Synthesis of bicyclic lactones via I2-mediated intramolecular tandem C–C/C–O bond formation

Article abstract of DOI:10.1016/j.tet.2018.04.081

The iodine/DMAP-mediated intramolecular tandem C–C/C–O bond forming reaction of malonate bearing alkene moiety proceeded to give bicyclic lactones with good diastereoselectivity in good yield. The mechanistic investigation was also discussed on the basis

Full text of DOI:10.1016/j.tet.2018.04.081

Accepted Manuscript
Synthesis of bicyclic lactones via I -mediated intramolecular tandem C–C/C–O bond
2
formation
Saki Maejima, Mai Osuka, Eiji Yamaguchi, Akichika Itoh
PII:
S0040-4020(18)30486-1
10.1016/j.tet.2018.04.081
TET 29496
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 9 April 2018
Revised Date: 23 April 2018
Accepted Date: 25 April 2018
Please cite this article as: Maejima S, Osuka M, Yamaguchi E, Itoh A, Synthesis of bicyclic lactones
via I -mediated intramolecular tandem C–C/C–O bond formation, Tetrahedron (2018), doi: 10.1016/
2
j.tet.2018.04.081.
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Synthesis of bicyclic lactones via I2-mediated
intramolecular tandem C–C/C–O bond
formation
Leave this area blank for abstract info.
Saki Maejima, Mai Osuka, Eiji Yamaguchi, Akichika Itoh
Gifu Pharmaceutical University

1
ACCEPTED MANUSCRIPT
Tetrahedron
journal homepage: www.elsevier.com
Synthesis of bicyclic lactones via I2-mediated intramolecular tandem C–C/C–O bond
formation
Saki Maejima a, Mai Osuka a, Eiji Yamaguchi a, and Akichika Itoh a,
a Gifu Pharmaceutical University, 1-25-4, Daigaku-nishi, Gifu 501-1196, Japan
ARTICLE INFO
ABSTRACT
Article history:
Received
Received in revised form
Accepted
The iodine/DMAP-mediated intramolecular tandem C–C/C–O bond forming reaction of
malonate bearing alkene moiety proceeded to give bicyclic lactones with good
diastereoselectivity in good yield. The mechanistic investigation was also discussed on the basis
of various control experimental results.
Available online
2009 Elsevier Ltd. All rights reserved
.
Keywords:
Lactones
Polycyclic compounds
Cyclization
C–C bond formation
Molecular iodine
———
Corresponding author. e-mail: yamaguchi@gifu-pu.ac.jp
Corresponding author. e-mail: itoha@gifu-pu.ac.jp

2
Tetrahedron
ACCEPTED MANHUerSeiCn,RwIPe T
1. Introduction
report that intramolecular C–C/C–O bond
formation in alkene group-containing malonates is efficiently
promoted by molecular iodine/base combinations to afford
bicyclic lactones.
The high abundance of naturally occurring polycyclic lactones
and their unique biological activities make the stereoselective
construction of these species a matter of great importance for the
fields of pharmaceuticals, agrichemicals, and organic synthesis.1–
3 Consequently, a range of corresponding synthetic methods have
been developed, e.g., Pd-catalyzed intramolecular cyclization,4
Lewis or Bronsted acid–mediated cyclization,5 Os-catalyzed
oxidative carboesterification of olefins,6 ferrocenium ion–
mediated oxidative cyclization,7 and Mn-mediated intramolecular
radical cyclization,8 although the search for more
environmentally friendly methodologies is still ongoing. By way
of an example, polycyclic lactones can be obtained by iodine-
2. Result and discussion
Initially, we focused on the lactonization of 1a to afford 2a in
the presence of various iodine/base mixtures under irradiation
with visible light emitted by a compact fluorescent lamps (CFLs)
(Table 1). When the above reaction was conducted using
methanolic K2CO3 as the base, only traces of 2a were obtained
(entry 1), while other carbonate bases (Na2CO3, CaCO3, SrCO3,
and BaCO3) were equally ineffective (entries 2–5). Although the
use of Ca(OH)2 and Sr(OH)2 as stronger bases did not result in
product formation, 2a was obtained in 19% yield in the presence
of Ba(OH)2 (entries 6–8). Encouraged by this result, several key
parameters including solvent, temperature, and reaction time
were screened for the second step using Ba(OH)2 as the base. As
a result, we found that bicyclic lactonization could be achieved
by heating 1a in the presence of molecular iodine and Ba(OH)2
instead of utilizing visible light irradiation (entries 8 vs. 9 and
10).
mediated electrophilic cyclization performed utilizing
a
combination of molecular iodine with strong Lewis acids or
bases.9,10
Recently, we have developed iodine-mediated (catalyzed)
intra-
and
intermolecular
transformations
affording
polyfunctionalized heterocyclic compounds.11 In the course of
our work on iodine-mediated transformation of carbonyl
compounds with non-activated C=C π-bonds, we unexpectedly
found that carbocyclization furnished bicyclic lactones,11b which
indicated that the intramolecular formation of a C–C bond
between the olefin and the carbon α to the carbonyl group
occurred in a 5-exo-trig manner (Scheme 1a). Therefore, we
proposed that intramolecular C–C/C–O bond formation could be
realized for olefin moiety-bearing malonates under similar
reaction conditions (Scheme 1b).
Subsequently, various organic bases were screened under
heating conditions. Aliphatic amines such as trimethylamine,
diisopropylamine, and pyrrolidine were inferior to Ba(OH)2 in
terms of reaction yield (entries 10 vs. 11–13), with pyridine and
lutidine, known to induce electrophilic iodine activation, being
equally ineffective (entries 14 and 15).12 When N,N-
dimethylaminopyridine (DMAP) was employed as a base, the
target product was obtained in 63% yield (entry 16). Finally, the
best yield of 88% was obtained using 1.5 equivalents of
molecular iodine and DMAP even under the air condition (entry
18).
a. Our previous result
H
N
H
N
CaI2
CFLs
CO2Me
CO2Me
With the optimized reaction conditions in hand, the reaction
scope was explored by varying substituents on the side chain of
malonates 1 (Table 2). Similarly to the non-functionalized
dimethylmalonate derivative 1a, malonate 1b (dimethyl
substituted at the allylic position) also gave the corresponding
bicyclic lactone 2b in good yield (77%) in the presence of iodine
and DMAP (entry 2). In the case of 3-phenyl-4-pentenylmalonate
1c, product 2c was obtained in moderate yield with almost
complete diastereoselectivity (entry 3). The iodine/DMAP–
mediated lactonization could also be applied to 2-substituted 4-
pentenylmalonate derivatives 1d, 1e, and 1f, affording the
corresponding products in moderate to good yields with good
diastereoselectivities (entries 4–6). Furthermore, 1-methyl
derivative 1g afforded the desired bicyclic lactone 2g in good
yield without any diastereoselectivity decrease (entry 7).
not formed
tAmyl-OH
air, 20 h
CO2Me
CO2Me
H
N
CO2Me
O
H
O
product
b. This work
O
O
I2
base
CO2Me
CO2Me
H
CO2Me
Scheme 1. (a) Previously reported iodine-mediated bicyclic
lactone formation and (b) the reaction investigated in this
work.
Table 1. Optimization of reaction conditionsa
O
O
CO2Me
CO2Me
I2 (1 equiv.), base (1 equiv.)
solvent, conditions
H
CO2Me
1a
2a
Entry
Base
Solvent
Conditionsb
Yield (%)c
trace
1
2
3
4
K2CO3
Na2CO3
CaCO3
SrCO3
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
CFLs, Ar, 20 h
CFLs, Ar, 20 h
CFLs, Ar, 20 h
CFLs, Ar, 20 h
trace
trace
trace

3
5
BaCO3
MeOH (1 mL)
CFLs, Ar, 20 h
trace
trace
trace
(19)e
39
ACCEPTED MANUSCRIPT
6
Ca(OH)2
Sr(OH)2
Ba(OH)2
Ba(OH)2
Ba(OH)2
Et3N
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (1 mL)
MeOH (2 mL)
MeOH (2 mL)
CFLs, Ar, 20 h
7
CFLs, Ar, 20 h
CFLs, Ar, 20 h
40 °C, Ar, 20 h
70 °C, Ar, 20 h
70 °C, Ar, 20 h
70 °C, Ar, 20 h
70 °C, Ar, 20 h
70 º°C, Ar, 20 h
70 °C, Ar, 20 h
70 °C, Ar, 20 h
70 °C, Ar, 20 h
70 °C, Air, 20 h
8
9
10
11
12
13
14
15
16
17
18d
51
trace
35
HNiPr2
pyrrolidine
pyridine
lutidine
DMAP
28
n.r.
6
63
DMAP
67
DMAP
90 (88)e
a Reaction conditions: 1a (0.3 mmol), I2 (1.0 equiv.) and base (1.0 equiv.) in solvent were stirred under the condition above.
b CFLs represents Compact Fluorescent Lamps
c Yield was determined by the NMR analysis of the crude reaction mixture using 1,1,2,2-tetrachloroethane as an internal standard.
d The reaction performed using I2 (1.5 equiv.) and DMAP (1.5 equiv.).
e Isolated yield.
CO2Me
O
7
68
Table 2. Scope of the developed bicyclic lactone formation
O
reactiona, b
CO2Me
H
CO2Me
Me
dr = 88:12
O
Me
O
I2 (1.5 equiv.)
CO2Me
CO2Me
1g
DMAP (1.5 equiv.)
2g
H
CO2Me
MeOH (2 mL)
Air, 70 ºC, 20 h
CO2Me
CO2Me
Me
Me
8
9
78
O
O
Me
Me
H
CO2Me
1
2
Me
1h
Entry
1
1
2
Yield (%)
2h
CO2Me
CO2Me
CO2Me
CO2Me
O
O
88
68
Me
O
O
H
CO2Me
H
CO2Me
dr = 67:33
1a
1i-E
2a
2i
2i
CO2Me
CO2Me
O
CO2Me
CO2Me
2
3
4
77
10
11
71
O
H
CO2Me
dr = 67:33
Me
Me Me
Me
1i-Z
Me
1b
2b
CO2Me
CO2Me
O
62
Ph
O
CO2Me
CO2Me
O
50
Ph
O
H
CO2Me
dr = 88:12
H
CO2Me
dr > 95:5
1j-E
Ph
Ph
2j
2j
1c
Me CO2Me
CO2Me
2c
CO2Me
CO2Me
12
31
O
66
O
dr = 84:16
Ph
1j-Z
dr = 85:15
H
CO2Me
1d
a Isolated yield.
Me
H
2d
b Diastereomeric ratio (dr) was determined by 1H NMR analysis
of crude reaction mixture.
5
6
O
94
O
CO2Me
CO2Me
dr = 77:23
H
CO2Me
The developed reaction was applicable to 5,5-
dimethylsubstituted derivative 1h, furnishing the desired product
in 78% yield (entry 8). Moreover, the cyclization of 1i-E and 1i-
Z gave bicyclic lactone 2i in yields of 68 and 71% with identical
1e
Ph CO2Me
CO2Me
H
2e
53
O
O
diastereoselectivity, respectively (entries
9 and 10). The
dr = 88:12
H
CO2Me
1
assignments were based on a comparison of the obtained H
NMR and 13C NMR spectra with those reported by Taguchi.9a
Therefore, the developed lactonization was concluded to be
markedly different from the titanium alkoxide/iodine–mediated
SN2-type cyclization of 1i-E and 1i-Z, which was reported to
1f
Ph
H
2f

4
Tetrahedron
ACCEPTED MANUSCRIPT
almost exclusively afford a single syn diastereomer of bicyclic
different depend on the structure 1a-I. First, the lactonization of
primary alkyl iodide could be occurred through SN2-type reaction
(route 1).13 Second mechanism is through carbocation
intermediate. The heterolytic cleavage of the C–I bond of 1a-I
under thermal conditions is believed to furnish the stable
carbocation intermediate 1a-II, which undergoes iodide-mediated
cyclization to give the desired bicyclic lactone 2 (route 2).
lactone 2i in the case of 1i-E and trans bicyclic lactone 2i in the
case of 1i-Z (entries 9 and 10).9a This tendency was also observed
when 1j-E and 1j-Z were used as substrates (entries 11 and 12),
which indicated that the cyclization step proceed via an SN1-type
mechanism and gave the thermodynamically most stable
diastereomer.9d
To elucidate the reaction mechanism, control experiments
were carried out (Scheme 2). The reaction of 1a with
iodine/DMAP at room temperature afforded the desired product
in only 13% yield, mainly furnishing cyclopentyl ring–containing
1a-I (65% yield), which was tentatively identified as a possible
reaction intermediate (Scheme 2, eq. 1). Heating of 1a-I at 70 °C
in methanol in the absence of base resulted in the formation of
the desired product in 66% yield (Scheme 2, eq. 2). Thus, it was
concluded that the first carbocyclization proceeded smoothly
under optimal conditions even at room temperature to afford
intermediate 1a-I, whereas the second rate-determining step
corresponded to lactone formation.
3. Conclusion
In summary, we have developed a robust synthetic method for
the formation of functionalized and bicyclic lactones containing
all-carbon quaternary stereocenters from simple linear precursors
and are currently investigating the above transformation in the
context of natural product synthesis.
4. Experimental section
4.1. General Information
Unless otherwise noted, all reactants or reagents including dry
solvents were obtained from commercial suppliers and used as
received. Malonate 1a-1j8i were prepared according to the
procedure reported. Malonates 1a,14 1d,9d 1e,9e 1i9a are known
and their analytical data are in full agreement with those reported
in cited references.
I2 (1.0 equiv.)
DMAP (1.0 equiv.)
CO2Me
CO2Me
CO2Me
CO2Me
I
1a-I
+
2a (1)
MeOH
rt, 20 h
H
1a
65%
13%
Analytical thin-layer chromatography (TLC) was carried out
using 0.25 mm commercial silica gel plates (Merck silica gel 60
F254). Flash column chromatography was performed with Kanto
silica gel 60N (Spherical, Neutral, 40–50 µm). Visualization of
the developed chromatogram was performed by UV lamp (254
nm) and p-anisaldehyde or basic potassium permanganate stain.
NMR spectra were recorded on a JEOL ECA 500 spectrometer
(500 MHz for 1H NMR, 125MHz for 13C NMR), and are
internally referenced to residual protic solvent signals or TMS
(note: CDCl3 referenced at δ 7.26 and 77.0 ppm respectively,
O
O
CO2Me
H
CO2Me
(2)
CO2Me
I
MeOH, 70 ºC, 20 h
H
2a
1a-I
66%
Scheme 2. Control experiments for evaluation of the reaction
mechanism
Based on the previously reported iodine-mediated bicyclic
lactone formation reactions and the results of our control
experiments, the following mechanism was suggested (Scheme
3).9
1
TMS referenced at δ 0 and 0 ppm respectively). Data for H
NMR are reported as follows: chemical shift (δ ppm),
multiplicity (s = singlet, d = doublet, t = triplet, q = quartet, m =
multiplet, br = broad, dd = doublet of doublets, ddd = doublet of
doublet of doublets, td = triplet of doublets), coupling constant
(Hz), integration, and assignment. Data for 13C NMR are reported
in terms of chemical shifts (δ ppm). IR spectra were recorded on
a Perkin Elmer Spectrum 100 FTIR spectrometer and are
reported in terms of frequency of absorption (cm–1). High-
resolution mass spectra (HRMS) were obtained on a JEOL JMS-
T100TD and are reported as m/z.
NMe2
N
I2
DMAP
MeO
OH
CO2Me
CO2Me
I
R
CO2Me
R
1
route 1: SN2 pathway
I-
n-Bu
H
4.2. General procedure for the preparation of 4-pentenyl
O Me
malonate derivatives 1
O
O
CO2Me
MeO2C
I
Triethylamine (1.5 equiv.) was added to a stirred solution of
alcohol (1.0 equiv.) in dry DCM (0.2 M) and cooled to 0 °C after
which MsCl (1.2 equiv.) was added. The solution was allowed to
warm to room temperature and stirred for 1.5 h after which time
aqueous 0.5 M HCl solution (4.5 mL/mmol alcohol) was added.
The layers were separated and the aqueous layer was extracted
with DCM (3×4.5 mL/mmol). The combined organic extracts
were dried (MgSO4), filtered, and the solvent removed in vacuo
to give the mesylate. Sodium hydride (60 % in mineral oil, 2.5
equiv.) was suspended in dry DMF (0.2 M) and cooled to 0 °C,
after which dimethyl malonate (2.5 equiv.) was added dropwise
and the mixture was stirred for 20 minutes. A solution of the
mesylate (1.0 equiv.) in dry THF (0.2 M) was added followed by
potassium iodide (1.0 equiv.) and the solution was stirred at 80
°C overnight. After cooling to RT, the solution was poured onto
saturated NH4Cl solution (7 mL/mmol mesylate) and extracted
with EtOAc (3×7 mL/mmol mesylate). The combined organic
CO2Me
I
1a-I: R = H
route 2: SN1 pathway
O
- MeI
H
I-
H
R
n-Bu
H
2
1a-I
O Me
O
R
1a-II: R = alkyl, Ar
Scheme 3. Plausible reaction mechanism
The reaction is thought to be initiated by the coordination of the
iodonium-DMAP adduct to the olefin moiety of 1, with the
subsequent cyclization at the α-position of the carbonyl affording
the five-membered intermediate 1a-I. If the rate of this
cyclization is slow, the iodonium intermediate can be attacked by
iodide instead of the carbon nucleophile to form a diiodide
species. It is assumed that mechanism for lactonization step is

5
extracts were washed with water, dried (MgSO4), filtered, and the
solvent removed in vacuo to give the crude product.
838 cm-1.; HMRS m/z (DART) [M+H]+: calcd for C12H21O4:
229.1434; found: 229.1437.
ACCEPTED MANUSCRIPT
4.2.1. Dimethyl (3,3-dimethyl-4-pentenyl)propanediate (1b)
4.2.6. (E)-Dimethyl (5-phenyl-4-pentenyl)propanediate (1j-E)
The product was obtained in 57% yield (2.6 g, 11.4 mmol) after
The product was obtained in 64% yield (3.5 g, 12.8 mmol) after
column chromatography on silica gel (n-hexane : EtOAc = 10 :
1) as a coloress oil. 1H NMR (500 MHz, CDCl3): δ 5.45-5.34 (m,
2H), 3.74 (s, 6H), 3.36 (t, J = 7.5 Hz, 1H), 2.02 (q, J = 7.5 Hz,
2H), 1.92-1.87 (m, 2H), 1.64 (d, J = 6.3 Hz, 3H), 140-1.31 (m,
2H).; 13C NMR (125 MHz, CDCl3): δ 169.9, 130.3, 125.5, 52.4,
51.5, 32.0, 28.3, 27.2, 17.8.; FTIR (neat): 3026, 2998, 2955, 2859,
1752, 1735, 1435, 1345, 1282, 1265, 1236, 1215, 1197, 1152,
1054, 1011, 967, 920 cm-1.; HMRS m/z (DART) [M+H]+: calcd
for C16H21O4: 277.1434; found: 277.1433.
column chromatography on silica gel (n-hexane : EtOAc = 10 : 1)
1
as a colorless oil. H NMR (500 MHz, CDCl3): δ 5.42 (ddd, J =
17.2, 10.9, 2.9 Hz, 1H), 4.96-4.91 (m, 2H), 3.74 (s, 6H), 3.29 (t, J
= 7.5 Hz, 1H), 1.86-1.80 (m, 2H). 1.30-1.26 (m, 2H), 1.00 (s,
6H).; 13C NMR (125 MHz, CDCl3): δ 169.8, 147.4, 111.0, 52.4,
52.1, 39.9, 36.4, 26.5, 24.3.; FTIR (neat): 2958, 1754, 1736, 1640,
1457, 1435, 1345, 1273, 1253, 1225, 1203, 1144, 1004, 913, 689
cm-1.; HMRS m/z (DART) [M+H]+: calcd for C12H21O4:
229.1434; found: 229.1439.
4.2.2. Dimethyl (3-phenyl-4-pentenyl)propanediate (1c)
4.2.7. (Z)-Dimethyl (5-phenyl-4-pentenyl)propanediate (1j-Z)
The product was obtained in 52% yield (284 mg, 2.0 mmol) after
The product was obtained in 67% yield (8.6 g, 31 mmol) after
column chromatography on silica gel (n-hexane : EtOAc = 10 : 1)
as a colorless oil. H NMR (500 MHz, CDCl3): δ 7.31-7.16 (m,
column chromatography on silica gel (n-hexane : EtOAc = 10 : 1)
as a colorless oil. H NMR (500 MHz, CDCl3): δ 5.49-5.34 (m,
1
1
5H), 5.91 (ddd, J = 17.2, 9.2, 7.5 Hz, 1H), 5.06-5.03 (m, 2H),
3.72 (s, 3H), 3.71 (s, 3H), 3.35 (t, J = 7.5 Hz, 1H), 3.25 (q, J =
7.5 Hz, 1H), 1.98-1.61 (m, 4H).; 13C NMR (125 MHz, CDCl3): δ
169.7, 143.6, 141.4, 128.5, 127.4, 126.4, 114.6, 52.5, 51.5, 49.6,
32.8, 26.9.; FTIR (neat): 3066, 3028, 3001, 2954, 1752, 1733,
1637, 1601, 1493, 1453, 1435, 1346, 1243, 1222, 1197, 1152,
1002, 917, 751, 702 cm-1.; HMRS m/z (DART) [M+H]+: calcd
for C16H21O4: 277.1434; found: 277.1432.
2H), 3.74 (s, 6H), 3.37 (t, J = 7.5 Hz, 1H), 2.07 (q, J = 7.5 Hz,
2H), 1.94-1.89 (m, 2H), 1.60 (d, J = 6.3 Hz, 3H), 140-1.35 (m,
2H).; 13C NMR (125 MHz, CDCl3): δ 169.8, 129.5, 124.5, 52.4,
51.5, 28.4, 27.1, 26.3.; FTIR (neat): 3014, 2955, 2938, 2862,
1753, 1735, 1435, 1341, 1270, 1238, 1215, 1199, 1152, 1119,
1046, 1005, 832, 704 cm-1.; HMRS m/z (DART) [M+H]+: calcd
for C16H21O4: 277.1434; found: 277.1437.
4.3. General procedure for the preparation of bicyclic lactones 2
4.2.3. Dimethyl (2-phenyl-4-pentenyl)propanediate (1f)
A Pyrex® test tube (16.5 cm × 1.5 cm) containing a mixture
of 2 (0.3 mmol), I2 (114 mg, 1.5 epuiv., 0.3 mmol) and DMAP
(54.9 mg, 1.5 epuiv., 0.3 mmol) in methanol (2.0 mL) was stirred
at 70 ºC under air for 20 h. After cooling to room temperature,
the solvent was removed under reduced pressure. The resulting
mixture was purified by flash column chromatography on silica
gel (n-hexane : EtOAc) to give 2.
The product was obtained in 16% yield (193 mg, 0.7 mmol) after
column chromatography on silica gel (n-hexane : EtOAc = 10 : 1)
1
as a coloress oil. H NMR (500 MHz, CDCl3): δ 7.31-7.12 (m,
5H), 5.62 (ddd, J = 17.2, 10.3, 6.9 Hz, 1H), 5.01-4.93 (m, 2H),
3.74 (s, 3H), 3.60 (s, 3H), 3.16 (dd, J = 9.7, 4.6 Hz, 1H), 2.65-
2.60 (m, 1H), 2.41-2.35 (m, 3H), 2.11 (ddd, J = 16.0, 10.3, 4.6
Hz, 1H).; 13C NMR (125 MHz, CDCl3): δ 169.8, 142.9, 136.1,
128.5, 127.7, 126.7, 116.5, 52.4, 49.7, 43.6, 41.4, 34.7.; FTIR
(neat): 3064, 3026, 2998, 2954, 1750, 1732, 1641, 1603, 1494,
1435, 1340, 1259, 1231, 1200, 1149, 1027, 999, 914, 845, 765,
701 cm-1.; HMRS m/z (DART) [M+H]+: calcd for C16H21O4:
277.1434; found: 277.1436.
4.3.1. (3aRS,6aSR)-Methyl 3-oxohexahydro-1H-cyclopenta-
[c]-furan-3a-carboxylate (2a)
The product was obtained in 88% yield (48.5 mg, 0.26 mmol)
after column chromatography on silica gel (n-hexane : EtOAc =
4 : 1) as a colorless oil.; 1H NMR (500 MHz, CDCl3): δ 4.56 (dd,
J = 9.2, 8.5 Hz, 1H), 4.08 (dd, J = 9.2, 2.3 Hz, 1H), 3.78 (s, 3H),
3.13-3.09 (m, 1H), 2.41-2.35 (m, 1H), 2.29-2.25 (m, 1H), 2.11-
2.05 (m, 1H), 1.85-1.81 (m, 1H), 1.71-1.62 (m, 2H).; 13C NMR
(125 MHz, CDCl3): δ 176.4, 170.4, 73.0, 61.5, 53.1, 45.5, 34.6,
34.0, 25.6.; FTIR (neat): 2957, 2874, 1767, 1738, 1449, 1435,
1379, 1320, 1251, 1203, 1168, 1142, 1114, 1053, 1010, 976, 920,
863, 841, 792, 757, 726, 684 cm-1.; HMRS m/z (DART) [M+H]+:
calcd for C9H13O4: 185.0808; found: 185.0805. Data was
consisted with the literature. 8f
4.2.4. Dimethyl (1-methyl-4-pentenyl)propanediate (1g)
The product was obtained in 77% yield (1.1 g, 5.1 mmol) after
column chromatography on silica gel (n-hexane : EtOAc = 10 :
1
1) as a colorless oil. H NMR (500 MHz, CDCl3): δ 5.79 (ddd, J
= 16.6, 10.3, 6.6 Hz, 1H), 5.04-4.95 (m, 2H), 3.73 (s, 6H), 3.30
(d, J = 8.0 Hz, 1H), 2.31-2.25 (m, 1H), 2.17-2.11 (m, 1H), 2.07-
1.99 (m, 1H), 1.55-1.48 (m, 1H), 1.33-1.26 (m, 1H), 1.00 (d, J =
6.9 Hz, 3H).; 13C NMR (125 MHz, CDCl3): δ 169.2, 138.0,
114.8, 57.3, 52.2, 33.4, 32.9, 31.0, 16.7.; FTIR (neat): 2954, 1755,
1735, 1641, 1455, 1435, 1346, 1286, 1239, 1223, 1194, 1152,
1018, 1000, 912 cm-1.; HMRS m/z (DART) [M+H]+: calcd for
C11H19O4: 215.1278; found: 215.1286.
4.3.2.
(3aRS,6aSR)-Methyl-6,6-dimethyl-3-oxohexahydro-1H-
cyclopenta[c]-furan-3a-carboxylate (2b)
The product was obtained in 77% yield (49 mg, 0.23 mmol) after
column chromatography on silica gel (n-hexane : EtOAc = 4 : 1)
as a colorless oil.; H NMR (500 MHz, CDCl3): δ 4.42 (dd, J =
4.2.5. Dimethyl (5-methyl-4-hexynyl)propanediate (1h)
1
The product was obtained in 75% yield (1.3 g, 5.9 mmol) after
9.7, 7.5 Hz, 1H), 4.28 (dd, J = 9.7, 2.3 Hz, 1H), 3.78 (s, 3H), 2.70
(dd, (s, J = 7.5, 2.3 HZ, 1H), 2.59 (ddd, J = 13.8, 8.0, 5.7 Hz, 1H),
2.22 (ddd, J = 13.8, 7.5, 5.2 Hz, 1H), 1.65 (ddd, J = 13.2, 7.5, 5.7
Hz, 1H), 1.55 (dd, J = 13.2, 8.0, 5.2 Hz, 1H), 1.06 (s, 3H), 1.01
(s, 3H).; 13C NMR (125 MHz, CDCl3): δ 176.8, 170.7, 68.0, 61.5,
56.0, 55.1, 42.4, 40.5, 31.7, 28.8, 23.0.; FTIR (neat): 2959, 2871,
1769, 1738, 1459, 1435, 1370, 1311, 1255, 1206, 1171, 1125,
1059, 1043, 996, 978, 930, 881, 797, 730, 685 cm-1.; HMRS m/z
(DART) [M+H]+: calcd for C11H17O4: 213.1121; found: 213.1111.
column chromatography on silica gel (n-hexane : EtOAc = 10 : 1)
1
as a colorless oil. H NMR (500 MHz, CDCl3): δ 5.10-5.06 (m,
1H), 3.74 (s, 3H), 3.37 (t, J = 7.5 Hz, 1H), 2.01 (q, J = 7.5 Hz,
2H), 1.93-1.88 (m, 2H), 1.68 (s, 3H), 1.59 (s, 3H), 1.38-1.31 (m,
2H).; 13C NMR (125 MHz, CDCl3): δ 169.9, 132.0, 123.6, 52.3,
51.5, 28.4, 27.5, 25.6, 17.6.; FTIR (neat): 2955, 1752, 1735, 1435,
1379, 1346, 1288, 1271, 1225, 1201, 1147, 1112, 1063, 1008,

6
Tetrahedron
1
ACCEPTED MANUSCRIPT
(3aRS,6aSR)-Methyl-3-oxo-6-phenyltetrahydro-1H-
4.3.3.
as a colorless oil.; H NMR (500 MHz, CDCl3): Major isomer δ
4.44 (dd, J = 9.2, 6.8 Hz, 1H), 4.12 (d, J = 9.2 Hz, 1H), 3.80 (s,
3H), 3.39-3.35 (m, 1H), 2.80-2.75 (m, 1H), 2.32-2.24 (m, 1H),
1.89-1.82 (m, 1H), 1.63-1.54 (m, 2H), 1.02 (d, J = 7.5 Hz, 3H).
Minor isomer δ 4.56 (dd, J = 9.2, 7.5 Hz, 1H), 3.97 (dd, J = 9.2,
4.0 HZ, 1H), 3.80 (s, 3H), 3.26-3.23 (m, 1H), 2.75-2.71 (m, 1H),
2.02-1.93 (m, 2H), 1.71-1.69 (m, 1H), 1.23 (d, J = 6.9 Hz, 3H).;
13C NMR (125 MHz, CDCl3): δ Major isomer 175.4, 168.4, 73.1,
65.9, 52.9, 42.9, 42.5, 33.8, 31.3, 16.1. δ Minor isomer 173.7,
170.7, 63.0, 53.0, 46.0, 42.3, 35.5, 32.3, 14.6 (one carbon atom
was overlapped.).; FTIR (neat): 2957, 2877, 1770, 1726, 1454,
1435, 1378, 1243, 1167, 1145, 1053, 1004, 972, 955, 930, 797,
715, 667 cm-1.; HMRS m/z (DART) [M+H]+: calcd for C10H15O4:
199.0965; found: 199.0957.
cyclopenta[c]-furan-3a-carboxylate (2c)
The product was obtained in 50% yield (39.2 mg, 0.15 mmol)
after column chromatography on silica gel (n-hexane : EtOAc = 4
1
: 1) as a colorless oil.; H NMR (500 MHz, CDCl3): δ 7.36-7.22
(m, 5H), 4.46 (dd, J = 9.2, 6.3 Hz, 1H), 4.22 (dd, J = 9.2, 1.2 Hz,
1H), 3.81 (s, 3H), 3.08 (dd, J = 9.7, 6.3 Hz, 1H), 2.95-2.91 (m,
1H), 2.83-2.76 (m, 1H), 2.27-2.17 (m, 2H), 2.05-1.98 (m, 1H).;
13C NMR (125 MHz, CDCl3): δ 176.5, 170.3, 140.5, 128.9,
127.3, 127.2, 70.2, 61.0, 54.5, 53.3, 52.4, 35.4, 32.7.; FTIR
(neat): 2956, 1771, 17371603, 1496, 1453, 1435, 1375, 1265,
1242, 1190, 1149, 1088, 1070, 1057, 1026, 991, 963, 922, 820,
792, 753, 701 cm-1.; HMRS m/z (DART) [M+H]+: calcd for
C15H17O4: 261.1121; found: 261.1133.
4.3.8.
(3aRS,6aSR)-Methyl-1,1-dimethyl-3-oxotetrahydro-1H-
4.3.4. (3aRS,5RS,6aSR)-Methyl-3-oxo-5-methyltetrahydro-1H-
cyclopenta[c]-furan-3a-carboxylate (2d)
cyclopenta[c]-furan-3a-carboxylate (2h)
The product was obtained in 78% yield (50 mg, 0.23 mmol) after
The product was obtained in 66% yield (39 mg, 0.2 mmol) after
column chromatography on silica gel (n-hexane : EtOAc = 4 : 1)
column chromatography on silica gel (n-hexane : EtOAc = 4 : 1)
1
as a colorless oil.; H NMR (500 MHz, CDCl3): δ 3.80 (s, 3H),
1
as a colorless oil.; H NMR (500 MHz, CDCl3): δ 4.50 (dd, J =
2.91-2.88 (m, 1H), 2.35-2.25 (m, 2H), 1.90-1.77 (m, 2H), 1.61-
1.52 (m, 1H), 1.47 (s, 3H), 1.41 (s, 3H).; 13C NMR (125 MHz,
CDCl3): δ 175.3, 171.8, 84.9, 63.8, 54.5, 53.1, 36.8, 30.3, 30.0,
26.6, 24.2.; FTIR (neat): 2956, 2873, 1761, 1729, 1649, 1435,
1389, 1374, 1328, 1256, 1222, 1179, 1160, 1104, 1058, 1037,
1000, 980, 960, 932, 922, 909, 876, 804, 786, 731 cm-1.; HMRS
m/z (DART) [M+H]+: calcd for C11H17O4: 213.1121; found:
213.1115.
9.2, 6.9 Hz, 1H), 4.16 (dd, J = 9.3, 1.2 Hz, 1H), 3.77 (s, 6H),
3.06-3.03 (m, 1H), 2.77-2.72 (m, 1H), 2.24-2.13 (m, 2H), 1.68-
1.64 (m, 1H), 1.24-1.17 (m, 1H), 1.05 (d, J = 6.3 Hz, 3H).; 13C
NMR (125 MHz, CDCl3): δ 176.7, 170.6, 71.5, 61.1, 53.1, 47.5,
41.9, 41.4, 36.4, 18.6.; FTIR (neat): 2957, 2873, 1768, 1739,
1458, 1435, 1377, 1300, 1260, 1246, 1204, 1145, 1109, 1084,
1067, 1050, 1015, 985, 950, 844, 788, 722, 669 cm-1.; HMRS m/z
(DART) [M+H]+: calcd for C10H15O4: 199.0965; found: 199.0957.
4.3.9.
(1RS,3aRS,6aSR)-Methyl-1-phenyl-3-oxotetrahydro-
4.3.5.
(3aRS,5RS,6aSR)-Methyl-3-oxo-5-allyltetrahydro-1H-
1H-cyclopenta[c]-furan-3a-carboxylate (2i)
cyclopenta[c]-furan-3a-carboxylate (2e)
The product was obtained in 71% yield (42.3 mg, 0.21 mmol) for
the E isomer and 68% yield (40.1 mg, 0.2 mmol) for the Z isomer
after column chromatography on silica gel (n-hexane : EtOAc = 4
: 1) as a colorless oil.; 1H NMR (500 MHz, CDCl3): Major
isomer δ 4.27 (dq, J = 6.3, 4.0 Hz, 1H), 3.79 (s, 3H), 2.79-2.77
(m, 1H), 2.37-2.32 (m, 1H), 2.29-2.23 (m, 1H), 2.00-1.94 (m,
1H), 1.88-1.56 (m, 2H), 1.47 (d, J = 6.3 Hz, 3H). Minor isomer δ
4.89 (quin, J = 6.3 Hz, 1H), 3.78 (s, 3H), 2.95 (dd, J = 7.5, 6.3
Hz, 1H), 2.43-2.38 (m, 1H), 2.29-2.23 (m, 1H), 1.89-1.56 (m,
4H), 1.40 (d, J = 6.3 Hz, 1H).; 13C NMR (125 MHz, CDCl3): δ
Major isomer 175.9, 171.1, 82.4, 62.6, 53.1, 52.2, 35.4, 33.9,
25.7, 22.0. Minor isomer δ 176.0, 170.6, 63.8, 53.0, 50.7, 34.3,
27.1, 26.4, 16.1 (one carbon atom was overlapped.).; FTIR
(neat): 2956, 2873, 1765, 1737, 1450, 1435, 1384, 1352, 1253,
1207, 1162, 1128, 1108, 1059, 1039, 992, 976, 936, 913, 803,
733, 660 cm-1.; HMRS m/z (DART) [M+H]+: calcd for C10H15O4:
199.0965; found: 199.0963. Data was consisted with the
literature.8i
The product was obtained in 94% yield (63.1 mg 0.28 mmol)
after column chromatography on silica gel (n-hexane : EtOAc = 4
: 1) as a colorless oil.; 1H NMR (500 MHz, CDCl3): δ 5.74 (tdd, J
= 17.0, 10.0, 6.8 Hz, 1H), 5.05-4.99 (m, 2H), 4.50 (dd, J = 9.2,
6.3 Hz, 1H), 4.16 (dd, J = 9.2, 1.7 Hz, 1H), 3.77 (s, 3H), 3.07-
3.02 (m, 1H), 2.76-2.72 (m, 1H), 2.26-2.09 (m, 4H), 1.73 (dd, J =
14.3, 9.7 Hz, 1H), 1.27-1.20 (m, 1H).; 13C NMR (125 MHz,
CDCl3): δ 176.6, 170.5, 136.3, 116.2, 71.4, 60.7, 53.2, 47.1, 41.3,
39.4, 39.2, 38.3.; FTIR (neat): 2956, 2915, 1768, 1739, 1641,
1479, 1435, 1377, 1301, 1255, 1233, 1209, 1151, 1053, 986, 917,
846, 790, 728, 668 cm-1.; HMRS m/z (DART) [M+H]+: calcd for
C12H17O4: 225.1121; found: 225.1116. Data was consisted with
the literature.9e
4.3.6.
(3aRS,5RS,6aSR)-Methyl-3-oxo-5-phenyltetrahydro-
1H-cyclopenta[c]-furan-3a-carboxylate (2f)
The product was obtained in 53% yield (41.7 mg, 0.16 mmol)
after column chromatography on silica gel (n-hexane : EtOAc = 4
1
4.3.10. (1RS,3aRS,6aSR)-Methyl-1-methyl-3-oxotetrahydro-1H-
: 1) as a colorless oil.; H NMR (500 MHz, CDCl3): δ 7.33-7.21
cyclopenta[c]-furan-3a-carboxylate (2j)
(m, 5H), 4.58 (dd, J = 9.2, 6.3 Hz, 1H), 4.26 (dd, J = 9.2, 1.2 Hz,
1H), 3.82 (s, 3H), 3.34-3.26 (m, 1H), 3.21-3.16 (m, 1H), 3.06
(ddd, J = 13.8, 8.0, 1.7 Hz, 1H), 2.52-2.46 (m, 1H), 2.17 (dd, J =
13.8, 11.5 Hz, 1H), 1.78-1.70 (m, 1H).; 13C NMR (125 MHz,
CDCl3): δ 176.3, 170.4, 141.3, 128.6, 126.8, 128.8, 71.1, 60.5,
53.3, 47.3, 46.5, 40.8, 40.6.; FTIR (neat): 2956, 2349, 2326, 1769,
1239, 1711, 1603, 1496, 1435, 1378, 1256, 1238, 1222, 1204,
1148, 1116, 1100, 1060, 1030, 985, 935, 848, 755, 699, 672, 663
cm-1.; HMRS m/z (DART) [M+H]+: calcd for C15H17O4:
261.1121; found: 261.1129.
The product was obtained in 31% yield (24.3 mg, 0.093 mmol)
for the E isomer and 62% yield (48.5 mg, 0.19 mmol) for the Z
isomer after column chromatography on silica gel (n-hexane :
1
EtOAc = 4 : 1) as a colorless oil.; H NMR (500 MHz, CDCl3):
Major isomer δ 7.41-7.27 (m, 5H), 5.05 (d, J = 4.6 Hz, 1H), 3.72
(s, 3H), 3.15 (ddd, J = 7.0, 4.6, 1.9 Hz, 1H), 2.47-2.32 (m, 2H),
2.05-1.90 (m, 3H). Minor isomer δ 7.41-7.27 (m, 5H), 5.88 (d, J
= 6.9 Hz, 1H), 3.84 (s, 3H), 3.33-3.29 (ddd, J = 8.8, 6.9. 5.6 Hz,
1H), 2.48-2.35 (m, 2H), 1.70-1.50 (m, 3H), 1.30-1.24 (m, 1H);
13C NMR (125 MHz, CDCl3): Major isomer δ 175.9, 1708,
139.7, 128.7, 128.5, 125.4, 86.0, 54.3, 53.1, 35.2, 33.6, 25.5.
Minor isomer δ 175.9, 170.8, 136.4, 128.6, 128.0, 124.9, 81.4,
63.6, 53.2, 34.7, 28.5, 25.9.; FTIR (neat): 2955, 2872, 1769, 1738,
4.3.7.
(3aRS,6aSR)-Methyl-4-methyl-3-oxotetrahydro-1H-
cyclopenta[c]-furan-3a-carboxylate (2g)
The product was obtained in 68% yield (40.4 mg, 0.2 mmol) after
column chromatography on silica gel (n-hexane : EtOAc = 4 : 1)

7
2012, 18, 12267-12277. (e) lagtap, P. R.; Ford, L.; Deister, E.; Pohl,
1497, 1451, 1435, 1340, 1254, 1235, 1212, 1195, 1148, 1097,
1055, 1007, 924, 842, 766, 735, 718, 698 cm-1.; HMRS m/z
(DART) [M+H]+: calcd for C15H17O4: 261.1121; found: 261.1127.
Data was consisted with the literature.9a
ACCEPTED MANUSCRIPT
R.; Císařová, I.; Hodek, J.; Weber, J.; Mackman, R.; Bahador, G.; Jahn,
U. Chem. Eur. J. 2014, 20, 10298-10304. (f) Řehová, L.;
Dračinský,M.; Jahn, U. Org. Biomol. Chem. 2016, 14, 9612-9621.
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S. B.; Dombroski, M. J. Am. Chem. Soc. 1991, 113, 6607-6617.
(c) Bertrand, M. P.; Surzur, J.-M.; Oumar-Mahamat, H.;
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W. Chem. Commun. 2008, 2559-2561. (g) Curry, L.; Hallside, M.
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Acknowledgments
The authors are grateful to the Takeda Science Foundation and
the Sasagawa Scientific Research Foundation for their financial
support.
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Supplementary Material
Supplementary data associated with this article can be found
in the online version at doi: