The synthesis of N-vanillyl-arachidonoyl-amide (arvanil) and its analogs: An improved procedure for the synthesis of the key synthon methyl 14-hydroxy-(all-cis)-5,8,11-tetradecatrienoate

Article abstract of DOI:10.1016/S0040-4020(00)00877-2

Several arvanil analogs were synthesized where the end n-pentyl chain was branched and carried substituents at the terminal end of the chain. A high yielding total synthesis of these analogs was developed from methyl hex-5-ynoate, which was converted to t

Full text of DOI:10.1016/S0040-4020(00)00877-2

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 9195±9202
The Synthesis of N-Vanillyl-arachidonoyl-amide (Arvanil) and its
Analogs: An Improved Procedure for the Synthesis of the Key
Synthon Methyl 14-Hydroxy-(all-cis)-5,8,11-tetradecatrienoate
Olivier Dasse,a Anu Mahadevan,a Luning Han,a Billy R. Martin,b Vincenzo Di Marzoc
and Raj K. Razdana,
*
aOrganix Inc., 240 Salem Street, Woburn, MA 01801, USA
bDepartment of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA 23298, USA
cIstituto per la Chimica di Molecole di Intresse Biologico, C.N.R. Via Toiano 6, 80072 Arco Felice, Napoli, Italy
Received 7 August 2000; accepted 21 September 2000
AbstractÐSeveral arvanil analogs were synthesized where the end n-pentyl chain was branched and carried substituents at the terminal end
of the chain. A high yielding total synthesis of these analogs was developed from methyl hex-5-ynoate, which was converted to the synthon 6
in a facile ®ve step sequence (overall yield, 33%). The pharmacological pro®le of these novel analogs suggests that they may be acting
through a novel site of action for anandamide (arachidonylethanolamide, AEA). q 2000 Elsevier Science Ltd. All rights reserved.
Introduction
from macrophages in the spleen, canine gut and pancreas
and it has been shown that 2-arachidonyl glycerol (2-Ara-
Gl) acts at this receptor.8c,11±13 It has since been found in the
brain and binds to both CB1 and CB2 receptors.13 Like
AEA, 2-Ara-Gl is found together with a family of related
fatty acid glycerol esters. Furthermore, the potency of
2-Ara-Gl was increased in various tests in the presence of
these related 2-acyl-glycerols which when tested alone do
not show any signi®cant activity. This effect8c has been
referred to as the `entourage effect' which may represent a
route for molecular regulation of endogenous cannabinoid
activity. In summary both AEA and 2-Ara-Gl interact with
the cannabinoid receptors, in the brain as well as the peri-
phery, to produce a myriad of pharmacological effects.
Since the discovery of anandamide (arachidonylethanol-
amide, AEA) as one of the endogenous ligands which
bind to the G-protein coupled receptor (CB1) for canna-
binoids, some progress has been made in understanding
their mechanism of action. It appears that a family of fatty
acid derivatives interacts in different degrees with the
cannabinoid receptors.1±8 AEA exhibits cannabimimetic
effects similar to those of D9-tetrahydrocannabinol (D9-
THC), the active constituent of marijuana but there are
some pharmacological differences between AEA and D9-
THC, for example the onset of action of AEA is faster
than that of D9-THC but the duration of action is much
shorter.4 This is attributed to the rapid enzymatic hydrolysis
of the amide bond in AEA by amidases.9 However, several
analogs of AEA have been developed which are metabolic-
ally stable and have much greater binding af®nities than
AEA. Their pharmacological activity has substantiated the
similarities between D9-THC and AEA.8 It is noteworthy,
that several other fatty acid ethanolamides besides AEA are
present in the brain, two of which, gamma-linolenyl
ethanolamide and docosatetraenyl ethanolamide have
comparable binding af®nities to AEA but the others do
not bind to the CB1 receptor.10 Another peripherally
expressed cannabinoid receptor subtype CB2 was identi®ed
In an effort to further examine the interactions of cannabi-
noid receptors (endocannabinoids) with other receptors in
the brain, Di Marzo et al. reported on the interactions with
vanilloid receptors which are present in sensory neurons14
and some peripheral tissues.15 Capsaicin [N-(3-methoxy-4-
hydroxy)-benzyl-8-methyl-6-trans-nonenamide] which is
the pungent ingredient of chili pepper exerts its vasodila-
tory, analgesic and anti-in¯ammatory properties by activat-
ing the vanilloid receptor (VR1).15,16 Another fatty acyl
chain analog of capsaicin called olvanil, [N-(3-methoxy-4-
hydroxy)-benzyl-cis-9-octadecenoamide] was also found to
exhibit vasodilatory, analgesic and anti-in¯ammatory prop-
erties but to a lesser extent than capsaicin.17±19 Based on the
differences in their pharmacological behavior it was postu-
lated that this synthetic analog might be activating a differ-
ent vanilloid receptor subtype.19
Keywords: cannabinoid receptor; vanilloid receptors; anandamide; arvanil
analogs.
* Corresponding author. Tel.: 11-781-932-4142; fax: 11-781-933-6695;
e-mail: razdan@organixinc.com
0040±4020/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(00)00877-2

9196
O. Dasse et al. / Tetrahedron 56 (2000) 9195±9202
Figure 1. Structures of anandamide, arvanil, capsaicin and olvanil.
Di Marzo et al. reported14 that olvanil is a potent inhibitor of
AEA facilitated transport, blocking the uptake but not the
hydrolysis of AEA. Olvanil was also found to be a weak
agonist of CB1, but not CB2 receptors. Further modi®cation
of olvanil, by Di Marzo et al. led to the development of
arvanil (N-Vanillyl-arachidonyl-amide)20 (Fig. 1). Arvanil
is a unique vanilloid/cannabinoid hybrid, which is meta-
bolically stable, a novel ligand of vanilloid receptors and
cannabinoid CB1, but not CB2, receptors and it inhibits the
uptake of the proposed endogenous ligand of CB1 receptor,
AEA. It was proposed that this compound may have thera-
peutic potential for use as analgesics, vasodilators, and anti-
in¯ammatory or anti-tumor agents, and due to its interaction
with the endogenous cannabinoid system may lead to
novel class of cannabinoids with potential therapeutic
applications.14,20
compounds 10, 13, 22 and 23 had Ki'sˆ262, 790, 33 and
67 nM, respectively. The CB1 binding af®nity of AEA was
89 nM22 and arvanil was reported to be almost 4-fold more
potent than AEA in the displacement of [3H]SR 141716A
from membrane preparations from N18TG2 cells.20
However, in in vivo potency (tetrad tests)22 the arvanil
dimethylheptyl analog 10 (arvanil DMH) was very potent
(,100-fold more potent than AEA), and was equiactive
with arvanil but its binding af®nity to CB1 receptors
was one third that of AEA. Analog 22 was more potent
than arvanil whereas analogs 13 and 23 were less active
than arvanil. Their in vivo potency was much greater than
what would be expected based on their binding af®nity and
ef®cacy at CB1 and VR1 receptors, thus suggesting that they
may be acting through a novel site of action for AEA. The
details of their pharmacological evaluation will be
published elsewhere.
In order to optimize the activity of arvanil, we synthesized
analogs 10, 13, 22 and 23 where the end n-pentyl chain in
arvanil was branched and carried substituents at the terminal
end of the chain. Similar structural changes in THCs and
AEA series have led to analogs with potent cannabimimetic
activity.21±23
This series of arvanil analogs is important as it may lead to a
novel class of cannabimimetics with potential therapeutic
applications, and in this paper the details of the synthetic
route to these analogs are described.
The biological evaluation of analogs 10, 13, 22 and 23 was
carried out and in summary they exhibit a pharmacological
pro®le that is more similar to AEA than capsaicin. In bind-
ing studies,8c,22 in the displacement of [3H]CP 55,940
from rat whole brain P2 membrane preparations (CB1),
Results
In the synthesis of the arvanil analogs the alcohol, methyl 14-
hydroxy-(all-cis)-5,8,11-tetradecatrienoate 6, was the key
intermediate (Scheme 1). In general our strategy involves
Scheme 1.

O. Dasse et al. / Tetrahedron 56 (2000) 9195±9202
9197
Scheme 2.
conversion of 6 to the corresponding phosphonium iodide
(Scheme 2), the ylide of which was treated with the desired
aldehyde in a Wittig reaction, to give the required ester.
Hydrolysis of the ester followed by treatment with oxalyl
chloride and vanillylamine gave the desired arvanil analogs.
CuI as a catalyst to give 10-hydroxy-deca-5,8-diynoic acid
methyl ester 3. Bromination with CBr4/Ph3P gave the
propargylic bromide which was then coupled with but-3-yn-
1-ol in the presence of CuI as a catalyst to provide the triynoic
acid methyl ester 5.27 Partial reduction of the triyne 5 over
`nickel boride' catalyst provided the key intermediate 6.28
Several procedures have been reported for the synthesis of
the alcohol 6 from arachidonic acid.24 Our previously
reported synthesis of this synthon was a 11 step sequence
(overall yield, 14%),25 but here we report a much more
¯exible and shorter route to 6, a ®ve step sequence (overall
yield, 33%), which allows us to ef®ciently synthesize differ-
ent AEA derivatives.
Alcohol 6 was converted to the iodide quantitatively by
treatment with triphenyl phosphine/I2.29 The iodide was
then converted to the corresponding phosphonium iodide
7 by re¯uxing with triphenyl phosphine. Treatment of the
phosphonium iodide 7 with NaHMDS converted it into the
ylide which was then allowed to react with the aldehyde 8
(which we had previously synthesized from ethyl isobuty-
rate)22 in a Wittig reaction to give the ester derivative 9.22
Hydrolysis of the ester 9 with LiOH followed by treatment
with oxalyl chloride22 and vanillylamine formed the target
analog 10 (Scheme 2). Similarly, the ylide of 7 on treatment
with aldehyde 11 gave the ester derivative 12 (Scheme 3).
Methyl 14-hydroxy-(all-cis)-5,8,11-tetradecatrienoate
6
was synthesized (Scheme 1) starting from hex-5-ynoic
acid which was converted into its methyl ester 1 by treat-
ment with p-TSA in MeOH. The ester 1 was then coupled
with the known 4-chloro-but-2-yn-1-ol 226 in the presence of
Scheme 3.

9198
O. Dasse et al. / Tetrahedron 56 (2000) 9195±9202
Scheme 4.
The synthesis of the aldehyde 11 was achieved following a
modi®cation of the sequence we developed for the synthesis
of 8 (Scheme 4) from ethyl isobutyrate (14)22 by alkylation
with 4-bromobut-1-ene (15) to give 16. Hydroboration of
the ester 16 formed 17,30 the hydroxyl group of which was
protected as the THP derivative 18.31 Reduction of the
carboxyester group32 in 18 with LAH formed the alcohol
19 which was oxidized with PCC33 to the desired aldehyde
11 in an overall yield of 50%.
treatment with Ph3P/Br2.34 The bromide 20 was then trans-
formed into the cyano derivative 21 by treatment with
KCN.35 Hydrolysis of the esters 20 and 21 with LiOH
followed by treatment with oxalyl chloride and vanillyla-
mine formed the target analogs 22 and 23, respectively.
In summary, we have developed a facile ®ve step sequence
for the synthesis of the key synthon, methyl 14-hydroxy-
(all-cis)-5,8,11-tetradecatrienoate (6) from commercially
available hex-5-ynoic acid (overall yield, 33%). This
synthon (6) was used to synthesize novel arvanil analogs
which are important for the study of `endocannabinoids'
and may lead to a novel class of cannabinoids with poten-
tial therapeutic use. It is noteworthy that synthon 6 could
also provide an entry to the synthesis of novel analogs in
other ®elds where arachidonic acid plays an important
role.
Hydrolysis of the ester 12 (Scheme 3) with LiOH followed
by coupling with vanillylamine in the presence of 1-ethyl-
3-[3-(dimethylamino)propyl]carbodiimide hydrochloride
(EDCI) formed the target analog 13.22 Interestingly the
THP protecting group was also removed during this
coupling reaction. Ester derivative 12 was converted into
the corresponding bromo derivative 20 (Scheme 5) by
Scheme 5.

O. Dasse et al. / Tetrahedron 56 (2000) 9195±9202
9199
Experimental
CBr4 (17.74 g, 53.5 mmol) in CH2Cl2 (80 mL) cooled to
2208C, a solution of triphenylphosphine (14.6 g, 55.7
mmol) in CH2Cl2 (40 mL) was added dropwise. After the
addition the cooling bath was removed and the mixture was
stirred for an additional 1 h. Hexanes/ethyl acetate (4/1) was
then added until triphenylphosphine oxide precipitated. The
mixture was plugged through a pad of silica gel to yield
methyl 10-bromo-deca-5,8-diynoate as a colorless oil
(10.54 g, 92%). Attempts to further purify it by ¯ash
chromatography resulted in partial decomposition of the
bromide. Hence, it was used as such in the subsequent reac-
All reagents were of commercial quality, reagent grade, and
used without further puri®cation. Anhydrous solvents were
purchased from Aldrich and used without further puri®-
cation. All reactions were carried out under N2 atmosphere.
1H NMR spectra were recorded on a JEOL Eclipse 300
spectrophotometer using CDCl3 as the solvent with tetra-
methylsilane as an internal standard. Thin-layer chroma-
tography (TLC) was carried out on Baker Si 250F plates
and was developed upon treatment with phosphomolybdic
acid (PMA). Flash column chromatography was carried out
on EM Science silica gel 60. Elemental analyses were
performed by Atlantic Microlab, Inc., Atlanta, GA, and
were found to be within ^0.4% of calculated values for
the elements shown, unless otherwise noted.
1
tion. H NMR d 1.81 (quint, 2H, Jˆ7.1 Hz), 2.23 (tt, 2H,
Jˆ7.1, 2.5 Hz), 2.43 (t, 2H, Jˆ7.1 Hz), 3.20 (quint, 2H,
Jˆ2.5 Hz), 3.67 (s, 3H), 3.90 (t, 2H, Jˆ2.5 Hz).
A mixture of K2CO3 (9.67 g, 70 mmol), CuI (6.66 g,
35 mmol), but-3-yn-1-ol (4; 5.3 mL, 70 mmol), NaI
(10.50 g, 70 mmol) and methyl 10-bromo-deca-5,8-diyno-
ate (17.99 g, 70 mmol) in DMF (140 mL) was stirred over-
night at 258C. The mixture was diluted with ethyl acetate
and plugged through a pad of celite. It was washed with
saturated NH4Cl followed by brine. The solution was
dried over MgSO4 and the solvent was evaporated under
vacuum. The oily residue was dissolved in hexanes/ethyl
acetate (1/1) and plugged through a pad of silica gel to
provide compound 5 as a yellowish oil (14.63 g, 85%)
which was used in the subsequent step without further puri-
®cation. Attempts to purify by ¯ash chromatography
Methyl hex-5-ynoate-1. A stirred solution of hex-5-ynoic
acid (5 g, 44.6 mmol), p-TSA (58 mg, 0.3 mmol) in MeOH
(8 mL) and CH2Cl2 (17 mL) was re¯uxed for 24 h. The
mixture was quenched with saturated NaHCO3 and the
organic layer was separated. The aqueous layer was
extracted with CH2Cl2. The combined organic layers were
dried over MgSO4 and evaporated under reduced pressure to
yield the methyl ester (5.46 g, 97%). 1H NMR d 1.84 (quint,
2H, Jˆ7.2 Hz), 1.96 (t, 1H, Jˆ2.75 Hz), 2.25 (dt, 2H,
Jˆ7.2, 2.75 Hz), 2.45 (t, 2H, Jˆ7.2 Hz), 3.67 (s, 3H).
1
4-Chloro-but-2-yn-1-ol 2.26 To a stirred solution of but-2-
yn-1,4-diol (86 g, 1 mol) and pyridine (89 mL, 1.1 mol) in
benzene (100 mL) was added thionyl chloride (80.23 mL,
1.1 mol) dropwise over a period of 6 h, while the tempera-
ture was maintained between 10±208C. The reaction
mixture was then stirred overnight at 258C. The mixture
was poured into ice water (250 mL) and the benzene layer
was separated. The aqueous layer was extracted with ether
(4£100 mL) and the combined organic layers were washed
with saturated NaHCO3, followed by water. The ether
extract was dried over MgSO4 and the solvent was removed
under vacuum. Puri®cation of the residual oil by distillation
(808C, 5 mmHg) provided the title compound as a colorless
resulted in partial decomposition of the triyne. H NMR d
1.80 (quint, 2H, Jˆ6.7 Hz), 2.23 (tt, 2H, Jˆ6.9, 2.2 Hz),
2.42 (t, 2H, Jˆ7.1 Hz), 2.42±2.48 (m, 2H), 3.14 (dq, 4H,
Jˆ6.3, 2 Hz), 3.67 (s, 3H), 3.69 (t, 2H, Jˆ6 Hz).
14-Hydroxy-tetradeca-all-cis-5,8,11-trienoic acid methyl
ester 6.28 To a stirred solution of Ni(OAc)2 (14.93 g,
60 mmol) in EtOH (450 mL) was added ethylenediamine
(4 mL, 60 mmol) followed by a 1 M solution of NaBH4
(60 mL). The mixture was stirred at 258C for 0.5 h. The
triyne 5 (6.6 g, 26.8 mmol) was added to the reaction
mixture and a H2 atmosphere (balloon) was kept over the
reaction mixture. It was stirred for 3 h at 258C and
the solvent was removed in vacuo. The residue was
dissolved in hexanes/ethyl acetate (1/1) and plugged
through a pad of silica gel. Puri®cation by ¯ash chroma-
tography (eluting with hexanes/ethyl acetate 2/1) provided
the desired triene 6 as a colorless oil (3.38 g, 50%). 1H NMR
d 1.70 (quint, 2H, Jˆ7.1 Hz), 1.98±2.14 (m, 2H), 2.27±
2.39 (m, 2H), 2.32 (t, 2H, Jˆ7.1 Hz), 2.79 (dd, 2H,
Jˆ5.2, 5.2 Hz), 2.84 (dd, 2H, Jˆ14.0, 5.8 Hz), 3.65 (t, 2H,
Jˆ6.6 Hz), 3.66 (s, 3H), 5.29±5.58 (m, 6H).
1
liquid (34.5 g, 33%). H NMR d 4.18 (t, 2H, Jˆ1.9 Hz),
4.33 (dt, 2H, Jˆ6.3, 1.9 Hz).
10-Hydroxy-deca-5,8-diynoic acid methyl ester 3.27
A
mixture of K2CO3 (5.94 g, 43 mmol), CuI (4.1 g,
22 mmol), 4-chloro-but-2-yn-1-ol (2; 4.47 g, 43 mmol),
NaI (6.44 g, 43 mmol) and methyl hex-5-ynoate (5.46 g,
43 mmol) in DMF (86 mL) was stirred overnight at 258C.
The mixture was diluted with ethyl acetate and plugged
through a pad of celite. It was washed with saturated NH4Cl
followed by brine. The solution was dried over MgSO4 and
the solvent was evaporated under vacuum. The oily residue
was dissolved in hexanes/ethyl acetate (1/1) and plugged
through a pad of silica gel to provide a yellowish oil (7.2 g,
87%) which was used in the subsequent step without further
puri®cation since some of the diyne decomposed upon ¯ash
chromatography. 1H NMR d 1.81 (quint, 2H, Jˆ6.7 Hz), 2.23
(tt, 2H, Jˆ6.7, 2.2 Hz), 2.43 (t, 2H, Jˆ7.4 Hz), 3.17 (quint,
2H, Jˆ2.2 Hz), 3.67 (s, 3H), 4.25 (dt, 2H, Jˆ6, 2.2 Hz).
Methyl 14-triphenylphosphonio-tetradeca-all-cis-5,8,11-
trienoate iodide 7. To a stirred solution of triphenyl-
phosphine (456 mg, 1.74 mmol) and imidazole (118 mg,
1.74 mmol) in Et2O/CH3CN (5/1.7 mL) cooled to 08C, I2
was added (441 mg, 1.74 mmol) in several portions. The
resulting slurry was warmed to 258C and stirred for
20 min. It was again cooled to 08C and the alcohol 6 was
added slowly. The mixture was warmed to 258C after
addition and stirred for 1 h. It was diluted with pentane/
ether (4/1) and plugged through a pad of silica gel to yield
the iodide as a colorless oil (562 mg, 98%). 1H NMR d 1.70
(quint, 2H, Jˆ7.4 Hz), 1.95±2.17 (m, 4H), 2.32 (t, 2H,
14-Hydroxy-tetradeca-5,8,11-triynoic acid methyl ester
5. To a stirred solution of diyne 3 (8.65 g, 44.6 mmol) and

9200
O. Dasse et al. / Tetrahedron 56 (2000) 9195±9202
Jˆ7.4 Hz), 2.66 (q, 2H, Jˆ7.4 Hz), 2.80 (m, 2H), 3.15
(t, 2H, Jˆ7.2 Hz), 3.66 (s, 3H), 5.29±5.58 (m, 6H).
Jˆ5.5 Hz), 2.81 (t, 2H, Jˆ5.5 Hz), 2.92 (t, 2H,
Jˆ5.5 Hz), 3.87 (s, 3H), 4.34 (d, 2H, Jˆ5.8 Hz), 5.12±
5.25 (m, 2H), 5.30±5.41 (m, 6H), 5.60 (s, 1H), 5.63 (br s,
1H), 6.74±6.87 (m, 3H). Anal. Calcd for C31H44O3N.20.6H2O:
C, 75.87; H, 9.99. Found: C, 75.89; H, 9.89.
A solution of triphenylphosphine (2.25 g, 8.6 mmol) and the
above iodide (2.83 g, 7.82 mmol) in acetonitrile (50 mL)
was re¯uxed overnight. The solvent was removed under
reduced pressure and the oily residue was puri®ed by wash-
ing and decanting with hexanes/benzene (1/1; 80 mL). The
solvent was removed and the oily residue was heated in a
vacuum oven overnight at 608C to yield 7 as a yellow
gum (90%) which was used in the subsequent step without
further puri®cation. 1H NMR d 1.66 (quint, 2H, Jˆ7.4 Hz),
2.04 (q, 2H, Jˆ7.4 Hz), 2.29 (t, 2H, Jˆ7.4 Hz), 2.39±2.52
(m, 2H), 2.58 (t, 2H, Jˆ7.2 Hz), 2.63 (t, 2H, Jˆ6.6 Hz),
3.64 (s, 3H), 3.80±3.90 (m, 2H), 5.14±5.67 (m, 6H),
7.64±7.73 (m, 6H), 7.78±7.88 (m, 9H).
2,2-Dimethyl-(tetrahydro-pyran-6-yloxy)-hexanal 11.
Ethyl 2,2-dimethyl-hex-5-enoate 16:22 To a stirred solution
of diisopropylamine (5.7 mL, 41 mmol) in THF cooled to
2788C was added dropwise a 2.5 M solution of n-BuLi in
hexanes (16.4, 41 mL). The reaction mixture was stirred for
30 min and ethyl isobutyrate 14 (5.1 mL, 37 mmol) was
added dropwise at 2788C. The mixture was stirred for
30 min and 4-bromo-but-1-ene (15; 5.0 g, 37 mmol) in
HMPA (7.4 mL) was added dropwise. Upon addition, the
mixture was left to warm to 258C and was stirred for 2 h. It
was quenched with water and extracted with ethyl acetate.
The organic extract was then washed with 10% HCl, satu-
rated NaHCO3 and dried over MgSO4. The residual oil was
plugged through a pad of silica gel (4/1 hexanes/EtOAc) to
16,16-Dimethyl-docosa-5,8,11,14-all-cis-tetraenoic acid
methyl ester 9.22 To a stirred solution of the phosphonium
salt 7 (686 mg, 1.1 mmol) in THF/HMPA (6/1 mL) cooled
to 2108C was added dropwise a 1 M solution of NHMDS in
THF (1.1 mL). The mixture was stirred at 08C for 30 min
and cooled to 2788C. The aldehyde 8 (171 mg, 1.1 mmol)22
was added dropwise in THF (1.5 mL) to the reaction
mixture. The cooling bath was removed and it was left to
warm to 258C over 2 h. It was quenched with hexanes and
the mixture was plugged through a pad of silica gel (eluting
with ethyl acetate/hexanes 1/4). The ®ltrate was dried over
MgSO4 and the solvent was removed under reduced pres-
sure. The oily residue was puri®ed by ¯ash chromatography
(3% EtOAc/97% hexanes) to yield the tetraene 9 as a color-
1
yield a slightly yellow oil (5.54 g, 88%). H NMR d 1.17
(s, 6H), 1.24 (t, 3H, Jˆ7.2 Hz), 1.56±1.63 (m, 2H), 1.94±
2.02 (m, 2H), 4.10 (q, 2H, Jˆ7.2 Hz), 4.92 (ddt, 1H,
Jˆ10.2, 1.9, 1.4 Hz), 4.99 (ddt, 1H, Jˆ17, 1.9, 1.9 Hz),
5.78 (ddt, 1H, Jˆ17, 10.2, 6.6 Hz).
Ethyl 2,2-dimethyl-6-hydroxy-hexanoate 17:30 To a stirred
0.5 M solution of 9-BBN in THF (65.2 mL, 32.6 mmol) was
added ethyl 2,2-dimethyl-hex-5-enoate (16; 5.54 g,
32.6 mmol) in THF (16.2 mL). After 2 h at 258C, the reac-
tion mixture was cooled to 08C. Ethanol (20 mL) was added
followed by 6N NaOH (6.5 mL) and 30% H2O2 (13 mL).
The mixture was then heated to 508C and stirred for 1 h.
After cooling to 258C, it was diluted with brine and
extracted with EtOAc. The organic layer was dried and
evaporated under vacuum. Puri®cation of the oil by ¯ash
chromatography (1/1 hexanes/EtOAc) yielded the alcohol
1
less oil (0.25 g, 61%). H NMR d 0.87 (t, 3H, Jˆ6.6 Hz),
1.09 (s, 6H), 1.18±1.35 (m, 10H), 1.70 (quint, 2H,
Jˆ7.4 Hz), 2.00±2.11 (m, 2H), 2.32 (t, 2H, Jˆ7.4 Hz),
2.70±2.91 (m, 6H), 3.66 (s, 3H), 5.12±5.25 (m, 2H),
5.30±5.41 (m, 6H).
1
16,16-Dimethyl-docosa-5,8,11,14-all-cis-tetraenoic acid
(4-hydroxy-3-methoxy-benzyl) amide 10.22 To a stirred
solution of ester 9 (250 mg, 0.67 mmol) in MeOH
(33 mL) and water (11 mL) was added LiOH´H2O
(190 mg, 4.8 mmol) and the reaction mixture was stirred
at 558C overnight. It was diluted with ether and acidi®ed
with 10% HCl. The layers were separated and the aqueous
layer was extracted with ether. The combined organic layers
were dried over MgSO4 and evaporated to yield the crude
acid (224 mg, 93%) which was used directly. The acid
(224 mg, 0.62 mmol) was dissolved in CH2Cl2 (7 mL) and
cooled to 08C. A 2 M solution of oxalyl chloride in CH2Cl2
(0.67 mL) was added dropwise followed by 2 drops of
DMF. The ice bath was removed and the mixture was stirred
at 258C for 2 h. The solvent was evaporated under vacuum.
A solution of the acid chloride in CH2Cl2 (3 mL) was added
to a solution of 4-hydroxy-3-methoxy benzylamine (1 g,
5.2 mmol) in CH2Cl2 (5 mL) at 08C. The ice bath was
removed and the mixture was stirred at 258C overnight. It
was diluted with CH2Cl2 and washed with brine. The
organic layer was dried over MgSO4 and then concentrated
in vacuo. The crude product was puri®ed by ¯ash chroma-
tography (hexanes/EtOAc 2/1) to yield the amide 10
as a colorless oil (5.1 g, 83%). H NMR d 1.17 (s, 6H),
1.21±1.34 (m, 4H), 1.24 (t, 3H, Jˆ7.2 Hz), 1.49±1.55
(m, 2H), 3.63 (br s, 2H), 4.10 (q, 2H, Jˆ7.2 Hz).
Ethyl 2,2-dimethyl-6-(tetrahydro-pyran-2-yloxy)-hexanoate
18:31 A mixture of alcohol 17 (5.1 g, 27 mmol), PPTS
(200 mg, 0.8 mmol) and DHP (2.96 mL, 32.4 mmol) in
CH2Cl2 was stirred at 258C for 4 h. The mixture was diluted
with water and extracted with CH2Cl2. The organic layer
was dried over MgSO4 and evaporated to yield the product
1
as a colorless oil (6.75 g, 92%). H NMR d 1.16 (s, 6H),
1.23±1.32 (m, 4H), 1.24 (t, 3H, Jˆ7.2 Hz), 1.49±1.90
(m, 8H), 3.36 (dt, 1H, Jˆ9.4, 6.6 Hz), 3.48±3.52 (m, 1H),
3.70 (dt, 1H, Jˆ9.4, 6.6 Hz), 3.83±3.90 (m, 1H), 4.10 (q, 2H,
Jˆ7.2 Hz), 4.56 (br t, 1H, Jˆ2.5 Hz).
2,2-Dimethyl-(tetrahydro-pyran-6-yloxy)-hexan-1-ol 19:32
To a suspension of LAH (943 mg, 24.8 mmol) in ether
(120 mL) cooled to 08C was added the ester 18 (6.75 g,
24.8 mmol) in ether (10 mL) dropwise. After stirring for
30 min the reaction was quenched by the careful addition
of water. The aqueous layer was extracted with ether and the
combined organic layers were dried and evaporated to
1
1
(170 mg, 55%). H NMR d 0.87 (t, 3H, Jˆ6.9 Hz), 1.08
provide the alcohol as a colorless oil (5.34 g, 95%). H
NMR d 0.86 (s, 6H), 1.23±1.32 (m, 4H), 1.49±1.90
(m, 8H), 3.30 (dd, 2H, Jˆ6.3, 1.9 Hz), 3.41 (dt, 1H,
(s, 6H), 1.22±1.35 (m, 10H), 1.73 (quint, 2H, Jˆ7.4 Hz),
2.00±2.12 (m, 2H), 2.20 (t, 2H, Jˆ7.4 Hz), 2.77 (t, 2H,

O. Dasse et al. / Tetrahedron 56 (2000) 9195±9202
9201
Jˆ9.4, 6.6 Hz), 3.48±3.52 (m, 1H), 3.75 (dt, 1H, Jˆ9.4,
6.6 Hz), 3.83±3.90 (m, 1H), 4.56 (br t, 1H, Jˆ2.5 Hz).
(m, 6H), 5.72 (br s, 1H), 6.74±6.87 (m, 3H). Anal. Calcd
for C30H45O4N.0.6H2O: C, 72.87; H, 9.41. Found: C, 72.77;
H, 9.34.
2,2-Dimethyl-(tetrahydro-pyran-6-yloxy)-hexanal 11:33 To
a stirred suspension of PCC (4.55 g, 21.45 mmol) and celite
in CH2Cl2 (40 mL) was added a solution of the alcohol 19
(3.3 g, 14.3 mmol) in CH2Cl2 (10 mL). The mixture was
stirred at 258C for 2 h. It was then ®ltered through a pad
of silica gel (hexanes/EtOAc 3/1) and the solution was
evaporated to yield the aldehyde as a colorless oil (3.6 g,
20-Bromo-16,16-dimethyl-eicosa-5,8,11,14-all-cis-tetra-
enoic acid methyl ester 20.34 To a stirred solution of tri-
phenylphosphine (524 mg, 2 mmol) in CH2Cl2 (4 mL)
cooled to 08C was added bromine (0.1 mL, 1.95 mmol).
The tetraene 12 (850 mg, 1.9 mmol) was then added drop-
wise and the ice bath was removed. The reaction mixture
was stirred overnight at 258C. The solvent was removed
under vacuum and the residue was dissolved in hexanes/
EtOAc (9/1) and plugged through a pad of silica gel. Further
puri®cation by ¯ash chromatography (hexanes/EtOAc 9/1)
provided the desired bromide 20 (404 mg, 50%). 1H NMR d
1.10 (s, 6H), 1.25±1.40 (m, 4H), 1.70 (quint, 2H, Jˆ7.2 Hz),
1.82 (quint, 2H, Jˆ7.2 Hz), 2.10 (m, 2H), 2.31 (t, 2H,
Jˆ7.2 Hz), 2.75±2.95 (m, 6H), 3.40 (t, 2H, Jˆ6.6 Hz),
3.66 (s, 3H), 5.12±5.41 (m, 8H).
1
79%). H NMR d 1.04 (s, 6H), 1.23±1.32 (m, 4H), 1.45±
1.85 (m, 8H), 3.36 (dt, 1H, Jˆ9.4, 6.6 Hz), 3.48±3.52
(m, 1H), 3.70 (dt, 1H, Jˆ9.4, 6.6 Hz), 3.83±3.90 (m, 1H),
4.56 (br t, 1H, Jˆ2.5 Hz), 9.44 (s, 1H).
20-(Tetrahydro-pyran-2-yloxy)-16,16-dimethyl-eicosa-
5,8,11,14-all-cis-tetraenoic acid methyl ester 12.22 To a
stirred solution of the phosphonium salt 7 (4.36 g,
6.98 mmol) in THF/HMPA (40/5 mL) cooled to 2108C
was added dropwise a 1 M solution of NHMDS in THF
(6.98 mL). The mixture was stirred at 08C for 30 min and
cooled to 2788C. The aldehyde 11 (1.58 g, 6.98 mmol) was
added dropwise in THF (8 mL) to the reaction mixture. The
cooling bath was removed and it was left to warm to 258C
over 2 h. It was quenched with hexanes and the mixture was
plugged through a pad of silica gel (eluting with ethyl
acetate/hexanes 1/4). The ®ltrate was dried over MgSO4
and the solvent was removed under reduced pressure. The
oily residue was puri®ed by ¯ash chromatography (EtOAc/
hexanes 1/4) to yield the tetraene 12 as a colorless oil
(1.56 g, 50%). 1H NMR d 1.10 (s, 6H), 1.25±1.40 (m, 4H),
1.45±1.63 (m, 8H), 1.70 (quint, 2H, Jˆ7.4 Hz), 1.97±2.13
(m, 2H), 2.31 (t, 2H, Jˆ7.4 Hz), 2.75±2.95 (m, 6H), 3.37
(dt, 1H, Jˆ9.6, 6.6 Hz), 3.50 (br dt, 1H, Jˆ11.3, 5.2 Hz),
3.66 (s, 3H), 3.72 (dt, 1H, Jˆ9.6, 6.6 Hz), 3.86 (br dt, 1H,
Jˆ11.3, 5.2 Hz), 4.57 (br t, 1H, Jˆ4.4 Hz), 5.12±5.41
(m, 8H).
20-Cyano-16,16-dimethyl-eicosa-5,8,11,14-all-cis-tetra-
enoic acid methyl ester 21.35 A mixture of bromide 20
(318 mg, 0.68 mmol) and KCN (90 mg, 1.36 mmol) in
DMSO (3.4 mL) was heated at 508C for 5 h. After cooling,
the reaction mixture was diluted with hexanes/EtOAc (4/1)
and plugged through a pad of silica gel. Further puri®cation
by ¯ash chromatography (hexanes/EtOAc 9/1) afforded the
cyano derivative 21 (195 mg, 78%). 1H NMR d 1.11 (s, 6H),
1.30±1.49 (m, 4H), 1.63 (quint, 2H, Jˆ7.6 Hz), 1.70 (quint,
2H, Jˆ7.2 Hz), 2.00±2.12 (m, 2H), 2.32 (t, 4H, Jˆ7.6 Hz),
2.75±2.95 (m, 6H), 3.66 (s, 3H), 5.17±5.25 (m, 2H), 5.31±
5.43 (m, 6H).
20-Bromo-16,16-dimethyl-eicosa-5,8,11,14-all-cis-tetra-
enoic acid (4-hydroxy-3-methoxy-benzyl) amide 22.22 To
a stirred solution of bromide 20 (404 mg, 0.97 mmol) in
MeOH (48 mL) and water (16 mL) was added LiOH.H2O
(267 mg, 6.8 mmol) and the mixture was stirred at 258C
overnight. It was diluted with ether and acidi®ed with
10% HCl. The layers were separated and the aqueous
layer was extracted with ether. The combined organic layers
were dried over MgSO4 and evaporated to yield the crude
acid (375 mg, 94%) which was used directly in the next
step. The acid (200 mg, 0.49 mmol) was dissolved in
CH2Cl2 (5 mL) and cooled to 08C. A 2 M solution of oxalyl
chloride in CH2Cl2 (0.49 mL) was added dropwise followed
by 2 drops of DMF. The ice bath was removed and the
mixture was stirred at 258C for 2 h. The solvent was evapo-
rated under vacuum. A solution of the acid chloride in
CH2Cl2 (3 mL) was added to a solution of 4-hydroxy-3-
methoxy benzylamine (0.4 mL, 5 mmol) in CH2Cl2 (5 mL)
at 08C. The ice bath was removed and the mixture was
stirred at 258C overnight. It was diluted with CH2Cl2 and
washed with brine. The organic layer was dried over MgSO4
and then concentrated in vacuo. The crude product was
puri®ed by ¯ash chromatography (hexanes/EtOAc 1/1) to
yield the amide 22 (85 mg, 32%). 1H NMR d 1.10 (s, 6H),
1.31±1.45 (m, 4H), 1.73 (quint, 2H, Jˆ7.4 Hz), 1.82 (quint,
2H, Jˆ6.9 Hz), 2.00±2.12 (m, 2H), 2.20 (t, 2H, Jˆ7.4 Hz),
2.77 (t, 2H, Jˆ5.5 Hz), 2.81 (t, 2H, Jˆ5.5 Hz), 2.91 (t, 2H,
Jˆ5.5 Hz), 3.40 (t, 2H, Jˆ6.9 Hz), 3.86 (s, 3H), 4.34 (d, 2H,
Jˆ5.8 Hz), 5.12±5.25 (m, 2H), 5.30±5.41 (m, 6H), 5.59
(s, 1H), 5.62 (br s, 1H), 6.74±6.87 (m, 3H). Anal. Calcd
16,16-Dimethyl-20-hydroxy-eicosa-5,8,11,14-all-cis-
tetraenoic acid (4-hydroxy-3-methoxy-benzyl) amide
13.22 To a stirred solution of tetraene 12 (300 mg,
0.67 mmol) in MeOH (33 mL) and water (11 mL) was
added LiOH´H2O (190 mg, 4.8 mmol) and the mixture
was stirred at 258C overnight. It was diluted with ether
and acidi®ed with 10% HCl. The layers were separated
and the aqueous layer was extracted with ether. The
combined organic layers were dried over MgSO4 and evapo-
rated to yield the crude acid (258 mg, 90%) which was used
directly in the next step. The acid was added to a stirred
solution of 4-hydroxy-3-methoxy benzylamine (358 mg,
1.89 mmol) pretreated with Et3N, DMAP (93 mg,
0.76 mmol) and EDCI (146 mg, 0.76 mmol) in CH2Cl2
(5 mL) cooled to 08C. The mixture was stirred for 30 min
and the ice bath was removed. It was left to stir overnight at
258C. The reaction mixture was diluted with CH2Cl2 and
plugged through a pad of celite. Puri®cation by ¯ash
chromatography (hexanes/EtOAc 4/1) provided the amide
(80 mg, 26%). 1H NMR d 1.09 (s, 6H), 1.28±1.40 (m, 4H),
1.52 (quint, 2H, Jˆ6.3 Hz), 1.73 (quint, 2H, Jˆ7.4 Hz),
2.00±2.12 (m, 2H), 2.20 (t, 2H, Jˆ7.4 Hz), 2.77 (t, 2H,
Jˆ5.5 Hz), 2.80 (t, 2H, Jˆ 5.5 Hz), 2.92 (t, 2H,
Jˆ5.5 Hz), 3.62 (dt, 2H, Jˆ6.3, 5.5 Hz), 3.87 (s, 3H),
4.33 (d, 2H, Jˆ5.8 Hz), 5.12±5.25 (m, 2H), 5.30±5.41

9202
O. Dasse et al. / Tetrahedron 56 (2000) 9195±9202
for C30H44O3NBr.0.4H2O: C, 65.06; H, 8.15. Found: C,
65.06; H, 7.97.
13. Sugiura, T.; Kondo, S.; Sukagawa, A.; Nakane, S.; Shinoda,
A.; Itoh, K.; Yamashita, A.; Waku, K. Biochem. Biophys. Res.
Commun. 1995, 215, 89±97.
20-Cyano-16,16-dimethyl-eicosa-5,8,11,14-all-cis-tetra-
enoic acid (4-hydroxy-3-methoxy-benzyl) amide 23. Pre-
pared as described for 20-Bromo-16,16-dimethyl-eicosa-
5,8,11,14-all-cis-tetraenoic acid (4-hydroxy-3-methoxy-
benzyl) amide 22 (28%). 1H NMR d 1.10 (s, 6H),
1.31±1.45 (m, 4H), 1.62 (quint, 2H, Jˆ7.1 Hz), 1.73
(quint, 2H, Jˆ7.4 Hz), 2.00±2.12 (m, 2H), 2.20 (t, 2H,
Jˆ7.4 Hz), 2.33 (t, 2H, Jˆ7.2), 2.77 (t, 2H, Jˆ5.5 Hz),
2.81 (t, 2H, Jˆ5.5 Hz), 2.91 (t, 2H, Jˆ5.5 Hz), 3.86
(s, 3H), 4.34 (d, 2H, Jˆ5.8 Hz), 5.12±5.25 (m, 2H), 5.30±
5.41 (m, 6H), 5.59 (s, 1H), 5.62 (br s, 1H), 6.74±6.87
(m, 3H). Anal. Calcd for C31H44O3N.20.4H2O: C, 75.29;
H, 9.01. Found: C, 74.99; H, 8.87.
14. Di Marzo, V.; Bisogno, T.; Melck, D.; Ross, R.; Brockie, H.;
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The authors are grateful to NIDA Grants DA-09789 and
DA-08904 for the support of this work.
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