A short synthesis of (+)-β-lycorane by asymmetric conjugate addition cascade

Article abstract of DOI:10.1016/j.tet.2015.03.014

Abstract The chiral diether ligand-controlled asymmetric conjugate addition of organolithiums to nona-2,7-dienedioate and subsequent intramolecular conjugate addition of the enolate intermediate gave all-trans trisubstituted cyclohexanes with high ee and

Full text of DOI:10.1016/j.tet.2015.03.014

Tetrahedron xxx (2015) 1e5
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Tetrahedron
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A short synthesis of (þ)-
b-lycorane by asymmetric conjugate
addition cascade
Katsumi Nishimura a, Naoshi Fukuyama a, Tomohisa Yasuhara a, Mitsuaki Yamashita a,
,b,
Takaaki Sumiyoshi a, Yasutomo Yamamoto b, Ken-ichi Yamada a, Kiyoshi Tomioka a
*
a Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan
b Faculty of Pharmaceutical Sciences, Doshisha Women’s College of Liberal Arts, Kodo, Kyotanabe 610-0395, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The chiral diether ligand-controlled asymmetric conjugate addition of organolithiums to nona-2,7-
dienedioate and subsequent intramolecular conjugate addition of the enolate intermediate gave all-
trans trisubstituted cyclohexanes with high ee and yields. Using this methodology, an efficient short
Received 28 December 2014
Received in revised form 10 February 2015
Accepted 3 March 2015
Available online xxx
asymmetric total synthesis of (þ)-
b
-lycorane was accomplished in 33% overall yield through five steps
from the dienedioate.
Ó 2015 Elsevier Ltd. All rights reserved.
Keywords:
Chiral ligand
Asymmetric synthesis
Organolithiums
Conjugate addition
Lycorane
1. Introduction
study to show the utility of this cascade reaction, here we report
a short asymmetric total synthesis of (þ)-
-lycorane (2b).6e8
b
The Amaryllidaceae alkaloids have attracted much attention due
to their rich bioactivities, such as anti-Alzheimer, antifungal, anti-
bacterial, and antineoplastic activities.1 Among these alkaloids,
lycorine (1)1,2 and its deoxygenated derivatives lycoranes (2a and
b)3 possess the characteristic pyrrolo-phenanthridine skeleton
(Fig. 1). We have previously reported the asymmetric total syn-
thesis of (ꢀ)-lycorine (1) using a chiral ligand-controlled asym-
metric conjugate addition cascade.4,5 As a continuation of this
Our strategy starts from the asymmetric conjugate addi-
tion9,10 of aryllithium 4 to nona-2,7-dienedioate 311,12 mediated
by chiral ligand 5 (Scheme 1). The subsequent intramolecular
Michael reaction of the resulting enolate 6 would afford tri-
substituted cyclohexane 7a with three contiguous stereogenic
centers.4 The nitrogen functionality could be introduced by
Curtius rearrangement, and the subsequent cyclization gives
(þ)-
b-lycorane (2b).
Fig. 1. Structures of lycorine and lycoranes.
Scheme 1. Synthetic strategy to (þ)-
b-lycorane.
* Corresponding author. Tel.: þ81 774 65 8676; fax: þ81 774 65 8658; e-mail
address: tomioka@pharm.kyoto-u.ac.jp (K. Tomioka).
http://dx.doi.org/10.1016/j.tet.2015.03.014
0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Nishimura, K.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.03.014

2
K. Nishimura et al. / Tetrahedron xxx (2015) 1e5
2. Results and discussion
intramolecular Michael reaction preferentially via conformer A and
lead to tt-7a, due to the absence of the 1,3-diaxial repulsion of the
alkenoate moiety, which exists in conformer B. Therefore, the lower
diastereoselectivity (4:1, Table 1, entry 6) than that in the pre-
viously reported reaction of 4 and 8 to give 9 (9:1)4 could be at-
tributed to the decreased 1,3-diaxial repulsion in conformer B (R¼H
vs ethylenedioxy).
First, the reaction of dienedioate 3 and phenyllithium was in-
vestigated as a model reaction. The reaction of PhLi (3 equiv) in the
presence of 5 (4.2 equiv) was complete within 0.5 h to give
trans,trans-cyclohexane tt-7b with 71% ee and trans,cis-cyclohex-
ane tc-7b with 3% ee in 50% and 9% yields, respectively (Table 1,
entry 1). The relative configuration of tt-7b was assigned based on
the trans-diaxial coupling between the two pairs of the adjacent
methine protons (J¼11.2 Hz each). The absolute configuration of tt-
7b was determined by conversion to a known compound with
established stereochemistry (see Supplementary data).
Table 1
Asymmetric conjugate addition cascadea
Entry
Ar
7
tt-7
tc-7
Scheme 2. Rationale for observed diastereoselectivity.
Yield (%)
ee (%)
Yield (%)
ee (%)
1
2
3
4
Ph
7b
7c
7d
7e
50
63
72
79
71b
68
9
7
16
4
3b
42
2-MeC6H4
2-i-PrC6H4
1-Naphthyl
The asymmetric total synthesis of (þ)-
b-lycorane (2b) was ac-
67b
81b
61
complished starting from tt-7a as shown in Scheme 3. Treatment of
tt-7a with HCl for 0.5 h in refluxing ethanol gave protodesilylated
half ester 10 in 98% yield. Interestingly and usefully, the carboxylic
acid at the C-2 position was not esterified, probably due to steric
hindrance.15 Curtius rearrangement using diphenylphosphoryl
azide (DPPA)16 followed by BischlereNapieralski-type cyclization
with polyphosphoric acid (PPA)17 converted 10 into lactam 11 via
an isocyanate intermediate in 70% yield. Finally, treatment of 11
with boraneedimethyl sulfide complex18 in refluxing THF induced
three sequential transformations: reduction of the lactam, lactam
formation between the resulting amine and the ester moiety, and
39b
5
7f
40
74
99
10
18
72
88
6
7a
68
a
All reactions were carried out using ArLi (3 equiv) and 5 (4.2 equiv).
The ee was determined after derivatization (see Supplementary data).
b
reduction of the resulting lactam to directly give (þ)-
b-lycorane
Toward the synthesis of (þ)-
b-lycorane, benzodioxol-5-
(2b) in 70% yield. 1H and 13C NMR,6c,6d and the specific rotation6d
were in good agreement with those reported. Notably, the asym-
metric total synthesis was accomplished through only five steps
from 3 in high overall yield (33%).
yllithium was employed in the cascade reaction. The reaction pro-
ceeded with comparable enantioselectivity, and tt-7f with 74% ee
was obtained in 40% yield along with tc-7f with 72% ee in 10% yield
(entry 5). Although tt-7c and 7d were obtained with the same level
of enantioselectivity (67e68% ee) in the reactions with 2-methyl-
and 2-isopropylphenyllithiums (entries 2 and 3), the enantiose-
lectivity was improved in the reaction with 1-naphthyllithium to
give tt-7e with 81% ee in 79% yield along with tc-7e with 39% ee in
4% yield (entry 4). Encouraged by this result, we utilized aryllithium
4, bearing a bulky TMS group at the ortho-position, in the reaction.
To our delight, tt-7a, which has all the carbon atoms and stereo-
chemistry required for the total synthesis, was obtained in 68%
yield with almost perfect enantioselectivity (99% ee; entry 6). In-
terestingly, the products were obtained in higher yields with the
more bulky aryllithiums (entries 1 and 5 vs 2e4 and 6). This is
explainable by decreased order of aggregation of the organolithium
compounds in solution by the steric hindrance.13 Unfortunately,
lowering the amount of the aryllithium, the enantiomeric excesses
of tt-7a and tc-7a were decreased to 85% and 54% (2 equiv), or to
50% and 27% (1.2 equiv), respectively, although the yield and the
diastereoselectivity were unchanged. These results indicate that
the lithium enolate that was generated by the conjugate addition
cascade would form a ternary complex with the aryllithium and
chiral ligand, which undergoes less enantioselective conjugate
addition.14 Importantly, chiral ligand 5 was quantitatively re-
covered without any loss of optical purity, and was reusable.
The diastereoselectivity of the cascade reaction is explainable as
shown in Scheme 2. The lithium enolate intermediate, which re-
sults from the conjugate addition of 4 to 3, would undergo the
Scheme 3. Asymmetric total synthesis of (þ)-
b-lycorane (2b).
3. Conclusion
This study revealed that the bulky TMS group at the ortho-po-
sition of aryllithium is effective to improve the enantioselectivity of
the chiral ligand-mediated asymmetric conjugate addition cascade
of nonadienedioate. Cyclohexanes bearing three contiguous sub-
stituents with trans,trans-configuration were obtained in high op-
tical purity. It was suggested that the 1,3-diaxial interaction would
play an important role in determining the diastereoselectivity. This
methodology enables the formation of two CeC bonds and three
stereogenic centers in one pot to give synthetically useful chiral
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K. Nishimura et al. / Tetrahedron xxx (2015) 1e5
3
cyclohexane derivatives. The utility of this methodology was clearly
demonstrated by the achievement of the shortest asymmetric total
OD-H, hexane/i-PrOH¼1000/1, 1 mL/min, 250 nm; major 9.5 min,
minor 7.5 min).
synthesis of (þ)-
b
-lycorane. Importantly, the chiral ligand could be
tc-7a: Rf¼0.5 (hexane/Et2O¼9/1, developed twice). ½a D25
þ11.7 (c
ꢂ
recycled, and the one-pot reactions are economically and ecologi-
1.32, CHCl3). 1H NMR: 0.41 (9H, s), 1.18 (9H, s), 1.1e1.3 (2H. m), 1.44
(9H, s), 1.52e1.62 (2H, m), 1.72e1.84 (2H, m), 2.38 (1H, dd, J¼4.6,
15.2), 2.53 (1H, dd, J¼3.7, 15.2), 2.71 (1H, m), 2.84 (1H, dd, J¼4.0,
11.8), 3.00 (1H, dt, J¼3.1, 11.8), 5.83 (2H, m), 6.66 (1H, d, J¼8.2), 6.71
(1H, d, J¼8.2). 13C NMR: 1.6 (CH3), 20.5 (CH2), 27.8 (CH3), 28.1 (CH3),
29.4 (CH2), 33.3 (CH), 34.2 (CH2), 37.0 (CH2), 38.5 (CH), 53.0 (CH),
79.7 (C), 80.0 (C), 99.6 (CH2), 108.6 (CH), 118.0 (CH), 118.9 (C), 143.9
(C), 144.4 (C), 152.5 (C), 172.4 (C), 172.6 (C). IR (neat): 1728. EIMS m/
z: 490 (Mþ). Anal. Calcd for C27H42O6Si: C, 66.09; H, 8.63. Found: C,
66.17; H, 8.70. The ee was determined by HPLC (Daicel Chiralcel OD-
H, hexane/i-PrOH¼1000/1, 1 mL/min, 250 nm; major 8.9 min, mi-
nor 7.5 min).
cally beneficial.
4. Experimental section
4.1. General
All melting points are uncorrected. Silica gel was used for col-
umn chromatography. 1H and 13C NMR (500 and 125 MHz, re-
spectively) were measured in CDCl3 unless otherwise mentioned.
Chemical shifts and coupling constants are presented in parts per
million
d relative to tetramethylsilane and Hertz, respectively. The
wavenumbers of maximum absorption peaks of IR spectroscopy are
presented in cmꢀ1. Chiral ligand 5 was prepared as previously
described.19
4.2.2. tert-Butyl (1S,2S,3S)-2-(tert-butoxycarbonyl)-3-
phenylcyclohexaneacetate (tt-7b) (Table 1, entry 1). Rf¼0.5 (hexane/
EtOAc¼9/1). A white solid of mp 70e72 ꢁC. 71% ee. ½a D25
þ14.0 (c 5.00,
ꢂ
4.1.1. Di-tert-butyl (2E,7E)-nona-2,7-dienedioate (3).11h To a stirred
suspension of tert-butyl triphenylphosphoranylideneacetate (161 g,
0.43 mol) in toluene (0.26 L) was added a solution of glutaralde-
hyde (17.2 g, 0.17 mol) in toluene (80 mL) at rt. After 21 h, the
mixture was filtered, and the residue was washed with hexane. The
combined filtrate and washings were concentrated and purified by
column chromatography (hexane/EtOAc¼20/1) to give the title
compound (53 g, 90%) as a colorless oil of bp 135e140 ꢁC/
0.2 mmHg: Rf¼0.4 (hexane/EtOAc¼9/1). 1H NMR: 1.48 (18H, s), 1.62
(2H, quintet, J¼7.3), 2.20 (4H, ddt, J¼1.5, 7.0, 7.3), 5.75 (2H, dt,
J¼15.6, 1.5), 6.83 (2H, dt, J¼15.6, 7.0). 13C NMR: 26.4 (CH2), 28.1
(CH3), 31.2 (CH2), 80.1 (C), 123.6 (CH), 146.8 (CH), 165.9 (C). IR
(neat): 1710, 1650. EIMS m/z: 223 (Mꢀ t-BuO). Anal. Calcd for
CHCl3). 1H NMR (C6D6): 1.12 (9H, s), 1.22e1.38 (3H, m), 1.41 (9H, s),
1.60 (1H, m),1.70 (1H, m), 2.02 (1H, m), 2.24 (1H, dd, J¼9.5,15.0), 2.34
(1H, t, J¼11.2), 2.40 (1H, m), 2.60 (1H, dd, J¼3.1, 15.0), 2.81 (1H, dt,
J¼3.4, 11.2), 7.05e7.20 (5H, m). 13C NMR (C6D6): 26.0 (CH2), 27.2 (CH3),
28.1 (CH3), 31.2 (CH2), 34.4 (CH2), 37.9 (CH), 40.7 (CH2), 48.3 (CH), 56.1
(CH), 79.5 (C), 79.8 (C), 126.6 (CH), 128.3 (CH), 128.3 (CH), 144.6 (C),
171.2 (C), 173.1 (C). IR (CHCl3): 1710. EIMS m/z: 374 (Mþ), 318, 262.
Anal. Calcd for C23H34O4: C, 73.76; H, 9.15. Found: C, 73.75; H, 9.33.
The ee was determined after reduction with LiAlH4. The absolute
configuration was determined after conversion into a known com-
pound (see Supplementary data).
4.2.3. tert-Butyl (1R,2S,3S)-2-(tert-butoxycarbonyl)-3-
C
17H28O4: C, 68.89; H, 9.52. Found: C, 68.87; H, 9.57. 1H NMR and IR
phenylcyclohexaneacetate (tc-7b) (Table 1, entry 1). Rf¼0.6 (hex-
spectra were in agreement with those reported,11h while 13C NMR
had slight difference; 26.4 (CH2) instead of reported 29.7 (CH2).
ane/EtOAc¼9/1). A white solid of mp 90e95 ꢁC. 3% ee. ½a D25
ꢂ
e19.8 (c
2.04, CHCl3). 1H NMR: 1.15 (9H, s), 1.34e1.40 (1H, m), 1.45 (9H, s),
1.58e1.62 (3H, m), 1.79 (1H, m), 1.87 (1H, m), 2.45 (1H, dd, J¼9.8,
15.6), 2.50 (1H, dd, J¼4.9,15.6), 2.73 (1H, m), 2.82 (2H, m), 7.15e7.25
(5H, m). 13C NMR: 20.6 (CH2), 27.7 (CH3), 28.1 (CH3), 29.5 (CH2), 32.8
(CH), 34.2 (CH2), 35.0 (CH2), 40.9 (CH), 52.6 (CH), 80.1 (C), 80.2 (C),
126.1 (CH), 127.4 (CH), 128.1 (CH), 145.2 (C), 172.4 (C), 172.9 (C). IR
(CHCl3): 1710. EIMS m/z: 374 (Mþ), 318, 262. Anal. Calcd for
4.2. Asymmetric conjugate addition cascade (Table 1)
4.2.1. General Procedure. (1S,2S,3S)- and (1R,2S,3S)-tert-butyl 2-tert-
butoxycarbonyl-3-(4-trimethylsilylbenzo[1,3]dioxol-5-yl)cyclo-
hexaneacetate (tt-7a and tc-7a) (Table 1, entry 3). To a solution of 5
(10.2 g, 42 mmol) and 3,4-methylenedioxy-2-trimethyl-
silylbromobenzene20 (8.19 g, 30 mmol) in toluene (280 mL) was
added a solution of t-BuLi (1.69 M; 16.6 mL, 28 mmol) in pentane at
ꢀ78 ꢁC, and the resulting solution was stirred for 1 h at the same
temperature. A solution of 3 (2.96 g, 10 mmol) in toluene (20 mL)
was added at ꢀ78 ꢁC, and the mixture was stirred for 10 min at the
same temperature. The reaction was quenched by the addition of
saturated NH4Cl. The organic layer was separated, and the aqueous
layer was extracted with Et2O. The combined organic layers were
successively washed with saturated NaHCO3 and brine, dried over
Na2SO4, and concentrated. Column chromatography (hexane/
Et2O¼30/1) gave tt-7a (3.31 g, 68%) with 99% ee and tc-7a (860 mg,
18%) with 88% ee as colorless oils, and 5 (10.2 g, quantitative re-
covery) as a colorless solid.
C23H34O4: C, 73.76; H, 9.15. Found: C, 73.89; H, 9.00. The ee was
determined after conversion to the corresponding dimethyl ester
(see Supplementary data).
4.2.4. (1S,2S,3S)-tert-Butyl
2-(tert-butoxycarbonyl)-3-(2-methyl-
phenyl)cyclohexanacetate (tt-7c) (Table 1, entry 2). Rf¼0.5 (hexane/
Et2O¼9/1, developed twice). A colorless oil. 68% ee (HPLC: Daicel
Chiralcel OD-H ꢃ 2 were connected, hexane/i-PrOH¼100/1, 1 mL/
min, 254 nm; major 37.5 min, minor 33.2 min). ½a D25
þ13.4 (c 2.16,
ꢂ
CHCl3). 1H NMR: 1.07 (9H, s), 1.17 (1H, m), 1.33 (1H, m), 1.46 (9H, s),
1.56 (1H, m), 1.81 (2H, m), 1.94 (1H, m), 2.05 (1H, dd, J¼10.1, 14.7),
2.15 (1H, m), 2.32 (1H, dd, J¼3.4, 14.7), 2.32 (3H, s), 2.36 (1H, t,
J¼10.7), 3.06 (1H, dt, J¼3.4, 11.9), 7.04e7.22 (4H, m). 13C NMR: 19.6
(CH3), 25.9 (CH2), 27.5 (CH3), 28.1 (CH3), 31.0 (CH2), 33.7 (CH2), 37.5
(CH), 40.5 (CH2), 42.1 (CH), 55.5 (CH), 79.9 (C), 80.2 (C), 125.8 (CH),
125.9 (CH), 126.4 (CH), 130.0 (CH), 135.5 (C), 142.1 (C), 171.7 (C),
173.6 (C). IR (neat): 1720. EIMS m/z: 388 (Mþ), 332, 276. Anal. Calcd
for C24H36O4: C, 74.19; H, 9.34. Found: C, 73.91; H, 9.47.
tt-7a: Rf¼0.4 (hexane/Et2O¼9/1, developed twice). ½a D25
þ16.8 (c
ꢂ
1.26, CHCl3). 1H NMR: 0.35 (9H, s), 1.07 (9H, s), 1.07e1.20 (1H, m),
1.20e1.34 (2H, m), 1.42 (9H, s), 1.72e1.82 (2H, m), 1.89 (1H, m), 2.01
(1H, dd, J¼9.8, 14.4), 2.05 (1H, m), 2.27 (1H, dd, J¼2.4, 14.4), 2.33
(1H, t, J¼11.0), 2.97 (1H, dt, J¼1.8, 11.0), 5.78 (2H, m), 6.68e6.76 (2H,
m). 13C NMR: 1.5 (CH3), 25.5 (CH2), 27.6 (CH3), 28.0 (CH3), 30.6
(CH2), 36.1 (CH2), 37.6 (CH), 40.2 (CH2), 45.4 (CH), 55.4 (CH), 79.6
(C), 80.1 (C), 99.4 (CH2), 108.5 (CH), 119.0 (C), 120.1 (CH), 142.5 (C),
144.0 (C), 152.2 (C), 171.4 (C), 173.3 (C). IR (neat): 1728. EIMS m/z:
490 (Mþ). Anal. Calcd for C27H42O6Si: C, 66.09; H, 8.63. Found: C,
65.92; H, 8.70. The ee was determined by HPLC (Daicel Chiralcel
4.2.5. (1R,2S,3S)-tert-Butyl
2-(tert-butoxycarbonyl)-3-(2-methyl-
phenyl)cyclohexanacetate (tc-7c) (Table 1, entry 2). Rf¼0.6 (hexane/
Et2O¼9/1, developed twice). A colorless solid of mp 60e75 ꢁC. 42%
ee (HPLC: Daicel Chiralcel OG, hexane/i-PrOH¼500/1, 0.5 mL/min,
254 nm; major 10.8 min, minor 15.8 min). ½a D25
ꢂ
e8.28 (c 0.79,
CHCl3). 1H NMR: 1.12 (9H, s), 1.19e1.27 (2H, m), 1.46 (9H, s),
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4
K. Nishimura et al. / Tetrahedron xxx (2015) 1e5
1.59e1.63 (2H, m), 1.79e1.81 (2H, m), 2.36 (3H, s), 2.47 (1H, dd,
J¼4.9, 15.3), 2.52 (1H, dd, J¼3.4, 14.7), 2.76 (1H, m), 2.92 (1H, dd,
J¼4.0, 12.2), 3.05 (1H, dt, J¼3.7, 12.2), 7.02e7.15 (4H, m). 13C NMR:
19.6 (CH3), 20.8 (CH2), 27.6 (CH3), 28.1 (CH3), 29.5 (CH2), 33.1 (CH),
34.0 (CH2), 34.1 (CH2), 35.3 (CH), 52.5 (CH), 80.0 (C), 80.2 (C), 124.8
(CH), 125.6 (CH), 126.0 (CH), 130.1 (CH), 135.6 (C), 143.5 (C), 172.4
(C), 172.9 (C). IR (Nujol): 1730, 1710. EIMS m/z: 388 (Mþ), 332, 276.
Anal. Calcd for C24H36O4: C, 74.19; H, 9.34. Found: C, 73.96; H, 9.38.
hexane/i-PrOH¼100/1, 1 mL/min, 250 nm; major 6.3 min, minor
7.0 min). ½a 2D5
ꢂ
þ15.2 (c 1.24, CHCl3). 1H NMR: 1.10 (9H, s), 1.0e1.4
(3H, m), 1.38 (9H, s), 1.70e1.78 (2H, m), 1.84 (1H, m), 1.95 (1H, dd,
J¼9.8, 14.6), 2.03 (1H, m), 2.11 (1H, t, J¼11.0), 2.22 (1H, dd, J¼2.7,
14.6), 2.60 (1H, dt, J¼2.4,11.0), 5.81 (2H, m), 6.55 (1H, m), 6.60e6.63
(2H, m). 13C NMR: 25.5 (CH2), 27.6 (CH3), 28.0 (CH3), 30.7 (CH2), 34.1
(CH2), 37.3 (CH), 40.3 (CH2), 47.3 (CH), 56.3 (CH), 79.8 (C), 80.0 (C),
100.5 (CH2), 107.7 (CH), 107.9 (CH), 120.7 (CH), 137.9 (C), 145.8 (C),
147.2 (C), 171.4 (C), 173.1 (C). IR (neat): 1728. EIMS m/z: 418 (Mþ).
Anal. Calcd for C24H34O6: C, 68.87; H, 8.19. Found: C, 69.01; H, 8.40.
4.2.6. (1S,2S,3S)-tert-Butyl 2-(tert-butoxycarbonyl)-3-(2-
isopropylphenyl)cyclohexanacetate (tt-7d) (Table 1, entry 3). Rf¼0.4
(hexane/EtOAc¼9/1). A colorless oil. 67% ee. ½a D25
ꢂ
þ17.9 (c 5.11,
4.2.10. (1R,2S,3S)-tert-Butyl 2-tert-butoxycarbonyl-3-(benzo[1,3]di-
oxol-5-yl)cyclohexaneacetate (tc-7f) (Table 1, entry 5). Rf¼0.6
(hexane/Et2O¼4/1). A colorless oil. 72% ee (HPLC: Daicel Chiralcel
OD-H, hexane/i-PrOH¼100/1, 1 mL/min, 250 nm; major 6.2 min,
CHCl3). 1H NMR: 1.05 (9H, s), 1.17 (3H, d, J¼6.7), 1.25 (3H, d, J¼6.7),
1.27e1.52 (3H, m), 1.46 (9H, s), 1.82 (1H, m), 1.95 (1H, m), 2.05 (1H,
dd, J¼9.8, 14.7), 2.16 (1H, m), 2.31 (1H, dd, J¼3.1, 14.7), 2.41 (1H, t,
J¼11.0), 3.17 (1H, dt, J¼3.1, 11.0), 3.29 (1H, septet, J¼6.7), 7.10e7.26
(4H, m). 13C NMR: 23.2 (CH3), 24.6 (CH3), 26.0 (CH2), 27.5 (CH3),
28.12 (CH), 28.14 (CH3), 30.9 (CH2), 35.0 (CH2), 37.7 (CH), 40.5 (CH2),
41.3 (CH), 55.5 (CH), 79.9 (C), 80.2 (C), 124.8 (CH), 125.3 (CH), 126.2
(CH), 126.9 (CH), 140.7 (C), 146.0 (C), 171.6 (C), 173.7 (C). IR (neat):
1720. EIMS m/z: 416 (Mþ), 360, 304. Anal. Calcd for C26H40O4: C,
74.96; H, 9.68. Found: C, 75.17; H, 9.83. The ee was determined after
reduction with LiAlH4 (see Supplementary data).
minor 7.1 min). ½a D25
ꢂ
e20.1 (c 1.78, CHCl3). 1H NMR: 1.21 (9H, s),
1.2e1.4 (2H, m), 1.44 (9H, s), 1.5e1.7 (2H, m), 1.76 (1H, m), 1.84 (1H,
m), 2.42 (1H, dd, J¼9.5, 15.6), 2.48 (1H, dd, J¼4.3, 15.6), 2.68e2.78
(3H, m), 5.89 (2H, m), 6.64 (1H, m), 6.69e6.71 (2H, m). 13C NMR:
20.5 (CH2), 27.8 (CH3), 28.1 (CH3), 29.5 (CH2), 32.8 (CH), 34.2 (CH2),
35.2 (CH2), 40.5 (CH), 52.8 (CH), 80.10 (C), 80.12 (C), 100.7 (CH2),
107.8 (CH), 107.9 (CH), 120.2 (CH), 139.3 (C), 145.6 (C), 147.3 (C),
172.4 (C), 172.7 (C). IR (neat): 1728. EIMS m/z: 418 (Mþ). Anal. Calcd
for C24H34O6: C, 68.87; H, 8.19. Found: C, 68.66; H, 8.22.
4.2.7. (1R,2S,3S)-tert-Butyl 2-(tert-butoxycarbonyl)-3-(2-
isopropylphenyl)cyclohexanacetate
(tc-7d)
(Table
1,
entry
4.3. Asymmetric total synthesis of (D)-b-lycorane (Scheme 3)
3). Rf¼0.5 (hexane/EtOAc¼9/1). A colorless solid of mp 79e81 ꢁC.
61% ee (HPLC: Daicel Chiralcel AD, hexane/i-PrOH¼100/1, 0.5 mL/
4.3.1. (1S,2S,6S)-2-(Benzo[1,3]dioxol-5-yl)-6-ethoxycarbonyl-meth-
ylcyclohexanecarboxylic acid (10). To a solution of tt-7a (2.94 g,
6.0 mmol) in EtOH (2 mL) was added anhydrous 35% HCl in EtOH
(20 mL) at rt, and the mixture was heated under reflux for 0.5 h.
Water was added at 0 ꢁC, and the whole was extracted with Et2O.
The organic layer was washed with brine, dried over Na2SO4, and
concentrated. Column chromatography (hexane/EtOAc¼4/1) gave
the title compound (2.03 g, 98%) as colorless needles of mp
min, 254 nm; major 9.3 min, minor 8.2 min). ½a D25
ꢂ
e15.1 (c 0.56,
CHCl3). 1H NMR: 1.13 (9H, s), 1.20 (3H, d, J¼6.7), 1.29 (3H, d, J¼6.7),
1.46 (9H, s), 1.59e1.67 (4H, m), 1.79e1.82 (2H, m), 2.52 (1H, dd,
J¼10.4, 15.6), 2.57 (1H, dd, J¼4.3, 15.6), 2.76 (1H, m), 2.92 (1H, dd,
J¼4.3, 11.9), 3.17 (1H, dt, J¼3.4, 11.9), 3.32 (1H, septet, J¼6.7),
7.08e7.25 (4H, m). 13C NMR: 20.7 (CH2), 23.6 (CH3), 24.3 (CH3), 27.7
(CH3), 28.0 (CH), 28.1 (CH3), 29.5 (CH2), 33.0 (CH), 33.9 (CH2), 34.5
(CH), 35.4 (CH2), 52.5 (CH), 79.8 (C), 80.1 (C), 125.0 (CH), 125.2 (CH),
125.4 (CH), 126.0 (CH), 141.7 (C), 146.1 (C), 172.5 (C), 172.8 (C). IR
(Nujol): 1710. EIMS m/z: 416 (Mþ), 360, 304. Anal. Calcd for
90e91 ꢁC: Rf¼0.4 (hexane/EtOAc¼4/1). ½a 2D5
þ39.6 (c 1.00, CHCl3).
ꢂ
1H NMR: 1.11 (1H, m), 1.23 (3H, t, J¼7.0), 1.36e1.51 (2H, m),
1.82e1.90 (3H, m), 2.11e2.19 (2H, m), 2.26 (1H, t, J¼11.0), 2.36 (1H,
m), 2.71 (1H, dt, J¼2.8, 11.0), 4.09 (2H, q, J¼7.0), 5.89 (2H, s), 6.59
(1H, dd, J¼1.5, 7.9), 6.64e6.68 (2H, m). 13C NMR: 14.1 (CH3), 25.4
(CH2), 30.9 (CH2), 33.7 (CH2), 37.0 (CH), 39.4 (CH2), 46.6 (CH), 55.7
(CH), 60.4 (CH2), 100.7 (CH2), 107.4 (CH), 108.0 (CH), 120.4 (CH),
137.4 (C), 146.1 (C), 147.5 (C), 172.1 (C), 179.6 (C). IR (Nujol):
2800e3300, 1720, 1685. EIMS m/z: 334 (Mþ), 288, 201, 135. Anal.
Calcd for C18H22O6: C, 64.66; H, 6.63. Found: C, 64.61; H, 6.55.
C
26H40O4: C, 74.96; H, 9.68. Found: C, 74.69; H, 9.66.
4.2.8. (1S,2S,3S)- and (1R,2S,3S)-tert-Butyl 2-(tert-butoxycarbonyl)-
3-(naphthalen-1-yl)cyclohexanacetate (tt-7e and tc-7e) (Table 1,
entry 4). Rf¼0.6 (hexane/EtOAc¼9/1, developed twice). A colorless
oil. A 79:4 mixture of tt-7e with 81% ee and tc-7e with 39% ee. ½a D25
ꢂ
e16.3 (c 5.00, CHCl3). 1H NMR: 0.88 (9H, s), 0.98 (1.8H, s), 1.21e1.29
(1H, m), 1.44e1.50 (1H, m), 1.48 (9H, s), 1.59 (1.8H, s), 1.66 (1H, m),
1.89 (1H, m), 2.01 (1H, m), 2.12 (1H, dd, J¼10.0, 15.0), 2.27 (1H, m),
2.38 (1H, dd, J ¼ 3.4, 15.0), 2.51 (0.2H, dd, J¼4.0, 15.3), 2.55 (1H, t, J ¼
11.0), 2.65 (0.2H, dd, J ¼ 11.0, 15.3), 2.86 (0.2H, m), 3.14 (0.2H, dd,
J¼4.3, 11.9), 3.74 (1H, dt, J¼3.4, 11.0), 7.41e7.51 (4H, m), 7.30e7.50
(1.0H, m), 7.67 (0.2H, d, J¼7.9), 7.68 (1H, d, J¼7.9), 7.81 (1H, d, J¼8.1),
7.82 (0.2H, d, J¼8.0), 8.16 (1H, d, J¼8.6). 13C NMR: (tt-7e) 26.0 (CH2),
27.3 (CH3), 28.1 (CH3), 31.2 (CH2), 34.5 (CH2), 37.9 (CH), 40.5 (CH2),
40.9 (CH), 56.0 (CH), 80.0 (C), 80.2 (C), 123.1 (CH), 123.7 (CH), 125.2
(CH), 125.3 (CH), 125.7 (CH), 126.6 (CH), 128.6 (CH), 131.5 (C), 133.8
(C), 140.4 (C), 171.7 (C), 173.1 (C); (tc-7e) 20.9 (CH2), 27.5 (CH3), 29.5
(CH2), 33.4 (CH), 34.3 (CH2), 34.9 (CH2), 52.5 (CH), 80.1 (C), 123.0
(CH),125.3 (CH),126.4 (CH),128.8 (CH),131.6 (C),133.8 (C),141.8 (C),
172.3 (C), 172.8 (C). IR (neat): 1720. EIMS m/z: 424 (Mþ), 368, 312.
Anal. Calcd for C27H36O4: C, 76.38; H, 8.55. Found: C, 76.61; H, 8.64.
The ee was determined after reduction with LiAlH4 (see
Supplementary data).
4.3.2. (4S,4aR,11bR)-Ethyl (6-oxo-1,2,3,4,4a,5,6,11b-octahydro-[1,3]
dioxolo[4,5-j]phenanthridin-4-yl)acetate (11). To a solution of 10
(1.84 g, 5.5 mmol) in toluene (16 mL) were added diphenylphos-
phoryl azide (1.3 mL, 6 mmol) and Et3N (0.92 mL, 6.6 mmol) at 0 ꢁC.
The whole was heated under reflux for 0.5 h. After cooled to rt, the
mixture was concentrated in vacuo to give colorless oil, which in-
dicated the absorbance at 2250 cme1 in the IR spectrum. To the
above oil was added PPA (10 mL) at 0 ꢁC, and the whole was stirred
for 0.5 h at rt. Water was added, and the mixture was extracted
with CHCl3. The organic layer was successively washed with water,
saturated NaHCO3, and brine, dried over Na2SO4, and concentrated.
Column chromatography (CHCl3/EtOAc¼4/1), followed by re-
crystallization from EtOH gave the title compound (1.28 g, 70%) as
colorless needles of mp 205e206 ꢁC: Rf¼0.3 (CHCl3/EtOAc¼4/1).
½
a 2D5
ꢂ
þ72.7 (c 1.06, CHCl3). 1H NMR: 1.17e1.36 (2H, m), 1.29 (3H, t,
J¼7.0), 1.52 (1H, m), 1.90e1.94 (2H, m), 2.05 (1H, m), 2.27 (1H, dd,
J¼7.0, 15.9), 2.34 (1H, m), 2.60 (1H, dd, J¼5.0, 15.9), 2.71 (1H, dt,
J¼3.7, 11.6), 3.03 (1H, t, J¼11.6), 4.19 (2H, q, J¼7.0), 6.00 (2H, m), 6.73
(1H, brs), 6.76 (1H, s), 7.51 (1H, s). 13C NMR: 14.1 (CH3), 24.5 (CH2),
26.9 (CH2), 31.3 (CH2), 37.7 (CH), 37.8 (CH2), 41.6 (CH), 59.6 (CH),
4.2.9. (1S,2S,3S)-tert-Butyl 2-tert-butoxycarbonyl-3-(benzo[1,3]di-
oxol-5-yl)cyclohexaneacetate (tt-7f) (Table 1, entry 5). Rf¼0.5 (hex-
ane/Et2O¼4/1). A colorless oil. 74% ee (HPLC: Daicel Chiralcel OD-H,
Please cite this article in press as: Nishimura, K.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.03.014

K. Nishimura et al. / Tetrahedron xxx (2015) 1e5
5
7. Our other approaches for lycoranes: (a) Yasuhara, T.; Nishimura, K.; Yamashita,
M.; Fukuyama, N.; Yamada, K.; Muraoka, O.; Tomioka, K. Org. Lett. 2003, 5,
1123e1126; (b) Yasuhara, T.; Osafune, E.; Nishimura, K.; Yamashita, M.; Yamada,
K.; Muraoka, O.; Tomioka, K. Tetrahedron Lett. 2004, 45, 3043e3045.
8. Our total syntheses of other Amaryllidaceae alkaloids: (a) Tomioka, K.; Koga, K.;
Yamada, S. Chem. Pharm. Bull. 1977, 25, 2681e2688; (b) Shimizu, K.; Tomioka,
K.; Yamada, S.; Koga, K. Chem. Pharm. Bull. 1978, 26, 3765e3771; (c) Yamada, K.;
Mogi, Y.; Mohamed, M. A.; Takasu, K.; Tomioka, K. Org. Lett. 2012, 14,
5868e5871.
60.7 (CH2), 101.4 (CH2), 103.9 (CH), 107.9 (CH), 123.2 (C), 138.0 (C),
146.4 (C), 151.0 (C), 165.8 (C), 172.6 (C). IR (Nujol): 3200, 1735, 1660.
EIMS m/z: 331 (Mþ), 243, 216, 202. Anal. Calcd for C18H21NO5: C,
65.24; H, 6.39; N, 4.23. Found: C, 65.02; H, 6.34; N, 4.25.
4.3.3. (þ)-
in THF (100 mL) was added BH3,SMe2 (10 M; 1.0 mL, 10 mmol) at
ꢁC, and the mixture was heated under reflux for 3 d. To the
b-lycorane (2b). To a solution of 11 (662 mg, 2.0 mmol)
9. (a) Tomioka, K. Synthesis 1990, 541e549; (b) Kanai, M.; Shibasaki, M. In Cata-
lytic Asymmetric Synthesis; Ojima, I., Ed.; VCH: Weinheim, Germany, 2000;
pp 569e592; (c) Sibi, M. P.; Manyem, S. Tetrahedron 2000, 56, 8033e8061; (d)
0
mixture was added 10% NaOH at 0 ꢁC, and the whole was extracted
with toluene. The organic layer was washed with brine, dried over
Na2SO4, and concentrated. Column chromatography (EtOAc/
EtOH¼4/1) gave the title compound (442 mg, 70%) as colorless
plates of mp 72e73 ꢁC (lit.3,6d mp 72e73 ꢁC): Rf¼0.4 (EtOAc/
€
Krause, N.; Hoffmann-Roder, A. Synthesis 2001, 171e196; (e) Feringa, B. L.;
Naasz, R.; Imbos, R.; Arnold, L. A. In Modern Organocopper Chemistry; Krause, N.,
Ed.; Wiley-VCH: Weinheim, Germany, 2002; chapter 7; (f) Hayashi, T.; Yama-
saki, K. Chem. Rev. 2003, 103, 2829e2844; (g) Tomioka, K. In Comprehensive
Asymmetric Catalysis, Supplement; Jacobsen, E. N., Pfaltz, A., Yamamoto, H., Eds.;
Springer: 2004; Chapter 31.1, pp 109e124; (h) Yamataka, H.; Yamada, K.; To-
mioka, K. In The Chemistry of Organolithium Compounds; Rappoport, Z., Marek, I.,
Eds.; Wiley: 2004, Part 1, Chapter 14; (i) Christoffers, J.; Koripelly, G.; Rosiak, A.;
EtOH¼4/1). [
a
]
D
20 þ153 (c 1.02, EtOH); lit. [
a
]
20 ꢀ143.3 (c 1.04, EtOH)
D
for the enantiomer,3 [
a
]
20 þ142.5 (c 0.17, EtOH).6d 1H NMR: 1.1e1.2
D
(2H, m), 1.35e1.55 (2H, m), 1.51 (1H, t, J¼10.5), 1.65 (1H, m),
1.9e2.05 (3H, m), 2.26e2.35 (2H, m), 2.50 (1H, t, J¼10.5), 3.33 (1H,
d, J¼14.3), 3.38 (1H, dt, J¼5.5, 9.0), 4.06 (1H, d, J¼14.3), 5.87 (1H,
brs), 5.88 (1H, brs), 6.50 (1H, s), 6.71 (1H, s). 13C NMR: 26.4 (CH2),
28.2 (CH2), 28.8 (CH2), 30.0 (CH2), 41.7 (CH), 42.9 (CH), 53.8 (CH2),
57.2 (CH2), 71.8 (CH), 100.6 (CH2), 105.3 (CH), 106.8 (CH), 128.4 (C),
131.2 (C), 145.6 (C), 146.1 (C). IR (CHCl3): 2928, 1593, 1485. EIMS m/
z: 257 (Mþ). 1H NMR and 13C NMR are in good agreement with
those reported in ref 6c and 6d, respectively, while there are slight
differences in 1H NMR and IR from those reported in ref 6d, prob-
ably due to a misprint; ours 1.9e2.05 (3H, m) instead of reported
1.93e1.98 (2H, m) and 3.23 (1H, m), and ours 1593 cme1 instead of
reported 1724 cme1, respectively.
€
Rossle, M. Synthesis 2007, 1279e1300; (j) Tomioka, K.; Yamamoto, Y.; Yamada,
K. In Comprehensive Chirality; Carreira, E. M., Yamamoto, H., Eds.; Elsevier:
2012; Vol. 4, pp 122e131.
10. (a) Asano, Y.; Iida, A.; Tomioka, K. Tetrahedron Lett. 1997, 38, 8973e8976; (b)
Asano, Y.; Iida, A.; Tomioka, K. Chem. Pharm. Bull. 1998, 46, 184e186; (c) Asano,
Y.; Yamashita, M.; Nagai, K.; Kuriyama, M.; Yamada, K.; Tomioka, K. Tetrahedron
Lett. 2001, 42, 8493e8495.
11. Diastereoselective conjugate addition cascades of dienedioates: (a) Saito, S.;
Hirohara, Y.; Narahara, O.; Moriwake, T. J. Am. Chem. Soc. 1989, 111, 4533e4535;
(b) Saito, S.; Hara, T.; Naka, K.; Hayashi, T.; Moriwake, T. Synlett 1992, 241e243;
(c) Klimko, P. G.; Singleton, D. A. J. Org. Chem. 1992, 57, 1733e1740; (d) Uyehara,
T.; Shida, N.; Yamamoto, Y. J. Org. Chem. 1992, 57, 3139e3145; (e) Shida, N.;
Uyehara, T.; Yamamoto, Y. J. Org. Chem. 1992, 57, 5049e5051; (f) Yoshii, E.; Hori,
K.; Nomura, K.; Yamaguchi, K. Synlett 1995, 568e571; (g) Urones, J. G.; Garrido,
N. M.; Díez, D.; Dominguez, S. H.; Davies, S. G. Tetrahedron: Asymmetry 1997, 8,
2683e2685; (h) Davies, S. G.; Díez, D.; Dominguez, S. H.; Garrido, N. M.; Kru-
chinin, D.; Price, P. D.; Smith, A. D. Org. Biomol. Chem. 2005, 3, 1284e1301.
12. Our other approaches of conjugate addition-triggered cascade reactions: (a)
Nagaoka, Y.; Tomioka, K. Org. Lett. 1999, 1, 1467e1469; (b) Ono, M.; Nishimura,
K.; Nagaoka, Y.; Tomioka, K. Tetrahedron Lett. 1999, 40, 6979e6982; (c) Ono, M.;
Nishimura, K.; Tsubouchi, H.; Nagaoka, Y.; Tomioka, K. J. Org. Chem. 2001, 66,
8199e8203; (d) Nagaoka, Y.; El-Koussi, N.; Uesato, S.; Tomioka, K. Tetrahedron
Lett. 2002, 43, 4355e4359; (e) Inoue, H.; Nagaoka, Y.; Tomioka, K. J. Org. Chem.
2002, 67, 5864e5867; (f) Nishimura, K.; Tsubouchi, H.; Ono, M.; Hayama, T.;
Nagaoka, Y.; Tomioka, K. Tetrahedron Lett. 2003, 44, 2323e2326; (g) Sakai, T.;
Kawamoto, Y.; Tomioka, K. J. Org. Chem. 2006, 71, 4706e4709; (h) Suzuki, M.;
Kawamoto, Y.; Sakai, T.; Yamamoto, Y.; Tomioka, K. Org. Lett. 2009, 11, 653e655;
(i) Yamada, K.; Maekawa, M.; Akindele, T.; Yamamoto, Y.; Nakano, M.; Tomioka,
K. Tetrahedron 2009, 65, 903e908; (j) Yamamoto, Y.; Yasuda, Y.; Nasu, H.; To-
mioka, K. Org. Lett. 2009, 11, 2007e2009; (k) Yamada, K.; Konishi, T.; Nakano,
M.; Fujii, S.; Cadou, R.; Yamamoto, Y.; Tomioka, K. J. Org. Chem. 2012, 77,
5775e5780; (l) Harada, S.; Sakai, T.; Takasu, K.; Yamada, K.; Yamamoto, Y.;
Tomioka, K. Chem.dAsian. J. 2012, 7, 2196e2198; (m) Harada, S.; Sakai, T.; Ta-
kasu, K.; Yamada, K.; Yamamoto, Y.; Tomioka, K. J. Org. Chem. 2012, 77,
7212e7222; (n) Harada, S.; Sakai, T.; Takasu, K.; Yamada, K.; Yamamoto, Y.;
Tomioka, K. Tetrahedron 2013, 69, 3264e3273.
Acknowledgements
We thank JSPS and MEXT for financial support.
Supplementary data
Supplementary data (Determination of enantiomeric excess,
and relative and absolute configuration, and characterization data
of the products (PDF)) related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2015.03.014.
References and notes
1. (a) Jin, Z. Nat. Prod. Rep. 2011, 28, 1126e1142; (b) Jin, Z. Nat. Prod. Rep. 2009, 26,
363e381; (c) Zarotsky, V.; Sramek, J. J.; Cutler, N. R. Am. J. Health-Syst. Pharm.
2003, 60, 446e452.
2. (a) Cook, J. W.; Loudon, J. D. In The Alkaloids; Manske, R. H. F., Holmes, H. L., Eds.;
Academic: New York, NY, 1952; Vol. 2, pp 331e352; (b) Kondo, H.; Uyeo, S.
Chem. Ber. 1935, 68, 1756e1760.
3. Kotera, K. Tetrahedron 1961, 12, 240e247.
4. Yamada, K.; Yamashita, M.; Sumiyoshi, T.; Nishimura, K.; Tomioka, K. Org. Lett.
2009, 11, 1631e1633.
13. NMR and X-ray studies on substituted phenyllithiums: (a) Reich, H. J.; Gold-
enberg, W. S.; Sanders, A. W.; Jantzi, K. L.; Tzschucke, C. C. J. Am. Chem. Soc.
€
2003, 125, 3509e3521; (b) Reich, H. J.; Goldenberg, W. S.; Gudmundsson, B. O.;
Sanders, A. W.; Kulicke, K. J.; Simon, K.; Guzei, I. A. J. Am. Chem. Soc. 2001, 123,
8067e8079; (c) Boman, A.; Johnels, D. Magn. Reson. Chem. 2000, 38, 853e860.
14. Doi, H.; Sakai, T.; Iguchi, M.; Yamada, k.; Tomioka, K. J. Am. Chem. Soc. 2003, 125,
2886e2887.
15. Also in the LiAlH4 reduction of tt-7b, the ester group at the C-2 remained
unchanged (see Supplementary data).
5. Recent synthetic studies of lycorine: Sun, Z.; Zhou, M.; Li, X.; Meng, X.; Peng, F.;
Zhang, H.; Shao, Z. Chem.dEur. J. 2014, 20, 6112e6119. Other approaches are
cited therein.
16. Ninomiya, K.; Shioiri, T.; Yamada, S. Tetrahedron 1974, 30, 2151e2157.
ꢀ
17. (a) Sanchez, I. H.; Mendoza, M. T. Tetrahedron Lett. 1980, 21, 3651e3654; (b)
6. Racemic syntheses: (a) Hill, R. K.; Joule, J. A.; Loeffler, L. J. J. Am. Chem. Soc. 1962,
84, 4951e4956; (b) Martin, S. F.; Tu, C.-y J. Org. Chem. 1981, 46, 3764e3767; (c)
Martin, S. F.; Tu, C.-y.; Kimura, M.; Simonsen, S. H. J. Org. Chem. 1982, 47,
3634e3643 Asymmetric syntheses: (d) Dong, L.; Xu, Y.-J.; Yuan, W.-C.; Cui, X.;
Cun, L.-F.; Gong, L.-Z. Eur. J. Org. Chem. 2006, 4093e4105; (e) Hong, B.-C.; Nimje,
R. Y.; Wu, M.-F.; Sadani, A. A. Eur. J. Org. Chem. 2008, 1449e1457.
Taylor, E. C., Jr.; Kalenda, N. W. J. Am. Chem. Soc. 1954, 76, 1699e1700.
18. Venuti, M. C.; Ort, O. Synthesis 1988, 985e988.
19. Shindo, M.; Koga, K.; Tomioka, K. J. Org. Chem. 1998, 63, 9351e9357.
20. Mattson, R. J.; Sloan, C. P.; Lockhart, C. C.; Catt, J. D.; Gao, Q.; Huang, S. J. Org.
Chem. 1999, 64, 8004e8007.
Please cite this article in press as: Nishimura, K.; et al., Tetrahedron (2015), http://dx.doi.org/10.1016/j.tet.2015.03.014