z,E)-(11a). Oil, H NMR48
(250 MHz, CDCl3): d = 1.04 (d, 3JHH = 6.8 Hz,
(CH3)2CH Zisomer), 1.05 (d, JHH = 6.6 Hz, (CH3)2CH
5.2.1. Cells and cytotoxicity assays. Mouse leukemia L-
1210 cells were cultured in RPMI 1640 medium (Sigma,
St. Louis, MO) supplement with 10% fetal calf serum
(Gibco, Berlin, Germany), gentamycin (50 lg/mL) and
0.02 M Hepes buffer (Gibco). Cytostatic effects were as-
sayed by measuring inhibitory effects on L-1210 cell pro-
liferation. In this assay, cells were seeded in 2 mL
aliquots onto a 24-well plate (NUNC, Denmark) at a
concentration 1.5 · 103 cells/mL. After 24 h, drug solu-
tion was added and incubation was carried out for an
additional 46 h. The cell number relative to control
was determined by a tetrazolium dye method.51
3
4
3
Eisomer), 2.77 (ddd, JHH = 3.0 Hz, JHH = 6.4 Hz,
2JHH = 16.7 Hz, 1H, H-4 Eisomer), 2.85 (ddd,
3
2
4JHH = 3.0 Hz, JHH = 7.8 Hz, JHH = 16.0 Hz, 1H, H-4
4
3
Zisomer), 3.28 (ddd, JHH = 3.0 Hz, JHH = 7.8 Hz,
2JHH = 16.0 Hz, 1H, H-4 Zisomer), 3.33 (ddd,
3
2
4JHH = 3.0 Hz, JHH = 8.1 Hz, JHH = 16.7 Hz, 1H, H-4
Zisomer), 3.70–3.86 (m, (CH3)2CH Zisomer + Eisomer), 5.45
3
(dd, JHH = 7.8 Hz, JHH = 7.8 Hz, 1H, H-5 Zisomer),
3
5.52 (dd, 3JHH = 6.4 Hz, 3JHH = 8.1 Hz, 1H, H-5 Eisomer),
4
3
5.69 (dt, JHH = 3.0 Hz, JHH = 10.0 Hz, 1H, CH@C
Zisomer), 6.03 (dt, JHH = 3.0 Hz, JHH = 10.1 Hz, 1H,
4
3
CH@C Eisomer), 7.30–7.43 (m, 5H, H-Ar Zisomer
Eisomer).
+
Human leukemia promyelocytic HL-60 and lympho-
blastic NALM-6 cell lines were used. Leukemia cells
were cultured in RPMI 1640 medium supplemented with
10% heat-inactivated fetal bovine serum (Invitrogen,
Paisley, UK) and antibiotics (100 lg/mL streptomycin
and 100 U/mL penicillin). Cells were grown in 37 ꢁC in
a humidified atmosphere of 5% CO2 in air. Cytotoxic
activity was determined by the MTT [3-(4,5-dimethylthi-
azol-2-yl)-2,5-diphenylterazolium bromide, Sigma, St.
Louis, USA] assay.52 Exponentially growing leukemia
cells were seeded at 8 · 103/well on 96-well plate (Nunc,
Roskilde, Denmark). Stock solutions of the analyzed
compounds were freshly prepared in DMSO and diluted
with complete culture medium to obtain the concentra-
tion range from 10ꢁ7 to 10ꢁ3 M. Cells were exposed to
the test compounds for 46 h, then MTT reagent was
added and incubation was continued for 2 h. After incu-
bation, MTT-formazan crystals were dissolved in 20%
SDS and 50% DMF at pH 4.7 and absorbance was read
at 562 and 630 nm on an ELISA-plate reader (ELX 800,
Bio-Tek, USA). As a control, cultured cells were grown
in the absence of drugs. The values of IC50 (the concen-
tration of the tested compound required to reduce the
cells survival fraction to 50% of the control) were calcu-
lated from concentration–response curves and used as a
measure of cellular sensitivity to a given treatment. Data
points represent means of at least 6 repeats SD.
5.1.5.3.
(E)-3-Benzylidene-5-phenyl-dihydrofuran-
2(3H)-one (11b)50. Oil, yield = 50%; IR (film, cmꢁ1):
1732, 1320, 1232, 1192; H NMR (250 MHz, CDCl3):
1
d = 2.96
(ddd,
4JHH = 2.7 Hz,
3JHH = 6.0 Hz,
2JHH = 17.5 Hz, 1H, H-4), 3.64 (ddd, JHH = 2.7 Hz,
4
3JHH = 8.3 Hz, JHH = 17.5 Hz, 1H, H-4), 5.62 (dd,
2
3JHH = 6.0 Hz, JHH = 8.3 Hz, 1H, H-5), 7.32–7.63 (m,
3
10H, H-Ar), 7.67 (t, JHH = 2.7 Hz, 1H, CH@C); 13C
4
NMR (62.9 MHz, CDCl3): d = 36.44 (s, C-4), 78.06 (s,
C-5), 124.02 (s, C-Ar), 125.28 (s, 2· C-Ar), 128.46 (s,
CH@C) 128.80 (s, 2· C-Ar), 128.85 (s, C-Ar), 129.87 (s,
2· C-Ar), 129.95 (s, 2· C-Ar), 134.45 (s, C-Ar) 136.86
(s, CH@C), 140.21 (s, C-Ar), 171.86 (s, C-2); Anal. Calcd
for C17H14O2: C, 81.58; H, 5.64. Found: C, 81.76; H, 5.65.
5.1.6. The preparation of (E)-1-methyl-3-(2-methylpropy-
lidene)-5-phenylpyrrolidin-2-one (12).
A
3-diethoxyphosphoryl-5-phenylpyrrolidin-2-one
solution of
(9a)
(0.311 g, 1.0 mmol) in THF (5 mL) was added to a sus-
pension of NaH (0.033 g, 1.1 mmol) in THF (3 mL) at
0 ꢁC, and the reaction mixture was stirred for 0.5 h at that
temperature. Next, isobutyraldehyde (0.080 g, 1.1 mmol)
was added and the resulting mixture was refluxed for
1.5 h. After cooling to 0 ꢁC, brine (5 mL) was added, lay-
ers were separated, and water layer was washed with
CH2Cl2 (2· 10 mL). Combined organic extracts were
dried (MgSO4) and evaporated to give crude product
which was purified by column chromatography (CHCl3).
Acknowledgment
1
Oil, yield = 59%; IR (film, cmꢁ1): 1752, 1368, 1204; H
3
This work was financed from the government budget for
science in the years 2005–2008 (Project No. 3 T09A 075
28).
NMR (250 MHz, CDCl3): d = 1.01 (d, JHH = 6.7 Hz,
CH3), 1.02 (d, JHH = 6.7 Hz, CH3), 2.58 (ddd,
3
3
2
4JHH = 2.3 Hz, JHH = 4.5 Hz, JHH = 16.5 Hz, 1H, H-

4882
A. Albrecht et al. / Bioorg. Med. Chem. 16 (2008) 4872–4882
27. Kuroda, C.; Kasahara, T.; Akiyama, K.; Amemiya, T.;
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