Synthesis and spectral properties of amphophilic lipids with linear conjugated polyene and phenylpolyene fluorescent groups

Article abstract of DOI:10.1002/ejoc.200600954

Lipophilic fluorescent groups with a chain-like linear conformation emitting in the visible range and with high photostability are presently unavailable. These structures would be of great interest as labels for long-chain fatty acids and phospholipids lacking intrinsic fluorescent groups. With this aim in mind, we report the synthesis and the spectroscopic characterization of a series of emitting amphiphilic lipids that may approach that ideal fluorescent tag. Each lipid was constructed by attaching a linear, all-(E) conjugated pentaene, tetraenyne, ω-phenyltetraene, or ω-phenyltrienyne chromophore to a hydrophilic head-group through a polymethylene chain spacer. The key steps of the synthesis were the Pd ⁰-mediated cross-coupling reaction between bromopolyenes and terminal acetylenic compounds, yielding tetraenynes or ω-phenyltrienynes, and the subsequent triple-bond partial reduction, producing the corresponding pentaenes or ω-phenyltetraenes in good overall yields. This method represents a further successful example of the so-called "acetylenic approach" to the indirect high-yield synthesis of polyene systems. In the case of ω-phenyltrienynes, a higher proportion of the all-(E) isomer was obtained using an alternative method based on the reaction of an ω- phenyldienylphosphonate with an α-acetylenic aldehyde. Some of the resulting compounds exhibit spectral and photochemical properties that warrant their use as emitting lipophilic tags. Thus, the cophenyltetraene and ω-phenyltrienyne members of the series show intense absorption bands in the 320-370 nm range with fluorescence emission centered at 475 nm and quantum yields up to 0.25. These parameters are appropriate for the applications noted above. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejoc.200600954

FULL PAPER
DOI: 10.1002/ejoc.200600954
Synthesis and Spectral Properties of Amphiphilic Lipids with Linear
Conjugated Polyene and Phenylpolyene Fluorescent Groups
Ernesto Quesada,[a,b][‡] Javier Delgado,[a,b] Valentín Hornillos,[b] A. Ulises Acuña,*[a] and
Francisco Amat-Guerri*[b]
Keywords: Amphiphiles / Polyenes / Cross-coupling / Enynes / Fluorescent probes
Lipophilic fluorescent groups with a chain-like linear confor- phenyltetraenes in good overall yields. This method repre-
mation emitting in the visible range and with high photosta-
bility are presently unavailable. These structures would be
of great interest as labels for long-chain fatty acids and phos-
pholipids lacking intrinsic fluorescent groups. With this aim
sents a further successful example of the so-called “acetyle-
nic approach” to the indirect high-yield synthesis of polyene
systems. In the case of ω-phenyltrienynes, a higher pro-
portion of the all-(E) isomer was obtained using an alterna-
in mind, we report the synthesis and the spectroscopic char- tive method based on the reaction of an ω-phenyldienylphos-
acterization of a series of emitting amphiphilic lipids that
may approach that ideal fluorescent tag. Each lipid was con-
structed by attaching a linear, all-(E) conjugated pentaene,
tetraenyne, ω-phenyltetraene, or ω-phenyltrienyne chromo-
phore to a hydrophilic head-group through a polymethylene
chain spacer. The key steps of the synthesis were the Pd0-
mediated cross-coupling reaction between bromopolyenes
and terminal acetylenic compounds, yielding tetraenynes or
ω-phenyltrienynes, and the subsequent triple-bond partial
reduction, producing the corresponding pentaenes or ω-
phonate with an α-acetylenic aldehyde. Some of the resulting
compounds exhibit spectral and photochemical properties
that warrant their use as emitting lipophilic tags. Thus, the ω-
phenyltetraene and ω-phenyltrienyne members of the series
show intense absorption bands in the 320–370 nm range with
fluorescence emission centered at 475 nm and quantum
yields up to 0.25. These parameters are appropriate for the
applications noted above.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
or nanocrystals. Before these methods can be extended to
lipid research a number of shortcomings need to be solved,
chiefly the absence of intrinsic emitting chromophores in
most natural lipids. This problem may be circumvented by
attaching a fluorescent tag to the original lipid structure to
produce a fluorescent lipid analogue, as in the case of pro-
teins and nucleic acids. However, this approach still presents
difficulties. Since natural lipids are usually amphipathic
molecules, the emitting label might be attached to either the
polar or the non-polar part of the molecule. In the first
case, xanthene, cyanine, and other dyes have frequently
been used, all with very convenient spectral properties in
the visible range and reasonable photostability.[14] Unfortu-
nately, the labeling dye also introduces foreign ionizable
groups that were not present in the original structure as
well as substantial changes of electron charge distribution,
molecular size and conformation. Alternatively, the non-po-
lar part of the lipid might be labeled with a lipophilic flu-
orophore such as a multiring aromatic system (anthracene,
pyrene, perylene, etc.) or difluoroborodipyrromethene
(BODIPY) dyes. However, the task of preserving as much
as possible the structure, polarity and conformation of the
original apolar chains is even more difficult in this case and
often this strategy fails to produce a fully functional ana-
logue of the parent lipid.
Introduction
Lipids are essential components of all living organisms
and an understanding of the structures, dynamics, functions
and metabolic pathways of natural lipids at a molecular
level is being pursued with intense activity.[1] In addition,
there is a growing number of synthetic, lipid-like com-
pounds that present interesting biological properties, such
as, anti-tumoral[2–4] or anti-protozoal[5–10] activity. At the
same time, fluorescence techniques have now become the
primary methods in protein and nucleic acid research.[11,12]
This is due to the availability of very specific and sensitive
fluorescent assays, new high-resolution fluorescence micro-
scopes,[13] and a large variety of hydrophilic fluorophores in
the form of water-soluble organic dyes, fluorescent proteins,
[a] Instituto de Química Física “Rocasolano”, C.S.I.C.,
Serrano 119, 28006 Madrid, Spain
Fax: +34-91-546-24-31
E-mail: roculises@iqfr.csic.es
[b] Instituto de Química Orgánica, C.S.I.C.,
Juan de la Cierva 3, 28006 Madrid, Spain
Fax: +34-91-564-48-53
E-mail: famat@iqog.csic.es
[‡] Current address: Instituto de Química Médica, C.S.I.C., Dpt.
Chemotherapy,
Juan de la Cierva 3, 28006 Madrid, Spain
Supporting information for this article is available on the
WWW under http://www.eurjoc.org or from the author.
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Conjugated linear polyenes are strongly absorbing non- ling reaction) is a useful way of preparing conjugated acety-
polar chromophores that may attain modest but useful lenic compounds. In recent years, this reaction has emerged
fluorescence yields. These groups retain several characteris- as a general, reliable, and efficient method for the synthesis
tics of the aliphatic chains of common lipids and are not of complex molecules.[29–31] This reaction can be combined
strangers to the pool of natural polyunsaturated lipids.[15,16] with selective triple-bond partial reduction (the acetylenic
This structural similarity has been exploited in the past to approach) to synthesize polyene systems stereoselectively.[32]
develop the natural parinaric fatty acid, all-(E)-9,11,13,15- This strategy is more convenient than the use of the Stille[33]
octadecatetraenoic acid, as a fluorescent probe of lipid bi- or Suzuki[34–36] reactions particularly when the respective
layers and cell membranes.[17–20] Extending the parinaric organostannane or -borane compound required is either
acid conjugated system from four to five double bonds gives unavailable or too unstable. Several conjugated polyene and
rise to a new fluorophore with a red-shifted intense absorp- polyenyne systems have been prepared in our laboratory by
tion, a fluorescence spectrum centered in the blue region this approach.[23,24,28] In this work, the target compounds
(ca. 470 nm), and improved spectroscopic properties.[21–24] were obtained similarly, following the sequence shown in
In this way we could show[21,22] that the fluorescent all-(E)- Scheme 1. The first step was the cross-coupling[37,38] be-
octadeca-8,10,12,14,16-pentaenoic acid (t-COPA) may be a tween a bromopolyene 1 [in the form of a 3:7 (1E,..)/(1Z,..)
good choice for probing important properties of lipid bi- mixture of isomers] and an alkyne 2. In preliminary assays
layers and membranes by means of the usual cuvette spec- designed to optimize reaction conditions, the coupling be-
trofluorimetric methods. However, excitation of t-COPA in tween bromotetraene 1A and acetylenic ester 2d was studied
the near UV region (ca. 350 nm) is still unpractical for lipid in some detail. In the presence of a 30% excess of 2d, 1A
imaging in standard wide-field fluorescence microscopes. In disappeared from the reaction medium after around 30 min
recent times new confocal optical microscopes have become at room temperature, yielding 3Ad. A larger excess of 2d
available in which fluorophores can be easily excited by gave rise to the 2d–2d homocoupling byproduct, easily sep-
two-photon absorption[25,26] using, for example, a Ti:Za la- arable from the expected product 3Ad by chromatographic
ser. This laser can be tuned within the 690–1000 nm range methods. In contrast, both the starting compound 2d and
and, therefore, provides an alternative method for the two- the product 3Ad show almost similar chromatographic be-
photon excitation of the conjugated pentaene fluorophore havior. This was also observed with other compounds 2 and
(2ϫ350 nm). In fact, Thiele and co-workers have recently their corresponding cross-coupling products 3. For this
demonstrated this possibility in a very elegant way.[27] They reason, at the end of the reaction, when 1A could no longer
showed first that living mammalian cells readily take up be detected, the unreacted excess of 2d was converted into
a lipid precursor labeled with the t-COPA emitting group its homocoupling product by bubbling air through the mix-
without altering the natural metabolic paths. Next, they ture for a short time in order to oxidize the Pd0 complexes
showed that the microdomains of the cell lipids incorporat- to PdII species (the species catalyzing the homocoupling).
ing the pentaene group could be imaged in high contrast by In this way, product 3Ad can be easily purified by silica gel
two-photon excitation of the pentaene chromophore.
chromatography without degradation. This oxidation pro-
The absorbing/fluorescent properties of a polyene chain cess was also carried out in the other cross-coupling reac-
may be further improved by introducing an ω-phenyl resi- tions described herein. A thoroughly deoxygenated dieth-
due with a relatively modest increase in molecular size. This ylamine/THF mixture was used as the reaction medium in-
approach has also been used recently to obtain an emitting stead of the pure amine to completely dissolve 1A. A mix-
analogue of the ether lipid drug edelfosine[28] in which the ture of dichlorobis(triphenylphosphane)palladium(II) ([Pd-
anti-cancer activity of the original lysophospholipid is pre- (PPh3)2Cl2]) and copper(I) iodide (5 and 17 mol-%, respec-
served. With the purpose of exploring the use of new poly- tively, with regard to 1A) was used as the catalyst. With
ene and phenylpolyene systems to produce additional fluo- freshly prepared tetrakis(triphenylphosphane)palladium(0)
rescent lipid analogues, we report a general strategy for the ([Pd(PPh3)4], 5 mol-%), a less efficient catalyst,[37] much
synthesis of amphipathic structures containing diverse lipo- lower yields of the coupling product were obtained even
philic, linear π-conjugated chromophores that absorb in the after longer reaction times under similar experimental con-
350–370 nm range. In these compounds, conjugated penta- ditions.
ene, tetraenyne, ω-phenyltetraene, or ω-phenyltrienyne
By using the optimized conditions detailed above, the
groups were attached to simple polar residues Ϫ primary complete series of compounds 3 were similarly obtained (in
alcohol, acetate, carboxylic acid, or methyl ester Ϫ through yields higher than 80%) by cross-coupling between the cor-
a linear aliphatic chain of 5–8 methylene groups. As we responding bromopolyenes 1 and alkynes 2. In all cases, the
wanted to optimize the fully-extended conformation of the stereochemistry of the double bond in the 1-position in 1
chromophore, all-(E) isomers were consistently selected as did not change during the reaction and the same 3:7 (E)/
the double-bond systems.
(Z) ratio was obtained for each compound 3, as ex-
pected.[39] These isomers could not be separated by either
chromatography on silica gel or by crystallization, although
pure samples of the corresponding all-(E)-3 isomers could
Results and Discussion
Synthesis of Polyenynes 3 and Polyenes 4 and 5
The Pd/Cu-catalyzed reaction of terminal alkynes with be separated by selective precipitation from concentrated
sp2 carbon halides (the Sonogashira–Hagihara cross-coup- CHCl3 or CH2Cl2 solutions by careful addition of n-pen-
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Amphiphilic Lipids with Polyene and Phenylpolyene Groups
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Scheme 1. Reagents and conditions: i) 2/1 = 1.3 (molar), [Pd(PPh3)2Cl2] (5 mol-% on 1), CuI (17 mol-% on 1), Et2NH, THF, Ar, room
temperature, 1–3 h; ii) Zn/Cu/Ag, MeOH/H2O, 1:1, room temperature, Ar, 24 h; iii) I2 (trace), hexane, Ar, 15 min, reflux; iv) KOH
(5 equiv.), EtOH, room temperature, Ar, 4 h; v) t-BuOK, THF, 0 °C, then room temperature, 1 h, 60%; vi) TBAF, THF, room temperature,
40 min, 98%.
tane. In the case of products 3A, the (E)/(Z) mixtures ob-
This approach allows access to all-(E)-polyene systems in
tained could be converted into the corresponding all-(E) a simple and efficient way that is more convenient than use
isomers with a trace of iodine.[24] In contrast, mixtures of of the Wittig reaction for the same purpose, as was de-
isomeric 3B compounds could not be isomerized by this scribed before for the synthesis of the acid 5Af (t-
procedure and pure all-(E)-3B isomers had to be separated COPA).[21,27] This method can be scaled up for the prepara-
from the corresponding (E)/(Z) mixtures by precipitation, tion of larger amounts of product and, also, it can be used
as above. An alternative approach that yields a much higher to prepare other similar compounds with different poly-
proportion of all-(E)-3B isomers is shown below.
methylene chain lengths and terminal polar groups. For ex-
Partial reduction of the triple bond in any of the isomeric ample, the CH2OH group could allow the easy introduction
polyenyne compounds 3 or their mixtures with zinc acti- of a phosphate as the terminal polar group.
vated with copper and silver (the Boland method)[32]
yielded the corresponding polyenes 4. This reduction step
gave rise to compounds with a (Z) double bond in the posi-
tion of the triple bond. Reduction of any other unsaturation
Alternative Synthesis of all-(E)-Phenyltrienynes
moiety in the polyene system was not observed in any case.
As discussed above, the synthesis of conjugated ω-phen-
Subsequent isomerization of the mixtures of polyenes 4 yltrienyne compounds 3B, using as starting material the 1-
with a trace of iodine provided the corresponding all-(E) bromo-6-phenylhexatriene (1B) as a (1E)/(1Z) mixture,[28]
compounds 5 in good overall yields. Hydrolysis of all-(E)- yielded (Z) isomers that could not be isomerized to the cor-
polyenyne esters 3Ab,d and 3Bb,c or of all-(E)-polyenes responding (E) isomers with iodine as was the case for the
5Ab,c and 5Bc gave rise to compounds 3Ae,g, 3Be,f, 5Ae,f, tetraenynes 3A, the pentaenes 4A, and the ω-phenyl-
and 5Bf, respectively, with a primary alcohol or carboxylic tetraenes 4B. Pure all-(E)-3B isomers were isolated in
acid as the terminal polar groups. All polyene and poly- around 30% yield by precipitation with CHCl3/pentane. In
enyne compounds must be conserved completely free of the following, we report an alternative way of obtaining
traces of inorganic acids to prevent uncontrolled acid-cata- much higher yields of the pure all-(E)-3B compounds. The
lyzed double-bond isomerization. The solubility of each method is illustrated with the obtention of alcohol 3Bh, a
specific amphiphilic compound depends on the type of homologue of 3Ba and 3Be with six methylene groups in
head-group, those with a terminal carboxylic acid group the polymethylene chain (Scheme 1). Thus, the reaction be-
being less soluble (Ͻ10–5 ) in common organic solvents, tween diethyl [(2E,4E)-5-phenylpenta-2,4-dienyl]phos-
although they are soluble in DMSO. In an acid-free CHCl3 phonate (6)[40] and the silylated aldehyde 7[41] under
solution, conjugated tetraenyne and ω-phenyltrienyne com- Horner–Wadsworth–Emmons (HWE) conditions gave rise
pounds show much higher thermal and photochemical sta- to the corresponding silylated compound with one more
bility than the corresponding compounds with conjugated double bond and with a larger proportion of the (9E) iso-
pentaene and ω-phenyltetraene systems (data not shown) mer: 9:1 (9E)/(9Z), as determined by 1H NMR spec-
such that no degradation was observed when stored for troscopy. After deprotection with tetrabutylammonium
months at –20 °C and protected from exposure to light.
fluoride in THF[42] the same isomeric mixture of the free
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alcohol 3Bh was produced from which all-(E)-3Bh could
easily be isolated in the pure form by washing the crude
solid with pentane. The stereochemistry of the product in
the HWE reaction is sterically controlled,[43,44] yielding the
(E) isomer as the major product.
Absorption and Fluorescence Properties
In this section, the spectroscopic properties of represen-
tative amphiphilic compounds bearing pentaene, tetraen-
yne, ω-phenyltetraene, and ω-phenyltrienyne conjugated
groups in the 300–600 nm range are described. As expected,
the absorption and emission spectra recorded in this wave-
length range are characteristic of the polyunsaturated
group.
The spectral properties of the all-(E)-pentaene carboxylic
acid 5Af (t-COPA), both in homogeneous solution and in
lipid bilayers, have previously been reported in detail.[22]
The main spectroscopic parameters of the compounds de-
scribed herein containing the same conjugated all-(E)-pen-
Figure 1. Absorption and corrected fluorescence spectra of the
conjugated tetraenyne methyl ester all-(E)-3Ad in CHCl3; [all-(E)-
3Ad] = 2ϫ10–5  (absorption), 2ϫ10–6  (emission); λexc
347 nm; 22 °C.
=
The absorption and fluorescence spectra of 5Bb, which
taene system as t-COPA, 5Ab–e, are very similar to those contains the all-(E)-ω-phenyltetraene fluorophore, is shown
reported for 5Af. Neither the type of terminal polar group in Figure 2. In DMSO solution, the absorption maximum
nor the length of the saturated polymethylene spacer (5–8 appears at 342 nm with an absorption coefficient value
methylene groups) affected these parameters to an appreci- close to 105 –1 cm–1. In this solvent, the fluorescence emis-
able extent (Table 1), indicating the lack of electronic inter- sion, with a maximum at 467 nm, also shows a large Stokes
action between distal groups in these molecules.
shift. The absorption spectrum shifts to longer wavelengths
The all-(E)-tetraenyne group in all-(E)-3Ab–e,g absorbs in a non-polar microenvironment, such as in large unilamel-
in the 270–370 nm range in CHCl3 solution, giving rise in lar vesicles (LUV) of 1,2-dimyristoyl-sn-glycero-3-phos-
the specific case of all-(E)-3Ad to a vibrational sequence phocholine (DMPC) (Figure 3), whereas the emission spec-
band with maxima at 315, 329 and 347 nm (Figure 1, trum is almost insensitive to solvent polarity. The fluores-
Table 1), and a relative intensity distribution very similar cence quantum yield of 5Bb in lipid vesicles is 0.24, signifi-
to that of the conjugated all-(E)-pentaene group, as in the cantly higher than that in EtOH solution (0.15). This effect
carboxylic acid 5Af. The emission spectrum of all-(E)-3Ad of the ordered lipid environment on the emission quantum
in the same solvent is a broad band with little structure yield has already been observed in other polyene com-
(Figure 1), a maximum at around 470 nm and a large pounds[22,23] and is most likely due to the conformational
Stokes shift, indicating important differences between the changes that take place on photoexcitation. It is known that
electronic states involved in the absorption and emission the electron reorganization of single and double bonds
processes. The fluorescence quantum yield is modest leads to large conformational variability of the polyene ex-
(0.075), similar to that of the conjugated pentaenoic acid cited states.[45] This rotational isomerism facilitates relax-
5Af, and the emission does not change after several hours ation channels that quench the fluorescence. In contrast, in
of irradiation in an aerated solution in a standard spectro- a rigid environment, internal rotation modes are hindered,
fluorimeter.
decreasing the radiationless deactivation.
Table 1. Absorption spectroscopic data of representative amphiphilic compounds containing the indicated all-(E) conjugated polyene.
Polyene
Polar end-group
Model compound
Solvent
λmax [nm] (ε [104 –1 cm–1])
Pentaene
CH2OAc
CH2OAc
CH2OAc
CH2OH
CO2H
CO2Me
CH2OH
CH2OH
CH2OH
CH2OH
4Ab[a]
5Ab
5Ab
5Ae
CHCl3
CHCl3
hexane
EtOH
EtOH
CHCl3
CHCl3
EtOH
DMSO
MeOH
319 (4.30), 335 (7.20), 353 (7.10)
319 (4.30), 334 (6.80), 351 (6.50)
311 (4.60), 327 (7.00), 344 (6.90)
312 (6.20), 327 (10.20), 344 (10.50)
312 (6.00), 327 (9.80), 344 (10.30)
315 (4.20), 329 (6.40), 347 (6.40)
315 (4.20), 329 (6.40), 347 (6.40)
325 (8.84), 340 (12.57), 360 (10.61)
333 (7.47), 349 (10.40), 368 (8.76)
321 (4.30), 335 (5.80), 353 (5.20)
5Af[b]
3Ad
3Ae
Tetraenyne
ω-Phenyltetraene
5Ba
5Ba
3Ba
ω-Phenyltrienyne
[a] The (8Z,10E,12E,14E,16E) isomer. [b] t-COPA, data from ref.[22]
.
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the emitting polyene within the bilayer. At higher tempera-
tures, the fluorescence anisotropy decreased, with a sharp
transition at around 23.5 °C. This value corresponds to the
thermal transition between the gel and liquid-crystal phases
of the DMPC lipid bilayer, as determined previously.[22,47]
The changes in the anisotropy of 5Bb reliably reflect the
corresponding large changes in the fluidity of the lipid bi-
layer, indicating that the fluorescence emission originates
from polyene molecules fully embedded in the bilayer.
Figure 2. Absorption and corrected fluorescence spectra of all-(E)-
phenyltetraene acetate 5Bb in DMSO; [all-(E)-5Bb] = 2ϫ10–5
(absorption), 2ϫ10–6  (emission); λexc = 347 nm; 22 °C.

Figure 4. Fluorescence anisotropy, ϽrϾ, of the phenyltetraene ace-
tate 5Bb in lipid vesicles (LUV) of DMPC as a function of tempera-
ture. λexc = 348 nm; λem = 462 nm; [5Bb] ≈ 10–5 ; [DMPC] ≈
10–3 ; [5Bb]/[DMPC] = 1:200.
Figure 3. Absorption spectra of all-(E)-phenyltetraene acetate 5Bb
in EtOH (solid line) and in large unilamellar lipid vesicles of
DMPC (dashed line) at 22 °C.
Conclusions
In symmetric, linear conjugated polyene compounds the
A large variety of amphiphilic linear compounds incor-
1
first excited singlet state (S1) is of type Ag, whereas the porating the conjugated chromophore tetraenyne or ω-
1
S2 state is Bu.[46] In this case, the most intense absorption phenyltrienyne can be synthesized in good yields by the
transition recorded experimentally corresponds to the Sonogashira–Hagihara cross-coupling reaction. In the case
S0ǞS2 excitation because S0ǞS1 is symmetry-forbidden. of the ω-phenyltrienyne members of the series, much higher
However, the emission takes place exclusively from the S1 yields of the all-(E) isomers were obtained by reaction be-
state. The absorption and emission of the all-(E) conjugated tween the appropriate phosphonate and an α-acetylenic al-
groups studied here (pentaene, tetraenyne, ω-phenyl- dehyde under Horner–Wadsworth–Emmons conditions.
tetraene, and ω-phenyltrienyne) probably follow the same Subsequent triple-bond partial reduction with activated
pattern, thus explaining the large Stokes shift and the dif- zinc (Boland reduction) combined with (Z)Ǟ(E) isomeriza-
ferent shapes of the absorption and emission spectra. These tion with a trace of iodine allowed the obtention of the
transition assignments are also consistent with the different corresponding conjugated all-(E) compounds with pentaene
sensitivities of the absorption and emission spectra to the or ω-phenyltetraene groups. The tetraenyne compounds
medium polarity because the charge distribution in the S1 prepared in this way exhibit an intense structured absorp-
and S2 states is different.[22]
tion spectrum in the 315–350 nm range and a wide fluores-
It is expected that the emitting polyenes obtained here cent band centered at ca. 470 nm. These spectroscopic fea-
would readily be incorporated into lipid bilayers because of tures are very similar to those of the conjugated pentaene
their amphiphilic properties. To test this preferential solu- group described previously.[22] Some of the novel chain-like
bility in a lipid environment, the phenyltetraene acetate 5Bb chromophores obtained in this work, such as the all-(E)-
was added to an aqueous suspension of lipid vesicles phenyltetraene and all-(E)-phenyltrienyne conjugated sys-
(LUVs) made up of DMPC and the fluorescence aniso- tems, exhibit a convenient intense absorption (at ca.
tropy, ϽrϾ, was recorded as a function of temperature 360 nm) and a fluorescence yield up to 0.25 in the visible
(Figure 4). At low temperatures (ca. 10 °C), the anisotropy range (ca. 470 nm). These spectral properties allow these
value (0.37) was close to the theoretical maximum (0.40), groups to be used as fluorescent labels with a variety of
indicating the absence of depolarizing rotational motions of lipid compounds.
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cause degradation was observed even if stored at –20 °C. Its sta-
bility increased considerably in the presence of trace amounts (ca.
1%) of 2,6-di-tert-butyl-4-methylphenol (BHT). Compound 1B is
stable for months if kept cool in the dark.
Experimental Section
General Remarks: Chemicals were obtained from commercial
sources, and used without further purification. All solvents were
freshly purified, distilled and deoxygenated thoroughly by argon-
bubbling prior to use. All reactions were carried out under the total
absence of oxygen in oven-dried Schlenk-type flasks. Analytical
thin-layer chromatography was performed on precoated silica gel
plates (Merck 60F254, 0.25 mm). Flash column chromatography
was carried out on silica gel (Merck, 230–400 mesh). HPLC analy-
sis was performed with an Agilent 1100 chromatograph equipped
with a C18 reversed-phase column and a diode array detector using
MeOH/H2O mixtures as eluents. Melting points were measured
with a Reichert–Kofler hot-stage microscope and are uncorrected.
Yields refer to the isolated pure compound. Elemental analyses of
all the compounds isolated herein were carried out with a Carlo
Erba CHN-1108 microanalyser. However, results are provided only
in those cases in which the experimental uncertainty is Ϯ0.4%. The
larger experimental uncertainty in some of the compounds de-
scribed here was attributed to incomplete elimination of water/or-
Data for all-(E)-1A: Isolated from the isomeric mixture by ex-
tracting the (1Z) isomer with diethyl ether. Yellow oil, m.p. 84 °C
(dec). Rf = 0.86 (hexane/EtOAc, 9:1). 1H NMR (300 MHz, CDCl3,
30 °C): δ = 6.74 (dd, J = 13.5, 10.8 Hz, 1 H, 2-H), 6.55–6.00 (m, 6
H, 1-H, 3-H to 7-H), 5.78 (dq, J = 13.5, 6.9 Hz, 1 H, 8-H), 1.77
(dd, J = 6.9, 1.2 Hz, 3 H, CH3) ppm. 13C NMR (50 MHz, CDCl3,
20 °C): δ = 137.7, 134.9, 134.0, 131.7, 131.3, 129.5, 128.7, 107.9,
18.5 ppm. FTIR (neat): νmax = 3069, 3013, 2928, 1595, 1445, 1309,
˜
1000, 941, 923, 751, 708, 688 cm–1. MS (EI, 70 eV): m/z (%) = 200
(11) (nominal mass, [M]+), 198 (11), 135 (26), 117 (17), 105 (12),
103 (17), 91 (77), 83 (42), 79 (36), 77 (41), 51 (29), 43 (100). Data
for (1Z,3E,5E,7E)-1A [deduced from its 4:1 mixture with all-(E)-
1A]: 1H NMR (300 MHz, CDCl3, 30 °C): δ = 6.65 (dd, J = 9.9,
7.2 Hz, 1 H, 2-H), 6.55–6.00 (m, 6 H, 1-H, 3-H to 7-H), 5.81 (dq, J
= 14.1, 7.2 Hz, 1 H, 8-H), 1.80 (dd, J = 7.2, 1.5 Hz, 3 H, CH3) ppm.
1
ganic solvent molecules. H and 13C NMR spectra were recorded
Hept-6-yn-1-ol (2a) was obtained by triple-bond zipper isomeriza-
tion of hept-2-yn-1-ol, as described previously.[55]
with a Varian Gemini-200 or an INOVA-300, -400 or -500 spec-
trometer. Chemical shifts are reported in parts per million (ppm)
using as internal reference the proton signal of the trace of unde-
uteriated solvent or the carbon signal of the deuteriated solvent: δ
= 7.26 and 77.0 ppm, respectively, in CDCl3. Abbreviations: s (sing-
let), d (doublet), t (triplet), q (quartet), quint (quintet), m (complex
multiplet). Carbon and proton assignments were based on COSY,
DEPT, HSQC and HMQC experiments. (E)/(Z) ratios were calcu-
Non-8-ynyl acetate (2b) was synthesized from non-2-yn-1-ol by zip-
per isomerization to non-8-yn-1-ol and subsequent acetic anhy-
dride/triethylamine esterification (overall yield 5.37 g, 83%), as de-
scribed previously.[56] Finally, 2b was purified by column
chromatography (silica gel, hexane/EtOAc, 4:1). Yellowish oil. Rf
1
= 0.56 (hexane/EtOAc, 4:1). H NMR (300 MHz, CDCl3, 30 °C):
δ = 4.04 (t, J = 6.7 Hz, 2 H, 1-H), 2.17 (td, J = 6.9, 2.6 Hz, 2 H,
7-H), 2.03 (s, 3 H, CH3), 1.93 (t, J = 2.6 Hz, 1 H, 9-H), 1.61 (m, 2
H, 2-H), 1.50 (m, 2 H, 6-H), 1.34 (m, 6 H, 3-H to 5-H) ppm. 13C
NMR (75 MHz, CDCl3, 30 °C): δ = 171.2 (CO), 84.6 (C-8), 68.1
(C-9), 64.5 (C-1), 28.7, 28.6, 28.5, 28.3 (C-2, C-4 to C-6), 25.7 (C-
1
lated from the relative integrals of characteristic H NMR signals.
IR spectra (in cm–1) were recorded with a Perkin–Elmer 681 or a
FT-Spectrum One spectrometer. Low-resolution mass spectra were
recorded by electron impact (70 eV) using a Hewlett–Packard 5973
spectrometer in direct injection mode or by electrospray ionization
using a Hewlett–Packard 1100 apparatus. High-resolution mass
spectra were also determined by electron impact (70 eV) in a Waters
VG AutoSpec EI apparatus (Peak Match, perfluoroquerosene as
internal standard). UV/Vis absorption spectra were registered on a
Varian CARY-3E or a Perkin–Elmer Lambda-2 spectrophotome-
ter. Steady-state corrected fluorescence intensity and anisotropy
(ϽrϾ) measurements were recorded with an SLM 8000D spectro-
fluorimeter.[22] Fluorescence quantum yields (Φf) were determined
by comparison of the corrected fluorescence spectra of diluted
solutions of the samples with that of quinine sulfate in 0.05 
H2SO4 (Φf = 0.51), using the expression of Parker and Rees.[48]
Large unilamellar vesicles (LUV) of 1,2-dimyristoyl-sn-glycero-3-
phosphocholine (DMPC) containing the amphiphilic compound
5Bb (molar ratio 200:1) were prepared by extrusion, as described
elsewhere.[49,50]
3), 21.0 (CH ), 18.3 (C-7) ppm. FTIR (neat): ν
= 3296, 2935,
˜
3
max
2859, 2095, 1739, 1464, 1366, 1242, 1042 cm–1. MS (EI, 70 eV):
m/z (%) = 182 (1) [M]+, 121 (2), 107 (18), 93 (29), 81 (100).
Methyl non-8-ynoate (2c)[57] was obtained from non-8-yn-1-ol by
Jones oxidation[58] to the corresponding carboxylic acid and subse-
quent esterification with MeOH/SOCl2; it was purified by column
chromatography (silica gel, hexane/EtOAc, 4:1). Overall yield:
1
2.50 g, 80%. Yellow oil. Rf = 0.55 (hexane/EtOAc, 4:1). H NMR
(300 MHz, CDCl3, 30 °C): δ = 3.63 (s, 3 H, CH3), 2.23 (t, J =
7.2 Hz, 2 H, 2-H), 2.10 (td, J = 6.6, 2.7 Hz, 2 H, 7-H), 1.90 (t, J =
2.7 Hz, 1 H, 9-H), 1.56 (q, J = 7.2 Hz, 2 H, 3-H), 1.46 (q, J =
6.6 Hz, 2 H, 6-H), 1.35–1.10 (m, 4 H, 4-H, 5-H) ppm. 13C NMR
(75 MHz, CDCl3, 30 °C): δ = 173.6 (CO), 84.0 (C-8), 68.0 (C-9),
51.0 (C-2), 35.6 (CH3), 28.3, 28.0, 27.9 (C-4 to C-6), 24.5 (C-3),
18.0 (C-7) ppm. FTIR (neat): νmax = 3296, 2938, 2860, 2117, 1739,
˜
1436, 1254, 1201, 1173, 1094, 1016, 879 cm–1. MS (EI, 70 eV): m/z
(%) = 168 (1) [M]+, 153 (3), 121 (5), 108 (31), 79 (79), 74 (100).
Starting Compounds: 1-Bromonona-1,3,5,7-tetraene (1A) and 1-
bromo-6-phenylhexa-1,3,5-triene (1B),[28] both 3:7 (1E)/(1Z) iso-
meric mixtures, were synthesized from all-(E)-hexa-2,4-dienal and
(E)-cinnamaldehyde, respectively, in four steps: 1) Vinylogation
(Horner–Wadsworth–Emmons reaction)[43,44,51] with the ylide from
triethyl phosphonoacetate,[52] yielding the corresponding all-(E) es-
ters with an additional (E) double bond; 2) reduction to the corre-
sponding unstable primary alcohols with DIBAL-H;[53] 3) oxi-
dation of the alcohols with MnO2[54] to the corresponding unstable
aldehydes all-(E)-octa-2,4,6-trienal[21] and all-(E)-5-phenylpenta-
2,4-dienal;[28] 4) the aldehydes were treated as soon as possible with
the ylide produced from (bromomethyl)triphenylphosphonium bro-
mide (Wittig reaction). Compound 1A, obtained in 72% overall
yield (fourth step: 654 mg, 80%), must be used immediately be-
Methyl undec-10-ynoate (2d) was obtained as described pre-
viously.[24,59]
Diethyl [(2E,4E)-5-phenylpenta-2,4-dienyl]phosphonate (6) was
synthesized as described previously.[40] 9-(tert-Butyldimethylsilyl-
oxy)non-2-ynal (7) was obtained from oct-7-yn-1-ol by OH protec-
tion with tert-butyldimethylsilyl chloride and subsequent reaction
of the protected compound with n-butyllithium and dimethylform-
amide as described previously.[41] Aldehyde 7 was purified by col-
umn chromatography (silica gel, hexane/EtOAc, 9:1). Overall yield:
2.02 g, 93%. Colorless oil. Rf = 0.50 (hexane/EtOAc, 9:1). 1H
NMR (300 MHz, CDCl3, 25 °C): δ = 0.04 (s, 6 H, Si(CH3)2), 0.89
(s, 9 H, SiC(CH3)3), 1.31–1.46 (m, 4 H, 6-H, 7-H), 1.56 (m, 4 H,
2290
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 2285–2295

Amphiphilic Lipids with Polyene and Phenylpolyene Groups
FULL PAPER
2-H, 5-H), 2.42 (td, J = 7.0, 0.6 Hz, 2 H, 4-H), 3.60 (t, J = 6.4 Hz, H), 6.40–6.00 (m, 5 H, 12-H to 16-H), 5.75 (dq, J = 15.3, 7.2 Hz,
2 H, 9-H), 9.18 (d, J = 0.6 Hz, 1 H, 1-H) ppm. 13C NMR (75 MHz,
1 H, 17-H), 5.56 (dt, J = 15.3, 2.4 Hz, 1 H, 10-H), 3.66 (s, 3 H,
CDCl3, 25 °C): δ = –4.9 (Si(CH3)2), 18.7 (C(CH3)3), 19.5 (C-4), CH3O), 2.33 (dt, J = 6.9, 2.4 Hz, 2 H, 7-H), 2.31 (t, J = 7.2 Hz, 2
26.3 (C(CH3)3), 25.6, 29.0 (C-6, C-7), 28.9 (C-8), 33.1 (C-5), 63.6
H, 2-H), 1.79 (dd, J = 6.9, 1.4 Hz, 3 H, 18-H), 1.70–1.30 (m, 8 H,
3-H to 6-H) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 174.0,
140.6, 134.4, 134.3, 131.7, 131.1, 130.8, 130.0, 111.0, 93.8, 80.4,
(C-9), 82.1 (C-2), 99.7 (C-3), 177.6 (C-1) ppm. FTIR (KBr): ν
˜
max
= 2932, 2858, 2275, 2231, 2202, 1710, 1673, 1472, 1385, 1360, 1255,
1100, 1002, 836, 776 cm–1. MS (ESI+): m/z
=
269.2
51.3, 33.8, 28.5, 28.40, 28.35, 24.7, 19.5 ppm. FTIR (KBr): ν
=
˜
max
[M + H]+. The starting alcohol oct-7-yn-1-ol was synthesized from
oct-3-yn-1-ol by triple-bond zipper isomerization to the terminal
position with Li/1,3-diaminopropane/tBuOK, as described pre-
viously.[41] Yield: 1.49 g, 85%. Pale yellow oil. 1H NMR (300 MHz,
3040, 2935, 2870, 2270, 1734, 1640, 1460, 999 cm–1. MS (EI, 70 eV):
m/z (%) = 286 (60) [M]+, 185 (4), 171 (9), 158 (40), 141 (56),
129(100), 115 (61), 105 (28), 91 (58), 77 (29). UV (CHCl3): λmax
(logε) = 347 (4.8), 329 (4.8), 315 nm (4.6). C19H26O2 (286.41):
CDCl3, 25 °C): δ = 1.31–1.46 (m, 4 H, 3-H, 4-H), 1.55 (m, 4 H, 2- calcd. C 79.68, H 9.15; found C 79.01, H 8.93.
H, 5-H), 1.94 (t, J = 2.7 Hz, 1 H, 8-H), 2.19 (td, J = 7.0, 2.7 Hz,
Methyl Icosa-12,14,16,18-tetraen-10-ynoate (3Ad): The 3:7 all-
2 H, 6-H), 3.64 (t, J = 6.6 Hz, 2 H, 1-H) ppm. 13C NMR (75 MHz,
CDCl3, 25 °C): δ = 18.7 (C-6), 25.6, 28.8 (C-3, C-4), 28.9 (C-5),
33.0 (C-2), 63.3 (C-1), 70.0 (C-8), 85.0 (C-7) ppm. FTIR (KBr):
(E)/(12Z,14E,16E,18E) isomeric mixture was obtained by coupling
between polyene 1A [3:7 all-(E)/(1Z,3E,5E,7E) isomeric mixture]
(270 mg, 1.35 mmol) and alkyne 2d (353 mg, 1.8 mmol). It was
purified by flash column chromatography (silica gel, hexane/
EtOAc, 9:1). Yield: 360 mg, 85%. Data for the all-(E)-3Ad isomer:
Yellow solid, m.p. 83–85 °C. Rf = 0.66 (hexane/EtOAc, 4:1). 1H
NMR (300 MHz, CDCl3, 25 °C): δ = 6.52 (dd, J = 15.3, 9.9 Hz, 1
ν
= 3305, 2935, 2855, 2115, 1458 1429, 1055, 1031, 999,
˜
max
901 cm–1. MS (ESI+): m/z = 127.1 [M + H]+, 149.1 [M + Na]+,
275.2 [2M + Na]+.
Synthesis of Polyenyne Compounds 3. General Procedure: Dieth-
ylamine (0.7 mL, 6.9 mmol), [Pd(PPh3)2Cl2] (70 mg, 0.1 mmol), H, 13-H), 6.32–6.05 (m, 5 H, 14-H to 18-H), 5.75 (dq, J = 15.3,
and CuI (66 mg, 0.34 mmol) were added (Schlenk flask, room tem-
perature, stirring, argon) to a freshly-prepared solution of bromo-
polyene 1, in the form of a 3:7 (1E)/(1Z) isomeric mixture
(1.35 mmol), and an alkyne 2 (1.8 mmol) in deoxygenated THF
(40 mL); the mixture was kept under these conditions for 3 h. After
solvent elimination, the residue was redissolved in CH2Cl2, the
solution was filtered through a short silica gel pad, and the isolated
crude product was purified by column chromatography. Com-
pounds 3 were in all cases formed as 3:7 (E)/(Z) isomeric mixtures.
Pure samples of the corresponding all-(E) isomers were separated
from the these mixtures by precipitation with pentane from a satu-
rated solution in CHCl3 or CH2Cl2.
7.2 Hz, 1 H, 19-H), 5.56 (dt, J = 15.3, 2.1 Hz, 1 H, 12-H), 3.66 (s,
3 H, CH3O), 2.33 (dt, J = 6.9, 2.1 Hz, 2 H, 9-H), 2.30 (t, J =
7.2 Hz, 2 H, 2-H), 1.79 (dd, J = 6.9, 1.2 Hz, 3 H, 20-H), 1.60 (quint,
J = 7.2 Hz, 2 H, 3-H), 1.50 (quint, J = 7.2 Hz, 2 H, 8-H), 1.41–
1.30 (m, 2 H, 4-H), 1.29 (m, 6 H, 5-H to 7-H) ppm. 13C NMR
(75 MHz, CDCl3, 25 °C): δ = 174.3, 140.7, 134.5, 134.4, 131.8,
131.3, 130.9, 130.1, 111.2, 94.2, 80.4, 51.4, 34.1, 29.1 (2 C), 28.9,
28.8, 28.7, 24.9, 19.7, 18.4 ppm. FTIR (KBr): ν
= 3017, 2929,
˜
max
2855, 2204, 1739, 1637, 1439, 1322, 1247, 1209, 1172, 1002,
730 cm–1. MS (EI, 70 eV): m/z (%) = 314 (16) [M]+, 157 (25), 143
(55), 129 (56), 117 (49), 105 (46), 91 (72), 83 (70), 74 (30), 67 (31),
55 (86), 41 (100). HRMS (peak matching): calcd. for C21H30O2
314.2246; found 314.2248. UV (CHCl3): λmax (logε) = 347 (4.8),
329 (4.8), 315 nm (4.6). UV (MeOH/H2O, 9:1): λmax = 310, 324
(max.), 340 nm. C21H30O2 (314.46): calcd. C 80.21, H 9.62; found
C 79.97, H 9.38.
Octadeca-10,12,14,16-tetraen-8-ynyl Acetate (3Ab): The 3:7 all-(E)/
(10Z,12E,14E,16E) isomeric mixture was obtained by coupling be-
tween polyene 1A [3:7 all-(E)/(1Z,3E,5E,7E) isomeric mixture]
(270 mg, 1.35 mmol) and alkyne 2b (328 mg, 1.8 mmol). It was
purified by flash column chromatography (silica gel, hexane/
EtOAc, 9:1). Yield: 356 mg, 90%. Data for all-(E)-3Ab: Yellowish
waxy solid. Rf = 0.64 (hexane/EtOAc, 4:1). 1H NMR (300 MHz,
CDCl3, 25 °C): δ = 6.53 (dd, J = 15.3, 9.9 Hz, 1 H, 11-H), 6.4–6.0
13-Phenyltrideca-8,10,12-trien-6-yn-1-ol (3Ba): The 3:7 all-(E)/
(8Z,10E,12E) isomeric mixture was obtained by coupling between
polyene 1B [3:7 all-(E)/(1Z,3E,5E) isomeric mixture] (317 mg,
1.35 mmol) and alkyne 2a (202 mg, 1.8 mmol). It was purified by
(m, 5 H, 12-H to 16-H), 5.75 (dq, J = 15.3, 7.2 Hz, 1 H, 17-H), column chromatography (silica gel, hexane/EtOAc, 4:1). Yield:
5.56 (dt, J = 15.3, 2.4 Hz, 1 H, 10-H), 4.06 (t, J = 6.6 Hz, 2 H, 1- 287 mg, 80%. Data for the all-(E)-3Ba isomer: Yellowish waxy so-
H), 2.34 (dt, J = 6.6, 2.4 Hz, 2 H, 7-H), 2.05 (s, 3 H, CH3CO), 1.80
(dd, J = 6.9, 1.2 Hz, 3 H, 18-H), 1.64 (quint, J = 6.9 Hz, 2 H, 2-
H), 1.60 (quint, J = 6.9 Hz, 2 H, 6-H), 1.50–1.30 (m, 6 H, 3-H to
5-H) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 171.0, 140.6,
134.5, 134.4, 131.8, 131.2, 130.8, 130.0, 111.1, 93.9, 80.4, 64.5,
28.71 (2 C), 28.69, 28.6, 28.5, 25.7, 20.9, 19.6, 18.3 ppm. FTIR
lid. Rf = 0.51 (hexane/EtOAc, 2:1). 1H NMR (300 MHz, CDCl3,
30 °C): δ = 7.38 (m, 2 H, Ho), 7.29 (m, 2 H, Hm), 7.22 (m, 1 H,
Hp), 6.81 (dd, J = 15.6, 9.8 Hz, 1 H, 12-H), 6.60 (dd, J = 15.4,
10.0 Hz, 1 H, 9-H), 6.59 (d, J = 15.6 Hz, 1 H, 13-H), 6.39 (m, 2
H, 10-H, 11-H), 5.64 (dt, J = 15.4, 2.0 Hz, 1 H, 8-H), 3.67 (t, J =
5.5 Hz, 2 H, 1-H), 2.38 (td, J = 6.7, 2.0 Hz, 2 H, 5-H), 1.70–1.45
(m, 6 H, 2-H to 4-H) ppm.13C NMR (CDCl3, 75 MHz, 30 °C): δ
= 140.6 (C-9), 137.2 (Ci), 134.3 (C-11), 132.5 (C-10), 133.7 (C-13),
128.7 (C-12), 128.6 (Cm), 127.7 (Cp), 126.4 (Co), 111.9 (C-8), 94.2
(C-6), 80.5 (C-7), 62.8 (C-1), 32.3 (C-2), 28.5 (C-4), 25.0 (C-3), 19.7
(KBr): νmax = 3050, 2928, 2856, 2200, 1731, 1370, 1249, 1042, 1004,
˜
762 cm–1. MS (EI, 70 eV): m/z (%) = 300 (100) [M]+, 285 (2), 199
(4), 183 (10), 169 (20), 155 (45), 143 (91), 129 (94), 115 (54), 105
(32). UV (CHCl3): λmax (logε) = 347 (4.8), 329 (4.8), 315 nm (4.6).
C20H28O2 (300.44): calcd. C 79.96, H 9.39; found C 79.67, H 9.65.
(C-5) ppm. FTIR (KBr): νmax = 3435, 3014, 2927, 2855, 1632, 1049,
˜
995, 746, 688 cm–1. MS (EI, 70 eV): m/z (%) = 266 (84) [M]+, 205
(16), 191 (50), 179 (100), 165 (67), 152 (26), 141 (23), 128 (27), 115
(58), 91 (68), 77 (15). HRMS (peak matching): calcd. for C19H22O
266.1671; found 266.1667. UV (MeOH): λmax (logε) = 321 (4.64),
335 (4.76), 353 nm (4.72).
Methyl Octadecen-10,12,14,16-tetraen-8-ynoate (3Ac): The 3:7 all-
(E)/(10Z,12E,14E,16E) isomeric mixture was obtained by coupling
between polyene 1A [3:7 all-(E)/(1Z,3E,5E,7E) isomeric mixture]
(270 mg, 1.35 mmol) and alkyne 2c (303 mg, 1.8 mmol). It was
purified by flash column chromatography (silica gel, hexane/
EtOAc, 9:1). Yield: 336 mg, 87%. Data for the all-(E)-3Ac isomer:
Yellowish waxy solid. Rf = 0.72 (hexane/EtOAc, 4:1). 1H NMR
15-Phenylpentadeca-10,12,14-trien-8-ynyl Acetate (3Bb): The 3:7
all-(E)/(10Z,12E,14E) isomeric mixture was obtained by coupling
(300 MHz, CDCl3, 25 °C): δ = 6.53 (dd, J = 15.3, 9.9 Hz, 1 H, 11- between polyene 1B [3:7 all-(E)/(1Z,3E,5E) isomeric mixture]
Eur. J. Org. Chem. 2007, 2285–2295
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2291

E. Quesada, J. Delgado, V. Hornillos, A. U. Acuña, F. Amat-Guerri
FULL PAPER
(317 mg, 1.35 mmol) and alkyne 2b (328 mg, 1.8 mmol). It was
purified by flash column chromatography (silica gel, hexane/
EtOAc, 4:1). Yield: 387 mg, 85%. Data for the all-(E)-3Bb isomer:
(10E,12E,14E,16E)/(10Z,12E,14E,16E) isomeric mixture] (100 mg,
0.33 mmol) after Zn reduction and precipitation with pentane. Pale
1
yellow oil. Yield: 30 mg, 30%. Rf = 0.68 (hexane/EtOAc, 4:1). H
1
Yellow solid. Rf = 0.63 (hexane/EtOAc, 4:1). H NMR (500 MHz,
NMR (300 MHz, CDCl3, 30 °C): δ = 6.48 (m, 1 H, 11-H), 6.30–
6.10 (m, 5 H, 10-H, 12-H to 16-H), 6.04 (m, 1 H, 9-H), 5.73 (dq,
J = 15.3, 6.9 Hz, 1 H, 17-H), 5.44 (dt, J = 10.2, 7.8 Hz, 1 H, 8-H),
4.05 (t, J = 6.6 Hz, 2 H, 1-H), 2.2 (dt, J = 6.9, 6.6 Hz, 2 H, 7-H),
2.04 (s, 3 H, CH3CO), 1.79 (dd, J = 6.6, 1.2 Hz, 3 H, 18-H), 1.62
CDCl3, 25 °C): δ = 7.40 (d, J = 7.5 Hz, 2 H, Ho), 7.31 (t, J =
7.5 Hz, 2 H, Hm), 7.22 (t, J = 7.5 Hz, 1 H, Hp), 6.80 (dd, J = 15.5,
9.8 Hz, 1 H, 14-H), 6.59 (dd, J = 15.4, 10.0 Hz, 1 H, 11-H), 6.58
(d, J = 15.5 Hz, 1 H, 15-H), 6.43 (dd, J = 14.7, 9.8 Hz, 1 H, 13-
H), 6.35 (dd, J = 14.7, 10.0 Hz, 1 H, 12-H), 5.64 (dt, J = 15.4, (quint, J = 6.9 Hz, 2 H, 2-H), 1.45–1.25 (m, 8 H, 3-H to 6-H) ppm.
2.1 Hz, 1 H, 10-H), 4.06 (t, J = 6.9 Hz, 2 H, 1-H), 2.36 (td, J = 13C NMR (75 MHz, CDCl3, 30 °C): δ = 171.1, 133.2, 133.1, 132.85,
7.0, 2.1 Hz, 2 H, 7-H), 2.05 (s, 3 H, CH3), 1.64 (quint, J = 6.9 Hz,
132.79, 132.4, 132.0, 130.6, 130.2, 128.9, 128.0, 64.6, 29.6, 29.1
2 H, 2-H), 1.55 (m, 2 H, 6-H), 1.50–1.30 (m, 6 H, 3-H to 5-H) ppm. (ϫ2), 28.6, 27.9, 25.9, 21.0, 18.4 ppm. UV (CHCl3): λmax (logε) =
13C NMR (75 MHz, CDCl3, 25 °C): δ = 171.2 (CO), 140.5 (C-11),
137.2 (Ci), 134.3 (C-13), 133.7 (C-15), 132.5 (C-12), 128.7 (C-14),
128.6 (Cm), 127.7 (Cp), 126.4 (Co), 112.0 (C-10), 94.5 (C-8), 80.4
(C-9), 64.6 (C-1), 28.8, 28.7, 28.6, 28.5 (C-2, C-4 to C-6), 25.8 (C-
353 (4.85), 335 (4.86), 319 nm (4.63).
Methyl 15-Phenylpentadeca-8,10,12,14-tetraenoate (4Bc): The 1:1
(8Z,10E,12E,14E)/(8Z,10Z,12E,14E) isomeric mixture was ob-
tained by Zn reduction of 3Bc [1:1 all-(E)/(10Z,12E,14E) isomeric
mixture] (106 mg, 0.33 mmol); it was purified by column
chromatography (silica gel, hexane/EtOAc, 4:1 as eluent). Yield:
86 mg, 80%. Yellowish waxy oil. Rf = 0.57 (hexane/EtOAc, 4:1).
1H NMR (300 MHz, CDCl3, 30 °C): δ = 7.41 (d, J = 7.4 Hz, 1 H,
Ho of (8Z,10Z)), 7.40 (d, J = 7.4 Hz, 1 H, Ho of (8Z,10E)), 7.32
(t, J = 7.4 Hz, 1 H, Hm of (8Z,10Z)), 7.31 (t, J = 7.3 Hz, 1 H, Hm
of (8Z,10Z)), 7.22 (t, J = 7.4 Hz, 0.5 H, Hp of (8Z,10Z)), 7.21 (t,
J = 7.4 Hz, 0.5 H, Hp of (8Z,10E)), 6.86 (m, 1 H, 14-H), 6.59 (d,
J = 15.2 Hz, 0.5 H, 15-H of (8Z,10Z)), 6.54 (d, J = 15.3 Hz, 0.5
H, 15-H of (8Z,10E)), 6.56–6.24 (m, 4 H, 10-H to 13-H), 6.09 (m,
1 H, 9-H), 5.57 (dt, J = 10.7, 7.5 Hz, 0.5 H, 8-H of (8Z,10Z)), 5.47
(dt, J = 10.4, 7.5 Hz, 0.5 H, 8-H of (8Z,10E)), 3.67 (s, 3 H, CH3),
2.31 (t, J = 7.5 Hz, 2 H, 2-H), 2.22 (q, J = 7.5 Hz, 2 H, 7-H), 1.64
(quint, J = 7.5 Hz, 2 H, 3-H), 1.48–1.25 (m, 6 H, 4-H to 6-H) ppm.
13C NMR (75 MHz, CDCl3, 30 °C): δ = 174.1 (CO), 137.4, 137.3,
133.8, 133.7, 133.6, 133.0, 132.9, 132.7, 132.6, 132.2, 129.1, 129.0,
128.8, 128.6 (C-8 to C-13, C-15), 128.5 (Cm), 127.4, 127.3 (Cp),
126.3, 126.2 (Co), 124.8, 123.7 (C-14), 51.3 (CH3), 34.0 (C-2), 29.3,
29.2, 28.9, 28.8, 27.8, 27.4 (C-4 to C-7), 24.8 (C-3) ppm. MS (EI,
70 eV): m/z (%) = 324 (72) [M]+, 195 (21), 181 (73), 167 (47), 155
(20), 141 (27), 128 (26), 117 (59), 104 (25), 91 (100).
3), 21.0 (CH ), 19.7 (C-7) ppm. FTIR (KBr): ν
= 3436, 3014,
˜
3
max
2928, 2847, 2195, 1734, 1631, 1243, 1001, 926, 890, 746, 689 cm–1.
MS (ESI+): m/z = 337.3 [M + H]+. MS (EI, 70 eV): m/z (%) = 336
(86) [M]+, 205 (17), 193 (53), 179 (100), 165 (52), 152 (17), 141
(23), 129 (30), 115 (53), 91 (70). HRMS (peak matching): calcd. for
C23H28O2 336.2089; found 336.2080. UV (CHCl3): λmax = 334, 346
(max.), 358 nm. UV (MeOH/H2O, 9:1): λmax = 332, 336 (max.),
354 nm.
Methyl 15-Phenylpentadeca-10,12,14-trien-8-ynoate (3Bc): The 3:7
all-(E)/(10Z,12E,14E) isomeric mixture was obtained by coupling
between polyene 1B [3:7 all-(E)/(1Z,3E,5E) isomeric mixture]
(317 mg, 1.35 mmol) and alkyne 2c (303 mg, 1.8 mmol). It was
purified by flash column chromatography (silica gel, hexane/
EtOAc, 4:1). Yield: 371 mg, 80%. Data for the all-(E)-3Bc isomer:
Brown oil. Rf = 0.59 (hexane/EtOAc, 4:1). 1H NMR (300 MHz,
CDCl3, 30 °C): δ = 7.40 (d, J = 7.5 Hz, 2 H, Ho), 7.31 (t, J =
7.5 Hz, 2 H, Hm), 7.22 (t, J = 7.5 Hz, 1 H, Hp), 6.80 (dd, J = 15.5,
9.8 Hz, 1 H, 14-H), 6.59 (dd, J = 15.4, 10.0 Hz, 1 H, 11-H), 6.58
(d, J = 15.5 Hz, 1 H, 15-H), 6.43 (dd, J = 14.7, 9.8 Hz, 1 H, 13-
H), 6.35 (dd, J = 14.7, 10.0 Hz, 1 H, 12-H), 5.64 (dt, J = 15.4,
2.1 Hz, 1 H, 10-H), 3.67 (s, 3 H, CH3), 2.35 (td, J = 6.9, 2.0 Hz, 2
H, 7-H), 2.31 (t, J = 7.5 Hz, 2 H, 2-H), 1.74–1.30 (m, 8 H, 3-H to
6-H) ppm. 13C NMR (75 MHz, CDCl3, 30 °C): δ = 173.7 (CO),
140.5 (C-11), 137.2 (Ci), 134.3 (C-13), 133.7 (C-15), 132.5 (C-12),
128.7 (C-14), 128.6 (Cm), 127.7 (Cp), 126.4 (Co), 112.0 (C-10), 94.2
(C-8), 80.4 (C-9), 51.1 (C-2), 33.7 (CH3), 28.4, 28.3, 28.2 (C-4, C-
5, C-6), 24.6 (C-3), 19.5 (C-7) ppm. MS (ESI+): 323.5 [M + H]+.
UV (CHCl3): λmax = 334, 346 (max.), 358 nm.
all-(E)-Octadeca-8,10,12,14,16-pentaenyl Acetate (5Ab): Acetate
5Ab was obtained by reduction/isomerization of 3Ab (100 mg,
0.33 mmol). It was purified by column chromatography (silica gel,
hexane/EtOAc, 4:1). Yield: 87 mg, 87%. Yellow waxy solid. Rf =
0.68 (hexane/EtOAc, 4:1). 1H NMR (300 MHz, CDCl3, 30 °C): δ
= 6.30–6.10 (m, 8 H, 9-H to 16-H), 5.72 (dq, J = 15.3, 7.2 Hz, 1
H, 17-H), 5.7 (m, 1 H, 8-H), 4.05 (t, J = 6.9 Hz, 2 H, 1-H), 2.1 (dt,
J = 7.2, 6.9 Hz, 2 H, 7-H), 2.04 (s, 3 H, CH3CO), 1.78 (dd, J =
7.2, 1.2 Hz, 3 H, 18-H), 1.61 (quint, J = 6.9 Hz, 2 H, 2-H), 1.39
(quint, J = 6.9 Hz, 2 H, 6-H), 1.32 (m, 6 H, 3-H to 5-H) ppm. 13C
NMR (75 MHz, CDCl3, 30 °C): δ = 171.0, 135.4, 132.9, 132.8,
132.5, 132.4, 132.0, 130.9, 130.7, 130.66, 129.9, 64.6, 32.8, 29.2,
Synthesis of Polyene Compounds 4 and 5. General Procedure: A
slurry of zinc power (3 g, 46 mmol), freshly activated under Ar,
with Cu(OAc)2·H2O (0.3 g, 1.51 mmol) and AgNO3 (0.3 g,
1.75 mmol) (Boland procedure)[32,60] in MeOH/H2O (1:1, 6 mL)
was added to a solution of each polyenyne 3Ab–d, 3Ba–c [all 3:7
(E)/(Z) isomeric mixtures] (0.33 mmol) in MeOH (1 mL) at room
temperature and with stirring. After 24 h, the reaction mixture was
filtered through Celite with CH2Cl2 and the subsequent work up
afforded the corresponding reduced products 4 as 3:7 (Z,E,..)/
(Z,Z,..) mixtures of isomers with a (Z) double bond in the position
of the original triple bond. A solution of each crude product in
hexane (200 mL) was refluxed for 15 min under Ar with iodine-
saturated hexane (60 µL) and the solution was filtered through a
short silica gel pad while hot. After solvent evaporation, the corre-
sponding all-(E) isomer 5 was purified by column chromatography
and subsequent precipitation with pentane from a CH2Cl2 solution
and/or by crystallization from acetone at –20 °C.
29.1, 29.0, 28.6, 25.8, 21.0, 18.4 ppm. FTIR (neat): ν
= 3015,
˜
max
2926, 2854, 1739, 1466, 1367, 1247, 1002 cm–1. MS (EI, 70 eV):
m/z (%) = 302 (34) [M]+, 290 (4), 277 (16), 185 (3), 173 (4), 159
(12), 147 (9), 143 (22), 131 (20), 117 (36), 105 (38), 91 (63), 81 (56),
67 (41), 55 (59), 43 (100). UV (CHCl3): λmax (logε) = 351 (4.81),
334 (4.83), 319 nm (4.63). UV (hexane): λmax (logε) = 344 (4.84),
327 (4.85), 311 nm (4.66).
Methyl all-(E)-Octadeca-8,10,12,14,16-pentaenoate (5Ac): Com-
pound 5Ac was obtained by reduction/isomerization of 3Ac (95 mg,
0.33 mmol). It was purified by column chromatography (silica gel,
hexane/EtOAc, 4:1). Yield: 78 mg, 82%. Yellowish waxy solid. Rf
1
(8Z,10E,12E,14E,16E)-Octadeca-8,10,12,14,16-pentaenyl Acetate
(4Ab): The (Z,E,E,E,E) isomer was obtained from 3Ab [3:7
= 0.7 (hexane/EtOAc, 4:1). H NMR (400 MHz, CDCl3, 30 °C): δ
= 6.30–6.00 (m, 8 H, 9-H to 16-H), 5.80–5.60 (m, 2 H, 8-H, 17-H),
2292
www.eurjoc.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 2285–2295

Amphiphilic Lipids with Polyene and Phenylpolyene Groups
FULL PAPER
3.65 (s, 3 H, CH3O), 2.29 (t, J = 7.2 Hz, 2 H, 2-H), 2.1 (dt, J =
7.2, 6.9 Hz, 2 H, 7-H), 1.78 (dd, J = 6.9, 1.5 Hz, 3 H, 18-H), 1.60
10-H, 11-H), 6.11 (m, 1 H, 9-H), 5.74 (dt, J = 14.4, 7.0 Hz, 1 H,
8-H), 4.05 (t, J = 6.8 Hz, 2 H, 1-H), 2.12 (q, J = 7.0 Hz, 2 H, 7-
(quint, J = 7.2 Hz, 2 H, 3-H), 1.45–1.20 (m, 6 H, 4-H to 6-H) ppm. H), 2.04 (s, 3 H, CH3), 1.62 (q, J = 6.8 Hz, 2 H, 2-H), 1.33 (m, 8
13C NMR (75 MHz, CDCl3, 30 °C): δ = 174.1, 135.1, 132.78, H, 3-H to 6-H) ppm. 13C NMR (75 MHz, CDCl3, 30 °C): δ = 171.2
132.75, 132.4, 132.35, 132.0, 130.9, 130.7, 130.6, 129.7, 51.2, 33.9,
32.7, 29.0, 28.9, 28.7, 24.8, 18.2 ppm. FTIR (neat): ν = 2927,
(CO), 137.5 (Ci), 135.9 (C-8), 133.7, 133.6 (C-11, C-12), 132.3 (C-
13), 131.9 (C-15), 130.7, 130.6 (C-9, C-10), 129.3 (C-14), 128.6
(Cm), 127.3 (Cp), 126.3 (Co), 64.6 (C-1), 33.7 (C-7), 32.8, 29.2, 29.0,
˜
max
2830, 1737, 1436, 1175, 1003 cm–1. MS (EI, 70 eV): m/z (%) = 288
(1) [M]+, 277 (5), 199 (3), 179 (3), 171 (13), 157 (6), 141 (22), 129 28.8 (C-2, C-4, C-5, C-6), 25.8 (C-3), 21.0 (CH3) ppm. UV
(21), 121 (17), 107 (26), 95 (59), 83 (55), 74 (38), 55 (100). UV
(CHCl3): λmax (logε) = 351 (4.81), 334 (4.83), 319 nm (4.63). UV
(hexane): λmax (logε) = 344 (4.84), 327 (4.85), 311 nm (4.66).
(CHCl3): λmax = 332, 347 (max.), 365 nm.
Hydrolysis of Polyenyne Esters 3 and Polyene Esters 5. General Pro-
cedure: A solution of a polyenyne ester [3Ab,d, 3Bb,c, pure all-(E)
isomers] or of a polyene ester (5Ab,c, 5Bc) (0.6 mmol) in EtOH
(7 mL) with potassium hydroxide (0.17 g, 3 mmol) was stirred at
room temperature for 4 h. The reaction mixture was then acidified
with 5% aqueous HCl, poured into water, extracted with dichloro-
methane (3ϫ20 mL), and the organic extract washed with water.
Work up yielded a crude product that was purified by column
chromatography (silica gel, hexane/EtOAc, 4:1). When the (E)/(Z)
isomeric mixtures of polyenyne esters 3 were hydrolyzed instead,
pure all-(E) isomers 3Ae,g and 3Be,f were obtained from the reac-
tion mixtures by precipitation with pentane or hexane or, in the
case of compounds 3A, by isomerization with traces of iodine, as
before. Compounds 3B could not be isomerized by the latter treat-
ment.
Methyl all-(E)-Icosa-10,12,14,16,18-pentaenoate (5Ad): Compound
5Ad was obtained by reduction/isomerization of 3Ad (104 mg,
0.33 mmol). It was purified by column chromatography (silica gel,
hexane/EtOAc, 4:1). Yield: 99 mg, 95%. Bright yellowish crystals,
m.p. 113–115 °C. Rf = 0.70 (hexane/EtOAc, 4:1). 1H NMR
(300 MHz, CDCl3, 30 °C): δ = 6.30–6.00 (m, 8 H, 11-H to 18-H),
5.80–5.65 (m, 2 H, 10-H, 19-H), 3.66 (s, 3 H, CH3O), 2.30 (t, J =
7.2 Hz, 2 H, 2-H), 2.09 (dd, J = 14.1, 6.9 Hz, 2 H, 2-H), 1.78 (d, J
= 6.9 Hz, 3 H, 20-H), 1.62 (quint, J = 7.2 Hz, 2 H, 3-H), 1.38
(quint, J = 6.9 Hz, 2 H, 8-H), 1.29 (br. s, 8 H, 4-H to 7-H) ppm.
13C NMR (75 MHz, CDCl3, 30 °C): δ = 135.6 (C-10), 132.9, 132.8,
132.4, 132.41, 132.0, 130.8, 130.7, 130.6, 129.9 (C-11 to C-19), 51.5
(CH3O), 34.1 (C-2), 32.9 (C-9), 29.26 (ϫ2), 29.17, 29.10 (ϫ2) (C-
4 to C-8), 24.9 (C-3), 18.4 (C-20) ppm. FTIR (KBr): ν
= 3011,
˜
max
all-(E)-Octadeca-10,12,14,16-tetraen-8-yn-1-ol (3Ae): Compound
3Ae was obtained by hydrolysis of all-(E)-3Ab (180 mg, 0.6 mmol).
Yield: 135 mg, 87%. Yellow waxy solid. Rf = 0.24 (hexane/EtOAc,
2921, 2848, 1737, 1471, 1436, 1243, 1207, 1176, 1003 cm–1. MS (EI,
70 eV): m/z (%) = 316 (5) [M]+, 277 (2), 199 (7), 169 (10), 157 (11),
145 (18), 131 (23), 125 (21), 117 (23), 105 (30), 91 (47), 55 (100).
UV (CHCl3): λmax (logε) = 351 (4.81), 334 (4.83), 319 nm (4.63).
UV (hexane): λmax (logε) = 344 (4.84), 327 (4.85), 311 nm (4.66).
C21H32O2 (316.48): calcd. C 79.70, H 10.19; found C 79.60, H
10.40.
1
4:1). H NMR (300 MHz, CDCl3, 30 °C): δ = 6.52 (dd, J = 15.3,
9.9 Hz, 1 H, 11-H), 6.32–6.05 (m, 5 H, 12-H to 16-H), 5.75 (dq, J
= 15.3, 7.2 Hz, 1 H, 17-H), 5.56 (dt, J = 15.3, 2.4 Hz, 1 H, 10-H),
3.63 (t, J = 6.9 Hz, 2 H, 1-H), 2.33 (dt, J = 6.9, 2.4 Hz, 2 H, 7-H),
1.79 (dd, J = 6.9, 1.5 Hz, 3 H, 18-H), 1.58 (quint, J = 6.9 Hz, 2 H,
2-H), 1.55 (quint, J = 6.9 Hz, 2 H, 6-H), 1.5–1.3 (m, 6 H, 3-H to
5-H) ppm. 13C NMR (75 MHz, CDCl3, 30 °C): δ = 140.6, 134.5,
134.4, 131.2, 130.8, 130.0, 111.0, 94.1, 80.4, 62.9, 32.7, 28.9, 28.8,
all-(E)-13-Phenyltrideca-6,8,10,12-tetraen-1-ol (5Ba): Compound
5Ba was obtained by reduction/isomerization of 3Ba (88 mg,
0.33 mmol). It was purified by column chromatography (silica gel,
hexane/EtOAc, 4:1). Yield: 80 mg, 90%. Yellowish waxy solid. Rf
28.7, 25.6, 19.7, 18.4 ppm. FTIR (KBr): ν
= 3435, 2926, 2850,
˜
max
1630, 1467, 1065, 998, 749 cm–1. MS (EI, 70 eV): m/z (%) = 258
(30) [M]+, 199 (3), 169 (7), 157 (34), 143 (98), 129 (100), 115 (57),
91 (59), 79 (29). UV (CHCl3): λmax (logε) = 347 (4.80), 329 (4.80),
315 nm (4.62). C18H26O (258.40): calcd. C 83.67, H 10.14; found C
83.25, H 10.34.
1
= 0.13 (hexane/EtOAc, 4:1). H NMR (300 MHz, CDCl3, 30 °C):
δ = 7.39 (d, J = 7.3 Hz, 2 H, Ho), 7.30 (m, 2 H, Hm), 7.20 (m, 1
H, Hp), 6.83 (ddd, J = 15.5, 6.7, 3.6 Hz, 1 H, 12-H), 6.53 (d, J =
15.5 Hz, 1 H, 13-H), 6.37 (dd, J = 6.7, 3.6 Hz, 2 H, 10-H, 11-H),
6.23 (m, 2 H, 8-H, 9-H), 6.11 (m, 1 H, 7-H), 5.74 (dt, J = 14.8,
7.0 Hz, 1 H, 6-H), 3.64 (t, J = 6.4 Hz, 2 H, 1-H), 2.14 (dt, J = 7.0,
6.8 Hz, 2 H, 5-H), 1.56 (m, 2 H, 2-H), 1.50–1.30 (m, 4 H, 3-H, 4-
H) ppm. 13C NMR (CDCl3, 75 MHz, 30 °C): δ = 137.5 (Ci), 135.7
(C-6), 133.7, 133.6 (C-9, C-10), 132.4 (C-11), 131.9 (C-13), 130.8,
130.7 (C-7, C-8), 129.3 (C-12), 128.6 (Cm), 127.3 (Cp), 126.2 (Co),
62.9 (C-1), 32.8 (C-5), 32.6 (C-2), 29.0 (C-4), 25.3 (C-3) ppm. FTIR
all-(E)-Icosa-12,14,16,18-tetraen-10-ynoic Acid (3Ag): Compound
3Ag was obtained by hydrolysis of all-(E)-3Ad (188 mg, 0.6 mmol).
Yield: 177 mg, 98%. Yellowish waxy solid. Rf = 0.65 (CH2Cl2/
EtOH, 9:1). 1H NMR (300 MHz, [D6]acetone, 30 °C): δ = 10.6 (br.
s, 1 H, CO2H), 6.69 (dd, J = 15.3, 10.2 Hz, 1 H, 13-H), 6.60–6.20
(m, 5 H, 14-H to 18-H), 5.96 (dq, J = 15.3, 6.9 Hz, 1 H, 19-H),
5.79 (dt, J = 15.3, 2.4 Hz, 1 H, 12-H), 2.49 (dt, J = 6.9, 2.4 Hz, 2
H, 9-H), 2.43 (t, J = 7.2 Hz, 2 H, 2-H), 1.91 (d, J = 6.9 Hz, 3 H,
20-H), 1.74 (m, 2 H, 3-H), 1.70–1.45 (m, 10 H, 4-H to 8-H) ppm.
13C NMR (75 MHz, [D6]acetone): δ = 173.6, 138.5, 135.2, 134.9,
131.8, 130.1, 129.0, 108.9, 93.6, 80.2, 33.1, 28.72, 28.48, 28.45,
(KBr): νmax = 3349, 3021, 2930, 2857, 1673, 1448, 1072, 1001, 746,
˜
690 cm–1. MS (EI, 70 eV): m/z (%) = 268 (100) [M]+, 195 (16), 181
(62), 167 (35), 155 (26), 141 (25), 128 (28), 117 (56), 104 (29), 91
(94), 77 (24). HRMS (peak matching): calcd. for C19H24O
268.1827; found 268.1823. UV (EtOH): λmax (logε) = 325 (4.95),
340 (5.10), 360 nm (5.03). UV (DMSO): λmax (logε) = 333 (4.87),
349 (5.02), 368 nm (4.94).
28.44, 24.6, 19.0, 17.4 ppm. FTIR (KBr): νmax = 3435, 3060, 2929,
˜
2860, 2126, 1705, 1001 cm–1. MS (EI, 70 eV): m/z (%) = 300 (45)
[M]+, 199 (3), 185 (5), 171 (9), 157 (39), 143 (100), 129 (90), 115
(46), 105 (27), 91 (52), 79 (26). UV (MeOH/H2O, 9:1): λmax = 310,
324, 340 nm (max.). C18H26O (300.44): calcd. C 79.96, H 9.39;
found C 79.60, H 9.99.
all-(E)-15-Phenylpentadeca-8,10,12,14-tetraenyl Acetate (5Bb):
Compound 5Bb was obtained by reduction/isomerization of 3Bb
(111 mg, 0.33 mmol). It was purified by column chromatography
(silica gel, hexane/EtOAc, 4:1). Yield: 103 mg, 92%. Waxy oil. Rf
1
= 0.60 (hexane/EtOAc, 4:1). H NMR (300 MHz, CDCl3, 30 °C): all-(E)-15-Phenylpentadeca-10,12,14-trien-8-yn-1-ol (3Be): Com-
δ = 7.38 (m, 2 H, Ho), 7.30 (m, 2 H, Hm), 7.20 (m, 1 H, Hp), 6.83
(ddd, J = 15.5, 6.6, 3.2 Hz, 1 H, 14-H), 6.53 (d, J = 15.5 Hz, 1 H,
15-H), 6.37 (dd, J = 6.6, 3.2 Hz, 2 H, 12-H, 13-H), 6.24 (m, 2 H,
pound 3Be was obtained by hydrolysis of all-(E)-3Bb (202 mg,
0.6 mmol). Yield: 175 mg, 99%. Yellowish waxy solid. Rf = 0.24
(hexane/EtOAc, 4:1). 1H NMR (300 MHz, CDCl3, 30 °C): δ = 7.39
Eur. J. Org. Chem. 2007, 2285–2295
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2293

E. Quesada, J. Delgado, V. Hornillos, A. U. Acuña, F. Amat-Guerri
(d, J = 7.3 Hz, 2 H, Ho), 7.31 (t, J = 7.3 Hz, 2 H, Hm), 7.22 (t, J isomerization to 5Bc and subsequent hydrolysis. Yield: 167 mg,
FULL PAPER
1
= 7.5 Hz, 1 H, Hp), 6.81 (dd, J = 15.5, 9.8 Hz, 1 H, 14-H), 6.59
(dd, J = 15.4, 10.0 Hz, 1 H, 11-H), 6.58 (d, J = 15.5 Hz, 1 H, 15-
H), 6.43 (dd, J = 14.7, 9.8 Hz, 1 H, 13-H), 6.35 (dd, J = 14.7,
90%. Yellow amorphous solid. Rf = 0.13 (hexane/EtOAc, 4:1). H
NMR (300 MHz, CDCl3, 30 °C): δ = 7.39 (m, 2 H, Ho), 7.27 (m,
2 H, Hm), 7.17 (m, 1 H, Hp), 6.80 (ddd, J = 15.5, 6.6, 3.2 Hz, 1 H,
10.0 Hz, 1 H, 12-H), 5.64 (dt, J = 15.4, 2.4 Hz, 1 H, 10-H), 3.65 14-H), 6.49 (d, J = 15.5 Hz, 1 H, 15-H), 6.34 (dd, J = 6.6, 3.2 Hz,
(t, J = 6.5 Hz, 2 H, 1-H), 2.36 (td, J = 6.9, 2.4 Hz, 2 H, 7-H), 1.63–
2 H, 12-H, 13-H), 6.20 (m, 2 H, 10-H, 11-H), 6.07 (m, 1 H, 9-H),
5.70 (dt, J = 14.4, 7.0 Hz, 1 H, 8-H), 2.32 (t, J = 7.2 Hz, 2 H, 2-
1.49 (m, 4 H, 2-H, 6-H), 1.37 (m, 6 H, 3-H to 5-H) ppm. 13C NMR
(75 MHz, CDCl3, 30 °C): δ = 140.5 (C-11), 137.2 (Ci), 134.2 (C- H), 2.08 (q, J = 7.0 Hz, 2 H, 7-H), 1.61 (q, J = 7.2 Hz, 2 H, 3-H),
13), 133.6 (C-15), 132.5 (C-12), 128.7 (C-14), 128.6 (Cm), 127.7
(Cp), 126.4 (Co), 112.0 (C-10), 94.5 (C-8), 80.4 (C-9), 63.0 (C-1),
32.7 (C-2), 28.9, 28.8, 28.7 (C-4, C-5, C-6), 25.6 (C-3), 19.7 (C-
1.42–1.24 (m, 6 H, 4-H to 6-H) ppm. FTIR (KBr): ν
= 3435,
˜
max
3007, 2920, 2847, 1631, 1001, 742, 688 cm–1. MS (ESI–): m/z = 309
[M – H]–. UV (MeOH): λmax = 326, 339 (max.), 358 nm.
7) ppm. FTIR (KBr): ν
= 3435, 2956, 2928, 2847, 1631, 1447,
˜
max
Synthesis of 14-Phenyltetradeca-9,11,13-trien-7-yn-1-ol (3Bh): A
solution of potassium tert-butoxide (340 mg, 3.02 mmol) in dry
THF (7 mL) was added with stirring and under argon to a solution
of phosphonate 6 (846 mg, 3.02 mmol) and aldehyde 7 (675 mg,
2.51 mmol) in THF (20 mL) at 0 °C. After stirring the mixture at
room temperature for 1 h, the solvent was evaporated in vacuo.
Column chromatography of the crude product (silica gel, hexane/
EtOAc 9:1) yielded a 9:1 (9E,11E,13E)/(9Z,11E,13E) isomeric mix-
ture of the protected alcohol tert-butyldimethyl(14-phenyltetra-
deca-9,11,13-trien-7-ynyloxy)silane. Yield: 590 mg, 60%. Pale yel-
low amorphous solid. Rf = 0.70 (EtOAc/hexane, 9:1). 1H NMR
(300 MHz, CDCl3, 25 °C): δ = 7.30 (d, J = 7.0 Hz, 2 H, Ho), 7.31
(t, J = 7.3 Hz, 2 H, Hm), 7.22 (t, J = 7.3 Hz, 1 H, Hp), 6.86 (m, 1
H, 13-H), 6.59 (d, J = 15.6 Hz, 1 H, 14-H), 6.59 (dd, J = 10.5,
15.5 Hz, 1 H, 10-H), 6.42 (m, 2 H, 11-H, 12-H), 5.64 (dt, J = 15.2,
2.1 Hz, 0.9 H, 9-H of isomer (9E)), 5.46 (dt, J = 10.2, 2.2 Hz, 0.1
H, 9-H isomer (9Z)), 3.61 (t, J = 6.5 Hz, 2 H, 1-H), 2.43 (td, J =
7.0, 2.2 Hz, 0.2 H, 6-H of isomer (9Z)), 2.35 (td, J = 7.0, 2.1 Hz,
1.8 H, 6-H of isomer (9E)), 1.54 (m, 4 H, 2-H, 5-H), 1.46–1.31 (m,
4 H, 3-H, 4-H), 0.90 (s, 9 H, SiC(CH3)3), 0.05 (s, 6 H, Si-
(CH3)2) ppm. 13C NMR (75 MHz, CDCl3, 25 °C): δ = 137.6 (Ci),
134.6, 134.0 (C-10, C-14), 140.9, 133.0, 129.2 (C-11 to C-13), 129.1
(Cm), 128.1 (Cp), 126.8 (Co), 112.5 (C-9), 94.9 (C-7), 80.8 (C-8),
63.6 (C-1), 33.1, 29.1, 28.9, 25.8 (C-2 to C-5), 26.4 (SiC(CH3)3),
20.1 (C-6), 18.7 (SiC(CH3)3), –4.9 (Si(CH3)2) ppm. MS (EI, 70 eV):
m/z (%) = 394 (15) [M]+, 337 (4), 263 (7), 193 (22), 178 (30), 165
(22), 117 (51).
1261, 1096, 1020, 802, 746, 688 cm–1. MS (EI, 70 eV): m/z (%) =
294 (42) [M]+, 205 (7), 193 (45), 179 (100), 165 (57), 152 (22), 141
(26), 129 (30), 115 (68), 91 (90). HRMS (peak matching): calcd. for
C21H26O 294.1984; found 294.1979. UV (CHCl3): λmax = 334, 346
(max.), 358 nm. UV (MeOH/H2O, 9:1): λmax = 322, 336 (max.),
354 nm.
all-(E)-15-Phenylpentadeca-10,12,14-trien-8-ynoic Acid (3Bf): Com-
pound 3Bf was obtained by hydrolysis of all-(E)-3Bc (194 mg,
0.6 mmol). Yield: 183 mg, 99%. Yellowish crystals. Rf = 0.41 (hex-
1
ane/EtOAc, 1:1). H NMR (300 MHz, CDCl3, 30 °C): δ = 7.39 (d,
J = 7.3 Hz, 2 H, Ho), 7.31 (t, J = 7.3 Hz, 2 H, Hm), 7.22 (t, J =
7.5 Hz, 1 H, Hp), 6.81 (dd, J = 15.5, 9.8 Hz, 1 H, 14-H), 6.59 (dd,
J = 15.4, 10.0 Hz, 1 H, 11-H), 6.58 (d, J = 15.5 Hz, 1 H, 15-H),
6.43 (dd, J = 14.7, 9.8 Hz, 1 H, 13-H), 6.35 (dd, J = 14.7, 10.0 Hz,
1 H, 12-H), 5.64 (dt, J = 15.4, 2.4 Hz, 1 H, 10-H), 2.37 (m, 4 H,
1-H, 7-H), 1.66 (q, J = 7.3 Hz, 2 H, 3-H), 1.56 (quint, J = 6.9 Hz, 2
H, 6-H), 1.40 (m, 4 H, 4-H, 5-H) ppm. 13C NMR (75 MHz, CDCl3,
30 °C): δ = 179.5 (CO), 140.6 (C-11), 137.2 (Ci), 134.3 (C-13), 133.7
(C-15), 132.5 (C-12), 128.7 (C-14), 128.6 (Cm), 127.7 (Cp), 126.4
(Co), 112.0 (C-10), 94.3 (C-8), 80.5 (C-9), 33.9 (C-2), 28.6, 28.5,
28.4 (C-4 to C-6), 24.5 (C-3), 19.7 (C-7) ppm. FTIR (KBr): ν
=
˜
max
3434, 3014, 2934, 2855, 1711, 1631, 996, 757, 688 cm–1. MS (EI,
70 eV): m/z (%) = 308 (27) [M]+, 193 (43), 179 (100), 165 (48), 152
(18), 141 (19), 129 (22), 115 (57), 91 (69). HRMS (peak matching):
calcd. for C21H24O2 308.1776; found 308.1770. UV (CHCl3): λmax
= 334, 342 (max.), 359 nm. UV (MeOH/H2O, 9:1): λmax = 322, 336
(max.), 354 nm.
The resulting 9:1 mixture of isomers was deprotected to give the
corresponding isomeric alcohols as follows: A solution of tetrabu-
tylammonium fluoride (TBAF) (1.0  in THF, 1 mL, 0.95 mmol)
was added dropwise to the solution of the protected alcohol (9:1
(9E)/(9Z) mixture) (260 mg, 0.63 mmol) in THF (10 mL) at room
temperature and the mixture was stirred for 20 min. Then more
TBAF solution was added (0.5 mL, 0.48 mmol) and the reaction
mixture was stirred for another 20 min. Work up yielded a crude
product that was purified by column chromatography with hexane/
EtOAc (7:3) as eluent. Yield: 180 mg, 98%. Pure all-(E)-3Bh was
separated by washing the solid (9E)/(9Z) mixture with n-pentane.
Data for all-(E)-3Bh: M.p. 98–100 °C. Rf = 0.65 (hexane/EtOAc,
all-(E)-Octadeca-8,10,12,14,16-pentaen-1-ol (5Ae): Compound 5Ae
was obtained by hydrolysis of acetate 5Ab (181 mg, 0.6 mmol).
Yield: 94 mg, 60%. Bright white crystals. Rf = 0.22 (hexane/EtOAc,
1
4:1). H NMR (300 MHz, [D6]DMSO, 70 °C): δ = 6.40–6.00 (m, 8
H, 9-H to 16-H), 5.73 (m, 2 H, 8-H, 17-H), 4.40 (br. s, 1 H, OH),
3.37 (t, J = 6.6 Hz, 2 H, 1-H), 2.07 (dt, J = 7.2, 6.9 Hz, 2 H, 7-H),
1.74 (d, J = 6.9 Hz, 3 H, 18-H), 1.40 (quint, J = 6.6 Hz, 2 H, 2-
H), 1.36 (quint, J = 6.6 Hz, 2 H, 6-H), 1.27 (m, 6 H, 3-H to 5-
H) ppm. 13C NMR (75 MHz, [D6]DMSO, 70 °C): δ = 134.7, 132.4,
132.3, 131.88, 131.86, 131.5, 130.3, 130.14, 130.11, 128.1, 60.3,
32.0, 31.7, 28.2 (ϫ2), 28.1, 25.0, 17.4 ppm. FTIR (KBr): ν
=
˜
max
1
3401, 2927, 2850, 1633, 1633, 1465, 1070, 1002 cm–1. MS (EI):
m/z (%) = 260 (100) [M]+, 159 (22), 145 (90), 131 (66), 117 (81),
105 (63), 91 (65), 79 (63). UV (EtOH): λmax (logε) = 344 (4.02),
327 (4.01), 312 (4.79), 298 nm (4.48). C18H28O (260.41): calcd. C
83.02, H 10.38; found C 82.26, H 10.37.
1:1). H NMR (300 MHz, CDCl3, 25 °C): δ = 7.40 (d, J = 7.3 Hz,
2 H, Ho), 7.32 (t, J = 7.3 Hz, 2 H, Hm), 7.22 (t, J = 7.3 Hz, 1 H,
Hp), 6.86 (dd, J = 9.5, 15.3 Hz, 1 H, 13-H), 6.59 (d, J = 15.7 Hz,
1 H, 14-H), 6.59 (dd, J = 9.2, 15.2 Hz, 1 H, 10-H), 6.41 (m, 2 H,
11-H, 12-H), 5.64 (d, J = 15.3 Hz, 1 H, 9-H), 3.66 (t, J = 6.0 Hz,
2 H, 1-H), 2.37 (t, J = 5.9 Hz, 2 H, 6-H), 1.58 (m, 4 H, 2-H, 5-H),
1.48–1.31 (m, 4 H, 3-H, 4-H) ppm. 13C NMR (75 MHz, CDCl3,
25 °C): δ = 137.6 (Ci), 129.1 (C-13), 141.0, 134.7, 134.1, 132.9 (C-
10, C-11, C-12, C-14), 129.1 (Cm), 128.1 (Cp), 126.8 (Co), 112.4 (C-
9), 94.9 (C-7), 80.8 (C-8), 63.4 (C-1), 33.1, 29.1, 29.1, 25.7 (C-2 to
all-(E)-Octadeca-8,10,12,14,16-pentaenoic Acid (5Af) (t-COPA):
Compound 5Af was obtained by hydrolysis of ester 5Ac (173 mg,
0.6 mmol). Yield: 156 mg, 95%. Ivory crystals; m.p. 139 °C. Rf =
0.33 (hexane/EtOAc, 4:1). This is a known compound; it was pre-
viously obtained through a Wittig olefination approach.[21]
C-5), 20.1 (C-6) ppm. FTIR (KBr): ν
= 3435, 2927, 2855, 1631,
˜
max
all-(E)-15-Phenylpentadeca-8,10,12,14-tetraenoic Acid (5Bf): Com-
pound 5Bf was obtained from 4Bc (195 mg, 0.6 mmol) by iodine
1447, 1071, 995, 746, 688 cm–1. MS (EI, 70 eV): m/z (%) = 280 (43)
[M]+, 193 (45), 179 (100), 165 (58), 152 (21), 141 (25), 128 (29), 115
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2007, 2285–2295

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Received: November 2, 2006
Published Online: March 20, 2007
Eur. J. Org. Chem. 2007, 2285–2295
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2295