Approaches to polyunsaturated sphingolipids: New conformationally restrained analogs with minimal structural modifications

Article abstract of DOI:10.1016/j.tet.2015.11.067

Conformationally restrained sphingolipids 1-4, arising from the introduction of a polyene or a polyenyne moiety as part of the sphingoid backbone, have been synthesized. While addition of polyene acetylides 6 and 7 to Garner's aldehyde afforded the corres

Full text of DOI:10.1016/j.tet.2015.11.067

Tetrahedron 72 (2016) 605e612
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Approaches to polyunsaturated sphingolipids: new
conformationally restrained analogs with minimal structural
modifications
a
a
c
c
a,b,
*
ꢀ
ꢀ
~
Ingrid Nieves , Jose-Luis Abad , L. Ruth Montes , Felix M. Goni , Antonio Delgado
a Research Unit on BioActive Molecules, Department of Biomedicinal Chemistry, Institute for Advanced Chemistry of Catalonia (IQAC-CSIC), Jordi Girona
18-26, E-08034, Barcelona, Spain
b University of Barcelona (UB), Faculty of Pharmacy, Department of Pharmacology and Medicinal Chemistry, Unit of Pharmaceutical Chemistry
(Associated Unit to CSIC), Avga. Joan XXIII s/n, E-08028, Barcelona, Spain
c Unidad de Biofísica (CSIC-UPV/EHU), and Departamento de Bioquímica, Universidad del País Vasco, Aptdo. 688, 48080, Bilbao, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 15 October 2015
Received in revised form 27 November 2015
Accepted 30 November 2015
Available online 15 December 2015
Conformationally restrained sphingolipids 1e4, arising from the introduction of a polyene or a polyenyne
moiety as part of the sphingoid backbone, have been synthesized. While addition of polyene acetylides 6
and 7 to Garner’s aldehyde afforded the corresponding Felkin-Anh anti-addition adducts, addition of
alkenylzirconocenes showed no diastereoselectivity. This behaviour was also observed from protected
serinal 14, which allowed the synthesis of the acid-sensitive pentaene sphingosine backbone present in
ceramide 4. Despite the inherent limitations of the synthetic approaches here reported, their application
to such highly conjugated polyene sphingoid analogs is unprecedented.
Keywords:
Sphingolipids
Diastereoselectivity
Polyene
Ó 2015 Elsevier Ltd. All rights reserved.
Hydrozirconation
Ceramide
Sphingosine
1. Introduction
alterations in the resulting probe,15 in comparison with commer-
cially available bulkier chromophores, such as BODIPY or NBD.16,17
One of the ultimate goals in biology is to understand the re-
lationship between structure, function, and dynamics of bio-
molecules in their natural environment, namely the living cell. In
this context, the use of conformationally restrained analogs has
become a common strategy in medicinal chemistry programs to
delineate the active conformation of flexible molecules and, in-
directly, to gain insight into the three-dimensional requirements of
their receptors.1 This approach has also been applied in the
sphingolipid arena by incorporating part of the aminodiol moiety of
the sphingoid backbone into cyclic structures2e4 or, less frequently,
by introduction of unsaturations in the sphingoid chain.5e10 How-
ever, the full understanding of the roles of sphingolipids (SLs) in the
cell environment is far for complete due to a lack of adequate ex-
periments able to directly visualize molecular interactions under
physiological conditions. In this context, fluorescent lipid analogs
become useful biophysical tools. In particular, polyene systems11e14
are suitable fluorescent tags that introduce minimize structural
Most importantly, the pentaene moiety has been reported to be-
have like its endogenous saturated counterparts in vivo, with re-
spect to uptake, metabolism, transport and localization in
membrane microdomains.12,18,19 However, when these labeled
lipids are part of the N-acyl or O-acyl SLs chains,11,12,15,20,21 the
fluorophore can be released by hydrolysis of the amide or the ester
bonds by specific enzymes, and the resulting sphingoid base is no
longer traceable. This is not the case when the polyene system is
part of the sphingoid backbone. On the other hand, the chemical
modification of the sphingoid backbone by incorporation of an
acetylene group has received considerable attention.8,22e24 The
triple bond increases the rigidity of the molecule, affecting its
physicochemical and biological properties.
Based on the above considerations and in our interested in the
development of new sphingolipid probes with potential bio-
physical and biochemical applications, we wish to report on the
development of synthetic protocols for the elaboration of new
conformationally constrained sphingosines and ceramide analogs
resulting from the incorporation of a polyunsaturated system as
part of the sphingoid backbone. In this account, the synthesis of
* Corresponding author. E-mail address: delgado@rubam.net (A. Delgado).
http://dx.doi.org/10.1016/j.tet.2015.11.067
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

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I. Nieves et al. / Tetrahedron 72 (2016) 605e612
polyenyne sphingosines 1 and 2, polyene sphingosine 3 and poly-
ene ceramide 4 are described as representative examples of the
above general approach (Fig. 1).
On the other hand, by addition of a transient alkenylzinc in-
termediate, arising from transmetallation of the above alkenyl zir-
conocene, the opposite syn stereoselectivity is obtained.41,42 In our
case, initial hydrozirconation attempts of 6 using ZnBr2 as Lewis
acid were unsuccessful, since no addition products were obtained.
After much experimentation (variation of ZnBr2 stoichiometry,
solvent systems,45 and even the in situ generation of Schwartz re-
agent46) we turned our attention to the use of silver salts, which
have also been reported as suitable catalysts for the addition of
alkenyl zirconocenes to aldehydes.47e49 Thus, coupling of Garner’s
aldehyde, in the presence of AgClO4 (20% mol), with the alkenyl
zirconocene arising from alkyne 6 (5E/Z: 4/1) afforded the desired
addition product 10 in 50% yield in a roughly 1:1 syn/anti ratio, as
expected from the reported drop of diastereoselectivity under sil-
ver promoted additions.41,47 Similarly, the hydrozirconation-
coupling of alkyne (all-E)-7 with Garner’s aldehyde under the
above conditions led to the expected adduct 11 (syn/anti 1:1), albeit
in lower yield (Scheme 2). Despite the simultaneous deprotection
of the isopropylidene and N-Boc groups of 10 in HCleMeOH
afforded the expected polyene sphingosine 3, these conditions
were not suitable for the deprotection of pentaene 11, since
a complex mixture of products were obtained in all cases.
In light of the above results and taking into account the apparent
instability of the conjugated pentaene system under the acidic
conditions required for the deprotection step, we considered the
use of an alternative protection strategy in the starting aldehyde.
Thus, the previously unreported protected serinal 14 was consid-
ered for our purposes. In this case, the Fmoc and TBDMS protecting
groups would enable the use of non-acidic deprotection conditions
in the final step. The protected serinal 14 was obtained from Fmoc
serine methyl ester, after hydroxyl protection (as the TBDMS ether
12) and reduction of the intermediate Weinreb amide 13 (Scheme
3). Alkenylation of aldehyde 14 was optimized using 1-
tetradecenylzirconocene as a model, obtained from treatment of
1-tetradecyne with Schwartz reagent. Under the above silver pro-
moted alkenylation conditions, a marked stereoselectivity leading
to the unnatural syn adduct (anti/syn 1:4) was observed. The con-
figurational assignment at C3 in this mixture was unambiguously
confirmed by its derivatization to the corresponding (R) and (S)-
MPA esters, following the standard methodology of Riguera et al.,50
as illustrated in Fig. 2.
2. Results and discussion
Access to the alkyne polyene framework present in probes 1 and
2 was planned by nucleophilic addition of the corresponding lith-
ium acetylides of 6 or 7 (Scheme 1) to Garner’s aldehyde under
conditions similar to those described for simpler acetylenes.23,25e27
The synthesis of the required acetylenes started from the phos-
phonium salt 5, easily obtained in two steps (85% overall yield)
from commercially available 4-pentyn-1-ol.28 Salt 5 was submitted
to (E)-selective Wittig olefination29 with the required polyene al-
dehyde (2,4-hexadienal for 6 and 2,4,6,8-decatetraenal30 for 7),
followed by iodine-promoted isomerization31e34 of the resulting
polyene system. The initial condensation attempts of 6 with Gar-
ner’s aldehyde, using BuLi/HMPA or LiHMDS in THF at low tem-
perature for acetylide generation, were unsuccessful. Only the use
of LDA in THF at ꢀ78 ꢁC afforded acceptable yields of the conden-
sation adduct 8. Application of the above conditions to acetylene 7
led to the corresponding adduct 9, albeit in lower yields. Gratify-
ingly, only the corresponding C3-erythro isomers of 8 and 9 were
obtained, in agreement with the operation of a Felkin-Anh transi-
tion state model. The low temperature used in this condensation
step becomes crucial for the exclusive formation of the erythro
isomers and avoids the use of HMPA or HMPT as co-solvents.23 In
our case, the erythro configuration of 8 and 9 was confirmed by
comparison with the reported 1H NMR data for the corresponding
saturated alkyne in CDCl3.35 The simultaneous removal of the iso-
propylidene and Boc groups of the above adducts under acidic
conditions (HCl in MeOH)36 led to the target acetylene polyene
probes 1 and 2 in acceptable yields (Scheme 1). Contrary to our
initial expectations, the acidic conditions used in this deprotection
step were compatible with the presumably acid-sensitive polyene
framework of the sphingoid backbone.
For the synthesis of the polyene probes 3 and 4 (Fig. 1), initial
attempts relied on the stereoselective Red-AlÒ reduction of the
propargylic alcohols 8 and 9 to the corresponding E-allylic alcohols,
following the reported methodology of Herold et al.37 However,
complex reaction mixtures were obtained in both cases, as well as
from the fully deprotected amino diol 1. In light of these results,
hydrozirconation of the alkyne polyenes 6 and 7 with Schwartz
reagent (Cp2Zr(H)Cl),38 followed by addition of the intermediate
alkenyl zirconocenes to Garner’s aldehyde, was considered
(Scheme 2). According to the literature, this sequence has been
successfully applied to the elaboration of the allylic alcohol
framework present in simple sphingolipids and related com-
pounds.39e44 In particular, the addition of alkenyl zirconocenes to
Garner’s aldehyde has been reported to lead to anti adducts by the
use of substoichiometric ZnBr2 as carbonyl-activating Lewis acid.
Attempts to revert this stereoselectivity were next undertaken.
After much experimentation, the use of ZnCl2 (50 mol %) in DCM
allowed the alkenylation of 14 with polyene (all-E)-7 to afford the
adduct 15 as an anti/syn 1:1.5 mixture, albeit in modest yield
(Scheme 3). The diastereoisomeric composition of 15 was inferred
from that of the above model reaction of aldehyde 14 with 1-
tetradecyne.
In order to avoid an excessive manipulation of the sensitive
polyene sphingosine system, we decided to carry out an one-pot
deprotection-acylation of 15. Thus, the simultaneous removal of
Fig. 1. Unsaturated probes described in this work.

I. Nieves et al. / Tetrahedron 72 (2016) 605e612
607
Scheme 1. (a) BuLi (2.5 M hexanes), HMPA, THF, 2,4-hexadienal (for 6) or 2,4,6,8-decatetraenal (for 7), ꢀ78 ꢁC, 4 h; (b) I2 in hexanes, reflux (for 6, 5E/Z 4:1, 80% combined; for ‘all E’-
7, 25% yield after preparative HPLC, see Experimental); (c) 1) LDA, ꢀ78 ꢁC, 30 min; 2) Garner’s aldehyde, THF, 3 h from ꢀ78 ꢁC to rt (8, 45% or 9, 25%); (d) CH3COCl (1.5% vol), MeOH,
0
ꢁC to rt, 30 min (1, 60% or 2, 40%).
the Fmoc51 and TBDMS groups52e54 with TBAF in THF, followed by
N-acylation of the crude reaction mixture with palmitic acid and
EDC-HOBt, afforded the expected polyene ceramide 4 after chro-
matographic purification, albeit as an inseparable mixture of syn/
anti diastereomers.
reported in ppm relative to the solvent (CDCl3) signal. The polyenes
described in this work, due to their labile nature, were stored at
ꢀ80 ꢁC as THF solutions (1 mg/mL) solutions stabilized with BHT
(butylated hydroxytoluene).
4.1. Pent-4-yn-1-yltriphenylphosphonium iodide (5)
3. Conclusion
a) 5-Iodo-1-pentyne:
A solution of 4-pentyn-1-ol (2.5 g,
Synthetic approaches to polyene sphingosine analogs, based on
the alkynylation or hydrozirconation of Garner’s aldehyde with the
unprecedented polyene alkynes 6 and 7 are reported. While addi-
tion of lithium acetylides afforded the natural anti adducts, addition
of alkenylzirconocenes showed no diastereoselectivity. This trend
was also observed from aldehyde 14, which allowed the synthesis
of the acid-sensitive pentaene sphingosine backbone present in
ceramide 4. Despite the inherent limitations of the synthetic ap-
proaches here reported, their application to such highly conjugated
polyene sphingoid analogs is unprecedented. Experiments
addressed at illustrating the applicability of these fluorescent
probes in a variety of biophysical studies will be reported in due
course.
29.7 mmol) in DCM (30 mL) was added to a rapidly stirred sus-
pension of triphenylphosphine (10.1 g, 38.9 mmol), imidazole
(2.6 g, 38.6 mmol) and iodine (9.8 g, 38.6 mmol) in DCM (120 mL).
After stirring for 1 h, the solvent was evaporated and the residue
purified by flash column chromatography (hexane:EtOAc; 95:5) to
give the 5-iodo-1-pentyne as an orange oil (60%).
Rf: 0.86 (hexane:EtOAc; 9:1).
1H NMR (CDCl3):
d
3.44e3.11 (m, 2H), 2.33 (qt, J¼7.0, 3.0 Hz, 3H),
2.09e1.92 (m, 3H).
13C NMR (CDCl3):
d 82.2 (C), 69.5 (CH), 31.8 (CH2), 19.4 (CH2), 5.1
(CH2).
b) A mixture of 5-iodo-1-pentyne (2.7 g, 14.0 mmol) and tri-
phenylphosphine (11 g, 42.0 mmol) was heated at 86 ꢁC for 16 h
under Ar. The wax mixture was cooled down to rt and then was
added hexane (50 mL) affording a precipitate. The supernatant was
discarded and the crude was concentrated under reduced pressure.
The residue was purified by flash column chromatography
(DCM:MeOH; 96:4) to give a yellowish solid (85%).
4. Experimental
General: Commercial grade reagents and solvents were directly
used as supplied with the exception of THF that was distilled over
Na/benzophenone under Ar. Reactions sensitive to moisture and
oxygen were carried out under argon or nitrogen atmosphere and
were monitored by thin layer chromatography (TLC) on aluminum
foil pre-coated silica gel plates. Visualization of UV-inactive mate-
rials was accomplished by soaking the TLC plates in an ethanol
solution of phosphomolybdic acid (5%) and developing of the
stained material with a heating gun. Organic solutions obtained
from workup of crude reaction mixtures were dried over anhydrous
MgSO4. Flash column chromatography was performed with the
indicated solvents using silica gel 60 (230e400 mesh). Yields refer
to chromatographically and spectroscopically pure compounds,
unless otherwise stated. 1H and 13C NMR spectra were obtained in
CDCl3 solutions at 400 MHz (for 1H) and 101 MHz (for 13C), re-
Rf: 0.72 (DCM:MeOH; 9:1).
1H NMR (CDCl3)
d 7.87e7.78 (m, 9H), 7.74e7.68 (m, 6H),
3.96e3.87 (m, 2H), 2.66 (ddd, J¼12.0, 6.5, 1.0 Hz, 2H), 2.01 (t,
J¼3.0 Hz, 1H), 1.96e1.84 (m, 2H).
13C NMR (CDCl3)
CH), 130.5 (JCeP¼12 Hz, CH), 118.2 (C), 117.1 (C), 82.3 (C), 70.6 (CH),
21.8 (JCeP¼51.8 Hz, CH2), 21.7 (JCeP¼2.3 Hz, CH2), 19.2 (JCeP¼18.8 Hz,
CH2).
d
135.2 (JCeP¼2.2 Hz, CH), 133.5 (JCeP¼9.8 Hz,
4.2. (5E,7E,9E)-Undeca-5,7,9-trien-1-yne (6)
To a suspension of phosphonium iodide 5 (6.3 g, 13.8 mmol) in
anhydrous THF (150 mL) under Ar was added HMPA (7.5 mL, 5% vol)
at rt and then cooled to ꢀ78 ꢁC. To the reaction mixture was added
spectively, unless otherwise indicated. Chemical shifts (d) are
Scheme 2. (a) 6 (5E/Z: 4/1), Cp2Zr(H)Cl, AgClO4, DCM, 0 ꢁC to rt, 40 min, (anti/syn 1:1) (50%); (b) idem from (all-E)-7, (anti/syn 1:1) (20%); (c) CH3COCl (3% vol), MeOH, rt, 1 h,
quantitative (anti/syn 1:1 from 10).

608
I. Nieves et al. / Tetrahedron 72 (2016) 605e612
Scheme 3. (a) N,O-dimethylhydroxylamine$(HCl), DCM, Me3Al (2 M in toluene) (93%); (b) LiAlH4. THF, (90%); (c) (all-E)-7, Cp2Zr(H)Cl, ZnCl2, DCM, 0 ꢁC to rt, 40 min, (anti/syn¼1:1.5)
(20%); (d) 1) TBAF (1 M in THF), THF, rt, 90 min; 2) Palmitic acid, HOBt, EDC, Et3N, DCM, rt, 90 min, (anti/syn: 1:1.5), (20% combined).
(5Z,7E,9E)
d 133.8 (CH), 131.8 (CH), 130.3 (CH), 130.2 (CH), 129.0
(CH), 125.4 (CH), 84.0 (C), 68.8 (CH), 27.1 (CH2), 19.0 (CH2), 18.5
(CH3).
Analytical HPLC for 6. Column (Kromasil 100, C18, 5
15ꢂ0.4 cm). Isocratic method (30:70, H2O:ACN). Sample volume:
25 L; 6 (1 mg/mL DMSO); Rt: 6.6 min (Z-isomer); Rt: 7.1 min (E-
isomer) ( : 254 nm).
mm,
m
l
4.3. (5E,7E,9E,11E,13E)-Pentadeca-5,7,9,11,13-pentaen-1-yne
(7)
Using the protocol described above for 6, pentaenyne 7 (650 mg,
55% yield) was obtained from phosphonium salt 5 (4.5 g, 9.8 mmol)
and trans-2,4,6,8-hexatetraenal30 (0.70 mL, 6.1 mmol) as a mixture
of isomers 5E:5Z: 2:1. Isomerization of the C5eC6 double bond led
to a 5E:5Z: 6:1 mixture of isomers. Purification by preparative HPLC
afforded pure 7 (see conditions below).
Fig. 2. (R)- and (S)-MPA derivatives of the major syn diastereomer from the alkeny-
lation of aldehyde 14 with 1-tetradecenylzirconocene.
Rf: 0.30 (hexane).
1H NMR (CDCl3): (5E,7E,9E,11E,13E)
d 6.37e6.03 (m, 8H), 5.73
(dq, J¼14.5, 7.0 Hz, 2H), 2.40e2.24 (m, 4H), 1.97 (t, J¼2.5 Hz, 1H),
1.78 (dd, J¼7.0, 1.4 Hz, 3H).
dropwise a solution of n-butyllithium (2.5 M in hexanes, 5.8 mL,
14.6 mmol) and then was warmed to 0 ꢁC with stirring for 1 h. After
cooling the reddish orange solution to ꢀ78 ꢁC, commercial trans,-
trans-2,4-hexadienal (1 mL, 8.6 mmol) was added dropwise under
Ar and protected from light. After 4 h the conversion was complete.
Then, MeOH (60 mL) was added at ꢀ78 ꢁC and the resulting mix-
ture was gradually warmed overnight to rt. The mixture was con-
centrated under reduced pressure and then extracted with Et2O
(3ꢂ50 mL). The combined organic layers were washed with brine,
dried over MgSO4, and concentrated. The residue was purified by
flash column chromatography (hexane) with silica gel neutralized
with Et3N (1% vol, using hexane as solvent) to afford 6 as a pale
yellow oil in 80% yield, (5E:Z): (1:1).
(5Z,7E,9E,11E,13E) d 6.75e6.35 (m, 2H), 6.33e5.86 (m, 7H), 5.49
(ddd, J¼18.0, 9.0, 7.0 Hz, 1H), 2.50e2.40 (m, 2H), 2.39e2.31 (m, 2H),
1.97 (t, J¼2.5 Hz, 1H), 1.82 (d, J¼7.0 Hz, 3H).
13C NMR (CDCl3): (5E,7E,9E,11E,13E)
d 133.3 (CH), 133.1 (CH),
132.5 (CH), 132.4 (CH), 132.3 (CH), 132.1 (CH), 132.0 (CH), 131.9 (CH),
130.7 (CH), 130.3 (CH), 83.92 (C), 68.9 (CH), 32.0 (CH2), 18.8 (CH2),
18.5 (CH3).
(5Z,7E,9E,11E,13E)
d 133.8 (CH), 133.7 (CH), 133.6 (CH), 132.1
(CH),132.0 (CH), 130.6 (CH), 130.5 (CH), 130.3 (CH),129.8 (CH), 127.6
(CH), 83.9 (C), 68.8 (CH), 27.2 (CH2), 18.9 (CH2), 18.6 (CH3).
Preparative-HPLC for (all-E)-7: Column (X-Bridge C18, 5
OBD, 19ꢂ250 mm). Isocratic method (35:65, H2O:ACN, 10 mL/min);
Rt: 35.0 min; : 330 nm.
mm
l
Isomerization of the C5eC6 double bond: To a mixture of the
above isomers 6 (50 mg, 0.3 mmol) in hexane (125 mL) under Ar,
was added a saturated solution of iodine in hexane (5
mL). The
4.4. (S)-tert-Butyl 4-((R,6E,8E,10E)-1-hydroxydodeca-6,8,10-
trien-2-yn-1-yl)-2,2-dimethyloxazolidine-3-carboxylate (8)
resulting solution was heated at 69 ꢁC for 20 min, after which the
solution was cooled to rt. The mixture was washed thoroughly with
saturated aqueous sodium metabisulfite (Na2S2O5) and the yellow
solution was washed with water, dried, and concentrated under
reduced pressure to furnish 6 (quantitative) as a pale yellow oil of
a mixture of diastereomers (5E:Z, 4:1).
To a stirred solution of alkyne 6 (5E/Z 4/1) (400 mg, 2.4 mmol) in
anhydrous THF (40 mL), was added dropwise a solution of LDA
(3.3 mmol, 1.8 M in THF/heptane/ethylbenzene) at ꢀ78 ꢁC under Ar.
The mixture was stirred at ꢀ78 ꢁC for 30 min, and then was added
a solution of Garner’s aldehyde (815 mg, 3.6 mmol) in THF (20 mL).
After 3 h, a saturated aqueous NH4Cl (5 mL) solution was added to
the reaction mixture at ꢀ78 ꢁC and was warmed to rt. The resulting
white suspension was diluted with H2O, and extracted with Et2O
(3ꢂ50 mL). The combined organic layers were dried with MgSO4
and concentrated under reduced pressure. The residue was purified
by flash column chromatography (hexane:EtOAc, 90:10) with
silica-gel neutralized with Et3N (1% vol, using hexane as solvent) to
afford erythro-8 in 45% yield (enriched in the (all-E) isomer).
Rf: 0.36 (hexane).
1H NMR (CDCl3): (5E,7E,9E)
d 6.23e6.00 (m, 4H), 5.78e5.62 (m,
2H), 2.37e2.22 (m, 2H), 1.97 (t, J¼2.5 Hz, 1H), 1.77 (dd, J¼7.0, 1.5 Hz,
3H).
(5Z,7E,9E)
d 6.42e6.29 (m, 1H), 6.23e6.02 (m, 3H), 5.81e5.66
(m, 1H), 5.49e5.38 (m, 1H), 2.47e2.39 (m, 2H), 2.29e2.22 (m, 2H),
1.97 (t, J¼3.0 Hz, 1H), 1.79 (d, J¼7.0 Hz, 3H).
13C NMR (CDCl3): (5E,7E,9E)
d 131.9 (CH), 131.8 (CH), 131.5 (CH),
130.2 (CH), 130.1 (CH), 129.6 (CH), 84.0 (C), 68.8 (CH), 31.9 (CH2),
18.8 (CH2), 18.4 (CH3).
Rf: 0.34 (hexane:EtOAc; 8:2); [
a]D: ꢀ22.6 (c 1.3, CHCl3)

I. Nieves et al. / Tetrahedron 72 (2016) 605e612
609
1H NMR (CDCl3): Data for (all-E)-isomer.
d
6.25e5.95 (m, 4H),
(v:25
mL, sample 1 mg/mL DMSO); (
l
: 254 nm). Rt: 11.8 and
5.77e5.60 (m, 2H), 4.62e4.40 (m, 1H), 4.21e3.82 (m, 3H),
2.33e2.25 (m, 4H), 1.76 (d, J¼7.0 Hz, 3H), 1.51 (s, 6H), 1.49 (s, 9H).
13C NMR (CDCl3): Some splitting observed due to rotamers.
12.3 min.
4.7. (S) tert-Butyl 4-(R:S(2E,6E,8E,10E,12E,14E)-1-hydroxyhexade
ca-2,6,8,10,12,14-hexaen-1-yl)-2,2-dimethyloxazolidine-3-
carboxylate (11)
d
154.2 (C), 133.6 (CH), 131.8 (CH), 131.7 (CH), 130.1 (CH), 129.4 (CH),
125.4 (CH), 95.0 (C), 85.8 (C), 81.3 (C), 78.7 (C), 64.8 (CH2), 64.0 (CH),
62.8 (CH), 32.0 (CH2), 28.5 (CH3), 28.3 (CH3), 19.1(CH2), 18.3 (CH3).
ESI-MS m/z C22H33NO4 [MþNa]þ Found:398.2315; Calculated:
398.2307.
Following the same protocol used for 10, condensation of alke-
nylzirconocene, obtained from alkyne 7 (200 mg, 1.0 mmol), with
Garner’s aldehyde afforded 11 in 20% yield as a 1:1 syn:anti mixture
after flash chromatography with silica-gel neutralized with Et3N
(1% vol, using hexane as solvent) (hexane:EtOAc; stepwise gradient
from 0 to 18% of EtOAc).
4.5. (S)-tert-Butyl 4-((R,6E,8E,10E,12E,14E)-1-hydroxyhexa
deca-6,8,10,12,14-pentaen-2-yn-1-yl)-2,2-
dimethyloxazolidine-3-carboxylate (9)
Rf: 0.30 (hexane:EtOAc; 8:2) (mixture syn:anti 1:1).
1H NMR (CDCl3): (syn:anti: 1:1).
d 6.28e6.00 (m, 7H), 5.80e5.58
Following the method described for 8, condensation of Garner’s
aldehyde with (all-E)-7 (500 mg, 2.5 mmol) afforded erytrho-9 in
25% yield.
(m, 3H), 5.56e5.37 (m, 2H), 4.44e4.30 (m, 1H), 4.26e4.06 (m, 2H),
4.06e3.77 (m, 3H), 2.25e2.11 (m, 4H), 1.78 (dd, J¼7.5, 1.5 Hz, 3H),
1.50 (s, 6H), 1.48 (s, 9H).
Rf: 0.24 (hexane:EtOAc; 8:2); [
1H NMR (CDCl3): Data described for (all-E)-isomer.
(6E,8E,10E,12E,14E) 6.34e6.00 (m, 8H), 5.83e5.62 (m, 2H),
a]D: ꢀ28.2 (c 1, CHCl3).
13C NMR (CDCl3): (syn:anti: 1:1).
d 159.3 (C), 133.1 (CH), 132.9
(CH), 132.8 (CH), 132.8 (CH), 132.8 (CH), 132.7 (CH), 132.5 (CH), 132.1
(CH), 131.4 (CH), 131.2 (CH), 130.8 (CH), 130.1 (CH), 118.0 (C), 94.6
(C), 74.0 (CH), 65.0 (CH2), 62.4 (CH), 32.6 (CH2), 32.3 (CH2), 28.6
(CH3), 26.5 (CH3), 18.6 (CH3).
d
4.74e4.58 (m, 1H), 4.59e4.45 (m, 1H), 4.24e3.81 (m, 3H),
2.35e2.24 (m, 4H), 1.78 (dt, J¼7.0, 2.0 Hz, 3H), 1.63e1.53 (m, 6H),
1.56e1.39 (m, 9H).
ESI-MS m/z C26H39NO4 [MþNa]þ Found: 452.2776; Calculated:
13C NMR (CDCl3): (6E,8E,10E,12E,14E).
d 154.3(C), 133.8 (CH),
452.2777; [MþH]þ Found:430.2995; Calculated: 430.2957.
133.7 (CH), 132.3 (CH), 132.1 (CH), 132.0 (CH), 131.9 (CH), 130.7 (CH),
130.6 (CH), 130.5 (CH), 130.3 (CH), 95.1 (C), 86.0 (C), 81.4 (C), 79.3
(C), 65.2 (CH2), 64.4 (CH), 62.9 (CH), 53.6 (C), 32.1 (CH2), 29.8 (CH3),
26.0 (CH3), 19.3 (CH2), 18.5 (CH3).
4.8. Methyl N-(((9H-fluoren-9-yl)methoxy)carbonyl)-O-(tert-
butyldimethylsilyl)-L-serinate (12)
ESI-MS m/z C26H37NO4 [MþNa]þ Found:450.2610; Calculated:
To a solution of Fmoc serine methyl ester55 (8.1 g, 23.7 mmol) in
anhydrous DCM (180 mL) was added TBDMSCl (7.1 g, 47.1 mmol)
followed by imidazole (4.8 g, 71.2 mmol) at 0 ꢁC. The reaction
mixture was warmed to rt and stirred for 3 h. The reaction was
quenched by the addition of saturated aqueous NH4Cl solution and
then was extracted with DCM (3ꢂ150 mL). The combined organic
extracts were washed with brine, dried with Mg2SO4 and concen-
trated. The residue was purified by flash chromatography (hex-
ane:EtOAc; 95:5) to afford 12 (10.3 g, 94%) as a white solid.
450.2620.
Analytical HPLC conditions for 9: Column (Kromasil 100, C18,
5
m
m, 15ꢂ0.4 cm). Isocratic method (30:70, H2O:ACN). Sample
(v:25 L, sample 1 mg/mL DMSO); ( : 331 nm). Rt: 23.6 min.
m
l
4.6. (S)-tert-Butyl 4-((R:S,2E,6E,8E,10E)-1-hydroxydodeca-
2,6,8,10-tetraen-1-yl)-2,2-dimethyloxazolidine-3-carboxylate
(10)
Rf: 0.81 (hexane:EtOAc; 7:3); [
a
]
þ19.6 (c 1, CHCl3).
D
To a flame-dried Schlenk with Cp2Zr(H)Cl (350 mg, 1.4 mmol),
was added a solution of alkyne 6 (5E/Z: 4/1; 200 mg, 1.4 mmol) in
anhydrous DCM (1.7 mL) at 0 ꢁC under Ar and protected from light.
During warming to room temperature (20 min), the zirconocene
complex gradually dissolved to give a clear orange solution. A so-
lution of Garner’s aldehyde (224 mg,1.0 mmol) in DCM (1.2 mL) was
added followed by AgClO4 (20% mol). After 20 min, the reaction
mixture turned dark red and was diluted with Et2O and quenched
by addition of 3 mL of saturated NaHCO3. The mixture was filtered
through a pad of CeliteÒ and extracted with Et2O (3ꢂ10 mL). The
combined ethereal solution were washed with brine, dried and
concentrated under reduced pressure. Flash chromatography with
silica-gel neutralized with Et3N (1% vol, using hexane as solvent) in
hexane:EtOAc (stepwise gradient from 0 to 12% of EtOAc) afforded
10 (50%) as an anti:syn 1:1mixture of diastereomers.
1H NMR (CDCl3):
d
7.77 (d, J¼7.5 Hz, 2H), 7.62 (t, J¼8.0 Hz, 2H),
7.40 (t, J¼7.5 Hz, 2H), 7.32 (td, J¼7.5, 1.0 Hz, 2H), 5.64 (d, J¼9.0 Hz,
1H), 4.48e4.43 (m, 1H), 4.42e4.33 (m, 2H), 4.26 (t, J¼7.5 Hz, 1H),
4.08 (dd, J¼10.0, 3.0 Hz, 1H), 3.87 (dd, J¼10.0, 3.0 Hz, 1H), 3.77 (s,
3H), 0.89 (s, 9H), 0.06 (s, 3H), 0.04 (s, 3H).
13C NMR (CDCl3):
d 171.1 (C), 156.1 (C), 144.1 (C), 143.9 (C), 141.4
(C), 127.9 (CH), 127.2 (CH), 125.3 (CH), 125.3(CH), 120.1 (CH), 67.4
(CH2), 63.8 (CH2), 56.1 (CH), 52.6 (CH3), 47.3 (CH), 25.9 (CH3), 18.4
(C), ꢀ5.4 (CH3), ꢀ5.5 (CH3).
ESI-MS m/z C25H33NO5Si [MþNa]þ Found: 478.2008; Calcu-
lated: 478.2026; [MþH]þ Found: 456.2193; Calculated: 456.2206.
4.9. (9H-Fluoren-9-yl)methyl (S)-(3,8,8,9,9-pentamethyl-4-
oxo-2,7-dioxa-3-aza-8-siladecan-5-yl)carbamate (13)
Rf: (anti) 0.38; (syn) 0.32 (hexane:EtOAc; 8:2).
A solution of N,O-dimethylhydroxylamine$(HCl) (13.5 g,
1H NMR (CDCl3): Mixture of diastereomers
d
6.19e5.93 (m, 4H),
138.3 mmol) in DCM (50 mL) under Ar, was treated at 0 ꢁC with
69.1 mL Me3Al (2 M in toluene, 138.3 mmol). The reaction mixture
was stirred at rt for 30 min, treated with a solution of 12 (21 g,
46.1 mmol) in DCM (150 mL) and heated to reflux for 16 h. The re-
action mixture was next cooled to 0 ꢁC and carefully quenched with
aqueous sodium potassium tartrate (10%, 75 mL). After stirring at rt
for 1 h, the resulting suspension was filtered through a pad of Cel-
iteÒ, which was then washed with DCM. The filtrates were con-
centrated under reduced pressure to give the crude product, which
upon purification by flash chromatography (hexane:EtOAc; 85:15)
afforded the Weinreb amide 13 (20.8 g, 93%) as a colorless oil.
5.77e5.57 (m, 3H), 5.51e5.38 (m,1H), 4.45e3.73 (m, 5H), 2.24e1.96
(m, 4H), 1.74 (d, J¼6.5 Hz, 3H), 1.47 (s, 6H), 1.46 (s, 9H).
13C NMR (CDCl3):
d 152.8 (C), 133.0 (CH), 132.4 (CH), 131.9 (CH),
131.3 (CH), 131.2 (CH), 130.5 (CH), 130.4 (CH), 129. (CH), 94.6 (C),
81.2 (C), 74.1 (CH), 65.0 (CH2), 62.4 (CH), 32.5 (CH2), 32.3 (CH2), 28.5
(2 CH3), 18.4 (CH3).
ESI-MS m/z C22H35NO4 [MþNa]þ Found: 400.2379; Calculated:
400.2464.
Analytical HPLC for 10 (anti:syn 1:1): Column (Kromasil 100,
C18, 5
mm, 15ꢂ0.4 cm). Isocratic method (30:70, H2O:ACN). Sample

610
I. Nieves et al. / Tetrahedron 72 (2016) 605e612
Rf: 0.35 (hexane:EtOAc; 7:3); [
a
]
D þ13.9 (c 1, CHCl3).
(t, J¼7.0 Hz, 1H), 3.96 (d, J¼10.0 Hz, 1H), 3.76 (d, J¼10.0 Hz, 1H),
3.71e3.62 (m, 1H), 3.26 (d, J¼5.0 Hz, 1H), 2.24e1.94 (m, 3H), 1.78
(dd, J¼7.0, 1.5 Hz, 3H),0.91 (s, 9H), 0.08 (s, 6H).
1H NMR (CDCl3):
d
7.76 (d, J¼7.5 Hz, 2H), 7.61 (t, J¼8.0 Hz, 2H),
7.40 (tq, J¼7.5, 1.0 Hz, 2H), 7.31 (tt, J¼7.5, 1.0 Hz, 2H), 5.69 (d,
J¼9.0 Hz, 1H), 4.89e4.79 (m, 1H), 4.36 (d, J¼7.5 Hz, 2H), 4.24 (t,
J¼7.0 Hz, 1H), 3.88 (qd, J¼10.0, 5.0 Hz, 2H), 3.77 (s, 3H), 3.24 (s, 3H),
0.89 (s, 9H), 0.05 (d, J¼2.0 Hz, 6H).
(syn):
d
7.77 (d, J¼8.0 Hz, 2H), 7.60 (d, J¼7.5 Hz, 2H), 7.40 (ddt,
J¼8.5, 7.5, 1.5 Hz, 2H), 7.31 (tt, J¼7.5, 2.0 Hz, 2H), 6.30e5.88 (m, 8H),
5.91e5.21 (m, 4H), 4.97 (d, J¼12.0 Hz, 2H), 4.54e4.30 (m, 3H), 4.23
(t, J¼7.0 Hz, 1H), 3.89e3.81 (m, 2H), 3.70e3.61 (m, 1H), 3.17 (d,
J¼12.5 Hz, 1H), 2.24e1.94 (m, 4H), 1.78 (dd, J¼7.0, 1.4 Hz, 3H), 0.91
(s, 9H), 0.08 (s, 6H).
13C NMR (CDCl3): The methyl group bonded to the Weinreb
amide is not observed in the 13C spectra.
d 156.1 (C), 156.1 (C), 144.1
(C),144.0 (C),141.4 (C),127.8 (CH),127.2 (CH),125.4 (CH),125.3 (CH),
120.1 (CH), 67.3 (CH2), 63.5 (CH2), 61.7 (CH3), 53.2 (CH), 47.3 (CH),
25.9 (CH3), ꢀ5.4 (CH3).
13C NMR (CDCl3): (mixture syn:anti):
d 156.3 (C), 144.1 (C), 141.5
(C), 133.1 (CH), 133.1 (CH), 132.8 (CH), 132.5 (CH), 132.4 (CH), 132.1
(CH), 132.1 (CH), 131.0 (CH), 130.8 (CH), 130.2 (CH), 129.9 (CH), 129.6
(CH), 127.85 (CH), 127.2 (CH), 125.23 (CH), 120.1 (CH), 73.4 (CH), 67.1
(CH2), 65.5 (CH2), 55.2 (CH), 47.4 (CH), 32.2 (CH2), 32.1 (CH), 26.0
(CH3), 18.3 (CH3), ꢀ5.4 (CH3).
ESI-MS m/z C26H36N2O5Si [MþNa]þ Found: 507.2280; Calcu-
lated: 507.2291; [MþH]þ Found: 485.2451; Calculated: 485.2472.
4.10. (S)-(9H-Fluoren-9-yl)methyl (1-((tert-butyldimethyl
silyl)oxy)-3-oxopropan-2-yl)-carbamate (14)
ESI-MS m/z C39H51NO4Si [MþNa]þ Found: 648.3478; Calculated:
648.3485; [MþH]þ Found: 626.3668; Calculated: 626.3666.
To a solution of Weinreb amide 13 (5 g, 10.3 mmol) in anhydrous
THF (100 mL) at ꢀ40 ꢁC, was added dropwise a solution of LiAlH4
(0.7 g, 19.6 mmol) in 20 mL of THF. After stirring for 2.5 h at ꢀ40 ꢁC,
the reaction was quenched by addition of saturated aqueous
Na2SO4 solution. The resulting white solid was filtered through
a pad of CeliteÒ, which was then washed with EtOAc. The filtrates
were concentrated under reduced pressure to give the crude
product, which was flash chromatographed (hexane:EtOAC; 98:12)
to afford the aldehyde 14 (3.9 g, 90%) as a colorless oil.
4.12. (2S,3R,8E,10E,12E)-1,3-Dihydroxytetradeca-8,10,12-trien-
4-yn-2-amonium chloride (1)
To a solution of 8 (200 mg, 0.5 mmol) in MeOH (35 mL) was
added dropwise acetyl chloride (540
m
L, 1.5% vol) at ꢀ30 ꢁC. The
resulting mixture was vigorously stirred and allowed to warm to rt
for 30 min. Next, addition of a saturated aqueous NaHCO3 solution
and concentration under reduce pressure, afforded a dark green
residue, which was taken up in DCM, dried over MgSO4, filtered
through a cotton pad and concentrated under reduced pressure to
give 80 mg (60% yield) of amino diol 1$HCl.
Rf: 0.44 (hexane:EtOAc; 8:2); [
a
]
þ19.3 (c 1, CHCl3).
D
1H NMR (CDCl3):
d
9.67 (s, 1H), 7.77 (d, J¼8.0 Hz, 2H), 7.65e7.57
(m, 2H), 7.41 (t, J¼7.5 Hz, 2H), 7.37e7.28 (m, 2H), 5.65 (d, J¼7.0 Hz,
1H), 4.42 (d, J¼7.0 Hz, 2H), 4.35 (dt, J¼7.0, 4.0 Hz, 1H), 4.29e4.18 (m,
3H), 3.90 (dd, J¼10.5, 4.0 Hz, 1H), 0.88 (s, 9H), 0.06 (s, 6H).
Rf: 0.60 (DCM:MeOH; 8:2); [
a
]D: ꢀ3.1 (c 1.2, CH3OH).
1H NMR (CD3OD):
d
6.46e5.93 (m, 4H), 5.86e5.60 (m, 2H),
13C NMR (CDCl3):
d 198.9 (CH), 156.2 (C), 144.0 (C), 143.9 (C),
4.71e4.60 (m,1H), 3.99e3.74 (m, 2H), 3.35e3.27 (m,1H), 2.46e2.23
(m, 4H), 1.77 (d, J¼7.0 Hz, 3H).
141.5 (C), 127.9 (CH), 127.2 (CH), 125.3 (CH), 125.2 (CH), 120.2 (CH),
67.4 (CH2), 62.0 (CH), 61.4 (CH2), 47.3 (CH), 25.9 (CH3), ꢀ5.4 (CH3),
ꢀ5.4 (CH3).
13C NMR (CD3OD):
d 131.7 (CH),131.7 (CH),131.6 (CH),131.1 (CH),
129.9 (CH), 128.6 (CH), 87.4 (C), 76.4 (C), 59.3 (CH), 58.4 (CH2), 57.2
(CH), 31.3 (CH2), 18.3 (CH2), 17.0 (CH3).
ESI-MS m/z C24H31NO4Si [MþH]þ Found: 426.2087; Calculated:
426.2101.
ESI-MS m/z C14H21NO2 [MþH]þ Found:236.1655; Calculated:
236.1651.
4.11. (9H-Fluoren-9-yl)methyl ((2S,3R:S,4E,8E,10E,
12E,14E,16E)-1-((tert-butyldimethyl-silyl)oxy)-3-hydroxy-oc-
tadeca-4,8,10,12,14,16-hexaen-2-yl)carbamate (15)
4.13. (2S,3R,8E,10E,12E,14E,16E)-1,3-Dihydroxyoctadeca-
8,10,12,14,16-pentaen-4-yn-2-amonium chloride (2)
Following the same protocol described for 1, the protected
amino diol 9 (20 mg, 0.04 mmol) afforded amino diol 2$HCl 6 mg in
40% yield.
To a flame-dried Schlenk with a suspension of Cp2Zr(H)Cl
(100 mg, 0.4 mmol) in DCM (0.4 mL), was added a solution of the
alkyne (all-E)-7 (55 mg, 0.3 mmol) in anhydrous DCM (0.4 mL), at
Rf: 0.46 (DCM:MeOH; 8:2); [
a
]D: ꢀ4.2 (c 1, CH3OH).
0
ꢁC under Ar and protected from light. During warming to room
1H NMR (CD3OD):
d
6.38e5.94 (m, 8H), 5.84e5.63 (m, 2H),
temperature, the zirconocene complex gradually dissolved to give
a clear red solution (20 min). A solution of the aldehyde 14 (91 mg,
0.2 mmol) in DCM (0.6 mL), previously activated for 10 min with
ZnCl2 (15 mg, 0.1 mmol, dried under vacuum for 1 h before use), was
added to the reaction mixture. The solution was stirred for 30 min at
rt and turned clear orange. Next, it was diluted with DCM (2 mL) and
stirred with a 10% aqueous potassium sodium tartrate solution
(2 mL) for 10 min. The resulting suspension was filtered through
a pad of CeliteÒ and washed thoroughly with DCM (5 mL). The
combined filtrates were successively washed with H2O and brine.
The aqueous phase was extracted with DCM (3ꢂ10 mL), and the
combined organic layers were dried over Mg2SO4. Purification by
flash chromatography with silica-gel neutralized with Et3N (1% vol,
using hexane as solvent) (hexane:EtOAc; stepwise gradient from
0 to 10% of EtOAc) afforded 15 in 20% yield as a 1:1.5 anti:syn mixture.
Rf: 0.43 (syn); 0.37 (anti) (hexane:EtOAc; 8:2).
4.71e4.62 (m, 1H), 4.02e3.87 (m, 1H), 3.86e3.71 (m, 2H), 2.45e2.13
(m, 4H), 1.77 (d, J¼6.5 Hz, 3H).
ESI-MS m/z C18H25NO2 [MþNa]þ Found: 310.1779; Calculated:
310.1783; [MþH]þ Found:288.1954; Calculated: 288.1964.
Analytical HPLC conditions for 2$HCl: Column (Kromasil 100,
C18, 5
acetate (pH¼4.8, 140 mM):ACN). Sample (v:50
DMSO); ( : 331 nm). Rt: 8.8 min; labs (nm) 275, 315, 346; lem (nm)
440, 456, 470.
m
m, 15ꢂ0.4 cm). Isocratic method (60:40, Buffer sodium
m
L, 2 at 1 mg/mL
l
FF
(
lex: 346 nm, ethanol, 9,10-DPA as reference): 0.065;
3 (lex
max¼325 nm): 12,790 Mꢀ1 cmꢀ1
.
4.14. (2S,3(R:S),4E,8Z:E,10E,12E)-1,3-Dihydroxytetradeca-
4,8,10,12-tetraen-2-aminium chloride (3)
1H NMR (CDCl3): From a mixture of diastereomers.
Following the method described for amino diol 1, protected 10
(syn:anti 1:1) (185 mg, 0.5 mmol) afforded aminodiol 3$HCl
(160 mg) in quantitative yield as a 1:1 syn:anti mixture.
Rf: (syn:anti 1:1) 0.40 (DCM:MeOH; 85:15).
(anti):
d
7.77 (d, J¼8.0 Hz, 2H), 7.60 (d, J¼7.5 Hz, 2H), 7.40 (ddt,
J¼8.5, 7.5, 1.5 Hz, 2H), 7.31 (tt, J¼7.5, 2.0 Hz, 2H), 6.30e5.88 (m, 8H),
5.91e5.21 (m, 4H), 5.05 (d, J¼13.0 Hz, 1H), 4.54e4.30 (m, 3H), 4.23

I. Nieves et al. / Tetrahedron 72 (2016) 605e612
611
1H NMR (CDCl3): (2S,3R:S) (4E,8E,10E,12E)
d
6.26e5.80 (m,
References and notes
5H), 5.76e5.42 (m, 3H), 4.47e4.26 (m, 1H), 3.92 (s, 1H), 3.84e3.42
(m, 2H), 3.31e3.20 (m, 1H), 2.27e2.04 (m, 4H), 1.76 (d, J¼7.0 Hz,
3H).
d 133.5 (CH), 133.0
(CH), 131.9 (CH), 131.3 (CH), 130.5 (CH), 130.4 (CH), 129.9 (CH), 129.5
1. Fang, Z.; Song, Y.; Zhan, P.; Zhang, Q.; Liu, X. Future Med. Chem. 2014, 6,
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2. Lee, S.; Lee, S.; Park, H. J.; Lee, S. K.; Kim, S. Org. Biomol. Chem. 2011, 9,
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3. Ballereau, S.; Baltas, M.; Genisson, Y. Curr. Org. Chem. 2011, 15, 953e986.
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4. Rives, A.; Genisson, Y.; Faugeroux, V.; Zedde, C.; Lepetit, C.; Chauvin, R.; Saffon,
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ESI-MS m/z C14H23NO2 [MþNa]þ Found: 260.1610; Calculated:
5. Nakayama, S.; Uto, Y.; Tanimoto, K.; Okuno, Y.; Sasaki, Y.; Nagasawa, H.; Nakata,
E.; Arai, K.; Momose, K.; Fujita, T.; Hashimoto, T.; Okamoto, Y.; Asakawa, Y.;
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260.1626.
Analytical HPLC conditions: Column (Kromasil 100, C18, 5 mm,
15ꢂ0.4 cm). Isocratic method (25:75, buffer sodium acetate
(pH:4.8, 140 mM): ACN). Sample (v:25
254 nm). Rt: 17.6 min and 19.7 min.
mL, 3 at 1 mg/mL DMSO); (l:
9. Kim, S.; Lee, Y. M.; Kang, H. R.; Cho, J.; Lee, T.; Kim, D. Org. Lett. 2007, 9,
2127e2130.
4.15. N-((2S,3R:S,4E,8E,10E,12E,14E,16E)-1,3-Dihydroxyoctad
eca-4,8,10,12,14,16-hexaen-2-yl) palmitamide (4)
10. Salma, Y.; Ballereau, S.; Maaliki, C.; Ladeira, S.; Andrieu-Abadie, N.; Genisson, Y.
Org. Biomol. Chem. 2010, 8, 3227e3243.
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12. Kuerschner, L.; Ejsing, C. S.; Ekroos, K.; Shevchenko, A.; Anderson, K. I.; Thiele,
C. Nat. Methods 2005, 2, 39e45.
Compound 15 (20 mg, 0.03 mmol) compound was dissolved in
anhydrous THF (0.5 mL) under Ar. Next, 35 L of TBAF solution was
~
13. Quesada, E.; Delgado, J.; Hornillos, V.; Acuna, U.; Amat-Guerri, F. Eur. J. Org.
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Chem. 2007, 2007, 2285e2295.
added via syringe (0.04 mmol, 1 M in THF). The solution turned
orange immediately. After being stirred for 1 h at rt, it was ob-
served by TLC part of the starting material, then to the reaction
14. Nieves, I.; Artetxe, I.; Abad, J. L.; Alonso, A.; Busto, J. V.; Fajari, L.; Montes, L. R.;
Sot, J.; Delgado, A.; Goni, F. M. Langmuir 2015, 31, 2484e2492.
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15. Ernst, A. M.; Contreras, F.-X.; Thiele, C.; Wieland, F.; Brugger, B. Biochim. Bio-
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mixture was added an additional 15 mL of TBAF solution (1 M in
THF) to fulfil the conversion. After 30 min, a saturated aqueous
NH4Cl (0.5 mL) solution was added, and the mixture was dried
with MgSO4 and the resulting amino diol was eluted to another
flask with DCM. The solvent was concentrated under reduced
pressure and the crude was used in the next reaction without
further purification.
17. Wang, T. Y.; Silvius, J. R. Biophys. J. 2000, 79, 1478e1489.
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€
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d 6.27e5.80 (m, 5H), 5.86e5.52 (m, 3H),
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~
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5.53e5.30 (m, 2H), 5.13e5.03 (m, 1H), 5.03e4.83 (m, 2H),
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ESI-MS m/z C34H57NO3 [MþH]þ Found: 528.4432; Calculated:
528.4417.
labs (nm) 315, 325, 345; lem (nm) 440, 465, 500. FF (lex: 346 nm,
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3
(lex max¼325 nm):
10,781 Mꢀ1 cmꢀ1
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This work was supported in full by the ‘Fundacion Biofisica
Bizkaia’ and, in part, by the Spanish ‘Ministerio de Economía y
Competitividad’ (Project CTQ2014-54743). I.N. was supported by
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a contract sponsored by the ‘Fundacion Biofisica Bizkaia’ and by
a JAE-predoc fellowship (CSIC).

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