Synthesis and biological evaluation of several structural analogs of 2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand

Article abstract of DOI:10.1016/j.bmc.2006.10.049

2-Arachidonoylglycerol (2-AG (1)) is an endogenous ligand for the cannabinoid receptors (CB1 and CB2). There is growing evidence that 2-arachidonoylglycerol plays important physiological and pathophysiological roles in various mammalian tissues and cells,

Full text of DOI:10.1016/j.bmc.2006.10.049

Bioorganic & Medicinal Chemistry 15 (2007) 854–867
Synthesis and biological evaluation of several structural analogs of
2-arachidonoylglycerol, an endogenous cannabinoid receptor ligand
Yoshitomo Suhara,a Saori Oka,b Atsushi Kittaka,a Hiroaki Takayama,a
Keizo Wakub and Takayuki Sugiurab,*
aDepartment of Pharmaceutical Chemistry, Faculty of Pharmcaceutical Sciences, Teikyo University,
Sagamihara, Kanagawa 199-0195, Japan
bDepartment of Molecular Health Science, Faculty of Pharmcaceutical Sciences, Teikyo University, Sagamihara,
Kanagawa 199-0195, Japan
Received 31 August 2006; revised 19 October 2006; accepted 20 October 2006
Available online 27 October 2006
Abstract—2-Arachidonoylglycerol (2-AG (1)) is an endogenous ligand for the cannabinoid receptors (CB1 and CB2). There is grow-
ing evidence that 2-arachidonoylglycerol plays important physiological and pathophysiological roles in various mammalian tissues
and cells, though the details remain to be clarified. In this study, we synthesized several remarkable analogs of 2-arachidonoylglycerol,
closely related in chemical structure to 2-arachidonoylglycerol: an analog containing an isomer of arachidonic acid with migrated
olefins (2-AGA118 (3)), an analog containing a one-carbon shortened fatty acyl moiety (2-AGA113 (4)), an analog containing an
one-carbon elongated fatty acyl moiety (2-AGA114 (5)), a hydroxy group-containing analog (2-AGA105 (6)), a ketone group-con-
taining analog (2-AGA109 (7)), and a methylene-linked analog (2-AGA104 (8)). We evaluated their biological activities as cannab-
inoid receptor agonists using NG108-15 cells which express the CB1 receptor and HL-60 cells which express the CB2 receptor.
Notably, these structural analogs of 2-arachidonoylglycerol exhibited only weak agonistic activities toward either the CB1 receptor
or the CB2 receptor, which is in good contrast to 2-arachidonoylglycerol which acted as a full agonist at these cannabinoid receptors.
These results clearly indicate that the structure of 2-arachidonoylglycerol is strictly recognized by the cannabinoid receptors (CB1 and
CB2) and provide further evidence that the cannabinoid receptors are primarily the intrinsic receptors for 2-arachidonoylglycerol.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
roblastoma x glioma hybrid cells,6 the inhibition of
long-term potentiation in rat hippocampal slices,7 the
inhibition of synaptic transmission in hippocampal neu-
rons,8 the suppression or potentiation of lymphocyte
proliferation,9 hypotension,10 and the migration of var-
ious types of leukocytes and microglia cells.11–13 Based
on the results of structure–activity relationship experi-
ments, we have proposed that 2-AG rather than ananda-
mide is the true natural ligand for the cannabinoid
receptors.3–5,14,15 Further detailed studies on 2-AG are
thus essential for a better understanding of the physio-
logical and pathophysiological roles of the endocannab-
inoid system in diverse mammalian tissues and cells.
2-Arachidonoylglycerol (2-AG) (1) is an arachidonic
acid-containing 2-monoacylglycerol isolated from rat
brain1 and canine gut2 as an endogenous ligand for
the cannabinoid receptors. 2-AG binds to both the
CB1 receptor, which is abundantly expressed in the ner-
vous system including the brain, and the CB2 receptor,
which is expressed in lymphoid organs such as the
spleen, with high affinity and exhibits a variety of bio-
logical activities. For example, 2-AG induces the inhibi-
tion of adenylyl cyclase,2 the inhibition of electrically
evoked contractions of the mouse vas deferens,2
a
Ca2+ transient in neuroblastoma x glioma hybrid
NG108-15 cells3,4 and promyelocytic leukemia HL-60
cells,5 the inhibition of a depolarization-induced eleva-
tion of the intracellular free Ca2+ concentration of neu-
In order to elucidate the pharmacological properties of
the receptor molecules, it is indispensable to prepare a
variety of structural analogs of endogenous ligands with
agonistic and antagonistic activities. Previously, we4,16
and Mechoulam et al.10 developed an ether-linked ana-
log of 2-AG (2-AG ether (2), HU-310). This compound
exhibited appreciable cannabimimetic activities in vitro
*
Corresponding author. Tel: +81 42 685 3746; fax: +81 42 685 1345;
e-mail: sugiurat@pharm.teikyo-u.ac.jp
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.10.049

Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
855
OH
O
OH
OH
O
O
OH
2-AG (1)
2-AG ether (2)
OH
OH
OH
OH
OH
OH
O
O
O
O
O
O
2-AGA118 (3)
2-AGA113 (4)
2-AGA114 (5)
2-AGA104 (8)
OH
OH
OH
OH
OH
OH
OH
O
2-AGA105 (6)
2-AGA109 (7)
Figure 1. Chemical structures of 2-AG and its structural analogs.
and in vivo. We also synthesized several structural ana-
logs and homologs of 2-AG.3–5 Among them,
(5Z,8Z,11Z)-1,3-dihydroxypropan-2-yl icosa-5,8,11-tri-
enoate (2-eicosatrienoylglycerol) and (5Z,8Z,11Z,14Z,
17Z)-1,3-dihydroxypropan-2-yl icosa-5,8,11,14,17-pen-
taenoate (2-eicosapentaenoylglycerol) are particularly
noteworthy because they possessed appreciable biologi-
cal activities; these analogs are potentially valuable
experimental tools in studies on the functions of the
endocannabinoid system. Despite these previous re-
ports, however, information concerning the structural
analogs of 2-AG is scarce compared with the case of
anandamide.
acid. The reaction mixture was stirred at 100 ꢁC for
30 min, then cooled to room temperature. Chromatog-
raphy on silica gel gave 3 in 72% yield. Compound 3
was further purified by borate-impregnated TLC to re-
move any contaminating migrated 1- or 3-isomer.
We next synthesized an analog of 2-AG containing a
one carbon-shortened fatty acyl moiety (4) and another
analog containing a one carbon-lengthened fatty acyl
moiety (5). The synthesis of 4 and 5 is summarized in
Schemes 2 and 3. An intermediate phosphonium salt
16, and aldehyde synthons 19a, 19b were prepared and
then combined using the Wittig reaction in a convergent
and stereoselective manner to obtain the necessary
precursors 20a, 20b. Chemical modification of these
compounds was then successively carried out to give
the desired compounds 4, 5.
In this study, we synthesized several remarkable analogs
of 2-AG closely related in chemical structure to 2-AG:
an analog containing an arachidonic acid isomer with
migrated olefins (3), an analog containing a one-carbon
shortened acyl chain (4), an analog containing a one-
carbon lengthened acyl chain (5), a hydroxy group-con-
taining analog (6), a ketone group-containing analog
(7), and a methylene-linked analog (8) (Fig. 1). We eval-
uated their biological activities as cannabinoid receptor
agonists using NG108-15 cells which express the CB1
receptor and HL-60 cells which express the CB2 recep-
tor and compared them with those of 2-AG.
Scheme 2 summarizes the synthesis of the intermediate al-
kyl chain synthon of 4 and 5. The common intermediate
in the synthesis of all these analogs of 1, namely
2-[(3Z,6Z,9Z)-pentadeca-3,6,9-trien-1-yl] triphenylphos-
phonium bromide (16), was prepared as follows.
Commercially available 2-octyn-1-ol was brominated
with phosphorus tribromide and the resulting halide 12
coupled with propargyl alcohol to give undeca-2,5-diyn-
1-ol (13) by a reported method.17 Diyne 13 was subse-
quently halogenated with 1,2-bis(diphenylphosphi-
no)ethane tetrabromide and the resulting bromide was
coupled with the tetrahydropyranyl ether of butynyl alco-
hol to yield the triyne 14 in 85% yield. Triyne 14 was then
converted to cis-triene by controlled hydrogenation using
a Lindlar catalyst. Traces of overreduced or underre-
duced products were removed by argentation chromatog-
raphy utilizing 10% silver nitrate on silica gel to give 15 in
62% yield.17,18 The resulting pure cis triene 15 was con-
verted to the bromide using 1,2-bis(diphenylphosphi-
no)ethane tetrabromide in one step and finally treated
with triphenylphosphine to afford 16 in 92% yield as a col-
orless oil.
2. Results and discussion
2.1. Chemistry
First, we synthesized (8Z,11Z,14Z,17Z)-1,3-dihydroxy-
propan-2-yl icosa-8,11,14,17-tetraenoate (2-AGA118)
(3). As shown in Scheme 1, the synthesis of 3 was carried
out from commercially available (8Z,11Z,14Z,17Z)-ico-
sa-8,11,14,17-tetraenoic acid (9) and 1,3-benzylidene-
glycerol (10).16 Esterification of 9 with alcohol 10
using N,N-dicyclohexylcarbodiimide (DCC) and 4-
N,N-dimethylaminopyridine (DMAP) in dry toluene at
room temperature for 6 h provided ester 11 in 69% yield.
Deprotection of the benzylidene group was accom-
plished by dissolving ester 11 in trimethyl borate at
room temperature followed by the addition of boric
As shown in Scheme 3, we chose pentenoic acid (17a)
and heptenoic acid (17b) as the starting materials to
make the aldehyde synthons 19a and 19b. After coupling

856
Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
O
OH
O
a
b
Ph
3
O
O
O
72%
69%
9
11
Scheme 1. Synthesis of 2-AGA118 (3). Reagents: (a) 1, 3-benzylideneglycerol (10), DCC, DMAP, toluene; (b) boric acid, trimethyl borate.
THPO
HO
b, c
a
HO
Br
85%
12
13
+
-
PPh3Br
OTHP
d
b, e
THPO
92%
62%
14
16
15
Scheme 2. Synthesis of an intermediate 16. Reagents and conditions: (a) EtMgBr, CuI; (b) Ph2PCH2CH2PPh2 Æ 2Br2; (c) EtMgBr, CuI; (d) H2/
Lindlar catalyst; (e) Ph3P, reflux 36 h.
O
n
O
O
O
n
O
O
n
O
O
c
b
a
Ph
Ph
O
OH
O
H
17a n= 2
17b n= 4
18a n= 2 (75%)
18b n= 4 (70%)
19a n= 2 (72%)
19b n= 4 (74%)
O
OH
OH
O
O
Ph
d
O
n
O
n
O
4
5
n= 2 (43%)
n= 4 (44%)
20a n= 2 (55%)
20b n= 4 (60%)
Scheme 3. Synthesis of 2-AGA113 (4) and 2-AGA114 (5). Reagents and conditions: (a) 10, DCC, DMAP; (b) O3 and then CH3SCH3; (c) 16,
LiHMDS, HMPA, À78 ꢁC; (d) boric acid, trimethyl borate, 100 ꢁC.
with 1,3-benzylideneglycerol (10) by the same method as
used for 2, ozonolysis of 18a and 18b, respectively, gave
the desired aldehyde synthons 19a and 19b in good yield.
Wittig coupling of the anion derived from phosphonate
16 with aldehydes 19a and 19b gave 55% and 60% yields
of each adduct 20a and 20b. Finally, deprotection of the
benzylidene group using boric acid and trimethyl borate
as described in Scheme 3 gave 4 and 5 in good yields.
containing analog. We first prepared a racemic 6 which
was then converted to the ketone group-containing ana-
log 7 through oxidation of the hydroxy group.
The key aldehyde synthon 29 for the synthesis of 6 and 7
was prepared from commercially available 5-hexen-1-ol
(21) as illustrated in Scheme 4. Protection of alcohol 21
with benzyl bromide using sodium hydride (NaH) fol-
lowed by oxidation with osmium tetraoxide (OsO4) gave
diol 23 in 72%. After selective tosylation of the primary
alcohol of 23, the tert-butyldimethylsilyl (TBS) group
was introduced into the secondary alcohol of 24 to af-
ford 25 in good yield. The tosylate was then converted
to iodide 26 with lithium iodide in dry acetone in 88%
yield. Alkylation of 26 with diethyl malonate employing
NaH gave dicarboxylate 27 in 88% yield. The benzyl
group of 27 was hydrogenated using palladium-activat-
ed carbon (Pd/C) in ethanol to afford the alcohol 28 in
97% yield. Swern oxidation of 28 afforded the desired
aldehyde 29 in 89% yield after purification by column
chromatography.
We then modified the bond between the glycerol back-
bone and arachidonic acid in compound 1. Previously,
an ether analog of 2-AG, 2-[(5Z,8Z,11Z,14Z)-icosa-
5,8,11,14-tetraenyloxy]propane-1,3-diol (2-AG ether,
HU-310) (2), was synthesized by us4,15 and by Mechou-
lam et al.10 The agonistic activities of this compound at
the cannabinoid receptors have already been evaluat-
ed.4,10,15 However, no other hydrolysis-resistant analogs
have been reported so far. Here, we synthesized two
structurally related analogs of 2-AG, that is, (8Z,11Z,
14Z,17Z)-2-(hydroxymethyl)tricosa-8,11,14,17-tetraene-
1,4-diol (2-AGA105) (6) and (8Z,11Z,14Z,17Z)-1-hy-
droxy-2-(hydroxymethyl)tricosa-8,11,14,17-tetraen-4-
one (2-AGA109) (7) (Fig. 1). Compound 6 is a hydroxy
group-containing analog whose ester bond was substitut-
ed by a methylene bond. Compound 7 is a ketone group-
The preparation of the 2-AG analogs 6 and 7 proceeded
as follows (Scheme 5). Wittig coupling of phosphonate
16 with aldehyde 29 gave a 69% yield of coupling prod-

Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
857
OH
OH
OH
OTs
97%
HO
BnO
BnO
BnO
72%
95%
74%
22
21
23
24
OTBS
COOEt
OTBS
OTBS
I
OTs
BnO
BnO
O
BnO
91%
88%
COOEt
88%
26
OTBS
27
25
OTBS
COOEt
COOEt
COOEt
COOEt
h
H
HO
89%
29
28
Scheme 4. Synthesis of an intermediate 29. Reagents: (a) NaH, BnBr; (b) OsO4, 4-methylmorpholine N-oxide; (c) TsCl, pyridine; (d) TBSCl,
imidazole; (e) LiI, acetone; (f) NaH, CH2(CO2Et)2; (g) H2, Pd/C; (h) Swern oxidation.
CO2Et
CO2Et
OH
OH
OTBS
OTBS
b
a
c
6
16 + 29
72%
81%
69%
30
31
OTIPS
OTIPS
OTIPS
OTIPS
O
OH
c
e
d
7
76%
74%
60%
32
33
Scheme 5. Synthesis of a 2-AGA109 (7). Reagents and conditions: (a) LiHMDS, HMPA, À78 to 0 ꢁC; (b) LiAlH4; (c) TBAF; (d) TIPSCl, imidazole,
DMF; (e) PDC.
uct 30. No trace of the trans isomer was produced as evi-
denced by the NMR spectrum. Reduction of the diethyl
ester of 30 with lithium aluminum hydride afforded the
diol 31 in 81% yield. The TBS-protecting group of 31
was removed by treatment with tetrabutylammonium
fluoride (TBAF) to produce the triol 6 in 72% yield.
Selective protection of the primary alcohol 6 using a tri-
isopropylsilyl (TIPS) group followed by oxidation of the
secondary alcohol 32 with pyridinium dichromate
(PDC); deprotection of the TIPS group then gave the
ketone analog 7 in good yield.
2.2. Biological activity
First, we examined the effects of 2-AG (1) and its struc-
tural analogs (2-AG ether, 2-AGA118 (3), 2-AGA113
(4), 2-AGA114 (5), 2-AGA105 (6), 2-AGA109 (7), and
2-AGA104 (8)) on the intracellular free Ca2+ concentra-
tion ([Ca2+]i) in NG108-15 cells which express the CB1
receptor. As illustrated in Figure 2, 2-AG induced a ra-
pid transient increase in [Ca2+]i in NG108-15 cells. The
response was detectable from a concentration as low
as 0.3 nM, and the EC50 value was calculated to be
23 nM. The effect of 2-AG was mediated via the CB1
receptor; treatment of the cells with SR141716A, a
CB1 receptor-specific antagonist, abolished the response
induced by 2-AG (data not shown). 2-AG ether, an
ether-linked analog of 2-AG, also induced a Ca2+ tran-
sient, although its activity was apparently weaker than
that of 2-AG. Notably, an analog of 2-AG containing
an isomer of arachidonic acid with migrated olefins (2-
AGA118) (3) exhibited only weak agonistic activity.
Two types of 2-AG analogs with one carbon-shortened
and one carbon-lengthened fatty acyl moieties, 2-
AGA113 (3) and 2-AGA114 (4), also possessed margin-
al agonistic activities. Similar markedly lower levels of
activity compared with that of 2-AG (1) were observed
with 2-AGA105 (6), 2-AGA109 (7), and 2-AGA 104
(8), which lack an ester linkage between the glycerol
backbone and the arachidonoyl moiety.
Finally, we synthesized a methylene-linked analog of 1
(2-AGA104) (8) (Scheme 6). This compound contains
a methylene bond instead of an ester bond between
the glycerol moiety and the fatty chain. For the synthesis
of 8, we chose 6-(tert-butyldimethylsilanyloxy)-hexan-
1-ol (34) as a starting material. The alcohol 34 was hal-
ogenated with methyltriphenoxyphosphonium iodide in
N,N-dimethylformamide (DMF) at room temperature
in good yield. Alkylation of the resulting iodide 35 via
a similar procedure as used for 27 gave dicarboxylate
36 in 75% yield. Although deprotection of the TBS
group with TBAF resulted in the alcohol 37, it was dif-
ficult to remove the solvent completely after purification
by silica gel column chromatography because the boiling
point of 37 was close to that of the solvent used. When
we tried to remove the solvent completely from the solu-
tion, compound 37 was also evaporated. This is why the
resulting compound 37 was crude and contained a small
amount of the solvent. The compound 37 was converted
to an aldehyde, and then Wittig coupling with 16 fol-
lowed by reduction of the dicarboxylate gave 8 in 12%
overall yield in three steps.
Figure 3 shows the effects of 2-AG and its structural
analogs on [Ca2+]i in HL-60 cells which express the
CB2 receptor. 2-AG induced a rapid increase in [Ca2+
]
i
in HL-60 cells as in the case of NG108-15 cells. The re-
sponse was detectable from 1 nM and the EC50 value

858
Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
COOEt
COOEt
a
b
I
OH
TBSO
TBSO
TBSO
75%
82%
34
35
36
COOEt
COOEt
c
d, e, f
12% (3 steps)
HO
8
35%
37
Scheme 6. Synthesis of a 2-AGA104 (8). Reagents and conditions: (a) CH3P(OC6H5)3I, DMF; (b) NaH, CH2(CO2Et)2; (c) TBAF in THF; (d) Swern
oxidation; (e) 16, LiHMDS, HMPA, À78 to 0 ꢁC; (f) LiAlH4.
B
D
A
C
E
F
G
H
Figure 2. Effects of 2-AG and its structural analogs on [Ca2+]i in NG108-15 cells. A, 2-AG (1); B, 2-AG ether (2); C, 2-AGA118 (3); D, 2-AGA113
(4); E, 2-AGA114 (5); F, 2-AGA105 (6); G, 2-AGA109 (7); H, 2-AGA104 (8). The data are means SD from five to six determinations.
was 17 nM. The response induced by 2-AG was abro-
gated by treatment of the cells with SR144528, a CB2
receptor-specific antagonist (data not shown), indicating
that the CB2 receptor is involved in the response. On the
other hand, the activities of various structural analogs of
2-AG examined here (2-AG ether, 2-AGA118 (3),
2-AGA113 (4), 2-AGA114 (5), 2-AGA105 (6),
2-AGA109 (7), and 2-AGA104 (8)) were markedly
weaker than that of 2-AG as in the case of NG108-15
cells. The magnitude of the response induced by each
of these compounds was rather small even at 3 lM.
2-oleoylglycerol, did not exhibit any agonistic activity.
The activities of 2-linoleoylglycerol, 2-c-linolenoylglyc-
erol, and 2-docosahexaenoylglycerol were also found
to be negligible. 2-Eicosapentaenoylglycerol possessed
appreciable agonistic activity, yet its activity was mark-
edly weaker than that of 2-AG. Thus, the presence of the
arachidonoyl moiety in the molecule is crucial to the
activity. We also found that the isopropanol-type analog
of 2-AG did not exhibit any agonistic activity. The activ-
ity levels of the ethyleneglycol-type analog of 2-AG
(arachidonoylethyleneglycol) and 2-hydroxypropyl ara-
chidonate were lower than that of 2-AG, indicating that
the presence of the glycerol moiety is also essential.
These results strongly suggested that the structure of
2-AG is strictly recognized by the receptor mole-
cules.3–5
2.3. Discussion
Previously, we examined in detail the biological activi-
ties of 2-AG and various 2-AG analogs using NG108-
15 cells and HL-60 cells.3,4 We found 2-AG to have
the highest level of activity among the various structural
analogs. For example, saturated or monoenoic
2-monoacylglycerols, such as 2-palmitoylglycerol and
In the present study, we synthesized several novel struc-
tural analogs of 2-AG, closely related in chemical struc-
ture to 2-AG, and compared their biological activities to

Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
859
A
B
D
E
F
G
H
Figure 3. Effects of 2-AG and its structural analogs on [Ca2+]i in HL-60 cells. A, 2-AG (1); B, 2-AG ether (2); C, 2-AGA118 (3); D, 2-AGA113 (4); E,
2-AGA114 (5); F, 2-AGA105 (6); G, 2-AGA109 (7); H, 2-AGA104 (8). The data are means SD from five to six determinations.
that of 2-AG. As shown in Figures 2 and 3, 2-AG acted
as a full agonist and exhibited the most potent agonistic
effect among the various structural analogs examined
here. Importantly, any modification to the structure of
2-AG, even if it appeared to be minor, markedly reduced
the agonistic activity of 2-AG. It is apparent, therefore,
that the presence of the arachidonoyl moiety, the glycer-
ol backbone, and the ester linkage is indispensable for
exhibiting strong agonistic activity. These results rein-
force the hypothesis that the cannabinoid receptors
(CB1 and CB2) are primarily the ‘2-AG receptors’; var-
ious analogs of 2-AG employed here, closely related in
chemical structure to 2-AG, are thus valuable experi-
mental tools in the elucidation of the structure and
properties of the cannabinoid receptor molecules.
In relation to this, it should be noted that 2-AG ether
exhibits appreciable biological activities comparable to
those of 2-AG in vivo10,24 and in prolonged incubation
experiments in vitro,25 although its level of activity
was apparently lower than that of 2-AG estimated in
short-term incubation experiments in vitro.4,5 This is
probably due to the fact that 2-AG ether is metabolical-
ly stable compared with 2-AG, especially in vivo and in
prolonged incubation experiments in vitro. By the way,
several of the 2-AG analogs examined in the present
study are also metabolically rather stable. For example,
2-AGA105 (6), 2-AGA109 (7), and 2-AGA104 (8) are
resistant to hydrolytic enzymes due to the lack of an es-
ter bond in the molecule. It is possible, therefore, that
these compounds may exhibit appreciable cannabimi-
metic activities in vivo, like 2-AG ether, and can be used
as valuable tools in exploring the physiological and
pathophysiological significance of 2-AG. Further de-
tailed studies are thus essential to evaluate the exact bio-
logical activities of these novel 2-AG analogs in vivo.
Several remarkable analogs of 2-AG have also been syn-
thesized by other investigators. Parkkari et al.19 recently
reported that a dimethylheptyl derivative of 2-AG is a
weak CB1 receptor agonist, and Bobrov et al.20 demon-
strated that a,a-dimethyl arachidonoylethyleneglycol
acts as a weak CB1 and CB2 receptor agonist. Parkkari
et al.21 also reported the synthesis of an a-methylated
analog of 2-AG and a fluorine-containing analog of 2-
AG. Interestingly, the a-methylated analog of 2-AG
was much more stable toward hydrolytic enzymes than
2-AG, which is in agreement with the assertion by other
investigators that the a-methylated analog of 1-AG is
metabolically rather stable and can be used as an inhib-
itor of monoacylglycerol lipase.22,23 Of note, the a-meth-
ylated analog of 2-AG possessed biological activity only
slightly weaker than that of 2-AG, while a fluorine-con-
taining analog of 2-AG did not exhibit any biological
activity. The a-methylated analog of 2-AG may become
a useful experimental tool in the elucidation of the phys-
iological and pathophysiological roles of 2-AG, espe-
cially those in vivo.
3. Conclusion
We synthesized several remarkable analogs of 2-AG (2-
AGA118 (3), 2-AGA113 (4), 2-AGA114 (5), 2-AGA105
(6), 2-AGA109 (7), and 2-AGA104 (8)) which are closely
related in chemical structure to 2-AG. Notably, these
structural analogs exhibited only weak agonistic activi-
ties toward either the CB1 receptor or the CB2 receptor,
while 2-AG acted as a full agonist toward these cannab-
inoid receptors. A modification of the structure of 2-
AG, even a minor one, markedly reduced the agonistic
activity of 2-AG. It is apparent, therefore, that an intact
arachidonoyl moiety, glycerol backbone, and ester
linkage are crucially important for having potent ago-
nistic activities. Based on these experimental results

860
Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
and those in previous studies, we concluded that both
the CB1 receptor and the CB2 receptor are the intrin-
sic-specific receptors for 2-AG.
TLC (hexane/ethyl acetate, 5:1, v/v) to give 11 (5.2 mg,
yield 69%) as a colorless oil: 1H NMR (400 MHz,
CDCl3) d 7.52–7.50 (m, 2H), 7.39–7.36 (m, 3H), 5.56
(s, 1H), 5.42–5.29 (m, 8H), 4.72 (br s, 1H), 4.28 (d,
2H, J = 12.6 Hz), 4.17 (d, 2H, J = 13.2 Hz), 2.85–2.81
(m, 6H), 2.44–2.40 (m, 2H), 2.09–2.04 (m, 4H), 1.82–
1.60 (m, 2H), 1.39–1.28 (m, 6H), 0.98 (br t, 3H,
J = 7.7 Hz); 13C NMR (100 MHz, CDCl3) d 173.8,
137.8, 130.2, 129.1, 128.5, 128.4, 128.3, 128.02, 127.96,
127.8, 127.1, 126.0, 101.2, 69.2, 65.7, 34.0, 32.8, 30.9,
29.5, 29.0, 27.2, 26.4, 25.6, 24.7, 22.5, 14.0; MS 466
[M]+; HRMS calcd for [C30H42O4] 466.3084; found
466.3073.
Not much attention has thus far been directed to 2-AG
compared with anandamide,14,15 yet it is becoming evi-
dent that 2-AG plays pivotal roles as the true natural li-
gand for the cannabinoid receptors in various
mammalian tissues and cells. Thus, further intensive
studies on 2-AG are indispensable for a thorough eluci-
dation of the physiological and pathophysiological roles
of the endocannabinoid system. In order to promote
such studies, it is essential to develop a number of struc-
tural analogs of 2-AG which may mimic the functions of
2-AG: metabolically stable 2-AG analogs would become
valuable experimental tools, especially in prolonged
incubation experiments and in vivo experiments, as
receptor agonists or as inhibitors of monoacylglycerol li-
pase and the thioester bond-containing analog of 2-AG
may be useful as a synthetic substrate in the measure-
ment of monoacylglycerol lipase activity. Nevertheless,
the number of available 2-AG analogs is still limited.
Further detailed studies are needed to synthesize and
provide a variety of novel 2-AG analogs. The develop-
ment of various 2-AG analogs with different chemical
structures, characteristics, and agonistic or antagonistic
activities would greatly contribute to the thorough eluci-
dation of the physiological and pathophysiological sig-
nificance of 2-AG and the cannabinoid receptors in
mammalian tissues.
4.3. (8Z,11Z,14Z,17Z)-1,3-Dihydroxypropan-2-yl icosa-
8,11,14,17-tetraenoate (3)
A suspension of 11 (2.5 mg, 5.4 lmol) and boric acid
(662 lg, 10.7 mmol) in trimethyl borate (1 mL) was re-
fluxed at 100 ꢁC for 20 min. After being cooled to room
temperature, the reaction mixture was diluted with ethyl
acetate (5 mL) and successively washed with 3 mL of
water and brine. The organic layer was dried (MgSO4),
and the solvent was evaporated in vacuo. Preparative
TLC (CHCl3/MeOH, 20:1, v/v) of the crude residue pro-
vided the product 3 (1.5 mg, yield 72%) as a colorless oil:
1H NMR (400 MHz, CDCl3) d 5.38–5.37 (m, 8H), 4.92
(tt, 1H, J = 4.8, 4.8 Hz), 3.84 (d, 4H, J = 4.9 Hz),
2.85–2.80 (m, 6H), 2.38 (t, 2H, J = 7.5 Hz), 2.21 (br s,
2H), 2.08–2.05 (m, 4H), 1.71–1.68 (m, 2H), 1.39–1.31
(m, 6H), 0.98 (br t, 3H, J = 7.5 Hz); 13C NMR
(100 MHz, CDCl3) d 174.0, 132.0, 130.2, 128.5, 128.4,
128.03, 127.97, 127.8, 127.1, 75.0, 62.5, 34.3, 29.4,
29.0, 28.9, 27.2, 25.6, 24.9, 20.6, 14.3; MS 378 [M]+;
HRMS calcd for [C23H38O4] 378.2770; found 378.2779.
4. Experimental
4.1. General
1H NMR spectra were recorded on a JEOL GSX-400
spectrometer at 400 MHz and 13C NMR spectra were
recorded at 100 MHz using CDCl3 as a solvent unless
otherwise specified. Chemical shifts are given in ppm
(d) using tetramethylsilane (TMS) as the internal stan-
dard. MS spectra (EIMS) and high-resolution MS spec-
tra (HREIMS) were recorded on a JEOL JMX-SX 102
A mass spectrometer. Column chromatography was car-
ried out on silica gel 60 (70–230 mesh) and preparative
thin layer chromatography (TLC) was run on silica gel
60F254. Unless otherwise noted, all reagents were pur-
chased from commercial suppliers and used as received.
4.4. Undeca-2,5-diyn-1-ol (13)
Compound 13 was prepared from 2-octyn-1-ol and 1-
bromooct-2-yne (12) by a reported method.17
4.5. (Pentadeca-3,6,9-triyloxy)tetrahydro-2H-pyran (14)
A solution of bromine (3.33 mL, 64.6 mmol) in CH2Cl2
(30 mL) was added slowly dropwise to a solution of
1,2-bis(diphenylphosphino)ethane (14.2 g, 35.6 mmol)
in CH2Cl2 (150 mL) under an argon atmosphere at 0 ꢁC.
Diyne 13 (5.3 g, 32.3 mmol) in CH2Cl2 (30 mL) was add-
ed to this mixture, and the resultant solution was stirred
at room temperature for 2 h. The volume of the reaction
mixture was reduced in vacuo to 15 mL and diethyl ether
(300 mL) was added. Pentane (600 mL) was added to the
diethyl ether solution and the organic solution was dried
over MgSO4. The mixture was filtered through a pad of
silica gel (Merck, 40–60 lm). The eluate was concentrat-
ed in vacuo to afford 1-bromo-2,5-undecadiyne (7.2 g,
yield 99%) as a colorless oil. Next, a solution of bromoe-
thane (2.64 mL, 35.6 mmol) in dry tetrahydrofuran
(THF) (20 mL) was added dropwise to magnesium
(788 mg, 32.4 mmol) in THF (40 mL) at 0 ꢁC under an
atmosphere of argon. After the addition was completed,
the reaction mixture was stirred at ambient temperature
until all the magnesium dissolved. A solution of 2-(3-
4.2. (8Z,11Z,14Z,17Z)-2-Phenyl-1,3-dioxan-5-yl icosa-
8,11,14,17-tetraenoate (11)
To a solution of 1,3-benzylidene glycerol (10) (4.4 mg,
24.6 lmol) and (8Z,11Z,14Z,17Z)-icosa-8,11,14,17-tet-
raenoic acid (9) (5 mg, 16.4 lmol) in dry toluene
(1 mL) were added DCC (6.8 mg, 33.0 lmol) and
DMAP (200 lg, 1.6 lmol) at 0 ꢁC under an argon atmo-
sphere. After stirring at 0 ꢁC for 2 h and then at room
temperature for 12 h, the reaction mixture was diluted
with ethyl acetate (5 mL). The mixture was washed with
water (3 mL) and brine (3 mL), and then the organic
layer was separated, dried over MgSO4, and concentrat-
ed in vacuo. The residue was purified with preparative

Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
861
butynyloxy)tetrahydro-2H-pyran (5.0 g, 32.4 mmol) in
THF (15 mL) was slowly added to the cooled ethylmag-
nesium bromide solution. After stirring at 23 ꢁC for 10 h,
copper (I) iodide (300 mg) was added and the mixture
was stirred for an additional 15 min. 1-Bromo-2,5-
undecadiyne (7.2 g, 31.8 mmol) in THF (15 mL) was
added, and the resulting mixture was stirred at room
temperature for 2 h. The reaction mixture was poured
into a solution of 2 N H2SO4 (50 mL) and ice (20 mL).
The resultant solution was extracted with diethyl ether
(3· 20 mL), and the diethyl ether extracts were washed
with saturated aqueous NH4Cl (20 mL) and saturated
aqueous Na2CO3 (20 mL) and dried over MgSO4. The
solvent was removed and the residue was chromato-
graphed on silica gel (ether/hexane, 1:20, v/v) to provide
one portion. The mixture was stirred at room tempera-
ture for 9 h. The solvent was removed in vacuo and the
residue was dissolved in hexane/diethyl ether (2:1, v/v)
(600 mL). The solution was filtered through a pad of sil-
ica gel to afford crude 1-bromo-3,6,9-tetradecatriene
(2.22 g, yield 92%).
The bromo compound (3.60 g, 12.7 mmol) was dissolved
in dry acetonitrile (100 mL), and triphenylphosphine
(6.65 g, 25.3 mmol) was added. The reaction mixture
was refluxed for 36 h under an argon atmosphere and
then concentrated in vacuo. The phosphonium salt 16
was purified by flash column chromatography
(CH2Cl2/MeOH, 19:1, v/v) to afford the pure phospho-
1
nium salt 16 (6.40 g, yield 92%) as a white powder: H
1
triyne 14 (8.2 g, yield 85%) as a colorless oil: H NMR
NMR (400 MHz, CDCl3) d 7.89–7.70 (m, 15H), 5.40–
5.19 (m, 6H), 3.88–3.86 (m, 2H), 2.64 (t, 1H,
J = 7.2 Hz), 2.58 (t, 1H, J = 7.4 Hz), 2.48 (m, 2H),
2.17–1.96 (m, 4H), 1.35–1.24 (m, 6H), 0.88 (t, 3H,
J = 6.9 Hz); 13C NMR (100 MHz, CDCl3) d 135.0,
133.7, 133.6, 130.6, 130.5, 130.4, 130.3, 128.9, 127.1,
118.6, 117.7, 31.4, 29.2, 27.1, 25.5, 22.4, 14.0; MS 546
[M]+; HRMS calcd for [C33H40PBr] 546.2051; found
546.2056.
(400 MHz, CDCl3) d 4.62 (dd, 1H, J = 3.1, 4.1 Hz),
3.91–3.86 (m, 1H), 3.80 (tt, 1H, J = 7.2, 7.2 Hz), 3.57–
3.48 (m, 2H), 3.12 (s, 4H), 2.49–2.45 (m, 2H), 2.17–2.13
(m, 2H), 1.87–1.79 (m, 1H), 1.75–1.69 (m, 1H), 1.63–
1.45 (m, 6H), 1.38–1.27 (m, 4H), 0.90 (t, 3H,
J = 6.9 Hz); 13C NMR (100 MHz, CDCl3) d 98.7, 80.8,
77.4, 74.93, 74.89, 74.4, 73.6, 65.7, 62.1, 31.0, 30.5,
28.4, 25.4, 22.1, 20.1, 19.4, 18.6, 13.9; FAB-MS(NBA-
NaI) 301 [M+H]+; HR-FAB-MS calcd for [C20H29O2]
301.2167; found 301.2144.
4.8. 2-Phenyl-1,3-dioxan-5-yl pent-4-enoate (18a)
4.6. 2-((3Z,6Z,9Z)-Pentadeca-3,6,9-trienyloxy)tetrahy-
dro-2H-pyran (15)
To a solution of 4-pentenoic acid (17a) (510 lL,
5.0 mmol) in toluene (10 mL) were added DCC
(2.06 g, 10.0 mmol), DMAP (61 mg, 0.5 mmol), and 10
(1.16 g, 6.0 mmol) at 0 ꢁC under an argon atmosphere.
After stirring at 0 ꢁC for 2 h and then at room tempera-
ture for 12 h, the reaction mixture was diluted with ethyl
acetate (50 mL). The mixture was washed with water
(30 mL) and brine (30 mL), then the organic layer was
separated, dried over MgSO4, and concentrated in vac-
uo. The residue was chromatographed on silica gel (hex-
ane/ethyl acetate, 5:1, v/v) to give 18a (980 mg, yield
To a solution of 14 (330 mg, 1.10 mmol) in ethanol
(10 mL) were added triethylamine (0.1 mL) and Lindlar
catalyst (100 mg) under an argon atmosphere at room
temperature. Hydrogenation was performed at atmo-
spheric pressure at 0 to 5 ꢁC for 5 h and then at room
temperature for 24 h. The solution was filtered to re-
move the catalyst, and the filtrate was then evaporated
at reduced pressure to give crude triene 15, which was
purified by argentation chromatography utilizing 10%
silver nitrate on silica gel (diethyl ether/hexane, 1:20, v/
v) to give pure 15 (208 mg, yield 62%) as a colorless
1
75%) as a colorless oil: H NMR (400 MHz, CDCl3) d
7.52–7.50 (m, 2H), 7.40–7.34 (m, 3H), 5.90–5.80 (m,
1H), 5.55 (s, 1H), 5.09 (dd, 1H, J = 1.5, 17.1 Hz), 5.01
(dd, 1H, J = 1.5, 10.6 Hz), 4.72 (dd, 1H, J = 1.5,
3.0 Hz), 4.27 (dd, 2H, J = 1.5, 13.1 Hz), 4.16 (dd, 2H,
J = 1.5, 13.1 Hz), 2.57–2.53 (m, 2H), 2.46–2.40 (m,
2H); 13C NMR (100 MHz, CDCl3) d 173.0, 137.8,
136.5, 129.0, 128.2, 126.0, 115.6, 101.2, 69.0, 65.9,
33.6, 28.8; MS 262 [M]+; HRMS calcd for [C15H18O4]
262.1205; found 262.1209.
1
oil: H NMR (400 MHz, CDCl3) d 5.46–5.32 (m, 6H),
4.60 (dd, 1H, J = 2.7, 4.0 Hz), 3.90–3.85 (m, 1H), 3.75
(tt, 1H, J = 7.0, 7.0 Hz), 3.53–3.48 (m, 1H), 3.42 (tt,
1H, J = 7.0, 7.0 Hz), 2.86–2.80 (m, 4H), 2.41–2.37 (m,
2H), 2.05 (dd, 2H, J = 6.7, 13.7 Hz), 1.86–1.80 (m,
1H), 1.75–1.69 (m, 1H), 1.59–1.50 (m, 4H), 1.40–1.27
(m, 6H), 0.89 (t, 3H, J = 6.9 Hz); 13C NMR
(100 MHz, CDCl3) d 130.4, 129.8, 128.5, 127.9, 127.6,
126.1, 98.7, 66.9, 62.3, 31.5, 30.7, 29.3, 28.0, 27.2, 25.7,
25.6, 25.5, 22.5, 19.6, 14.0; MS 306 [M]+; HRMS calcd
for [C20H34O2] 306.2558; found 306.2554.
4.9. 2-Phenyl-1,3-dioxan-5-yl hept-6-enoate (18b)
Compound 18b was prepared from 6-heptenoic acid
(17b) (946 mg, 7.38 mmol) in a manner similar to that
for 18a. Chromatography on silica gel (hexane/ethyl ace-
tate, 5:1, v/v) gave 18b (1.50 g, yield 70%) as a colorless
4.7. 2-[(3Z,6Z,9Z)-Pentadeca-3,6,9-trien-1-yl] triphenyl-
phosphonium bromide (16)
1
oil: H NMR (400 MHz, CDCl3) d 7.52–7.49 (m, 2H),
A solution of bromine (0.88 mL, 17.0 mmol) was slowly
added dropwise to
7.39–7.34 (m, 3H), 5.84–5.74 (m, 1H), 5.55 (s, 1H),
5.01 (dt, 1H, J = 1.1, 7.1 Hz), 4.95 (dt, 1H, J = 1.1,
10.0 Hz), 4.70 (s, 1H), 4.27 (d, 2H, J = 13.0 Hz), 4.15
(dd, 2H, J = 1.0, 13.0 Hz), 2.44 (t, 2H, J = 7.6 Hz),
2.08 (dd, 2H, J = 6.8, 13.9 Hz), 1.73–1.63 (m, 2H),
1.50–1.41 (m, 2H); 13C NMR (100 MHz, CDCl3) d
173.3, 138.1, 137.7, 128.9, 128.1, 125.8, 114.5, 101.1,
a
solution of 1,2-bis(diph-
enylphosphino)ethane (3.73 g, 9.36 mmol) in CH2Cl2
(20 mL) under an argon atmosphere at 0 ꢁC. A slight
excess of 1,2-bis(diphenylphosphino)ethane was added
back to the solution until the light yellow color disap-
peared. Triene 15 (2.60 g, 8.49 mmol) was added in

862
Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
69.1, 65.7, 34.3, 33.4, 28.4, 24.5; MS 290 [M]+; HRMS
calcd for [C17H22O4] 290.1518; found 290.1525.
2H), 7.38–7.35 (m, 3H), 5.56 (s, 1H), 5.40–5.32 (m,
8H), 4.72 (t, 1H, J = 1.5 Hz), 4.27 (dd, 2H, J = 1.5,
12.8 Hz), 4.17 (dd, 2H, J = 1.5, 12.8 Hz), 2.85–2.80 (m,
6H), 2.47–2.43 (m, 4H), 2.12–2.03 (m, 2H), 1.45–1.26
(m, 6H), 0.88 (t, 3H, J = 6.9 Hz); 13C NMR
(100 MHz, CDCl3) d 173.1, 137.8, 130.5, 129.6, 129.4,
129.0, 128.6, 128.4, 128.3, 128.0, 127.8, 127.7, 127.5,
126.0, 101.2, 69.1, 65.9, 34.2, 31.5, 29.3, 27.2, 25.6,
22.7, 22.5, 14.0; MS 452 [M]+; HRMS calcd for
[C29H40O4] 452.2926; found 452.2924.
4.10. 2-Phenyl-1,3-dioxan-5-yl 3-formylpropanoate (19a)
A solution of 18a (720 mg, 2.75 mmol) in methanol
(20 mL) and methylene chloride (5 mL) under nitrogen
was ozonized at À78 ꢁC for 1 h. After the solution
turned blue, the ozone was removed, and the reaction
mixture was quenched with dimethyl sulfide (5 mL)
and allowed to warm to 23 ꢁC. The solvent was
removed and the crude product dissolved in diethyl
ether (10 mL) and washed with dilute acetic acid and
water. The diethyl ether layer was dried (MgSO4), the
solvent was removed, and the crude residue was
chromatographed on silica gel (ether/pentane, 1:3, v/v)
4.13. (6Z,9Z,12Z,15Z)-2-Phenyl-1,3-dioxan-5-yl henico-
sa-6,9,12,15-tetraenoate (20b)
Compound 20b was prepared from 19b (143 mg,
490 lmol) as described for 20a. Purification with silica
gel column chromatography (hexane/ethyl acetate, 5:1,
v/v) provided 20b (141 mg, yield 60%) as a colorless
1
to give 19a (522 mg, yield 72%) as a colorless oil: H
NMR (400 MHz, CDCl3) d 9.82 (s, 1H), 7.51–7.49
(m, 2H), 7.39–7.35 (m, 3H), 5.56 (s, 1H), 4.73 (br s
1H), 4.28 (dd, 2H, J = 1.0, 13.2 Hz), 4.16 (dd, 2H,
J = 1.0, 12.8 Hz), 2.84 (t, 1H, J = 6.6 Hz), 2.76 (dt,
1H, J = 1.1, 6.1 Hz), 2.60–2.53 (m, 2H); 13C NMR
(100 MHz, CDCl3) d 199.8, 172.2, 137.8, 129.1, 128.3,
126.0, 101.2, 69.0, 38.5, 26.8; MS 264 [M]+; HRMS
calcd for [C14H16O5] 264.0998; found 264.0997.
1
oil: H NMR (400 MHz, CDCl3) d 7.52–7.49 (m, 2H),
7.40–7.34 (m, 3H), 5.56 (s, 1H), 5.43–5.31 (m, 8H),
4.72 (t, 1H, J = 1.7 Hz), 4.27 (dd, 2H, J = 1.7,
13.1 Hz), 4.17 (dd, 2H, J = 1.7, 13.1 Hz), 2.85–2.77
(m, 6H), 2.45 (t, 2H, J = 7.5 Hz), 2.12–2.03 (m, 4H),
1.74–1.66 (m, 2H), 1.47–1.24 (m, 8H), 0.89 (t, 3H,
J = 6.9 Hz); 13C NMR (100 MHz, CDCl3) d 173.6,
137.8, 130.5, 129.7, 129.0, 128.5, 128.3, 128.2, 128.1,
127.9, 127.6, 126.0, 101.2, 69.1, 65.8, 34.3, 31.5, 29.3,
29.1, 27.2, 26.9, 25.6, 24.6, 22.6, 14.0; MS 480 [M]+;
HRMS calcd for [C31H44O4] 480.3239; found
480.3249.
4.11. 2-Phenyl-1,3-dioxan-5-yl 4-formylbutanoate (19b)
Compound 19b was prepared from 18b (400 mg,
1.37 mmol) in the same fashion as described for 19a.
Purification with silica gel column chromatography
(diethyl ether/pentane, 1:3, v/v) gave 19b (298 mg, yield
4.14. (4Z,7Z,10Z,13Z)-1,3-Dihydroxypropan-2-yl nona-
deca-4,7,10,13-tetraenoate (4)
1
74%) as a colorless oil: H NMR (400 MHz, CDCl3) d
9.72 (s, 1H), 7.50–7.49 (m, 2H), 7.39–7.33 (m, 3H),
5.06 (s, 1H), 4.69 (s, 1H), 4.24 (d, 2H, J = 12.7 Hz),
4.13 (d, 2H, J = 13.0 Hz), 2.47–2.42 (m, 2H), 2.14 (br
s, 2H), 1.80–1.56 (m, 4H); 13C NMR (100 MHz, CDCl3)
d 201.7, 173.1, 129.2, 127.8, 125.6, 100.8, 68.7, 65.7,
33.9, 30.7, 23.9; MS 292 [M]+; HRMS calcd for
[C16H20O5] 292.1311; found 292.1313.
Compound 4 was prepared from 20a (60 mg, 133 lmol)
as described for 3. Purification with silica gel column
chromatography (hexane/ethyl acetate, 5:1) and bo-
rate-impregnated TLC gave pure 4 (21 mg, yield 43%
1
overall) as a colorless oil: H NMR (400 MHz, CDCl3)
d 5.46–5.32 (m, 8H), 4.93 (tt, 1H, J = 5.0, 5.0 Hz), 3.83
(dd, 4H, J = 1.5, 5.0 Hz), 2.86–2.80 (m, 6H), 2.47–2.40
(m, 4H), 2.17 (br s, 2H), 2.05 (dd, 2H, J = 6.6, 13.7
Hz), 1.38–1.25 (m, 6H), 0.89 (br t, 3H, J = 7.0 Hz);
13C NMR (100 MHz, CDCl3) d 173.3, 130.6, 129.7,
128.7, 128.5, 127.84, 127.79, 127.72, 127.5, 75.2, 62.4,
34.2, 31.5, 29.3, 27.2, 25.65, 25.62, 22.8, 22.6, 14.1; MS
364 [M]+; HRMS calcd for [C22H36O4] 364.2613; found
364.2621.
4.12. (4Z,7Z,10Z,13Z)-2-Phenyl-1,3-dioxan-5-yl nona-
deca-4,7,10,13-tetraenoate (20a)
To a cooled (À78 ꢁC), stirred solution of the phosphoni-
um salt 16 (200 mg, 442 lmol) in THF (5 mL) was add-
ed lithium hexamethyldisilazide (LiHMDS) (1 M THF
solution; 363 lL, 363 lmol) dropwise under an argon
atmosphere. After stirring at À78 ꢁC for 2 h, hexameth-
ylphosphoramide (HMPA) (0.5 mL) was added, the
reaction mixture was stirred for 10 min, and then alde-
hyde 19a (86 mg, 325 lmol) in THF (0.5 mL) was added
to the resulting red solution. The reaction mixture was
stirred at À78 ꢁC for 1 h and then allowed to warm
slowly to 0 ꢁC over a period of 1 h. It was then quenched
by the addition of 2 N HCl solution (1 mL) and extract-
ed with diethyl ether (3· 10 mL). The combined extracts
were washed with cold water (3· 5 mL), dried over
MgSO4, filtered, and concentrated under reduced pres-
sure to afford the crude product which was purified by
flash column chromatography (diethyl ether/hexane,
1:20, v/v) to give pure 20a (81 mg, yield 55%) as a color-
4.15. (6Z,9Z,12Z,15Z)-1,3-Dihydroxypropan-2-yl heni-
cosa-6,9,12,15-tetraenoate (5)
Compound 5 was prepared from 20b (70 mg, 145 lmol)
as described for 3. Purification with silica gel column
chromatography (hexane/ethyl acetate, 5:1, v/v) and bo-
rate-impregnated TLC gave 5 (25 mg, yield 44%) as a
1
colorless oil: H NMR (400 MHz, CDCl3) d 5.46–5.32
(m, 8 H), 4.93 (tt, 1H, J = 4.5, 4.5 Hz), 3.84 (dd, 4H,
J = 1.6, 4.5 Hz), 2.85–2.80 (m, 6H), 2.39 (t, 2H,
J = 7.5 Hz), 2.11–2.00 (m, 4H), 1.67 (tt, 2H, J = 7.3,
7.3 Hz), 1.60 (br s, 2H), 1.44–1.26 (m, 8H), 0.89 (br t,
3H, J = 6.8 Hz); 13C NMR (100 MHz, CDCl3) d 173.8,
130.5, 129.6, 128.6, 128.31, 128.26, 128.18, 127.9,
1
less oil: H NMR (400 MHz, CDCl3) d 7.52–7.50 (m,

Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
863
127.6, 75.1, 62.6, 34.2, 31.5, 29.3, 29.0, 27.2, 26.8, 25.7,
24.6, 22.6, 14.1; MS 392 [M]+; HRMS calcd for
[C4H40O4] 392.2927; found 392.2934.
(400 MHz, CDCl3) d 7.81–7.78 (m, 2H), 7.35–7.25 (m,
7H), 4.48 (br s, 2H), 4.01 (dd, 1H, J = 2.8, 9.5 Hz),
3.87 (dd, 1H, J = 7.0, 16.5 Hz), 3.85–3.80 (m, 1H),
3.45 (t, 2H, J = 6.4 Hz), 2.42 (br s, 3H), 2.27 (br s,
1H), 1.64–1.36 (m, 6H); 13C NMR (100 MHz, CDCl3)
d 129.9, 128.4, 127.9, 127.6, 127.5, 73.9, 72.9, 70.0,
69.3, 32.4, 29.4, 22.0, 21.6; MS 378 [M]+; HRMS calcd
for [C20H26O5S] 378.1501; found 378.1502.
4.16. 5-Hexenyloxymethylbenzene (22)
To a solution of 5-hexen-1-ol (21) (10 mL, 83 mmol) in
DMF (50 mL) were added sodium hydride (60% in oil
4.0 g, 100 mmol), benzyl bromide (14.9 g, 125 mmol),
and tetra-n-butylammonium iodide (3.1 g, 8.3 mmol) at
0 ꢁC under an argon atmosphere. The reaction mixture
was stirred at room temperature for 6 h, then diluted
with ethyl acetate (300 mL). The mixture was washed
with water (200 mL) and brine (200 mL), and the organ-
ic layer was dried over MgSO4 and evaporated in vacuo.
The residue was chromatographed on silica gel (hexane/
ethyl acetate, 40:1, v/v) to give 22 (15 g, yield 95%) as a
4.19. 6-Benzyloxy-2-(tert-butyldimethylsilanyloxy)hexyl
4-methylbenzenesulfonate (25)
To a 0ꢁC cooled solution of 24 (5.00 g, 13.2 mmol) in
DMF (50 mL) was added imidazole (1.98 g, 29.1 mmol)
followed by tert-butyldimethylsilyl chloride (TBSCl)
(3.99 g, 26.4 mmol) and stirred at room temperature
for 1 h. The reaction mixture was poured into water
(200 mL) and extracted with ethyl acetate (3· 100 mL).
The ethyl acetate layer was combined and washed with
brine (100 mL), dried over MgSO4, and filtered. The sol-
vent was evaporated under reduced pressure, and the
product was purified by flash column chromatography
(hexane/ethyl acetate, 20:1, v/v) to afford 25 (5.92 g,
yield 91%) as a colorless oil: 1H NMR (400 MHz,
CDCl3) d 7.79–7.75 (m, 2H), 7.34–7.24 (m, 7H), 4.46
(br s, 2H), 3.88–3.80 (m, 2H), 3.69–3.61 (m, 1H), 3.45–
3.36 (m, 2H), 2.42 (br s, 3H), 1.65–1.24 (m, 6H), 0.84
(s, 9H), 0.00 (s, 6H); 13C NMR (100 MHz, CDCl3) d
129.9, 129.8, 129.6, 128.3, 127.9, 127.6, 83.1, 72.9,
70.0, 33.8, 32.4, 29.4, 22.0, 21.4, À3.0, À3.6; MS 492
[M]+; HRMS calcd for [C26H40O5SiS] 492.2366; found
492.2369.
1
colorless oil: H NMR (400 MHz, CDCl3) d 7.36–7.22
(m, 5H), 5.85–5.75 (m, 1H), 5.02–4.92 (m, 2H), 4.49 (s,
2H), 3.47 (t, 2H, J = 6.4 Hz), 2.06 (dd, 2H, J = 7.2,
14.4 Hz), 1.67–1.60 (m, 2H), 1.51–1.43 (m, 2H); 13C
NMR (100 MHz, CDCl3) d 128.4, 127.7, 127.4, 114.5,
72.8, 72.1, 70.2, 33.5, 29.2, 25.5; MS 190 [M]+; HRMS
calcd for [C13H18O] 190.1357; found 190.1358.
4.17. 6-Benzyloxyhexane-1,2-diol (23)
Compound 22 (10.1 g, 53.1 mmol) was dissolved in
CH3CN/water (2:1, v/v) (100 mL), and then a 2%
OsO4 solution in water (5 mL) and 4-methylmorpholine
N-oxide (12.5 g, 0.11 mol) were added to the solution.
After the mixture was stirred at room temperature for
12 h, Na2SO3 (20 mL) was added. The mixture was stir-
red at room temperature for 30 min, then extracted with
ethyl acetate (3· 50 mL). The organic layer was com-
bined and washed with 1 N HCl (50 mL) and brine
(50 mL), dried over MgSO4, and evaporated in vacuo.
The crude residue was chromatographed on silica gel
(hexane/ethyl acetate, 1:1 to ethyl acetate only, v/v) to
afford 23 (8.57 g, yield 72%) as a colorless oil: 1H
NMR (400 MHz, CDCl3) d 7.34–7.25 (m, 5H), 4.49 (s,
2H), 3.68–3.62 (m, 1H), 3.57 (dd, 1H, J = 2.8,
11.2 Hz), 3.47 (t, 2H, J = 6.4 Hz), 3.37 (dd, 1H,
J = 7.6, 11.3 Hz), 3.03 (br s, 2H), 1.69–1.59 (m, 2H),
1.54–1.38 (m, 4H); 13C NMR (100 MHz, CDCl3) d
138.4, 128.3, 127.6, 127.5, 72.9, 72.0, 70.2, 66.6, 32.8,
29.5, 22.2; MS 224 [M]+; HRMS calcd for [C13H20O3]
224.1412; found 224.1415.
4.20. (6-Benzyloxy-1-iodohexan-2-yloxy) tert-butyldi-
methylsilane (26)
To a solution of 25 (3.20 g, 6.50 mmol) in dry acetone
(300 mL) was added lithium iodide (9.70 g, 64.7 mmol),
and the solution was refluxed for 14 h. The reaction mix-
ture was concentrated under reduced pressure, then the
residue was dissolved in ethyl acetate (300 mL). The eth-
yl acetate solution was washed with water (100 mL) and
brine (100 mL), dried over MgSO4, filtered, and concen-
trated under reduced pressure to afford the crude
product, which was purified by flash column chromatog-
raphy (hexane/ethyl acetate, 20:1, v/v) to give pure 26
(2.56 g, yield 88%) as a colorless oil: 1H NMR
(400 MHz, CDCl3) d 7.29–7.19 (m, 5H), 4.40 (s, 2H),
3.50–3.45 (m, 1H), 3.41 (t, 2H, J = 6.4 Hz), 3.12 (d,
2H, J = 5.2 Hz), 1.62–1.55 (m, 6H), 0.84 (s, 9H), 0.03
(s, 3H), 0.00 (s, 3H); 13C NMR (100 MHz, CDCl3) d
128.3, 127.6, 127.5, 72.9, 71.3, 70.2, 36.7, 29.7, 25.8,
21.7, 13.9, À4.4, À4.6; MS 448 [M]+; HRMS calcd for
[C19H33O2SiI] 448.1295; found 448.1299.
4.18. 6-(Benzyloxy)-2-hydroxyhexyl 4-methylbenzene-
sulfonate (24)
To a solution of 23 (11.4 g, 50.9 mmol) in pyridine
(50 mL) was added p-toluenesulfonyl chloride (TsCl)
(9.70 g, 50.9 mmol) at 0 ꢁC under an argon atmosphere.
The suspension was stirred at room temperature for
12 h. The reaction mixture was diluted with CH2Cl2
(300 mL) and successively washed with 100 ml of 1 N
HCl, water, saturated aqueous NaHCO3, and brine.
The organic layer was dried over MgSO4 followed by fil-
tration and evaporation in vacuo. The residue was chro-
matographed on silica gel (hexane/ethyl acetate, 3:1, v/v)
to give 24 (14.2 g, yield 74%) as a colorless oil: 1H NMR
4.21. Diethyl 2-[6-benzyloxy-2-(tert-butyldimethylsilanyl-
oxy)hexyl] malonate (27)
To a suspension of NaH (60% in oil; 0.99 g, 24.8 mmol)
in a mixture of dry THF and dry DMF (1:1, v/v,
100 mL), diethyl malonate (6.8 mL, 44.8 mmol) was
added dropwise at 0 ꢁC under an argon atmosphere.
After stirring at room temperature for 15 min, the iodide

864
Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
26 (10.1 g, 22.5 mmol) in THF (10 mL) was added drop-
wise at 0 ꢁC under an argon atmosphere and the mixture
was refluxed for 4 h. The reaction mixture was cooled to
room temperature, then diluted with saturated aqueous
NH4Cl (300 mL) and extracted with ethyl acetate
(3· 100 mL). The organic layer was combined, dried
over MgSO4, filtered, and concentrated under reduced
pressure to give the crude product, which was purified
by flash column chromatography over silica gel (hex-
ane/ethyl acetate, 10:1, v/v) to give the pure product
27 (9.50 g, yield 88%) as a colorless oil: 1H NMR
(400 MHz, CDCl3) d 7.31–7.22 (m, 5H), 4.46 (s, 2H),
4.20–4.10 (m, 4H), 3.68–3.65 (m, 1H), 3.51 (dd, 1H,
J = 5.3, 9.0 Hz), 3.43 (t, 2H, J = 6.5 Hz), 2.11–2.04 (m,
1H), 1.94–1.87 (m, 1H), 1.57 (tt, 2H, J = 6.4, 6.7 Hz),
1.48–1.35 (m, 4H), 1.231 (t, 3H, J = 7.2 Hz), 1.225 (t,
3H, J = 7.2 Hz), 0.84 (s, 9H), 0.00 (s, 6H); 13C NMR
(100 MHz, CDCl3) d 169.9, 169.5, 138.6, 128.3, 127.6,
127.4, 72.9, 70.3, 69.7, 61.3, 61.2, 48.3, 37.1, 35.6, 29.9,
25.8, 21.5, 18.0, 14.0, À4.35, À4.82; MS 480 [M]+;
HRMS calcd for [C26H44O6Si] 480.2908; found
480.2906.
crude product, which was purified by flash column chro-
matography (hexane/ethyl acetate, 10:1, v/v) to give pure
29 (1.95 g, yield 89%) as a colorless oil: 1H NMR
(400 MHz, CDCl3) d 9.72 (s, 1H), 4.17–4.11 (m, 4H),
3.70–3.66 (m, 1H), 3.49 (dd, 1H, J = 5.5, 8.8 Hz),
2.392 (t, 1H, J = 7.3 Hz), 2.387 (t, 1H, J = 7.3 Hz),
2.10–2.03 (m, 1H), 1.96–1.90 (m, 1H), 1.68–1.60 (m,
2H), 1.47–1.42 (m, 2H), 1.23 (t, 6H, J = 7.3 Hz), 0.84
(s, 9H), 0.00 (s, 6H); 13C NMR (100 MHz, CDCl3) d
202.1, 169.8, 169.4, 69.3, 61.4, 61.3, 48.2, 43.7, 36.5,
35.4, 25.8, 17.3, 14.0, À4.4, À4.9; MS 388 [M]+; HRMS
calcd for [C19H36O6Si] 388.2281; found 388.2276.
4.24. Diethyl (6Z,9Z,12Z,15Z)-2-[2-(tert-butyldimethyl-
silanyloxy)henicosa-6,9,12,15-tetraenyl] malonate (30)
To a cooled (À78 ꢁC), stirred solution of the phosphoni-
um salt 16 (3.0 g, 5.48 mmol) in THF (30 mL) was add-
ed lithium hexamethyldisilazide (1 M THF solution;
5.46 mL, 5.46 mmol) dropwise under an argon atmo-
sphere. After stirring at À78 ꢁC for 2 h, HMPA (3 mL)
was added, the reaction mixture was stirred for
10 min, and then aldehyde 29 (1.90 g, 4.89 mmol) in
THF (6 mL) was added to the resulting red solution.
The reaction mixture was stirred at À78 ꢁC for 1 h and
then allowed to warm slowly to 0 ꢁC over a period of
1 h. It was then quenched by the addition of a 2 N
HCl solution (2 mL) and extracted with diethyl ether
(3· 50 mL). The combined extracts were washed with
cold water (3· 25 mL), dried over MgSO4, filtered, and
concentrated under reduced pressure to afford the crude
product, which was purified by flash column chromatog-
raphy (diethyl ether/hexane, 1:20, v/v) to give pure 30
(1.95 g, yield 69%) as a colorless oil: 1H NMR
(400 MHz, CDCl3) d 5.38–5.29 (m, 8H), 4.17–4.12 (m,
4H), 3.66 (tt, 1H, J = 3.9, 4.2 Hz), 3.51 (dd, 1H,
J = 5.1, 8.8 Hz), 2.84–2.76 (m, 6H), 2.10–1.87 (m, 6H),
1.47–1.17 (m, 16H), 0.85 (br s, 12H), 0.00 (br s, 6H);
13C NMR (100 MHz, CDCl3) d 169.9, 169.5, 130.4,
129.9, 128.5, 128.3, 128.1, 127.9, 127.5, 69.7, 61.3,
61.2, 48.3, 36.9, 35.6, 31.5, 29.3, 27.2, 25.8, 25.6, 24.7,
22.5, 18.0, 14.0, À4.3, À4.8; MS 576 [M]+; HRMS calcd
for [C34H60O5Si] 576.4210; found 576.4202.
4.22. Diethyl 2-[2-(tert-butyldimethylsilanyloxy)-6-
hydroxyhexyl] malonate (28)
To a solution of 27 (9.5 g, 19.8 mmol) in ethanol
(100 mL) was added 10% Pd/C (2 g) under an argon
atmosphere at room temperature. Hydrogenation was
performed at atmospheric pressure at room temperature
for 12 h. The solution was filtered to remove the cata-
lyst, and the filtrate was then evaporated at reduced
pressure. Silica gel column chromatography (hexane/
ethyl acetate, 10:1, v/v) gave 28 (7.49 g, yield 97%) as
a colorless oil: 1H NMR (400 MHz, CDCl3) d 4.19–
4.11 (m, 4H), 3.70–3.64 (m, 1H), 3.60 (t, 2H,
J = 6.5 Hz), 3.52 (dd, 1H, J = 5.2, 9.1 Hz), 2.11–2.04
(m, 1H), 1.94–1.87 (m, 1H), 1.67 (br s, 1H), 1.56–1.31
(m, 6H), 1.230 (t, 3H, J = 7.2 Hz), 1.228 (t, 3H,
J = 7.3 Hz), 0.85 (s, 9H), 0.00 (s, 6H); 13C NMR
(100 MHz, CDCl3) d 169.9, 169.5, 69.7, 62.6, 61.3,
61.2, 48.3, 37.0, 35.4, 32.7, 25.8, 20.9, 18.0, 14.0, À4.4,
À4.9; MS 333 [MÀt-Bu]+; HRMS calcd for
[C15H29O6Si] 333.1734; found 333.1741.
4.25. (6Z,9Z,12Z,15Z)-2-[2-(tert-Butyldimethylsilanyl-
oxy)henicosa-6,9,12,15-tetraenyl]propane-1,3-diol (31)
4.23. Diethyl 2-[2-(tert-butyldimethylsilanyloxy)-6-oxo-
hexyl] malonate (29)
To a solution of compound 30 (1.65 g, 493 mmol) in dry
diethyl ether (50 mL) was added dropwise LiAlH4
(435 mg) in dry diethyl ether at 0 ꢁC under an argon
atmosphere. The reaction mixture was stirred at room
temperature for 1 h. Ethyl acetate (0.5 mL) was then
added dropwise to the mixture to quench excess LiAlH4
at 0 ꢁC. The mixture was diluted with ethyl acetate
(100 mL), then filtered through a pad of silica gel. The
filtrate was successively washed with 50 mL of water
and brine. The organic layer was dried (MgSO4) and
concentrated in vacuo. The crude residue was chromato-
graphed on silica gel (hexane/ethyl acetate, 5:1, v/v) to
To a cooled (À78 ꢁC) solution of oxalyl chloride
(984 lL, 11.3 mmol) in dry CH2Cl2 (100 mL) was added
dimethylsulfoxide (1.20 mL, 16.9 mmol) in dry CH2Cl2
(10 mL) and stirred at this temperature for 10 min. A
solution of 28 (2.20 g, 5.64 mmol) in CH2Cl2 (10 mL)
was slowly added to the cooled solution for 5 min. After
the addition was completed, the reaction mixture was
stirred at À78 ꢁC for 15 min and then at À48 ꢁC for
45 min. Triethylamine (5.50 mL, 39.5 mmol) was added
and the mixture was stirred at 0 ꢁC for 20 min. The
resulting solution was quenched by being poured into
saturated aqueous NH4Cl (100 mL) and extracted with
ethyl acetate (3· 100 mL). The combined extracts were
washed with brine (100 mL), dried over MgSO4, filtered,
and concentrated under reduced pressure to afford the
1
give 31 (1.14 g, yield 81%) as a colorless oil: H NMR
(400 MHz, CDCl3) d 5.36–5.23 (m, 8H), 3.73 (tt, 1H,
J = 4.6, 6.1 Hz), 3.61–3.51 (m, 4H), 2.78–2.72 (m, 6H),
2.00–1.95 (m, 5H), 1.91–1.83 (m, 1H), 1.52–1.18 (m,

Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
865
13H), 0.82 (br s, 12H), 0.00 (br s, 6H); 13C NMR
(100 MHz, CDCl3) d 130.5, 129.9, 128.6, 128.3, 128.1,
127.9, 127.6, 71.0, 66.7, 65.9, 38.9, 36.5, 35.4, 31.5,
29.3, 27.3, 27.2, 25.9, 25.6, 25.4, 22.6, 18.1, 14.1, À4.4,
À4.5; MS 492 [M]+; HRMS calcd for [C30H56O3Si]
492.3999; found 492.3997.
gel (hexane/ethyl acetate, 40:1, v/v) to give 33 (319 mg,
yield 74%) as a colorless oil: 1H NMR (400 MHz,
CDCl3) d 5.43–5.31 (m, 8H), 3.71 (dd, 2H, J = 5.8,
9.8 Hz), 3.65 (dd, 2H, J = 5.5, 9.8 Hz), 2.85–2.76 (m,
6H), 2.49 (d, 2H, J = 6.4 Hz), 2.43 (t, 2H, J = 7.6 Hz),
2.28 (dt, 1H, J = 5.8, 6.4 Hz), 2.10–2.01 (m, 4H), 1.64
(dt, 2H, J = 7.6, 7.6 Hz), 1.40–1.26 (m, 6H), 1.12–0.96
(m, 6H), 1.04 (br s, 36H), 0.89 (t, 3H, J = 6.8 Hz); 13C
NMR (100 MHz, CDCl3) d 130.5, 129.3, 128.6, 128.23,
128.17, 127.9, 127.5, 63.2, 42.7, 41.0, 40.0, 31.5, 30.9,
29.3, 27.2, 26.6, 25.6, 23.7, 22.6, 18.0, 14.1, 12.0; MS
688 [M]+; HRMS calcd for [C42H80O3Si2] 688.5646;
found 688.5646.
4.26. (8Z,11Z,14Z,17Z)-2-(Hydroxymethyl)tricosa-
8,11,14,17-tetraene-1,4-diol (6)
TBAF (1 M THF solution; 4.30 mL) was added drop-
wise to the solution of ethyl ester 31 (1.06 g, 2.15 mmol)
in THF (20 mL) at 0 ꢁC under an argon atmosphere.
The reaction mixture was warmed to room temperature
and stirred for 1 h. Removal of the solvent and chroma-
tography on silica gel (hexane/ethyl acetate, 1:1, v/v) of
the residue gave 6 (586 mg, yield 72%) as a colorless oil:
1H NMR (400 MHz, CDCl3–D2O) d 5.41–5.33 (m, 8 H),
3.77–3.63 (m, 5H), 2.85–2.78 (m, 6H), 2.07 (dt, 4H,
J = 7.0, 7.0 Hz), 1.95 (dt, 1H, J = 5.8, 5.8 Hz), 1.74–
1.67 (m, 2H), 1.60–1.22 (m, 10H), 0.89 (t, 3H,
J = 6.7 Hz); 13C NMR (100 MHz, CDCl3) d 130.5,
129.8, 128.6, 128.3, 128.2, 128.1, 127.9, 127.5, 70.2,
65.6, 65.3, 40.5, 37.8, 36.7, 31.5, 29.3, 27.2, 27.1, 25.7,
25.6, 25.5, 22.5, 14.0; MS 378 [M]+; HREIMS calcd
for [C24H42O3] 378.3134; found 378.3134.
4.29. (8Z,11Z,14Z,17Z)-1-Hydroxy-2-(hydroxymeth-
yl)tricosa-8,11, 14,17-tetraen-4-one (7)
TBAF (1 M THF solution; 777 lL, 777 lmol) was add-
ed dropwise to a solution of silyl ether 33 (228 mg,
331 lmol) in THF (10 mL) at 0 ꢁC under an argon
atmosphere. The reaction mixture was warmed to room
temperature and stirred for 1 h. Removal of the solvent
and chromatography on silica gel (hexane/ethyl acetate,
1:1, v/v) of the residue gave 7 (90 mg, yield 76%) as a
colorless oil: 1H NMR (400 MHz, CDCl3–D2O) d
5.42–5.32 (m, 8H), 3.74 (dd, 2H, J = 4.8, 10.8 Hz),
3.68 (dd, 2H, J = 5.7, 10.8 Hz), 2.85–2.79 (m, 6H),
2.57 (d, 2H, J = 6.7 Hz), 2.47 (t, 2H, J = 7.3 Hz), 2.29
(ddd, 1H, J = 4.8, 5.8, 6.7 Hz), 2.12–1.99 (m, 4H), 1.66
(dt, 2H, J = 7.3, 7.3 Hz), 1.40–1.25 (m, 6H), 0.89 (t,
3H, J = 6.8 Hz); 13C NMR (100 MHz, CDCl3) d 210.9,
130.5, 129.1, 128.8, 128.6, 128.3, 128.2, 127.9, 127.6,
65.1, 42.7, 41.5, 38.3, 31.5, 29.3, 27.2, 26.5, 25.7, 23.6,
22.6, 14.1; MS 358 [MÀH2O]+; HREIMS calcd for
[C24H38O2] 358.2872; found 358.2867.
4.27. (8Z,11Z,14Z,17Z)-1-(Triisopropylsilanyloxy)-2-
(triisopropylsilanyloxymethyl)tricosa-8,11,14,17-tetraen-
4-ol (32)
The triol 6 (500 mg, 1.32 mmol) was dissolved in DMF
(10 mL) containing imidazole (297 mg, 4.36 mmol) and
cooled to 0 ꢁC under an argon atmosphere. Triisopropyl-
silyl chloride (TIPSCl) (764 mg, 3.96 mmol) in DMF
(5 mL) was added and the reaction mixture was stirred
at room temperature for 1 h. The mixture was diluted
with ethyl acetate (50 mL), then washed with water
(30 mL) and brine (30 mL). The organic layer was dried
over MgSO4, filtered, and concentrated in vacuo. Chro-
matography on silica gel (hexane/ethyl acetate, 40:1, v/v)
4.30. 6-(tert-Butyldimethylsilanyloxy)hexan-1-ol (34)
Compound 34 was prepared from 1,6-hexanediol by a
reported method.26
1
gave 32 (548 mg, yield 60%) as a colorless oil: H NMR
4.31. tert-Butyl(6-iodohexyloxy)dimethylsilane (35)
(400 MHz, CDCl3) d 5.41–5.32 (m, 8H), 3.80 (dd, 2H,
J = 5.8, 9.8 Hz), 3.72 (dd, 2H, J = 5.8, 9.8 Hz), 3.60 (tt,
1H, J = 6.1, 6.4 Hz), 2.85–2.80 (m, 6H), 2.11–2.03 (m,
4H), 1.96 (dt, 1H, J = 6.1, 6.4 Hz), 1.57–1.26 (m, 13H),
1.13–1.01 (m, 6H), 1.07 (br s, 36H), 0.89 (t, 3H,
J = 6.9 Hz); 13C NMR (100 MHz, CDCl3) d 130.5,
130.3, 128.52, 128.48, 128.01, 127.96, 127.7, 127.6,
69.98, 65.7, 65.3, 42.5, 38.8, 37.4, 31.5, 29.3, 27.3, 27.2,
25.9, 25.6, 22.6, 18.0, 14.1, 11.9; MS 691 [M]+; HRMS
calcd for [C42H82O3Si2] 690.5803; found 690.5803.
To a solution of 34 (119 mg, 513 lmol) in dry DMF
(10 mL) was added methyltriphenoxyphosphonium io-
dide (387 mg, 956 lmol). The mixture was stirred at
room temperature for 20 min under an argon
atmosphere. The crude product was purified by flash
column chromatography (hexane/ethyl acetate, 20:1,
v/v) to afford 35 (120 mg, yield 82%) as a colorless oil:
1H NMR (400 MHz, CDCl3)
d
3.55 (t, 2H,
J = 6.8 Hz), 3.15 (t, 2H, J = 7.2 Hz), 1.82–1.75 (m,
2H), 1.49–1.47 (m, 2H), 1.40–1.30 (m, 4H), 0.85 (s,
9H), 0.01 (s, 6H); 13C NMR (100 MHz, CDCl3) d
63.2, 32.7, 28.9, 25.8, 25.5, 18.3, 6.5, À5.4; MS 285
[MÀt-Bu]+; HREIMS calcd for [C8H18OISi] 285.0172;
found 285.0172.
4.28. (8Z,11Z,14Z,17Z)-1-(Triisopropylsilanyloxy)-2-
(triisopropylsilanyloxymethyl)tricosa-8,11,14,17-tetraen-
4-one (33)
PDC (503 mg, 1.34 mmol) in CH2Cl2 (10 mL) was add-
ed to alcohol 32 (433 mg, 627 lmol) containing molecu-
lar sieves 4A in CH2Cl2 (30 mL) at 0 ꢁC under an argon
atmosphere. The reaction mixture was stirred at room
temperature for 20 h and then concentrated with silica
gel (10 g). The residue was chromatographed on silica
4.32. Diethyl 2-[6-(tert-butyldimethylsilanyloxy)hexyl]
malonate (36)
The compound 35 (70 mg, 246 lmol) was converted to
dicarboxylate 36 (69 mg) according to the procedure

866
Y. Suhara et al. / Bioorg. Med. Chem. 15 (2007) 854–867
described above for obtaining 27 from 26 in 75% yield
as a colorless oil. H NMR (400 MHz, CDCl3) d 4.15
aliquots (1 lL each) were added to the cuvette (final
concentration of dimethylsulfoxide: 0.2%).
1
(dd, 4H, J = 7.2, 14.4 Hz), 3.54 (t, 2H, J = 6.4 Hz),
3.27 (t, 1H, J= 7.6 Hz), 1.84 (dd, 2H, J = 7.6,
14.8 Hz), 1.46 (t, 2H, J = 6.4 Hz), 1.26–1.25 (m, 6H),
1.22 (t, 6H, J = 7.2 Hz), 0.81 (s, 9H), 0.01 (s, 6H); 13C
NMR (100 MHz, CDCl3) d 169.5, 63.1, 61.2, 52.0,
32.7, 29.0, 28.6, 27.3, 25.9, 25.5, 18.3, 14.0, À5.4; MS
374 [M]+; HREIMS calcd for [C19H38O5Si] 374.2489;
found 374.2468.
Acknowledgments
We are grateful to Junko Shimode and Maroka Kitsuk-
awa for the spectroscopic measurements. This study was
supported in part by a Grant-in-Aid from the Ministry
of Education, Culture, Sports, Science and Technology,
the Japanese Government.
4.33. Diethyl 2-(6-hydroxyhexyl)malonate (37)
To a solution of 36 (494 mg, 1.32 mmol) in THF was
added 1.0 M TBAF in THF. The mixture was stirred
at room temperature for 1 h. It was then concentrated
in vacuo and the crude product was purified by flash col-
umn chromatography (hexane/ethyl acetate, 2:1, v/v) to
afford 37 (120 mg, yield 35%) as a colorless oil: 1H NMR
(400 MHz, CDCl3) d 4.19 (dd, 4H, J = 7.2, 14.4 Hz),
3.62 (t, 2H, J = 6.8 Hz), 3.31 (t, 1H, J = 7.6 Hz), 2.18
(s, 1H), 1.90 (dd, 2H, J = 7.6, 14.8 Hz), 1.56 (t, 2H,
J = 6.8 Hz), 1.38–1.31 (m, 6H), 1.28 (t, 6H, J = 7.2
Hz); 13C NMR (100 MHz, CDCl3) d 169.5, 62.7, 61.2,
53.8, 52.0, 32.5, 31.6, 29.2, 28.9, 28.6, 27.2, 25.4, 14.0;
MS 260 [M]+; HREIMS calcd for [C13H24O5]
260.1624; found 260.1622.
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