Rapid access to jaspine B and its enantiomer

Article abstract of DOI:10.1016/j.tet.2013.06.091

A rapid access to jaspine B and its enantiomer ent-jaspine B from a 2,3-aziridino-γ-lactone is reported. This synthesis relies on a one pot regioselective aziridine ring-opening followed by intramolecular cyclization to install the cis-amino-alcohol pattern of jaspine B and on a modified Julia olefination of the lactone followed by a diastereoselective hydrogenation for the introduction of the C14 aliphatic chain. The separation of enantiomers in the course of this synthesis was achieved by supercritical fluid chromatography. The cytotoxicity of both enantiomers was evaluated.

Full text of DOI:10.1016/j.tet.2013.06.091

Tetrahedron 69 (2013) 7227e7233
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Rapid access to jaspine B and its enantiomer
a
a
b
a,
*
ꢀ
ꢀ
Cecile Santos , Isabelle Fabing , Nathalie Saffon , Stephanie Ballereau
,
a,
*
ꢀ
Yves Genisson
LSPCMIB, UMR-5068, CNRS, Universite de Toulouse, UPS, Toulouse, France
a
ꢀ
b
ꢀ
Universite de Toulouse, UPS, Institut de Chimie de Toulouse, FR2599 Toulouse, France
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 24 May 2013
Received in revised form 21 June 2013
Accepted 25 June 2013
Available online 1 July 2013
A rapid access to jaspine B and its enantiomer ent-jaspine B from a 2,3-aziridino-g-lactone is reported.
This synthesis relies on a one pot regioselective aziridine ring-opening followed by intramolecular
cyclization to install the cis-aminoealcohol pattern of jaspine B and on a modified Julia olefination of the
lactone followed by a diastereoselective hydrogenation for the introduction of the C14 aliphatic chain.
The separation of enantiomers in the course of this synthesis was achieved by supercritical fluid chro-
matography. The cytotoxicity of both enantiomers was evaluated.
Keywords:
Jaspine B
Ó 2013 Elsevier Ltd. All rights reserved.
Pachastrissamine
Sphingosine
Aziridine
Lactone
1. Introduction
displays a strong dose- and time-dependent cytotoxicity towards
melanoma cells (murine B16 and human SK-Me128).3 However, de-
Jaspine B (also named Pachastrissamine) (Fig. 1) is a naturally
occurring anhydrophytosphingosine, which was first isolated in 2002
from the Okinawan marine sponge, Pachastrissa sp.1 One year later
spite a significant interest in the molecular mechanism of cell death
induced by jaspine B,3,4 this likely complex and multi-target mode of
action has not been characterized fully. Recently, Kim et al. also
highlight the potential use of jaspine B as a therapeutic agent against
hyperproliferative diseases, such as melanoma.5
Due to this remarkable biological activity and its relatively
simple structural features, jaspine B has stimulated considerable
interest of the synthetic community.6,7 To go deeper in the un-
derstanding of the structureeactivity relationships of this natural
compound, many analogues were synthesized8 as well as di-
astereoisomers of jaspine B.4a,b,6a,7fej,8a,9 The enantiomer ent-jas-
pine B was not the deal of such an effort from the synthetic point
of view4b,7k,9a,10 and study of its biological activity remains
limited.4b,9a
Debitus et al.2 also extracted this natural
D-ribo-phytosphingosine
derivative from the sponge Jaspis sp. collected in Vanuatu. This nat-
ural jaspine B was reported to exhibit submicromolar cytotoxicity
against various cell lines.1,2 We found in particular that jaspine B
In this paper, we wish to report a rapid synthetic access to jas-
pine B and its enantiomer and the evaluation of their cytotoxic
activity.
2. Results and discussion
2.1. Synthetic approach
Fig. 1. Structure of D-ribo-phytosphingosine, jaspine B and its enantiomer.
Recently, we described the synthesis of phytosphingosine and
jaspine B analogues containing an aziridine ring.8e These syntheses
were based on an aziridino-g-lactone as a common precursor
* Corresponding authors. Tel.: þ33 (0)5 6155 62 99; fax: þ33 (0)56155 6011; e-mail
addresses: ballereau@chimie.ups-tlse.fr (S. Ballereau), genisson@chimie.ups-tlse.fr
ꢀ
(Y. Genisson).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.06.091

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C. Santos et al. / Tetrahedron 69 (2013) 7227e7233
(Scheme 1). We envisioned that this versatile intermediate was
ideally suited to assemble the jaspine B all-cis tetrahydrofuran
framework according to the following retrosynthetic scheme
(Scheme 1).
Scheme 1. Retrosynthetic approach to jaspine B.
Scheme 3. Proposed mechanism for the oxazolidin-2-one formation.
The two main features of this approach are: (1) the construction
of the cis-aminoealcohol pattern through a one pot regioselective
aziridine ring-opening followed by intramolecular cyclization and
(2) the introduction of the C14 aliphatic chain through a modified
Julia olefination of the lactone followed by a diastereoselective
hydrogenation.
The next step en route to the jaspine B tetrahydrofuran core
assembly was the introduction of the C14 alkyl chain. According to
our synthetic plan, an olefination of the carbonyl function of the
lactone was accomplished by a Julia modified reaction15 using the
methodology recently described by Gueyrard and coll. for the
synthesis of exo-glycal.16 The reaction of the lactone 3 and 2-(tet-
radecylsulfonyl)benzo[d]thiazole17 (Scheme 4) followed by a treat-
ment with DBU afforded the enol ether 6 as an irrelevant 2:1
mixture of E/Z isomers18 and in a 49% yield. As appeared in the
literature during the course of this work,19 we observed that the
enol ether formed was very sensitive to hydration and we could not
completely avoid formation of the hemiketal 7 (23% yield after
chromatography). Use of boron trifluoride etherate as described by
Gueyrard, Goekjian and coll.20 did not improve the conversion. On
the other hand, purification on basic alumina instead of silica gel,
allowed us to slightly increase the isolated yield in alkenes 6 to 55%.
2.2. Synthesis
2.2.1. Racemic route. Aziridino-g-lactones are very useful in-
termediates11 that have been used in the preparation of several
amino-acids derivatives.12
The 2,3-aziridino-g-lactones bearing an alkyl group on the ni-
trogen (Scheme 1, R¼alkyl) can be regarded as non-activated azir-
idine-2-carboxylates. The reactivity of non-activated 2-substituted
aziridines towards ring opening reaction has recently been
reviewed.13 Lee, Ha and coll. showed that the reaction of aziridines
bearing an electron withdrawing group at C-2 with methyl chlor-
oformate give oxazolidin-2-ones in a one pot process.14 We applied
this pathway to 2,3-aziridino-g-lactone 1 (Scheme 2) so as to in-
troduce the cis-aminoealcohol moiety present on the tetrahydro-
furan ring of the jaspine B.
Scheme 2. Synthesis of lactone oxazolidinone 3. Reagents and conditions: (a)
ClCO2CH3, CH3CN, reflux, 12 h, 74%; or (b) ClCO2CH3, CH3CN, sealed tube, MW, 160 W,
100 ꢀC, 2 h, 79%.
The racemic 2,3-aziridino-g-lactone 1 was obtained in two
steps from
D
-erythronolactone (2).8e Under the conditions de-
Scheme 4. Synthesis of racemic protected jaspine B. Reagents and conditions: (a) (1)
2-(tetradecylsulfonyl)benzo[d]thiazole, LiHMDS, THF, ꢁ78 ꢀC, 30 min; (2) DBU, THF, rt,
2 h, 55% in 6 and 8% in 7; (b) H2, (Ph3P)3RhCl, C6H6/EtOH, 2 h, 78%.
scribed by Lee, Ha and coll.14 the aziridine ring was converted to
the oxazolidin-2-one 3.
According the mechanism reported,14 this transformation, ini-
tiated by a N-methoxycarbonylation, provides an activated azir-
idinium 4 that undergoes a regioselective C2eN bond cleavage by
the nucleophilic chloride ion. The intramolecular cyclization of the
resulting intermediate chlorocarbamate 5 gives the oxazolidin-2-
one with a global retention of configuration at C-2 as a result of
a double SN2 inversion process (Scheme 3).
Hydrogenation of the olefin in compound 6 employing homo-
geneous catalyst (Ph3P)3RhCl7c furnished the fully protected race-
mic jaspine B (8) as a single diastereoisomer and in a 78% yield. The
use of heterogeneous Pd/C catalyst (up to 50 mol %) did not give any
hydrogenation product but only hydration product 7.
We were satisfied to observe that, despite the presence of the
sensitive lactone,12a the yield was only slightly lower than those
described by Lee, Ha and coll. In order to further improve the effi-
ciency of this transformation, the reaction time was reduced by the
use of microwave irradiation. Under these conditions, only 2 h were
necessary to bring the reaction to completion with a 79% yield.
The intermediate 8, in its enantiomeric pure form, has already
been used by our group in the synthesis of jaspine B.8d Following
the protocol described, two deprotection steps, that is oxidative
elimination of the PMB-group followed by the hydrolysis of the
oxazolidinone ring, allowed us to obtain the racemic jaspine B in
a 60% yield (Scheme 5).

C. Santos et al. / Tetrahedron 69 (2013) 7227e7233
7229
Scheme 5. Synthesis of racemic jaspine B. Reagents and conditions: (a) CAN, MeCN/
H2O, 2 h, 71%; (b) KOH, EtOH/H2O, 85 ꢀC, 12 h, 85%.
This six-step synthetic route validated in the racemic form, we
were interested in its application to the synthesis of enantiomeri-
cally pure jaspine B and its enantiomer.
2.2.2. Chiral auxiliary route. The first option was to start the syn-
thesis with an optically active aziridine. In this aim, we reproduced
the two-step synthesis of 2,3-aziridino-
g-lactone starting from
D-erythronolactone (2) via the triflate derivative 10 with the
Fig. 2. Molecular view of the aziridino-
g
-lactone 11a in the solid state (thermal el-
(R)-(þ)-
a
-methylbenzylamine. A mixture of two diastereoisomeric
-lactone 11a and 11b was obtained in a 21% yield over
lipsoids at 50% probability); hydrogen atoms are omitted for clarity excepted on
asymmetric carbons.
aziridino-
g
the two steps (Scheme 6).
Scheme 7. Synthesis of optically active lactone oxazolidinones. Reagents and condi-
tions: (a) ClCO2CH3, CH3CN, sealed tube, MW, 160 W, 100 ꢀC, 2.5 h, 50%.
Scheme 6. Synthesis of optically active 2,3-aziridino-g-lactones. Reagents and condi-
tions: (a) Tf2O, pyridine, CH2Cl2, ꢁ78 ꢀC to ꢁ30 ꢀC, 3.5 h; (b) (R)-(þ)-
a-methyl-
benzylamine, DMF, ꢁ30 ꢀC, 12 h, 21% over two steps.
g
-lactones have a much lower reactivity towards nucleophilic
aziridine ring opening than the N-benzyl-2-acyl-aziridines.12a This
lack of reactivity was thus not only attributed to the poor electron-
withdrawing character of the benzyl group but also to the com-
petitive electrophilic behaviour of the lactone ring.
Due to the lower reactivity of a-methylbenzylamine compared
to methoxy-substituted benzylamines in the tandem Michael-type
addition/cyclization leading to the aziridine,12a the reaction time at
ꢁ30 ꢀC necessary for the completion was much longer and the
competitive opening of the lactone ring by the amine may explain
the somewhat moderate yield.12b This aziridination reaction was
The two diastereoisomers 12a and 12b were crystallized and
X-ray analysis allowed their structural assignment (Figs. 3 and 4).
The yield obtained in the two first steps of this synthesis using
(R)-(þ)-
a-methylbenzylamine as chiral auxiliary, much lower
also conducted with enantiomerically pure (R)-p-methoxy-
methylbenzylamine. The use of this chiral auxiliary did not improve
the yield of the reaction. The two (R)-p-methoxy- -methylbenzyl
a-
than in the p-methoxybenzyl racemic series, associated with fas-
tidious chromatographies required for the separation of the di-
astereoisomers led us to consider another option for the synthesis
of enantiomerically pure jaspine B and its enantiomer. We de-
veloped a separation method of both enantiomers of the racemic
protected jaspine B 8.
a
substituted aziridines were isolated and characterized including by
X-ray diffraction crystallography (see Supplementary data).
Even after several thorough chromatographies on silica gel only
milligramme-scale samples of each diastereoisomer 11a and 11b
could be isolated. Nevertheless, X-ray crystallography analysis of
compound 11a allowed its unambiguous structural assignment
(Fig. 2).
The mixture of diastereoisomers 11 was treated with methyl
chloroformate in acetonitrile under MW irradiation to give the two
diastereoisomeric oxazolidinones 12a and 12b that were separated
by chromatography on silica gel (Scheme 7). The yield (25% for each
diastereoisomer) was lower than in the p-methoxybenzyl racemic
series.
This moderate yield with
may deserve comments. Indeed, Lee, Ha and coll. described
transformation of -methylbenzyl]aziridines-2-
N-[(R)-(þ)-
carboxylates to 5-functionalized oxazolidin-2-ones in almost
quantitative yield.14 Thus, the presence of the
-methylbenzyl
a-methylbenzyl substituted aziridine
a
a
group instead of the p-methoxybenzyl does not by itself explain
the lowering of the yield. Nevertheless, this trend could be ex-
pected since it has already be shown that N-benzyl-2,3-aziridino-
Fig. 3. Molecular view of compound 12a in the solid state (thermal ellipsoids at 50%
probability); hydrogen are omitted for clarity excepted on asymmetric carbons.

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C. Santos et al. / Tetrahedron 69 (2013) 7227e7233
Scheme 8. Synthesis of jaspine B and ent-jaspine B. Reagents and conditions: (a) CAN,
MeCN/H2O, 2 h; (b) KOH, EtOH/H2O, 85 ꢀC, 12 h, 60% over two steps.
Fig. 4. Molecular view of compound 12b in the solid state (thermal ellipsoids at 50%
probability); hydrogen atoms are omitted for clarity excepted on asymmetric carbons.
biological evaluation of ent-jaspine B: Rao and coll. evaluated its
cytotoxicity9a while Fujii, Oishi and coll. assessed its inhibitory
potency against sphingosine kinases.4b In these two studies, the
results obtained with ent-jaspine B proved to be very close to that of
the natural enantiomer. On the other hand, Casas and Delgado and
coll.4a showed that inversion of C-2 and/or C-3 stereocenters pro-
vides significantly less toxic compounds.
In order to go further in the understanding of the influence of
the absolute configuration on the cytotoxic activity, the cytotoxicity
of jaspine B and ent-jaspine B was examined on GM637 (normal
fibroblast), HTC116 (human colon carcinoma) and U2OS (human
osteosarcoma) cells. The IC50 of the compounds are reported in
Table 1.
2.2.3. Enantiomers separation. The resolution of enantiomers by
supercritical fluid chromatography (SFC) is a flourishing technol-
ogy. The environmental and practical benefits of SFC (e.g., less
solvent used, higher resolution, shorter separation times,.) are
already well-known.21 It is even sometimes considered that it is
more ‘time efficient’ to synthesize racemic mixtures and then
chromatographically separate the enantiomers than to develop
asymmetric syntheses of the drug candidates of interest.22 An
overview of SFC applications for chiral separations covering the
literature from 2000 has recently been published.23
In our case, the best resolution was achieved by semi-
preparative SFC on a Chiralpak IC column (5
mm silica particles
immobilized with cellulose tris-(3,5-dichlorophenylcarbamate))
with 25% of a CH2Cl2/MeOH mixture (80:20, v/v) as an additive in
a CO2 mobile phase (Fig. 5). This separation could be run on more
than 100 mg and both enantiomers were obtained in high effi-
ciency and purity (80% global yield).
Table 1
Cytotoxicity of jaspine B and ent-jaspine B
Compound
IC50 (mM)
GM637
HTC116
U2OS
Jaspine B
ent-Jaspine B
0.4
6
0.7
5
0.17
4
In all cell lines, the natural compound, with IC50 values in sub-
micromolar range, proved to be significantly more cytotoxic than
its enantiomer. These results indicate that the absolute configura-
tion of the tetrahydrofuran jaspine B is indeed determinant for the
biological activity of this natural compound. Nevertheless, it is
noteworthy that the cytotoxicities obtained for the unnatural
compound are in the micromolar range. These values thus justify
the study of the enantiomer of jaspine B itself for further target
identification and structural optimization.
3. Conclusions
In summary, we have developed a rapid synthesis of jaspine B
and ent-jaspine B involving six synthetic steps from commercially
Fig. 5. Separation of the enantiomers of (ꢂ)-8 by SFC.
available
critical fluid chromatography (SFC). This synthesis illustrated well
the versatility of 2,3-aziridino- -lactone intermediates, alterna-
D-erythronic g-lactone and a chiral separation by super-
Each enantiomer of protected jaspine B ((þ)-8 and (ꢁ)-8) was
submitted to the same two steps deprotection protocol leading to
jaspine B and its enantiomer ent-jaspine B in 60% yield (Scheme 8).
Enantiomerically pure jaspine B and its enantiomer were thus
g
tively taking advantage of its different reactivities: first, that of the
aziridine ring to install the cis-aminoealcohol moiety through
a one pot regioselective ring-opening followed by intramolecular
cyclization and, second, the reactivity of the lactone to introduce
the aliphatic chain by a Julia modified olefination followed by
a diastereoselective hydrogenation. Thanks to an efficient enan-
tiomeric resolution by a chiral SFC, this route was easily amenable
to the preparation of natural jaspine B and its enantiomer. Bi-
ological evaluation of the synthesized compounds confirmed the
influence of the absolute configuration of the natural product on its
synthetized in six steps from commercially available
ronolactone in 7% overall yield.
D-eryth-
2.3. Biological evaluation
Despite the synthetic efforts dedicated to the synthesis of vari-
ous diastereoisomers of jaspine B, only two groups reported

C. Santos et al. / Tetrahedron 69 (2013) 7227e7233
7231
cytotoxicity. Yet the cytotoxicity retained by the ent-jaspine B (in
the micromolar range) justifies the interest of a synthetic access to
both enantiomers.
was closed using a PTFE-silicon septum (vial and septum available
from CEM Corporation). Then the reaction mixture was submitted
in a sealed tube to microwave irradiation (CEM DiscoverÔ reactor,
160 W, 100 ꢀC) for 2 h. After cooling, the reaction mixture was
concentrated to dryness. The resulting residue was purified by flash
chromatography on silica gel (EtOAc/CH2Cl2 1:9) to give the oxa-
zolidinone 3 (451 mg, 79%) as a white amorphous solid.
4. Experimental part
4.1. General methods
The following solvents and reagents were dried prior to use:
CH2Cl2, MeOH (from calcium hydride), Et2O, petroleum ether, THF
(freshly distilled from sodium/benzophenone). Analytical thin layer
chromatography (TLC) was performed using Merck silica gel 60F254
precoated plates. Chromatograms were observed under UV light
and/or were visualized by heating plates that were dipped in 10%
phosphomolybdic acid in ethanol. Column chromatographies were
4.2.2. (3aS*,6aS*,E)-3-(4-Methoxybenzyl)-6-tetradecylidenetetrahydro-
furo[3,4-d]oxazol-2(3H)-one (E-6) and (3aS*,6aS*,Z)-3-(4-
methoxybenzyl)-6-tetradecylidenetetrahydrofuro[3,4-d]oxazol-2(3H)-
one (Z-6). To a solution of lactone 3 (75 mg, 0.29 mmol) and 2-
(tetradecylsulfonyl)benzo[d]thiazole (135 mg, 0.34 mmol) in an-
hydrous THF (2 mL) under nitrogen at ꢁ78 ꢀC was added dropwise
a solution of LiHMDS (1.0 M in THF, 570
mL, 0.57 mmol) over
carried out with SDS 35e70
m
m flash silica gel. NMR spectroscopic
10 min. The reaction mixture was stirred at that temperature for
30 min and quenched by addition of water. After hydrolysis, the
mixture was extracted with EtOAc (3ꢃ10 mL). The combined or-
ganic extracts were dried over magnesium sulfate and concen-
trated to dryness. The residue was dissolved in anhydrous THF
data were obtained with Bruker Advance 300. Chemical shifts are
quoted in parts per million (ppm) relative to residual solvent peak. J
values are given in hertz. Assignments of chemical shifts are de-
scribed according to the numbering drawn on Scheme 2 for lac-
tones and on Scheme 4 for all other compounds. Mass spectrometry
(MS) data were obtained on a ThermoQuest TSQ 7000 spectrome-
ter, high-resolution mass spectra (HRMS) were performed on
a ThermoFinnigan MAT 95 XL. Optical rotations were measured
(6 mL) and DBU (98 mL, 0.57 mmol) was added. After 2 h stirring,
the reaction mixture was concentrated to dryness and the result-
ing residue was purified by flash chromatography on basic alumina
(EtOAc/CH2Cl2/petroleum ether 6:24:70) to give the compound 6
(70 mg, 55%) as a 2:1 mixture of E and Z isomers. An aliquot of this
mixture was purified by preparative TLC (EtOAc/CH2Cl2/petroleum
ether 4:1:5) to characterize the two isomers.
on
a
Jasco P-2000 polarimeter.
[
a]
values are given in
D
deg dmꢁ1 cm3 gꢁ1
.
For crystallographic analysis, the selected crystals were moun-
ted on a glass fibre using perfluoropolyether oil and cooled rapidly
in a stream of cold N2. Crystallographic data of the structures for
compounds 11a, 12a and 12b were collected on a Bruker-AXS
Quazar APEX II diffractometer using a 30 W air-cooled microfocus
(E)-6: 1H NMR (CDCl3, 300 MHz)
d (ppm): 7.25e7.15 (m, 2H, Har);
6.95e6.85 (m, 2H, Har); 5.32 (dd, 1H, 3-H, J3-2¼7.9, J3-5¼1.1); 5.13
(td, 1H, 5-H, J5-6¼8.1, J5-3¼1.1); 4.67 (d, 1H, CH2N, J¼15.0); 4.18 (d,
1H, CH2N, J¼14.9); 4.16 (ddd, 1H, 2-H, J2-3¼7.9, J2-1a¼4.4, J2-1b¼1.4);
4.01 (dd, 1H, 1b-H, J1b-1a¼10.2, J1b-2¼1.5); 3.80 (s, 3H, OMe); 3.71
(dd, 1H, 1a-H, J1b-1a¼10.2, J1a-2¼4.7); 2.20e1.90 (m, 2H, 6-H);
1.40e1.15 (m, 22H, 7-H to 17-H), 0.98e0.84 (3H, m, 18-H). 13C NMR
source (ImS) with focussing multilayer optics at a temperature of
ꢁ
193(2) K, with Mo K
a
radiation (wavelength¼0.71073 A) by using
phi- and omega-scans. The data were integrated with SAINT, and an
empirical absorption correction with SADABS was applied.24 The
structures were solved by direct methods, using SHELXS-97,25 and
refined using the least-squares method on F2.25 All non-H atoms
were treated anisotropically. Crystallographic data (excluding
structure factors) have been deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication no. CCDC-
935731 (11a), CCDC-935732 (12a) and CCDC-935733 (12b). These
data can be obtained free of charge via www.ccdc.cam.uk/conts/
retrieving.html (or from the CCDC, 12 Union Road, Cambridge CB2
1EZ, UK; fax: (þ44) 1223 336 033; or deposit@ccdc.cam.ac.uk).
(CDCl3, 75 MHz)
d (ppm): 159.6 (CeOMe); 157.2 (C]O); 152.0 (C-
4); 129.6 (Car); 127.1 (Cqar); 114.4 (Car); 106.8 (C-5); 73.2 (C-3); 70.6
(C-1); 58.2 (C-2); 55.3 (OMe); 46.6 (CH2N); 32.0, 30.2, 29.7 (4C),
29.6, 29.5, 29.4, 29.2, 26.7, 22.7 (C-6 to C-17); 14.2 (C-18). MS (CI/
NH3): m/z¼461 ([MþNH4]þ). HRMS m/z: calcd for C27H42NO4
[MþH]þ: 444.3114; found: 444.3125.
(Z)-6: 1H NMR (CDCl3, 300 MHz)
d (ppm): 7.25e7.15 (m, 2H, Har);
6.95e6.85 (m, 2H, Har); 5.12 (d, 1H, 3-H, J3-2¼7.9); 4.80 (t, 1H, 5-H,
J5-6¼7.4); 4.68 (d, 1H, CH2N, J¼15.0); 4.16 (d, 1H, CH2N, J¼14.9); 4.14
(ddd, 1H, 2-H, J2-3¼7.7, J2-1a¼4.9, J2-1b¼1.6); 4.08 (dd, 1H, 1b-H, J1b-
¼10.2, J1b-2¼1.6); 3.81 (s, 3H, OMe); 3.80 (dd,1H,1a-H, J1b-1a¼10.1,
1a
4.2. Synthesis
J1a-2¼4.8); 2.08 (q, 2H, 6-H, J¼7.2); 1.40e1.15 (m, 22H, 7-H to 17-H),
0.98e0.84 (3H, m, 18-H). 13C NMR (CDCl3, 125 MHz)
d (ppm): 159.6
4.2.1. (3aS*,6aS*)-3-(4-Methoxybenzyl)dihydrofuro[3,4-d]oxazole-
2,6(3H,6aH)-dione (3). Method A: To a solution of 1 (285 mg,
1.30 mmol) in CH3CN (5 mL) was added methyl chloroformate
(CeOMe); 157.2 (C]O); 151.7 (C-4); 129.7 (Car); 127.1 (Cqar); 114.4
(Car); 107.0 (C-5); 75.7 (C-3); 71.3 (C-1); 57.8 (C-2); 55.3 (OMe); 46.5
(CH2N); 32.0, 29.7 (4C), 29.6, 29.5, 29.4 (2C), 29.3, 25.4, 22.7 (C-6 to
C-17); 14.2 (C-18). MS (CI/NH3): m/z¼461 ([MþNH4]þ). HRMS m/z:
calcd for C27H42NO4 [MþH]þ: 444.3114; found: 444.3136.
Compound 7 (10 mg, 8%) resulting from the hydration of the
exo-double bond was also isolated.
(151 mL, 1.95 mmol) and the mixture was refluxed for 12 h. After
cooling to rt, the mixture concentrated to dryness. The resulting
residue was purified by flash chromatography on silica gel (EtOAc/
CH2Cl2 1:9) to give the oxazolidinone 3 (253 mg, 74%) as a white
amorphous solid. 1H NMR (CDCl3, 300 MHz)
d
(ppm): 7.25e7.15 (m,
7: 1H NMR (CDCl3, 300 MHz)
d (ppm): 7.25e7.15 (m, 2H, Har);
2H, Har); 7.00e6.90 (m, 2H, Har); 4.95 (d, 1H, 2-H, J2-3¼7.9); 4.67 (d,
1H, CH2N, J¼15.0); 4.35 (ddd, 1H, 3-H, J3-2¼7.9, J3-4a¼4.1, J3-4b¼1.5);
4.30 (AB of an ABX, 2H, 4a-H and 4b-H, J4a-4b¼10.8, J4a-3¼4.1, J4b-
6.90e6.80 (m, 2H, Har); 4.68 (d, 1H, CH2N, J¼15.0); 4.59 (d, 1H, 3-H,
J3-2¼7.5); 4.14 (ddd, 1H, 2-H, J2-3¼7.5, J2-1a¼3.4, J2-1b¼1.6); 4.08 (d,
1H, CH2N, J¼15.0); 3.90e3.80 (m, 2H, H-1); 3.79 (s, 3H, OMe);
2.70e2.20 (br s,1H, OH); 1.96e1.82 (m, 1H, 5a-H); 1.81e1.68 (m, 1H,
5b-H); 1.55e1.40 (m, 2H, 6-H); 1.35e1.15 (m, 22H, 7-H to 17-H);
¼1.5); 4.29 (d, 1H, CH2N, J¼14.9); 3.81 (s, 3H, OMe). 13C NMR
3
(CDCl3, 75 MHz)
d (ppm): 170.4 (C-1); 159.9 (CeOMe); 155.9
(C]O); 129.8 (Car); 126.0 (Cqar); 114.7 (Car); 69.8 (C-2); 68.5 (C-4);
55.4 (C-3); 55.2 (OMe); 46.8 (CH2N). HRMS m/z: calcd for
0.92e0.82 (3H, m, 18-H). 13C NMR (CDCl3, 75 MHz)
d (ppm): 159.6
(CeOMe); 157.0 (C]O); 129.6 (Car); 127.2 (Cqar); 114.4 (Car); 107.4
(C-4); 80.6 (C-3); 67.6 (C-1); 59.0 (C-2); 55.3 (OMe); 46.3 (CH2N);
34.9 (C-5); 31.9, 29.8, 29.7 (5C), 29.6 (2C), 29.4, 23.3, 22.7 (C-6 to C-
17); 14.2 (C-18). MS (CI/NH3): m/z¼479 ([MþNH4]þ). HRMS m/z:
calcd for C27H44NO5 [MþH]þ: 462.3219; found: 462.3227.
C
13H14NO5 [MþH]þ: 264.0872; found: 264.0863.
Method B: To a solution of 1 (472 mg, 2.16 mmol) in CH3CN
(7 mL) in a 10 mL glass pressure vial equipped with a stir bar was
added methyl chloroformate (250 L, 3.23 mmol). The pressure vial
m

7232
C. Santos et al. / Tetrahedron 69 (2013) 7227e7233
4.2.3. (3aS*,6S*,6aS*)-3-(4-Methoxybenzyl)-6-tetradecyltetrahydro-
furo[3,4-d]oxazol-2(3H)-one (8). A solution of compound 6 (89 mg,
0.20 mmol) (as a Z/E mixture) and (PPh3)3RhCl (37 mg, 0.04 mmol)
in benzene/EtOH (4 mL, 1:1) was stirred at 40 ꢀC for 14 h under H2
atmosphere. After concentration to dryness, the residue was puri-
fied by flash chromatography on silica gel (EtOAc/CH2Cl2/petro-
leum ether 6:24:70 to 10:40:50) to give the compound 8 (70 mg,
78%). All analyses were in agreement with the data reported in the
literature.8d
(C-2); 23.4 (CH3CH). [
a
]
20 ꢁ19.6 (c 0.5, CHCl3). HRMS m/z: calcd for
D
C
12H14NO2 [MþH]þ: 204.1025; found: 204.1028.
11b: 1H NMR (CDCl3, 300 MHz)
d (ppm): 7.4e7.2 (m, 5H, Har);
4.41 (d, 1H, 4a-H, J4a-4b¼9.9); 4.26 (dd, 1H, 4b-H, J4b-4a¼9.9, J4b-
¼3.0); 2.99 (dd, 1H, 3-H, J3-2¼4.5, J3-4b¼3.0); 2.73 (q, 1H, CH3CHN,
3
J¼6.5); 2.55 (d, 1H, 2-H, J2-3¼4.5), 1.48 (d, 3H, CH3CHN, J¼6.5). 13
C
NMR (CDCl3, 75 MHz) d (ppm): 172.2 (C-1); 142.5 (Cqar); 128.6 (Car);
127.6 (Car); 126.3 (Car); 69.4 (C-4); 66.9 (CH3CH); 42.6 (C-3); 39.0
(C-2); 23.5 (CH3CH). [
C
a
]
20 ꢁ23.6 (c 0.4, CHCl3). HRMS m/z: calcd for
D
12H14NO2 [MþH]þ: 204.1025; found: 204.1033.
4.2.4. (3aS*,6S*,6aS*)-6-Ethyltetrahydrofuro[3,4-d]oxazol-2(3H)-one
4.2.7. (3aR,6aR)-3-((R)-1-Phenylethyl)dihydrofuro[3,4-d]oxazole-
2,6(3H,6aH)-dione (12a) and (3aS,6aS)-3-((R)-1-phenylethyl)dihy-
drofuro[3,4-d]oxazole-2,6(3H,6aH)-dione (12b). The protocol used
for the synthesis of 3 (method B) was applied to the mixture of
aziridine lactones 11a and 11b (178 mg, 0.874 mmol) and methyl
(9). To
a solution of PMB-protected compound 8 (70 mg,
0.157 mmol) in CH3CN/H2O (9:1) (10 mL) was added CAN (517 mg,
0.94 mmol). The mixture was stirred at rt for 12 h, then diluted with
water and extracted three times with CH2Cl2. The combined or-
ganic layers were washed with a saturated aqueous NaHCO3 solu-
tion and with brine, dried over MgSO4 and concentrated to dryness.
The residue was purified by flash chromatography on silica gel
(EtOAc/CH2Cl2 4:6) to give the compound 9 (37 mg, 72%). All
analyses were in agreement with the data reported in the
literature.8d
chloroformate (104 mL, 1.31 mmol) in CH3CN (3 mL) to give after
chromatography (CH2Cl2/EtOAc 1:9) oxazolidinone 12a (55 mg,
25%) and oxazolidinone 12b (55 mg, 25%).
12a: 1H NMR (CDCl3, 300 MHz)
d (ppm): 7.45e7.25 (m, 5H, Har);
5.22 (q, 1H, CH3CHN, J¼7.3); 4.83 (d, 1H, 2-H, J2-3¼8.3); 4.47 (dd, 1H,
4a-H, J4a-4b¼10.6, J4a-3¼1.5); 4.34 (dd, 1H, 4b-H, J4b-4a¼10.6, J4b-
¼5.1); 4.22 (ddd, 1H, 3-H, J3-2¼8.3, J3-4b¼5.1, J3-4a¼1.5); 1.68 (d, 3H,
3
4.2.5. (2S*,3S*,4S*)-4-Amino-2-tetradecyltetrahydrofuran-3-ol (ra-
cemic jaspine B). KOH (34.5 mg, 0.62 mmol) was added to a solu-
tion of oxazolidinone (20 mg, 0.062 mmol) in EtOH/H2O (8:2)
(1.5 mL). The mixture was heated at 85 ꢀC for 24 h before being
cooled to rt and diluted with EtOAc and brine. The mixture was
extracted three times with EtOAc and the combined extracts were
concentrated to dryness. The residue was purified by flash chro-
matography on silica gel (EtOAc/MeOH/NH4OH 84.2:15:0.8) to give
racemic jaspine B (15.6 mg, 85%). All analyses were in agreement
with the data reported in the literature.8d
CH3CHN, J¼7.3). 13C NMR (CDCl3, 75 MHz)
d (ppm): 170.5 (C-1);
155.9 (C]O); 137.6 (Cqar); 129.2 (Car); 128.7 (Car); 127.2 (Car); 71.3
(C-4); 69.8 (C-2); 54.1 (C-3); 53.5 (CH3CH); 18.6 (CH3CH). [
a
]
20 þ0.9
D
(c 1.0, CHCl3). HRMS m/z: calcd for C13H14NO4 [MþH]þ: 248.0935;
found: 248.0923.
12b: 1H NMR (CDCl3, 300 MHz)
d (ppm): 7.45e7.3 (m, 5H, Har);
5.21 (q, 1H, CH3CHN, J¼7.1); 4.95 (d, 1H, 2-H, J2-3¼8.3); 4.62 (ddd,
1H, 3-H, J3-2¼8.3, J3-4a¼5.1, J3-4b¼1.4); 3.96 (dd, 1H, 4a-H, J4a-
¼10.9, J4a-3¼5.1); 3.47 (dd, 1H, 4b-H, J4b-4a¼10.9, J4b-3¼1.4); 1.67
4b
(d, 3H, CH3CHN, J¼7.1). 13C NMR (CDCl3, 75 MHz)
d (ppm): 170.4 (C-
1); 155.7 (C]O); 138.9 (Cqar); 129.3 (Car); 128.8 (Car); 127.0
(Car); 69.9 (C-2); 69.8 (C-4); 53.5 (C-3); 52.7 (CH3CH); 15.7 (CH3CH).
4.2.6. (1R,5S)-6-((R)-1-Phenylethyl)-3-oxa-6-azabicyclo[3.1.0]
hexan-2-one (11a) and (1S,5R)-6-((R)-1-phenylethyl)-3-oxa-6-
[
a
]
20 ꢁ180.8 (c 0.9, CHCl3). HRMS m/z: calcd for C13H14NO4 [MþH]þ:
D
azabicyclo[3.1.0]hexan-2-one (11b). To
a
solution of
D-eryth-
248.0929; found: 248.0923.
ronolactone (1.55 g, 13.1 mmol) in dichloromethane (62 mL) held at
ꢁ78 ꢀC under argon were successively added pyridine (5.31 mL,
65.6 mmol) and a solution of trifluoromethanesulfonic anhydride
(10.0 g, 35.4 mmol) in CH2Cl2 (16 mL). After 15 min of stirring at
ꢁ78 ꢀC, the reaction mixture was slowly warmed to ꢁ25 ꢀC over
a period of 3.5 h. The reaction solution was then poured into cold
Et2O (150 mL). The precipitate was filtered, and the filtrate was
evaporated under reduced pressure at 0 ꢀC. The resulting residue
was rapidly purified by filtration on silica gel (Et2O) to afford triflate
10 as a yellow oil, which was directly reacted in the next step. To
a solution of compound 10 (1.68 g, 7.23 mmol) in DMF (35 mL) at
4.2.8. (3aS,6S,6aS)-6-Ethyltetrahydrofuro[3,4-d]oxazol-2(3H)-one
((þ)-9). The protocol used for the synthesis of 9 was applied to
PMB-protected compound (þ)-8 (41 mg, 0.093 mmol) and CAN
(310 mg, 0.56 mmol) in CH3CN/H2O (9:1) (3 mL) to give the com-
pound (þ)-9 (20 mg, 66%). All analyses were in agreement with the
20
data reported in the literature.8d
[
a
]
þ65.0 (c 0.8, CHCl3) [Lit.8d
D
[a
]
20 þ66.5 (c 1.2, CHCl3)].
D
4.2.9. (2S,3S,4S)-4-Amino-2-tetradecyltetrahydrofuran-3-ol (jaspine
B). The protocol used for the synthesis of racemic jaspine B was
applied to oxazolidinone (þ)-9 (20 mg, 0.062 mmol) and KOH
(34.5 mg, 0.62 mmol) in EtOH/H2O (8:2) (1.5 mL) to give jaspine B
(17 mg, 92%). All analyses were in agreement with the data re-
ꢁ30 ꢀC under argon was added dropwise (R)-(þ)-
a-methyl-
benzylamine (1.40 mL, 10.8 mmol). The reaction mixture was stir-
red for at ꢁ30 ꢀC overnight before being diluted with EtOAc (50 mL)
and water (50 mL). The layers were separated, and the aqueous
phase was extracted with EtOAc (2ꢃ50 mL). The combined
organic extracts were dried over magnesium sulfate and concen-
trated to dryness. The resulting residue was purified by flash
chromatography on silica gel (Et2O/petroleum ether 2:1) to give
(1R,5S)-6-((R)-1-phenylethyl)-3-oxa-6-azabicyclo[3.1.0]hexan-2-
one (11a) (60 mg, 2%), (1S,5R)-6-((R)-1-phenylethyl)-3-oxa-6-
azabicyclo[3.1.0]hexan-2-one (11b) (60 mg, 2%) and the mixture
of the two diastereoisomers (460 mg, 17%).
ported in the literature.8d
(c 0.1, EtOH)].
[
a
]
D
20 þ18.8 (c 0.85, EtOH) [Lit.1 [
a
]
20 þ18
D
4.2.10. (3aR,6R,6aR)-6-Ethyltetrahydrofuro[3,4-d]oxazol-2(3H)-one
((ꢁ)-9). The protocol used for the synthesis of 9 was applied to PMB-
protected compound (ꢁ)-8 (41 mg, 0.093 mmol) and CAN (310 mg,
0.56 mmol) in CH3CN/H2O (9:1) (3 mL) to give the compound (ꢁ)-9
(20 mg, 66%). NMR spectral data and mass spectroscopy were
identical to those of compound (þ)-9. [
a
]
20 ꢁ65.7 (c 1.0, CHCl3).
D
11a: 1H NMR (CDCl3, 300 MHz)
d (ppm): 7.4e7.1 (m, 5H, Har);
4.13 (d, 1H, 4a-H, J4a-4b¼9.9); 4.04 (dd, 1H, 4b-H, J4b-4a¼9.9, J4b-
4.2.11. (2R,3R,4R)-4-Amino-2-tetradecyltetrahydrofuran-3-ol (ent-
jaspine B). The protocol used for the synthesis of jaspine B was
applied to oxazolidinone (ꢁ)-9 (20 mg, 0.062 mmol) and KOH
(34.5 mg, 0.62 mmol) in EtOH/H2O (8:2) (1.5 mL) to give ent-jaspine
B (16 mg, 87%). NMR spectral data and mass spectroscopy were
¼2.9); 2.74 (dd, 1H, 3-H, J3-2¼4.4, J3-4b¼3.0); 2.67 (d, 1H, 2-H, J2-
3
¼4.5), 2.61 (q, 1H, CH3CHN, J¼6.5); 1.42 (d, 3H, CH3CHN, J¼6.5). 13
C
3
NMR (CDCl3, 75 MHz) d (ppm): 172.5 (C-1); 143.0 (Cqar); 128.7 (Car);
127.7 (Car); 126.5 (Car); 69.7 (C-4); 67.1 (CH3CH); 41.5 (C-3); 40.2

C. Santos et al. / Tetrahedron 69 (2013) 7227e7233
7233
20
20 ꢁ19.0 (c 0.8, EtOH) [Lit.10c
[a]
D
3. Salma, Y.; Lafont, E.; Therville, N.; Carpentier, S.; Bonnafe, M. J.; Levade, T.;
Genisson, Y.; Andrieu-Abadie, N. Biochem. Pharmacol. 2009, 78, 477e485.
identical to those of jaspine B. [
ꢁ17.7 (c 0.4, EtOH)].
a
]
D
ꢀ
4. (a) Canals, D.; Mormeneo, D.; Fabrias, G.; Llebaria, A.; Casas, J.; Delgado, A.
Bioorg. Med. Chem. 2009, 17, 235e241; (b) Yoshimitsu, Y.; Oishi, S.; Miyagaki, J.;
Inuki, S.; Ohno, H.; Fujii, N. Bioorg. Med. Chem. 2011, 19, 5402e5408; (c) Yoo, H.;
Lee, Y. S.; Lee, S.; Kim, S.; Kim, T. Y. Phytother. Res. 2012, 26, 1927e1933.
5. Shin, D. H.; Kim, T. Y. U.S. Patent, US 2012/0071424 A1, 2012.
4.3. Separation of enantiomers of ( )-8
Chemicals. Solvents used were HPLC grade methanol (MeOH)
and dichloromethane (CH2Cl2) provided by Carlo Erba Reagents
(France). Carbon dioxide was provided by Linde (France).
Samples preparation. 58 mg in 2.0 mL of CH2Cl2, the concentra-
tion was 30 g/L.
6. For reviews see: (a) Abraham, E.; Davies, S. G.; Roberts, P. M.; Russell, A. J.;
Thomson, J. E. Tetrahedron: Asymmetry 2008, 19, 1027e1047; (b) Ballereau, S.;
ꢀ
Baltas, M.; Genisson, Y. Curr. Org. Chem. 2011, 15, 953e986.
7. (a) Inuki, S.; Yoshimitsu, Y.; Oishi, S.; Fujii, N.; Ohno, H. Org. Lett. 2009, 11,
4478e4481; (b) Urano, H.; Enomoto, M.; Kuwahara, S. Biosci. Biotechnol. Bio-
chem. 2010, 74, 152e157; (c) Inuki, S.; Yoshimitsu, Y.; Oishi, S.; Fujii, N.; Ohno, H.
J. Org. Chem. 2010, 75, 3831e3842; (d) Vichare, P.; Chattopadhyay, A. Tetrahe-
dron: Asymmetry 2010, 21, 1983e1987; (e) Srinivas Rao, G.; Venkateswara Rao,
B. Tetrahedron Lett. 2011, 52, 6076e6079; (f) Passiniemi, M.; Koskinen, A. M. P.
Org. Biomol. Chem. 2011, 9, 1774e1783; (g) Yoshimitsu, Y.; Inuki, S.; Oishi, S.;
Fujii, N.; Ohno, H. J. Org. Chem. 2010, 75, 3843e3846; (h) Llaveria, J.; Díaz, Y.;
Apparatus and operating conditions. The separation of both en-
antiomers and the analysis of purified fractions were carried out
using manufactured equipment with three model HPLC K-501
Knauer pumps, two used for carbon dioxide and one for the mod-
ifier. Control of the mobile phase composition was performed by
the modifier pump. The pump head used for pumping the carbon
dioxide was cooled to ꢁ10 ꢀC by a cryostat (Minichiller, Huber). The
ꢀ
Matheu, M. I.; Castillon, S. Eur. J. Org. Chem. 2011, 1514e1519; (i) Bae, H.; Jeon, H.;
Baek, D. J.; Lee, D.; Kim, S. Synthesis 2012, 44, 3609e3612; (j) Yoshimitsu, Y.;
Miyagaki, J.; Oishi, S.; Fujii, N.; Ohno, H. Tetrahedron 2013, 69, 4211e4220; (k)
Srinivas Rao, G.; Chandrasekhar, B.; Venkateswara Rao, B. Tetrahedron: Asym-
metry 2012, 23, 564e569.
injector valve was supplied with a 50
HT300L allowed from 1 to 500 L injection volumes. The columns
were thermostated by an oven regulated at 35 ꢀC. A Chiralpak IC
column (5 m silica particles immobilized with cellulose tris-(3,5-
mL loop. The autosampler
8. (a) Chandrasekhar, S.; Tiwari, B.; Prakash, S. J. Arkivoc 2006, 155e161; (b)
m
ꢀ
Genisson, Y.; Lamande, L.; Salma, Y.; Andrieu-Abadie, N.; Andre, C.; Baltas, M.
Tetrahedron: Asymmetry 2007, 18, 857e864; (c) Rives, A.; Ladeira, S.; Levade, T.;
ꢀ
Andrieu-Abadie, N.; Genisson, Y. J. Org. Chem. 2010, 75, 7920e7923; (d) Salma, Y.;
m
ꢀ
Ballereau, S.; Maaliki, C.; Ladeira, S.; Andrieu-Abadie, N.; Genisson, Y. Org. Biomol.
dichlorophenylcarbamate), 250ꢃ4.6 mm for analytical scale and
250ꢃ10 mm for preparative scale) was used with a 25% of a CH2Cl2/
MeOH mixture (80:20, v/v) as an additive in a CO2 mobile phase.
The flowrate was 4 mL for analytical scale and 12 mL/min for pre-
parative scale and the outlet pressure was 100 bars.
Chem. 2010, 8, 3227e3243; (e) Ballereau, S.; Andrieu-Abadie, N.; Saffon, N.;
ꢀ
Genisson, Y. Tetrahedron 2011, 67, 2570e2578; (f) Jeon, H.; Bae, H.; Baek, D. J.;
Kwak, Y.-S.; Kim, D.; Kim, S. Org. Biomol. Chem. 2011, 9, 7237e7242; (g) Salma, Y.;
ꢀ
Ballereau, S.; Ladeira, S.; Lepetit, C.; Chauvin, R.; Andrieu-Abadie, N.; Genisson, Y.
Tetrahedron 2011, 67, 4253e4262.
9. (a) Jayachitra, G.; Sudhakar, N.; Anchoori, R. K.; Rao, B. V.; Roy, S.; Banerjee, R.
Synthesis 2010, 115e119; (b) Sudhakar, N.; Kumar, A. R.; Prabhakar, A.; Jaga-
deesh, B.; Rao, B. V. Tetrahedron Lett. 2005, 46, 325e327; (c) Abraham, E.;
Candela-Lena, J. I.; Davies, S. G.; Georgiou, M.; Nicholson, R. L.; Roberts, P. M.;
Russell, A. J.; Sanchez-Fernandez, E. M.; Smith, A. D.; Thomson, J. E. Tetrahedron:
Asymmetry 2007, 18, 2510e2513; (d) van den Berg, R.; Boltje, T. J.; Verhagen, C. P.;
Litjens, R.; van der Marel, G. A.; Overkleeft, H. S. J. Org. Chem. 2006, 71, 836e839;
(e) Abraham, E.; Brock, E. A.; Candela-Lena, J. I.; Davies, S. G.; Georgiou, M.;
Nicholson, R. L.; Perkins, J. H.; Roberts, P. M.; Russell, A. J.; Sanchez-Fernandez, E.
M.; Scott, P. M.; Smith, A. D.; Thomson, J. E. Org. Biomol. Chem. 2008, 6,
1665e1673; (f) Abraham, E.; Brock, E. A.; Candela-Lena, J. I.; Davies, S. G.;
Georgiou, M.; Nicholson, R. L.; Perkins, J. H.; Roberts, P. M.; Russell, A. J.; Sanchez-
Fernandez, E. M.; Scott, P. M.; Smith, A. D.; Thomson, J. E. Org. Biomol. Chem. 2008,
6, 4668; (g) Reddipalli, G.; Venkataiah, M.; Mishra, M. K.; Fadnavis, N. W. Tetra-
hedron: Asymmetry 2009, 20, 1802e1805; (h) Sanchez-Eleuterio, A.; Quintero, L.;
Sartillo-Piscil, F. J. Org. Chem. 2011, 76, 5466e5471; (i) Lee, D. Synlett 2012,
2840e2844.
The detector was Smartline UV 2600 Knauer detector. UV de-
tection was carried out at 270 nm. Injection volumes were 10
analytical scale and 50 L for preparative scale.
mL for
m
Both isomers were obtained with an enantiomeric purity supe-
rior to 99.5% in the re-analysis (see ESD) and in 80% yield (23 mg).
4.4. Biological evaluation
For cytotoxicity evaluation, 3000 cells (HCT116, GM637H or
U2OS) were seeded per wells in 96-wells plates and, 24 h later,
were treated with concentrations ranging from 10 nM to 50
(8 replicates for each) for jaspine B and from 175 nM to 100
m
m
M
M
(8 replicates for each) for ent-jaspine B. After 4 days of treatment,
cells were incubated with the cell proliferation reagent WST-1
(Roche) for 3-4 h and the absorbance was then measured with
a scanning multi-well spectrophotometer at 450 nm. The measured
absorbance directly correlates to the number of viable cells. Data
were analyzed using Prism softwares.
10. (a) Ramana, C. V.; Giri, A. G.; Suryawanshi, S. B.; Gonnade, R. G. Tetrahedron Lett.
2007, 48, 265e268; (b) Cruz-Gregorio, S.; Espinoza-Rojas, C.; Quintero, L.;
Sartillo-Piscil, F. Tetrahedron Lett. 2011, 52, 6370e6371; (c) Prasad, K. R.; Pen-
chalaiah, K. Tetrahedron: Asymmetry 2011, 22, 1400e1403.
11. (a) Valle, M. S.; Saraiva, M. F.; Retailleau, P.; de Almeida, M. V.; Dodd, R. H. J. Org.
Chem. 2012, 77, 5592e5599; (b) Dauban, P.; de Saint-Fuscien, C.; Dodd, R. H.
Tetrahedron 1999, 55, 7589e7600; (c) Dubois, L.; Mehta, A.; Tourette, E.; Dodd,
R. H. J. Org. Chem. 1994, 59, 434e441.
12. (a) Tarrade, A.; Dauban, P.; Dodd, R. H. J. Org. Chem. 2003, 68, 9521e9524; (b)
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Chem. 2009, 673e686; (c) Valle, M. S.; Tarrade-Matha, A.; Dauban, P.; Dodd, R.
H. Tetrahedron 2008, 64, 419e432.
Acknowledgements
The chiral chromatography separation was carried out on the
equipment of the technical platform of the Institute of Chemistry of
Toulouse (ICTdFR CNRS 2599).
The biological evaluations were carried out by the Platform of
biological activities evaluation at ITAV-USR35005, Centre Pierre
Potier in Toulouse.
13. Stankovic, S.; D’Hooghe, M.; Catak, S.; Eum, H.; Waroquier, M.; Van Speybroeck,
V.; De Kimpe, N.; Ha, H.-J. Chem. Soc. Rev. 2012, 41, 643e665.
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Chem. 2003, 68, 104e108.
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Supplementary data
́
Copies of 1H and 13C NMR spectra of new compounds, supple-
mentary crystallographic data and analytical chiral HPLC chro-
matograms. Supplementary data related to this article can be found
at http://dx.doi.org/10.1016/j.tet.2013.06.091.
18. The stereochemistry of the double bond was established by analogy with
compounds described in the literature (Ref. 7c).
€
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References and notes
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