Extended structural modulation of bio-inspired chiral lipidic alkynylcarbinols as antitumor pharmacophores

Article abstract of DOI:10.1016/j.tet.2015.08.003

The chiral alkynylcarbinol motif typically found in natural marine products, has been the subject of intense research activity for its pharmacophoric properties, in particular cytotoxicity against tumor cell lines. In a chemical synthesis-driven four-parameter structure-activity relationship (SAR) study from the (S,E)-eicos-4-en-1-yl-3-ol natural reference 1, the (S)-dialkynylcarbinol unit of the non-natural dehydro derivative 2 emerged as an unprecedented anti-tumoral pharmacophore. An extended study of lipidic alkynylcarbinol pharmacophores is presented, addressing additional structural parameters: Z→E isomerization of the alkenyl carbinol substituent of 1, variation of the lipidic chain length of 2 (C_3n, n=3, 4, 6), oxidation or substitution of the carbinol unit of 2 (to ketone, tertiary methylcarbinol, or methylether), cyclomethylenation of the double bond of 1. The synthesis of these analogues is described, including the preparation of enantio-enriched chiral alkynylcarbinol derivatives using a modified Carreira procedure for Zn-mediated addition of (trialkylsilyl)acetylene substrates to ynals in the presence of (-)- or (+)-N-methylephedrine. Preliminary cytotoxicity evaluation of 12 new products against the HCT 116 tumor cell line are finally reported and the results compared with those obtained for 1 and 2. These observations support and refine the relevance of the pharmacophoric character of secondary DAC units.

Full text of DOI:10.1016/j.tet.2015.08.003

Tetrahedron 71 (2015) 7920e7930
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Extended structural modulation of bio-inspired chiral lipidic
alkynylcarbinols as antitumor pharmacophores
,
b
,
c
,
,
Dymytrii Listunov a
d, Chelmia Billot a b, Etienne Jolye, Isabelle Fabing c,
d
c
,
a,
b,
a,b,
*
*
*
ꢀ
ꢀ
Yulian Volovenko , Yves Genisson , Valerie Maraval
a UPR CNRS 8241, LCC (Laboratoire de Chimie de Coordination), 205 Route de Narbonne, BP 44099, 31077 Toulouse Cedex 4, France
, Remi Chauvin
b
ꢀ
ꢀ
Institut de Chimie de Toulouse, ICT-FR2599, Universite de Toulouse, Universite Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse, France
c
ꢀ
ꢀ
UMR CNRS 5068, LSPCMIB, Universite de Toulouse, Universite Paul Sabatier, 118 Route de Narbonne, 31062 Toulouse Cedex 9, France
d Department of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska Street 64/13, Kyiv 01601, Ukraine
e UMR CNRS 5089, IPBS (Institut de Pharmacologie et de Biologie Structurale), 205 Route de Narbonne, 31077 Toulouse Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 June 2015
Received in revised form 29 July 2015
Accepted 1 August 2015
Available online 6 August 2015
The chiral alkynylcarbinol motif typically found in natural marine products, has been the subject of
intense research activity for its pharmacophoric properties, in particular cytotoxicity against tumor cell
lines. In a chemical synthesis-driven four-parameter structureeactivity relationship (SAR) study from the
(S,E)-eicos-4-en-1-yl-3-ol natural reference 1, the (S)-dialkynylcarbinol unit of the non-natural dehydro
derivative 2 emerged as an unprecedented anti-tumoral pharmacophore. An extended study of lipidic
alkynylcarbinol pharmacophores is presented, addressing additional structural parameters: Z/E isom-
erization of the alkenyl carbinol substituent of 1, variation of the lipidic chain length of 2 (C3n, n¼3, 4, 6),
oxidation or substitution of the carbinol unit of 2 (to ketone, tertiary methylcarbinol, or methylether),
cyclomethylenation of the double bond of 1. The synthesis of these analogues is described, including the
preparation of enantio-enriched chiral alkynylcarbinol derivatives using a modified Carreira procedure
for Zn-mediated addition of (trialkylsilyl)acetylene substrates to ynals in the presence of (ꢀ)- or (þ)-N-
methylephedrine. Preliminary cytotoxicity evaluation of 12 new products against the HCT 116 tumor cell
line are finally reported and the results compared with those obtained for 1 and 2. These observations
support and refine the relevance of the pharmacophoric character of secondary DAC units.
Ó 2015 Elsevier Ltd. All rights reserved.
This article is dedicated to the memory of
Jean Buendia (1932e2015), head of the
process research department at the Roussel-
Uclaf company when the last author of this
report was working under his valuable and
benevolent guidance
Keywords:
Alkyne
Antitumor agent
Asymmetric synthesis
Cytotoxicity
Lipidic alkynylcarbinol
1. Introduction
and Strongylophora sp.,9 respectively, and the neuritogenic lembe-
hyne A,10 extracted from Haliclona sp.,3 are representative exam-
Among the hundred of natural products exhibiting an oligoa-
cetylenic structure, those containing a chiral propargylic alcohol on
a lipidic skeleton constitute a well-identified subclass continuously
inspiring topical interest in medicinal and synthetic chemistry.1
Most of these alkynylcarbinols, often multi-functional, have been
extracted from marine sponges and reported to display various
biological effects, including RNA cleavage activity,2 neu-
ritogenicity,3 or anti-viral properties, in particular against HIV.4 The
foremost activity of these lipidic alkynylcarbinols is however their
in vitro cytotoxicity against several tumor cell lines.5 The cytotoxic
petrocortyne A6 and strongylodiol A,7 extracted from Petrosia sp.2,8
ples of such metabolites (Fig. 1). Inspection of the whole family
shows that the propargylic alcohol moiety is a minimal pharma-
cophoric unit, which is also found in simple natural lipids isolated
from Cribrochalina vasculum.11 One of these natural products, (S,E)-
eicos-4-en-1-yl-3-ol 1, is a lipidic alkenyl-alkynylcarbinol (AAC)
which was recently invoked as a reference for a systematic study of
the cytotoxic activity of propargylic alcohol-based pharmacophoric
units.12 The four structural parameters first considered were the
following ones: the absolute configuration of the carbinol center,
the unsaturation level of the terminal C2 carbinol substituent, the
unsaturation level of the lipidic carbinol substituent, and the length
of the lipidic chain (Fig. 1). Regarding cytotoxicity toward the HCT
116 cell line, four main structureeactivity relationship (SAR) trends
emerged: (i) the activity of the enantiomers differ by at least one
order of magnitude in a chemically correlated manner (the natural
* Corresponding authors. E-mail addresses: genisson@chimie.ups-tlse.fr
ꢀ
(Y. Genisson), valerie.maraval@lcc-toulouse.fr (V. Maraval), chauvin@lcc-toulouse.fr
(R. Chauvin).
http://dx.doi.org/10.1016/j.tet.2015.08.003
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.

D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
7921
OH
14
14
4
H
1
4
(S)-eicos-(4E)-en-1-yn-3-ol
OH
OH
H
OH
petrocortyne A
6
H
H
2
OH
OH
15
2
R1
7
lembehyne A
*
H
R2
11
2
non natural
OH
7
(R)-strongylodiol A
8
HO
further
investigations:
O
OH
OMe
Me
H
(CH2)11Me
H
(CH2)11Me
H
(CH2)11Me
OH
OH
(CH2)11Me
OH
(CH2)11Me
H
1 or 2
H
(CH2)nMe
H
n = 8, 17
OH
OH
(CH2)11Me
(CH2)11Me
H
Fig. 1. Examples of bio-active natural lipidic polyacetylenic alcohols having inspired the identification of alkynylcarbinols as cytotoxic antitumor pharmacophores, such as the
artificial DAC 2, and proposed structural modulations of 1 and 2.
product 1 being the distomer); (ii) the most active derivatives
possess two unsaturations next to the carbinol center, and at least
one triple bond (the unnatural dehydro derivative of 1 being more
active than 1); and (iii) the cytotoxic activity is dramatically influ-
enced by the chain length (a truncated homologue of 1 being more
active than 1). These investigations brought out the lipidic dia-
lkynylcarbinol (DAC) 2 as being two orders of magnitude more
cytotoxic against HCT 116 cancer cells (IC50z60e90 nM) than the
original (S)-configured natural AAC product 1 (Fig. 1).12
here envisaged for the previously identified more potent DAC de-
rivative 2.12 The synthesis of chiral lipidic propargylic alcohols was
envisaged by Zn-mediated enantioselective addition of terminal
alkynes to aldehydes (Scheme 1).13 The known methods involve in
situ generation of alkynylzinc reagents generated from commer-
cially available sources of Zn(II). The first procedure, described by
Carreira et al. in 2000, relies on the user-friendly precursor salt
Zn(OTf)2 (Tf¼CF3SO2).14 This was, however, reported to be in-
efficient from aliphatic or a,b
-unsaturated aldehydes,15 and alter-
Five kinds of structural modulation of the chiral lipidic alky-
nylcarbinols 1 or 2 were envisaged: (i) variation of the length of the
lipidic chain of 2 (C3n, n¼3, 4, 6), (ii) inversion of the configuration
of the double bond of 1 (from E to Z), (iii) alteration of the redox
state and substitution pattern of the carbinol center of 2 (from
secondary carbinol to carbonyl and tertiary carbinol, from alcohol
to ether), (iv) introduction of a cyclopropylene group in place of the
ethene or ethyne fragment of 1.
native processes have been developed, in particular with the view
to asymmetric total synthesis of marine acetylenic lipids. In 2002,
Pu et al. reported a system based on the combination of (þ)- or
(ꢀ)-BINOL and Ti(OiPr)4 as a chiral Lewis acidic auxiliary, giving
high ee’s from various substrates.16 Trost et al. proposed the use of
ProPhenol as a chiral ligand of Zn(II),17 while Zhong and Guo de-
scribed the alternative use of a cyclopropane-containing 1,4-
aminoalcohol ligand (Scheme 1).18
In 2006, a modified Carreira procedure was applied to the par-
ticular case of the double-headed acetylenedicarbaldehyde cobalt
complex 3, giving the triynediol 4 with high stereoselectivity
(Scheme 2).19 The method, based on the use of four equivalents of
zinc triflate, N-methylephedrine and alkyne per equivalent of dia-
ldehyde in dichloromethane (DCM), was thus envisaged for the
synthesis of non-natural lipidic DAC targets.
2. Results and discussion
2.1. Synthesis of the lipidic alkynylcarbinol targets
The preparation of the targeted analogues of 1 or 2 is described
hereafter.
Considering the C12 chain of the highly cytotoxic DAC 2 and the
dramatic influence of the chain length in the parent AAC series
(defined from 1),12 a shorter C9 chain and a longer C18 chain were
first envisaged for an extension of the lipidic DAC series. The cor-
responding alkyne precursors 5 and 6 were synthesized by a two-
step sequence from 1-bromononane and 1-bromooctadecane,
2.1.1. Variation of the lipidic chain length of 2. It was recently shown
that truncating the lipidic chain of the natural AAC (S,E)-eicos-4-en-
1-yl-3-ol 1 by three methylene units resulted in a five-fold increase
in the cytotoxic potency. While a finer tuning of the lipophilic
backbone of AACs deserves consideration, the chain length effect is

7922
D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
OH
n
O
+
H
n
TMS
Pu's system
giving the (R) enantiomer
Zhong and Guo's system
giving the (S) enantiomer
Carreira's system
giving the (R) enantiomer
Trost's system
giving the (R) enantiomer
(S)-BINOL (0.4 eq.)
Et2Zn (4 eq.)
Ti(OiPr)4 (1 eq.)
(+)-NME (1.2 eq.)
Zn(OTf)2 (1.1 eq.)
Et3N (1.2 eq.)
(S,S)-ProPhenol (10 mol%)
Me2Zn (3 eq.)
Toluene, 4 oC
Ligand (20 mol%)
Me2Zn (3 eq.)
Toluene, 48 h, 0 oC
Toluene, r.t.
Toluene, Et2O, r.t.
Ph
OH
Ph
Ph
Ph
HO
OH N
Ph
Ph
Me2N
Me
OH
Ph
N
OH
OH
N
OH
TBSO
(+)-NME
Ligand
(S,S)-ProPhenol
(S)-BINOL
Scheme 1. Procedures for the enantioselective addition of terminal alkynes to aldehydes used in the synthesis of natural alkynylcarbinols.14,16e18
Scheme 2. Application of the modified Carreira system to the stereoselective addition of trimethylsilylacetylene to cobalt-stabilized acetylenedicarbaldehyde.19
respectively (Scheme 3), by alkylation of trimethylsilylacetylene,20
followed by proto-desilylation with potassium carbonate in
methanol.
paraformaldehyde. Hydrogenation of 16 into the (Z)-configured
allylic alcohol 17 was then performed using the Lindlar catalyst
(89% yield). After quantitative MnO2-mediated oxidation of 17 to
the poorly stable aldehyde 18, addition of ethynylmagnesium bro-
mide led to the (Z)-AAC 14 with 65% yield (Scheme 4).
Reaction of the TMS-protected propynal 7 with the terminal
alkynes 5 and 6 through the modified Carreira procedure in the
presence of (þ)- or (ꢀ)-N-methylephedrine, afforded the dia-
lkynylcarbinols (S)-8 and (S)-9, or (R)-8 and (R)-9, respectively.
Subsequent condensation of these four products with 1-naphthyl
isocyanate yielded the corresponding 1-naphthyl carbamate de-
rivatives 10 and 11, respectively (Scheme 3), which were analyzed
by chiral supercritical fluid chromatography (SFC). The high ee
values are consistent with those previously recorded in the syn-
thesis of analogous chiral DACs by the same modified Carreira
procedure.12 Proto-desilylation of 8 and 9 with K2CO3/MeOH led to
the targeted enantio-enriched dialkynylcarbinols 12 and 13. Very
recently, the efficiency of the modified Carreira procedure also
revealed key to demonstrate the dramatic impact of the absolute
chiral configuration on the in vitro antitumor activity of C2-sym-
metrical double-headed bis-DAC derivatives.21
2.1.3. Variation of the oxidation state and substitution pattern of the
carbinol center of 2. A possible mechanism of biological activity of
alkynylcarbinol pharmacophores would rely on their in cellulo
metabolic oxidation into the corresponding ketones.22 The potency
of the secondary DAC 2 naturally suggested comparison with the
cytotoxic activity of the corresponding dialkynylketone 19. Con-
versely, oxidation-protected derivatives of 2, namely the isomeric
tertiary methylcarbinol 20 and methyl ether 21, were also consid-
ered (Scheme 5).
The synthesis of 19, 20 and 21 called for the intermediate ra-
cemic dialkynylcarbinols (rac)-22aeb, prepared by addition of the
lithium salt of undec-1-yne to the C-silylated propynal derivatives
7aeb. The dialkynylketone 19 was then synthesized in two steps,
by proto-desilylation of 22a to (rac)-2, followed by oxidation using
the DesseMartin periodinane reagent.23 Starting from the same
precursor 22a, the tertiary carbinol 20 was synthesized in three
steps, by PCC-mediated oxidation to the ketone 23, addition of
MeMgBr giving the methylcarbinol 24 with 93% yield, and proto-
desilylation of the latter. The synthesis of the methyl ether 21 re-
quired recourse to the more stable precursor 22b which was
deprotonated with n-Buli, then O-methylated with MeI to give
the ether 25, which was in turn desilylated with TBAF in THF
(Scheme 5).
2.1.2. Variation of the configuration of the double bond of 1. While
the (E)-AAC unit is widely encountered in marine natural products,
the (Z)-AAC unit is barely found in Nature. The cis-fused bis-
alkenyl-alkynylcarbinol core of the C2-symmetrical petrosynol is
a notable exception (Scheme 4). The racemic (Z)-AAC 14 with a C12
alkyl chain was thus targeted for comparison of its biological ac-
tivity with that of the previously described (E)-AAC isomer 15.12
The propargylic alcohol 16 was first prepared, with 70% yield, by
treatment of tetradec-1-yne with n-butyllithium and, then,

D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
7923
HN
Br
R
R
R
O
O
TMS
H
n-BuLi, HMPA
n-Bu4NI, THF
S
R
TMS
R = n-C8H17, (S)-10, 80 %, 90 % ee
R = n-C17H35, (S)-11, 85 %, 90 % ee
TMS
K2CO3
MeOH
1-naphthyl isocyanate
DBU, DCM
H
(+)-NME (4 eq.)
Zn(OTf)2(4 eq.)
Et3N (4 eq.)
OH
OH
K2CO3
S
R
R = n-C8H17, 5
R = n-C17H35, 6
R
R
DCM
MeOH
H
TMS
R = n-C8H17, (S)-8, 55 %
R = n-C17H35, (S)-9, 60 %
R = n-C8H17, (R)-12, 85 %,
R = n-C17H35, (R)-13, 75 %
O
(4 eq.)
H
(-)-NME (4 eq.)
Zn(OTf)2(4 eq.)
Et3N (4 eq.)
OH
OH
TMS
7
K2CO3
MeOH
R
S
R
R
TMS
DCM
H
R = n-C8H17, (S)-12, 80 %
R = C8H17, (R)-8, 50 %
R = C17H35, (R)-9, 55 %
R = n-C17H35, (S)-13, 80 %
1-naphthyl isocyanate
DBU, DCM
HN
O
O
R
R
TMS
R = n-C8H17, (R)-10, 80 %, 93 % ee
R = n-C17H35, (R)-11, 85 %, 92 % ee
Scheme 3. Enantioselective syntheses of homologues of the DAC 2, with shortened (12) or elongated (13) lipidic chains.
OH
OH
HO
OH
H
H
11
HO
OH
11
(E)
(Z)
(rac)-14
H
H
6
6
(rac)-15
H
MgBr
1)
petrosynol
HO
65 %
O
2) NH4Cl
H
HO
Lindlar, H2
MnO2
DCM
1) n-BuLi
H
pyridine
89 %
2) (CH2O)n
70 %
11
11
11
quant.
11
16
17
18
Scheme 4. Natural petrosynol embedding a cis-fused bis-alkenyl-alkynylcarbinol core, and synthesis of the stereochemically related non-natural (Z)-AAC (rac)-14.
2.1.4. Cyclomethylenation of the double bond of 1. The occurrence of
at least one triple bond and two unsaturated substituents at the
carbinol center was shown to be a key structural factor for the
cytotoxic activity of lipidic carbinols (e.g. 1 and 2).12 Beyond C2-
unsaturated alkenyl and alkynyl substituents, C3-pseudo-un-
saturated cyclopropyl substituents are iso-diametral to the formers
with respect to the carbinol center (Max[HOC/C(insat)]¼
yield by addition of the lithium salt of tetradeca-1-yne to cyclo-
propane carboxaldehyde. The racemic trans-diastereoisomer of the
internal CAC 27 was obtained in five steps from the same alky-
nyllithium salt, through the propargylic alcohol 16.25 Following
a classical procedure,26 reduction of 16 with LiAlH4 quantitatively
afforded the (E)-allylic alcohol 28,27 Zn/Ti-mediated methylenation
of which giving the cyclopropylcarbinol 29 with 67% yield and
a complete trans stereoselectivity.28 After PCC-mediated oxidation
of 29, the resulting trans-substituted cyclopropane carboxaldehyde
30 was reacted with ethynyl magnesium bromide to give the
cyclopropylalkynylcarbinol 27 with 65% yield, as a 50:50 mixture of
diastereoisomers 27a and 27b, which could not be assigned to ei-
ther the threo or erythro configuration, but could be resolved by
silica gel chromatography. In the absence of crystallographic data,
ꢁ
2.55ꢁ0.10 A), and may thus be regarded as potential bioisosteres of
alkyne or alkene moieties.24 Two cyclopropylene homologues of 2
and 15 (an optimized truncated homologue of the natural product
1) were considered in the racemic series, namely the cyclo-
propylalkynylcarbinols (CACs) 26 and 27 bearing the cyclopropyl
substituent at the terminal and internal position, respectively
(Scheme 6). The racemic terminal CAC 26 was obtained with 72%

7924
D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
OH
O
PCC
DCM
H
1) n-BuLi
O
2)
E
E = TMS TMS
75 %
7a: E = TMS : 74 %
7b: E = TIPS: 64 %
11
11
11
H
(rac)-22a: E = TMS
(rac)-22b: E = TIPS
23
E
3) NH4Cl
1) MeMgBr
2) NH4Cl
1) n-BuLi
2) MeI
93 %
E = TIPS
50 %
K2CO3
MeOH
E = TMS
75 %
OH
OMe
OH
Me
24
H
TIPS
TMS
11
11
11
(rac)-2
(rac)-25
TBAF
Dess-Martin
periodinane
K2CO3
70 %
85 %
83 %
MeOH
THF
DCM
O
OMe
OH
Me
(rac)-20
H
H
H
11
11
11
19
(rac)-21
Scheme 5. Syntheses of the dialkynylketone 19 and oxidation-protected DAC derivatives of 2, the tertiary dialkynylcarbinol 20 and methyl ether 21. TMS¼Me3Si, TIPS¼iPr3Si.
OH
H
1) n-BuLi, THF
O
11
2)
3) NH4Cl
72 %
11
26
H
CH2I2
Et2Zn, Ti(OiPr)4
HO
LiAlH4
HO
HO
11
11 THF, reflux
99 %
DCM
67 %
11
16
28
29
O
HO
HO
PCC
DCM
72 %
H
MgBr
29
+
H
THF
65 %
11
11
11
H
H
rac-trans
erythro (R*,S*)-trans
threo (R*,R*)-trans
30
27 (27a and 27b)
Scheme 6. Syntheses of the cyclopropylene homologues of 2 and 15, the terminal CAC 26 and internal CAC 27, in the racemic series.
the structures of the threo (R*,R*) and erythro (R*,S*) di-
a standard in all experiments (IC50 in the range 90e160 nM:
Table 1).
The DACs 12 and 13, with truncated and elongated lipidic chains
respectively, were found to be both less cytotoxic than the opti-
mized parent DAC (S)-2 (IC50z0.1 M), but the general stereo-
chemical trend in favor of the (S)-configured derivatives was
retained (Table 1):12 the IC50 values in the eutomeric series remain
submicromolar (600 nM for (S)-12, 360 nM for (S)-13), and signif-
icantly inferior to those of the corresponding (R) enantiomers
astereoisomers of a simplified model of 27 (¼27aþ27b) defined by
truncating the lipidic chain to a methyl group, were calculated at
the DFT level (B3PW91/6-31G(d,p)).24b The optimized geometries,
of similar energies (
D
E¼1.6 kcal/mol), correspond to staggered
m
conformations (Fig. 2), showing that the steric crowding of the
alkynylcarbinol unit is much larger in CACs than in AACs and DACs
(see Section 2.2 and S. D.).
2.2. First insights into the cytotoxic activity of the synthe-
sized alkynylcarbinols
(>50 mM for (S)-12, 2.23 mM for (S)-13). The unnatural reference
DAC (S)-2 with an n-C12H25 lipidic chain remains the most cytotoxic
of the n-C3nH6nþ1 homologue series for n¼3, 4, 6. Further efforts
will have to be undertaken in the DAC series for n¼5 (the corre-
sponding C15 chain being the one of the natural AAC 1), and for
a finer tuning between C10 and C17 (or C14 depending on the results
for the C15 homologue).
For the sake of preliminary comparison with previously re-
ported data, the cytotoxicity of the synthesized alkynylcarbinol
derivatives was evaluated against the human colon carcinoma
cell line HCT116.12 The reference compound (S)-2 was used as

D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
7925
Fig. 2. Newman views and energies of DFT-optimized geometries of models of the threo and erythro isomers of 27 (¼27aþ27b), where the lipidic chain is represented by a methyl
group. Level of calculation: B3PW91/6-31G(d,p).24b Hydrogen atoms at the rear are omitted for clarity. See Supplementary data.
Table 1
the secondary DAC pharmacophore, the reported preliminary cell
viability study will be extended to a larger panel of tumor cells. In
Preliminary evaluation of alkynylcarbinols for cytotoxicity against HCT 116 cancer
cells
future investigations, specific synthetic methodologies described
here and elsewhere,12,13,21,29 as well as other approaches, will be
also applied for further structural modulation of the pharmaco-
phoric unit. With a view to gaining insight into the cellular mode of
action of these products, labeling of the reference lipidic DAC by
terminal fluorescent probes will also be envisaged.
DAC derivatives
IC50
[
m
M]
AAC or CAC derivatives
IC50 [mM]
(S)-2
0.09e0.160a,b
(rac)-15
(rac)-14
(rac)-26
(rac)-27a
(rac)-27b
0.55a,12
(S)-12
(R)-12
(S)-13
(R)-13
19
(rac)-20
(rac)-21
(rac)-25
0.60a
19a
>50a
>50a
>10b
>10b
0.36a
2.23a
>50a
>50a
3.1. Experimental section
>10b
>10b
3.1.1. General. THF and diethyl ether (Et2O) were dried and distilled
over sodium/benzophenone, dichloromethane (DCM) over CaH2,
and pyridine over KOH. All the other solvents, petroleum ether (PE)
in particular, and reagents were used as commercially available. The
commercial solutions of n-BuLi used were 1.6 M or 2.5 M in hexanes,
solutions of ethynylmagnesium bromide were 0.5 M in THF, and
solutions of methylmagnesium bromide were 3 M in diethyl ether.
Analytical thin-layer chromatography (TLC) was performed with
0.25 mm plates 60F254. TLC plates were observed under UV-light
and/or revealed with a 20% phosphomolybdic acid ethanolic solu-
a
Cells were seeded in 96-well plates and were treated with concentrations
M; after 96 h, the number of live cells was evaluated by
ranging from 10 nM to 50
m
a WST test (see Experimental procedures).
b
Cells were seeded in 96-well plates and were treated with concentrations
ranging from 10 nM to 10 mM; after 48 or 72 h, the number of live cells was eval-
uated by a standard MTT test (see Experimental procedures).
The cytotoxicity of the (Z)-AAC (rac)-14 with a C12 lipidic chain
was found 30 times weaker than that of the previously described
(E)-AAC isomer (rac)-15 (IC50¼19
mM vs 0.555 m
M).12
The ketone 19 and methylated DAC derivatives (the tertiary DAC
20, ether 21 and its highly lipophilic triisopropylsilylated precursor
25) were found completely inactive in the investigated range of
ꢁ
tion. Column chromatography was carried out on silica gel 60 A,
70e230 mesh. The following analytical instruments were used: 1H
and 13C NMR: Bruker Avance 300 or Avance 400 spectrometers.
Mass spectrometry (MS): ThermoQuest TSQ 7000 spectrometer.
High-resolution mass spectrometry (HRMS): Thermo-Finnigan MAT
95 XL instrument. Infrared (IR): PerkineElmer Spectrum 100 FTIR
spectrometer. Optical rotations: Jasco P-2000 polarimeter. Chiral
SFC: Acquity UPC2 System by Waters and SFC PIC Lab Analytic by Pic
concentrations (IC50>10 mM). The same lack of activity was recor-
ded for the racemic CACs 26 and 27, bearing cyclopropylene units as
pseudo-unsaturated substituents (iso-diametral to the ethenylene
and ethynylene unsaturations of the reference AACs 1 or 15 and
DAC 2). It can be incidentally noticed that the decrease of cyto-
toxicity in the order DAC>(E)-AAC>(Z)-AAC>CAC happens to par-
Solution with column Chiralpak AD-H 5
mm (4.6ꢂ250 mm).
allel an increase of a,b steric crowding of the alkynylcarbinol center
(Fig. 2 and S.D.). The observations might give a qualitative guideline
for further optimisation of the pharmacophore structure. Overall,
these first biological data already confirm and refine the relevance
of the pharmacophoric character of secondary DAC units.
3.1.2. General procedure for enantioselective addition of terminal
alkynes to aldehydes. A 25 mL flask was charged with Zn(OTf)2
(4 equiv) and (þ) or (ꢀ) N-methylephedrine (4 equiv) and purged
with dry argon for 15 min. Then, DCM (10 mL) and triethylamine
(4 equiv) were added. The resulting mixture was vigorously stirred
for 2 h at rt before addition in one portion of a solution of the alkyne
3. Conclusion
(4 equiv) in DCM (15 mL). After
1
h
stirring, 3-
The lipidic DAC fragment recently highlighted as potent cyto-
toxic pharmacophore,12 has thus been modified along four di-
rections of structural modulation of the reference compound 2.
Although the envisaged alterations did not lead to any absolute
improvement with respect to 2 (in terms of IC50 values against HCT
116 cells), the disclosed preliminary biological data further sub-
stantiate the significance of the (S)-1,4-diyn-3-ol DAC moiety as
a pharmacophore for cytotoxicity. In addition to a strong de-
pendence of the antitumor potency on both the lipidic chain length
and absolute configuration of the carbinol center, the present re-
sults establish the requirement of a free hydroxyl group, a second-
ary carbinol center, and a truly C2 unsaturated substituent of the
alkynylcarbinol motif. To further refine the cytotoxicity profile of
alkynylcarbinol derivatives and delineate further the relevance of
trimethylsilylpropiolaldehyde (1 equiv) was added, and the mix-
ture was stirred at rt overnight. After treatment with a saturated
aqueous NH4Cl solution, the aqueous layer was extracted with DCM
(3ꢂ10 mL). The collected organic layers were combined, washed
with brine and concentrated under reduced pressure. The crude
product was submitted to chromatography over silica gel
(Rf¼0.3e0.4, PE/Et2O 9:1) to give the targeted enantio-enriched
dialkynylcarbinol in high yield.
3.1.3. General procedure for the deprotection of silylated
alkynylcarbinols. A solution of the silylated precursor (1 equiv) in
methanol (5 mL) was treated with K2CO3 (3 equiv) under stirring at
rt for 24 h. The mixture was treated with H2O and the aqueous layer
was extracted with Et2O. The combined organic layers were

7926
D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
concentrated under reduced pressure, and the residue was purified
by silica gel chromatography (PE/Et2O 8:2) to give the deprotected
alkynes in high yields.
(PE/Et2O 9:1)¼0.4., 1H NMR (300 MHz, CDCl3):
¼0.19 (s, 9H), 0.88
d
(t, J¼6.9 Hz, 3H), 1.27e1.44 (m, 12H), 1.52 (m, 2H), 2.22 (td, J¼2.1,
6.6 Hz, 2H), 2.37 (d, J¼6.6 Hz, 1H), 5.10 (br s, 1H); 13C {1H} NMR
(75 MHz, CDCl3):
29.8, 32.2, 53.0, 77.6, 86.1, 89.0, 103.0 ppm; IR (neat):
d
¼0.0 (3C), 14.4, 19.0, 23.0, 28.6, 29.2, 29.4, 29.6,
3.1.4. General procedure for the synthesis of 1-naphthyl carbamate
derivatives. 1-Naphtyl isocyanate (1.5 equiv) and DBU (0.1 equiv)
were dissolved in DCM and added to a solution of alkynylcarbinol
(1 equiv) in DCM (0.5 mL). The mixture was stirred overnight, water
was added, and the mixture was extracted with DCM. After stan-
dard treatment of the combined organic layers, the crude product
was purified by chromatography over SiO2 (PE/Et2O 8:2) to give the
1-naphthyl carbamate in relatively high yield.
n
¼3366, 2956,
2925, 2855, 2291, 2232, 2178, 1465, 1408, 1377, 1329, 1296, 1249,
1141, 1030, 961, 840, 759, 721, 700, 669, 617, 599, 580, 573, 560,
555 cmꢀ1; MS (DCI, NH3): m/z (%): 296.2 (90) [MþNH4]þ, 278.1
(100) [MþH]þ; HRMS (DCI-CH4): m/z [MþH]þ calcd for C17H29OSi:
20
277.1988, found: 277.1997. optical rotation [
a]
¼ ꢀ0.54 (c 0.0515,
D
CHCl3). A 93% ee was estimated for (S)-8 from the chiral SFC anal-
ysis of the corresponding 1-naphthyl carbamate 10.
3.1.5. 1-(Trimethylsilyl)heptadeca-1,4-diyn-3-ol (rac)-2. A 1.6 M so-
lution of n-BuLi in hexanes (0.95 mL, 1.52 mmol) was added drop-
wise to a stirred solution of 1-tetradecyne (300 mg, 1.528 mmol) in
THF (10 mL) at ꢀ78 ꢃC. The reaction mixture was stirred for 1 h at
this temperature and then for 30 min at rt, before cooling again at
ꢀ78 ꢃC. Trimethylsilylpropiolaldehyde (211 mg, 1.68 mmol) was
then added and the resulting mixture was stirred overnight. After
treatment with saturated aqueous NH4Cl solution and extractions
with DCM (3ꢂ15 mL), the combined organic layers were washed
with brine, dried over MgSO4 and evaporated to dryness. The crude
residue was purified by silica gel chromatography (Rf¼0.3, PE/Et2O
9:1) to give (rac)-2 as a colorless oil (367 mg, 74%). 1H NMR
3.1.10. (3R)-1-(Trimethylsilyl)tetradeca-1,4-diyn-3-ol (R)-8. Using
(ꢀ)-N-methylephedrine, obtained as a colorless oil (90 mg, 50%). Rf
(PE/Et2O 9:1)¼0.4. 1H and 13C {1H} NMR, IR and MS data are the
20
same as those described for (S)-8. [
a
]
¼ þ0.51 (c 0.0235, CHCl3). A
D
91% ee was estimated for (R)-8 from the chiral SFC analysis of the
corresponding 1-naphthyl carbamate 10.
3.1.11. (3S)-1-(Trimethylsilyl)tricosa-1,4-diyn-3-ol
(S)-9. Using
(þ)-N-methylephedrine (87 mg (60%). Rf (PE/Et2O 9:1)¼0.3. 1H
NMR (300 MHz, CDCl3):
d
¼0.20 (s, 9H), 0.89 (t, J¼6.9 Hz, 3H),
1.26e1.44 (m, 30H),1.52 (m, 2H), 2.22 (td, J¼2.0, 7.2 Hz, 2H), 2.58 (d,
J¼7.2 Hz, 1H), 5.11 (dt, J¼2.0, 7.2 Hz, 1H); 13C {1H} NMR (75 MHz,
(300 MHz, CDCl3):
d
¼0.15 (s, 9H, Si(CH3)3), 0.85 (t, J¼6.9 Hz, 3H),
CDCl3):
d
¼ꢀ0.3 (3C), 14.1, 18.8, 22.7, 28.3, 28.9, 29.2, 29.4, 29.5, 29.6,
1.22e1.39 (m,18H),1.49 (pseudo-quint., J¼7.1 Hz, 2H), 2.18 (td, J¼2.1,
29.7 (8C), 31.9, 52.8, 77.3, 85.9, 88.8, 102.6 ppm; IR (neat):
n¼3324,
7.3 Hz 2H), 2.57 (br s, 1H), 5.07 ppm (br s, 1H); 13C {1H} NMR
2957, 2913, 2849, 2313, 2231, 2176, 1471, 1377, 1286, 1250, 1139,
1109, 1034, 987, 960, 841, 801, 760, 716, 698, 675, 614, 604, 572,
553 cmꢀ1; MS (DCI-NH3): m/z (%): 422.3 (100) [MþNH4]þ, 404.3
(75 MHz, CDCl3):
29.5, 29.6 (2C), 31.8, 52.5, 77.3, 85.5, 88.5, 102.7 ppm; IR (neat):
d
¼ꢀ0.4, 14.0, 18.6, 22.6, 28.2, 28.8, 29.0, 29.3, 29.4,
n
¼3368, 2958, 2933, 2860, 2290, 2232, 2177, 1454, 1410, 1379, 1297,
(40); HRMS (DCI-CH4): m/z [MþH]þ calcd for C26H49OSi: 405.3553,
20
1250, 1142, 1035, 964, 844, 761, 668, 617, 452 cmꢀ1; MS (DCI, NH3):
m/z (%): 338 (100) [MþNH4]þ, 320 (21); HRMS (DCI-CH4): m/z
[MþH]þ calcd for C20H36OSi: 320.2535, found: 320.2520.
found: 405.3563. [
a
]
¼ ꢀ0.23 (c 0.0175 in CHCl3). A 90% ee was
D
estimated for (S)-9 from the chiral SFC analysis of the corre-
sponding 1-naphthyl carbamate 11.
3.1.6. General procedure for the synthesis of the terminal alkynes 5
and 6. To a solution of trimethylsilylacetylene (6.56 g, 0.0668 mol,
4.0 equiv) in THF (100 mL) under stirring at ꢀ78 ꢃC was added
dropwise n-BuLi (27 mL of a 2.5 M solution in hexane, 0.0668 mol,
4.0 equiv). The resulting mixture was stirred for 30 min at ꢀ78 ꢃC
and at 0 ꢃC for 50 min before being transferred through a cannula to
a solution of alkyl bromide (0.0167 mol, 1.0 equiv) in THF (50 mL) at
rt. Freshly distilled HMPA (48 g, 0.267 mol, 16.0 equiv) and TBAI
(0.3 g, 0.835 mmol, 0.05 equiv) were then added and the resulting
brown mixture was stirred at rt for 12 h before being quenched
with 3 N HCl. The aqueous layer was extracted with Et2O and the
recovered organic layer was washed sequentially with saturated
NaHCO3 and brine, dried over MgSO4 and concentrated. The crude
product was used in the next step without further purification.
To a solution of the silylated product (1 equiv) in a THF/MeOH
1:1 mixture (100 mL) at 0 ꢃC was added K2CO3 (3 equiv) in one
portion. The mixture was stirred at rt overnight, then diluted with
a saturated aqueous NH4Cl solution (200 mL) and extracted with
Et2O. The combined organic layers were washed with brine, dried
over Na2SO4 and concentrated under reduced pressure.
3.1.12. (3R)-1-(Trimethylsilyl)tricosa-1,4-diyn-3-ol
(R)-9. Using
(ꢀ)-N-methylephedrine, obtained as a white solid (80 mg, 55%). Mp
36.9e37.8 ꢃC. Yield. Rf (PE/Et2O 9:1)¼0.3. 1H and 13C {1H} NMR, IR
20
and MS data are the same as those described for (S)-9. [
a]
¼ þ0.26
D
(c 0.046 in CHCl3). A 92% ee was estimated for (rac)-2 from the
chiral SFC analysis of the corresponding 1-naphthyl carbamate 11.
3.1.13. 1-(Trimethylsilyl)tetradeca-1,4-diyn-3-yl N-(naphthalen-1-yl)
carbamate 10. It was obtained as a viscous oil (25 mg, 80%) by the
general method for the synthesis of 1-naphthyl carbamate de-
rivatives. Rf¼0.4, PE/Et2O 9:1. 1H NMR (300 MHz, CDCl3):
¼0.21 (s,
d
9H), 0.89 (t, J¼6.6 Hz, 3H), 1.27e1.44 (m, 12H), 1.56 (pseudo-quint.
J¼7.3 Hz, 2H), 2.27 (td, J¼2.1, 7.3 Hz, 2H), 6.20 (t, J¼2.1 Hz, 1H), 7.10
(br,1H), 7.45e7.55 (m, 3H), 7.68 (d, J¼8.1 Hz,1H), 7.85e7.94 (m, 3H);
13C {1H} NMR (75 MHz, CDCl3):
28.9, 29.2, 29.3, 29.5, 31.9, 55.2, 74.4, 87.1, 90.4, 99.1, 120.3, 125.3,
125.8,126.1 (2C),126.3 (2C),128.8,132.1,134.1,152.4 ppm; IR (neat):
d
¼ꢀ0.3 (3C), 14.2, 18.9, 22.7, 28.2,
n
¼3573, 3265, 3054, 2956, 2920, 2851, 2313, 2245, 2114, 1725, 1702,
1630, 1596, 1577, 1535, 1505, 1467, 1347, 1313, 1288, 1275, 1251,
1226, 1170, 1154, 1098, 1063, 1036, 1005, 969, 880, 841, 788, 759,
723, 698, 647, 619, 578, 574, 567, 553 cmꢀ1; HRMS (DCI-CH4): m/z
[MþH]þ calcd for C28H37NO2Si: 447.2594, found: 447.2581. Chiral
3.1.7. Undec-1-yne 5. Purified by distillation at 78e80 ꢃC under
17 mbar (2.0 g, 45%). The NMR spectra were in agreement with
previously reported ones.30
SFC analysis: Chiralpak AD-H 5
mm (4.6ꢂ250 mm), SC CO2þ5%
MeOH, 4 mL/min, 35 ꢃC, 110 bar, UV 220 nm, tR 6.2 min (S) and
7.9 min (R).
3.1.8. Eicos-1-yne 6. Purified by filtration through a pad of silica
eluted with Et2O/pentane 10:1 (2.2 g, 52%). The analytical data were
in agreement with previously reported ones.31
3.1.14. 1-(Trimethylsilyl)tricosa-1,4-diyn-3-yl
carbamate 11. Obtained as an amorphous solid (30 mg, 85%) by the
N-(naphthalen-1-yl)
general method for the synthesis of 1-naphthyl carbamate de-
3.1.9. (3S)-1-(Trimethylsilyl)tetradeca-1,4-diyn-3-ol
(þ)-N-methylephedrine, obtained as a colorless oil (99 mg, 55%). Rf
(S)-8. Using
rivatives. Rf¼0.3, PE/Et2O 9/1. 1H NMR (300 MHz, CDCl3):
¼0.25 (s,
d
9H), 0.90 (t, J¼6.9 Hz, 3H), 1.28e1.44 (m, 30H), 1.58 (pseudo-quint.

D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
7927
J¼7.0 Hz, 2H), 2.28 (td, J¼2.1, 7.0 Hz, 2H), 6.21 (t, J¼2.1 Hz, 1H), 7.05
(br,1H), 7.47e7.58 (m, 3H), 7.69 (d, J¼8.1 Hz,1H), 7.87e7.96 (m, 3H);
well-dried paraformaldehyde (3.09 g, 103 mmol) in THF (50 mL)
was added in one portion. The resulting mixture was stirred over-
night, and then treated with a saturated aqueous solution of NH4Cl
(100 mL). Et2O (100 mL) was added and the separated organic layer
was washed first with brine (2ꢂ100 mL) and then with water
(2ꢂ100 mL). The organic layer was dried over MgSO4, and after
evaporation of the solvent under reduced pressure, the residue was
purified by silica gel chromatography (Rf¼0.3, PE/Et2O 7:3) to give
16 of as a white powder (3.23 g, 70%). The physical data and NMR
spectra are consistent with previously reported data.32
13C {1H} NMR (75 MHz, CDCl3):
d¼ꢀ0.4 (3C), 14.1, 18.8, 22.7, 28.1,
28.8, 29.1, 29.3, 29.5, 29.7 (9C), 31.9, 55.1, 74.3, 87.0, 90.4, 99.0,120.3,
125.2, 125.8, 126.0 (2C), 126.3 (2C), 128.7, 132.0, 134.0, 152.3 ppm; IR
(neat):
n
¼3557, 3267, 3053, 2957, 2915, 2849, 2324, 2249, 2190,
1725,1702,1597,1577,1535, 1502, 1471, 1401,1346, 1313,1289, 1275,
1252, 1226, 1172, 1156, 1099, 1064, 1029, 1006, 908, 879, 843, 786,
760, 716, 700, 659, 654, 640, 628, 571, 560, 520 cmꢀ1; HRMS (DCI-
CH4): m/z [MþH]þ calcd for C37H55NO2Si: 573.4002, found:
573.4019. Chiral SFC analysis: Chiralpak AD-H 5 mm (4.6x250 mm),
SC CO2þ10% MeOH, 4 mL/min, 35 ꢃC, 110 bar, UV 220 nm, tR 5.7 min
(S) and 7.4 min (R).
3.1.21. (Z)-Pentadec-2-en-1-ol 17. A solution of 16 (1 g, 4.46 mmol)
in dry pyridine (10 mL), and Lindlar catalyst (50 mg) was stirred at rt
under a H2 atmosphere for 24 h. The mixture was filtered through
a CeliteÒ pad. The filtrate was concentrated under reduced pressure
and the residue was purified by silica gel chromatography (PE/Et2O
6:4, Rf¼0.5) to afford 17 as a yellow oil (0.90 g, 89%). The physical data
and NMR spectra are consistent with previously reported data.33
3.1.15. (3R)-Tetradeca-1,4-diyn-3-ol (R)-12. White powder (60 mg,
85%). Rf (PE/Et2O 8:2)¼0.4. 1H NMR (300 MHz, CDCl3):
¼0.89 (t,
d
J¼6.9 Hz, 3H),1.29e1.43 (m,12H),1.54 (m, 2H), 2.25 (td, J¼2.1, 7.2 Hz,
2H), 2.56 (d, J¼2.4 Hz, 1H), 5.12 (dd, J¼2.1, 2.4 Hz, 1H); 13C {1H} NMR
(75 MHz, CDCl3):
52.2, 72.1, 76.9, 81.5, 86.2 ppm; IR (neat):
d
¼14.1, 18.6, 22.6, 28.2, 28.8, 29.1, 29.2, 29.4, 31.8,
n
¼3311, 3293, 2923, 2853,
3.1.22. (2Z)-Pentadec-2-enal 18. To a solution of 17 (100 mg,
0.45 mmol) in DCM (30 mL) under stirring at 0 ꢃC was added MnO2
(470 mg, 5.4 mmol). The resulting mixture was stirred for 5e8 h
(until TLC indicated reaction completion) at rt and then filtrated
through a CeliteÒ pad. The solvent was removed under reduced
pressure and the obtained colorless oil was used without further
2290, 2234, 2121, 1464, 1377, 1328, 1298, 1139, 1015, 929, 798, 722,
654, 645, 544, 520 cmꢀ1; HRMS (DCI-CH4): m/z [MþH]þ calcd for
C14H21O: 205.1592, found: 205.1604. [
a]
D
20 ꢀ4.5 (c 0.018, CHCl3).
3.1.16. (3S)-Tetradeca-1,4-diyn-3-ol (S)-12. White powder (70 mg,
80%). Rf (PE/Et2O 8:2)¼0.4. 1H and 13C {1H} NMR, IR and MS data are
purification. 1H NMR (400 MHz, CDCl3):
d
¼0.86 (t, J¼6.8 Hz, 3H),
20
the same as those described for 12-R. [
a]
¼ þ3.17 (c 0.024, CHCl3).
1.24 (m, 18H), 1.49 (quint., J¼7.2 Hz, 2H), 2.54e2.63 (m, 2H), 5.94
(ddt, J¼11.2, 8.2, 1.6 Hz, 1H), 6.61 (dt, J¼11.2, 8.2 Hz, 1H), 10.06 (d,
J¼8.1 Hz, 1H) ppm.
D
3.1.17. (3R)-Tricosa-1,4-diyn-3-ol (R)-13. White powder (110 mg,
75%). Rf (PE/Et2O 8:2)¼0.3. 1H NMR (300 MHz, CDCl3):
¼0.91 (t,
d
J¼6.9 Hz, 3H),1.29e1.44 (m, 30H),1.55 (m, 2H), 2.25 (td, J¼2.1, 7.2 Hz,
2H), 2.35 (d, J¼7.2 Hz, 1H), 2.56 (d, J¼2.3 Hz, 1H), 5.12 (dt, J¼2.3,
3.1.23. Heptadeca-1,4-diyn-3-one 19. To a stirred solution of 20
(106 mg, 0.43 mmol)in DCM (10 mL) at 0 ꢃC was added in one portion
DesseMartin periodinane (275 mg, 0.65 mmol). The resulting mix-
ture was stirred at rt for 3e5 h (until TLC indicated reaction com-
pletion). Then, Et2O (5 mL) and brine (10 mL) were added, and after
separation of the layers, the aqueous one was extracted with Et2O
(3ꢂ5 mL). The combined organic layers were dried with MgSO4 and
after evaporation to dryness, the residue was purified by silica gel
chromatography (Rf¼0.8e0.9, PE/Et2O 10:1) to give 19 as a colorless
7.2 Hz, 1H); 13C {1H} NMR (75 MHz, CDCl3):
d
¼14.1, 18.6, 22.7, 28.2,
28.8, 29.1, 29.3, 29.5, 29.6 (3C), 29.7 (6C), 31.9, 52.1, 72.1, 76.9, 81.5,
86.1 ppm; IR (neat):
n
¼3273, 3183, 2956, 2920, 2847, 2292, 2225,
2120,1461,1426,1406,1370,1293,1138,1017, 932, 794, 725, 703, 660,
638, 609, 522 cmꢀ1; HRMS (DCI-CH4): m/z [MþH]þ calcd for
20
C
23H41O: 333.3157, found: 333.3170. [
a]
¼ ꢀ1.36 (c 0.025, CHCl3).
D
3.1.18. (3S)-Tricosa-1,4-diyn-3-ol (S)-13. White powder (100 mg,
oil (89 mg, 85%). 1H NMR (300 MHz, CDCl3):
d
¼0.86 (t, J¼6.9 Hz, 3H),
80%). Rf (PE/Et2O 8:2)¼0.3. 1H and 13C {1H} NMR, IR and MS data are
1.20e1.41 (m, 18H), 1.59 (pseudo-quint., J¼7.3 Hz, 2H), 2.39 (t,
20
the same as those described for (R)-12. [
a]
¼ þ1.4 (c 0.027, CHCl3).
J¼7.3 Hz, 2H), 3.26 (s, 1H); 13C {1H} NMR (75 MHz, CDCl3):
¼14.0,
d
D
19.1, 22.6, 27.4, 28.8, 28.9, 29.3, 29.4, 29.5, 29.6, 31.9, 77.9, 81.9, 82.2,
3.1.19. (4Z)-Heptadec-4-en-1-yn-3-ol 14. To a solution of the alde-
hyde 18 (100 mg, 0.446 mmol) in dry THF (20 mL) under stirring at
0
96.9, 160.3 ppm; IR (neat):
n
¼3298, 3256, 2923, 2853, 2222, 2097,
1633, 1465, 1422, 1377, 1350, 1325, 1291, 1260, 1208, 1003, 962, 804,
725, 687, 645, 614, 573, 557 cmꢀ1; HRMS (DCI-CH4): m/z [MþH]þ
calcd for C17H27O: 247.2062, found: 247.2052.
ꢃC was added dropwise ethynylmagnesium bromide (1.07 mL,
0.536 mmol). The reaction mixture was stirred for 1 h at 0 ꢃC and 1 h
at rt before treatment with saturated aqueous NH4Cl. The organic
layer was separated, washed with brine, and dried over Na2SO4. The
solvent was evaporated under reduced pressure and the residue was
purified by silica gel chromatography (Rf¼0.3, PE/Et2O 9:1) to afford
3.1.24. 3-Methylheptadeca-1,4-diyn-3-ol 20. It was obtained as
a colorless oil from 24 through the general procedure for the
deprotection of silylated alkynylcarbinols (22 mg, 70%). Rf¼0.3 (PE/
14 as a colorless oil (72 mg, 65%). 1H NMR (300 MHz, CDCl3):
d
¼0.89
Et2O 9:1). 1H NMR (300 MHz, CDCl3):
d¼0.88 (t, J¼6.6 Hz, 3H),
(t, J¼6.9 Hz, 3H), 1.27e1.42 (m, 20H), 1.95 (br s, 1H), 2.15 (pseudo-q,
1.26e1.38 (m, 18H), 1.53 (pseudo-quint., J¼7.2 Hz, 2H), 1.75 (s, 3H),
J¼7 Hz, 2H), 2.51 (d, J¼2.2 Hz, 1H), 5.17 (br s, 1H), 5.60 (m, 2H); 13
C
2.20 (t, J¼7.2 Hz, 2H), 2.53 (s, 1H); 13C {1H} NMR (75 MHz, CDCl3):
{1H} NMR (75 MHz, CDCl3):
29.6 (2C), 29.7 (2C), 31.9, 58.0, 72.9, 84.0,128.6,134.1 ppm; IR (neat):
d
¼14.1, 22.7, 27.6, 29.2, 29.3, 29.4, 29.5,
d
¼14.1, 18.6, 22.7, 28.3, 28.8, 29.1, 29.3, 29.5, 29.6 (3C), 31.9, 32.0,
59.8, 70.1, 81.1, 84.0, 85.5 ppm; IR (neat):
n
¼3394, 3312, 3294, 2992,
n
¼3311, 3022, 2964, 2922, 2852, 2315, 2115, 1655, 1465, 1378, 1304,
2922, 2853, 2247, 2115, 2080, 1725, 1623, 1465, 1368, 1329, 1210,
1140, 1075, 1030, 923, 890, 868, 844, 721, 650, 632, 606, 589, 575,
568, 557, 545 cmꢀ1; HRMS (DCI-CH4): m/z [MþH]þ calcd for
1261, 1126, 1015, 968, 909, 719, 650, 626, 595, 583, 572, 562, 555,
542 cmꢀ1; HRMS (DCI-CH4): m/z [MþH]þ calcd for C17H31O:
251.2375, found: 251.2384.
C18H31O: 263.2375, found: 263.2385.
3.1.20. Pentadec-2-yn-1-ol 16. To a solution of 1-tetradecyne (5 mL,
20.6 mmol) in dry THF (150 mL) under stirring at ꢀ78 ꢃC was added
dropwise n-BuLi (9.1 mL of 2.5 M solution in hexanes, 22.8 mmol).
The reaction mixture was stirred at this temperature for 1 h, and
then 30 min at rt. After cooling again at ꢀ78 ꢃC, a suspension of
3.1.25. Heptadeca-1,4-diyn-3-ol (rac)-2. It was obtained as a white
powder from (rac)-22a using the general procedure for depro-
tection of silylated alkynylcarbinols (300 mg, 75%). Rf¼0.50 (PE/
Et2O 8:2), mp: 47e49 ꢃC. 1H NMR (300 MHz, CDCl3):
d
¼0.88 (t,
J¼6.9 Hz, 3H), 1.20e1.38 (m, 18H), 1.52 (m, 2H), 2.12 (br s, 1H), 2.23

7928
D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
(td, J¼2.1, 7.3 Hz, 2H), 2.54 (d, J¼2.1 Hz, 1H), 5.10 (br s, 1H); 13C {1H}
3-ol 22b (77 mg, 0.190 mmol) in THF (3 mL) at ꢀ78 ꢃC was added
NMR (75 MHz, CDCl3):
d
¼14.1, 18.7, 22.7, 28.2, 28.8, 29.1, 29.3, 29.5,
dropwise 76 mL of n-BuLi (2.5 M in hexanes, 0.190 mmol). The re-
29.6 (3C), 31.9, 52.2, 72.2, 77.2, 81.5, 86.2 ppm; IR (neat):
n
¼3325,
action mixture was stirred at that temperature for 10 min, then
iodomethane (0.12 mL, 1.908 mmol) was added dropwise. The
stirred mixture was allowed warming up to ꢀ30 ꢃC, temperature at
3276, 2955, 2925, 2849, 2290, 2227, 2119, 1497, 1462, 1284, 1020,
932, 793, 710, 662, 604 cmꢀ1; MS (DCI, CH4): m/z (%): 277 (28), 249
(100) [MþH]þ, 247 (65); HRMS (DCI-CH4): m/z [MþH]þ calcd for
which DMSO was added (27 mL, 0.378 mmol), then to rt for 15 h. The
C
17H28O: 249.2218, found: 249.2236.
reaction was quenched by a saturated aqueous NH4Cl solution
(15 mL). The aqueous phase is extracted with Et2O. The combined
organic layers were washed with brine, dried over MgSO4 and
concentrated under reduced pressure. The crude product was pu-
rified by silica gel chromatography (pure pentane, Rf¼0.22) to give
3.1.26. 1-(Trimethylsilyl)heptadeca-1,4-diyn-3-one 23. To a stirred
solution of 50 mg (0.15 mmol) of (rac)-22a in DCM (5 mL) at 0 ꢃC was
added in one portion 67 mg (0.31 mmol) of PCC, then mixture was
warmed to rt and stirred for 8 h, before filtration through a pad of
Celite, and evaporation under reduced pressure. The residue was
purified by silica gel chromatography (Rf¼0.8, PE/Et2O 9:1) to give
25 as a colorless oil (40 mg, 50%). 1H NMR (400 MHz, CDCl3):
d 0.88
(t, J¼7.2 Hz, 3H), 1.04e1.14 (m, 21H), 1.19e1.44 (m, 18H), 1.46e1.57
(m, 2H), 2.22 (td, J¼7.2, 2 Hz, 2H), 3.43 (s, 3H), 4.94 (t, J¼2 Hz, 1H).
23 as colorless (37 mg, 74%). 1H NMR (300 MHz, CDCl3):
d
¼0.24 (s,
13C {1H} NMR (75 MHz, CDCl3):
d
ꢀ11.3 (3C), 14.2, 18.7 (6C), 18.8,
9H), 0.87 (t, J¼6.9 Hz, 3H), 1.24e1.41 (m, 18H), 1.59 (pseudo-quint.,
22.8, 28.5, 28.9, 29.3, 29.5, 29.7, 29.8 (3C), 32.1, 54.2, 60.5, 75.5, 86.4,
86.5, 102.6. IR (neat):
J¼7.2 Hz, 2H), 2.38 (t, J¼7.2 Hz, 2H); 13C {1H} NMR (75 MHz, CDCl3):
n
¼2924, 2863, 2856, 2229, 2171, 1463, 1382,
d
¼ꢀ0.9, 14.1, 19.1, 22.6, 27.4, 28.8, 29.0, 29.3, 29.4, 29.5, 29.6 (2C),
1367, 1314, 1297, 1282, 1260, 1188, 1137, 1080, 1000, 919, 883, 800,
31.9, 82.1, 96.0, 97.7,102.7,160.7 ppm; IR (neat):
n
¼2924, 2854, 2224,
733, 676, 660, 554 cmꢀ1; HRMS-DCI (CH4) m/z [MþH]þ calcd for
2151, 1627, 1465, 1421, 1377, 1325, 1252, 1210, 1163, 1114, 1005, 843,
760, 723, 636, 606, 496 cmꢀ1; HRMS (DCI-CH4): m/z [MþH]þ calcd
for C20H34OSi: 319.2458, found: 319.2448.
C27H50OSi (418.3631): 419.3709, found: 419.3710.
3.1.30. 3-Methoxyheptadeca-1,4-diyne 21. To
a solution of 25
(37 mg, 0.088 mmol) in 3 mL of dry THF at 0 ꢃC was added dropwise
0.26 mL of [n-Bu4N][F] (1 M in THF, 0.265 mmol: addition of TBAF led
to an immediate color change of the solution, from yellow to red-or-
ange). The reaction mixture was stirred at that temperature for 1 h
45 min (TLC monitoring). The reaction was quenched by saturated
aqueous NH4Cl solution (15 mL). The aqueous phase is extracted
with Et2O. The combined organic layers were washed with brine,
dried over MgSO4 and concentrated under reduced pressure. The
residue was purified by silica gel chromatography (eluted by pure
pentane, Rf¼0.18) to give 21 as a colorless oil (19 mg, 83%). 1H NMR
3.1.27. 3-Methyl-1-(trimethylsilyl)heptadeca-1,4-diyn-3-ol
a stirred solution of 40 mg (0.126 mmol) of 23 in 5 mL of dry Et2O at
0 ꢃC was added 41
L (0.126 mmol) of a 3 M solution of MeMgBr in
24. To
m
Et2O. The reaction mixturewas stirred at this temperature for 30 min,
and then 3 h at rt, before treatment with brine (5 mL) and extractions
with Et2O (2ꢂ5 mL). The combined organic layers were dried over
MgSO4, and evaporated under reduced pressure. The residue was
submitted to chromatography over SiO2 (Rf¼0.3, PE/Et2O, 9:1) to give
24 as a colorless oil (39 mg, 93%). 1H NMR (300 MHz, CDCl3):
d¼0.17
(s, 9H), 0.88 (t, J¼7.2 Hz, 3H),1.26e1.36 (m,18H),1.51 (pseudo-quint.,
(300 MHz, CDCl3):
d
0.88 (t, J¼6.8 Hz, 3H), 1.18e1.59 (m, 20H), 2.24
J¼7.0 Hz, 2H), 1.72 (s, 3H), 2.20 (t, J¼7.0 Hz, 2H); 13C {1H} NMR
(td, J¼7.2, 2.1 Hz, 2H), 2.52 (d, J¼2.4 Hz, 1H), 3.43 (s, 3H), 4.93 (q,
(75 MHz, CDCl3):
29.6 (2C), 29.7, 31.9, 32.2, 60.3, 81.5, 83.7, 86.2, 106.6 ppm; IR (neat):
d
¼ꢀ0.24, 14.1, 18.6, 22.7, 28.3, 28.8, 29.1, 29.3, 29.5,
J¼2.1 Hz, 1H). 13C {1H} NMR (75 MHz, CDCl3):
d
ꢀ14.3, 18.8, 22.8,
28.5, 29.0, 29.2, 29.5, 29.7, 29.8 (2C), 29.9, 32.0, 54.6, 59.9, 73.1, 74.7,
n
¼3375, 3311, 3252, 2942, 2922, 2853, 2241, 2115, 2100, 1463, 1365,
79.4, 87.1. IR (neat):
n
¼3311, 2922, 2853, 2231, 2094, 1462, 1377,
1322, 1208, 1135, 1060, 1035, 919, 885, 859, 831, 718, 640, 628, 603,
1260, 1080, 1017, 972, 797, 722, 660, 634, 554 cmꢀ1
.
565, 561, 545 cmꢀ1; HRMS (DCI-CH4): m/z [MþH]þ calcd for
C
21H39OSi: 335.2770, found: 335.2761.
3.1.31. 1-Cyclopropylpentadec-2-yn-1-ol 26. A 2.5 solution of n-BuLi
in hexanes (206 L, 0.515 mmol, 1.1 equiv) was added dropwise to
a stirred solution of 1-tetradecyne (tech., 90%: 140 L, 111 mg,
m
3.1.28. 1-[Tris(propan-2-yl)silane]heptadeca-1,4-diyn-3-ol 22b. To
a solution of tetradec-1-yne (tech., 90%, 0.78 mL, 3.070 mmol) in
50 mL of anhydrous THFat ꢀ78 ꢃC, was added dropwise 1.25 mL of n-
BuLi (2.5 M in hexanes, 3.125 mmol). After completion of addition,
the mixture was stirred 1 h at ꢀ78 ꢃC then 2 h at rt. Then, a solution of
3-[tris(propan-2-yl)silane]propioaldehyde 7b (600 mg, 2.851 mmol)
inTHF (5 mL) was added dropwise at ꢀ78 ꢃC. The mixture was stirred
for 15 h during which time the temperature raised to rt. The reaction
was quenched with a saturated aqueous NH4Cl solution (130 mL).
The phases were separated and the aqueous phase was extracted
with Et2O. The combined organic layers were washed with brine,
dried over Na2SO4 and concentrated under reduced pressure. The
residue was purified by silica gel chromatography (pentane/Et2O
20:1, Rf¼0.23), to give 22b as a colorless oil (802 mg, 64%). 1H NMR
m
0.515 mmol, 1.1 equiv) in THF (5 mL) at ꢀ78 ꢃC. The reaction mix-
ture was stirred at this temperature for 1 h, then another 30 min at
rt. The solution was cooled to ꢀ78 ꢃC and cyclopropylcarbaldehyde
(35 mL, 32.9 mg, 0.469 mmol, 1 equiv) was added dropwise. The
solution was stirred overnight, and then a saturated solution of
NH4Cl (10 mL) was added. The mixture was extracted with ether
(2ꢂ5 mL). The combined organic layers were dried over Na2SO4, the
crude product was submitted to chromatography over SiO2 (Rf¼0.3,
pentane/Et2O¼10:1) to give 26 as a colorless oil that crystallizes
upon standing (89 mg, 72%). 1H NMR (300 MHz, CDCl3):
d
0.35e0.60 (m, 4H), 0.88 (t, J¼6.40 Hz, 3H), 1.13e1.42 (m, 19H),
1.42e1.56 (m, 2H), 1.90 (br s, 1H), 2.19 (td, J¼7.04, 2.05 Hz, 2H), 4.24
(br s, 1H); 13C NMR (75 MHz, CDCl3):
1.3, 3.1, 14.1, 17.3, 18.6, 22.7,
28.6, 28.8, 29.1, 29.3, 29.5, 29.6 (2C), 29.7, 31.9, 65.9, 78.7, 85.9; IR
(neat):
d
(400 MHz, CDCl3):
d
0.88 (t, J¼6.8 Hz, 3H), 1.06e1.10 (m, 21H),
1.19e1.44 (m,18H), 1.45e1.55 (m, 2H), 2.14 (d, J¼7.2 Hz,1H), 2.21 (td,
n
¼3319, 3083, 3006, 2922, 2853, 2254, 2226, 1727, 1465,
J¼7.2, 2 Hz, 2H), 5.09 (dt, J¼7.2, 2 Hz, 1H). 13C {1H} NMR (75 MHz,
1432, 1377, 1328, 1309, 1270, 1207, 1149, 1131, 1024, 1007, 966, 917,
855, 830, 721, 620, 588, 563 cmꢀ1; HRMS-DCI (CH4) m/z [MþH]þ
calcd for C18H33O: 265.2531, found: 265.2540.
CDCl3):
d
ꢀ11.3 (3C), 14.3, 18.7 (6C), 18.8, 22.8, 28.5, 28.9, 29.3, 29.5,
29.7, 29.8 (3C), 32.1, 60.0, 77.8, 85.4, 85.6, 105.0. IR (neat):
n¼3364,
2924, 2856, 2288, 2231, 2177, 1463, 1367, 1295, 1140, 1032, 996, 959,
883, 679, 569 cmꢀ1; HRMS-DCI (CH4) m/z [MꢀH]þ calcd for
3.1.32. (E)-Pentadec-2-en-1-ol 28.27 To a solution of LiAlH4 (26 mg,
0.685 mmol) in THF (20 mL) at 0 ꢃC, was added dropwise a solution
of pentadec-2-yn-1-ol 16 (90 mg, 0.401 mmol) in THF (5 mL). After
stirring for 10 min, the mixture was heated at reflux for 20 h. After
cooling to 0 ꢃC, the reaction was quenched by dropwise addition of
C
26H48OSi (404.3474): 403.3396, found: 403.3393.
3.1.29. (3-Methoxyheptadeca-1,4-diyn-1-yl)tris(propan-2-yl)silane
25. To a solution of 1-[tris(propan-2-yl)silane]heptadeca-1,4-diyn-

D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
7929
1 M HCl (5 mL). The phases were separated and the aqueous phase
was extracted with Et2O. The combining organic phases were dried
over Na2SO4 and concentrated under reduced pressure. The residue
was purified by silica gel column chromatography (pentane/Et2O
5:1, Rf¼0.22) to give 28 (90 mg, 99%) as a white solid. 1H NMR
J¼2.4 Hz, 1H) 4.19 (td, J¼6.4, 2 Hz, 1H). 13C {1H} NMR (75 MHz,
CDCl3):
d
ꢀ8.8, 14.3, 17.7, 22.8, 24.7, 29.5, 29.6 (2C), 29.8 (4C), 32.0,
33.5, 65.4, 73.0. IR (neat):
n
¼3600e3100, 3271, 2916, 2849, 2119,
1499, 1467, 1408, 1287, 1262, 1158, 1094, 1052, 1022, 957, 815, 677,
595, 554 cmꢀ1; HRMS-DCI (CH4) m/z [MþH]þ calcd for C18H32
O
(300 MHz, CDCl3):
d
0.88 (t, J¼6.3 Hz, 3H), 1.18e1.43 (m, 20H), 1.58
(264.2453): 265.2531, found: 265.2521.
(br s, 1H), 2.02 (dt, J¼7.2, 6.6 Hz, 2H), 4.06 (d, J¼4.8 Hz, 2H),
5.53e5.75 (m, 2H). 13C {1H} NMR (75 MHz, CDCl3):
29.3 (2C), 29.5, 29.7, 29.8 (4C), 32.0, 32.4, 64.0, 128.9, 133.8.
d
ꢀ14.3, 22.8,
3.1.37. (R*) or (S*)-1-((1R*,2R*)-2-Dodecylcyclopropyl)prop-2-yn-1-
ol 27b. 1H NMR (400 MHz, CDCl3):
0.34e0.41 (m, 1H),
d
0.56e0.63 (m, 1H), 0.78e0.88 (m, 1H), 0.88 (t, J¼6.8 Hz, 3H),
0.93e1.02 (m, 1H), 1.21e1.44 (m, 22H), 1.78 (d, J¼6.4 Hz, 1H), 2.43
(d, J¼2 Hz, 1H) 4.12 (td, J¼6.4, 2 Hz, 1H). 13C {1H} NMR (75 MHz,
3.1.33. (2-Dodecylcyclopropyl)methanol 29. To a solution of ZnEt2
(1.1 M in toluene, 0.14 mL, 0.154 mmol) in DCM (1.5 mL) at ꢀ10 ꢃ
C
was added dropwise CH2I2 (19
m
L, 0.288 mmol). The solution was
CDCl3):
d
ꢀ10.6, 14.3, 16.0, 22.8, 24.8, 29.5, 29.6 (2C), 29.8 (4C), 32.0,
stirred for 15 min. at ꢀ10 ꢃC, while turning to cloudy colorless. To
33.5, 65.6, 73.0. IR (neat):
n
¼3600e3100, 3275, 2916, 2850, 2120,
this mixture, a solution of 28 (27 mg, 0.12 mmol) in dry DCM (3 mL)
1500, 1467, 1397, 1300, 1262, 1182, 1076, 1008, 951, 803, 672, 584,
was added dropwise, followed by, Ti(OiPr4) (2
mL, 0.006 mmol,
530 cmꢀ1
C18H32O(264.2453): 265.2531, found: 265.2547.
;
HRMS-DCI (CH4) m/z [MþH]þ calcd for
5 mol %). The mixture was stirred for 15 h, while temperature raised
to rt. The reaction was quenched with a saturated aqueous NH4Cl
solution (6 mL). The phases were separated and the aqueous phase
was extracted with Et2O. The combined organic layers were washed
with brine, dried over Na2SO4 and concentrated in vacuo. The
residue was purified by silica gel chromatography (pentane/Et2O
5:1, Rf¼0.17), to give 29 as a viscous white solid (68 mg, 67%). 1H
4. Biological evaluations
4.1. WST tests
HCT116 human colon cancer cells (ATCC) were cultured in
DMEM supplemented with 10% fetal calf serum. For cytotoxicity
evaluation, 3000 cells were seeded per well in 96-well plates,
and 24 h later, were treated with concentrations ranging from
10 nm to 50 mm (eight replicates for each). After 96 h of treat-
ment, cells were incubated with the cell proliferation reagent
WST-1 (Roche) for 3e4 h, and the absorbance was then measured
with a scanning multi-well spectrophotometer. The measured
absorbance directly correlates to the number of viable cells. Data
were analyzed using Excel (Microsoft) and Prism (GraphPad)
software.
NMR (300 MHz, CDCl3):
d 0.24e0.40 (m, 2H), 0.51e0.64 (m, 1H),
0.74e0.94 (m, 4H), 1.12e1.44 (m, 22H), 1.44e1.56 (br s, 1H), 3.42
(dd, J¼11.1, 6.9 Hz, 2H). 13C {1H} NMR (75 MHz, CDCl3):
ꢀ10.1, 14.2,
d
17.3, 21.3, 22.8, 29.5, 29.6, 29.7, 29.8 (5C), 32.0, 33.7, 67.3.
3.1.34. 2-Dodecylcyclopropane-1- carbaldehyde 30. To a solution of
29 (68 mg, 0.284 mmol) in DCM (5 mL) at 0 ꢃC, was added in one
portion
a solid mixture of pyridiniumchlorochromate (PCC:
117.8 mg, 0.535 mmol) and silica (117.7 mg). The mixture was
stirred at 0 ꢃC for 1 h, then at rt for 4 h (TLC monitoring; the orange
heterogeneous mixture turned to a dark brown limpid solution
after stirring for 25 min). The mixture was then filtered through
a small pad of Celite. The filtrate was concentrated in vacuo, then
purified on silica gel (pentane/Et2O 7:1, Rf¼0.62) to give 30 as
4.2. MTT tests
a colorless oil (49 mg, 72%). 1H NMR (400 MHz, CDCl3):
d 0.87 (t,
(MTT¼(3-[4,5-diMethylThiazol-2-yl]-2,5-diphenyl Tetrazolium
bromide). In brief, 10.000 HCT 116 cells were distributed in 96 flat
J¼6.8 Hz, 3H), 0.88e0.95 (m, 1H), 1.17e1.41 (m, 23H), 1.41e1.51 (m,
1H), 1.56e1.64 (m, 1H), 8.97 (d, J¼5.60 Hz, 1H). 13C {1H} NMR
bottom well plates in 100
containing the drug dilution was then added to each well. For each
drug, triplicates of concentrations ranging from 10 M to 5 nM were
mL of DMEM 10% FCS and 1 mL of DMSO
(75 MHz, CDCl3):
29.8 (3C), 30.7, 32.0, 32.8, 201.3. IR (neat):
d
ꢀ14.3, 15.0, 22.8 (2C), 29.2, 29.4, 29.5, 29.7 (2C),
n
¼2922, 2852, 2722,
m
1708, 1465, 1402, 1289, 1168, 1021, 864, 721, 688 cmꢀ1; HRMS-DCI
(CH4) m/z [MꢀH]þ calcd for C16H30O (238.2297): 237.2218, found:
237.2220 (the strongest peak at 255.2315 corresponds to
[MþCH5]þ).
carried out, by means of 7 successive three fold dilutions of a 1 mM
stock solution. Controls always included medium alone, DMSO
alone and dilutions of the reference DAC drug 2 (IC50 around
100 nM). Plates were then placed in a CO2 tissue culture incubator
for 48 or 72 h before the MTT test was performed. This was done by
3.1.35. 1(2-Dodecylcyclopropyl)prop-2-yn-1-ol 27. A 0.5 M solution
of ethynyl magnesium bromide in THF (0.75 mL, 0.377 mmol) was
added dropwise to a solution of 30 (36 mg, 0.151 mmol) in THF
(8 mL) at 0 ꢃC. The mixture was stirred for 1 h at 0 ꢃC, then for 5 h at
rt (TLC monitoring). The reaction was finally quenched by saturated
aqueous NH4Cl solution, and the aqueous phase was extracted with
Et2O. The combining organic phases were washed with brine, dried
over Na2SO4 and concentrated under reduced pressure. The residue
was purified on silica gel (pentane/Et2O 5:1, Rf¼0.33 and 0.27) to
give 27 (26 mg, 65%) as a 50:50 mixture of diastereoisomers 27a
and 27b. The diastereoisomers could not be not assigned to the
threo and erythro configurations, but sequential separation (pen-
tane/Et2O 5:1 and tolueneeethanol 60:1) allowed isolation of 27a
(8 mg) and 27b (7 mg), both as white viscous solids.
adding 10
mL of MTT stock solution (12 mM, 5 mg/mL in PBS, Sigma)
to each well and incubating the plate for 90 min at 37 ꢃC. 100
m
L
isopropanol, 0.1 M HCl were then added to each well, and the plates
were returned to 37 ꢃC for 90 min before reading of the optical
density at 570 nm.
Acknowledgements
D. L. was supported by the French Embassy in Kiev, Ukraine, and
the investigations were performed within the framework of the ‘
Groupement Franco-Ukrainien en Chimie Moleculaire’ (GDRI)
funded by the ‘Centre National de la Recherche Scientifique’ (CNRS).
R. C. is also indebted to the CNRS for half of a teaching sabbatical in
2014e2015. The ‘ Institut de Chimie de Toulouse’ (ICT) and the ‘
ꢀ
ꢀ
ꢀ
3.1.36. (S*) or (R*)-1-((1R*,2R*)-2-Dodecylcyclopropyl)prop-2-yn-1-
Plateforme Integree de Criblage Toulousaine’ (PICT) are acknowl-
ol 27a. 1H NMR (400 MHz, CDCl3):
d
0.30e0.38 (m, 1H),
edged for SFC facilities. The WST cytotoxicity tests were carried out
ꢀ
0.59e0.66 (m, 1H), 0.78e0.88 (m, 1H), 0.88 (t, J¼6.8 Hz, 3H),
pecuniarily at the ‘ Institut des Technologies Avancees en sciences
du Vivant’ (ITAV).
0.94e1.02 (m, 1H), 1.18e1.44 (m, 22H), 1.78 (d, J¼6 Hz, 1H), 2.43 (d,

7930
D. Listunov et al. / Tetrahedron 71 (2015) 7920e7930
14. (a) Frantz, D. E.; Fassler, R.; Carreira, E. M. J. Am. Chem. Soc. 2000, 122,
Supplementary data
1806e1807; (b) Frantz, D. E.; Fassler, R.; Tomooka, C. S.; Carreira, E. M. Acc.
Chem. Res. 2000, 33, 373e381.
15. Kirkham, J. E. D.; Courteny, T. D. L.; Lee, V.; Baldwin, J. E. Tetrahedron 2005, 61,
7219e7232.
16. (a) Moore, D.; Pu, L. Org. Lett. 2002, 4, 1855e1857; (b) Gao, G.; Moore, D.; Xie, R.
G.; Pu, L. Org. Lett. 2002, 4, 4143e4146.
17. Trost, B. M.; Weiss, A. H.; Jacobi von Wangelin, A. J. Am. Chem. Soc. 2006, 128,
Supplementary data (1H and 13C NMR spectra of all newly
described compounds, computational details, and DFT-optimized
structures of CAC, AAC and DAC models.) associated with this
article can be found in the online version, at http://dx.doi.org/
10.1016/j.tet.2015.08.003.
8e9.
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