Branched diacylglycerol-lactones as potent protein kinase C ligands and α-secretase activators

Article abstract of DOI:10.1021/jm0509391

Using as our lead structure a potent PKC ligand (1) that we had previously described, we investigated a series of branched DAG-lactones to optimize the scaffold for PKC binding affinity and reduced lipophilicity, and we examined the potential utility of s

Full text of DOI:10.1021/jm0509391

2028
J. Med. Chem. 2006, 49, 2028-2036
Branched Diacylglycerol-Lactones as Potent Protein Kinase C Ligands and r-Secretase
Activators
Jeewoo Lee,*,† Ji-Hye Kang,† Kee-Chung Han,† Yerim Kim,† Su Yeon Kim,† Hae-Suk Youn,† Inhee Mook-Jung,‡ Hee Kim,#
Jee Hye Lo Han,# Hee Jin Ha,# Young Ho Kim,# Victor E. Marquez,| Nancy E. Lewin,§ Larry V. Pearce,§
Daniel J. Lundberg,§ and Peter M. Blumberg§
Laboratory of Medicinal Chemistry, Research Institute of Pharmaceutical Sciences, College of Pharmacy and Department of Biochemistry &
Cancer Research Institute, College of Medicine, Seoul National UniVersity, Seoul 151-742, Korea, Digital Biotech, Ansan, Kyounggi-Do
425-839, Korea, and Laboratory of Medicinal Chemistry and Laboratory of Cellular Carcinogenesis and Tumor Promotion, Center for Cancer
Research, National Cancer Institute, NIH, Bethesda, Maryland 20892
ReceiVed September 21, 2005
Using as our lead structure a potent PKC ligand (1) that we had previously described, we investigated a
series of branched DAG-lactones to optimize the scaffold for PKC binding affinity and reduced lipophilicity,
and we examined the potential utility of select compounds as R-secretase activators. Activation of R-secretase
upon PKC stimulation by ligands causes increased degradation of the amyloid precursor protein (APP),
resulting in enhanced secretion of sAPPR and reduced deposition of â-amyloid peptide (Aâ), which is
implicated in the pathogenesis of Alzheimer’s disease. We modified in a systematic manner the C5-acyl
group, the 3-alkylidene, and the lactone ring in 1 and established structure-activity relationships for this
series of potent PKC ligands. Select DAG-lactones with high binding affinities for PKC were evaluated for
their abilities to lead to increased sAPPR secretion as a result of R-secretase activation. The DAG-lactones
potently induced R-secretase activation, and their potencies correlated with the corresponding PKC binding
affinities and lipophilicities. Further investigation indicated that 2 exhibited a modestly higher level of sAPPR
secretion than did phorbol 12,13-dibutyrate (PDBu).
Introduction
ing the glycerol backbone into a five-member DAG-lactone.
The second approach, the receptor-guided approach, involves
the use of highly branched alkyl chains to improve the
interaction of the DAG-lactone ligand with a cluster of
conserved hydrophobic amino acids in the space between the
two â-sheets of the C1 domain. We have found that the alkyl
chains in the DAG-lactones are of importance in controlling
binding affinity as a function of size, position on the glycerol
scaffold, and degree of branching.
Using these approaches, we have obtained derivatives of a
DAG-lactone scaffold bearing branched alkyl groups with
reduced lipophilicity and with high affinities as PKC ligands.9,10
For example, DAG-lactone 1a (log P ) 5.03) displayed a high
affinity with a Ki ) 2.9 nM, which was several hundred-fold
more potent than the corresponding straight-chain-substituted
DAG with similar lipophilicity (Ki ) ca. 1 µM).9 Furthermore,
recent enantioselective synthesis confirmed that DAG-lactone
2, the (R)-enantiomer of 1a, proved to be the “active” isomer
with exactly one-half (Ki ) 1.45 nM) of the Ki value found for
the racemate.11
The protein kinase C (PKC)1,2 family of serine/threonine
kinases are key enzymes in cellular signal transduction, being
activated by diacylglycerol (DAG) generated either by phos-
pholipase C (PLC) mediated hydrolysis of phosphatidylinositol-
4,5-biphosphate (PIP2) or indirectly by the action of phospho-
lipase D and phosphatidic acid hydrolase.3 DAG induces the
translocation of cytosolic PKC to the inner leaflet of the cellular
membrane and activates both the calcium-dependent classical
PKC isoforms (PKC-R, â, and γ) and the novel or calcium-
independent PKC isoforms (PKC-δ, ꢀ, η, and θ) by binding to
the C1 domains of the enzymes and promoting association with
the membrane phospholipids.4
Whereas the transiently generated DAG binds only weakly
to the C1 domains of the enzyme, phorbol esters bind to the
same DAG-binding site in a competitive manner with affinities
several orders of magnitude greater than those of DAGs and
have provided powerful pharmacological tools for studying PKC
function.5,6 Phorbol esters function as potent and metabolically
stable DAG surrogates because their conformationally rigid
scaffold, unlike the flexible glycerol backbone of DAG, is able
to specifically direct the hydrophilic pharmacophores.
The â-amyloid peptide (Aâ), a 39-43 amino acid peptide,
has been implicated in the pathogenesis of Alzheimer’s disease
(AD) and is generated from amyloid precursor protein (APP)
by stepwise proteolytic processing by the â- and γ-secretases.
Thus, inhibition of the â- and γ-secretases has been regarded
as a promising approach for the development of novel anti-
Alzheimer agents.12-15
Over the past several years, we have attempted to bridge the
affinity gap between phorbol esters and DAGs by two inde-
pendent but mutually complementary approaches.7,8 The first
approach, the pharmacophore-guided approach, seeks to reduce
the entropic penalty associated with DAG binding by constrain-
APP is also cleaved by the R-secretase within the Aâ
sequence at Lys686-Leu689 to release a large secreted fragment
termed sAPPR and a second fragment C83, which is further
processed to the N-terminally truncated Aâ variant called p3.16
These fragments are of no pathological significance and rather
have shown neuroprotection and synaptotrophic effects.17 Thus,
enhancement of R-secretase activity leads to a reduction of the
* To whom correspondence should be addressed. Phone: 82-2-880-7846.
Fax: 82-2-888-0649. E-mail: jeewoo@snu.ac.kr.
† College of Pharmacy, Seoul National University.
‡ College of Medicine, Seoul National University.
# Digital Biotech.
| Laboratory of Medicinal Chemistry, NIH.
§ Laboratory of Cellular Carcinogenesis and Tumor Promotion, NIH.
10.1021/jm0509391 CCC: $33.50 © 2006 American Chemical Society
Published on Web 02/14/2006

Branched Diacylglycerol-Lactones
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 6 2029
Scheme 1a
Chart 1
APP substrate that is available for Aâ formation. Conversely,
since the secretases seem to compete for a single pool of APP,
decreased R-secretase processing causes elevated Aâ produc-
tion by shunting more APP into the â-secretase pathway,
resulting in increased Aâ deposition.18,19 Thus, the activation
of R-secretase is an attractive pathway to lower Aâ deposition,
complementing strategies for inhibition of â- and γ-secretases.
PKC is known to participate in the processing of APP.
Although cells contain a certain level of basal R-secretase
activity, PKC activators, such as phorbol esters and benzo-
lactams, substantially enhance this proteolysis through R-secre-
tase activation, leading to enhanced production of sAPPR.15,20
Moreover, activation of receptors that work through protein
kinase C can augment R-secretase cleavage of APP with
concomitant reduction in â-secretase processing. Thus, these
ligands are potential anti-AD drug candidates along with â- and
γ-secretase inhibitors.
a Reagents and Conditions: (a) LiHMDS, [(CH3)2CHCH2]2CHCH2CHO,
-78 °C, THF; (b) (1) MsCl, NEt3, CH2Cl2, (2) DBU; (c) BCl3, CH2Cl2,
-78 °C; (d) RCOCl, NEt3, CH2Cl2; (e) (NH4)2Ce(NO3)6, CH3CN-H2O, 0
°C.
Scheme 2a
In this work, we investigated the structure-activity relation-
ships of the highly potent DAG-lactone scaffold (1) and
evaluated the abilities of potent DAG-lactones to inhibit
[3H]PDBu binding to PKC-R. We then evaluated a subset of
these DAG-lactones as potential anti-amyloidic agents, deter-
mining their ability to lead to activation of the R-secretase by
measuring the generation of sAPPR, a hydrolyzed product from
APP.
a Reagents and Conditions: (a) (COCl)2, DMSO, NEt3, CH2Cl2, -78
°C to rt; (b) Ph3PCHCO2tBu, CH2Cl2, rt; (c) (NH4)2Ce(NO3)6, CH3CN-
H2O, 0 °C.
2 equiv of isopentenyl bromide (Scheme 3). The syntheses of
δ-lactone surrogates (24-26) were initially attempted employing
the protocol of direct aldol condensation to the δ-lactone moiety
with branched aldehydes as described in Scheme 1. Unfortu-
nately, the condensation resulted in very low yield, and the
strategy was therefore revised to the method described in
Scheme 4. The intermediate 18, previously reported,21 was
converted to the corresponding aldehyde and then elongated by
two carbons in two steps. Aldol condensation of 21 with
aldehyde and subsequent elimination produced 22 as an
intractable mixture of E/Z isomers. The mixture underwent
cyclization under acidic conditions to provide lactone 23, whose
geometric isomers, 23a and 23b, could be separated at this stage
by column chromatography. With each isomer, the complete
syntheses of 24-26 were performed individually.
Design and Synthesis
The lead branched DAG-lactone (1) possesses high binding
affinity for PKCR. We used three approaches to optimize its
activity. First, the 5-pivaloyl group of 1 was substituted with
diverse acyl groups and with tert-butyl acrylate as an isostere,
while the 3-alkylidene group was fixed as the 3,3-diisobutyl-
propylidene group. Second, the 3-(3,3-diisobutylpropylidene)
chain was replaced by 3,3-diisopentyl or 3,3-diisopentenyl
groups to change the disposition of the side chain. Finally, the
γ-lactone moiety was replaced with a one-carbon-enlarged
δ-lactone scaffold.
The syntheses of 3-(3,3-diisobutylpropylidene) DAG-lactone
analogues (6-10) were completed from lactone 318 employing
a well-established methodology developed in our laboratory
involving aldol condensation with 3,3-diisobutyl-1-propion-
aldehyde followed by elimination of the â-hydroxy lactone
intermediate. Consistent with previously synthesized DAG-
lactones, the E/Z geometry was assigned based on the relative
chemical shift of vinyl protons in which the vinyl proton of the
E isomer was farther downfield than that of the Z isomer by δ
) 0.6-0.8. After separation of the geometric isomers 4a and
4b, the isomers individually were converted to the corresponding
DAG-lactones with different 5-acyl groups by conventional
methods (Scheme 1). The syntheses of the tert-butyl acrylate
analogues (12, 13) were accomplished using Wittig olefination
from aldehyde intermediate 11, which was prepared from 5 by
Swern oxidation (Scheme 2). 3,3-Bisalkylated lactones (15, 16)
were synthesized from lactone 3 by the enolate alkylation using
Results and Discussion
Binding Studies. The interaction of the target DAG-lactones
with PKC was assessed in terms of the ability of the ligands to
displace bound [20-3H]phorbol 12,13-dibutyrate (PDBu) from
recombinant PKC-R in the presence of phosphatidylserine as
previously described.10 The IC50 values were determined by
fitting the data points to the theoretical competition curve. The
Ki values for inhibition of binding were calculated from the
corresponding IC50 values (Tables 1-3). On the basis of the
lead branched DAG-lactones (1a, Ki ) 2.90 nM; 1b, Ki ) 4.51
nM) previously communicated, we fully explored the structure-
activity relationships of the pharmacophoric regions. The cLog

2030 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 6
Lee et al.
Scheme 3a
Table 1. Binding Affinities of 3-Alkylidene DAG-γ-Lactones to PKC-R
no.
R
E/Z CLog P
Ki (nM)
1a
1b
2a
6a
6b
7a
7b
8a
8b
9ab
CH2OCOC(CH3)3
CH2OCOC(CH3)3
CH2OCOC(CH3)3
CH2OCOC5H11
CH2OCOC5H11
CH2OCOC7H15
CH2OCOC7H15
CH2OCOPh
Z
E
Z
Z
E
Z
E
Z
E
Z
E
Z
Z
E
E
5.03
5.03
5.03
5.63
5.63
6.61
6.61
5.12
5.12
6.88
6.88
7.86
5.30
5.30
5.30
2.90 ((0.35)
4.51 ((0.49)
1.45 ((0.20)
3.78 ((0.18)
6.18 ((0.77)
4.97 ((0.17)
6.04 ((0.55)
6.66 ((0.90)
16.1 ((0.4)
6.87 ((0.56)
4.46 ((0.37)
6.88 ((0.67)
18.0 ((1.6)
173 ((16)
CH2OCOPh
CH2OCOCH2CH(i-Pr)2
9bb CH2OCOCH2CH(i-Pr)2
10a CH2OCOCH2CH[CH2(i-Pr)]2
12a (E)-CHdCHCO2C(CH3)3
12b (E)-CHdCHCO2C(CH3)3
13b (Z)-CHdCHCO2C(CH3)3
a Reagents and Conditions: (a) LiHMDS, (CH3)2CdCHCH2Br, -78 °C,
HMPA, THF; (b) BCl3, CH2Cl2, -78 °C; (c) H2, Pd-C, EtOH; (d)
(CH3)3CCOCl, NEt3, CH2Cl2; (e) (NH4)2Ce(NO3)6, CH3CN-H2O, 0 °C.
21700 ((1600)
P values were calculated according to the fragment-based
program KOWWIN.22
a Chiral R isomer.11 b Reference 9.
We modified the C5-acyl moiety (pivaloyl group in 1) by
substituting with linear acyl groups (6, R ) C5H11; 7, R )
C7H15), an aryl group (8, R ) Ph), and bulkier branched acyl
groups (9, R ) CH2CH(i-Pr)2; 10, R ) CH2CH[CH2(i-Pr)]2).
Although they still retained high binding affinities for PKC-R
(Ki ) 3.78-16.1 nM), the potencies did not exceed that of the
lead compound despite their higher log P values.
Previously, we demonstrated that the isosteric substitutions
of the C5-ester moiety in DAG-lactones with amide or N-
hydroxyamide led to a substantial loss of activity.9,23 Thus, as
a second approach we replaced the C5-acyloxy moiety with tert-
butyl E/Z-acrylate (12, E; 13, Z), a transposed isostere of
5-pivaloyloxymethyl. The result revealed that the activities were
very sensitive to the geometry of the acrylate. Whereas the
replacement with tert-butyl E-acrylate led to moderate reductions
in binding affinities (6-fold in 12a, 38-fold in 12b) as compared
to 1a and 1b, respectively, tert-butyl Z-acrylate (13) was
observed to have very low affinity. To date, the SAR analysis
of the C5-acyl group in a series of 3-(3,3-diisobutylpropylidene)
DAG-lactones has indicated that the pivaloyl group is optimal
as the C5-acyl group.
After identifying the optimizing group for the C5-ester moiety,
we next turned to the SAR of the 3-alkylidene group in lead 1.
We previously found that, in a series of 3-alkylidenes, the
branched alkyl chains conferred higher binding affinities and
lower lipophilicities than did the corresponding straight chains.10
Scheme 4a
a Reagents and Conditions: (a) ref 21; (b) 4-NMO, OsO4, NaIO4, acetone-H2O; (c) Ph3PCHCO2tBu, toluene; (d) H2, Pd-C, EtOAc; (e) p-TsOH, acetone;
(f) LiHMDS, [(CH3)2CHCH2]2CHCH2CHO, -78 °C, THF; (g) (1) MsCl, NEt3, CH2Cl2, (2) DBU; (h) CF3CO2H, CH2Cl2; (i) RCOCl, NEt3, DMAP, CH2Cl2;
(j) (NH4)2Ce(NO3)6, CH3CN-H2O, 0 °C.

Branched Diacylglycerol-Lactones
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 6 2031
Table 4. Activation of R-Secretase by Branched DAG-Lactones
Table 2. Binding Affinities of 3,3-Bisalkyl DAG-γ-Lactones to PKC-R
compound
sAPPR secretion (% of control)a
control
PDBu
1a
1b
2
7a
7b
8a
8b
100
185 ((19)
177 ((16)
133 ((7)
209 ((22)
158 ((8)
141 ((12)
157 ((9)
131 ((10)
225 ((7)
200 ((8)
no.
R
CLog P
Ki (nM)
15
16
CH2CHdC(CH3)2
CH2CH2CH(CH3)2
4.49
4.66
2100 ((260)
18300 ((1600)
9b
12a
Table 3. Binding Affinities of Branched DAG-δ-Lactones to PKC-R
a DAG-lactones increase production of sAPPR after challenge to W4
cells. The activation represented % of control. Values represent the mean
( SEM of three experiments.
no.
R
E/Z
CLog P
Ki (nM)
24a
24b
25b
26b
C(CH3)3
C(CH3)3
C5H11
Z
E
E
E
5.52
5.52
6.12
7.10
28 ((1)
48 ((2)
147 ((4)
129 ((8)
C7H15
This time we decided to replace the 3-alkylidene group with a
3,3-bis-alkyl group. In this study, we introduced isopentenyl
(15) and isopentyl (16) groups at the 3-position because they
have similar numbers of carbons as does the 3,3-diisobutyl-
propylidene group in 1. Unfortunately, incorporation of two
branched side chains led to a dramatic (more than 1000-fold)
reduction in binding affinity.
Finally, we investigated the SAR of the lactone ring in the
lead compound. It was previously observed that the substitutions
with five-membered ring isosteres, such as lactam, N-hydroxy-
lactam, and cyclopentanone, did not further optimize the potent
lead PKC ligand.9,24 Thus, we explored six-membered lactone
surrogates (24-26) as an approach to ring expansion. δ-Lactone
surrogates (24a, 24b, 25, and 26) retained good binding affinities
but with 10-20-fold lower potencies as compared to the
corresponding parent compounds (1a, 1b, 6b, and 7b), respec-
tively. Interestingly, the reduction in potencies upon ring
expansion was very consistent, implying that a series of
δ-lactone surrogates has a SAR pattern very similar to that found
in the γ-lactone series.
R-Secretase Activation in Vitro. The abilities of the
synthesized DAG-lactones to activate R-secretase were evaluated
by measuring the amount of secreted sAPPR in W4 cells,25
which are a human APP695 transfected rat neuroblastoma cell
line.26 The amount of secreted sAPPR, the hydrolysis product
of APP upon cleavage by the R-secretase, was measured by
gel electrophoresis and immunoblot analysis with monoclonal
antibody 6E10 that recognizes the N-terminus of the Aâ peptide.
The increased amount of sAPPR reflects increased R-secretase
activity.25,27 The intensity of the sAPPR band in the experimental
groups was analyzed by densitometry and compared to that of
the control group. Three independent experiments were con-
ducted for each compound at a concentration of 1 µM. The
results are shown in Table 4 and Figure 1, and phorbol 12,13-
dibutyrate (PBDu) was used as a reference compound.
Figure 1. DAG-lactone 2 activated R-secretase activity in a dose-
dependent manner. (A) Western blot of the amount of secreted sAPPR
as a function of the concentration of DAG-lactone 2. Results shown
are representative of three independent experiments. (B) Densitometric
analysis of the amount of secreted sAPPR as a function of the
concentration of DAG-lactone 2. Values indicate the mean ( SEM of
three experiments (*, P < 0.05; **, P < 0.01, paired t-test).
sAPPR correlated well with the binding affinities to PKC-R for
a series of DAG-lactones with the same log P values (1a vs
1b, 7a vs 7b, and 8a vs 8b). In addition, for pairs of compounds
with similar Ki values for PKCR binding but with different
lipophilicities, the secretion was enhanced for the compound
with the greater lipophilicity (7b vs 9b and 8b vs 12a). These
results imply that both PKC binding affinity and lipophilicity
contribute to R-secretase activation leading to sAPPR secretion.
To further explore quantitatively the effect of DAG-lactones
on sAPPR secretion, two potent PKC ligands, 1a (Ki ) 2.9 nM)
and its active enantiomer 2 (Ki ) 1.45 nM),11 were assayed
and compared with PDBu (1 µM). As shown in Table 4, the
two ligands exhibited significantly enhanced secretion of sAPPR.
The relative levels of secreted sAPPR induced by 1a and 2 were
177 ( 16% and 209 ( 22% (mean ( SEM), respectively,
compared to control (p ) 0.068 and 0.002, respectively, paired
t-test). These values are similar to the level of secretion induced
by PDBu (185 ( 19%). Furthermore, sAPPR secretion by 2
Nine selected DAG-lactones with high binding affinities were
initially screened for induction of sAPPR secretion at a
concentration of 1 µM (Table 4). As anticipated, all tested
compounds showed a substantial effect (130-225%) as com-
pared to the vehicle control (100%). The amount of secreted

2032 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 6
Lee et al.
2 × CHMe2 and CH(i-Bu)2), 1.10 (t, 4 H, 2 × CHCH2CHMe2),
increased in a dose-dependent manner as illustrated in Figure
1, in which the level of secreted sAPPR increased as the
concentration of 2 increased up to 2 µM. These results
demonstrate that the DAG-lactones enhanced sAPPR secretion
through R-secretase activation in a fashion similar to the phorbol
esters.
0.86 (d, 12 H, 4 × CH3); IR (neat) 1760 (CdO), 1680 cm-1
.
1
4b: Rf)0.60 (EtOAc:hexanes)1:3). H NMR (CDCl3) δ 7.25
(m, 5 H, phenyl), 6.75 (m, 5 H, >CdCH and 4-methoxyphenyl),
4.53 (s, 2 H, PhCH2O), 3.98 (AB dd, 2 H, J ) 9.7 and 19.5 Hz,
CH2Ar), 3.69 (s, 3 H, OCH3), 3.57 (AB dd, 2 H, J ) 10.2 and
18.0 Hz, BnCH2O), 2.78 (m, 2 H, H-4), 2.08 (m, 2 H, >CdCH-
CH2), 1.5-1.7 (m, 3 H, 2 × CHMe2 and CH(i-Bu)2), 1.04 (t, 4 H,
2 × CHCH2CHMe2), 0.80 (d, 12 H, 4 × CH3); IR (neat) 1759
In conclusion, we investigated a series of branched DAG-
lactones as PKC ligands and R-secretase activators based on a
potent lead PKC ligand (1). The C5-acyl group, 3-alkylidene,
and lactone ring in 1 were systematically modified, and
structure-activity relationships within the series have been
analyzed. The measurement of the amount of secreted sAPPR
generated from R-secretase activation by ligands indicated that
they were potent R-secretase activators with potencies which
correlated with their PKC binding affinities and lipophilicities.
Further investigation with 1a and its active enantiomer 2
demonstrated that they induce as high or higher a level of
secreted sAPPR as does PDBu, and the activity was dose
dependent. Our results support the approach of using PKC
ligands to enhance sAPPR secretion by R-secretase activation
and thus reduce plaque burden and suggest that DAG-lactones
are potential anti-Alzheimer’s drug candidate.
(CdO), 1680 cm-1
.
5-Hydroxymethyl-3-[(Z/E)-3-isobutyl-5-methylhexylidene]-5-
[(4-methoxyphenoxy)methyl]tetrahydro-2-furanone (5a,b). A
cooled solution of 4a (or 4b) (1.16 g, 2.35 mmol) in CH2Cl2 (20
mL) at -78 °C was treated with boron trichloride (4.70 mL, 1 M
in CH2Cl2, 4.7 mmol) and stirred for 2 h. The reaction mixture
was quenched with saturated NaHCO3 solution at -78 °C and
warmed to room temperature. The resulting solution was extracted
with diethyl ether several times. The combined organic layer was
washed with water followed by brine, dried over MgSO4, and
filtered. The filtrate was concentrated in vacuo, and the residue
was purified by flash column chromatography over silica gel with
EtOAc:hexanes (1:1) as eluent to afford 5a (or 5b) as an oil (0.94
g, 99%).
5a (Z isomer): 1H NMR (CDCl3) δ 6.82 (s, 4 H, Ar), 6.26 (m,
1 H, >CdCH), 4.02 (AB dd, 2 H, J ) 9.5 and 25.6 Hz, CH2Ar),
3.82 (AB ddd, 2 H, CH2OH), 3.77 (s, 3 H, OCH3), 2.98 (m, 1 H,
H-4a), 2.88 (m, 1 H, H-4b), 2.70 (m, 2 H, > CdCH-CH2), 1.91
(t, 1 H, OH), 1.5-1.7 (m, 3 H, 2 × CHMe2 and CH(i-Bu)2), 1.10
(t, 4 H, 2 × CHCH2CHMe2), 0.86 (m, 12 H, 4 × CH3).
5b (E isomer): 1H NMR (CDCl3) δ 6.82 (m, 5 H, >CdCH and
Ar), 4.02 (AB dd, 2 H, J ) 9.5 and 26.3 Hz, CH2Ar), 3.83 (AB
ddd, 2 H, CH2OH), 3.76 (s, 3 H, OCH3), 2.92 (m, 1 H, H-4a), 2.77
(m, 1 H, H-4b), 2.15 (m, 2 H, >CdCH-CH2), 1.93 (t, 1 H, OH),
1.55-1.75 (m, 3 H, 2 × CHMe2 and CH(i-Bu)2), 1.10 (m, 4 H, 2
× CHCH2CHMe2), 0.86 (m, 12 H, 4 × CH3).
Experimental Section
All chemical reagents were commercially available. Melting
points were determined on a Melting Point Bu¨chi B-540 apparatus
and are uncorrected. Silica gel column chromatography was
performed on silica gel 60, 230-400 mesh, Merck. Proton NMR
spectra were recorded on a JEOL JNM-LA 300 at 300 MHz.
Chemical shifts are reported in ppm units with Me4Si as a reference
standard. Infrared spectra were recorded on a Perkin-Elmer 1710
Series FTIR. Mass spectra were recorded on a VG Trio-2 GC-MS.
Elemental analyses were performed with an EA 1110 Automatic
Elemental Analyzer, CE Instruments.
General Procedure for Acylation and Deprotection. A stirred
solution of 5a (or 5b) (404 mg, 1 mmol), (dimethylamino)pyridine
(12 mg, 0.1 mmol), and triethylamine (0.28 mL, 2 mmol) in CH2Cl2
(20 mL) was cooled to -10 °C and treated slowly with acyl chloride
(1.4 mmol). The reaction mixture was warmed to room temperature
and stirred for 3 h. The mixture was quenched with water and
extracted with diethyl ether several times. The combined organic
layer was washed with water followed by brine, dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo, and the residue
was purified by flash column chromatography over silica gel with
an appropriate eluent.
A stirred solution of the above ester in acetonitrile-water (4:1,
25 mL) was cooled to -0 °C and treated with ammonium cerium
nitrate (1.1 g, 2 mmol). Stirring in an ice bath continued for 40
min, and the reaction mixture was diluted with CH2Cl2. The organic
layer was washed with water followed by brine, dried over MgSO4,
and filtered. The filtrate was concentrated in vacuo, and the residue
was purified by flash column chromatography over silica gel with
an appropriate eluent to give 6-10.
5-[(Benzyloxy)methyl]-3-[(Z/E)-3-isobutyl-5-methylhexylidene]-
5-[(4-methoxyphenoxy)methyl]tetrahydro-2-furanone (4a,b). A
cooled solution of 3 (2 g, 5.85 mmol) in THF (40 mL) at -78 °C
was treated dropwise with lithium bis(trimethylsilyl)amide (8.2 mL,
1.0 M in THF) and stirred for 20 min. A solution of 3-isobutyl-
5-methylhexanal (1.39 g, 8.2 mmol) was added dropwise to the
lithium enolate at the same temperature. After being stirred at -78
°C for 3 h, the reaction was quenched by the slow addition of a
saturated aqueous solution of ammonium chloride and then warmed
to room temperature. The aqueous layer was extracted three times
with diethyl ether, and the combined organic extracts were washed
with water followed by brine, dried over MgSO4, and filtered. The
filtrate was concentrated in vacuo, and the residue was purified by
flash column chromatography over silica gel with EtOAc:hexanes
(1:3) as eluent to afford â-hydroxylactone as an oil (2.85 g, 95%)
A cooled solution of â-hydroxylactone (2.85 g, 5.56 mmol) in
CH2Cl2 (40 mL) at 0 °C was treated with triethylamine (1.55 mL,
11.12 mmol) followed by methanesulfonyl chloride (0.65 mL, 8.34
mmol). The reaction mixture was warmed to room temperature and
stirred for 3 h. 1,8-Diazabicyclo[5.4.0]undec-7-ene (3.4 mL, 22.24
mmol) was added, and the resulting solution was stirred for 30
min at ambient temperature. The reaction mixture was neutralized
with acetic acid and diluted with CH2Cl2. The organic layer was
washed with water followed by brine, dried over MgSO4, and
filtered. The filtrate was concentrated in vacuo, and the residue
was purified by flash column chromatography over silica gel with
EtOAc:hexane (1:3) as eluent to afford 4a (Z isomer) and 4b (E
isomer) as an oil, respectively (ratio ) 5:4, 2.09 g, 76%).
5-Hexanoyloxymethyl-5-hydroxymethyl-3-[(Z/E)-3-isobutyl-
5-methylhexylidene]tetrahydro-2-furanone (6a,b). 6a (Z iso-
mer): 63% yield, oil; 1H NMR (CDCl3) δ 6.26 (m, 1H, >CdCH),
4.29 (AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 4.16 (AB d, 1 H, J )
11.9 Hz, CH2OCOR), 3.66 (ddd, 2 H, CH2OH), 2.91 (m, 1 H, H-4a),
2.6-2.75 (m, 3 H, H-4b and >CdCH-CH2), 2.34 (t, 2 H, J ) 7.3
Hz, COCH2), 2.10 (t, 1 H, OH), 1.55-1.7 (m, 5 H, COCH2CH2, 2
× CHMe2 and CH(i-Bu)2), 1.30 (m, 4 H, CO(CH2)2(CH2)2CH3),
1.09 (m, 4 H, 2 × CHCH2CHMe2), 0.85-0.92 (m, 15 H, 5 × CH3);
IR (neat) 3456 (OH), 1755 (CdO) cm-1; MS (FAB) m/z 397
(MH+). Anal. (C23H40O5) C, H.
1
4a: Rf ) 0.62 (EtOAc:hexanes ) 1:3). 1H NMR (CDCl3) δ 7.30
(m, 5 H, phenyl), 6.81 (s, 4 H, 4-methoxyphenyl), 6.21 (m, 1 H,
>CdCH), 4.59 (AB dd, 2 H, J ) 12.4 and 14.4 Hz, PhCH2O),
4.02 (AB dd, 2 H, J ) 9.7 and 22.7 Hz, CH2Ar), 3.76 (s, 3 H,
OCH3), 3.66 (AB dd, 2 H, J ) 10.2 and 18.0 Hz, BnCH2O), 2.92
(m, 2 H, H-4), 2.70 (m, 2 H, >CdCH-CH2), 1.55-1.7 (m, 3 H,
6b (E isomer): 65% yield, oil; H NMR (CDCl3) δ 6.80 (m, 1
H, >CdCH), 4.30 (AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 4.16
(AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 3.68 (AB ddd, 2 H, J )
7.1, 11.9 and 24.6 Hz, CH2OH), 2.81 (m, 1 H, H-4a), 2.64 (m, 1
H, H-4b), 2.33 (t, 2 H, J ) 7.3 Hz, COCH2), 2.1-2.2 (m, 3 H,
>CdCH-CH2 and OH), 1.55-1.75 (m, 5 H, COCH2CH2, 2 ×

Branched Diacylglycerol-Lactones
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 6 2033
CHMe2 and CH(i-Bu)2), 1.30 (m, 4 H, CO(CH2)2(CH2)2CH3), 1.10
(m, 4 H, 2 × CHCH2CHMe2), 0.88 (m, 15 H, 5 × CH3); IR (neat)
3444 (OH), 1747 (CdO), 1681 cm-1; MS (FAB) m/z 397 (MH+).
Anal. (C23H40O5) C, H.
2 × CH(i-Bu)2), 1.0-1.15 (m, 8 H, 4 × CHCH2CHMe2), 0.75-
MS (FAB) m/z 467 (MH+). Anal. (C28H50O5) C, H.
0.95 (m, 24 H, 8 × CH3); IR (neat) 3440 (OH), 1685 (CdO) cm-1
;
5-Formyl-3-[(Z/E)-3-isobutyl-5-methylhexylidene]-5-[(4-meth-
oxyphenoxy)methyl]tetrahydro-2-furanone (11a,b). A cooled
solution of oxalyl chloride (0.14 mL, 1.61 mmol) in CH2Cl2 (13
mL) at -78 °C was treated with DMSO (0.17 mL, 2.48 mmol)
followed by a solution of 5a (or 5b) (0.5 g, 1.24 mmol) in CH2Cl2
(7 mL). After being stirred at -78 °C for 1 h, the reaction mixture
was treated with triethylamine (0.43 mL, 3.1 mmol) and allowed
to warm to room temperature. The mixture was washed with water
and brine, dried over MgSO4, and filtered. The filtrate was
concentrated in vacuo, and the residue was purified by flash column
chromatography over silica gel with EtOAc:hexanes (1:1) as eluent
to afford 11a (or 11b) as an oil (0.493 g, 99%).
5-Hydroxymethyl-3-[(Z/E)-3-isobutyl-5-methylhexylidene]-5-
octanoyloxymethyltetrahydro-2-furanone (7a,b). 7a (Z isomer):
1
64% yield, oil; H NMR (CDCl3) δ 6.25 (m, 1H, >CdCH), 4.28
(AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 4.16 (AB d, 1 H, J ) 11.9
Hz, CH2OCOR), 3.65 (AB dd, 2 H, J ) 27.9 and 12.1 Hz, CH2OH),
2.90 (m, 1 H, H-4a), 2.6-2.75 (m, 3 H, H-4b and >CdCH-CH2),
2.33 (t, 2 H, J ) 7.3 Hz, COCH2), 1.55-1.7 (m, 5 H, COCH2CH2,
2 × CHMe2 and CH(i-Bu)2), 1.30 (m, 8 H, CO(CH2)2(CH2)4CH3),
1.10 (m, 4 H, 2 × CHCH2CHMe2), 0.88 (m, 15 H, 5 × CH3); IR
(neat) 3447 (OH), 1745 (CdO), 1670 cm-1; MS (FAB) m/z 425
(MH+). Anal. (C25H44O5) C, H.
7b (E isomer): 96% yield, oil; H NMR (CDCl3) δ 6.80 (m, 1
11a (Z isomer): 1H NMR (CDCl3) δ 9.81 (s, 1 H, CHO), 6.82
(s, 4 H, 4-methoxyphenyl), 6.32 (m, 1 H, >CdCH), 4.21 (s, 2 H,
CH2Ar), 3.76 (s, 3 H, OCH3), 3.06 (m, 2 H, H-4), 2.70 (m, 2 H,
>CdCH-CH2), 1.5-1.7 (m, 3 H, 2 × CHMe2 and CH(i-Bu)2),
1.10 (t, 4 H, 2 × CHCH2CHMe2), 0.86 (m, 12 H, 4 × CH3).
11b (E isomer): 1H NMR (CDCl3) δ 9.75 (s, 1 H, CHO), 6.74
(m, 5 H, 4-methoxyphenyl and >CdCH), 4.0 (m, 2 H, CH2Ar),
3.69 (s, 3 H, OCH3), 2.95 (m, 2 H, H-4), 2.10 (m, 2 H, >CdCH-
CH2), 1.5-1.7 (m, 3 H, 2 × CHMe2 and CH(i-Bu)2), 1.10 (t, 4 H,
2 × CHCH2CHMe2), 0.86 (m, 12 H, 4 × CH3).
1
H, >CdCH), 4.30 (AB d, 1 H, J ) 11.7 Hz, CH2OCOR), 4.16
(AB d, 1 H, J ) 11.7 Hz, CH2OCOR), 3.68 (AB ddd, 2 H, CH2OH),
2.81 (m, 1 H, H-4a), 2.63 (m, 1 H, H-4b), 2.33 (t, 2 H, J ) 7.6 Hz,
COCH2), 2.13 (t, 2 H, >CdCH-CH2), 2.06 (t, 1 H, OH), 1.5-
1.75 (m, 5 H, COCH2CH2, 2 × CHMe2 and CH(i-Bu)2), 1.28 (m,
8 H, CO(CH2)2(CH2)4CH3), 1.10 (m, 4 H, 2 × CHCH2CHMe2),
0.88 (m, 15 H, 5 × CH3); IR (neat) 3447 (OH), 1745 (CdO), 1670
cm-1; MS (FAB) m/z 425 (MH+). Anal. (C25H44O5) C, H.
5-Benzoyloxymethyl-5-hydroxymethyl-3-[(Z/E)-3-isobutyl-5-
methylhexylidene]tetrahydro-2-furanone (8a,b). 8a (Z isomer):
65% yield, oil; 1H NMR (CDCl3) δ 7.92 (d, 2 H, Ph), 7.52 (t, 1 H,
Ph), 7.37 (t, 2 H, Ph), 6.19 (m, 1H, >CdCH), 4.40 (AB dd, 2 H,
J ) 21 and 11.9 Hz, CH2OCOR), 3.64 (ddd, 2H, CH2OH), 2.90
(m, 1 H, H-4a), 2.6-2.75 (m, 3 H, H-4b and >CdCH-CH2), 2.34
(t, 2 H, J ) 7.3 Hz, COCH2), 1.60 (m, 3 H, 2 × CHMe2, CH(i-
Bu)2), 1.18 (d, 2 H, CHCH2CHMe2), 1.01 (t, 2 H, CHCH2CHMe2),
0.78 (d, 12 H, 4 × CH3); IR (neat) 3447 (OH), 1745 (CdO), 1670
cm-1; MS (FAB) m/z 403 (MH+). Anal. (C24H34O5) C, H.
5-[(E)-3-(tert-Butoxy)-3-oxo-1-propenyl]-5-hydroxymethyl-3-
[(Z)-3-isobutyl-5 -methylhexylidene]tetrahydro-2-furanone (12a).
A solution of 11a (0.13 g, 0.323 mmol) in CH2Cl2 (40 mL) was
treated with (tert-butoxycarbonylmethylene)triphenylphosphorane
(0.186 g, 0.485 mmol) and stirred at room temperature for 24 h.
The reaction mixture was concentrated in vacuo, and the residue
was purified by flash column chromatography over silica gel with
EtOAc:hexanes (1:3) as eluent to afford only E-unsaturated ester
as an oil (0.16 g, 99%).
1
8b (E isomer): 98% yield, oil; H NMR (CDCl3) δ 8.10 (d, 2
A cooled solution of the above unsaturated ester (0.16 g, 0.32
mmol) in acetonitrile (10 mL) and water (4 mL) in an ice bath was
treated with CAN (ammonium cerium nitrate, 0.526 g, 0.96 mmol).
The reaction mixture was warmed to room temperature and stirred
for 1 h. The resulting mixture was filtered through Celite with
additional CH2Cl2, and the filtrate was concentrated in vacuo. The
residue was purified by flash column chromatography over silica
gel with EtOAc:hexanes (1:3) as eluent to afford 12a as a white
solid (0.066 g, 52%).
H, Ph), 7.60 (t, 1 H, Ph), 7.44 (t, 2 H, Ph), 6.80 (m, 1 H, >CdCH),
4.47 (AB dd, 2 H, J ) 11.9 and 21.2 Hz, CH2OCOR), 3.76 (AB
dd, 2 H, J ) 12.2 and 24.1 Hz, CH2OH), 2.88 (m, 1 H, H-4a),
2.73 (m, 1 H, H-4b), 2.10 (m, 2 H, >CdCH-CH2), 1.5-1.7 (m,
3 H, 2 × CHMe2 and CH(i-Bu)2), 1.06 (m, 4 H, 2 × CHCH2-
CHMe2), 0.83 (d, 12 H, 4 × CH3); IR (neat) 3441 (OH), 1686
(CdO) cm-1; MS (FAB) m/z 403 (MH+). Anal. (C24H34O5) C, H.
5-Hydroxymethyl-3-[(Z/E)-3-isobutyl-5-methylhexylidene]-5-
(3-isopropyl-4-methyl-pentanoyloxymethyl)tetrahydro-2-fura-
1
12a: mp 135 °C; H NMR (CDCl3) δ 6.74 (d, 1 H, J ) 15.6
1
none (9a,b). 9a (Z isomer): 28% yield, oil; H NMR (CDCl3) δ
Hz, CH)CHCO2(CH3)3), 6.22 (m, 1 H, >CdCH), 6.04 (d, 1 H, J
) 15.6 Hz, CHdCHCO2(CH3)3), 3.74 (AB dd, 1 H, J ) 6.1 and
12.2 Hz, CH2OH), 3.60 (AB dd, 1 H, J ) 6.1 and 12.2 Hz, CH2OH),
3.12 (m, 1 H, H-4a), 2.58-2.76 (m, 3 H, H-4b and >CdCH-
CH2), 1.87 (t, 1 H, J ) 6.1 Hz, OH), 1.55-1.7 (m, 3 H, 2 × CHMe2
and CH(i-Bu)2), 1.45 (s, 9 H, CO2C(CH3)3), 1.05 (m, 4 H, 2 ×
CHCH2CHMe2), 0.84 (m, 12 H, 4 × CH3); IR (neat) 3433, 1715
cm-1; MS (FAB) m/z 395 (MH+). Anal. (C23H38O5) C, H.
5-[(E/Z)-3-(tert-Butoxy)-3-oxo-1-propenyl]-5-hydroxymethyl-
3-[(E)-3-isobutyl-5-methylhexylidene]tetrahydro-2-furanone (12b
and 13b). By following the procedure described for the synthesis
of 12a, 12b (5E isomer) and 13b (5Z isomer) with a ratio of 1:1
were obtained with 64% yield from 11b.
6.26 (m, 1 H, >CdCH), 4.27 (AB d, 1 H, J ) 11.9 Hz,
CH2OCOR), 4.14 (AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 3.66 (AB
dd, 2 H, J ) 11.9 and 24.6 Hz, CH2OH), 2.85-2.95 (m, 1 H, H-4a),
2.6-2.75 (m, 1 H, H-4b and >CdCH-CH2), 2.21 (d, 2 H, J )
5.8 Hz, COCH2), 2.04 (bs, 1 H, OH), 1.55-1.8 (m, 6 H, 4 ×
CHMe2, CH(i-Pr)2 and CH(i-Bu)2), 1.09 (m, 4 H, 2 × CHCH2-
CHMe2), 0.75-0.95 (m, 24 H, 8 × CH3); IR (neat) 3440 (OH),
1685 (CdO) cm-1; MS (FAB) m/z 439 (MH+). Anal. (C26H46O5)
C, H.
9b (E isomer): 32% yield, oil;1H NMR (CDCl3) δ 6.80 (m, 1
H, >CdCH), 4.29 (AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 4.14
(AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 3.68 (AB dd, 2 H, J ) 11.9
and 24.6 Hz, CH2OH), 2.81 (m, 1 H, H-4a), 2.64 (m, 1 H, H-4b),
2.20 (d, 2 H, J ) 5.8 Hz, COCH2), 2.13 (m, 2 H, >CdCH-CH2),
2.04 (bs, 1 H, OH), 1.55-1.8 (m, 6 H, 4 × CHMe2, CH(i-Pr)2 and
CH(i-Bu)2), 1.10 (m, 4 H, 2 × CHCH2CHMe2), 0.75-0.9 (m, 24
H, 8 × CH3); IR (neat) 3440 (OH), 1685 (CdO) cm-1; MS (FAB)
m/z 439 (MH+). Anal. (C26H46O5) C, H.
12b: Rf ) 0.5 (EtOAc:hexanes ) 1:2); 1H NMR (CDCl3) δ 6.80
(m, 1 H, >CdCH), 6.76 (d, 1 H, J ) 15.6 Hz, CHdCHCO2(CH3)3),
6.05 (d, 1 H, J ) 15.6 Hz, CHdCHCO2(CH3)3), 3.76 (AB dd, 1
H, J ) 6.1 and 12.2 Hz, CH2OH), 3.62 (AB dd, 1 H, J ) 6.1 and
12.2 Hz, CH2OH), 3.02 (m, 1 H, H-4a), 2.68 (m, 1 H, H-4b), 2.10
(m, 2 H, >CdCH-CH2), 1.85 (t, 1 H, J ) 6.1 Hz, OH), 1.55-1.7
(m, 3 H, 2 × CHMe2 and CH(i-Bu)2), 1.46 (s, 9 H, CO2C(CH3)3),
1.04 (m, 4 H, 2 × CHCH2CHMe2), 0.84 (d, 12 H, 4 × CH3); IR
(neat) 3435, 1718 cm-1; MS (FAB) m/z 395 (MH+). Anal.
(C23H38O5) C, H.
5-Hydroxymethyl-3-[(Z)-3-isobutyl-5-methylhexylidene]-5-(3-
isobutyl-5-methyl-hexanoyloxymethyl)tetrahydro-2-furanone
1
(10a). 10a (Z isomer): 22% yield, oil; H NMR (CDCl3) δ 6.25
(m, 1 H, >CdCH), 4.27 (AB d, 1 H, J ) 11.9 Hz, CH2OCOR),
4.16 (AB d, 1 H, J ) 11.9 Hz, CH2OCOR), 3.66 (AB dd, 2 H, J
) 11.9 and 24.6 Hz, CH2OH), 2.85-2.95 (m, 1 H, H-4a), 2.6-
2.75 (m, 1 H, H-4b and >CdCH-CH2), 2.25 (d, 2 H, J ) 6.6 Hz,
COCH2), 2.05 (bs, 1 H, OH), 1.55-1.75 (m, 6 H, 4 × CHMe2 and
1
13b: Rf ) 0.45 (EtOAc:hexanes ) 1:2); H NMR (CDCl3) δ
6.72 (m, 1 H, >CdCH), 6.25 (d, 1 H, J ) 12.7 Hz, CH)CHCO2-
(CH3)3), 5.83 (d, 1 H, J ) 12.7 Hz, CHdCHCO2(CH3)3), 3.88 (d,
1 H, J ) 6.8 Hz, CH2OH), 3.24 (m, 1 H, H-4a), 2.82 (m, 1 H,

2034 Journal of Medicinal Chemistry, 2006, Vol. 49, No. 6
Lee et al.
H-4b), 2.16 (t, 1 H, J ) 6.8 Hz, OH), 2.10 (m, 2 H, >CdCH-
CH2), 1.55-1.7 (m, 3 H, 2 × CHMe2 and CH(i-Bu)2), 1.48 (s, 9
H, CO2C(CH3)3), 1.07 (m, 4 H, 2 × CHCH2CHMe2), 0.84 (d, 12
H, 4 × CH3); IR (neat) 3434, 1715 cm-1; MS (FAB) m/z 395
(MH+). Anal. (C23H38O5) C, H.
in vacuo. The residue was purified by flash column chromatography
on silica gel with EtOAc:hexanes (1:1) as eluent to afford 20 as an
1
oil (1.112 g, 97%). H NMR (CDCl3) δ 6.84 (s, 4 H, Ar), 3.89
(AB q, 2 H, J ) 9.2 Hz, CH2OAr), 3.77 (s, 3 H, OCH3), 3.65 (AB
q, 2 H, J ) 11.2 Hz, CH2OH), 2.76 (bs, 1 H, OH), 2.36 (t, 2 H, J
) 6.8 Hz, CH2CO2), 1.6-1.8 (m, 4 H, >CCH2CH2), 1.43 (s, 9 H,
CO2C(CH3)3).
5-[(Benzyloxy)methyl]-5-[(4-methoxyphenoxy)methyl]-3,3-bis-
(3-methyl-2-butenyl)dihydro-2(3H)-furanone (14). A solution of
3 (342 mg, 1 mmol) in THF (10 mL) was cooled to -78 °C and
treated slowly with lithium bis(trimethylsilyl)amide (1.06 M in THF,
2.36 mL, 2.5 mmol). After stirring for 30 min, a solution of
4-bromo-2-methyl-2-butene (0.576 mL, 5 mmol) and hexamethyl-
phosphoramide (4 mL) was added and stirred for 1 h at -78 °C.
The reaction mixture was quenched with a solution of ammonium
chloride and extracted with diethyl ether several times. The organic
layer was washed with H2O, dried over Na2SO4, and concentrated
in vacuo. The residue was purified by flash column chromatography
on silica gel with EtOAc:hexane (1:6) as eluent to afford 14 (392
tert-Butyl 4-{[(4-Methoxyphenoxy)methyl]-2,2-dimethyl-1,3-
dioxolan-4-yl}butanoate (21). A mixture of 20 (2.04 g, 6 mmol)
and p-toluenesulfonic acid (0.114 g, 6 mmol) in acetone (10 mL)
was stirred for 1 h at room temperature. The mixture was neutralized
with solid NaHCO3 and filtered, and the filtrate was concentrated
in vacuo. The residue was purified by flash column chromatography
on silica gel with EtOAc:hexanes (1:4) as eluent to give 21 as an
1
oil (1.96 g, 85%). H NMR (CDCl3) δ 6.83 (s, 4 H, Ar), 4.08 (d,
1 H, J ) 8.8 Hz, CH2OAr), 3.83 (m, 3 H, CH2OAr and >CCH2O),
3.77 (s, 3 H, OCH3), 2.25 (t, 2 H, J ) 6.6 Hz, CH2CO2), 1.6-1.8
(m, 4 H, >CCH2CH2), 1.44 (m, 15 H, CO2C(CH3)3 and >C(CH3)2).
6-Hydroxymethyl-3-[(Z/E)-3-isobutyl-5-methylhexylidene]-6-
[(4-methoxyphenoxy)methyl]tetrahydro-2-pyranone (23a,b). A
stirred solution of 21 (1.14 g, 3 mmol) in THF (6 mL) was cooled
to -78 °C and treated dropwise with lithium bis(trimethylsilyl)-
amide (1 M in THF, 4 mL, 4 mmol). After 30 min, 3-isobutyl-5-
methylhexanal (0.47 g, 3 mmol) in THF (3 mL) was added and
stirring was continued for 2 h at -78 °C. The reaction was quenched
by the slow addition of a saturated aqueous solution of ammonium
chloride and extracted with ether several times. The combined
organic layers were washed with H2O and brine, dried over MgSO4,
and concentrated in vacuo. The residue was purified by flash column
chromatography on silica gel with EtOAc:hexanes (1:10) as eluent
to give â-hydroxylactone as an oil (660 mg, 40%). A solution of
above compound (660 mg, 1.2 mmol) in CH2Cl2 (6 mL) was cooled
to 0 °C and treated with triethylamine (0.668 mL, 4.8 mmol) and
methanesulfonyl chloride (274 mg, 2.4 mmol). After stirring for 4
h at room temperature, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU,
730 mg, 4.8 mmol) was added and the resulting solution was
refluxed for 24 h. The reaction mixture was concentrated in vacuo,
and the residue was purified by flash column chromatography on
silica gel with EtOAc:hexanes (1:10) as eluent to give 22 as an
inseparable mixture of E and Z isomers as oils (290 mg, 45%). 22
(290 mg, 0.5 mmol) was dissolved in CH2Cl2 (5 mL), cooled to 0
°C, and treated with trifluoroacetic acid (0.5 mL). After being stirred
for 24 h at room temperature, the mixture was concentrated in vacuo
and the residue purified by flash column chromatography on silica
gel with EtOAc:hexanes (1:4) as eluent to give 23a (Z isomer, 18
mg, 8%) and 23b (E isomer, 75 mg, 36%) as oils, respectively.
23a: 1H NMR (CDCl3) δ 6.15 (m, 1 H, >CdCH), 4.08 (AB d,
1 H, J ) 9.2 Hz, CH2OAr), 3.96 (AB d, 1 H, J ) 9.3 Hz, CH2OAr),
3.77 (AB q, 2 H, J ) 7.0 Hz, CH2OH), 3.77 (s, 3 H, OCH3), 2.5-
2.7 (m, 2 H, H-4 and >CdCH-CH2), 1.9-2.2 (m, 2 H, H-5), 1.5-
1.75 (m, 3 H, 2 × CHMe2, CH(i-Bu)2), 1.10 (m, 4 H, 2 ×
CHCH2CHMe2), 0.86 (d, 12 H, 4 × CH3).
1
mg, 82%) as an oil. H NMR (CDCl3) δ 7.25-7.35 (m, 5 H, Ph),
6.81 (s, 4 H, Ar), 5.05-5.18 (m, 2 H, 2 × CHdC<), 4.56 (dd of
AB, 2 H, J ) 12 Hz, OCH2Bn), 4.03 (d, 1 H, J ) 9.5 Hz, OCH2Ar),
3.91 (d, 1 H, J ) 9.5 Hz, OCH2Ar), 3.76 (s, 3 H, OCH3), 3.59 (dd
of AB, 2 H, J ) 10 Hz, CH2OBn), 2.3-2.45 (m, 4 H, 2 ×
>CCH2CH)), 2.14 (d, 1 H, J ) 13.7 Hz, H-4a), 2.04 (d, 1 H, J )
13.7 Hz, H-4b), 1.66 (s, 6 H, dC(CH3)2), 1.59 (s, 6 H, dC(CH3)2).
5-(Hydroxymethyl)-5-(pivaloyloxymethyl)-3,3-bis(3-methyl-
2-butenyl)dihydro-2(3H)-furanone (15). By following the pro-
cedure described for the synthesis of 6-10, the title compound was
obtained as an oil in 65% yield starting from 14. 1H NMR (CDCl3)
δ 5.11 (bt, 2 H, 2 × CHdC<), 4.14 (dd of AB, 2 H, J ) 11.7 Hz,
CH2OCO), 3.57 (bs, 2 H, CH2OH), 2.3-2.45 (m, 4 H, 2 ×
>CCH2CH)), 2.17 (s, 1 H, OH), 2.08 (d, 1 H, J ) 13.9 Hz, H-4a),
1.85 (d, 1 H, J ) 13.9 Hz, H-4b), 1.75 (s, 6 H, dC(CH3)2), 1.64
(s, 6 H, dC(CH3)2), 1.22 (s, 9 H, C(CH3)3); IR (neat) 3479, 2971,
1770, 1737, 1636, 1451 cm-1; MS (EI) m/z 366 (M+). Anal.
(C21H34O5) C, H.
5-(Hydroxymethyl)-5-(pivaloyloxymethyl)-3,3-bis(3-methyl-
butyl)dihydro-2(3H)-furanone (16). By following the procedure
described for the synthesis of 6-10, the title compound was
obtained as an oil in 68% yield starting from 14. 1H NMR (CDCl3)
δ 4.29 (d, 1 H, J ) 11.9 Hz, CH2OCO), 4.12 (d, 1 H, J ) 11.9 Hz,
CH2OCO), 3.63 (dd of AB, 2 H, J ) 12 Hz, CH2OH), 2.45 (bs, 1
H, OH), 2.15 (d, 1 H, J ) 13.3 Hz, H-4a), 1.90 (d, 1 H, J ) 13.3
Hz, H-4b), 1.45-1.73 (m, 6 H), 1.25-1.35 (m, 2 H), 1.05-1.2
(m, 2 H), 1.23 (s, 9 H, C(CH3)3), 0.85-0.93 (m, 12 H, 4 × CH3);
IR (neat) 3502, 2956, 1769, 1736, 1538, 1463 cm-1; MS (EI) m/z
370 (M+). Anal. (C21H38O5) C, H.
4-Benzyloxy-3-hydroxy-3-[(4-methoxyphenoxy)methyl]-1-
butanal (19). A solution of 1821 (6.54 g, 20 mmol) in acetone
(20 mL) and H2O (20 mL) was treated with 4-methylmorpholine
N-oxide (2.34 g, 20 mmol), sodium periodate (4.28 g, 20 mmol),
and osmium tetraoxide (2.5 mL, 2.5 wt % in 2-methyl-2-propanol,
0.2 mmol) and stirred for 20 h at room temperature. The reaction
mixture was diluted with EtOAc and filtered. The filtrate was
sequentially washed with sodium thiosulfate solution, H2O, and
brine, dried over MgSO4, and concentrated in vacuo. The residue
was purified by flash column chromatography on silica gel with
EtOAc:hexanes (1:3) as eluent to afford 19 as an oil (3.94 g, 58%).
1H NMR (CDCl3) δ 9.90 (t, 1 H, J ) 2.4 Hz, CHO), 7.25-7.4 (m,
5 H, phenyl), 6.82 (s, 4 H, Ar), 4.56 (s, 2 H, OCH2Ph), 3.92 (s, 2
H, CH2OAr), 3.77 (s, 3 H, OCH3), 3.60 (AB q, 2 H, J ) 9.3 Hz,
CH2OBn), 3.12 (bs, 1 H, OH), 2.77 (d, 2 H, J ) 2.4 Hz, CH2CHO).
tert-Butyl 5,6-Dihydroxy-5-[(4-methoxyphenoxy)methyl]hex-
anoate (20). A mixture of 19 (1.725 g, 5.2 mmol) and (tert-
butoxycarbonylmethylene)triphenylphosphorane (3.915 g, 10.4
mmol) in toluene (10 mL) was refluxed for 2 h and concentrated
in vacuo. The residue was purified by flash column chromatography
on silica gel with EtOAc:hexanes (1:2) as eluent to afford
unsaturated ester as an oil (1.465 g, 73%). A suspension of above
ester (1.465 g, 3.8 mmol) and 10% palladium on carbon (0.73 g)
in EtOAc (8 mL) was hydrogenated under a balloon of hydrogen
for 2 h. The mixture was filtered, and the filtrate was concentrated
23b: 1H NMR (CDCl3) δ 7.15 (m, 1 H, >CdCH), 4.11 (AB d,
1 H, J ) 9.3 Hz, CH2OAr), 3.94 (AB d, 1 H, J ) 9.3 Hz, CH2OAr),
3.81 (s, 2 H, CH2OH), 3.77 (s, 3 H, OCH3), 2.58 (m, 2 H, H-4),
1.95-2.2 (m, 4 H, H-5 and >CdCH-CH2), 1.5-1.75 (m, 3 H, 2
× CHMe2, CH(i-Bu)2), 1.10 (m, 4 H, 2 × CHCH2CHMe2), 0.86
(d, 12 H, 4 × CH3).
6-Hydroxymethyl-3-[(Z/E)-3-isobutyl-5-methylhexylidene]-6-
pivaloyloxymethyl-tetrahydro-2-pyranone (24a,b). A cooled
solution of 23a (or 23b) (30 mg, 0.07 mmol) in CH2Cl2 (2 mL) at
0 °C was treated with triethylamine (28 mg, 0.28 mmol), pivaloyl
chloride (17 mg, 0.14 mmol), and a catalytic amount of 4-di-
methylaminepyridine and stirred for 3 h at room temperature. The
mixture was concentrated in vacuo, and the residue was purified
by flash column chromatography on silica gel with EtOAc:hexanes
(1:10) as eluent to give the acylated product (32 mg, 90%).
Acylated Product. A solution of the acylated product (32 mg,
0.064 mmol) in CH3CN-H2O (4:1, 2 mL) was cooled to 0 °C and
treated with ammonium cerium(IV) nitrate (70 mg, 0.128 mmol).
After being stirred for 30 min at 0 °C, the mixture was diluted

Branched Diacylglycerol-Lactones
Journal of Medicinal Chemistry, 2006, Vol. 49, No. 6 2035
with CH2Cl2. The organic layer was washed with aqueous NaHCO3
solution and brine, dried over MgSO4, and concentrated in vacuo.
The residue was purified by flash column chromatography on silica
gel with EtOAc:hexanes (1:2) as eluent to give 24a (or 24b) as an
oil (20 mg, 76%).
monoclonal antibody (6E10-Chemicon, Temecula, CA) After further
washes, membranes were incubated for 1 h with horseradish
peroxidase-linked anti-mouse IgG antibody, and the immunoreactive
bands were detected by enhanced chemiluminescence (ECL)
(Amersham Pharmacia, Piscataway, NJ).
24a (Z isomer): 1H NMR (CDCl3) δ 6.15 (m, 1 H, >CdCH),
4.30 (AB d, 1 H, J ) 11.7 Hz, CH2OCO), 4.13 (AB d, 1 H, J )
11.7 Hz, CH2OCO), 3.64 (AB q, 2 H, J ) 11.9 Hz, CH2OH), 2.5-
2.7 (m, 4 H, H-4 and >CdCH-CH2), 1.75-2.05 (m, 2 H, H-5),
1.5-1.7 (m, 3 H, 2 × CHMe2, CH(i-Bu)2), 1.22 (s, 9 H, C(CH3)3),
1.10 (m, 4 H, 2 × CHCH2CHMe2), 0.86 (d, 12 H, 4 × CH3); IR
(neat) 3443, 1730, 1715, 1634 cm-1; MS (FAB) m/z 397 (MH+).
Anal. (C23H40O5) C, H.
Densitometric analysis of the western blot data was performed
using a Bio-Imaging analyzer (ChemiDoc XRS, Bio-Rad, Hercules,
CA & Image Gauge, Fuji, Tokyo).
Acknowledgment. This work was supported by a Korea
Research Foundation Grant (KRF-2003-015-E00229) and a
Korea Health 21 R&D Grant (02-PJ2-PG6-DC04-0001) from
the Ministry of Health and Welfare and by the Intramural
Research Program of the NIH, National Cancer Institute, Center
for Cancer Research. We thank Christina Torres, Kathy Hughes,
and Justin Kung for technical assistance.
24b (E isomer): 1H NMR (CDCl3) δ 7.14 (m, 1 H, >CdCH),
4.28 (AB d, 1 H, J ) 11.7 Hz, CH2OCO), 4.15 (AB d, 1 H, J )
11.7 Hz, CH2OCO), 3.63 (AB q, 2 H, J ) 12.2 Hz, CH2OH), 2.55
(m, 2 H, H-4), 1.8-2.15 (m, 4 H, H-5 and >CdCH-CH2), 1.5-
1.7 (m, 3 H, 2 × CHMe2, CH(i-Bu)2), 1.22 (s, 9 H, C(CH3)3), 1.10
(m, 4 H, 2 × CHCH2CHMe2), 0.86 (d, 12 H, 4 × CH3); IR (neat)
3442, 1732, 1718, 1633 cm-1; MS (FAB) m/z 397 (MH+). Anal.
(C23H40O5) C, H.
Supporting Information Available: Elemental analysis data
for final compounds. This material is available free of charge via
the Internet at http://pubs.acs.org.
6-Hydroxymethyl-3-[(E)-3-isobutyl-5-methylhexylidene]-6-
hexanoyloxymethyl-tetrahydro-2-pyranone (25b). The compound
was prepared by following the procedure described for the synthesis
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1
of 24 using hexanoyl chloride from 23b in 82% yield. H NMR
(CDCl3) δ 7.14 (m, 1 H, >CdCH), 4.31 (AB d, 1 H, J ) 11.7 Hz,
CH2OCO), 4.16 (AB d, 1 H, J ) 11.7 Hz, CH2OCO), 3.66 (AB q,
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1
of 24 using octanoyl chloride from 23b in 80% yield. H NMR
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15 H, 5 × CH3); IR (neat) 3442, 1732, 1718, 1633 cm-1; MS (FAB)
m/z 439 (MH+). Anal. (C26H46O5) C, H.
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