Synthetic studies on phloroglucins: a new approach to the bicyclo[3.3.1]nonane system via the regioselective ring-opening of the methoxycyclopropane

Article abstract of DOI:10.1016/j.tetlet.2007.05.041

A new synthetic approach to the bicyclo[3.3.1]nonane system, a common structure in a number of polyisoprenylated phloroglucinol derivatives (phloroglucins), has been developed. The key step in our approach is a 'one-pot' procedure of two successive reacti

Full text of DOI:10.1016/j.tetlet.2007.05.041

Tetrahedron Letters 48 (2007) 4873–4877
Synthetic studies on phloroglucins: a new approach to
the bicyclo[3.3.1]nonane system via the regioselective
ring-opening of the methoxycyclopropane
Masahito Abe and Masahisa Nakada*
Department of Chemistry and Biochemistry, Faculty of Advanced Science and Engineering, Waseda University,
3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-8555, Japan
Received 3 April 2007; revised 2 May 2007; accepted 10 May 2007
Available online 16 May 2007
Abstract—A new synthetic approach to the bicyclo[3.3.1]nonane system, a common structure in a number of polyisoprenylated
phloroglucinol derivatives (phloroglucins), has been developed. The key step in our approach is a ‘one-pot’ procedure of two suc-
cessive reactions, the intramolecular cyclopropanation reaction which affords the tricyclo[4.4.0.05,7]dec-2-ene derivative and its
methoxy group directed regioselective ring-opening reaction mediated by ZnCl2, producing the desired bicyclo[3.3.1]nonane as
the sole product.
Ó 2007 Elsevier Ltd. All rights reserved.
Phloroglucins, polyisoprenylated phloroglucinol deriva-
tives, are a growing family of natural products, possess-
ing a bicyclo[3.3.1]nonane framework as a common
structure.1 Numerous natural products belonging to this
family have been reported. The various oxygenation and
functionalization patterns on the bicyclo[3.3.1]nonane
framework give rise to diverse and complex structural
features. Besides their complex structure, phloroglucins
exhibit wide-ranging biological activities, including
cytotoxicity against several human cancer cell lines;2
hence, synthetic studies on this class of natural products
have been carried out.3,4
wort, a medicinal plant traditionally used to treat
depression, superficial wounds, burns, and dermatitis.5
Hyperforin possesses a complex trioxygenated bicy-
clo[3.3.1]nonane system which incorporates a homopren-
yl group and a methyl group at C6, three prenyl groups
at C1, C3, and C7, and an isobutyryl functionality at the
bridgehead C5. Hyperforin shows antibacterial,6 antitu-
mor,7 apoptotic,8 and other interesting biological activ-
ities.9,10 The complex structure of hyperforin as well as
its potent bioactivity have made it an attractive synthetic
target.
Recently, we reported a synthetic approach to the
bicyclo[3.3.1]nonane system (Scheme 1).11 The key
reaction in this approach is the Lewis acid promoted
regioselective ring-opening reaction of the cyclopropane
by the intramolecular attack of the benzyl carbonate of
a tricyclo[4.4.0.05,7]dec-2-ene derivative 1 to provide the
bicyclo[3.3.1]nonane derivative 2 as the sole product in
high yield. Nevertheless, further transformations would
be required to convert 2 to hyperforin. Particularly,
oxygen atoms should be introduced into the bicy-
clo[3.3.1]nonane framework. This operation should be
carried out at an early stage in the total synthesis
because hyperforin is sensitive to oxidation.4 Further-
more, the reaction of 3 under the same conditions as
those used for the conversion from 1 to 2 did not pro-
vide 4 (Scheme 1). This result suggested the limitation
of the transformation via the Lewis acid promoted
Hyperforin (Fig. 1) is a representative compound of the
phloroglucins, isolated as a metabolite from St. John’s
O
9
O
5
HO
4
6
8
3
7
1
2
O
H
Hyperforin
Figure 1.
*
Corresponding author. Tel./fax: +81 3 5286 3240; e-mail: mnakada@
waseda.jp
0040-4039/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2007.05.041

4874
M. Abe, M. Nakada / Tetrahedron Letters 48 (2007) 4873–4877
examined the IMCP reaction of an alkene substituted
O
OCO2Bn
by an oxygen atom. Therefore, we prepared the most
accessible substrate 12 (Scheme 3) from readily available
2, 6-dimethoxybenzoic acid methyl ester 8 to explore the
possibility of the IMCP reaction.
BF3 OEt2
(6.0 equiv)
O
9
H
O
O
4
6
5
1
3
CH2Cl2
-78 to -20 oC
93%
OH
7
8
H
2 H
CO2Et
CO2Et
H
1
2
Birch reduction of 8 and a subsequent ‘one-pot’ reaction
with allylbromide provided 9, and subsequent LiAlH4
reduction and protection of the resulting alcohol as a
TBDPS ether afforded 10 (63%, 3 steps). Regioselective
dihydroxylation of 10 using Sharpless’s ligand13 and fol-
lowing oxidative cleavage of the resulting diol by NaIO4
provided aldehyde 11 in 82% yield (2 steps). Attempts to
convert 11 to b-keto ester corresponding to 12 via a two-
step sequence that encompassed the aldol reaction of 11
with a lithium enolate of ethyl acetate followed by oxi-
dation of the resulting alcohol was low-yielding. Fur-
thermore, reaction of 11 with ethyl diazoacetate and
O
OCO2Bn
O
Lewis
acid
O
9
H
O
4
6
3
5
1
CH2Cl2
OH
7
8
H
2
SO2Ph
SO2Ph
3
4
Scheme 1.
ring-opening reaction of the benzyl carbonate of tricy-
clo[4.4.0.05,7]dec-2-ene derivatives.
14
SnCl2 afforded the product in moderate yield. How-
ever, Masamune’s protocol15 successfully converted 11
to the required b-keto ester in good yield. Thus, alde-
hyde 11 was oxidized to the carboxylic acid, which
was converted to the acyl imidazolide to react with
monoethyl malonate magnesium salt, providing the de-
sired b-keto ester, which was successfully converted to
the a-diazo-b-keto ester 12 (64%, 3 steps).
Consequently, we tried another approach to construct
the bicyclo[3.3.1]nonane framework in hyperforin from
a tricyclo[4.4.0.05,7]dec-2-ene derivative, and we herein
report a new approach to the bicyclo[3.3.1]nonane sys-
tem via the methoxy group directed regioselective ring-
opening reaction of the tricyclo[4.4.0.05,7]dec-2-ene
derivative.
The reaction of a-diazo-b-keto ester 12 with CuOTf
(10 mol %) in toluene at 80 °C proceeded very slowly;
however, use of ligand 13 (15 mol %) accelerated the
reaction to afford 14 in 55% isolated yield (Scheme 4).
The ring-opened product 15 (9%) also formed probably
because the initially formed 14 was further transformed
to 15 under the acidic reaction conditions.16 This result
indicated that the ring-opening reaction of 14 would af-
ford 15 under appropriate acidic conditions; hence, the
We devised a new intermediate 6 (Scheme 2) as a precur-
sor for 5 because use of 6 was expected to bring the fol-
lowing advantages: (1) Oxygen atoms introduced at C4
and C9 positions in 6 would correspond to the oxy-
gen-containing functional groups at C4 and C9 posi-
tions in 5. (2) A ring-opening reaction of 6 between C8
and C9 under acidic conditions was expected to be facile
because the cationic center which could be generated at
C9 would be stabilized by the oxygen atom at C9. (3)
Chiral tricyclo[4.4.0.05,7]dec-2-ene derivative 6 would
be prepared by the asymmetric intramolecular cyclo-
propanation of a-diazo-b-keto ester 7. (4) The methox-
yalkene moiety in 6 would be sensitive to the acidic
conditions for the ring-opening reaction; however, the
methoxycyclopropane was expected to be cleaved faster
under acidic conditions because of its strain.
Na, t-BuOH,
Et2O, liq. NH3;
MeO
OMe
1) LiAlH4, Et2O
0 oC, 20 min
CO2Me
CO2Me
OMe
then, allylbromide
-78 oC to rt, 11 h
2) TBDPSCl
imidazole
CH2Cl2/DMF
=10/1, rt, 24 h
MeO
9
8
We have been studying the intramolecular cyclopropa-
nation reaction (IMCP);11,12 however, we have never
63% (3 steps)
1) K2OsO2(OH)4,
(DHQD)2PHAL,
K3Fe(CN)6, K2CO3
MeO
OTBDPS
MeO
OTBDPS
CHO
R2O
OR3
O
t-BuOH/H2O=1/1, rt, 12 h
OR3
9
5
4
R1
R2O
6
4
2) NaIO4, MeOH/H2=1/1,
rt, 1 h
O
R1
9
7OH
CO2Et
1
3
MeO
10
8
MeO
11
8
2
OR2
R1
CO2Et
R1
82% (2 steps)
6
5
1) NaClO2, NaH2PO4, 2-methyl-2-butene,
-BuOH/H2O=1/1, rt, 36 h
MeO
OTBDPS
R2O
OR3
t
R1
O
N2
CO2Et
2) CDI, THF, 1 h;
then, (EtO2CCH2CO2)2Mg, THF, 41 h
3) TsN3, TEA, CH3CN, rt, 4 h
O
N2
MeO
12
OR2
CO2Et
R1
64% (3 steps)
7
Scheme 2.
Scheme 3.

M. Abe, M. Nakada / Tetrahedron Letters 48 (2007) 4873–4877
4875
[CuOTf]2 C6H6, (5 mol%),
O
OTBDPS
O
MeO
OTBDPS
ligand 13, (15 mol%)
OTBDPS
O
O
O
N2
CO2Et
toluene, 80 oC, 1.5 h
OH
CO2Et
MeO
MeO
12
H
CO2Et
O
O
16
17
N
N
O
Figure 2.
13
MeO
OTBDPS
OTBDPS
Since the ring-opening reaction of 14 was found to pro-
ceed in toluene, a ‘one-pot’ procedure of two successive
reactions, the catalytic IMCP reaction of 12 and the
ring-opening reaction of the in situ formed tricy-
clo[4.4.0.05,7]dec-2-ene derivative 14 with ZnCl2, was
examined. After checking the completion of the IMCP
reaction of 12, the diethyl ether solution of ZnCl2 was
carefully added to the reaction mixture at À78 °C. The
reaction mixture was warmed up to room temperature
to bring about the ring-opening reaction to provide
the desired bicyclo[3.3.1]nonane derivative 15 in 70%
yield.
MeO
O
+
OH
CO2Et
H
MeO
CO2Et
15 9%
14 55%
Scheme 4.
ring-opening reaction of 14 with Lewis acid was next
examined.
Reaction of 14 with TiCl4 (Table 1, entry 1) at À78 °C
was completed within 1 h to cause cleavage of the alken-
yl ether to generate diketone 16 in 84% (Fig. 2), but no
ring-opened products 15 or 17 were obtained. The reac-
tion of 14 with BF3ÆOEt2 (entry 2) afforded the desired
15 in a rather low yield (19%), and use of Me2BBr (entry
3)17 provided compound 16 (67%) as the sole product
again. After screening several Lewis acids,18 we found
that use of ZnCl2 was favorable for this ring-opening
reaction, providing 15 in 47% yield (entry 4). The reac-
tion must be carried out at room temperature to be com-
pleted and the optimized reaction time was 3.5 h because
the prolonged reaction at room temperature caused
cleavage of the alkenyl ether to afford 17 only instead
(55%, entry 5). Among the solvents examined for this
reaction, toluene was found to improve the yield slightly
(51%, entry 6).
Since the IMCP reaction of 12 afforded 14 and 15 in
64% combined yield and the ring-opening reaction of
14 provided 15 in 51% yield, this ‘one-pot’ procedure
greatly improved the yield of 15, which was practical en-
ough for the synthetic purpose. We examined the ring-
opening reaction of 14 under the same conditions as
those employed in Scheme 5, too, but this attempt did
not improve the yield. Therefore, the improved yield in
the ‘one-pot’ procedure did not depend on the reagent
system in Scheme 5. The yield of 15 in the ZnCl2-medi-
ated ring-opening reaction of 14 (entry 6) was reproduc-
ible, and the formation of some structurally unidentified
side-products reduced the yield. Hence, the moderate
yield of 15 in entry 6 of Table 1 could be affected by
something remaining (possibly moisture) in 14.
In summary, a new effective approach to the bicy-
clo[3.3.1]nonane system, a common structure in a num-
ber of polyisoprenylated phloroglucinol derivatives
(phloroglucins), has been developed. A ‘one-pot’ two
successive reactions, the intramolecular cyclopropana-
tion affording the tricyclo[4.4.0.05,7]dec-2-ene derivative
12 and its ZnCl2 mediated regioselective ring-opening
reaction directed by the methoxy group, produced the
desired 15 as the sole product. We expect this procedure
to be applicable to tricyclo[4.4.0.05,7]dec-2-ene deriva-
tive 6 possessing suitable substituent at its C1 and C3,
which would be prepared from the corresponding a-di-
azo-b-keto ester 7. Hence, further studies on the
Table 1. Lewis acid mediated ring-opening reaction of 14
O
MeO
OTBDPS
OTBDPS
MeO
conditions
CH2Cl2
O
OH
CO2Et
H
MeO
14
CO2Et
15
Entry Lewis
acida
Temp (°C)
À78
Time (h) Product Yieldb
(%)
1
2
3
4
5
6e
TiCl4
1
16d
15
84
19d
67
47
55
51
BF3ÆOEt2 À78, À30
1, 12c
Me2BBr
ZnCl2
ZnCl2
ZnCl2
À78, À50, À20 1, 1, 0.5c 16
À78, 0, rt
À78, 0, rt
À78, 0, rt
1, 1, 3.5c 15
1, 1, 60c 17
1, 1, 3.5c 15
[CuOTf]2 C6H6 (5 mol%)
MeO
OTBDPS
O
ligand 13 (15 mol%)
OTBDPS
toluene, 80 oC, 1.5 h
MeO
O
N2
CO2Et
a 1.5 equiv of Lewis acid was used.
b Isolated yields except entry 2.
OH
CO2Et
then, ZnCl2 (1.5 equiv)
rt, 3.5 h
MeO
12
Scheme 5.
H
c Time at the corresponding reaction temperature.
d Yield determined by 400 MHz 1H NMR due to the remaining
inseparable TBDPSF.
15
70%
e Toluene was used as the solvent.

4876
M. Abe, M. Nakada / Tetrahedron Letters 48 (2007) 4873–4877
Klein, A.; Miesch, M. Tetrahedron Lett. 2003, 44, 4483–
4485; (j) Srikrishna, A.; Kumar, P. P.; Reddy, T. J.
ARKIVOC 2003, 3, 55–66; (k) Mehta, G.; Bera, M. K.
Tetrahedron Lett. 2004, 45, 1113–1116; (l) Usuda, H.;
Kuramochi, A.; Kanai, M.; Shibasaki, M. Org. Lett. 2004,
6, 4387–4390; (m) Nicolaou, K. C.; Carenzi, G. E. A.;
Jeso, V. Angew. Chem., Int. Ed. 2005, 44, 3895–3899; (n)
Mehta, G.; Bera, M. K. Tetrahedron Lett. 2006, 47, 689–
692.
asymmetric synthesis of hyperforin are now underway in
this laboratory.
Acknowledgments
This work was financially supported in part by a Wase-
da University Grant for Special Research Projects and a
Grant-in-Aid for Scientific Research on Priority Areas
(Creation of Biologically Functional Molecules (No.
17035082)) from the Ministry of Education, Culture,
Sports, Science and Technology (MEXT), Japan. We
are also indebted to 21COE ‘Practical Nano-Chemistry’.
4. For total synthesis of garsubellin, see: (a) Kuramochi, A.;
Usuda, H.; Yamatsugu, K.; Kanai, M.; Shibasaki, M. J.
Am. Chem. Soc. 2005, 127, 14200–14201; (b) Siegel, D. R.;
Danishefsky, S. J. J. Am. Chem. Soc. 2006, 128, 1048–
1049; For total synthesis of clusianone, see: (c) Rodes-
chini, V.; Ahmad, N. M.; Simpkins, N. S. Org. Lett. 2006,
8, 5283–5285; (d) Nuhant, P.; David, M.; Pouplin, T.;
Delpech, B.; Marazano, C. Org. Lett. 2007, 9, 287–
289.
References and notes
5. (a) Gurevich, A. I.; Dobrynin, V. N.; Kolosov, M. N.;
Popravko, S. A.; Ryabova, I. D.; Chennov, B. K.;
Derbentseva, N. A.; Aizenman, B. E.; Garagulya, A. D.
Antibiotiki 1971, 6, 510–513; (b) Bystrov, N. S.; Chernov,
B. K.; Dobrynin, V. N.; Kolosov, M. N. Tetrahedron Lett.
1975, 16, 2791–2794; (c) Erdelmeier, C. A. J. Pharmacop-
sychiatry 1998, 31 (Suppl. 1), 2–6; (d) Barnes, J.;
Anderson, L. A.; Phillipson, J. D. J. Pharm. Pharmacol.
2001, 53, 583–600; (e) Schempp, C. M.; Windeck, T.;
Hezel, S.; Simon, J. C. Phytomedicine 2003, 10 (Suppl. 4),
31–37.
1. For recently reported phloroglucins, see: (a) Weng, J.-R.;
Tsao, L.-T.; Wang, J.-P.; Wu, R.-R.; Lin, C.-N. J. Nat.
Prod. 2004, 67, 1796–1799; (b) Cruz, F. G.; Teixeira, J. S.
R. J. Brz. Chem. Soc. 2004, 15, 504–508; (c) Wu, J.;
Cheng, X.-F.; Harrison, L. J.; Goh, S.-H.; Sim, K.-Y.
Tetrahedron Lett. 2004, 45, 9657–9659; (d) Wu, C.-C.;
Weng, J.-R.; Won, S.-J.; Lin, C.-N. J. Nat. Prod. 2005, 68,
1125–1127; (e) Herath, K.; Jayasuriya, H.; Ondeyka, J. G.;
Guan, Z.; Borris, R. P.; Stijfhoorn, E.; Stevenson, D.;
Wang, J.; Sharma, N.; Macnaul, K.; Menke, J. G.; Ali, A.;
Schulman, M. J.; Singh, S. B. J. Nat. Prod. 2005, 68, 617–
619; (f) Baggett, S.; Protiva, P.; Mazzola, E. P.; Yang, H.;
Ressler, E. T.; Basile, M. J.; Weinstein, I. B.; Kennelly, E.
J. J. Nat. Prod. 2005, 68, 354–360; (g) Massoit, G.; Long,
C.; David, B.; Serrano, M. J.; Daubie, F.; Alby, F.;
Ausseil, F.; Knibiehler, M.; Moretti, C.; Hoffmann, J. S.;
Cazaux, C.; Lavaud, C. J. Nat. Prod. 2005, 68, 979–984;
(h) Hernandez, I. M.; Fernandez, M. C.; Cuesta-Rubio,
O.; Piccinelli, A. N.; Rastrelli, L. J. Nat. Prod. 2005, 68,
931–934; (i) Taher, M.; Idris, M. S.; Ahmad, F.; Arbain,
D. Phytochemistry 2005, 66, 723–726; (j) Teixeira, J. S. R.;
Cruz, F. G. Tetrahedron Lett. 2005, 46, 2813–2816; (k)
Wu, C.-C.; Weng, J.-R.; Won, S.-J.; Lin, C.-N. J. Nat.
Prod. 2005, 68, 1125–1127; (l) Piccinelli, A. L.; Cuesta-
Rubio, O.; Chica, M. B.; Mahmood, N.; Pagano, B.;
Pavone, M.; Barone, V.; Rastrelli, L. Tetrahedron 2005,
61, 8206–8211; (m) Cao, S.; Low, K.-N.; Glover, R. P.;
Crasta, S. C.; Ng, S.; Buss, A. D.; Butler, M. S. J. Nat.
Prod. 2006, 69, 707–709; (n) Wafaa, H.; Solenn, B.;
Florence, M.-B.; Odile, T.; Stephane, M.; Bernard, D.;
Hung, N. V.; Thierry, S.; Christian, M. J. Nat. Prod. 2006,
69, 774–777, For the earlier reports, see references in Ref.
11.
2. Reviews: (a) Ciochina, R.; Grossman, R. B. Chem. Rev.
2006, 106, 3963–3986; (b) Medina, M. A.; Martinez-
Poveda, B.; Amores-Sanchez, M. I.; Quesada, A. R. Life
Sci. 2006, 79, 105–111; (c) Quiney, C.; Billard, C.;
Salanoubat, C.; Fourneron, J. D.; Kolb, J. P. Leukemia
2006, 20, 1519–1525.
3. (a) Nicolaou, K. C.; Pfefferkorn, J. A.; Kim, S.; Wei, H. X.
J. Am. Chem. Soc. 1999, 121, 4724–4725; (b) Nicolaou, K.
C.; Pfefferkorn, J. A.; Cao, G.-Q.; Kim, S.; Kessabi, J.
Org. Lett. 1999, 1, 807–810; (c) Usuda, H.; Kanai, M.;
Shibasaki, M. Org. Lett. 2002, 4, 859–862; (d) Spessard, S.
J.; Stoltz, B. M. Org. Lett. 2002, 4, 1943–1946; (e) Young,
D. G. J.; Zeng, D. X. J. Org. Chem. 2002, 67, 3134–3147;
(f) Usuda, H.; Kanai, M.; Shibasaki, M. Tetrahedron Lett.
2002, 43, 3621–3624; (g) Kraus, G. A.; Nguyen, T. H.;
Jeon, I. Tetrahedron Lett. 2003, 44, 659–661; (h) Ciochina,
R.; Grossman, R. B. Org. Lett. 2003, 5, 4619–4621; (i)
6. Schempp, C. M.; Pelz, K.; Wittmer, A.; Schopf, E.; Simon,
J. C. Lancet 1999, 353, 2129.
7. (a) Schempp, C. M.; Winghofer, B.; Ludtke, R.; Simon-
¨
Haarhaus, B.; Scho¨pff, E.; Simon, J. C. Br. J. Dermatol.
2000, 142, 979–984; (b) Schempp, C. M.; Kirkin, V.;
Simon-Haarhaus, B.; Kersten, A.; Kiss, J.; Termeer, C. C.;
Gilb, B.; Kaufmann, T.; Borner, C.; Sleeman, J. P.; Simon,
J. C. Oncogene 2002, 21, 1242–1250; For the derivative of
hyperforin, see: (c) Gartner, M.; Muller, T.; Simon, J. C.;
¨
Giannis, A.; Sleeman, J. P. Chem. BioChem. 2005, 6, 171–
177.
8. Hostanska, K.; Reichling, J.; Bommer, S.; Weber, M.;
Saller, R. Eur. J. Pharm. Biopharm. 2003, 56, 121–132.
9. Inhibition of inflammatory enzymes (cyclooxygenase-1
and 5-lipoxygenase): (a) Albert, D.; Zundorf, I.; Dinger-
¨
mann, T.; Muller, W. E.; Steinhilber, D.; Werz, O.
¨
Biochem. Pharmacol. 2002, 64, 1767–1775; Interference
with radical chain oxidation processes: (b) Heilmann, J.;
Winkelmann, K.; Sticher, O. Planta Med. 2003, 69, 202–
206.
10. Action as a nuclear factor that regulates expression of the
cytochrome P450 3A4 monooxygenase: (a) Watkins, R.
E.; Maglich, J. M.; Moore, L. B.; Wisely, G. B.; Noble, S.
M.; Davis-Searles, P. R.; Lambert, M. H.; Kliewer, S. A.;
Redinbo, M. R. Biochemistry 2003, 42, 1430–1438; (b)
Moore, L. B.; Goodwin, B.; Jones, S. A.; Wisely, G. B.;
Serabjit-Singh, C. J.; Willson, T. M.; Collins, J. L.;
Kliewer, S. A. Proc. Natl. Acad. Sci. U.S.A. 2000, 97,
7500–7502.
11. Abe, M.; Nakada, M. Tetrahedron Lett. 2006, 47, 6347–
6351.
12. Our efforts in the asymmetric catalysis of intramolecular
cyclopropanation: (a) Honma, M.; Sawada, T.; Fujisawa,
Y.; Utsugi, M.; Watanabe, H.; Umino, A.; Matsumura,
T.; Hagihara, T.; Takano, M.; Nakada, M. J. Am. Chem.
Soc. 2003, 125, 2860–2861; (b) Honma, M.; Nakada, M.
Tetrahedron Lett. 2003, 44, 9007–9011; (c) Takano, M.;
Umino, A.; Nakada, M. Org. Lett. 2004, 6, 4897–4900; (d)
Sawada, T.; Nakada, M. Adv. Synth. Catal. 2005, 347,
1527–1532; (e) Miyamoto, H.; Iwamoto, M.; Nakada, M.

M. Abe, M. Nakada / Tetrahedron Letters 48 (2007) 4873–4877
4877
Heterocycles 2005, 66, 61–68; (f) Takeda, H.; Watanabe,
H.; Nakada, M. Tetrahedron 2006, 62, 8054–8063; (g)
Takeda, H.; Nakada, M. Tetrahedron: Asymmetry 2006,
17, 2896–2906; (h) Takeda, H.; Honma, M.; Ida, R.;
Sawada, T.; Nakada, M. Synlett 2007, 579–582.
14. Holmquist, C. R.; Roskamp, E. J. J. Org. Chem. 1989, 54,
3258–3260.
15. Brooks, D. W.; Lu, L. D.-L.; Masamune, S. Angew.
Chem., Int. Ed. Engl. 1979, 18, 72–73.
1
16. Structure of 15 was fully characterized by H NMR, 13C
13. Sharpless, K. B.; Amberg, W.; Bennani, Y. L.; Crispino,
G. A.; Hartung, J.; Jeong, K.-S.; Kwong, H.-L.; Morik-
awa, K.; Wang, Z.-M.; Xu, D.; Zhang, X.-L. J. Org.
Chem. 1992, 57, 2768–2771.
NMR, IR, and HRMS spectra.
17. Quindon, Y.; Morton, H. E.; Yoakim, C. Tetrahedron
Lett. 1983, 24, 3969–3972.
18. No reaction occurred with LiClO4 and MgCl2.