Protein kinase C ligands based on tetrahydrofuran templates containing a new set of phorbol ester pharmacophores

Article abstract of DOI:10.1021/jm980713g

A series of substituted tetrahydrofurans with an embedded glycerol backbone carrying additional tetrahydrofuranylideneacetate or tetrahydrofuranylacetate motifs were grouped into four distinct templates (I- IV) according to stereochemistry. The compounds were designed to mimic three essential pharmacophores (C₃-C=O, C₂₀-OH and C₁₃-C=O) of the phorbol esters according to a new, revised model. The tetrahydrofuran ring was constructed from glycidyl 4-methoxyphenyl ether, and the structures of the isomeric templates were assigned by NMR spectroscopy, including NOE. The binding affinity for protein kinase C (PKC) was assessed in terms of the ability of the ligands to displace bound [³H-20]phorbol 12,13-dibutyrate (PDBU) from a recombinant α isozyme of PKC. Geometric Z- and E-isomers (1 and 3, respectively) containing a tetrahydrofuranylideneacetate motif were the most potent ligands with identical K(i) values of 0.35 μM. Molecular modeling studies of the four templates showed that the rms values when fitted to a prototypical phorbol 12,13-diacetate ester correlated inversely with affinities in the following order: I ? II > III > IV. These compounds represent the first generation of rigid glycerol templates seeking to mimic the binding of the C₁₃-C=O of the phorbol esters. The binding affinities of the most potent compounds are in the same range of the diacylglycerols (DAGs) despite the lack of a phorbol ester C₉-OH pharmacophore surrogate. This finding confirms that mimicking the binding of the C₁₃-C=O pharmacophore of phorbol is a useful strategy. However, since the C₉-OH and C₁₃-C=O in the phorbol esters appear to form an intramolecular hydrogen bond that functions as a combined pharmacophore, it is possible the lack of this combined motif in the target templates restricts the compounds from reaching higher binding affinities.

Full text of DOI:10.1021/jm980713g

J . Med. Chem. 1999, 42, 4129-4139
4129
P r otein Kin a se C Liga n d s Ba sed on Tetr a h yd r ofu r a n Tem p la tes Con ta in in g a
New Set of P h or bol Ester P h a r m a cop h or es
J eewoo Lee,*,† J i-Hye Kang,† Sang-Yoon Lee,† Kee-Chung Han,† Christina M. Torres,‡ Dipak K. Bhattacharyya,‡
Peter M. Blumberg,‡ and Victor E. Marquez§
Laboratory of Medicinal Chemistry, College of Pharmacy, Seoul National University, Shinlim-Dong, Kwanak-Ku,
Seoul 151-742, Korea, and Laboratories of Cellular Carcinogenesis and Tumor Promotion and of Medicinal Chemistry,
Division of Basic Sciences, National Cancer Institutes, National Institutes of Health, Bethesda, Maryland 20892
Received December 18, 1998
A series of substituted tetrahydrofurans with an embedded glycerol backbone carrying
additional tetrahydrofuranylideneacetate or tetrahydrofuranylacetate motifs were grouped into
four distinct templates (I-IV) according to stereochemistry. The compounds were designed to
mimic three essential pharmacophores (C3-CdO, C20-OH and C13-CdO) of the phorbol esters
according to a new, revised model. The tetrahydrofuran ring was constructed from glycidyl
4-methoxyphenyl ether, and the structures of the isomeric templates were assigned by NMR
spectroscopy, including NOE. The binding affinity for protein kinase C (PKC) was assessed in
terms of the ability of the ligands to displace bound [3H-20]phorbol 12,13-dibutyrate (PDBU)
from a recombinant R isozyme of PKC. Geometric Z- and E-isomers (1 and 3, respectively)
containing a tetrahydrofuranylideneacetate motif were the most potent ligands with identical
Ki values of 0.35 µM. Molecular modeling studies of the four templates showed that the rms
values when fitted to a prototypical phorbol 12,13-diacetate ester correlated inversely with
affinities in the following order: I ≈ II > III > IV. These compounds represent the first
generation of rigid glycerol templates seeking to mimic the binding of the C13-CdO of the
phorbol esters. The binding affinities of the most potent compounds are in the same range of
the diacylglycerols (DAGs) despite the lack of a phorbol ester C9-OH pharmacophore surrogate.
This finding confirms that mimicking the binding of the C13-CdO pharmacophore of phorbol
is a useful strategy. However, since the C9-OH and C13-CdO in the phorbol esters appear to
form an intramolecular hydrogen bond that functions as a combined pharmacophore, it is
possible the lack of this combined motif in the target templates restricts the compounds from
reaching higher binding affinities.
Ch a r t 1
In tr od u ction
Protein kinase C (PKC) represents a family of phos-
pholipid-dependent, serine/threonine-specific protein ki-
nases comprising 12 isozymes. These isozymes are
believed to play important roles in cellular signal
transduction pathways involved in cellular processes
such as cell differentiation, proliferation, modulation of
gene expression, and multiple-drug resistance (MDR).1-5
Most PKC isozymes are activated endogenously by
diacylglycerol (DAG) released from the receptor-acti-
vated hydrolysis of phosphatidylinositol 4,5-bisphos-
phate (PIP2) or from phosphatidylcholine (PC) hydrol-
ysis.6,7 PKC is also activated directly by several natural
product tumor-promoting agents such as the phorbol
esters.8 The binding site of these ligands on PKC has
been identified as a tandem repeat of two cysteine-rich
zinc-finger motifs, so-called C1a and C1b, present in the
regulatory C1 domain of the enzyme.9 In general, the
phorbol esters display binding affinities that are several
orders of magnitude greater than those of the DAGs.
This exceptional affinity can be explained in part by the
relative conformational rigidity of the phorbol esters
which confers on the molecule an entropic advantage
during binding.
Over the past few years, we have synthesized a series
of conformationally constrained DAG analogues embed-
ded in a variety of lactone templates designed to reduce
part of the entropic penalty associated with the binding
of the flexible glycerol backbone of DAG.10-32 We have
reported the benefits of this strategy which have
culminated with a series of “ultrapotent” DAG ana-
logues built on a 5-[(acyloxy)methyl]-5-(hydroxymethyl)-
tetrahydro-2-furanone template. Depending on the type
of hydrophobic substitution, some of the compounds
built with this template displayed ca. 100-fold greater
affinity for PKC-R than the equivalent DAGs (Chart
1).24-26 A comprehensive molecular modeling study of
this template in comparison to the phorbol esters
indicated that the two CdO groups (acyloxy and lactone)
* To whom correspondence should be addressed. E-mail:
jeewoo@snu.ac.kr.
† Seoul National University.
‡ Laboratory of Cellular Carcinogenesis and Tumor Promotion, NCI.
§ Laboratory of Medicinal Chemistry, NCI.
10.1021/jm980713g CCC: $18.00 © 1999 American Chemical Society
Published on Web 09/16/1999

4130 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20
Lee et al.
Sch em e 1a
a
Reagents and conditions: (a) BnOH, NaH, DMF, 80 °C; (b) PCC, 4 Å molecular sieve, CH2Cl2; (c) CH2dCHCH2MgCl, THF; (d) OsO4,
4-NMO, acetone-H2O, rt; (e) TsCl, pyridine; (f) PCC, molecular sieve, CH2Cl2; (g) (MeO)2P(dO)CH2CO2Me, t-BuOK, THF, reflux.
Ch a r t 2
and the primary OH overlapped almost perfectly with
the C3-CdO, C20-OH, and C9-OH of the diterpene.25
This result supported a previous pharmacophore model
in which the combined interaction of these three groups
was considered essential for the strong binding of
phorbol esters.33-35 Other pharmacophore models em-
phasizing the importance of the adjacent C4-OH group
have been proposed.36-38
Recently, a new pharmacophore model was proposed
by Hecker et al. who provided evidence in support of
the importance of the C13-CdO of the phorbol esters
for irritant and tumor-promoting potency in mouse
skin.39 Similarly, the group of Shibasaki demonstrated
indirectly the importance of the C13-CdO with phorbol
ester analogues lacking this functionality.40 In a more
direct fashion, photo-cross-linking experiments of a
phorbol ester with a diazoacetyl group at C13 suggested
that this group was indeed located in close proximity
to the protein in the ligand-enzyme-phospholipid
complex.40 The Blumberg group also reported that the
removal of the acyl group at C13 caused a significant
drop in binding affinity when comparing phorbol 12- and
13-monoesters.41
In our continuing effort to design conformationally
constrained DAG analogues as potent PKC ligands able
to compete efficiently with phorbol esters, we set out to
investigate simple substituted tetrahydrofuran tem-
plates with an embedded glycerol backbone carrying an
additional surrogate pharmacophore for the C13-CdO
of the phorbol esters. The four prototypes (templates
I-IV) proposed were designed to retain the putative
recognition domain of the phorbol ester: namely, the
C3-CdO and C20-OH (Chart 2). Since from our previ-
ous work the CdO of the (acyloxy)methyl group and
primary OH group of the potent lactone template
overlaid nicely with the C3-CdO and C20-OH groups,
respectively, these groups were retained. In the new
templates I-IV the lactone CdO was removed and Cd
hydrophobic interactions at different ends of the tem-
plate. The syntheses, binding affinities, and limited
structure-activity relationship (SAR) analysis of the
newly designed templates are reported herein.
Ch em istr y
O groups at different positions were investigated as
surrogate pharmacophores of the C13-CdO of the
phorbol esters. The position of the C13 ester-mimicking
carbonyl in templates I-IV was derived from the spatial
orientation of the C13-CdO of phorbol 12,13-diacetate
described in Hecker’s molecular model (Chart 2). As in
other conformationally constrained glycerol analogues,
short and long alkyl chains were combined to optimize
The key intermediate for the synthesis of targets 1-4
(Table 1) was compound 12. This was prepared as shown
in Scheme 1 from glycidyl 4-methoxyphenyl ether (9)
in six steps that involved a 1,5-intramolecular cycliza-
tion and oxidation as penultimate and ultimate steps.
Reaction of 12 with trimethyl phosphonoacetate pro-
vided both E- and Z-isomers which were separated with
difficulty by column chromatography due to their close

PKC Ligands Based on Tetrahydrofuran Templates
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20 4131
Sch em e 2a
F igu r e 1. NOEs of compounds 29, 32, and 33.
intractable separation of isomers at the final stage, the
target compounds 1 and 3 were synthesized from pure
samples of 13 and 14 after deprotection of the 4-meth-
oxyphenyl group, acylation, and debenzylation (Scheme
2). For targets 2 and 4, a mixture of 13 and 14 was used
directly because the final compounds were readily
separated by column chromatography (Scheme 3). As
before, the structures of 2 and 4 were also assigned
based on relative chemical shift differences between H-2
and H-5.
a
Reagents and conditions: (a) CAN, CH3CN-H2O; (b) C13H27
-
COCl, NEt3, DMAP, CH2Cl2; (c) BCl3, CH2Cl2, -78 °C.
Sch em e 3a
For the synthesis of targets 5-8 (Table 1), the key
intermediate 25 was prepared by an intramolecular
Michael-type reaction from R,â-unsaturated ester 24
which was obtained from ketone 10 in three steps
(Scheme 4). Even though at the stage of 25 resolution
of the two isomers was impossible, separation of isomers
was possible by column chromatography at the stage of
26 and 27 after removal of the p-methoxyphenyl group.
Acylation followed by debenzylation of each isomer
produced the final target compounds 5 and 7. The
structures of the final compounds were assigned based
on the results from NOE experiments performed at the
stage of compound 29 (Figure 1). Compound 29 was
ideal because it showed distinct chemical shifts for H-3
of the tetrahydrofuran ring and the 1′- and 1′′-methyl-
a
Reagents and conditions: (a) LiOH, THF, H2O; (b) C18H35OH,
DCC, DMAP, CH2Cl2; (c) CAN, CH3CN-H2O; (d) Ac2O, NEt3,
DMAP, CH2Cl2; (e) BCl3, CH2Cl2, -78 °C.
Rf values. The geometric assignment of E/ Z-isomers
was based on the relative differences in chemical shift
in H-2 and H-4 of the tetrahydrofuran ring. In each case,
the chemical shift of the ring methylene closest to the
carbonyl appeared downfield [13 (Z-isomer) δH-2 ) 4.95,
δH-5 ) 2.86; 14 (E-isomer) δH-2 ) 4.65, δH-5 ) 3.17].
Since initial syntheses of 1 and 3 directly from a
mixture of 13 and 14 were unsuccessful due to the
Sch em e 4a
a
Reagents and conditions: (a) CH2dCHCH2CH2Br, Mg, dibromoethane, THF; (b) OsO4, 4-NMO, NaIO4, acetone-H2O; (c) Ph3PdCHCO2CH3,
toluene, reflux; (d) Bu4NF, THF; (e) CAN, CH3CN-H2O; (f) C13H27COCl, NEt3, DMAP, CH2Cl2; (g) H2, Pd-C, EtOAc.

4132 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20
Lee et al.
Sch em e 5a
a
Reagents and conditions: (a) LiOH, THF, H2O; (b) C14H29OH, DCC, DMAP, CH2Cl2; (c) CAN, CH3CN-H2O; (d) C5H11COCl, NEt3,
DMAP, CH2Cl2; (e) H2, Pd-C, EtOAc.
ene groups located above and below the plane of the five-
membered ring.
compounds that one can generate. Hence, for target
compounds 1-4, alkyl chains of 13 and18 carbons were
studied (Table 1). In the case of target compounds 5-8,
however, a smaller 5-carbon acyl chain was required at
one end of the molecule to avoid the racemization that
is normally observed when acetyl groups are used. Such
a change demanded the use of a reduced size alkyl chain
at the other end of the molecule to approximate closely
the lipophilicity provided by an 18-carbon chain. Fol-
lowing our standard approach, the larger lipophilic
groups were switched from one carbonyl group to the
other.
For the synthesis of 6 and 8, the methyl ester of 25
was exchanged by a tetradecyl group in two steps
(Scheme 5). Following deprotection of the 4-methoxy-
phenyl group of 31, the two isomers 32 and 33 were
separated and their structures assigned by NOE (Figure
1). Acylation of each isomer was performed with hex-
anoyl chloride instead of acetyl chloride to avoid possible
acyl migration which would have caused epimerization
at C-5. Removal of the benzyl group afforded the desired
final compounds 6 and 8 without signs of acyl migration.
Compounds 1 and 3 had basically the same binding
affinity with a Ki ) 0.35 µM. This binding affinity was
superior to that shown by the corresponding DAG
analogue, rac-glycerol 1-myristate 2-acetate (GMA) with
a reported Ki of 0.7 µM.42 On the other hand, in
compounds 2 and 4, where the relative disposition of
the hydrophobic chain was inverted relative to 1 and 3,
the binding affinities were only comparable to that of
GMA. Compounds 5-8 were significantly less potent
than GMA but showed modest discrimination between
cis and trans isomers.
From the standpoint of ligands having equivalent
lipophilic parameters to compare the effects of the
different location of the ester side chains, compounds
1, 3, 5, and 7 were selected for a structural analysis.
These compounds differed in terms of the spatial
disposition of the CdO group that was designed to
mimic the C13-CdO ester of phorbol. Their relative
binding affinities followed the order: 1 (template I) ≈
3 (template II) > 5 (template III) > 7 (template IV).
Correlating their biological potency with the spatial
orientations of this critical ester group was examined
by molecular modeling. Compounds 1, 3, 5, and 7 were
selected as representatives of each of the different
templates. Molecular modeling was performed using the
program Sybyl 6.4 from Tripos. The lowest energy
conformers obtained after a full conformational search
are shown in Figures 2 and 3. The internal distances
between the carbonyls and hydroxyl pharmacophores
are also depicted as forming a triangle. The three
pharmacophores in each template were superimposed
onto the C3-CdO, C20-OH, and C13-CdO of phorbol
diacetate whose coordinates were derived from Hecker’s
study.39 The resulting rms values relative to phorbol
with ligands 1 and 3 (Figure 2) were very low: 0.002
for compound 1 and 0.009 for compound 3. These
Resu lts a n d Discu ssion
The binding affinities of the target compounds 1-8
(Table 1) were assessed in terms of their ability to
displace bound [3H-20]phorbol 12,13-dibutyrate (PDBU)
from a single recombinant PKC-R.10 The ID50 values
(concentration yielding 50% inhibition of [3H]PDBU
binding) were determined by fit of the data points to
the equation for noncooperative competition. The Ki
values for inhibition of binding were calculated from the
ID50 values. With this preliminary assay, one can
compare the efficiency of the new templates (I-IV)
relative to 14 previously synthesized templates10-32
before pursuing further biological evaluation on the
most promising compounds. Therefore, the results of
this work (Table 1) must be viewed in the context of a
larger universe that includes all the previous templates
investigated, but with particular reference to the most
potent lactone template shown in Chart 1. Relative to
this potent template, two of the critical recognition
elements of the template were left intact and only the
position of the third pharmacophore was changed to a
limited range of distances from the ring to best match
the C13 carbonyl of phorbol (Chart 2). To complement
the strategy alkyl chains of suitable length were ap-
pended at opposite sites of the templates in order to
steer these molecules into the lipid milieu in two
possible orientations. This strategy has proven success-
ful with previous templates, and the present work
represents an extension of this approach. From our
previous studies, we have also learned that these
molecules required a critical lipophilic character to be
active and to partition appropriately into the mem-
brane.18 We have determined that for this purpose the
required alkyl chains have to be between 13 and 18
carbons long,18 which puts limits on the number of

PKC Ligands Based on Tetrahydrofuran Templates
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20 4133
Ta ble 1. Apparent Ki Values for Ligands 1-8 as Inhibitors of PDBU Binding to PKC-R
F igu r e 2. Lowest energy conformers of 1 (template I) and 3
(template II) and their rms values after fitting to phorbol
12,13-diacetate.
F igu r e 3. Lowest energy conformers of 5 (template III) and
7 (template IV) and their rms values after fitting to phorbol
12,13-diacetate.
compounds showed a very similar triangular disposition
of pharmacophores in both preferred geometrical ori-
entations of the R,â-unsaturated esters which would
explain why they have similar binding affinities. The
higher rms values for 5 and 7 (0.603 and 1.34, respec-
tively) are in keeping with their poorer binding affini-
ties.
A representative fitting between Z-isomer 1 and
phorbol diacetate is shown in Figure 4. Although this
figure shows a perfect superposition of the C13-CdO
and CdO ester mimic in 1, the rest of the ester moieties
do not match well and are disposed like mirror images

4134 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20
Lee et al.
intramolecular hydrogen bonding. Probably the pres-
ence of both groups may be necessary for high binding
affinity. However, the observed differences in binding
affinities of our four prototype templates suggest that
indeed the C13-CdO of phorbol is very likely involved
in interacting with PKC at the same DAG binding site.
Although the X-ray structure of the phorbol ester 13-
acetate/C1b complex of PKC-δ showed that the C13-
CdO of phorbol was outside the binding pocket and
formed no contact with the protein,37b the C13-CdO has
been shown to be crucial for bioactivity in recent SAR
studies by Hecker and Shibasaki.39,40 Additional mo-
lecular modeling studies and site-directed mutagenesis
experiments also support the involvement of the C13-
CdO group in PKC binding.43
F igu r e 4. Superposition of 1 on phorbol 12,13-diacetate.
It is possible that the intramolecularly hydrogen-
bonded C9-OH/C13-CdO motif in phorbol 13-O-acetates
the missing pharmacophore!smay be interacting at the
membrane interface, and since the crystal structure of
the phorbol 13-O-acetate/C1b complex does not contain
lipid, this pharmacophore appears uninvolved. We
might conclude from this work that future templates
that contain all four pharmacophores (C3-CdO, C20-
OH, C9-OH, and C13-CdO) would probably produce
better ligands and help resolve the issue of the missing
pharmacophore.
of each other. This may explain, in part, the difference
in biological potency between the phorbol esters and 1.
The results obtained from molecular modeling agree
with the biological data and confirmed the already
established order of potency for templates I-IV (I ≈ II
> III > IV). Equivalent template ligands to 1, 3, 5, and
7 (2, 4, 6, and 8) having long alkyl chains at alternative
positions showed similar or slightly less binding affini-
ties than the parent structures. The term relative
potency among templates has to be taken with a word
of caution. As already mentioned, most of these com-
pounds have to be designed with a required lipophilic/
hydrophilic balance, and hence they share a common
affinity to localize into lipids. From our experience with
other templates, we have learned that the majority of
these templates generate rather modest ligands with
similar binding affinities despite their structural diver-
sity. Only with the best templates (Chart 1)25,26 do the
Ki values move to submicromolar and low-nanomolar
values. The reason for such a phenomenon is that with
these amphiphilic molecules there is always a nonspe-
cific binding effect resulting from their presence in the
lipid environment which produces a sort of “background”
effect regardless of the structure of the template. It is
only when the hydrophilic groups on the lactone tem-
plate are additionally capable of fitting well into the
binding site of PKC that a significant increase in
binding affinity is observed. We can conclude that in
the present study such a significant increase was not
realized. Certainly in relation to our best reference
template (Chart 1) binding affinity was diminished with
the changes implemented. However, based on past
record, templates I and II in the present paper fall into
the category of better templates because of their sub-
micromolar Ki’s, whereas templates III and IV are in
the category of poor templates. Indeed, ligands 1 and 3
showed better binding affinity than the structurally
equivalent DAG analogue, although they are still about
10 times less potent than the equivalent lactone tem-
plate (Chart 1, Ki ) 35-77 nM) whose three hydrogen-
bond-forming pharmacophores overlay the three clas-
sical phorbol pharmacophores shown in Chart 1 (C3-
CdO, C20-OH, and C9-OH).24 This may lead to the
conclusion that in terms of binding affinity to PKC, the
C13-CdO group is less critical than the C9-OH group
in phorbol ester binding. However, it may be difficult
to separate the individual function of these two groups
and evaluate their relative importance to binding, since
in phorbols these groups are aligned very closely by
Exp er im en ta l Section
Gen er a l Exp er im en ta l. All chemical reagents were com-
mercially 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 and carbon NMR spectra
were recorded on a J EOL J NM-LA 300 at 300 MHz and J EOL
J NM-GCX 400 at 100 MHz, respectively. Chemical shifts are
reported in ppm units with Me4Si as 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 auto-
matic elemental analyzer, CE Instruments.
An a lysis of In h ibition of [3H-20]P DBU Bin d in g by
Non r a d ioa ctive Liga n d s. Enzyme-ligand interactions to-
ward the single PKC isozyme (PKC-R) were analyzed by
competition of [3H-20]PDBU binding essentially as described
in our previous work.10 The ID50 values were determined from
the competition curves, and the corresponding Ki values for
the ligands were calculated from the ID50 values. Values
represent the mean ( standard error (three experiments).
Molecu la r Mod elin g. The structures of the four templates
were built and optimized using SYBYL 6.4, Tripos. All calcula-
tions including the conformational search were performed on
a Silicon Graphics O2 R10000 workstation. The structure of
phorbol 12,13-diacetate was constructed based on a previous
reference.39
1-(Ben zyloxy)-3-(4-m eth oxyp h en oxy)a ceton e (10). A
solution of benzyl alcohol (8.6 mL, 83.2 mmol) in DMF (40 mL)
was treated portionwise with NaH (60%, 3.33 g, 83.2 mmol)
while maintained at 0 °C. After 30 min of stirring at room
temperature, the mixture was treated with 9 (10 g, 55.5 mmol)
portionwise. The reaction mixture was heated at 80 °C for 4 h
and cooled to room temperature. The mixture was diluted with
H2O and extracted with EtOAc several times. The combined
organic layer was washed with H2O, dried over MgSO4, and
concentrated in vacuo. The residue was purified by flash
column chromatography on silica gel with EtOAc/hexane (1:
2) as eluant to give the correponding alcohol as an oil (14.46
g, 90%): 1H NMR (CDCl3) δ 7.27-7.37 (m, 5 H, phenyl), 6.80-
6.86 (m, 4 H, 4-methoxyphenyl), 4.58 (s, 2 H, PhCH2O), 4.17
(m, 1 H, CHOH), 4.00 (dd of AB, 1 H, CH2OAr, J ) 4.8 and 10
Hz), 3.96 (dd of AB, 1 H, CH2OAr, J ) 6.0 and 10 Hz), 3.76 (s,

PKC Ligands Based on Tetrahydrofuran Templates
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20 4135
3 H, OCH3), 3.67 (dd of AB, 1 H, BnOCH2, J ) 4.4 and 10 Hz),
3.61 (dd of AB, 1 H, BnOCH2, J ) 6.0 and 10 Hz), 2.60 (bs, 1
H, OH).
in THF, 5.8 mmol) was added to a stirred solution of trimethyl
phosphonoacetate (1.6 g, 8.7 mmol) in THF (8 mL). After 1 h
of stirring at room temperature, the mixture was cooled to 0
°C and a solution of 12 (1.0 g, 2.9 mmol) in THF (4 mL) was
added. The resulting solution was refluxed for 10 h, cooled to
room temperature, and concentratred in vacuo. The residue
was purified by flash chromatography on silica gel with EtOAc/
hexane (1:4) as eluant to afford 13 (0.404 g, 35%) and 14 (0.452
g, 39%) as colorless oils, respectively.
13: Z-isomer, Rf ) 0.50 (EtOAc:Hex ) 1:4); IR (neat) 1714
(CdO), 1508 (CdC) cm-1; 1H NMR (CDCl3) δ 7.25-7.35 (m, 5
H, phenyl), 6.82 (s, 4 H, 4-methoxyphenyl), 5.85 (m, 1 H, Cd
CHCO2Me), 4.95 (m, 2 H, H-2), 4.57 (dd of AB, 2 H, PhCH2O),
3.98 (dd of AB, 2 H, ArOCH2), 3.77 (s, 3 H, OCH3), 3.71 (s, 3
H, CO2CH3), 3.60 (dd of AB, 2 H, BnOCH2), 2.86 (m, 2 H, H-5);
13C NMR (CDCl3) δ 166.3, 162.7, 154.0, 152.8, 137.9, 128.3,
127.6, 127.5, 115.5, 114.5, 111.2, 83.2, 73.5, 71.8, 71.4, 70.0,
55.6, 51.2, 38.6. Anal. (C23H26O6) C, H.
14: E-isomer, Rf ) 0.43 (EtOAc:Hex ) 1:4); IR (neat) 1715
(CdO), 1509 (CdC) cm-1; 1H NMR (CDCl3) δ 7.25-7.35 (m, 5
H, phenyl), 6.82 (s, 4 H, 4-methoxyphenyl), 5.78 (m, 1 H, Cd
CHCO2Me), 4.65 (m, 2 H, H-2), 4.57 (dd of AB, 2 H, PhCH2O),
3.98 (dd of AB, 2 H, ArOCH2), 3.76 (s, 3 H, OCH3), 3.73 (s, 3
H, CO2CH3), 3.61 (dd of AB, 2 H, BnOCH2), 3.17 (m, 2 H, H-5);
13C NMR (CDCl3) δ 166.6, 161.8, 154.0, 152.9, 138.0, 128.3,
127.6, 127.5, 115.6, 114.5, 110.1, 85.5, 73.6, 72.5, 72.0, 70.64,
55.7, 51.2, 37.2. Anal. (C23H26O6) C, H.
(Z)-Meth yl 2-[4-(Hyd r oxym eth yl)-4-(tetr a d eca n oyloxy-
m eth yl)-3-oxola n ylid en e]a ceta te (1). A solution of 13 (0.232
g, 0.6 mmol) in CH3CN-H2O (4:1, 10 mL) was cooled to 0 °C
and treated with ammonium cerium(IV) nitrate (0.656 g, 1.2
mmol). After 30 min of stirring at 0 °C, the reaction mixture
was diluted with CH2Cl2. The organic layer was 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/hexane (1:2) as eluant to give 15 as an
oil (0.168 g, 93%): 1H NMR (CDCl3) δ 7.25-7.38 (m, 5 H,
phenyl), 5.84 (m, 1 H, CdCHCO2Me), 4.89 (m, 2 H, H-2), 4.54
(dd of AB, 2 H, PhCH2O), 3.70 (s, 3 H, CO2CH3), 3.63 (dd of
AB, 2 H, CH2OH), 3.48 (dd of AB, 2 H, CH2OBn), 2.78 (m, 2
H, H-5), 2.06 (t, 1 H, OH).
A solution of 15 (0.168 g, 0.48 mmol) in CH2Cl2 (10 mL) was
treated with triethylamine (0.268 mL, 1.92 mmol), a catalytic
amount of DMAP, and tetradecanoyl chloride (0.24 g, 0.96
mmol) at 0 °C. After 6 h of stirring at room temperature, the
reaction mixture was concentrated in vacuo. The residue was
purified by flash column chromatography on silica gel with
EtOAc/hexanes (1:4) as eluant to give 16 as an oil (0.196 g,
82%): 1H NMR (CDCl3) δ 7.25-7.38 (m, 5 H, phenyl), 5.83
(m, 1 H, CdCHCO2Me), 4.89 (m, 2 H, H-2), 4.54 (s, 2 H,
PhCH2O), 4.17 (dd of AB, 2 H, OCOCH2), 3.70 (s, 3 H, CO2-
CH3), 3.48 (dd of AB, 2 H, CH2OBn), 2.75 (m, 2 H, H-5), 2.27
(t, 2 H, CH2COO), 1.2-1.65 (m, 22 H, CH3(CH2)11CH2COO),
0.88 (distorted t, 3 H, CH3(CH2)12).
A solution of 16 (0.162 g, 0.32 mmol) in CH2Cl2 (8 mL) was
cooled to -78 °C and treated with boron trichloride in CH2Cl2
(1.28 mL, 1.0 M, 1.28 mmol). After 2 h of stirring at -78 °C,
the reaction mixture was quenched with saturated NaHCO3
solution and immediately partitioned between ether and
NaHCO3 solution. The organic layer was washed with H2O,
dried, and concentrated in vacuo. The residue was purified by
flash column chromatography on silica gel with EtOAc/hexanes
(1:2) as eluant to give 1 as an oil (0.112 g, 84%): IR (neat)
3443 (OH), 1730 and 1716 (CdO), 1671 (CdC) cm-1; 1H NMR
(CDCl3) δ 5.86 (m, 1 H, CdCHCO2Me), 4.91 (m, 2 H, H-2),
4.13 (s, 2 H, OCOCH2), 3.71 (s, 3 H, CO2CH3), 3.58 (dd of AB,
2 H, CH2OH), 2.75 (m, 2 H, H-5), 2.33 (t, 2 H, CH2COO), 2.16
(bs, 1 H, OH), 1.2-1.7 (m, 22 H, CH3(CH2)11CH2COO), 0.88
(distorted t, 3 H, CH3(CH2)12); 13C NMR (CDCl3) δ 173.8, 166.2,
161.8, 111.7, 83.2, 71.7, 64.8, 63.6. 51.3, 37.6, 34.1, 31.9. 29.7,
29.6, 29.5, 29.4, 29.3, 29.2, 29.1, 24.8, 22.7, 14.1; MS m/e 413
(M+ + 1). Anal. (C23H40O6) C, H.
A suspension of 4-Å molecular sieves (32.3 g) and pyridinium
chloroformate (32.3 g, 150 mmol) in CH2Cl2 (150 mL) was
slowly treated with alcohol (14.46 g, 50 mmol) in CH2Cl2 (50
mL) via syringe. After 24 h of stirring at room temperature,
the reaction mixture was quenched with ether and Celite and
stirred for 30 min. The mixture was filtered through a short
pad of silica gel, and the filtrate was concentrated. The residue
was purified by flash column chromatography on silica gel with
EtOAc/hexane (1:2) as eluant to give 10 as a white solid (13.26
g, 92%): mp 58.8 °C; IR (neat) 1753 (CdO) cm-1 1H NMR
;
(CDCl3) δ 7.30-7.40 (m, 5 H, phenyl), 6.83 (bs, 4 H, 4-meth-
oxyphenyl), 4.71 (s, 2 H, CH2OAr), 4.62 (s, 2 H, PhCH2O), 4.36
(s, 2 H, CH2OBn), 3.77 (s, 3 H, OCH3).
1-(Ben zyloxy)-2-[(4-m eth oxyph en oxy)m eth yl]-4-pen ten -
2-ol (11). Allylmagnesium chloride (2 M in THF, 30 mL, 60
mmol) was slowly added to a cooled solution of 10 (5.76 g, 20
mmol) in THF (20 mL) at 0 °C. The reaction mixture was
warmed to room temperature and stirred for 2 h. The mixture
was quenched with 1 N HCl and concentrated to a small
volume which was diluted with H2O and extracted with ether
several times. The combined organic layer was washed with
H2O, dried over MgSO4, and concentrated in vacuo. The
residue was purified by flash column chromatography on silica
gel with EtOAc/hexane (1:4) as eluant to give 11 as an oil (5.76
g, 88%): IR (neat) 3468 (OH), 1641 (CdC) cm-1
;
1H NMR
(CDCl3) δ 7.25-7.35 (m, 5 H, phenyl), 6.75-6.86 (m, 4 H,
4-methoxyphenyl), 5.89 (m, 1 H, CH)CH2), 5.10-5.20 (m, 2
H, CHdCH2), 4.55 (s, 2 H, PhCH2O), 3.87 (s, 2 H, CH2OAr),
3.76 (s, 3 H, OCH3), 3.57 (d, 1 H, BnOCH2, J ) 9.2 Hz), 3.48
(d, 1 H, BnOCH2, J ) 9.2 Hz), 2.60 (bs, 1 H, OH), 2.44 (d, 2 H,
CH2CHdCH2, J ) 7.3 Hz).
5-{[(4-Met h oxyp h en yl)m et h oxy]m et h yl}-5-[(p h en yl-
m eth oxy)m eth yl]oxola n -3-on e (12). A solution of 11 (3.28
g, 10 mmol) in acetone (10 mL) and H2O (10 mL) was treated
with 4-methylmorpholine N-oxide (2.35 g, 20 mmol) and
osmium tetraoxide (0.1 mL, 2.5 wt % in 2-methyl-2-propanol,
0.05 mmol) and stirred for 2 h at room temperature. The
reaction mixture was quenched with sodium thiosulfate solu-
tion and concentrated to a small volume, which was diluted
with H2O and extracted with EtOAc several times. The
combined organic layer was washed with brine, dried over
MgSO4, and concentrated in vacuo. The residue was purified
by flash column chromatography on silica gel with EtOAc/
hexane (1:1) as eluant to give the corresponding triol as an oil
(3.44 g). The triol was dissolved in pyridine (15 mL) and
treated with p-toluenesulfonyl chloride (2.67 g, 14 mmol) at 0
°C. After 2 h of stirring at room temperature, the reaction
mixture was quenched with H2O and extracted with CH2Cl2
several times. The combined organic layer was washed with
brine, dried over MgSO4, and concentrated in vacuo. The
residue was purified by flash column chromatography on silica
gel with EtOAc/hexane (1:4) as eluant to give the alcohol as
an oil (2.74 g). The alcohol in CH2Cl2 (10 mL) was slowly added
via syringe to a suspension of 4-Å molecular sieves (5.17 g)
and pyridinium chloroformate (5.17 g, 24 mmol) in CH2Cl2 (20
mL). After 4 h of stirring at room temperature, the reaction
mixture was quenched with ether and Celite and stirred for
30 min. The mixture was filtered through a short pad of silica
gel, and the filtrate was concentrated in vacuo. The residue
was purified by flash column chromatography on silica gel with
EtOAc/hexane (1:5) as eluant to give 12 as an oil (1.71 g,
50%): IR (neat) 1763 (CdO) cm-1; 1H NMR (CDCl3) δ 7.2-7.3
(m, 5 H, phenyl), 6.75 (m, 4 H, 4-methoxyphenyl), 4.52 (s, 2
H, PhCH2O), 4.10 (s, 2 H, H-2), 3.98 (dd of AB, 2 H, ArOCH2),
3.69 (s, 3 H, OCH3), 3.65 (dd of AB, 2 H, BnOCH2), 2.57 (dd of
AB, 2 H, H-4); 13C NMR (CDCl3) δ 213.80, 154.20, 152.50,
137.56, 128.46, 127.82, 127.54, 115.46, 114.60, 83.30, 73.68,
73.28, 72.21, 71.98, 55.67, 41.50. Anal. (C20H22O5) C, H.
(Z)- a n d (E)-Meth yl 2-{4-{[(4-Meth oxyp h en yl)m eth oxy]-
m et h yl}-4-[(p h en ylm et h oxy)m et h yl]-3-oxola n ylid en e }-
a ceta te (13 a n d 14). Potassium tert-butoxide (5.8 mL, 1.0 M
(E)-Meth yl 2-[4-(Hyd r oxym eth yl)-4-(tetr a d eca n oyloxy-
m eth yl)-3-oxola n ylid en e]a ceta te (3). This compound was

4136 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20
Lee et al.
obtained from 14 by following the same procedure used for
the synthesis of 1.
4: E-isomer, Rf ) 0.26 (EtOAc:Hex ) 1:2); IR (neat) 3466
(OH), 1741 and 1722 (CdO), 1668 (CdC) cm-1 1H NMR
;
17: oil; 1H NMR (CDCl3) δ 7.25-7.38 (m, 5 H, phenyl), 5.76
(m, 1 H, CdCHCO2Me), 4.59 (m, 2 H, H-2), 4.55 (m, 2 H,
PhCH2O), 3.72 (s, 3 H, CO2CH3), 3.65 (ddd of AB, 2H, CH2-
OH), 3.51 (dd of AB, 2 H, CH2OBn), 3.06 (m, 2 H, H-5), 2.06
(t, 1 H, OH).
18: oil; 1H NMR (CDCl3) δ 7.25-7.38 (m, 5 H, phenyl), 5.77
(m, 1 H, CdCHCO2Me), 4.60 (m, 2 H, H-2), 4.56 (s, 2 H,
PhCH2O), 4.17 (dd of AB, 2 H, OCOCH2), 3.73 (s, 3 H, CO2-
CH3), 3.50 (dd of AB, 2 H, CH2OBn), 3.07 (m, 2 H, H-5), 2.28
(t, 2 H, CH2COO), 1.2-1.65 (m, 22 H, CH3(CH2)11CH2COO),
0.88 (distorted t, 3 H, CH3(CH2)12).
(CDCl3) δ 5.59 (m, 1 H, CdCHCO2R), 5.3-5.4 (m, 2 H, CHd
CH), 4.70 (m, 2 H, H-2), 4.18 (dd of AB, 2 H, CH2OAc), 4.09 (t,
2 H, CO2CH2), 3.62 (m, 2 H, CH2OH), 3.20 (m, 2 H, H-5), 2.08
(s, 3 H, OCOCH3), 1.95-2.1 (m, 4 H, CH2CHdCHCH2), 1.2-
1.7 (m, 24 H), 0.88 (distorted t, 3 H,CH3(CH2)7CHdCH); 13C
NMR (CDCl3) δ 171.02, 169.81, 158.12, 136.66, 124.57, 92.18,
65.56, 65.29, 64.89, 64.37, 38.55, 33.39, 31.88, 29.54, 29.48,
29.41, 29.36, 29.30, 29.24, 29.20, 29.18, 29.12, 28.54, 26.51,
25.87, 22.68, 20.82, 14.10; MS m/e 480 (M+). Anal. (C28H48O6)
C, H.
1-(Ben zyloxy)-2-[(4-m eth oxyp h en oxy)m eth yl]-5-h exen -
2-ol (23). A round-bottomed flask containing magnesium
turnings (0.74 g, 26 mmol) was dried under vacuum and
treated with 4-bromo-1-butene (2.0 mL, 19.5 mmol) in THF
(40 mL) dropwise at 0 °C. The reaction mixture was warmed
to room temperature and treated with 10 (1.76 g, 6.5 mmol)
in THF (20 mL) dropwise. After overnight stirring at room
temperature, the mixture was filtered through Celite and
concentrated in vacuo. The residue was purified by flash
column chromatography on silica gel with EtOAc/hexanes (1:
2) as eluant to give 23 as an oil (1.91 g, 82%): IR (neat) 3478
3: oil; IR (neat) 3461 (OH), 1730 and 1720 (CdO), 1671 (Cd
C) cm-1; 1H NMR (CDCl3) δ 5.80 (m, 1 H, CdCHCO2Me), 4.60
(m, 2 H, H-2), 4.15 (dd of AB, 2 H, OCOCH2), 3.73 (s, 3 H,
CO2CH3), 3.60 (ddd of AB, 2 H, CH2OH), 3.07 (m, 2 H, H-5),
2.33 (t, 2 H, CH2COO), 2.13 (t, 1 H, OH), 1.2-1.7 (m, 22 H,
CH3(CH2)11CH2COO), 0.88 (distorted t, 3 H, CH3(CH2)12); 13C
NMR (CDCl3) δ 173.8, 166.4, 160.7, 110.8, 85.5, 72.1, 64.8, 64.1.
51.3, 36.2, 34.2, 31.9. 29.7, 29.6, 29.5, 29.4, 29.3, 29.2, 29.1,
24.9, 22.7, 14.1; MS m/e 413 (M+ + 1). Anal. (C23H40O6) C, H.
1
(OH), 1640 (CdC) cm-1; H NMR (CDCl3) δ 7.24-7.35 (m, 5
(Z)- a n d (E)-Octa d ec-9-en yl 2-[4-(Acetoxym eth yl)-4-
(h yd r oxym eth yl)-3-oxola n ylid en e]a ceta te (2 a n d 4). A
solution of 13 and 14 (0.48 g, 1.2 mmol) mixture in THF (10
mL) and H2O (10 mL) was treated with LiOH (0.058 g, 2.4
mmol) and stirred for 12 h at room temperature. The reaction
mixture was concentrated to a small volume, acidified to pH
3 by adding 1 N HCl, and extracted with EtOAc several times.
The combined organic layer was washed with H2O, dried over
MgSO4, and concentrated in vacuo to give 19 as an oil (0.456
g, 1.2 mmol, 99%). Acid 19 in CH2Cl2 (20 mL) was treated with
oleyl alcohol (85%, 0.28 mL, 1.44 mmol), (dimethylamino)-
pyridine (0.015 g, 0.12 mmol), and DCC (1.0 M in CH2Cl2, 1.4
mL, 1.4 mmol) and stirred for 12 h at room temperature. The
reaction mixture was treated with several drops of acetic acid,
stirred for 2 h, and concentrated. The residue was purified by
flash column chromatography on silica gel with EtOAc/hexanes
(1:6) as eluant to give 20 as an oil (0.6 g, 0.94 mmol, 79%).
Ester 20 in CH3CN-H2O (4:1, 15 mL) was cooled to 0 °C and
treated with ammonium cerium(IV) nitrate (1.038 g, 1.88
mmol). After 1 h of stirring at 0 °C, the reaction mixture was
diluted with CH2Cl2. The organic layer was 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/hexane (2:3) as eluant to give 21 as an oil (0.3
g, 0.58 mmol, 62%). Alcohol 21 in CH2Cl2 (10 mL) was treated
with triethylamine (0.32 mL, 2.28 mmol) and acetic anhydride
(0.16 mL, 1.72 mmol) at 0 °C. After 8 h of stirring at room
temperature, the reaction mixture was concentrated in vacuo.
The residue was purified by flash column chromatography on
silica gel with EtOAc/hexanes (1:6) as eluant to give 22 (0.280
g, 0.5 mmol, 86%). Ester 22 in CH2Cl2 (10 mL) was cooled to
-78 °C and treated with boron trichloride in CH2Cl2 (1.0 M, 2
mL, 2 mmol). After 2 h of stirring at -78 °C, the reaction
mixture was quenched with saturated NaHCO3 solution and
immediately partitioned between ether and NaHCO3 solution.
The organic layer was washed with H2O, dried over MgSO4,
and concentrated in vacuo. The residue was purified by flash
column chromatography on silica gel with EtOAc/hexanes (1:
2) as eluant to give 2 (0.072 g, 30%) and 4 (0.132 g, 55%) as
oils, respectively.
H, phenyl), 6.83 (s, 4 H, 4-methoxyphenyl), 5.83 (m, 1 H,
CH)CH2), 5.03 (d, 1 H, J ) 17 Hz, CHdCH2), 4.94 (d, 1 H, J
) 10 Hz, CHdCH2), 4.54 (s, 2 H, PhCH2O), 3.87 (s, 2 H, CH2-
OAr), 3.77 (s, 3 H, OCH3), 3.52 (dd of AB, 2 H, BnOCH2), 2.60
(s, 1 H, OH), 2.14-2.22 (m, 2 H, CH2CHdCH2), 1.70-1.78 (m,
2 H, (HO)CCH2); 13C NMR (CDCl3) δ 154.02, 152.89, 138.80,
137.97, 128.40, 127.71, 127.62, 115.60, 114.62, 114.45, 73.42,
73.19, 72.62, 71.01, 55.74, 33.71, 27.12; MS m/e 342 (M+). Anal.
(C21H26O4) C, H.
Meth yl (E)-7-(Ben zyloxy)-6-h ydr oxy-6-[(4-m eth oxyph e-
n oxy)m eth yl]-2-h ep ten oa te (24). A solution of 23 (1.9 g, 5.32
mmol) in acetone (10 mL) and H2O (10 mL) was treated with
4-methylmorpholine N-oxide (1.25 g, 10.64 mmol), sodium
periodate (2.28 g, 10.64 mmol), and osmium tetraoxide (0.1
mL, 2.5 wt % in 2-methyl-2-propanol, 0.05 mmol). After 20 h
of stirring at room temperature, the reaction mixture was
diluted with EtOAc and filtered. The filtrate was washed
sequentially with a solution of sodium thiosulfate, H2O, and
brine, dried over MgSO4, and concentrated in vacuo. The
residue was purified by flash column chromatography on silica
gel with EtOAc/hexane (1:2) as eluant to give a lactol as an
oil (1.05 g, 3.2 mmol, 60%). The lactol in toluene (20 mL) was
treated with methyl (triphenylphosphoranylidene)acetate (1.6
g, 4.8 mmol), refluxed for 2 h, and concentrated in vacuo. The
residue was purified by flash column chromatography on silica
gel with EtOAc/hexanes (2:3) as eluant to give 24 as an oil
(1.059 g, 87%): IR (neat) 3478 (OH), 1722 (CdO), 1656 (CdC)
cm-1; 1H NMR (CDCl3) δ 7.24-7.35 (m, 5 H, phenyl), 6.99 (dt,
1 H, J ) 15.7 and 6.84 Hz, CHdCHCO2Me), 6.82 (s, 4 H,
4-methoxyphenyl), 5.83 (dt, 1 H, J ) 15.7 and 1.44 Hz, CHd
CHCO2Me), 4.54 (s, 2 H, PhCH2O), 3.86 (s, 2 H, CH2OAr), 3.77
(s, 3 H, OCH3), 3.71 (s, 3 H, CO2CH3), 3.51 (dd of AB, 2 H,
BnOCH2), 2.64 (s, 1 H, OH), 2.29-2.38 (m, 2 H, CH2CH2CHd
CH), 1.75-1.82 (m, 2 H, CH2CH2CHdCH); 13C NMR (CDCl3)
δ 167.05, 154.13, 152.72, 149.41, 137.79, 128.44, 127.80,
127.66, 120.90, 115.60, 114.66, 73.44, 72.92, 72.44, 70.88,
55.74, 51.40, 32.70, 25.71; MS m/e 400 (M+). Anal. (C23H28O6)
C, H.
r el-(1R,3S)- a n d r el-(1S,3S)-Meth yl 2-{3-{[(4-Meth oxy-
p h en yl)m eth oxy]m eth yl}-3-[(p h en ylm eth oxy)m eth yl]-2-
oxola n yl}a ceta te (26 a n d 27). A solution of 24 (1.0 g, 2.6
mmol) in THF (20 mL) was treated with tetrabutylammonium
fluoride (5.2 mL, 1.0 M in THF, 5.2 mmol) and stirred
overnight. The reaction mixture was concentrated in vacuo,
and the residue was purified by flash column chromatography
on silica gel with EtOAc/hexanes (1:3) as eluant to give 25 as
an oil (0.99 g, 2.57 mmol, 99%). A solution of 25 in CH3CN-
H2O (4:1, 15 mL) was cooled to 0 °C and treated with
ammonium cerium(IV) nitrate (2.74 g, 5 mmol). After 4 h of
stirring at 0 °C, the reaction mixture was diluted with CH2-
2: Z-isomer, Rf ) 0.32 (EtOAc:Hex ) 1:2); IR (neat) 3469
(OH), 1740 and 1715 (CdO), 1668 (CdC) cm-1 1H NMR
;
(CDCl3) δ 5.79 (m, 1 H, CdCHCO2R), 5.3-5.4 (m, 2 H, CHd
CH), 4.60 (m, 2 H, H-2), 4.07-4.21 (m, 4 H, CH2OAc and CO2-
CH2), 3.60 (m, 2 H, CH2OH), 3.06 (m, 2 H, H-5), 2.09 (s, 3 H,
OCOCH3), 1.95-2.1 (m, 4 H, CH2CHdCHCH2), 1.2-1.7 (m,
24 H), 0.88 (distorted t, 3 H,CH3(CH2)7CHdCH); 13C NMR
(CDCl3) δ 170.94, 165.94, 160.17, 136.66, 124.57, 85.43, 65.01,
64.38, 64.15, 63.67, 38.55, 33.39, 31.88, 29.54, 29.48, 29.41,
29.36, 29.30, 29.24, 29.20, 29.18, 29.12, 28.54, 26.51, 25.87,
22.68, 20.82, 14.10; MS m/e 480 (M+). Anal. (C28H48O6) C, H.

PKC Ligands Based on Tetrahydrofuran Templates
J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20 4137
Cl2. The organic layer was 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/hexane (1:2 to 1:1) as eluant to give 26 and 27 as oils,
respectively (0.484 g, 64%).
r el-(1R,3S)- a n d r el-(1S,3S)-Tetr a d ecyl 2-[3-(Hyd r oxy-
m e t h yl)-3-[(p h e n ylm e t h oxy)m e t h yl]-2-oxola n yl]a ce -
ta te (32 a n d 33). A solution of 25 (0.384 g, 1.0 mmol) in a
mixture of THF (10 mL) and H2O (10 mL) was treated with
LiOH (0.048 g, 2.0 mmol) and stirred for 16 h at room
temperature. The reaction mixture was concentrated to a small
volume, acidified to pH 3 with 1 N HCl, and extracted with
EtOAc several times. The combined organic layer was washed
with H2O, dried over MgSO4, and concentrated in vacuo to give
30 as an oil (0.348 g, 0.94 mmol, 94%). Acid 30 in CH2Cl2 (12
mL) was treated with 1-tetradecanol (0.242 g, 1.13 mmol),
(dimethylamino)pyridine (0.013 g, 0.1 mmol), and DCC (1.0
M in CH2Cl2, 1.9 mL, 1.9 mmol) and stirred for 16 h at room
temperature. The reaction mixture was treated with several
drops of acetic acid, stirred for 2 h, and concentrated. The
residue was purified by flash column chromatography on silica
gel with EtOAc/hexanes (1:7) as eluant to give 31 as an oil
(0.384 g, 0.68 mmol, 72%). Ester 31 in CH3CN-H2O (4:1, 10
mL) was cooled to 0 °C and treated with ammonium cerium-
(IV) nitrate (0.746 g, 1.36 mmol). After 4 h of stirring at 0 °C,
the reaction mixture was diluted with CH2Cl2. The organic
layer was 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/hexane (1:3
to 1:2) as eluant to give 32 and 33 as oils (0.204 g, 0.43 mmol,
63%).
26: Rf ) 0.36 (EtOAc:Hex ) 1:1); IR (neat) 3445 (OH), 1732
1
(CdO) cm-1; H NMR (CDCl3) δ 7.22-7.37 (m, 5 H, phenyl),
4.54 (dd of AB, 2 H, PhCH2O), 4.38 (m, 1 H, H-1), 3.68 (s, 3 H,
CO2CH3), 3.56 (dd of AB, 2 H, HOCH2), 3.39 (dd of AB, 2 H,
BnOCH2), 2.78 (s, 1 H, OH), 2.56 (ddd of AB, 2 H, CH2CO2-
Me), 1.83-2.16 (m, 3 H), 1.70 (m, 1 H); 13C NMR (CDCl3) δ
171.79, 138.07, 128.34, 127.58, 127.52, 85.46, 75.92, 73.45,
73.14, 66.01, 51.73, 40.16, 31.33, 29.48; MS m/e 295 (M+ + 1).
Anal. (C26H22O5) C, H.
27: Rf ) 0.29 (EtOAc:Hex ) 1:1); IR (neat) 3458 (OH), 1738
1
(CdO) cm-1; H NMR (CDCl3) δ 7.22-7.37 (m, 5 H, phenyl),
4.54 (dd of AB, 2 H, PhCH2O), 4.37 (m, 1 H, H-1), 3.67 (s, 3 H,
CO2CH3), 3.56 (dd of AB, 2 H, HOCH2), 3.41 (dd of AB, 2 H,
BnOCH2), 2.55 (ddd of AB, 2 H, CH2CO2Me), 2.43 (s, 1 H, OH),
1.60-2.16 (m, 3 H); 13C NMR (CDCl3) δ 171.54, 138.11, 128.29,
127.52, 127.45, 84.91, 75.94, 73.43, 73.33, 65.95, 51.54, 40.58,
31.36, 30.03; MS m/e 295 (M+ + 1). Anal. (C26H22O5) C, H.
r el-(1R,3R)-{3-[(Meth oxyca r bon yl)m eth yl]-1-[(p h en yl-
m eth oxy)m eth yl]-2-oxolan yl}m eth yl Tetr adecan oate (28).
This compound was obtained from 26 by following the same
1
procedure used for the synthesis of 16: oil; H NMR (CDCl3)
δ 7.22-7.37 (m, 5 H, phenyl), 4.55 (dd of AB, 2 H, PhCH2O),
4.39 (m, 1 H, H-3), 4.08 (dd of AB, 2 H, OCOCH2), 3.67 (s, 3
H, CO2CH3), 3.41 (dd of AB, 2 H, BnOCH2), 2.70 (dd of AB, 1
H, CH2CO2Me), 2.45 (dd of AB, 1 H, CH2CO2Me), 2.29 (t, 2 H,
CH2COO), 2.12 (m, 1 H), 1.86-1.93 (m, 2 H), 1.55-1.73 (m, 3
H), 1.2-1.4 (m, 20 H), 0.88 (distorted t, 3 H).
32: Rf ) 0.24 (EtOAc:Hex ) 1:3); IR (neat) 3460 (OH), 1732
1
(CdO) cm-1; H NMR (CDCl3) δ 7.25-7.37 (m, 5 H, phenyl),
4.54 (dd of AB, 2 H, PhCH2O), 4.39 (m, 1 H, H-1), 4.08 (t, 2 H,
COOCH2), 3.56 (dd of AB, 2 H, HOCH2), 3.40 (dd of AB, 2 H,
BnOCH2), 2.65 (s, 1 H, OH), 2.60 (dd of AB, 1 H, J ) 7.1 and
14.6 Hz, CH2CO2C14H29), 2.51 (dd of AB, 1 H, J ) 5.6 and 14.6
Hz, CH2CO2C14H29), 1.55-2.2 (m, 6 H), 1.2-1.4 (m, 22 H), 0.88
(distorted t, 3 H); 13C NMR (CDCl3) δ 171.40, 138.10, 128.31,
127.56, 127.51, 85.44, 76.03, 73.48, 73.21, 66.06, 64.82, 40.47,
31.84, 31.33, 29.57, 29.50, 29.45, 29.28, 29.17, 28.50, 25.81,
22.63, 14.05; MS m/e 477 (M+ + 1). Anal. (C29H48O5) C, H.
r el-(1R,3S)-{3-[(Meth oxyca r bon yl)m eth yl]-1-[(p h en yl-
m eth oxy)m eth yl]-2-oxolan yl}m eth yl Tetr adecan oate (29).
This compound was obtained from 27 by following the same
1
procedure used for the synthesis of 16: oil; H NMR (CDCl3)
δ 7.22-7.37 (m, 5 H, phenyl), 4.54 (s, 2 H, PhCH2O), 4.39 (m,
1 H, H-3), 4.10 (s, 2 H, OCOCH2), 3.66 (s, 3 H, CO2CH3), 3.40
(dd of AB, 2 H, BnOCH2), 2.70 (dd of AB, 1 H, CH2CO2Me),
2.45 (dd of AB, 1 H, CH2CO2Me), 2.31 (t, 2 H, CH2COO), 1.95-
2.10 (m, 2 H), 1.55-1.85 (m, 4 H), 1.2-1.4 (m, 20 H), 0.88
(distorted t, 3 H).
33: Rf ) 0.15 (EtOAc:Hex ) 1:3); IR (neat) 3460 (OH), 1732
1
(CdO) cm-1; H NMR (CDCl3) δ 7.25-7.37 (m, 5 H, phenyl),
4.54 (dd of AB, 2 H, PhCH2O), 4.37 (m, 1 H, H-1), 4.06 (t, 2 H,
COOCH2), 3.56 (dd of AB, 2 H, HOCH2), 3.42 (dd of AB, 2 H,
BnOCH2), 2.63 (dd of AB, 1 H, J ) 6.8 and 15.3 Hz,
CH2CO2C14H29), 2.45 (dd of AB, 1 H, J ) 6.3 and 15.3 Hz, CH2-
CO2C14H29), 1.55-2.2 (m, 6 H), 1.2-1.4 (m, 22 H), 0.88
(distorted t, 3 H); 13C NMR (CDCl3) δ 171.22, 138.15, 128.38,
127.63, 127.54, 84.80, 77.20, 76.10, 73.54, 66.17, 64.71, 40.97,
31.92, 31.44, 29.63, 29.57, 29.50, 29.34, 29.23, 28.57, 25.88,
22.68, 14.10; MS m/e 477 (M+ + 1). Anal. (C29H48O5) C, H.
r el-(1R,3R)-{1-(Hyd r oxym eth yl)-3-[(m eth oxyca r bon yl)-
m eth yl]-2-oxola n yl}m eth yl Tetr a d eca n oa te (5). A solution
of 28 (0.12 g, 0.24 mmol) in EtOAc (10 mL) was treated with
10% Pd-C (0.12 g) and hydrogenated under a hydrogen-filled
balloon. The reaction mixture was filtered, and the filtrate was
concentrated. The residue was purified by flash column
chromatography on silica gel with EtOAc/hexane (1:1) as
eluant to give 5 as a white solid (0.09 g, 90%): mp 52 °C; IR
r el-(1R,3R)-{1-[(P h en ylm eth oxy)m eth yl]-3-[(tetr adecyl-
oxyca r bon yl)m eth yl]-2-oxola n yl}m eth yl Hexa n oa te (34).
A solution of 32 (0.072 g, 0.15 mmol) in CH2Cl2 (5 mL) was
treated at 0 °C with triethylamine (0.084 mL, 0.6 mmol), a
catalytic amount of DMAP, and hexanoyl chloride (0.042 mL,
0.3 mmol). After 12 h of stirring at room temperature, the
reaction mixture was concentrated in vacuo. The residue was
purified by flash column chromatography on silica gel with
EtOAc/hexanes (1:3) as eluant to give 34 (0.082 g, 95%) as an
oil: 1H NMR (CDCl3) δ 7.25-7.37 (m, 5 H, phenyl), 4.55 (dd
of AB, 2 H, PhCH2O), 4.39 (m, 1 H, H-3), 4.0-4.12 (m, 4 H,
COOCH2CH2 and H11C5COOCH2), 3.42 (dd of AB, 2 H,
BnOCH2), 2.71 (dd of AB, 1 H, J ) 6.1 and 15.4 Hz,
CH2CO2C14H29), 2.43 (dd of AB, 1 H, J ) 7.1 and 15.4 Hz, CH2-
CO2C14H29), 2.29 (t, 2 H, CH2COO), 1.5-2.2 (m, 8 H), 1.2-1.4
(m, 26 H), 0.8-1.0 (m, 6 H).
1
(neat) 3459 (OH), 1731 (CdO) cm-1; H NMR (CDCl3) δ 4.40
(m, 1 H, H-3), 4.05 (dd of AB, 2 H, OCOCH2), 3.69 (s, 3 H,
CO2CH3), 3.51 (dd of AB, 2 H, HOCH2), 2.66 (dd of AB, 1 H, J
) 6.8 and 15.4 Hz, CH2CO2Me), 2.50 (dd of AB, 1 H, J ) 6.1
and 15.4 Hz, CH2CO2Me), 2.33 (t, 2 H, CH2COO), 2.15 (m, 1
H), 1.55-1.9 (m, 5 H), 1.2-1.4 (m, 20 H), 0.88 (distorted t, 3
H); 13C NMR (CDCl3) δ 173.78, 171.45, 84.23, 76.31, 65.77,
65.14, 51.67, 40.51, 34.21, 31.87, 31.40, 29.91, 29.63, 29.61,
29.56, 29.42, 29.32, 29.22, 29.11, 24.90, 22.65, 14.08; MS m/e
415 (M+ + 1). Anal. (C23H42O6) C, H.
r el-(1R,3S)-{1-(Hyd r oxym eth yl)-3-[(m eth oxyca r bon yl)-
m eth yl]-2-oxola n yl}m eth yl Tetr a d eca n oa te (7). This com-
pound was obtained from 29 by following the same procedure
used for the synthesis of 5: white solid; mp 40.5 °C; IR (neat)
1
3459 (OH), 1731 (CdO) cm-1; H NMR (CDCl3) δ 4.41 (m, 1
r el-(1R,3R)- a n d r el-(1R,3S)-{1-[(P h en ylm eth oxy)m eth -
yl]-3-[(tetr a d ecyloxyca r bon yl)m eth yl]-2-oxola n yl}m eth -
yl Hexa n oa te (35). This compound was obtained from 33 by
following the same procedure used for the synthesis of 34 as
an oil: 1H NMR (CDCl3) δ 7.25-7.37 (m, 5 H, phenyl), 4.54
(dd of AB, 2 H, PhCH2O), 4.38 (m, 1 H, H-3), 4.0-4.12 (m, 4
H, COOCH2CH2 and H11C5COOCH2), 3.40 (dd of AB, 2 H,
BnOCH2), 2.70 (dd of AB, 1 H, J ) 6.1 and 15.4 Hz,
CH2CO2C14H29), 2.42 (dd of AB, 1 H, J ) 7.6 and 15.4 Hz, CH2-
H, H-3), 4.04 (dd of AB, 2 H, OCOCH2), 3.70 (s, 3 H, CO2CH3),
3.52 (dd of AB, 2 H, HOCH2), 2.63 (dd of AB, 1 H, J ) 6.6 and
14.9 Hz, CH2CO2Me), 2.54 (dd of AB, 1 H, J ) 5.6 and 14.9
Hz, CH2CO2Me), 2.33 (t, 2 H, CH2COO), 2.15 (m, 1 H), 1.55-
1.9 (m, 5 H), 1.2-1.4 (m, 20 H), 0.88 (distorted t, 3 H); 13C
NMR (CDCl3) δ 173.80, 171.64, 84.70, 76.11, 65.87, 65.13,
51.76, 39.95, 34.18, 31.86, 31.19, 29.62, 29.58, 29.55, 29.39,
29.35, 29.30, 29.21, 29.08, 24.88, 22.63, 14.05; MS m/e 415 (M+
+ 1). Anal. (C23H42O6) C, H.

4138 J ournal of Medicinal Chemistry, 1999, Vol. 42, No. 20
Lee et al.
(14) Sharma, R.; Marquez, V. E.; Milne, G. W. A.; Lewin, N. E.;
Blumberg, P. M. Conformationally constrained analogues of
diacylglycerol. 5. 2,5-dideoxy-3-O-tetradecanoyl-D-galactono-1,4-
lactone: a superior homologue of 3-O-tetradecanoyl-2-deoxy-L-
ribonolactone with PK-C binding affinity. Bioorg. Med. Chem.
Lett. 1993, 3, 1993-1998.
(15) Lee, J .; Marquez, V. E.; Blumberg, P. M.; Krausz, K. W.;
Kazanietz, M. G. Conformationally constrained analogues of
diacylglycerol (DAG). 2. Differential interaction of δ-lactones and
γ-lactones with protein kinase C (PK-C). Bioorg. Med. Chem.
1993, 1, 119-123.
(16) Lee, J .; Marquez, V. E.; Lewin, N. E.; Blumberg, P. M. Synthesis
of two rigid diacylglycerol analogues having a perhydro furo-
[3,4-b]furan bis-γ-butyrolactone skeleton. 2. Tetrahedron Lett.
1993, 34, 4313-4316.
(17) Lee, J .; Marquez, V. E.; Bahador, A.; Kazanietz, M. G.; Blumberg,
P. M. Synthesis of two rigid diacylglycerol analogues having a
perhydro furo[3,2-b]furan bis-γ-butyrolactone skeleton. 3. Tet-
rahedron Lett. 1993, 34, 4317-4320.
CO2C14H29), 2.29 (t, 2 H, CH2COO), 1.55-2.2 (m, 8 H), 1.2-
1.4 (m, 26 H), 0.8-0.95 (m, 6 H).
r el-(1R,3R)-[1-(Hyd r oxym eth yl)-3-[(tetr a d ecyloxyca r -
bon yl)m eth yl]-2-oxola n yl]m eth yl Hexa n oa te (6). This
compound was obtained from 34 by following the same
procedure used for the synthesis of 5 as an oil: IR (neat) 3461
(OH), 1731 (CdO) cm-1; 1H NMR (CDCl3) δ 4.39 (m, 1 H, H-3),
4.0-4.12 (m, 4 H, COOCH2CH2 and H11C5COOCH2), 3.51 (dd
of AB, 2 H, HOCH2), 2.65 (dd of AB, 1 H, J ) 6.8 and 15.6 Hz,
CH2CO2C14H29), 2.47 (dd of AB, 1 H, J ) 6.6 and 15.6 Hz, CH2-
CO2C14H29), 2.33 (t, 2 H, CH2COO), 2.15 (m, 1 H), 1.5-1.9 (m,
7 H), 1.2-1.4 (m, 26 H), 0.85-0.95 (m, 6 H); 13C NMR (CDCl3)
δ 173.78, 171.11, 84.18, 76.41, 65.82, 65.16, 64.76, 40.82, 34.20,
31.90, 31.44, 31.26, 29.96, 29.63, 29.56, 29.50, 29.34, 29.23,
28.55, 25.88, 24.60, 22.66, 22.28, 14.08, 13.87; MS m/e 485 (M+
+ 1). Anal. (C28H52O6) C, H.
(18) Marquez, V. E.; Lee, J .; Sharma, R.; Teng, K.; Wang, S.; Bahador,
A.; Kazanietz, M. G.; Lewin, N. E.; Blumberg, P. M. Conforma-
tionally constrained analogues of diacylglycerol. 6. Changes in
PK-C binding affinity for 3-O-acyl-2-deoxy-L-ribonolactones
bearing different acyl chains. Bioorg. Med. Chem. Lett. 1994, 4,
355-360.
(19) Lee, J .; Marquez, V. E.; Lewin, N. E.; Blumberg, P. M. Confor-
mationally constrained analogues of diacylglycerol. 7. Interaction
of a medium-size ꢀ-lactone with protein kinase C (PK-C). Bioorg.
Med. Chem. Lett. 1994, 4, 543-548.
(20) Lee, J .; Sharma, R.; Teng, K.; Lewin, N. E.; Blumberg, P. M.;
Marquez, V. E. Conformationally constrained analogues of DAG.
8. Changes in PK-C binding affinity produced by isosteric groups
of the 3-O-acyl function in 2-deoxy-L-ribonolactones. Bioorg.
Med. Chem. Lett. 1994, 4, 1369-1374.
(21) Lee, J .; Lewin, N. E.; Blumberg, P. M.; Marquez, V. E. Confor-
mationally constrained analogues of diacylglycerol. 9. The effect
of side-chain orientation on the protein kinase C (PK-C) binding
affinity of δ-lactones. Bioorg. Med. Chem. Lett. 1994, 4, 2405-
2410.
r el-(1R,3S)-[1-(Hyd r oxym eth yl)-3-[(tetr a d ecyloxyca r -
bon yl)m eth yl]-2-oxola n yl]m eth yl Hexa n oa te (8). This
compound was obtained from 35 by following the same
procedure used for the synthesis of 5 as an oil: IR (neat) 3462
(OH), 1731 (CdO) cm-1; 1H NMR (CDCl3) δ 4.41 (m, 1 H, H-3),
4.09 (t, 2 H, COOCH2CH2), 4.01 (t, 2 H, H11C5COOCH2), 3.52
(dd of AB, 2 H, HOCH2), 2.64 (dd of AB, 1 H, J ) 6.6 and 14.7
Hz, CH2CO2C14H29), 2.52 (dd of AB, 1 H, J ) 5.9 and 14.7 Hz,
CH2CO2C14H29), 2.33 (t, 2 H, CH2COO), 2.0-2.2 (m, 2 H), 1.5-
1.85 (m, 6 H), 1.2-1.4 (m, 26 H), 0.85-0.95 (m, 6 H); 13C NMR
(CDCl3) δ 173.79, 171.31, 84.68, 76.23, 65.95, 65.20, 64.94,
40.31, 34.18, 31.90, 31.26, 29.63, 29.56, 29.50, 29.34, 29.21,
28.53, 25.84, 24.58, 22.61, 22.28, 14.08, 13.87; MS m/e 485 (M+
+ 1). Anal. (C28H52O6) C, H.
Ack n ow led gm en t. This work was supported in part
by Grant No. KOSEF 96-0403-01-01-3 from the Korea
Science and Engineering Foundation and by 99 S.N.U.
Research Fund.
(22) Lee, J .; Marquez, V. E.; Lewin, N. E.; Blumberg, P. M. Synthesis
of two rigid diacylglycerol analogues having a 1,7-dioxaspiro-
[4.4]nonane bis-γ-butyrolactone skeleton. 4. Synlett 1994, 206-
208.
(23) Lee, J .; Wang, S.; Barchi, J . J ., J r.; Marquez, V E. Synthesis of
a rigid diacylglycerol analogue having a bis-γ-butyrolactone
skeleton separated by a cyclopentane ring. Chem. Lett. 1995,
299-300.
(24) Sharma, R.; Lee, J .; Wang, S.; Milne, G. W. A.; Lewin, N. E.;
Blumberg, P. M.; Marquez, V. E. Conformationally Constrained
Analogues of Diacylglycerol. 10. Ultrapotent Protein Kinase C
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