Total synthesis of (±)-dysibetaine CPa and analogs

Article abstract of DOI:10.1002/ejoc.201200730

The syntheses of the marine sponge-derived γ-amino carboxylic acid dysibetaine CPa and five analogs in their racemic forms were successfully performed by taking advantage of an electron-withdrawing N-(4-nitrophenyl) group in the cyclopropanation reaction,

Full text of DOI:10.1002/ejoc.201200730

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
FULL PAPER
DOI: 10.1002/ejoc.201200730
Total Synthesis of (؎)-Dysibetaine CPa and Analogs
Masato Oikawa,*[a] Shota Sasaki,[a] Michihiro Sakai,[a] Yuichi Ishikawa,[a] and
Ryuichi Sakai[b]
Dedicated to the memory of Professor Tetsuo Shiba
Keywords: Total synthesis / Natural products / Amino acids / Neurological agents / Diastereoselectivity / Chemoselectivity
The syntheses of the marine sponge-derived γ-amino carbox- an electron-withdrawing N-(4-nitrophenyl) group in the cy-
ylic acid dysibetaine CPa and five analogs in their racemic
forms were successfully performed by taking advantage of
clopropanation reaction, the reductive ring opening of an
imide, and the ethanolysis of an N-Boc-protected imide.
(DH),[2] neodysiherbaine (NDH),[3] dysibetaine (DB),[4] and
dysibetaines CPa (DBCPa, 1) and CPb (DBCPb, 2).[5] DH
and NDH are glutamate analogs with potent convulsant
activity.[6] DH exhibits a high affinity toward iGluRs such
as recombinant GluK1 and GluK2 kainate receptors
(KARs),[7] whereas NDH binds to GluK1 and GluK2 with
15- to 25-fold lower affinities.[8] Previously, we demon-
strated that the structural modification of natural products
by de novo organic synthesis is a useful approach to ef-
ficiently develop ligands with new specificities for iGluR
subunit proteins. That is, we synthetically developed
MSVIII-19, which lacks functional groups at the C-8 and
C-9 positions of the DH structure, as a weak partial agonist
for KARs. MSVIII-19 binds with a high affinity, but exhib-
its extraordinarily low efficacy, thereby acting as a func-
tional antagonist of GluK1 KARs, and i.c.v. (intracerebrov-
entricular) injection (0.002–0.020 mg/mouse) results in a
coma-like unconscious state for up to 6 h in vivo.[6,8–11]
DBCPa (1) and DBCPb (2), whose isolation and struc-
ture were reported in 2004,[5] are cyclopropane carboxylic
acids bearing quaternary ammonium groups. From a struc-
tural point of view, 1 and 2 have attracted significant atten-
tion as potential ligands for neuronal receptors such as γ-
aminobutyric acid (GABA) receptors, as they incorporate
Introduction
Ligands for ionotropic glutamate receptors (iGluRs) are
of particular importance for studying biological functions
of structurally diverse iGluRs in the central nervous system,
and a number of glutamate analogs, such as kainic acid,
domoic acid, acromelic acid, and kaitocephalin, have been
identified in natural resources.[1] Lendenfeldia chondrodes, a
Micronesian marine sponge, contains the structurally di-
verse amino acids shown in Figure 1, that is, dysiherbaine
Figure 1. Amino acids isolated from L. chondrodes and synthetic a GABA motif. However, at most only a weak affinity to
analog MSVIII-19.
iGluRs has been clarified for 1 and 2 in radioligand binding
assays, that is, 1 and 2 displaced [3H]KA from cortical
membrane proteins with IC50 (half maximal inhibitory con-
[a] Graduate School of Nanobioscience and University-Industry
centration) values of approximately 10 μm and 4.9Ϯ2.3 μm,
respectively.[5] In addition, the biological action of 1 and 2
on GABA receptors has not yet been studied because of
the limited availability from natural resources. We antici-
pated that de novo synthetic modifications of 1 and 2 would
generate a more robust source of the analogs and facilitate
new biological studies with these unusual molecules. In
Cooperative Research Center, Yokohama City University,
Seto 22-2, Kanazawa-ku, Yokohama 236-0027, Japan
Fax: +81-45-787-2403
E-mail: moikawa@yokohama-cu.ac.jp
Homepage: http://oiklab.sci.yokohama-cu.ac.jp/
[b] Graduate School of Fisheries Sciences, Hokkaido University,
Minato-cho, Hakodate 041-8611, Japan
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200730.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
M. Oikawa, S. Sasaki, M. Sakai, Y. Ishikawa, R. Sakai
FULL PAPER
2007, the first synthesis of DBCPa (1) in its racemic form
Therefore, we explored the synthetic approach by using
was reported by Donaldson et al.[12] This synthesis featured cyclic imides to accomplish the functional-group differenti-
the formation of the cyclopropane ring, starting from a re- ation efficiently. Because substituents on the imide-nitrogen
action between a [(pentadienyl)iron]1+ cation and nitro- were expected to control the reactivity, we planned for the
methane anion, and successfully confirmed the relative seven cyclopropane-fused succinimides (12–17 and 19) to
stereochemistry of 1. However, the synthesis was not practi- use in our experiments and prepared them as shown in
cal in terms of the preparation of pure specimens of struc- Scheme 2. Thus, the cyclopropanation of commercially
tural analogs, which are necessary for detailed biological available maleimide (7) and N-phenylmaleimide (8) along
evaluations. Herein, we report the synthesis of racemic with the two synthetic maleimides 9 and 10, prepared by
DBCPa (1),[13] which will then extend to its asymmetric the conventional two-step condensation of maleic anhy-
synthesis to determine its absolute stereochemistry. More- dride and amines (AcOH; NaOAc, Ac2O, 100 °C),[21] was
over, our synthetic route was capable of synthesizing five carried out by using ethoxycarbonyl- and tert-butoxy-
racemic analogs, as discussed below.
carbonyl-substituted sulfonium ylides 3[20] and 11 at 65 °C.
Generally, cis-cyclopropanes 13–17 were obtained as the
major products in moderate yields, along with trans isomers
such as 18 as the minor products. The reaction with malei-
mide (7) was an exception, wherein trans isomer 12 was pre-
dominantly obtained in 31% yield. It should be noted that
N-(4-nitrophenyl)maleimide (10) provided adduct 17 in the
highest yield (48%), among the reactions with all of the
maleimides 7–10, probably owing to the electron-with-
drawing nature of the 4-nitrophenyl group. The stereochem-
istry was determined on the basis of the results from a
NOESY experiment on 17, as shown in Figure 2, and was
finally confirmed by transforming diastereomer 18 into
dysibetaine CPa (1, see discussion below). All of the other
products were assigned by analogy. The cyclopropanation
of N-substituted maleimides 8–10 provided products in
favor of the cis isomers over the trans isomers, and the
stereoselectivities are in good agreement with previous ob-
servations.[22] N-PMB imide 19 with a trans configuration
was synthesized (PMBCl, K2CO3) from trans-imide 12.[23]
Results and Discussion
Several methods have been reported for the construction
of 1,2-disubstituted cyclopropanes to prepare cyclopro-
pane-containing GABA analogs.[14] The key reactions in-
clude: (1) an intramolecular alkylative cyclization reac-
tion[15] and (2) a diastereoselective cyclopropanation of β-
hydroxy-γ,δ-unsaturated carbonyl compounds.[16] However,
these methodologies are limited to 1,2-disubstituted cyclo-
propanes and not applicable to 1,2,3-trisubstituted cyclo-
propanes such as DBCPa (1) and DBCPb (2), which are
the unique examples of 1,2,3-trisubstituted cyclopropanes
found in natural products.[5] Although related compounds
such as DCV-IV,[17] carene-derived analogs,[18] and some
GABA analogs[19] have been generated previously, synthetic
methods for entry into the 1,2,3-trisubstituted cyclopropane
motif have not been well established.
In 2000, Aggarwal et al. reported the synthesis of trans-
1,2,3-cyclopropanetricarboxylic acid triethyl ester (5) using
sulfonium ylide 3 and diethyl fumarate (4, see Scheme 1).[20]
Initially, we anticipated that 5 would serve as a key interme-
diate for the synthesis of 6, which should be a direct precur-
sor to DBCPa (1). However, upon several experiments, the
transformation of 5 into 6 was not readily realized, because
of the following: (1) the poor selectivity in the functional-
group differentiation on 5 by alkaline or hydride treatment,
for example, and (2) the epimerization observed under the
reducing conditions.
Scheme 2. Preparation of cyclopropane-fused succinimides. Ab-
breviations are PMP = 4-methoxyphenyl, NP = 4-nitrophenyl, and
PMB = 4-methoxybenzyl.
Scheme 1. Our initial plan toward DBCPa (1) by way of known
triester 5.
2
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
Total Synthesis of (Ϯ)-Dysibetaine CPa and Analogs
Table 1. Initial attempts for chemoselective reaction of cyclic imide
over ester functional group.
Figure 2. NOE observed in cis-cyclopropane 17 for determination
of the stereochemistry.
Attempts at the chemoselective alcoholysis or hydrolysis
of the cyclic imide moiety in the presence of the ester func-
tional group by using cis-cyclopropanes 13–17 and trans-
cyclopropanes 12 and 19 are shown in Table 1. We pos-
tulated that cis isomers 13–17 would be especially well-
suited as substrates for our model study, directed toward
the total synthesis of dysibetaine CPa (1) and its analogs,
because the cis-cyclopropane is sterically demanding and
perhaps less reactive than the diastereomeric trans-cyclo-
propanes 12, 18, and 19. In these experiments, we generally
observed three types of products generated: (1) by solvolysis
of the ester (type-A), (2) by opening of the cyclic imide
(type-B, desired), and (3) by uncontrolled reactions at both
sites (type-C).
As shown in Table 1, Entry 1, the simplest imido ester 12
decomposed upon hydrolysis (NaOH, MeOH, H2O). Hy-
drolysis of N-phenylimido ester 13 provided the undesired
carboxylic acid 20A in 76% yield, showing that the ester
functionality is more reactive than the N-phenylimide moi-
ety (see Table 1, Entry 2). The same selectivity was also ob-
served with 4-methoxyphenyl derivative 14 under mild con-
ditions (LiOH, MeOH, H2O, –10 °C), which cleanly gave
undesired carboxylic acid 21A in 93% yield (see Table 1,
Entry 3). Changing the ester to the sterically demanding
tert-butyl ester 15 only resulted in decomposition and did
not improve the selectivity (see Table 1, Entry 4). After sev-
eral experiments, the desired selectivity was first observed
with N-(4-nitrophenyl)imido ester 16, which underwent hy-
drolysis predominantly at the imide functionality by using
LiOH and H2O at 0 °C to provide carboxylic acid 22B in
77% yield (see Table 1, Entry 5). N-NP imido ester 16 not
only underwent hydrolysis but also underwent meth-
anolysis, both proceeding chemoselectively even under neu-
tral conditions. As shown in Table 1, Entry 6, methanolysis
at 100 °C (sealed tube) or under microwave irradiation (ca.
120 °C) without any additives gave the desired methyl ester
23B in 66% yield. Not surprisingly, alcoholysis with the
bulkier EtOH resulted in diminished reactivity, and an
amine additive (Et3N) was required for the reaction to pro-
ceed (17 Ǟ 24B, see Table 1, Entry 7). The reactivity of the
imide was lower in trans-substituted cyclopropane 19 bear-
ing the N-PMB imide, and dicarboxylic acid 25C was
formed in 60% yield, resulting in hydrolysis (NaOH,
MeOH, H2O, 0 °C) of both the ester and imide functionali-
ties (see Table 1, Entry 8). In all of the entries, the cyclopro-
pane ring was stable and unaffected during the reaction.
Next, as a preliminary model study toward the synthesis (Boc = tert-butoxycarbonyl) in the presence of Et3N and
of DBCPa (1), the transformation of amide 24B was exam- DMAP [4-(N,N-dimethylamino)pyridine] provided N-Boc
ined (see Scheme 3). Treatment of the amide with Boc2O imide 26 in excellent yield (97%). However, to our disap-
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
M. Oikawa, S. Sasaki, M. Sakai, Y. Ishikawa, R. Sakai
FULL PAPER
pointment, the ethanolysis of the N-Boc imide 26 gave as
the sole product triethyl ester 5[20] with the trans configura-
tion in 85% yield. The epimerization was apparently a re-
sult of conducting the reaction under such thermodynamic
reaction conditions, suggesting that the transformation of
the 1,2,3-tricarbonylcyclopropane moiety should be care-
fully performed. Also, it should be noted that the cis isomer
of 5 has not been reported to date, probably because of its
instability,[20] and the synthesis still proves to be challeng-
ing.
Scheme 5. Successful reduction of cyclic imide 16 with NaBH4.
Thus, the reduction of N-NP imide 16 by using NaBH4
successfully gave us functional-group differentiation, re-
sulting finally in the total synthesis of (Ϯ)-dysibetaine CPa
(1). As shown in Scheme 6, trans-cyclopropane imide 18
was readily and regioselectively reduced with NaBH4 at
–10 °C to give amidoalcohol 29 in excellent yield (95%). As
expected, the reactivity of imide 18 was higher than that of
the cis-substituted cyclopropane 16 used in the model study
(see Scheme 5). The hydroxy group of 29 was protected
[TESCl (triethylsilyl chloride), Et3N, DMAP, 83%], and
then amide 30 was converted into imide 31 in 86% yield
by treatment with Boc2O, Et3N, and DMAP. The alkaline
ethanolysis of the N-Boc imide by using K2CO3 in EtOH
successfully delivered the diethyl ester, which in turn, was
Scheme 3. Observed epimerization during reaction of cis-cyclo-
propane 26.
Next, to avoid the undesired epimerization, shown in
Scheme 3, the selective reduction of methyl ester 23B was
explored using LiAlH4, to generate primary alcohol 28. As
shown in Scheme 4, 23B was readily reduced at –78 °C, but
the product was unexpected aminal 27 (43% yield). Al-
though no epimerization was detected in the reduction, cy-
clic aminal 27 was not desirable as a synthetic intermediate
for 28, as extensive transformations would be additionally
required.
Scheme 4. Selective reduction of methyl ester 23B.
We further investigated the selective reductions of the
compounds listed in Table 1. After extensive experiments,
N-NP imide 16 was eventually found to be a well-suited
substrate, which was cleanly converted into amido alcohol
28. The reduction of 16 with NaBH4 in THF (tetra-
hydrofuran) and MeOH[24,25] was successfully realized in
76% yield, as shown in Scheme 5. No epimerization was
detected, and 28 was obtained as a single isomer.[26]
Scheme 6. Total synthesis of (Ϯ)-dysibetaine CPa (1) from trans-
cyclopropane 18.
4
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
Total Synthesis of (Ϯ)-Dysibetaine CPa and Analogs
treated with tetra-n-butylammonium fluoride (TBAF) and
AcOH to give alcohol 32 in 74% yield.
Starting from cis-cyclopropane 17, the synthesis of a C-
3 epimer of dysibetaine CPa was also accomplished. As
To introduce nitrogen functionality at C-1 of 32 (using shown in Scheme 8, the synthesis of meso-3-epi-dysibetaine
the dysibetaine CPa numbering scheme), a two-step pro- CPa (44) was essentially identical to that for 1 (see
cedure by way of an iodide intermediate was first examined. Scheme 6), however, undesired side reactions were observed
Although the generation of an intermediary iodide (see in two transformations. First, a substantial amount (33%)
Scheme 7, Intermediate A) was unequivocally confirmed by of 3-epi-aminal intermediate 37 was obtained in the re-
1
TLC and H NMR, the iodide was unstable and readily duction of imide 17 to afford 36 (NaBH4, THF, MeOH,
underwent hydrolysis during purification by silica gel col- –10 °C). Attempts to complete the reaction were unsuccess-
umn chromatography to give the recovered alcohol 32. This ful and resulted in over-reduction (data not shown). Sec-
likely occurred because of the involvement of the neigh- ond, after the alkaline ethanolysis of 39 (K2CO3, EtOH), a
boring ethoxycarbonyl group (see Scheme 7, Intermediate trace amount (Ͻ5%) of the epimerized product, identical
B).
to the ethanolysis product of trans-cyclopropane 31, was
detected. However, the byproduct could be successfully re-
moved by silica gel column chromatography after the desil-
ylation (TBAF, AcOH). The side reactions apparently took
place because of the steric congestion of the cis-arranged
substituents on the cyclopropane ring. Overall, meso-3-epi-
Scheme 7. Plausible reaction mechanism for unexpected hydrolysis
of iodide A derived from 32.
Fortunately, the corresponding bromide 33, synthesized
by treating 32 with CBr4 and PPh3, was stable and isolable
in 85% yield (see Scheme 6). With bromide 33 in hand, we
next constructed the quaternary ammonium salt by examin-
ing two methods: (1) a one-step introduction by using
Me3N[27,28] and (2) a two-step procedure by successive treat-
ment with Me2NH and MeI.[29,30] In the former one-step
method, bromide 33 did not react with Me3N, even at an
elevated temperature (125 °C), and 33 was recovered intact.
On the other hand, the latter two-step reaction proved to
be of value, as shown in Scheme 6 (33 Ǟ 34 Ǟ 35). Thus,
treatment of bromide 33 with Me2NH in toluene at 125 °C
in a sealed tube gave rise to tertiary amine 34 quantitatively,
which was then further treated with CH3I at 125 °C (sealed
tube) to provide quaternary ammonium iodide 35. The ad-
dition of NaHCO3 was essential to complete the reaction.
These experiments indicated that the C-1 position is steri-
cally shielded in comparison to muscarine, which bears an
analogous trimethylammonium group, which is generally
synthesized by using the one-step reaction with Me3N.[27]
Without purification, 35 was hydrolyzed by treatment
with 6 m hydrochloric acid at 90 °C to furnish (Ϯ)-dysib-
etaine CPa (1) in 74% yield. The synthetic specimen was
identical to its natural counterpart chromatographically
(TLC, HPLC) and spectroscopically (1H and 13C NMR),
thus confirming the stereochemical assignments of cyclo-
propanation products 17 and 18.[31] The overall yield was
4.53% over a total of 12 steps, starting from maleic anhy-
dride.
Scheme 8. Synthesis of meso-3-epi-dysibetaine CPa (44) from cis-
cyclopropane 17.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
M. Oikawa, S. Sasaki, M. Sakai, Y. Ishikawa, R. Sakai
FULL PAPER
dysibetaine CPa (44) was synthesized in a total 2.59% yield smoothly at 80 °C by using NaN3 and Bu4NI in DMF (di-
over 12 steps starting from maleic anhydride. methylformamide) to give 47 (73%) and 48 (75%). The hy-
Tertiary ammonium analogs with natural and unnatural drogenolysis of the azide followed by N-Boc protection was
configurations were synthesized by acidic hydrolysis start- attained in a one-pot reaction,[32] giving rise to N-Boc
ing from the synthetic intermediates 34 and 42 (3-epi), amine 49 and 50 in 76% and 56% yields, respectively. It
respectively (see Scheme 9). Thus, (Ϯ)-45 with the natural should be noted that attempts to isolate the intermediate
configuration was obtained in 88% yield, and 46 with the amine lowered the two-step yields to less than 10%, and
unnatural configuration was furnished quantitatively. The hence, the in-situ N-Boc protection was essential. Finally,
overall yields were 5.39% (for 45) and 3.50% (for 46) with using the same hydrolysis procedure as was employed with
a total of 11 steps each, starting from maleic anhydride.
the other analogs (i.e., 1, 44, 45, and 46), 49 and 50 were
deprotected to furnish N-desmethyl analogs (Ϯ)-51 and 52
(meso-3-epi), both in quantitative yields. The overall yields
for 51 and 52 were 4.00% and 1.77%, respectively, with a
total of 12 steps each, starting from maleic anhydride.
Conclusions
In conclusion, we have successfully synthesized dysib-
etaine CPa (DBCPa, 1), a cyclopropane carboxylic acid
bearing a quaternary ammonium group, found in the Mi-
cronesian marine sponge L. chondrodes,[5] in its racemic
form. The de novo synthesis was performed in 2.59% yield
over a total of 12 steps starting from maleic anhydride and
was accomplished by taking advantage of the electron-with-
drawing N-(4-nitrophenyl) group used in the cyclopropan-
ation reaction (10 Ǟ 17 + 18, 74% total), the reductive ring
opening of the imide (18 Ǟ 29, 95%), and the ethanolysis
of the N-Boc imide (31 Ǟ 32, Ͼ74%).[13] This synthetic
route was capable of providing five analogs that are stereo-
isomers and isomers bearing different ammonium group
patterns. To clarify their structure–activity relationships, the
evaluation of their biological activities toward neuronal re-
ceptors is in progress. An asymmetric synthesis is also being
studied in our laboratory to determine the absolute stereo-
chemistry of these compounds as well as develop selective
ligands. Our present study affords synthetic strategies to-
ward this goal.[33]
Scheme 9. Synthesis of tertiary ammonium analogs (Ϯ)-45 and 46
(meso-3-epi).
Scheme 10 depicts the syntheses of N-desmethyl analogs
(Ϯ)-51 and 52 (meso-3-epi) starting from bromides 33 and
41, respectively. The introduction at the C-1 position of an
azide group, as an amino group precursor, proceeded
Experimental Section
General Methods: All reactions susceptible to moisture and air were
carried out in an atmosphere of argon gas, in glassware oven-dried
for 3 h, and in solvents freshly distilled from sodium and benzo-
phenone. Tetrahydrofuran and N-phenylmaleimide (8) were pur-
chased from Wako Pure Chemical Industries. All of the other
chemicals were purchased at the highest commercial grade and
used directly. The experiments by microwave irradiations were car-
ried out using the oven, as reported by Arai et al.[34] Analytical
thin-layer chromatography (TLC) was performed using Merck sil-
ica gel 60 F254 plates (0.25-mm thickness). Flash column
chromatography was carried out using Merck silica gel 60 (230–
400 mesh) or Fuji Silicia silica gel BW-300 (200–400 mesh). Re-
versed-phase silica gel column chromatography was carried out
using Fuji Silicia Chromatorex DM1020T (0.10-mm thickness).
For high performance liquid chromatography (HPLC), the recycl-
ing preparative system LC-918 (Japan Analytical Industries) was
used. The IR spectra were recorded with a Perkin–Elmer Spectrum
One FTIR spectrometer. 1H and 13C NMR spectroscopic data were
recorded with a BRUKER AVANCE 400 spectrometer. The chemi-
Scheme 10. Synthesis of N-desmethyl analogs (Ϯ)-51 and 52 (meso-
3-epi).
6
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
Total Synthesis of (Ϯ)-Dysibetaine CPa and Analogs
cal shift values are reported in δ (ppm) with a reference to the
internal residual solvent [1H NMR, CDCl3 (7.24), D2O (4.70), [D6]-
DMSO (2.62); 13C NMR, CDCl3 (77.0), [D6]DMSO (40.5)]. The
coupling constants (J) are reported in Hertz (Hz). The abbrevi-
ations used to designate the multiplicities are s singlet, d doublet,
t triplet, q quartet, m multiplet, and br. broad. ESI-TOF mass spec-
tra were measured with a Water LCT Premier XE spectrometer.
H), 6.53 (d, J = 12.0 Hz, 1 H), 6.38 (d, J = 12.0 Hz, 1 H) ppm. 13
C
NMR (100 MHz, [D6]DMSO): δ = 168.0, 165.1, 145.8, 143.4,
132.4, 131.1, 126.0 (2ϫ), 120.1 (2ϫ) ppm. HRMS (ESI): calcd. for
+
C10H9N2O5 [M + H]+ 237.0511; found 237.0517. A solution of
the crude maleic acid mono(4-nitrophenyl)amide (962.0 mg) and
AcONa (166.7 mg, 2.03 mmol) in Ac2O (5.8 mL) was heated to
100 °C with stirring. After 4 h, the hot mixture was poured onto
ice (10 g). After the ice melted, the mixture was diluted with CHCl3
(20 mL), and the resulting mixture was washed with saturated
aqueous NH4Cl (5 mL) and brine (5 mL), dried with Na2SO4, and
concentrated under reduced pressure. The residue was purified by
column chromatography on silica gel (10 g, EtOAc/hexane, 80:20)
to give N-(4-nitrophenyl)maleimide (10, 581.1 mg, 65%) as a yellow
Ethyl Pentamethylene-λ4-sulfanylideneacetate (3):[20] To a stirred
solution of pentamethylene sulfide (2.750 g, 26.9 mmol) in acetone
(4.5 mL) at room temp. was added ethyl bromoacetate (2.880 mL,
26.9 mmol). After 47 h, the resulting solid was collected by fil-
tration and washed with cold acetone (5 mL) to give the crude
(ethoxycarbonylmethyl)pentamethylenesulfonium bromide (6.50 g)
as a white solid, which was used without purification in the next
reaction. To a stirred solution of the crude sulfonium bromide
(6.50 g) in CHCl3 (27.0 mL) at 0 °C were added saturated aqueous
K2CO3 (9.2 mL) and aqueous NaOH (50% w/v, 2.0 mL). After stir-
ring at room temp. for 20 min, the mixture was filtered through a
pad of Celite by using CHCl3. The filtrate was dried with Na2SO4
and concentrated under reduced pressure to give ylide 3 (4.500 g,
89% for 2 steps) as a colorless oil, which was used without purifica-
tion in the next reaction; Rf = 0.58 (tBuOH/AcOH/H2O, 33:33:33).
1H NMR (400 MHz, CDCl3): δ = 4.02 (t, J = 7.2 Hz, 2 H), 3.61
(br., 2 H), 3.01 (br., 1 H), 2.75 (d, J = 11.2 Hz, 2 H), 2.10 (d, J =
13.6 Hz, 2 H), 1.77–1.65 (m, 3 H), 1.42 (dd, J = 13.6, 11.2 Hz, 1
H), 1.20 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 170.2, 57.9, 44.9 (2ϫ), 33.0, 24.2, 23.6 (2ϫ), 14.9 ppm. The
other spectroscopic data were in good agreement with those re-
ported.[20]
solid; R = 0.71 (acetone/CHCl , 10:90). IR (film): ν = 3099, 1724,
˜
f
3
1599, 1505, 1343, 1143 cm–1. 1H NMR (400 MHz, CDCl3): δ =
8.31 (d, J = 8.8 Hz, 2 H), 7.65 (d, J = 8.8 Hz, 2 H), 6.91 (s, 2
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 168.5 (2ϫ), 146.1,
137.0, 134.6 (2ϫ), 125.5 (2ϫ), 124.5 (2ϫ) ppm. HRMS (ESI):
+
calcd. for C10H7N2O4 [M + H]+ 219.0406; found 219.0401. The
other spectroscopic data were in good agreement with those re-
ported.[36,37]
tert-Butyl Pentamethylene-λ4-sulfanylideneacetate (11): To a stirred
solution of pentamethylene sulfide (700.0 mg, 6.85 mmol) in acet-
one (1.05 mL) at room temp. was added tert-butyl bromoacetate
(1.010 mL, 6.85 mmol). After stirring at room temp. for 75 h, the
resulting solid was collected by filtration, washed with cold acetone
(5 mL), and dried under air to give the crude (tert-butoxycarbonyl-
methyl)pentamethylenesulfonium bromide (1.800 g, 90%) as a
white solid, which was pure enough to be used in the next reaction
without any further purification; Rf = 0.42 (tBuOH/AcOH/H2O,
33:33:33). 1H NMR (400 MHz, CDCl3): δ = 5.21 (s, 2 H), 4.40 (br.,
2 H), 3.85 (br. d, J = 10.4 Hz, 2 H), 2.26 (br. d, J = 13.6 Hz, 2 H),
1.94–1.79 (m, 4 H), 1.46 (s, 9 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 163.4, 86.0, 43.5, 36.1 (2ϫ), 27.9 (3ϫ), 22.6 (2ϫ),
N-(4-Methoxyphenyl)maleimide (9): According to the original pro-
cedure for the synthesis of N-phenylmaleimide (8) reported by Cava
et al.,[21] N-(4-methoxyphenyl)maleimide (9) was prepared. To a
stirred solution of maleic anhydride (700.0 mg, 7.14 mmol) in acetic
acid (70 mL) at room temp. was added 4-methoxyaniline (p-anis-
idine, 879.0 mg, 7.14 mmol). After 100 min, the mixture was con-
centrated under reduced pressure by coevaporation with toluene
(2ϫ) to give the crude maleic acid mono(4-methoxyphenyl)amide
(1.591 g) as a yellow solid, which was used without purification in
the next reaction. A solution of the crude maleic acid mono(4-
methoxyphenyl)amide (1.300 g) and AcONa (241.1 mg, 2.94 mmol)
in Ac2O (2.7 mL) was heated to 100 °C with stirring. After 4 h, the
hot mixture was poured onto ice (20 g). After the ice melted, the
mixture was diluted with EtOAc (100 mL) and H2O (50 mL), and
the organic layer was separated. The aqueous layer was extracted
with EtOAc (20 mL), and the combined extracts were washed with
brine (20 mL), dried with Na2SO4, and concentrated under reduced
pressure. The residue was purified by column chromatography on
silica gel (30 g, EtOAc/hexane, 15:85) to give N-(4-methoxyphenyl)-
maleimide (9, 950.0 mg, 79%) as a yellow solid; Rf = 0.51 (EtOAc/
hexane, 40:60). The spectroscopic data were in good agreement
with those reported.[35]
22.4 ppm. To
a stirred solution of the sulfonium bromide
(290.0 mg, 0.989 mmol) in CHCl3 (1.2 mL) at 0 °C were added sat-
urated aqueous K2CO3 (0.866 mL) and aqueous NaOH (50% w/v,
0.116 mL). After stirring at room temp. for 20 min, the mixture was
filtered through a pad of Celite by using CHCl3. The filtrate was
dried with Na2SO4 and concentrated under reduced pressure to
give ylide 11 (214.0 mg, 100%) as a colorless oil, which was used
without purification in the next reaction; Rf = 0.64 (tBuOH/AcOH/
H O, 33:33:33). IR (film): ν = 3410, 2938, 2860, 1624, 1437, 1345,
˜
2
1134, 836, 752 cm–1. H NMR (400 MHz, CDCl3): δ = 3.43 (dd, J
1
= 13.6, 11.0 Hz, 2 H), 2.93 (br., 1 H), 2.70 (br. d, J = 11.0 Hz, 2
H), 2.02 (br. d, J = 13.6 Hz, 2 H), 1.71–1.58 (m, 4 H), 1.39 (s, 9
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 170.5, 76.7, 42.4 (2ϫ),
34.9, 29.0 (3ϫ), 24.0 (2ϫ), 23.8 ppm. HRMS (ESI): calcd. for
C11H21O2S+ [M + H]+ 217.1262; found 217.1257.
Ethyl
(1R*,5S*,6r*)-2,4-Dioxo-3-azabicyclo[3.1.0]hexane-6-carb-
oxylate (12): To a stirred solution of ylide 3 (69.9 mg, 0.372 mmol)
in 1,2-dichloroethane (0.744 mL) at 50 °C was added maleimide (7,
108.3 mg, 1.11 mmol). After 100 min, the mixture was filtered
through a pad of Celite by using CHCl3. The filtrate was concen-
trated, and the resulting residue was purified by column
N-(4-Nitrophenyl)maleimide (10): Using the same procedure for the
synthesis of 9, 10 was prepared in a reasonable yield. Thus, to a
stirred solution of maleic anhydride (400.0 mg, 4.08 mmol) in acetic
acid (40.0 mL) at room temp. was added 4-nitroaniline (563.4 mg, chromatography on silica gel (7.5 g, EtOAc/hexane, 80:20) to give
4.08 mmol). After 1.5 h, the mixture was concentrated under re-
duced pressure to give the crude maleic acid mono(4-nitrophenyl)-
amide (962.0 mg) as a yellow solid. The residue was used without
purification in the next reaction. Selected data for the intermediary
trans-cyclopropane 12 (20.9 mg, 31%) as a yellow oil; Rf = 0.40
(EtOAc/hexane, 40:60). IR (film): ν = 3353, 1718, 1350, 1314, 1277,
˜
1
1197, 1034, 921, 807 cm–1. H NMR (400 MHz, CDCl3): δ = 7.15
(br., 1 H), 4.19 (q, J = 7.2 Hz, 2 H), 2.85 (dd, J = 2.8, 1.6 Hz, 2
H), 2.52 (dd, J = 2.8, 2.8 Hz, 1 H), 1.27 (t, J = 7.2 Hz, 3 H) ppm.
amide: R = 0.60 (EtOAc/hexane, 50:50). IR (KBr): ν = 3298, 3089,
˜
f
1707, 1515, 1338, 1308, 1274, 1112 cm–1. 1H NMR (400 MHz, 13C NMR (100 MHz, CDCl3): δ = 171.8 (2ϫ), 167.3, 62.3, 32.0,
27.7 (2ϫ) ppm. HRMS (ESI): calcd. for C8H10NO4 [M + H]+
+
[D6]DMSO): δ = 8.25 (d, J = 9.2 Hz, 2 H), 7.87 (d, J = 9.2 Hz, 2
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
M. Oikawa, S. Sasaki, M. Sakai, Y. Ishikawa, R. Sakai
FULL PAPER
184.0610; found 184.0605. The stereochemistry of 12 was deter-
mined to be trans by comparing the H NMR spectroscopic data
with those of trans-cyclopropane 18.
(97.9 mg, 26%) as yellow oils. The stereochemistry of 17 and 18
was assigned on the basis of the results from a NOESY analysis,
as discussed in the text (see Figure 2). Data for cis-cyclopropane
1
17: R = 0.21 (EtOAc/hexane, 40:60). IR (film): ν = 2992, 1746,
˜
f
Ethyl (1R*,5S*,6s*)-2,4-Dioxo-3-phenyl-3-azabicyclo[3.1.0]hexane-
6-carboxylate (13): According to the same procedure for the synthe-
sis of 12, N-phenylmaleimide (8, 69.1 mg, 0.399 mmol) and ylide 3
(50.0 mg, 0.266 mmol) gave cis-cyclopropane 13 (30.0 mg, 44%) as
1694, 1520, 1349, 1313, 1198 cm–1. 1H NMR (400 MHz, CDCl3):
δ = 8.28 (d, J = 9.2 Hz, 2 H), 7.58 (d, J = 9.2 Hz, 2 H), 4.17 (q, J
= 7.2 Hz, 2 H), 2.99 (d, J = 8.4 Hz, 2 H), 2.68 (dd, J = 8.4, 8.4 Hz,
1 H), 1.23 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 169.5 (2ϫ), 167.3, 146.7, 137.1, 127.0 (2ϫ), 124.2 (2ϫ), 62.4,
a colorless oil; R = 0.40 (EtOAc/hexane, 40:60). IR (film): ν =
˜
f
3080, 2983, 1715, 1598, 1501, 1387, 1300, 1189, 869, 758, 694 cm–1.
1H NMR (400 MHz, CDCl3): δ = 7.44–7.31 (m, 5 H), 4.18 (q, J =
8.0 Hz, 2 H), 2.93 (d, J = 8.4 Hz, 2 H), 2.64 (dd, J = 8.4, 8.4 Hz,
1 H), 1.24 (t, J = 8.0 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 170.4, 167.3, 131.5, 129.0 (2ϫ), 128.5, 128.3, 126.5 (2ϫ), 62.3,
+
31.3, 27.0 (2ϫ), 13.9 ppm. HRMS (ESI): calcd. for C14H13N2O6
[M + H]+ 305.0774; found 305.0768. Data for trans-cyclopropane
18: R = 0.59 (EtOAc/hexane, 40:60). IR (film): ν = 2989, 1721,
˜
f
1684, 1521, 1352, 1292, 1212 cm–1. 1H NMR (400 MHz, CDCl3):
δ = 8.29 (d, J = 8.8 Hz, 2 H), 7.49 (d, J = 8.8 Hz, 2 H), 4.23 (q, J
= 7.2 Hz, 2 H), 3.07 (d, J = 2.8 Hz, 2 H), 2.62 (dd, J = 2.8, 2.8 Hz,
1 H), 1.30 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
δ = 170.4 (2ϫ), 166.8, 146.8, 136.6, 126.5 (2ϫ), 124.4 (2ϫ), 62.5,
+
31.5, 26.8 (2ϫ), 14.0 ppm. HRMS (ESI): calcd. for C14H14NO4
[M + H]+ 260.0923; found 260.0916.
Ethyl (1R*,5S*,6s*)-3-(4-Methoxyphenyl)-2,4-dioxo-3-azabicyclo-
[3.1.0]hexane-6-carboxylate (14): According to the same procedure
for the synthesis of 12, N-(4-methoxyphenyl)maleimide (9, 86.4 mg,
0.425 mmol) and ylide 3 (100.0 mg, 0.532 mmol) gave cis-cyclopro-
pane 14 (28.7 mg, 25%) as a colorless oil; Rf = 0.36 (EtOAc/hexane,
+
31.8, 26.5 (2ϫ), 14.1 ppm. HRMS (ESI): calcd. for C14H13N2O6
[M + H]+ 305.0774; found 305.0771.
Ethyl (1R*,5S*,6r*)-3-(4-Methoxybenzyl)-2,4-dioxo-3-azabicyclo-
[3.1.0]hexane-6-carboxylate (19): To a stirred solution of imide 12
(20.0 mg, 0.109 mmol) and K2CO3 (15.1 mg, 0.109 mmol) in ace-
tone (0.18 mL) at 65 °C was added 4-methoxybenzyl chloride
(0.296 mL, 0.218 mmol). After 1 h, the temperature was raised to
75 °C, and the stirring was continued for 15 h. H2O (0.5 mL) was
added, and the mixture was extracted with EtOAc (3ϫ2 mL). The
combined organic extracts were washed with brine (1 mL) and
dried with Na2SO4. The residue was purified by column
chromatography on silica gel (2 g, EtOAc/benzene, 10:90) to give
PMB ether 19 (6.4 mg, 19%) as a yellow oil; Rf = 0.55 (EtOAc/
50:50). IR (film): ν = 3078, 2917, 1713, 1515, 1392, 1300, 1251,
˜
1190, 1066, 1033, 832 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.23
(d, J = 8.8 Hz, 2 H), 6.94 (d, J = 8.8 Hz, 2 H), 4.18 (q, J = 7.2 Hz,
2 H), 3.79 (s, 3 H), 2.92 (d, J = 8.0 Hz, 2 H), 2.62 (dd, J = 8.0,
8.0 Hz, 1 H), 1.24 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 170.7 (2ϫ), 167.3, 159.4, 127.8 (2ϫ), 124.2, 114.5 (2ϫ),
62.2, 55.4, 31.5, 26.7 (2ϫ), 14.0 ppm. HRMS (ESI): calcd. for
+
C15H16NO5 [M + H]+ 290.1028; found 290.1024.
tert-Butyl (1R*,5S*,6s*)-3-(4-Methoxyphenyl)-2,4-dioxo-3-azabicy-
clo[3.1.0]hexane-6-carboxylate (15): According to the same pro-
cedure for the synthesis of 12, N-(4-methoxyphenyl)maleimide (9,
40.4 mg, 0.199 mmol) and ylide 11 (53.8 mg, 0.249 mmol) gave cis-
cyclopropane 15 (25.6 mg, 40%) as a colorless oil; Rf = 0.28
hexane, 40:60). IR (film): ν = 3083, 2955, 1711, 1514, 1393, 1248,
˜
1193, 1035 cm–1. 1H NMR (400 MHz, CDCl3): δ = 7.22 (d, J =
8.8 Hz, 2 H), 6.80 (d, J = 8.8 Hz, 2 H), 4.42 (s, 2 H), 4.12 (m, 2
H), 3.79 (s, 3 H), 2.82 (d, J = 2.8 Hz, 2 H), 2.22 (dd, J = 2.8,
2.8 Hz, 1 H), 1.24 (m, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ
= 172.0 (2ϫ), 167.3, 159.3, 130.1 (2ϫ), 129.4, 128.6, 114.2 (2ϫ),
62.1, 55.2, 41.4, 32.1, 27.6, 14.0 ppm. HRMS (ESI): calcd. for
(EtOAc/hexane = 30:70). IR (film): ν = 3376, 2922, 2855, 1645,
˜
1
1578, 1133, 767 cm–1. H NMR (400 MHz, CDCl3): δ = 7.22 (d, J
= 9.2 Hz, 2 H), 6.94 (d, J = 9.2 Hz, 2 H), 3.79 (s, 3 H), 2.86 (d, J
= 8.0 Hz, 2 H), 2.59 (dd, J = 8.0, 8.0 Hz, 1 H), 1.42 (s, 9 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 171.0, 166.0, 159.4, 128.3, 127.9
(2ϫ), 124.2, 114.4 (2ϫ), 83.3, 55.4, 32.0, 27.9 (3ϫ), 26.5 (2ϫ) ppm.
C16H18NO5 [M + H]+ 304.1185; found 304.1188.
+
(1R*,5S*,6s*)-2,4-Dioxo-3-phenyl-3-azabicyclo[3.1.0]hexane-6-
carboxylic Acid (20A): To a stirred solution of ethyl ester 13
(100.0 mg, 0.386 mmol) in MeOH (0.808 mL) at room temp. was
added a solution of NaOH (95.6 mg, 2.39 mmol) in H2O
(0.400 mL). After 40 min, EtOAc (2 mL) and hydrochloric acid
(1 m solution, 2 mL) were added. The organic layer was separated,
and the aqueous layer was extracted with EtOAc (1.5 mL). The
combined organic extracts were concentrated under reduced pres-
sure to give the crude carboxylic acid 20A (67.7 mg, 76%) as a
colorless solid, which was sufficiently pure for characterization; Rf
HRMS (ESI): calcd. for C17H20NO5 [M + H]+ 318.1341; found
+
318.1336.
tert-Butyl (1R*,5S*,6s*)-3-(4-Nitrophenyl)-2,4-dioxo-3-azabicyclo-
[3.1.0]hexane-6-carboxylate (16): According to the same procedure
for the synthesis of 12, N-(4-nitrophenyl)maleimide (10, 279.0 mg,
1.28 mmol) and ylide 11 (559.9 mg, 2.56 mmol) gave cis-cyclopro-
pane 16 (200.7 mg, 47%) as a colorless oil; Rf = 0.67 (acetone/
CHCl , 10:90). IR (film): ν = 3283, 2917, 2850, 1639, 1567, 1540,
˜
3
1416, 1133, 1094, 772 cm–1. 1H NMR (400 MHz, CDCl3): δ = 8.29
(d, J = 8.0 Hz, 2 H), 7.58 (d, J = 8.0 Hz, 2 H), 2.94 (d, J = 8.0 Hz,
2 H), 2.65 (dd, J = 8.0, 8.0 Hz, 1 H), 1.40 (s, 9 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 169.8 (2ϫ), 166.0, 162.6, 137.2, 128.6 (2ϫ),
124.2 (2ϫ), 83.8, 32.8, 27.9 (3ϫ), 26.8 (2ϫ) ppm. HRMS (ESI):
= 0.42 (EtOAc/MeOH/AcOH, 70:25:5). IR (film): ν = 3311, 2556,
˜
1711, 1589, 1495, 1200, 1011 cm–1. 1H NMR (400 MHz, D2O): δ
= 7.30–7.26 (m, 4 H), 7.12–7.11 (m, 1 H), 2.49 (dd, J = 9.6, 9.6 Hz,
1 H), 2.30 (d, J = 9.6 Hz, 2 H) ppm. 13C NMR (100 MHz,
CD3OD): δ = 170.5 (2ϫ), 166.6, 137.4, 127.8 (2ϫ), 123.6, 119.4
+
calcd. for C16H17N2O6 [M + H]+ 333.1087; found 333.1092.
–
(2ϫ), 27.0, 24.9 (2ϫ) ppm. HRMS (ESI): calcd. for C12H8NO4
Ethyl
(1R*,5S*,6s*)-3-(4-Nitrophenyl)-2,4-dioxo-3-azabicyclo-
[M – H]– 230.0453; found 230.0458.
[3.1.0]hexane-6-carboxylate (17) and Ethyl (1R*,5S*,6r*)-3-(4-Ni-
trophenyl)-2,4-dioxo-3-azabicyclo[3.1.0]hexane-6-carboxylate (18):
To a stirred solution of ylide 3 (270.0 mg, 1.24 mmol) in 1,2-dichlo-
roethane (37 mL) at 65 °C was added N-(4-nitrophenyl)maleimide
(10, 349.1 mg, 1.24 mmol). After 1 h, the mixture was concentrated
under reduced pressure. The residue was purified by column
chromatography on silica gel (7.5 g, EtOAc/hexane, 80:20) to give
cis-cyclopropane 17 (182.4 mg, 48%) and trans-cyclopropane 18
(1R*,5S*,6s*)-3-(4-Methoxyphenyl)-2,4-dioxo-3-azabicyclo-
[3.1.0]hexane-6-carboxylic Acid (21A): To a stirred solution of ethyl
ester 14 (4.5 mg, 0.015 mmol) in MeOH (0.175 mL) and H2O
(0.175 mL) at –10 °C was added a solution of LiOH (6.3 mg,
0.031 mmol) in MeOH (0.05 mL) and H2O (0.05 mL). After
25 min, the mixture was diluted with CHCl3 (0.5 mL), and the re-
sulting solution was extracted with H2O (3ϫ0.5 mL). The com-
8
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
Total Synthesis of (Ϯ)-Dysibetaine CPa and Analogs
bined aqueous layers were acidified with hydrochloric acid (1 m,
solution, 1 mL), and the resulting solution was extracted with
EtOAc (5ϫ4 mL). The combined organic extracts were dried with
Na2SO4 and concentrated under reduced pressure to give crude
carboxylic acid 21A (3.7 mg, 93%) as a colorless solid, which was
sufficiently pure for characterization; Rf = 0.39 (EtOAc/MeOH/
ous layer was separated and acidified with hydrochloric acid (1 m
solution, 0.5 mL). The resulting solution was extracted with EtOAc
(0.4 mL), and the organic layer was dried with Na2SO4 and concen-
trated under reduced pressure to give the crude dicarboxylic acid
25C (2.1 mg, 60%), which was sufficiently pure for characteriza-
tion; R = 0.73 (EtOAc/MeOH/AcOH, 60:35:5). IR (film): ν =
˜
f
AcOH, 60:35:5). IR (film): ν = 3022, 2547, 1710, 1505, 1245 cm–1. 3020, 1523, 1424, 1044, 926 cm–1. H NMR (400 MHz, D2O): δ =
1
˜
1H NMR (400 MHz, CD3OD): δ = 7.41 (d, J = 8.6 Hz, 2 H), 6.85
7.14 (d, J = 8.8 Hz, 2 H), 6.85 (d, J = 8.8 Hz, 2 H), 4.19 (s, 2 H),
(d, J = 8.6 Hz, 2 H), 3.75 (s, 3 H), 2.56–2.47 (m, 3 H) ppm. 13C 3.69 (s, 3 H), 2.45–2.38 (m, 2 H), 2.32 (m, 1 H) ppm. 13C NMR
NMR (100 MHz, CD3OD): δ = 173.8 (2ϫ), 169.5, 159.2, 133.3, (100 MHz, D2O): δ = 176.0, 173.5, 169.6, 158.0, 134.0, 130.3 (2ϫ),
124.2 (2ϫ), 115.9 (2ϫ), 62.5, 29.7, 28.1 (2ϫ) ppm. HRMS (ESI):
115.6 (2ϫ), 55.2, 42.6, 30.1, 28.7, 27.0 ppm. HRMS (ESI): calcd.
calcd. for C13H10NO5 [M – H]– 260.0559; found 260.0562.
for C14H14NO6 [M – H]– 292.0821; found 292.0822.
–
–
(1R*,2S*,3S*)-2-(tert-Butoxycarbonyl)-3-[(4-nitrophenyl)carb-
amoyl]cyclopropanecarboxylic Acid (22B): According to the same
procedure for the synthesis of 21A, N-(4-nitrophenyl)imide 16
(15.0 mg, 0.0451 mmol) at 0 °C gave carboxylic acid 22B (12.2 mg,
77%) as a colorless oil; Rf = 0.39 (EtOAc/MeOH/AcOH, 65:30:5).
Diethyl (1R*,2S*,3r*)-3-[(tert-Butoxycarbonyl)(4-nitrophenyl)-
carbamoyl]cyclopropane-1,2-dicarboxylate (26): To a solution of
amide 24B (5.0 mg, 0.014 mmol) in CH2Cl2 (0.2 mL) at 0 °C were
added Boc2 O (0.016 mL, 0.071 mmol), Et3 N (0.010 mL,
0.071 mmol), and DMAP (0.2 mg, 0.007 mmol). After 1 h, the mix-
ture was diluted with CHCl3 (3 mL), and the resulting solution was
washed with saturated aqueous NH4Cl (1 mL) and brine (1 mL),
dried with Na2SO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel (0.8 g,
EtOAc/hexane, 83:17) to give N-Boc imide 26 (6.2 mg, 97%) as a
IR (film): ν = 3278, 2916, 2844, 1540, 1339, 1217, 773, 668 cm–1.
˜
1H NMR (400 MHz, D2O): δ = 8.14 (d, J = 9.2 Hz, 2 H), 7.59 (d,
J = 9.2 Hz, 2 H), 2.43 (dd, J = 9.6, 9.2 Hz, 1 H), 2.32 (dd, J = 9.6,
9.2 Hz, 1 H), 2.13 (dd, J = 9.6, 9.2 Hz, 1 H), 1.10 (s, 9 H) ppm.
13C NMR (100 MHz, D2O): δ = 174.2, 170.7, 169.8, 143.6, 143.3,
125.2 (2ϫ), 119.7 (2ϫ), 83.5, 30.3, 28.7, 27.0 (3ϫ), 24.3 ppm.
yellow oil; R = 0.49 (EtOAc/hexane, 35:65). IR (film): ν = 2981,
˜
f
HRMS (ESI): calcd. for C16H17N2O7 [M – H]– 349.1036; found
–
1751, 1596, 1525, 1349, 1300, 1154 cm–1 1H NMR (400 MHz,
.
349.1039.
CDCl3): δ = 8.23 (d, J = 9.2 Hz, 2 H), 7.41 (d, J = 9.2 Hz, 2 H),
4.22–4.14 (m, 4 H), 3.10 (dd, J = 9.6 Hz, 1 H), 2.46 (d, J = 9.6 Hz,
2 H), 1.34 (s, 9 H), 1.25 (t, J = 7.2 Hz, 6 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 168.3, 167.9 (2ϫ), 151.5, 147.0, 144.5,
129.7 (2ϫ), 124.2 (2ϫ), 84.0, 61.4 (2ϫ), 30.2, 27.7 (3ϫ), 26.2 (2ϫ),
1-tert-Butyl 2-Methyl (1S*,2R*,3S*)-3-[(4-Nitrophenyl)carbamoyl]-
cyclopropane-1,2-dicarboxylate (23B): A solution of N-(4-ni-
trophenyl)imide 16 (10.0 mg, 0.0301 mmol) in MeOH (1.0 mL) was
heated to 100 °C in a sealed tube. After 12 h, the solution was con-
centrated under reduced pressure, and the residue was purified by
column chromatography on silica gel (2 g, EtOAc/benzene, 10:90)
to give methyl ester 23B (7.2 mg, 66%) as a colorless oil; Rf = 0.52
+
14.1 (2ϫ) ppm. HRMS (ESI): calcd. for C21H27N2O9 [M + H]+
451.1717; found 451.1727.
Triethyl trans-Cyclopropane-1,2,3-tricarboxylate (5): To a stirred
solution of N-Boc imide 26 (3.6 mg, 0.0080 mmol) in EtOH
(0.2 mL) at –10 °C was added K2CO3 (27.6 mg, 0.20 mmol). After
stirring at room temp. for 5 h, the mixture was diluted with EtOAc
(2 mL), and the resulting solution was washed with saturated aque-
ous NH4Cl (1 mL) and brine (1 mL), dried with Na2SO4, and con-
centrated under reduced pressure. The residue was purified by col-
umn chromatography on silica gel (0.5 g, EtOAc/hexane, 90:10) to
give triethyl ester 5 (1.7 mg, 85 %) as a colorless oil; Rf = 0.58
(acetone/CHCl , 10:90). IR (film): ν = 3316, 2917, 2850, 1728,
˜
3
1561, 1511, 1339, 1150, 1111, 850, 761 cm–1. H NMR (400 MHz,
1
CDCl3): δ = 10.5 (br., 1 H), 8.30 (d, J = 8.0 Hz, 2 H), 7.75 (d, J =
8.0 Hz, 2 H), 3.73 (s, 3 H), 2.45–2.38 (m, 3 H), 1.40 (s, 9 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 170.0, 168.0, 164.9, 144.1, 143.3,
125.0 (2ϫ), 119.2 (2ϫ), 83.4, 52.8, 28.9, 27.8 (3ϫ), 26.2, 25.0 ppm.
HRMS (ESI): calcd. for C17H21N2O7 [M + H]+ 365.1349; found
+
365.1358.
(EtOAc/hexane, 30:70). IR (film): ν = 2984, 1733, 1447, 1369, 1338,
˜
Diethyl (1R*,2S*,3r*)-3-[(4-Nitrophenyl)carbamoyl]cyclopropane-
1,2-dicarboxylate (24B): A solution of N-(4-nitrophenyl)imide 17
(40.5 mg, 0.133 mmol) and Et3N (0.090 mL) in EtOH (3.0 mL) was
heated in a microwave oven (200 W) for 40 min. The mixture was
diluted with CHCl3 (10 mL), and the resulting solution was washed
with saturated aqueous NH4Cl (3 mL) and brine (3 mL), dried with
Na2SO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel (1 g, EtOAc/hex-
ane, 60:40) to give diester 24B (14.8 mg, 32%) as a yellow oil; Rf
1
1183 cm–1. H NMR (400 MHz, CDCl3): δ = 4.14–4.07 (m, 6 H),
2.70 (dd, J = 5.6, 5.6 Hz, 1 H), 2.47 (d, J = 5.6 Hz, 2 H), 1.24–1.18
(m, 9 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 170.0, 167.5 (2ϫ),
61.5, 61.4 (2ϫ), 28.3 (2ϫ), 25.5, 14.0 (3ϫ) ppm. HRMS (ESI):
+
calcd. for C12H19O6 [M + H]+ 259.1182; found 259.1184. The
spectroscopic data for 5 were identical with those reported by Ag-
garwal et al.[20]
(1R*,2R*,5S*,6R*)-tert-Butyl 2-Hydroxy-3-(4-nitrophenyl)-4-oxo-
3-azabicyclo[3.1.0]hexane-6-carboxylate (27): To a stirred solution
of amido ester 23B (5.0 mg, 0.014 mmol) in THF (0.200 mL) at
–78 °C was added LiAlH4 (0.001 mg, 0.03 mmol). After 3 h, MeOH
(0.03 mL) and saturated aqueous potassium sodium tartrate (Ro-
chelle salt, 0.02 mL) were slowly added, and the mixture was fil-
tered through a pad of Celite. The filtrate was concentrated under
reduced pressure, and the residue was purified by column
chromatography on silica gel (0.5 g, acetone/CHCl3, 10:90) to give
aminal 27 (2.0 mg, 43%) as a colorless oil; Rf = 0.16 (acetone/
= 0.36 (EtOAc/hexane, 50:50). IR (film): ν = 3338, 2987, 1733,
˜
1597, 1511, 1342, 1302, 1189 cm–1. 1H NMR (400 MHz, CDCl3):
δ = 10.50 (s, 1 H), 8.16 (d, J = 9.2 Hz, 2 H), 7.74 (d, J = 9.2 Hz, 2
H), 4.21–4.12 (m, 4 H), 2.48–2.45 (m, 3 H), 1.21 (t, J = 6.8 Hz, 6
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 169.2 (2ϫ), 164.8,
144.0, 143.0, 125.0 (2ϫ), 119.2 (2ϫ), 61.2 (2ϫ), 29.0, 25.3 (2ϫ),
14.0 (2ϫ) ppm. HRMS (ESI): calcd. for C16H19N2O7 [M + H]+
+
351.1192; found 351.1187.
(1R*,2R*)-3-[(4-Methoxybenzyl)carbamoyl]cyclopropane-1,2-di-
carboxylic Acid (25C): To a stirred solution of imido ester 19
(3.7 mg, 0.012 mmol) in MeOH (0.100 mL) at 0 °C was added a
solution of NaOH (3.0 mg, 0.076 mmol) in H2O (0.012 mL). After
25 min, H2O (0.4 mL) and EtOAc (0.4 mL) were added. The aque-
CHCl , 10:90). IR (film): ν = 3344, 2917, 2844, 1722, 1594, 1516,
˜
3
1340, 1150, 773 cm–1. H NMR (400 MHz, CDCl3): δ = 8.19 (d, J
1
= 8.8 Hz, 2 H), 7.85 (d, J = 8.8 Hz, 2 H), 5.71 (s, 1 H), 3.04 (br.,
1 H), 2.55 (dd, J = 8.4, 5.8 Hz, 1 H), 2.34 (dd, J = 8.2, 5.8 Hz, 1
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
9

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
M. Oikawa, S. Sasaki, M. Sakai, Y. Ishikawa, R. Sakai
FULL PAPER
H), 2.27 (dd, J = 8.4, 8.2 Hz, 1 H), 1.27 (s, 9 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 170.0, 166.3, 144.2, 143.0, 124.6 (2ϫ),
121.2 (2ϫ), 82.7, 82.6, 77.2, 27.8, 27.3 (3ϫ), 26.3 ppm. HRMS
(ESI): calcd. for C16H19N2O6+ [M + H]+ 335.1243; found 335.1249.
(ESI): calcd. for C20H31N2O6Si+ [M + H]+ 423.1951; found
423.1942.
Ethyl (1S*,2S*,3R*)-2-[(tert-Butoxycarbonyl)(4-nitrophenyl)-
carbamoyl]-3-{[(triethylsilyl)oxy]methyl}cyclopropanecarboxylate
tert-Butyl (1R*,2R*,3S*)-2-(Hydroxymethyl)-3-[(4-nitrophenyl)- (31): To a stirred solution of amide 30 (277.5 mg, 0.660 mmol) in
carbamoyl]cyclopropanecarboxylate (28): To a stirred solution of N-
(4-nitrophenyl)imide 16 (3.4 mg, 0.010 mmol) in THF (0.200 mL)
CH2 Cl2 (6.6 mL) at 0 °C were added Boc2 O (0.300 mL,
1.31 mmol), Et3N (0.182 mL, 1.31 mmol), and DMAP (40.1 mg,
and MeOH (0.100 mL) at 0 °C was added NaBH4 (0.0012 mg, 0.33 mmol). After stirring at room temp. for 30 min, the mixture
0.031 mmol). After 50 min, the mixture was diluted with CHCl3
(2 mL), and the resulting solution was washed with saturated aque-
ous NH4Cl (1 mL), H2O (1 mL), and then brine (1 mL). The or-
ganic layer was dried with Na2SO4 and concentrated under reduced
pressure. The residue was purified by column chromatography on
silica gel (0.5 g, EtOAc/hexane, 70:30) to give alcohol 28 (2.6 mg,
was diluted with CHCl3 (20 mL), and the resulting solution was
washed with saturated aqueous NH4Cl (5 mL) and brine (5 mL),
dried with Na2SO4, and concentrated under reduced pressure. The
residue was purified by column chromatography on silica gel (10 g,
EtOAc/hexane, 20:80) to give N-Boc imide 31 (294.1 mg, 86%) as
a yellow oil; R = 0.55 (EtOAc/hexane, 20:80). IR (film): ν = 2956,
˜
f
76%) as a colorless oil; Rf = 0.23 (EtOAc/hexane, 60:40). IR (film): 2876, 1744, 1693, 1526, 1458, 1369, 1347, 1256, 1153 cm–1
ν = 3295, 2921, 2849, 1556, 1341, 1292, 1253, 1110, 1011, 886, NMR (400 MHz, CDCl3): δ = 8.24 (d, J = 8.8 Hz, 2 H), 7.31 (d,
772 cm–1. 1H NMR (400 MHz, CDCl3): δ = 8.95 (br., 1 H), 8.19 J = 8.8 Hz, 2 H), 4.13 (q, J = 7.2 Hz, 2 H), 3.92 (dd, J = 11.2,
(d, J = 8.0 Hz, 2 H), 7.70 (d, J = 8.0 Hz, 2 H), 4.11–4.06 (m, 2 H), 6.0 Hz, 1 H), 3.54 (dd, J = 11.2, 9.2 Hz, 1 H), 3.32 (dd, J = 10.4,
.
1H
˜
2.80 (br., 1 H), 2.27 (dd, J = 9.2, 8.8 Hz, 1 H), 2.17 (dd, J = 9.2, 4.8 Hz, 1 H), 2.42 (dd, J = 6.0, 4.8 Hz, 1 H), 2.22 (m, 1 H), 1.41
8.8 Hz, 1 H), 1.92–1.88 (m, 1 H), 1.53 (s, 9 H) ppm. 13C NMR (s, 9 H), 1.25 (t, J = 7.2 Hz, 3 H), 0.94 (t, J = 8.0 Hz, 9 H), 0.59
(100 MHz, CDCl3): δ = 168.9, 166.5, 143.8, 143.4, 125.1 (2ϫ),
(q, J = 8.0 Hz, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 171.4,
119.0 (2ϫ), 82.5, 57.9, 29.7, 28.0 (3ϫ), 25.0, 24.9 ppm. HRMS 170.5, 151.3, 147.0, 144.7, 129.4 (2ϫ), 124.3 (2ϫ), 84.6, 61.1, 59.0,
(ESI): calcd. for C16H21N2O6+ [M + H]+ 337.1400; found 337.1404.
32.3, 29.6, 27.7 (3ϫ), 26.5, 14.1, 6.7 (3ϫ), 4.3 (3ϫ) ppm. HRMS
(ESI): calcd. for C25H39N2O8Si+ [M + H]+ 523.2476; found
523.2473.
Ethyl (1S*,2R*,3S*)-2-(Hydroxymethyl)-3-[(4-nitrophenyl)carb-
amoyl]cyclopropanecarboxylate (29): To a stirred solution of N-(4-
nitrophenyl)imide 18 (730.0 mg, 2.38 mmol) in THF (23.8 mL) and Diethyl (1S*,2S*)-3-(Hydroxymethyl)cyclopropane-1,2-dicarboxyl-
MeOH (2.0 mL) at –10 °C was added NaBH4 (270.4 mg,
7.15 mmol). After 10 min, the mixture was diluted with CHCl3
(50 mL), and the resulting solution was washed with saturated
aqueous NH4Cl (20 mL) and brine (15 mL), dried with Na2SO4,
and concentrated under reduced pressure. The residue was purified
by column chromatography on silica gel (15 g, EtOAc/hexane,
50:50) to give alcohol 29 (695.6 mg, 95%) as a yellow oil; Rf = 0.44
ate (32): To a stirred solution of N-Boc imide 31 (1.79 g,
3.42 mmol) in EtOH (100 mL) at room temp. was added K2CO3
(13.8 g, 100 mmol). After 20 min, the mixture was filtered through
a pad of silica gel (20 g, CHCl3), and the filtrate was concentrated
under reduced pressure to give the crude siloxy diester (1.72 g) as
a yellow oil, which was used without purification in the next reac-
tion. To a stirred solution of the crude siloxy diester (1.72 g) in
THF (34.2 mL) at room temp. were added AcOH (0.800 mL,
14.7 mmol) and TBAF (1.0 m in THF, 10.26 mL, 10.26 mmol). Af-
ter 1 h, the mixture was diluted with CHCl3 (100 mL), and the
resulting solution was washed with saturated aqueous NaHCO3
(30 mL) and brine (30 mL), dried with Na2SO4, and concentrated
under reduced pressure. The residue was purified by column
(EtOAc/hexane, 50:50). IR (film): ν = 3334, 3090, 2894, 1731, 1699,
˜
1506, 1369, 1341, 1168 cm–1. 1H NMR (400 MHz, CDCl3): δ =
9.25 (s, 1 H), 8.07 (d, J = 9.2 Hz, 2 H), 7.63 (d, J = 9.2 Hz, 2 H),
4.16 (q, J = 7.2 Hz, 2 H), 4.08 (dd, J = 5.2, 4.4 Hz, 1 H), 3.83 (dd,
J = 9.2, 9.2 Hz, 1 H), 2.48 (dd, J = 10.0, 5.2 Hz, 1 H), 2.38 (dd, J
= 10.0, 4.4 Hz, 1 H), 2.17 (m, 1 H), 1.26 (t, J = 7.2 Hz, 3 H) ppm.
13C NMR (100 MHz, CD3OD): δ = 171.9, 168.0, 144.7, 143.0, chromatography on silica gel (20 g, EtOAc/hexane, 40:60) to give
124.3 (2ϫ), 118.8 (2ϫ), 60.9, 57.6, 30.7, 28.4, 25.1, 13.1 ppm.
alcohol 32 (546.7 mg, 74% for 2 steps from 31) as a colorless oil;
+
HRMS (ESI): calcd. for C14H17N2O6 [M + H]+ 309.1087; found
R = 0.36 (EtOAc/hexane, 30:70). IR (film): ν = 3441, 2982, 1723,
˜
f
1
309.1075.
1372, 1179 cm–1. H NMR (400 MHz, CDCl3): δ = 4.12 (m, 4 H),
3.91 (dd, J = 12.0, 5.2 Hz, 1 H), 3.77 (dd, J = 12.0, 7.6 Hz, 1 H),
2.29 (d, J = 7.6 Hz, 2 H), 1.84 (m, 1 H), 1.22 (t, J = 7.2 Hz, 6
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 169.3 (2ϫ), 61.3 (2ϫ),
57.5, 25.1, 24.2 (2ϫ), 14.1 (2ϫ) ppm. HRMS (ESI): calcd. for
Ethyl (1S*,2S*,3R*)-2-[(4-Nitrophenyl)carbamoyl]-3-{[(triethyl-
silyl)oxy]methyl}cyclopropanecarboxylate (30): To a stirred solution
of alcohol 29 (1.26 g, 4.09 mmol) in CH2Cl2 (40.0 mL) at 0 °C were
added TESCl (1.40 mL, 8.17 mmol), Et3N (1.13 mL, 8.17 mmol),
and DMAP (49.8 mg, 0.41 mmol). After 20 min, the mixture was
diluted with CHCl3 (80 mL), and the resulting solution was washed
with saturated aqueous NH4Cl (20 mL) and brine (20 mL), dried
with Na2SO4, and concentrated under reduced pressure. The resi-
due was purified by column chromatography on silica gel (15 g,
EtOAc/hexane, 70:30) to give TES ether 30 (1.43 g, 83%) as a col-
C10H17O5 [M + H]+ 217.1076; found 217.1077.
+
Diethyl (1R*,2R*)-3-(Bromomethyl)cyclopropane-1,2-dicarboxylate
(33): To a stirred solution of alcohol 32 (10.2 mg, 0.047 mmol) in
CH2Cl2 (2.1 mL) at room temp. were added PPh3 (24.7 mg,
0.094 mmol) and CBr4 (46.9 mg, 0.14 mmol). After 1 h, the mixture
was concentrated under reduced pressure. The residue was purified
by column chromatography on silica gel (2 g, EtOAc/hexane, 30:70)
orless oil; R = 0.53 (EtOAc/hexane, 50:50). IR (film): ν = 3334,
˜
f
3090, 2894, 1731, 1699, 1506, 1369, 1341, 1168 cm–1 1H NMR to give bromide 33 (11.2 mg, 85%) as a colorless oil; Rf = 0.49
.
(400 MHz, CDCl3): δ = 8.46 (s, 1 H), 8.17 (d, J = 9.2 Hz, 2 H),
7.67 (d, J = 9.2 Hz, 2 H), 4.16 (q, J = 7.2 Hz, 2 H), 4.04 (dd, J =
11.2, 5.6 Hz, 1 H), 3.67 (dd, J = 11.2, 9.2 Hz, 1 H), 2.38 (d, J =
7.6 Hz, 2 H), 2.15 (m, 1 H), 1.26 (t, J = 7.2 Hz, 3 H), 0.86 (t, J =
8.0 Hz, 9 H), 0.54 (q, J = 8.0 Hz, 6 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 172.4, 166.9, 143.9, 143.3, 125.0 (2ϫ), 118.8 (2ϫ),
61.6, 59.1, 31.3, 29.5, 25.1, 14.1, 6.6 (3ϫ), 4.1 (3ϫ) ppm. HRMS
(EtOAc/hexane, 15:85). IR (film): ν = 2981, 1722, 1314, 1205,
˜
1
1153 cm–1. H NMR (400 MHz, CDCl3): δ = 4.21–4.11 (m, 4 H),
3.73 (m, 1 H), 3.55 (m, 1 H), 2.44 (dd, J = 8.4, 5.6 Hz, 1 H),
2.33–2.28 (m, 2 H), 1.30–1.23 (m, 6 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 170.4, 169.2, 61.5, 61.4, 30.4, 30.0, 28.6, 28.5, 14.2,
14.1 ppm. HRMS (ESI): calcd. for C10H16O4Br+ [M + H]+
279.0232; found 279.0238.
10
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
Total Synthesis of (Ϯ)-Dysibetaine CPa and Analogs
Diethyl (1S*,2S*)-3-[(Dimethylamino)methyl]cyclopropane-1,2-di-
carboxylate (34): A solution of bromide 33 (22.4 mg, 0.080 mmol)
and dimethylamine (2.0 m in THF, 0.400 mL, 0.80 mmol) in toluene
(0.4 mL) was heated to 125 °C in a sealed tube. After 3 h, the mix-
ture was concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel (1 g, MeOH/
CHCl3, 10:90) to give tertiary amine 34 (19.5 mg, 100%) as a yel-
nal 37 (41.6 mg, 33%) as yellow oils. Data for 3-epi-alcohol 36: Rf
= 0.21 (EtOAc/hexane, 60:40). IR (film): ν = 3518, 3265, 2926,
˜
1716, 1653, 1507, 1378, 1341, 1174 cm–1. 1H NMR (400 MHz,
CDCl3): δ = 9.07 (br. s, 1 H), 8.18 (d, J = 9.2 Hz, 2 H), 7.70 (d, J
= 9.2 Hz, 2 H), 4.16 (q, J = 7.2 Hz, 2 H), 4.14–4.04 (m, 2 H), 2.35
(dd, J = 8.8, 8.8 Hz, 1 H), 2.24 (dd, J = 8.8, 8.8 Hz, 1 H), 1.94 (m,
1 H), 1.23 (t, J = 7.2 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3):
low oil; R = 0.58 (MeOH/CHCl , 50:50). IR (film): ν = 3439, 2981, δ = 169.8, 166.3, 143.7, 143.5, 125.1 (2ϫ), 119.2 (2ϫ), 61.6, 57.7,
˜
f
3
+
1722, 1370, 1203, 1176 cm–1. 1H NMR (400 MHz, CDCl3): δ =
28.2, 25.1, 23.6, 14.1 ppm. HRMS (ESI): calcd. for C14H17N2O6
4.16–4.09 (m, 4 H), 2.89–2.81 (m, 2 H), 2.42 (s, 6 H), 2.36 (dd, J
[M + H]+ 309.1087; found 309.1081. Data for 3-epi-aminal 37: Rf
= 9.2, 5.2 Hz, 1 H), 2.16 (dd, J = 5.2, 5.2 Hz 1 H), 2.09–2.05 (m, = 0.34 (EtOAc/hexane, 60:40). IR (film): ν = 3372, 2983, 1732,
˜
1 H) 1.26–1.21 (m, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
170.5, 169.9, 61.4 (2ϫ), 54.5, 44.0 (2ϫ), 26.9, 26.3, 24.9, 14.1,
1653, 1519, 1382, 1341, 1191 cm–1. 1H NMR (400 MHz, CDCl3):
δ = 8.12 (d, J = 9.2 Hz, 2 H), 7.79 (d, J = 9.2 Hz, 2 H), 5.59 (d, J
= 1.6 Hz, 1 H), 4.13 (br. s, 1 H), 3.99 (q, J = 7.2 Hz, 2 H), 2.51
(ddd, J = 8.4, 6.0, 1.6 Hz, 1 H), 2.38 (dd, J = 8.4, 6.0 Hz, 1 H),
2.26 (dd, J = 8.4, 8.4 Hz, 1 H), 1.10 (t, J = 7.2 Hz, 3 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 170.3, 167.6, 144.3, 143.0, 124.5
(2ϫ), 121.3 (2ϫ), 83.0, 61.7, 27.0, 26.8, 26.1, 14.0 ppm. HRMS
(ESI): calcd. for C14H15N2O6+ [M + H]+ 307.0930; found 307.0932.
+
14.1 ppm. HRMS (ESI): calcd. for C12H22NO4 [M + H]+
244.1549; found 244.1543.
1-[(2S*,3S*)-2,3-Bis(ethoxycarbonyl)cyclopropyl]-N,N,N-tri-
methylmethanaminium Iodide (35): A suspension of tertiary amine
34 (9.8 mg, 0.040 mmol), MeI (0.150 mL, 3.62 mmol), and
NaHCO3 (10.1 mg, 0.121 mmol) in toluene (0.15 mL) was heated
to 125 °C in a sealed tube. After 7 h, the mixture was concentrated
under reduced pressure. To the residue was added CHCl3 (2 mL),
and the insoluble materials were removed by filtration. The filtrate
was concentrated under reduced pressure to give the crude quater-
nary ammonium iodide 35 (14.5 mg) as a brown solid, which was
used without purification in the next reaction; Rf = 0.75 (BuOH/
Ethyl
(1R*,2S*,3R*)-2-[(4-Nitrophenyl)carbamoyl]-3-{[(triethyl-
silyl)oxy]methyl}cyclopropanecarboxylate (38): To a stirred solution
of 3-epi-alcohol 36 (10.0 mg, 0.032 mmol) in CH2Cl2 (0.200 mL) at
0 °C were added 2,6-lutidine (0.016 mL, 0.14 mmol) and TESOTf
(0.015 mL, 0.064 mmol). After 20 min, Et3N (0.030 mL) was added
at 0 °C, and the mixture was diluted with CHCl3 (5 mL). The re-
sulting solution was washed with saturated aqueous NH4Cl (2 mL)
and brine (2 mL), dried with Na2SO4, and concentrated under re-
duced pressure. The residue was purified by column chromatog-
raphy on silica gel (4 g, EtOAc/hexane, 40:60) to give 3-epi-TES
ether 38 (10.7 mg, 84%) as a yellow oil; Rf = 0.79 (EtOAc/hexane,
AcOH/H O, 33:33:33). IR (KBr): ν = 3441, 2981, 1716, 1305, 1222,
˜
2
1185 cm–1. 1H NMR (400 MHz, D2O): δ = 4.26–4.10 (m, 4 H), 4.01
(dd, J = 13.6, 6.4 Hz, 1 H), 3.89 (dd, J = 13.6, 8.0 Hz, 1 H), 3.48
(s, 9 H), 2.55 (dd, J = 8.8, 5.2 Hz, 1 H), 2.31 (dd, J = 5.2, 5.2 Hz,
1 H), 2.15 (m, 1 H), 1.29 (t, J = 7.2 Hz, 6 H) ppm. 13C NMR
(100 MHz, D2O): δ = 169.6, 169.2, 62.5, 62.4 (2ϫ), 54.1 (3ϫ), 26.8,
60:40). IR (film): ν = 3308, 2955, 1733, 1649, 1507, 1410, 1378,
˜
+
25.9, 20.8, 14.2 (2ϫ) ppm. HRMS (ESI): calcd. for C13H24NO4
1341, 1260, 1162 cm–1. H NMR (400 MHz, CDCl3): δ = 9.91 (s,
1
[M – I]+ 258.1705; found 258.1690.
1 H), 8.10 (d, J = 9.2 Hz, 2 H), 7.65 (d, J = 9.2 Hz, 2 H), 4.22–
4.01 (m, 2 H), 4.09 (q, J = 7.2 Hz, 2 H), 2.35 (dd, J = 9.2, 9.2 Hz,
1 H), 2.15 (dd, J = 9.2, 9.2 Hz, 1 H), 1.80 (m, 1 H), 1.16 (t, J =
7.2 Hz, 3 H), 0.92 (t, J = 8.0 Hz, 9 H), 0.61 (q, J = 8.0 Hz, 6
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 169.7, 166.0, 144.2,
143.0, 124.8 (2ϫ), 118.9 (2ϫ), 61.1, 57.7, 28.6, 25.5, 22.8, 13.9, 6.5
(3ϫ), 4.3 (3ϫ) ppm. HRMS (ESI): calcd. for C20H31N2O6Si+ [M +
H]+ 423.1951; found 423.1945.
(؎)-Dysibetaine CPa (1): A suspension of crude quaternary ammo-
nium iodide 35 (3.2 mg, 0.01 mmol), in hydrochloric acid (6 m solu-
tion, 1.0 mL) was heated to 90 °C with stirring. After 6 h, the mix-
ture was concentrated under reduced pressure. The residue was
purified by column chromatography on reversed-phase silica gel
(1 g, MeOH/H2O, 10:90) to give dysibetaine CPa (1, 1.3 mg, 74%
for 2 steps from 34) as a yellow solid; Rf = 0.28 (BuOH/AcOH/
H O, 33:33:33). IR (KBr): ν = 3410, 3013, 2609, 1733, 1472, 1233,
˜
2
Ethyl
carbamoyl]-3-{[(triethylsilyl)oxy]methyl}cyclopropanecarboxylate
(39): To stirred solution of 3-epi-amide 38 (150.0 mg,
(1R*,2S*,3R*)-2-[(tert-Butoxycarbonyl)(4-nitrophenyl)-
1184 cm–1. H NMR (400 MHz, D2O): δ = 3.68–3.57 (m, 2 H, 1-
1
H2), 3.10 [s, 9 H, 1-N(CH3)3], 2.44 (dd, J = 9.2, 5.2 Hz, 1 H, 3-H
or 4-H), 2.26 (dd, J = 5.2, 5.2 Hz, 1 H, 3-H or 4-H), 2.17 (m, 1 H,
2-H) ppm. 13C NMR (100 MHz, D2O): δ = 175.0 (C-5 or C-6),
174.0 (C-5 or C-6), 63.7 (C-1), 53.9 [3ϫ, 1-N(CH3)3], 27.8 (C-3 or
C-4), 27.7 (C-3 or C-4), 22.0 (C-2) ppm. HRMS (ESI): calcd. for
a
0.354 mmol) in CH2Cl2 (10.0 mL) at 0 °C were added Boc2O
(0.162 mL, 0.71 mmol), Et3N (0.098 mL, 0.71 mmol), and DMAP
(21.6 mg, 0.177 mmol). After stirring at room temp. for 50 min, the
mixture was diluted with CHCl3 (15 mL), and the resulting solution
was washed with saturated aqueous NH4Cl (7 mL) and brine
(7 mL), dried with Na2SO4, and concentrated under reduced pres-
sure. The residue was purified by column chromatography on silica
gel (10 g, EtOAc/hexane, 80:20) to give 3-epi-N-Boc imide 39
(180.7 mg, 97%) as a yellow oil; Rf = 0.75 (EtOAc/hexane, 30:70).
C9H16NO4 [M + H]+ 202.1079; found 202.1072. The chromato-
+
graphic data as well as the 1H and 13C NMR spectroscopic data
were identical with those for the natural product reported by Sakai
et al.[5]
Ethyl (1R*,2R*,3S*)-2-(Hydroxymethyl)-3-[(4-nitrophenyl)carb-
amoyl]cyclopropanecarboxylate (36) and Ethyl (1R*,2R*,5S*,6R*)-
IR (film): ν = 2956, 2876, 1747, 1699, 1526, 1457, 1347, 1325, 1265,
˜
2-Hydroxy-3-(4-nitrophenyl)-4-oxo-3-azabicyclo[3.1.0]hexane-6-carb- 1183 cm–1. H NMR (400 MHz, CDCl3): δ = 8.24 (d, J = 8.8 Hz,
1
oxylate (37): To a stirred solution of 3-epi-imide 17 (124.6 mg,
0.410 mmol) in THF (4.0 mL) and MeOH (2.0 mL) at –10 °C was
2 H), 7.36 (d, J = 8.8 Hz, 2 H), 4.18–4.11 (m, 3 H), 3.86 (dd, J =
11.6, 9.2 Hz, 1 H), 2.86 (dd, J = 8.8, 8.8 Hz, 1 H), 2.33 (dd, J =
added NaBH4 (46.4 mg, 1.23 mmol). After 2 h, the mixture was 8.8, 8.8 Hz, 1 H), 1.97 (m, 1 H), 1.35 (s, 9 H), 1.25 (t, J = 7.2 Hz,
diluted with CHCl3 (10 mL), and the resulting solution was washed
with saturated aqueous NH4Cl (3 mL) and brine (3 mL), dried with
Na2SO4, and concentrated under reduced pressure. The residue was
purified by column chromatography on silica gel (5 g, EtOAc/hex-
ane, 80:20) to give 3-epi-alcohol 36 (70.4 mg, 55%) and 3-epi-ami-
3 H), 0.91 (t, J = 8.0 Hz, 9 H), 0.55 (q, J = 8.0 Hz, 6 H) ppm. 13C
NMR (100 MHz, CDCl3): δ = 170.0, 169.7, 151.3, 147.0, 144.7,
129.6 (2ϫ), 124.2 (2ϫ), 84.0, 60.8, 57.8, 29.0, 28.5, 27.7 (3ϫ), 25.0,
14.2, 6.7 (3ϫ), 4.3 (3ϫ) ppm. HRMS (ESI): calcd. for
C25H39N2O8Si+ [M + H]+ 523.2476; found 523.2478.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
11

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
M. Oikawa, S. Sasaki, M. Sakai, Y. Ishikawa, R. Sakai
FULL PAPER
Diethyl (1R,2S,3r)-3-(Hydroxymethyl)cyclopropane-1,2-dicarboxyl-
ate (40): To a stirred solution of 3-epi-N-Boc imide 39 (26.4 mg,
quaternary ammonium iodide 43 (4.3 mg) as a brown solid, which
was used without purification in the next reaction; Rf = 0.42
0.050 mmol) in EtOH (3.0 mL) at room temp. was added K2CO3 (MeOH/CHCl , 30:70). IR (KBr): ν = 3421, 2976, 1733, 1378,
˜
3
1
(415.0 mg, 3.00 mmol). After 2 h, the mixture was filtered through
a pad of silica gel (10 g, CHCl3), and the filtrate was concentrated
under reduced pressure to give the crude siloxy diester (30.9 mg)
as a yellow oil, which was used without purification in the next
reaction. To a stirred solution of the crude siloxy diester (30.9 mg)
in THF (0.900 mL) at room temp. were added AcOH (0.020 mL,
0.37 mmol) and TBAF (1.0 m in THF, 0.28 mL, 0.28 mmol). After
3 h, the mixture was diluted with CHCl3 (10 mL), and the resulting
solution was washed with saturated aqueous NaHCO3 (4 mL) and
brine (4 mL), dried with Na2SO4, and concentrated under reduced
pressure. The residue was purified by column chromatography on
silica gel (3 g, EtOAc/hexane, 40:60) to give 3-epi-alcohol 40
(9.1 mg, 83% for 2 steps from 39) as a colorless oil; Rf = 0.12
1207, 1182 cm–1. H NMR (400 MHz, D2O): δ = 4.16–4.06 (m, 4
H), 3.86 (d, J = 6.8 Hz, 2 H), 3.10 (s, 9 H), 2.55 (d, J = 8.8 Hz, 2
H), 2.05 (m, 1 H), 1.17 (t, J = 7.2 Hz, 6 H) ppm. 13C NMR
(100 MHz, D2O): δ = 170.2 (2ϫ), 62.7 (2ϫ), 53.0, 48.8 (3ϫ), 23.9
+
(2ϫ), 17.2, 13.2 (2ϫ) ppm. HRMS (ESI): calcd. for C13H24NO4
[M – I]+ 258.1705; found 258.1699.
meso-3-epi-Dysibetaine CPa (44): A suspension of the crude 3-epi-
quaternary ammonium iodide 43 (4.3 mg) in hydrochloric acid (6 m
solution, 1.0 mL) was heated to 90 °C with stirring. After 8.5 h, the
mixture was concentrated under reduced pressure. The residue was
purified by column chromatography on reversed-phase silica gel
(1 g, MeOH/H2O, 10:90) to give DBCPa diastereomer 44 (1.7 mg,
74% for 2 steps from 42) as a yellow solid; Rf = 0.34 (BuOH/
(EtOAc/hexane, 30:70). IR (film): ν = 3341, 2983, 1732, 1378,
˜
AcOH/H O, 33:33:33). IR (KBr): ν = 3436, 2918, 1733, 1559, 1436,
˜
2
1
1179 cm–1. H NMR (400 MHz, CDCl3): δ = 4.17–4.12 (m, 4 H),
1212, 1189 cm–1. 1H NMR (400 MHz, D2O): δ = 3.84 (d, J =
6.8 Hz, 2 H, 1-H2), 3.09 [s, 9 H, 1-N(CH3)3], 2.43 (d, J = 8.8 Hz,
2 H, 3-H and 4-H), 2.01 (m, 1 H, 2-H) ppm. 13C NMR (100 MHz,
D2O): δ = 172.8 (2ϫ, C-5 and C-6), 61.4 (C-1), 52.9 [3ϫ, 1-N-
(CH3)3], 24.6 (2ϫ, C-3 and C-4), 17.2 (C-2) ppm. HRMS (ESI):
3.94 (d, J = 8.0 Hz, 2 H), 2.15 (d, J = 8.0 Hz, 2 H), 1.84 (m, 1 H),
1.22 (t, J = 7.2 Hz, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
169.3 (2ϫ), 61.3 (2ϫ), 57.5, 25.1, 24.2 (2ϫ), 14.1 (2ϫ) ppm. HRMS
(ESI): calcd. for C10H17O5 [M + H]+ 217.1076; found 217.1069.
+
calcd. for C9H16NO4 [M + H]+ 202.1079; found 202.1086.
+
Diethyl (1R,2S,3s)-3-(Bromomethyl)cyclopropane-1,2-dicarboxylate
(41): To
a stirred solution of 3-epi-alcohol 40 (27.7 mg,
(1S*,2S*,3S*)-2-Carboxy-3-[(dimethylammonio)methyl]cyclo-
propanecarboxylate [(؎)-Dysibetaine CPa Tertiary Ammonium An-
alog 45]: A suspension of amino diester 34 (9.8 mg, 0.040 mmol) in
hydrochloric acid (6 m solution, 1.0 mL) was heated to 90 °C with
stirring. After 4.5 h, the mixture was concentrated under reduced
pressure. The residue was purified by column chromatography on
reversed-phase silica gel (1 g, MeOH/H2O, 10:90) to give DBCPa
tertiary ammonium analog 45 (6.6 mg, 88%) as a yellow solid; Rf
0.146 mmol) in CH2Cl2 (2.1 mL) at room temp. were added PPh3
(100.8 mg, 0.384 mmol) and CBr4 (169.9 mg, 0.512 mmol). After
1 h, the mixture was diluted with CHCl3 (10 mL), and the resulting
solution was washed with saturated aqueous NaHCO3 (3 mL) and
brine (3 mL), dried with Na2SO4, and concentrated under reduced
pressure. The residue was purified by column chromatography on
silica gel (2 g, EtOAc/hexane, 40:60) to give 3-epi-bromide 41
(13.1 mg, 38%) as a colorless oil; Rf = 0.61 (EtOAc/hexane =
= 0.43 (BuOH/AcOH/H O, 33:33:33). IR (KBr): ν = 3404, 2966,
˜
2
30:70). IR (film): ν = 2982, 1738, 1378, 1203, 1158 cm–1. 1H NMR
2739, 1717, 1464, 1195 cm–1. 1H NMR (400 MHz, D2O): δ = 3.49–
3.39 (m, 2 H, 1-H2), 2.86 [s, 3 H, 1-N(CH3)], 2.83 [s, 3 H, 1-
N(CH3)], 2.42 (dd, J = 9.2, 5.2 Hz, 1 H, 3-H or 4-H), 2.28 (dd, J
= 5.2, 5.2 Hz, 1 H, 3-H or 4-H), 2.10 (m, 1 H, 2-H) ppm. 13C NMR
(100 MHz, D2O): δ = 173.9 (C-5 or C-6), 172.9 (C-5 or C-6), 54.2
(C-1), 42.7 [1-N(CH3)], 42.6 [1-N(CH3)], 26.9 (C-3 or C-4), 26.3
˜
(400 MHz, CDCl3): δ = 4.17 (q, J = 7.2 Hz, 2 H), 4.16 (q, J =
7.2 Hz, 2 H), 3.95 (d, J = 7.6 Hz, 2 H), 2.25 (d, J = 8.8 Hz, 2 H),
2.01 (m, 1 H), 1.25 (t, J = 7.2 Hz, 6 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 168.0 (2ϫ), 61.2 (2ϫ), 28.4, 26.6 (2ϫ), 26.4, 14.1
(2ϫ) ppm. HRMS (ESI): calcd. for C10H16O4Br+ [M + H]+
279.0232; found 279.0243.
+
(C-3 or C-4), 22.3 (C-2) ppm. HRMS (ESI): calcd. for C8H14NO4
[M + H]+ 188.0923; found 188.0912.
(1R,2S,3r)-Diethyl 3-[(Dimethylamino)methyl]cyclopropane-1,2-di-
carboxylate (42):
A solution of 3-epi-bromide 41 (3.5 mg,
(1R,2S,3S)-2-Carboxy-3-[(dimethylammonio)methyl]cyclo-
propanecarboxylate (meso-3-epi-Dysibetaine CPa Tertiary Ammo-
nium Analog 46): A suspension of 3-epi-amino diester 42 (7.6 mg,
0.031 mmol) in hydrochloric acid (6 m solution, 1.0 mL) was heated
to 90 °C with stirring. After 4.5 h, the mixture was concentrated
under reduced pressure. The residue was purified by column
chromatography on reversed-phase silica gel (1 g, MeOH/H2O,
10:90) to give 3-epi-DBCPa tertiary ammonium analog 46 (2.5 mg,
100%) as a yellow solid; Rf = 0.35 (MeOH/CHCl3, 50:50). IR
0.013 mmol) and dimethylamine (2.0 m in THF, 0.050 mL,
0.10 mmol) in toluene (0.1 mL) was heated to 125 °C in a sealed
tube. After 9.5 h, the mixture was concentrated under reduced pres-
sure. The residue was purified by column chromatography on silica
gel (1 g, MeOH/CHCl3, 17:83) to give 3-epi-tertiary amine 42
(2.5 mg, 83%) as a yellow oil; Rf = 0.35 (MeOH/CHCl3, 50:50).
IR (film): ν = 3431, 2982, 1732, 1379, 1208, 1178 cm–1. H NMR
1
˜
(400 MHz, CDCl3): δ = 4.18–4.09 (m, 4 H), 3.73 (d, J = 6.0 Hz, 2
H), 2.84 (s, 6 H), 2.41 (m, 1 H), 2.32 (d, J = 9.6 Hz, 2 H), 1.25 (t,
J = 7.2 Hz, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 168.2
(2ϫ), 61.2 (2ϫ), 52.3, 42.7 (2ϫ), 23.7 (2ϫ), 18.6, 14.1 (2ϫ) ppm.
(KBr): ν = 2924, 2754, 1734, 1437, 1180 cm–1. 1H NMR (400 MHz,
˜
D2O): δ = 3.51 (d, J = 8.0 Hz, 2 H, 1-H2), 2.83 [s, 6 H, 1-N-
(CH3)2], 2.31 (d, J = 8.4 Hz, 2 H, 3-H and 4-H), 1.87 (m, 1 H, 2-
H) ppm. 13C NMR (100 MHz, D2O): δ = 173.6 [2ϫ, C-5 and C-
6], 53.2 (C-1), 42.5 [2ϫ, 1-N(CH3)2], 25.1 (2ϫ, C-3 and C-4), 17.9
HRMS (ESI): calcd. for C12H22NO4 [M + H]+ 244.1549; found
+
244.1542.
+
(C-2) ppm. HRMS (ESI): calcd. for C8H14NO4 [M + H]+
1-[(1r,2R,3S)-2,3-Bis(ethoxycarbonyl)cyclopropyl]-N,N,N-trimeth-
ylmethanaminium Iodide (43): A suspension of 3-epi-tertiary amine
188.0923; found 188.0915.
42 (2.8 mg, 0.012 mmol), MeI (0.100 mL, 2.41 mmol), and (1S*,2S*)-Diethyl 3-(Azidomethyl)cyclopropane-1,2-dicarboxylate
NaHCO3 (2.0 mg, 0.036 mmol) in toluene (0.100 mL) was heated (47): To a stirred solution of bromide 33 (26.7 mg, 0.096 mmol)
to 125 °C in a sealed tube. After 6 h, the mixture was concentrated
under reduced pressure. To the residue was added CHCl3 (1 mL),
and the insoluble materials were removed by filtration. The filtrate
was concentrated under reduced pressure to give the crude 3-epi-
in DMF (0.500 mL) at room temp. were added Bu4NI (88.0 mg,
0.239 mmol) and NaN3 (31.0 mg, 0.478 mmol). After stirring at
80 °C for 2.5 h, the mixture was cooled to room temp. and then
poured into H2O (5 mL). The mixture was extracted with EtOAc
12
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
Total Synthesis of (Ϯ)-Dysibetaine CPa and Analogs
(4ϫ5 mL), and the combined organic extracts were washed with
brine (3 mL) and dried with Na2SO4. Concentration under reduced
pressure gave a residue, which was purified by column chromatog-
raphy on silica gel (2.5 g, EtOAc/hexane, 20:80) to give azide 47
79.0, 60.9 (2ϫ), 35.3, 28.3 (4ϫ), 23.8 (2ϫ), 23.3, 14.0 (2ϫ) ppm.
HRMS (ESI): calcd. for C15H25NO6Na+ [M + Na]+ 338.1580;
found 338.1567.
(1S*,2S*,3S*)-2-(Ammoniomethyl)-3-carboxycyclopropanecarb-
oxylate [(؎)-N-Desmethyldysibetaine CPa, 51]: A suspension of N-
Boc-amino diester 49 (2.7 mg, 0.0086 mmol) in hydrochloric acid
(6 m solution, 0.200 mL) was heated to 90 °C with stirring. After
7.5 h, the mixture was concentrated, and the residue was purified
by column chromatography on reversed-phase silica gel (1 g,
MeOH/H2O, 10:90) to give DBCPa N-desmethyl analog 51
(1.3 mg, 100%) as a yellow solid; Rf = 0.60 (BuOH/AcOH/H2O,
(16.9 mg, 73%) as a colorless oil; Rf = 0.62 (EtOAc/hexane =
1
20:80). IR (film): ν = 2983, 2097, 1722, 1456, 1369, 1178 cm–1. H
˜
NMR (400 MHz, CDCl3): δ = 4.19–4.11 (m, 4 H), 3.59 (dd, J =
13.2, 6.4 Hz, 1 H), 3.50 (dd, J = 13.2, 9.0 Hz, 1 H), 2.37 (dd, J =
9.2, 4.8 Hz, 1 H), 2.24 (dd, J = 5.6, 4.8 Hz, 1 H), 2.08 (dddd, J =
9.2, 9.0, 6.4, 5.6 Hz, 1 H), 1.29–1.24 (m, 6 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 170.6, 169.8, 61.6, 61.4, 47.6, 27.1, 26.7,
26.0, 14.1 (2ϫ) ppm. HRMS (ESI): calcd. for C10H15N3O4Na+ [M
+ Na]+ 264.0960; found 264.0962.
33:33:33). IR (KBr): ν = 3419, 3039, 1719, 1645, 1399, 1221,
˜
1
974 cm–1. H NMR (400 MHz, D2O): δ = 3.25 (ddd, J = 13.6, 7.6,
7.2 Hz, 2 H, 1-H2), 2.35 (dd, J = 9.2, 4.4 Hz, 1 H, 3-H or 4-H),
2.17 (dd, J = 6.4, 4.4 Hz, 1 H, 3-H or 4-H), 2.04 (dddd, J = 9.2,
7.6, 7.2, 6.4 Hz, 1 H, 2-H) ppm. 13C NMR (100 MHz, D2O): δ =
175.2 (C-5 or C-6), 173.8 (C-5 or C-6), 36.9 (C-1), 27.3 (C-3 or
C-4), 26.9 (C-3 or C-4), 24.3 (C-2) ppm. HRMS (ESI): calcd. for
Diethyl (1R,2S,3r)-3-(Azidomethyl)cyclopropane-1,2-dicarboxylate
(48): To
a stirred solution of 3-epi-bromide 41 (10.0 mg,
0.036 mmol) in DMF (0.200 mL) at room temp. were added Bu4NI
(33.0 mg, 0.090 mmol) and NaN3 (11.6 mg, 0.179 mmol). After
stirring at 80 °C for 6.5 h, the mixture was cooled to room temp.
and then poured into H2O (0.2 mL). The mixture was extracted
with EtOAc (3ϫ1 mL), and the combined organic extracts were
washed with brine (2 mL) and dried with Na2SO4. Concentration
under reduced pressure gave a residue, which was purified by col-
umn chromatography on silica gel (0.3 g, EtOAc/hexane, 10:90) to
give 3-epi-azide 48 (6.5 mg, 75%) as a colorless oil; Rf = 0.47
+
C6H10NO4 [M + H]+ 160.0610; found 160.0609.
(1R,2S,3S)-2-(Ammoniomethyl)-3-carboxycyclopropanecarboxylate
(meso-3-epi-N-Desmethyldysibetaine CPa, 52): A suspension of 3-
epi-N-Boc-amino diester 50 (2.0 mg, 0.0063 mmol) in hydrochloric
acid (6 m solution, 1.0 mL) was heated to 90 °C with stirring. After
24 h, the mixture was concentrated, and the residue was purified
by column chromatography on reversed-phase silica gel (1 g,
MeOH/H2O, 10:90) to give 3-epi-DBCPa N-desmethyl analog 52
(1.0 mg, 100%) as a yellow solid; Rf = 0.60 (BuOH/AcOH/H2O,
(EtOAc/hexane, 20:80). IR (film): ν = 2983, 2097, 1733, 1381, 1351,
˜
1
1199, 1028 cm–1. H NMR (400 MHz, CDCl3): δ = 4.19–4.13 (m,
4 H), 3.84 (d, J = 7.6 Hz, 2 H), 2.21 (d, J = 9.0 Hz, 2 H), 1.75 (m,
1 H), 1.27–1.23 (m, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ =
168.3 (2ϫ), 61.2 (2ϫ), 46.2, 23.8 (2ϫ), 23.0, 14.1 (2ϫ) ppm. HRMS
(ESI): calcd. for C10H15N3O4Na+ [M + Na]+ 264.0960; found
264.0970.
33:33:33). IR (KBr): ν = 3446, 3225, 1634, 1456, 1399, 1353, 1267,
˜
1
1038, 891, 799 cm–1. H NMR (400 MHz, D2O): δ = 3.42 (d, J =
8.0 Hz, 2 H, 1-H2), 2.35 (d, J = 8.8 Hz, 2 H, 3-H and 4-H), 1.85
(m, 1 H, 2-H) ppm. 13C NMR (100 MHz, D2O): δ = 173.7 (2ϫ, C-
5 and C-6), 35.4 (C-1), 25.0 (2ϫ, C-3 and C-4), 19.9 (C-2) ppm.
Diethyl
(1S*,2S*)-3-{[(tert-Butoxycarbonyl)amino]methyl}-
+
HRMS (ESI): calcd. for C6H10NO4 [M + H]+ 160.0610; found
cyclopropane-1,2-dicarboxylate (49): To a solution of azide 47
(16.9 mg, 0.070 mmol) in THF (0.175 mL) and MeOH (0.525 mL)
at room temp. were added Boc2O (0.077 mg, 0.35 mmol) and
Pd(OH)2 (3.0 mg). After stirring under a hydrogen atmosphere for
4 h, the mixture was filtered through a pad of Celite, and the filtrate
was concentrated under reduced pressure. The residue was purified
by column chromatography on silica gel (2.5 g, EtOAc/hexane,
30:70) to give N-Boc amine 49 (16.9 mg, 76%) as a colorless oil;
160.0603.
Supporting Information (see footnote on the first page of this arti-
1
cle): H and 13C NMR spectra of new compounds, NOESY spec-
trum of cis-cyclopropane 17, as well as chromatographic compari-
son of synthetic DBCPa (1) with its natural counterpart.
Acknowledgments
R = 0.42 (EtOAc/hexane, 30:70). IR (film): ν = 2980, 1739, 1723,
˜
f
1520, 1368, 1252, 1180 cm–1. 1H NMR (400 MHz, CDCl3): δ =
4.67 (br., 1 H), 4.18–4.10 (m, 4 H), 3.50 (m, 1 H), 3.28 (m, 1 H),
2.28 (dd, J = 9.6, 4.8 Hz, 1 H), 2.19 (dd, J = 4.8, 4.8 Hz, 1 H), 2.06
(m, 1 H), 1.42 (s, 9 H), 1.28–1.22 (m, 6 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 171.1, 170.1, 155.7, 61.3 (2ϫ), 37.5, 28.6,
28.4 (4ϫ), 26.8, 26.4, 14.2 (2ϫ) ppm. HRMS (ESI): calcd. for
C15H25NO6Na+ [M + Na]+ 338.1580; found 338.1583.
The authors are grateful to Emeritus Professor Tetsuo Shiba
(Osaka University) for his encouragement. Technical assistance by
Mr. Daiki Uchiyama, Mr. Ryo Kinoshita, Mr. Koichi Fukushima,
Mr. Kento Tanaka, and Ms. Manami Chiba is gratefully acknowl-
edged. We also thank Professor Shigeru Nishiyama (Keio Univer-
sity) for the LC–MS instrument access. This work was partly sup-
ported by the grant for 2010–2012 Strategic Research Promotion
of Yokohama City University, Japan (Nos. T2202, T2309, T2401).
Financial support from the Yamada Science Foundation is also
gratefully acknowledged.
(1R,2S,3r)-Diethyl
3-{[(tert-Butoxycarbonyl)amino]methyl}-
cyclopropane-1,2-dicarboxylate (50): To a solution of 3-epi-azide 48
(10.0 mg, 0.042 mmol) in THF (0.100 mL) and MeOH (0.300 mL)
at room temp. were added Boc2O (0.045 mg, 0.21 mmol) and
Pd(OH)2 (2.0 mg). After stirring under a hydrogen atmosphere for
3 h, the mixture was filtered through a pad of Celite, and the filtrate
was concentrated under reduced pressure. The residue was purified
by column chromatography on silica gel (1.8 g, EtOAc/hexane,
40:60) to give 3-epi-N-Boc amine 50 (7.3 mg, 56%) as a colorless
[1] H. Brauner-Osborne, J. Egebjerg, E. O. Nielsen, U. Madsen, P.
Krogsgaard-Larsen, J. Med. Chem. 2000, 43, 2609–2645.
[2] R. Sakai, H. Kamiya, M. Murata, K. Shimamoto, J. Am.
Chem. Soc. 1997, 119, 4112–4116.
[3] R. Sakai, T. Koike, M. Sasaki, K. Shimamoto, C. Oiwa, A.
Yano, K. Suzuki, K. Tachibana, H. Kamiya, Org. Lett. 2001,
3, 1479–1482.
[4] R. Sakai, C. Oiwa, K. Takaishi, H. Kamiya, M. Tagawa, Tetra-
hedron Lett. 1999, 40, 6941–6944.
[5] R. Sakai, K. Suzuki, K. Shimamoto, H. Kamiya, J. Org. Chem.
2004, 69, 1180–1185.
oil; R = 0.42 (EtOAc/hexane, 30:70). IR (film): ν = 2979, 1731,
˜
f
1717, 1505, 1379, 1176 cm–1. 1H NMR (400 MHz, CDCl3): δ =
5.21 (br., 1 H), 4.15–4.11 (m, 4 H), 3.56 (dd, J = 7.6, 6.8 Hz, 2 H),
2.10 (d, J = 8.6 Hz, 2 H), 1.80 (m, 1 H), 1.42 (s, 9 H), 1.26–1.23
(m, 6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 168.8, 156.0,
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
13

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
M. Oikawa, S. Sasaki, M. Sakai, Y. Ishikawa, R. Sakai
FULL PAPER
[6] R. Sakai, G. T. Swanson, M. Sasaki, K. Shimamoto, H. Ka-
miya, Cent. Nerv. Syst. Agents Med. Chem. 2006, 6, 83–108.
[7] G. T. Swanson, T. Green, R. Sakai, A. Contractor, W. Che, H.
Kamiya, S. F. Heinemann, Neuron 2002, 34, 589–598.
[8] J. M. Sanders, K. Ito, L. Settimo, O. T. Pentikainen, M. Shoji,
M. Sasaki, M. S. Johnson, R. Sakai, G. T. Swanson, J. Pharma-
col. Exp. Ther. 2005, 314, 1068–1078.
[9] M. Sasaki, T. Maruyama, R. Sakai, K. Tachibana, Tetrahedron
Lett. 1999, 40, 3195–3198.
[10] M. Shoji, N. Akiyama, K. Tsubone, L. L. Lash, J. M. Sanders,
G. T. Swanson, R. Sakai, K. Shimamoto, M. Oikawa, M. Sa-
saki, J. Org. Chem. 2006, 71, 5208–5220.
onium ylide analogous to 3 (% yield cis/trans, 61:17), however,
our yield for the desired trans-cyclopropane 18 (26%) was ap-
parently higher. So far, it is unclear why the sterically congested
cis-cyclopropane generally predominates over the trans isomer
in the thermodynamically-controlled cyclopropanations. Ef-
forts are continuously made to improve the diastereoselectivity,
even though the diastereomers can be readily separated in all
cases by silica gel column chromatography.
[24] J. S. Park, S. C. Moon, K. U. Balik, J. Y. Cho, E. S. Yoo, Y. S.
Byun, M. H. Park, Arch. Pharm. Res. 2002, 25, 137–142.
[25] D. J. Adams, A. J. Blake, P. A. Cooke, C. D. Gill, N. S.
Simpkins, Tetrahedron 2002, 58, 4603–4615.
[11] K. Frydenvang, L. L. Lash, P. Naur, P. A. Postila, D. S. Picker-
ing, C. M. Smith, M. Gajhede, M. Sasaki, R. Sakai, O. T. Pen-
tikaïnen, G. T. Swanson, J. S. Kastrup, J. Biol. Chem. 2009,
284, 14219–14229.
[12] T. A. Siddiquee, J. M. Lukesh, S. Lindeman, W. A. Donaldson,
J. Org. Chem. 2007, 72, 9802–9803.
[13] M. Oikawa, S. Sasaki, M. Sakai, R. Sakai, Tetrahedron Lett.
2011, 52, 4402–4404.
[14] I. A. Levandovskiy, D. I. Sharapa, T. V. Shamota, V. N. Ro-
dionov, T. E. Shubina, Future Med. Chem. 2011, 3, 223–241.
[15] V. Rodríguez-Soria, L. Quintero, F. Sartillo-Piscil, Tetrahedron
2008, 64, 2750–2754.
[26] It should also be noted that the experiments shown in
Schemes 4and 5 have evolved into a strategy directed toward
the asymmetric synthesis of dysibetaine CPa (1). That is, al-
though no direct evidence was obtained so far, the reduction
of 23B with LiAlH4 to give 27 (see Scheme 4) might have pro-
ceeded through cyclic imide 16 (see Scheme 5), which is no
longer a chiral but a meso compound. Because of this possible
racemization process caused by the undesirable cyclization
(23B Ǟ 16 Ǟ 27 Ǟ 28), the asymmetry in this synthesis should
not be introduced before the reduction. Instead, the asymmetry
should be introduced by the asymmetric reduction of a meso
imide such as 16.
[16] D. J. Aitken, S. D. Bull, I. R. Davies, L. Drouin, J. Ollivier, J. [27] J. Boukouvalas, I.-I. Radu, Tetrahedron Lett. 2007, 48, 2971–
Peed, Synlett 2010, 2729–2732.
2973.
[17] Y. Ohfune, K. Shimamoto, M. Ishida, H. Shinozaki, Bioorg.
Med. Chem. Lett. 1993, 3, 15–18.
[18] K. Gajcy, J. Pe˛kala, B. Fra˛ckowiak-Wojtasek, T. Librowski, S.
Lochyn´ski, Tetrahedron: Asymmetry 2010, 21, 2015–2020.
[19] F. Gnad, M. Poleschak, O. Reiser, Tetrahedron Lett. 2004, 45,
4277–4280.
[20] V. K. Aggarwal, H. W. Smith, G. Hynd, R. V. H. Jones, R.
Fieldhouse, S. E. Spey, J. Chem. Soc. Perkin Trans. 1 2000,
3267–3276.
[21] M. P. Cava, A. A. Deana, K. Muth, M. J. Mitchell, Org. Synth.
1961, 41, 93–95.
[28] F. Kong, G. R. Morais, R. A. Falconer, C. W. Sutton, Tetrahe-
dron Lett. 2012, 53, 546–549.
[29] J. M. Grisar, M. A. Petty, F. N. Bolkenius, J. Dow, J. Wagner,
E. R. Wagner, K. D. Haegele, J. W. De, J. Med. Chem. 1991,
34, 257–260.
[30] M.-C. Bonache, C. Chamorro, S. Velazquez, C. E. De, J. Balza-
rini, B. F. Rodriguez, F. Gago, M.-J. Camarasa, A. San-Felix,
J. Med. Chem. 2005, 48, 6653–6660.
[31] The relative stereochemistry of 1 was proposed in the original
paper[5] and recently confirmed by the synthesis of the race-
mate.[12]
.
[22] M. Biagetti, C. P. Leslie, A. Mazzali, C. Seri, D. A. Pizzi, J.
Bentley, T. Genski, F. R. Di, L. Zonzini, L. Caberlotto, Bioorg.
Med. Chem. Lett. 2010, 20, 4741–4744.
[32] M. Sasaki, K. Tsubone, K. Aoki, N. Akiyama, M. Shoji, M.
Oikawa, R. Sakai, K. Shimamoto, J. Org. Chem. 2007, 73, 264–
273.
[33] Recently, by modifying this synthetic route developed for the
racemate, we succeeded in the asymmetric synthesis of DBCPa
(1), although the enantiomeric purity is not still satisfactory.
The results will be reported in due course.
[34] T. Arai, T. Matsumura, T. Oka, Kagaku to Kyoiku 1993, 41,
278–279.
[35] N. Matuszak, G. G. Muccioli, G. Labar, D. M. Lambert, J.
Med. Chem. 2009, 52, 7410–7420.
[36] K. P. Haval, S. B. Mhaske, N. P. Argade, Tetrahedron 2006, 62,
937–942.
[23] During the studies for the cyclopropanation (see Scheme 2), we
found that it was necessary to carry out the reaction: (1) under
high dilution (ca. 0.03 m) and (2) by the addition of the malei-
mide to the ylide. In other cases, the polymerization of the
maleimides was observed as a serious side reaction. However,
the equivalency of reagents was not strictly optimized, except
for the syntheses of 17 and 18, where equimolar amounts of
maleimide 10 and ylide 3 were found to be sufficient for a satis-
factory combined yield (% yield 17/18, 48:26). On the other
hand, we were unable to improve the diastereoselectivity of the
cyclopropanation, and the desired trans isomer was obtained
as a minor product in all of the cases shown in Scheme 2. The
same selectivity had also been observed by Biagetti et al.[22] in
the reaction between N-benzylmaleimide and a diphenylsulf-
[37] N. Coskun, H. Mert, N. Arikan, Tetrahedron 2006, 62, 1351–
1359.
Received: May 31, 2012
Published Online: ᭿
14
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20730
/KAP1
Date: 29-08-12 15:08:12
Pages: 15
Total Synthesis of (Ϯ)-Dysibetaine CPa and Analogs
Total Synthesis
M. Oikawa,* S. Sasaki, M. Sakai,
Y. Ishikawa, R. Sakai ..................... 1–15
Total Synthesis of (Ϯ)-Dysibetaine CPa
and Analogs
The syntheses of the marine sponge-de-
rived γ-amino carboxylic acid dysibetaine
CPa and five analogs in their racemic forms
were successfully performed by taking ad-
vantage of an electron-withdrawing N-(4-
nitrophenyl) group in the cyclopropanation
reaction, the reductive ring opening of an
imide, and the ethanolysis of an N-Boc-
protected imide.
Keywords: Total synthesis / Natural prod-
ucts / Amino acids / Neurological agents /
Diastereoselectivity / Chemoselectivity
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
15