Stereoselective synthesis of 2,5-di- and 2,2,5-trisubstituted pyrrolidines by allylation reacton of acyliminium ion

Article abstract of DOI:10.3987/COM-05-S(K)61

-Allylation reactions of allytrimethylsilane and an allylcopper reagent to acyliminium ions derived from several 2-monosubstituted and 2,2-disubstituted pyrrolidinones were examined. These reactions proceeded in a stereoselective manner to give the corresponding allylated adducts. The stereochemical outcomes of these reactions were dependent upon the allylating reagents or the structures of the acyliminium ions.

Full text of DOI:10.3987/COM-05-S(K)61

HETEROCYCLES, Vol. 66, 2005
511
HETEROCYCLES, Vol. 66, 2005, pp. 511 – 525. © The Japan Institute of Heterocyclic Chemistry
Received, 20th September, 2005, Accepted, 28th October, 2005, Published online, 1st November, 2005. COM-05-S(K)61
STEREOSELECTIVE
SYNTHESIS
OF
2,5-DI-
AND
2,2,5-
TRISUBSTITUTED PYRROLIDINES BY ALLYLATION REACTON OF
ACYLIMINIUM ION
Tetsuro Shinada,* Makoto Hamada, Masanori Kawasaki, and Yasufumi
Ohfune*
Graduate School of Science, Osaka City University, Sumiyoshi, Sugimoto, Osaka
558-8585, Japan. ohfune@sci.osaka-cu.ac.jp, shinada@sci.osaka-cu.ac.jp
Abstract – Allylation reactions of allytrimethylsilane and an allylcopper reagent
to acyliminium ions derived from several 2-monosubstituted and 2,2-disubstituted
pyrrolidinones were examined. These reactions proceeded in a stereoselective
manner to give the corresponding allylated adducts. The stereochemical outcomes
of these reactions were dependent upon the allylating reagents or the structures of
the acyliminium ions.
INTRODUCTION
2,5-Disubstitued pyrrolidine is a basic heterocyclic framework of a wide range of natural products and
pharmaceutically interesting molecules.1 Recently, biologically active pyrrolidine derivatives having a
2,2,5-trisubstituted pyrrolidine skeleton, e.g., kaitocephalin2 and cylindricines,3 have been isolated. To
date, many synthetic efforts have been made for the stereoselective construction of 2,5- and
2,2,5-substituted pyrrolidines. Among them, an allylation reaction to an acyliminium intermediate derived
from a pyroglutamate derivative is a useful approach to this end (Scheme 1).1,4,5
R2
R3
R2
R3
R2
R3
M
R2
R3
5
N
R4
O
N
N
N
2
H
R1
acyliminium ion
O
R1
O
R1
O
M = Si, Sn, etc.
2,5-disubstituted or
2,2,5-trisubstituted
pyrrolidines
Scheme 1
This paper is dedicated to the memory of the Emeritus Professor Kenji Koga of Tokyo University.

512
HETEROCYCLES, Vol. 66, 2005
Recently, we have reported the total synthesis of kaitocephalin by an allylation reaction of an
acyliminium ion as a key step (Scheme 2).6 During the course of this study, we found that the
stereoselectivity of the key allylation reaction was dependent upon the allylic metal reagents. When an
allylcopper reagent was employed for the allylation reaction of 1, cis-isomer (2a) was obtained as a major
product (2a:2b = 2:1). In contrast, the use of allyltrimethylsilane (5) gave trans-isomer (2b), exclusively.
It is worthwhile to note that the stereoselectivity observed in the above allylation reactions was opposite
to the case of pyroglutamate (3) (Scheme 3). It has been reported that Lewis acid-mediated addition
reactions of allyltrimethylsilane or allyltributyltin to 4 proceeded in a stereoselective manner to give
cis-isomers.5g-k Although addition reactions of alkyl and vinylcopper reagents gave trans-isomers as
major products 7 the allylation reaction of 4 with an allylcopper reagent has not been examined. These
results led us to investigate the origin of the reagent- and substrate-dependent allylation reactions. In this
study, we report stereoselective allylation reactions of several 2-monosubstituted and 2,2-disubstitued
pyrrolidinones (9a-d) using allyltrimethylsilane and an allylcopper reagent.
Cl
CO2Me
CO2Me
7
MgBr
Me2S-CuBr
HO
Cl
N
H
H
CO2H
NH2
9
7
Boc
N
O
NCbz
N
BF3-OEt2
CO2Me
CO2Me
H
O
H
CO2H
cis-2a
CO2H
HO
2a:2b = 2:1
AcO
N
Boc
kaitocephalin and (9R)- isomers
O
NCbz
Cl
HO
Cl
SiMe3
CO2Me
7
1
CO2Me
5
H
CO2H
N
N
H
NH2
BF3-OEt2
Boc
O
NCbz
N
H
CO2H
O
H
CO2H
HO
trans-2b
single isomer
(7S, 9S)- and (7S,9R)-isomers
Scheme 2
CO2R2
SiMe3
H
N
H
5
CO2R2
CO2R2
H
O
OR1
cis-isomer
O
H
Lewis Acid
N
N
CO2R2
OR1
H
R
O
OR1
O
4
H
3
N
RCuLn
R = Vinyl, Alkyl
R1 = Me, Bn, t-Bu
R2 = Me, Et
O
OR1
trans-isomer
Scheme 3

HETEROCYCLES, Vol. 66, 2005
513
RESULTS AND DISCUSSION
Four substrates (6a-d) bearing substituents at C2 were employed for the addition reactions (Scheme 4).
The silyloxy derivative (6b) was synthesized in 2 steps from 7. The 2,2-disubstituted compound (6c) was
prepared by silylation of alcohol (8). 6 The E-α,β-unsaturated ester (6d)6 was synthesized by oxidation of
8 to an aldehyde followed by Wittig olefination.
6a R1 = CO2Me, R2 = H
R1
R2
OTBDPS
1) TBDPSCl
OH
6b R1 = CH2OTBDPS, R2 = H
6c R1 = CO2Me, R2 = CH2OTBDPS
6d R1 = CO2Me, R2 = CH=CHCO2Me
Et3N, DMAP
O
O
O
N
H
N
H
N
H
2) (Boc)2O, Et3N,
DMAP
67% in 2 steps
Boc
Boc
6b
7
1) TEMPO
CO2Me
1) TFA/CH2Cl2
CO2Me
OH
CO2Me
OTBDPS
PhI(OAc)2
O
O
O
2) TBDPSCl
3) (Boc)2O
N
N
N
2)
Boc
Boc
Boc
CO2Me
Ph3P
CO2Me
83% in 3 steps
89% in 2 steps
8
6c
6d
Scheme 4
N-Boc-lactams (6a-d) were converted to acyliminium ion precursors (9a-d) by a chemoselective
reduction with LiBEt3H followed by treatment with Ac2O (Scheme 5). Since 9a-d were labile for
purification on silica gel, the crude acetates (9a-d) were used for the allylation reaction without
purification. Addition reaction with allyltrimethylsilane (5 equiv.) was performed in the presence of
BF3-OEt2 (1.2 equiv.) in CH2Cl2 at -78 oC for 15 min. The addition reaction of an allyl copper reagent to
an acyliminium ion has been unprecedented except for the case of 1.6 After numerous attempts, we
established the following reproducible procedure: i) allylmagnesium bromide was added to Me2S-CuBr in
o
o
THF at -40 C and stirred for 0.5 h, ii) the mixture was cooled to -78 C, iii) to the mixture was added
o
BF3-OEt2 at -78 C, iv) 9 was added dropwise to the mixture, and v) the reaction mixture was gradually
warmed to 0 oC. These results are listed in Table 1.
SiMe3
or
R1
R2
R1
R2
R1
R2
Cu
1) LiBEt3H
AcO
O
N
N
N
Boc
Boc
9a-d
Boc
6a-d
2) Ac2O,
DMAP
BF3OEt2
cis-10a-d, trans-11a-d
Scheme 5
1
The ratios and structures of the adducts (10) and (11) were determined by H-NMR spectral data and
NOE spectral experiments of the corresponding pyrrolidine derivatives (Figure 1). Boc derivatives (10)
and (11) showed complex and broad signals due to the formation of a mixture of the rotamers in CDCl3 in
1
their H-NMR spectra. To obtain simple NMR spectral patterns, these compounds were converted to the
corresponding amines (12a-d) by the removal of the Boc groups. The NOESY spectral experiments

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HETEROCYCLES, Vol. 66, 2005
Table 1. Allylation Reactions of 9a-d and 1.
Productsa,b
Entry
1
Substrate
CO2Me
CO2Me
H
CO2Me
2
N
N
AcO
H
N
H
H
H
Boc
Boc
cis-10a
Boc
trans-11a
9a
Si c 84:16 (56%)
Cud 31:69 (48%)
OTBDPS
OTBDPS
OTBDPS
2
N
H
N
AcO
H
H
H
N
H
H
Boc
Boc
Boc
trans-11b
cis-10b
9b
Si 28:72 (37%)e
Cu 28:72 (74%)
CO2Me
OTBDPS
CO2Me
OTBDPS
CO2Me
N
AcO
N
N
H
OTBDPS
3
4
Boc
Boc
Boc
trans-11c
Si 75:25 (51%)f
Cu 68:32 (60%)
9c
cis-10c
CO2Me
CO2Me
CO2Me
AcO
N
N
N
H
H
Boc
Boc
Boc
CO2Me
CO2Me
CO2Me
trans-11d
cis-10d
9d
Si >98:2 (57%)
Cu 80:20 (20%)g
CO2Me
CO2Me
CO2Me
CO2Me
CO2Me
CO2Me
5
N
N
AcO
N
H
H
Boc
Boc
Boc
O
NCbz
O
NCbz
O
NCbz
trans-2b
cis-2a
1
Si 2:>98 (80%)
Cu 66:34 (60%)
a Cis is the term meaning where the allyl group is placed in the same face as the upper substituents
at C2 in 2a and 10a-d. Trans is the term meaning in the opposite sense to cis.
b Product ratios were determined by 1H-NMR spectrum of the corresponding amines.
OTBDPS
c Si : addition of 5.
H
N
d Cu: addition of an allycopper reagent.
3
TMS
(3S)-A, (3R)-B
O
O
e Cyclic carbamates (A) and (B) were obtained as a minor product.
The yeild of A and B were counted in the trans product.
f Cyclic carbamates (C) was obtained as a minor product.
The yield of C was counted in the cis product.
CO2Me
H
N
OTBDPS
C
TMS
O
O
H
g A complex mixture was obtained. One of the major products was a Michael adduct.

HETEROCYCLES, Vol. 66, 2005
515
of 12a-d confirmed the cis-relationship between R1 and the allyl group (Figure 1). The structures of 2a
and 2b were determined by its conversion to kaitocephalin and its C7-epimer, respectively. Based on
these results, the structures of trans-11a-d and 2b were unambiguously established.
CO2Me
CO2Me
OTBDPS
R
H
R1
2
R2
N
N
N
H
H
H
H
5
N
H
H
H
CO2Me
NOE
TMSOTf,
2,6-lutidine
P
H
10a-d: P = Boc
12a-d: P = H
R = CO2Me: cis-12a
R = CH2OTBDPS: cis-12b
cis-12d
cis-12c
Figure 1. Structure determination of the allylated adducts by NOE experiments.
Stereoselectivity of the allylation reactions using 9a and 1 were dependent on the metal species on the
allylic carbanion (Entries 1 and 5). In contrast, the allylation reactions using 9b and 9c were not affected
by the allylating reagents to give trans-11b and cis-10c as a major product, respectively (Entries 2 and 3).
The addition reaction of 9d with 5 gave cis-10d, exclusively (Entry 4). The use of the allylcopper reagent
to 9d also gave cis-10d as a major product in low yield due to a competition with a conjugate addition
reaction (Entry 4). The allylation reaction of 9b and 9c with 5 afforded cyclic carbamates (A, B, and C)
as a minor product (Entries 2 and 3).9 These side reactions were suppressed when the allylcopper reagent
was used.
Two transition state models (TS-A) and (TS-B) were proposed for explanation of the cis-selective
allylation reaction of 9a using allytrimethylsilane (5).5g-k,8 TS-A involves a considerable steric repulsion
between the methoxy carbonyl and the Boc groups. Accordingly, the t-Bu group occupies the α-face
(Figure 2).5g The addition reaction of 5 to TS-A preferentially occurs from the sterically less hindered
β-face to give cis-10a. Recently, Tomoda et al. have reported that an electrostatic or an orbital interaction
between the carbonyl and silyl groups attributes to the cis-selectivite deuteration of 9a with R3SiD (TS-B,
X = D).8 Similar attractive interaction would also account for the cis-selective allylation of 5 as shown in
TS-B (X = allyl).
R = Alkyl
X = D or allyl
Me3Si
CO2Me
5
CO2Me
CO2Me
t-Bu
SiR3
O
X
OMe
O
N
N
OMe
H
O
t-BuO
O
H
H
N
O
O
O
H
N
N
O
Cbz
H
Si
Me3
t-BuO
TS-B
N
O
MeO2C
5
H
t-Bu
O
Cbz
TS-D
TS-C
TS-A
Figure 2. Proposed TS for stereoselective addition reactions of 5 to 1 and 9a.
The addition reaction of 5 to 1 gave trans-2b, exclusively (Table 1, Entry 5). The stereochemical outcome
was opposite to the case of 9a. We assumed that the acyliminium ion intermediate derived from 1 would

516
HETEROCYCLES, Vol. 66, 2005
form TS-C. The sterically bulky acetonide moiety in TS-C would compel the t-Bu group into the
β-position. Thus, the addition reaction of 5 took place selectively from the α-face to avoid the sterically
bulky Boc group. Alternatively, the electron-donating acetonide group would attract 5 to form TS-D,
leading the selective allylation reaction from the bottom face.
The addition reaction of the allylcopper reagent prepared by the optimized protocol to 9a gave trans-11a
with moderate stereoselectivity (Table 1, Entry 1). The stereochemical outcome was relevant to those of
vinyl and alkylcopper reagents.7 In this context, a similar TS model (TS-E) proposed by Wistrand et al.
would account for the trans-selective allylation reaction observed in this experiment.7g They suggested
formation of a copper complex between the methoxycarbonyl group and a copper species (TS-E, alkyl
and vinyl Cu). The copper reagents preferentially attack from the opposite side to the copper complex,
giving trans-products. The same reaction pathway would be involved in the allylation reaction of the
allylcopper reagents to 9a (TS-E, allyl Cu). In contrast, the allylation reaction of 1 occurred from the
same side of the methoxycarbonyl group. The reverse stereoselectivity (β-face attack) would be attributed
to the stronger Lewis basic character of the alkoxy group than that of the carbonyl group, that induces the
formation of copper complex in the α-face (TS-F).
Cu Complex
Allyl Cu
CO2Me
O
Cu
OMe
N
H
CO2Me
H
Boc
N
O
Cu
Boc
H
NCbz
Alkyl Cu
Vinyl Cu
TS-F
TS-E
Cu
Figure 3. Proposed TS for stereoselective allylation reactions of 1 and 9a with allylcopper reagent.
Allylation reactions of 9b and 9c with allyltrimethylsilane gave trans-11b (28:72) and cis-10c (68:32),
respectively (Table 1, Entries 2 and 3). The addition reactions of the allylcopper reagents resulted in a
same manner. These results indicated that the silyloxymethyl group exerts the large influence on the
stereoselectivity. The effects of the alkoxy- and hydroxymethyl groups in the allylation reactions has been
discussed by Shono et al.5i and Langlois et al.10 They proposed TS-G which includes neighboring group
paticipation of the hydroxy and acetyloxy groups to the acyliminium ion (Figure 4). It is assumed that the
allylation reactions of 9b and 9c using the allylcopper reagent proceeded via similar intermediates (TS-G
and TS-H). Recently, the effect of the silyloxymethyl group upon reduction of an acyliminium ion such
as 9b using R3SiD has been evaluated by the exterior frontier orbital extension model by Tomoda et al.8
They suggested that the steric congestion of the silyloxymethyl group of 9b is a crucial factor for the

HETEROCYCLES, Vol. 66, 2005
517
stereochemical outcome rather than the neighboring group participation (TS-I). This possibility could not
be ruled out in our cases (TS-I and TS-J).
R
Cu
Cu
or
5
R = H, Ac,
or TBDPS
5
or
TBDPSO
N
O
N
CO2Me
CO2Me
N
N
O
Cu
O
Cu
O
O
H
O
O
H
t-Bu
O
or
5
t-Bu
TS-J
O
5
O
TBDPSO
TBDPS
or
t-Bu
t-Bu
TS-I
TS-G
R3SiH
TS-H
Figure 4. Effects of the silyloxymethyl group of 9b and 9c for the stereoselective allylation reactions.
In summary, we have demonstrated allylation reactions of allyltrimethylsilane and the allylcopper reagent
to various acyliminium intermediates. These results would provide valuable information for the
stereoselective synthesis of 2,5-disubstituted and 2,2,5-trisubstituted pyrrolidines.
EXPERIMENTAL
All reagents and solvents were purchased from either Aldrich Chemical Company, Inc., Nacalai Tesque
Company, Ltd., Tokyo Kasei Kogyo Co., Ltd., or Wako Pure Chemical Industries, Ltd., and used without
further purification unless otherwise indicated. Dichloromethane (CH2Cl2) was distilled from phosphoric
pentaoxide (P2O5). Optical rotations were taken on JASCO P-1030 polarimeter with a sodium lamp (D
line). FTIR spectra were measured on a JASCO FT/IR-420 infrared spectrophotometer. 1H NMR spectra
were recorded on either JEOL JNM-LA 300 (300 MHz), JEOL JNM-LA 400 (400 MHz), or Bruker
AVANCE 600 (600 MHz) spectrometer. Chemical shifts of 1H NMR spectrum were reported in parts per
13
million (ppm, δ) relative to CHCl3 (δ = 7.26) in CDCl3. C NMR spectra were recorded on an either
13
JEOL JNM-LA 300 (75 MHz) or JEOL JNM-LA 400 (100 MHz) spectrometer. Chemical shifts of C
NMR spectrum were reported in ppm (δ) relative to CHCl3 (δ = 77.0) in CDCl3. Low resolution mass
(LRMS) and high resolution mass (HRMS) spectra were obtained on a JEOL JMS-AX500 for fast atom
bombardment ionization (FAB), chemical ionization (CI), or electron ionization (EI). All reactions were
monitored by thin layer chromatography (TLC), which was performed with precoated plates (silica gel 60
F-254, 0.25 mm thickness, manufactured by Merck). TLC visualization was carried out by using UV
lamp (254 nm) or a charring solution (ethanoic p-anisaldehyde, ethanoic phosphomolybdic acid, aqueous
potassium permanganate, and butanoic ninhydrin). Daisogel IR-60 1002W (40/63 μm) was used for flash
column chromatography on silica gel. Compounds (6d) and (8) were prepared according to the literature
method.6 Structures of 10a and 11a were determined by comparisons of their spectral data with those of
the authentic data.5a Structures of 2a, 2b, and 10d were determined by comparisons of their NMR spectral

518
HETEROCYCLES, Vol. 66, 2005
data with those of the authentic samples.6
(S)-tert-Butyl 2-tert-butyldiphenylsilyloxymethyl-5-oxopyrrolidine-1-carboxylate (6b)
To a solution of 7 (497 mg, 4.32 mmol) in CH2Cl2 (21.6 mL) were added TBDPSCl (1.68 mL, 6.47
mmol), Et3N (0.902 mL, 6.47 mmol), and DMAP (52.8 mg, 0.432 mmol) at 0 oC. The mixture was stirred
for 18 h at rt, quenched with sat. NH4Cl (20 mL), and extracted with EtOAc (3 x 20 mL). The combined
organic layers were washed with brine (60 mL), dried over anhydrous MgSO4, filtered, and concentrated
under reduced pressure. To a solution of the residue in THF (21.6 mL) were added Boc2O (1.49 mL, 6.47
mmol), Et3N (0.902 mL, 6.47 mmol), and DMAP (52.8 mg, 0.432 mmol) at 0 oC. The mixture was stirred
for 19 h at rt, quenched with sat. NH4Cl (20 mL), and extracted with EtOAc (20 mL x 3). The combined
organic layers were washed with brine (60 mL), dried over anhydrous MgSO4, filtered, and concentrated
under reduced pressure. The residue was purified by flash column chromatography on silica gel
(hexane/EtOAc = 10/1-5/1) to give 6b (1.31 g, 67%) as colorless amorphous powder.
[α]21.3 -38.0o (c 0.75, CHCl3); IR (neat) 2985, 2931, 2858, 1789, 1750, 1712, 1473, 1428, 1367, 1312,
D
1153, 1112, 1031 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.63-7.57 (m, 4 H), 7.45-7.30 (m, 6 H), 4.21-4.16
(m, 1 H), 3.87 (dd, J = 10.5, 4.16 Hz, 1 H), 3.68 (dd, J = 10.5, 2.4 Hz, 1 H), 2.76 (dt, J = 17.3, 10.5 Hz, 1
13
H), 2.45-2.37 (m, 1 H), 2.14-2.10 (m, 2 H), 1.41 (s, 9 H), 1.02 (s, 9 H); C NMR (75 MHz, CDCl3) δ
174.9, 149.7, 135.5, 133.0, 132.6, 120.9, 129.8, 127.8, 82.6, 77.3, 65.0, 58.8, 32.3, 28.0, 26.8, 21.1, 19.1;
HRMS (FAB) m/z (M+H)+ calcd for [C26H35NO4Si+H]+ 454.2413, found 454.2415.
(R)-1-tert-Butyl 2-methyl 2-tert-butyldiphenylsilyloxymethyl-5-oxopyrrolidine-1,2-dicarboxylate
(6c)
o
To a solution of 8 (194 mg, 0.501 mmol) in CH2Cl2 (2.5 mL) was added TFA (2.5 mL) at 0 C. The
mixture was stirred at rt for 1 h and concentrated under reduced pressure. To a solution of the residue in
CH2Cl2 were added TBDPSCl (0.20 mL, 0.752 mmol), Et3N (105 μL, 0.752 mmol), and DMAP (6.1 mg,
0.05 mmol) at 0 oC. The mixture was stirred at rt under argon for 19 h, quenched with sat. NH4Cl (2 mL),
and extracted with EtOAc (20 mL x 3). The combined organic layers were washed with brine (60 mL),
dried over anhydrous MgSO4, filtered, and concentrated under reduced pressure. To a solution of the
residue in THF (2.5 mL) were added Boc2O (173 μL, 0.752 mmol), Et3N (105 μL, 0.752 mmol), and
DMAP (6.1 mg, 0.05 mmol) at 0 oC. The mixture was stirred at rt under argon for 18 h, quenched with sat.
NH4Cl (2 mL), and extracted with EtOAc (20 mL x 3). The combined organic layers were washed with
brine (6 mL), dried over anhydrous MgSO4, filtered, and concentrated under reduced pressure. The
residue was purified by flash column chromatography on silica gel (hexane/EtOAc = 8/1-6/1) to give 6c
(218 mg, 85%) as a colorless oil.

HETEROCYCLES, Vol. 66, 2005
519
[α]25 +10.9 o (c 4.76, CHCl3); IR (neat) 2955, 2858, 1792, 1748, 1715, 1429, 1369, 1309, 1257, 1157,
D
1113, 1074 cm-1; 1H NMR (300 MHz, CDCl3) δ 7.64-7.53 (m, 4 H), 7.43-7.31 (m, 6 H), 4.27 (d, J = 10.7
Hz, 1 H), 3.99 (d, J = 10.7 Hz, 1 H), 3.66 (s, 3 H), 2.80 (ddd, J = 17.5, 10.3, 8.4 Hz, 1 H), 2.56 (ddd, J =
17.5, 10.7, 4.4 Hz, 1 H), 2.31 (ddd, J = 12.9, 10.3, 4.4 Hz, 1 H), 2.09 (ddd, J = 12.9, 10.7, 8.4 Hz, 1 H),
1.36 (s, 9 H), 1.02 (s, 9 H); 13C NMR (75 MHz, CDCl3) δ 174.4, 171.8, 149.1, 135.7, 135.5, 132.9, 132.4,
130.0, 127.9, 83.6, 69.0, 65.5, 52.4, 31.6, 27.9, 26.8, 19.2; HRMS (FAB) m/z (M+H)+ calcd for
[C28H37NO6Si+H]+ 512.2468, found 512.2460.
General procedure for allylation with allyltrimethylsilane.
To a solution of 6a-d (0.100 mmol) in THF (0.5 mL) was added LiBEt3H (1 M solution in THF, 150 μL,
o
o
0.150 mmol) at -78 C. The mixture was stirred at -78 C under argon for 10 min, quenched with sat.
NaHCO3/30% H2O2 (1:1, 5 mL), stirred at rt for 3 h, and extracted with Et2O (5 mL x 3). The combined
organic layers were washed with brine (15 mL), dried over anhydrous MgSO4, filtered, and concentrated
under reduced pressure. To a solution of the residue in CH2Cl2 (0.5 mL) were added Ac2O (18.9 μL,
0.200 mmol) and DMAP (24.4 mg, 0.200 mmol) at 0 oC. The mixture was stirred for 18 h at rt, quenched
with sat. NH4Cl (0.5 mL), and extracted with Et2O (1 mL x 3). The combined organic layers were washed
with brine (1.5 mL), dried over anhydrous MgSO4, filtered, and concentrated under reduced pressure. To
a solution of the residue in CH2Cl2 (1.00 mL) were added allyltrimethylsilane (79.5 μL, 0.500 mmol) and
o
o
BF3-OEt2 (33.7μl, 0.125 mmol) at -78 C. The mixture was stirred for 10 min under argon at -78 C,
quenched with sat. NaHCO3 (1 mL), and extracted with Et2O (1 mL x 3). The combined organic layers
were washed with brine (3 mL), dried over anhydrous MgSO4, filtered, and concentrated under reduced
pressure. The residue was purified by flash column chromatography on silica gel (Hexane/AcOEt (20:1 to
1:3))to give a mixture of 10 and 11. The products ratios and yields are depicted in Table 1.
Allylation of 9a with 5.
10a and 11a were obtained as an inseparable mixture. These NMR spectral data were identical with those
of the authentic samples.5a
Allylation of 9b with 5.
An inseparable mixture of 10b and 11b, A, and B was obtained in 37 %, 15%, and 14% yields,
respectively. The structures of A and B were determined by their NOE spectral experiments. The cis:trans
ratio was calculated by the following equation: 10b:(11b+A+B) = 28:72.
10b and 11b.
Colorless oil; IR (neat) 3072, 2962, 2858, 1694, 1474, 1427, 1390, 1365, 1256, 1174, 1112, 997 cm-1; 1H

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HETEROCYCLES, Vol. 66, 2005
NMR (300 MHz, CDCl3) δ 7.68-7.60 (m, 4 H), 7.46-7.24 (m, 6 H), 5.81-5.61 (m, 1 H), 5.07-4.93 (m, 2
H), 3.95-3.70 (m, 7/2 H), 3.47-3.41 (m, 1/2 H), 2.63-2.47 (m, 1 H), 2.12-1.75 (m, 4 H), 1.71-1.62 (m, 1
13
H), 1.60 (s, 5/2 H), 1.35 (br, 2 H), 1.29 (s, 9/2 H), 1.05 (s, 4 H), 1.04 (s, 5 H); C NMR (100 MHz,
CDCl3) δ 154.8, 153.7, 135.7, 135.5, 133.8, 133.7, 133.6, 129.72, 129.68, 129.6, 127.7, 117.0, 116.98,
116.7, 79.21, 79.18, 79.1, 64.0, 63.7, 59.8, 58.8, 58.3, 57.8, 57.6, 38.7, 37.2, 28.64, 28.58, 28.47, 27.9,
27.0, 26.9, 26.3, 26.0, 25.8; HRMS (FAB) m/z (M+H)+ calcd for [C29H41NO3Si+H]+ 480.2934, found
480.2939.
(3S,4aS,7S)-Hexahydro-7-tert-butyldiphenylsilyloxymethyl-3-(trimethylsiliylmethyl)pyrrolo[1,2-c][1
,3]oxazin-1-one (A) .
Colorless oil; [α]23D -8.1o (c 0.88, CHCl3); IR (neat) 2956, 2854, 1698, 1427, 1312, 1250, 1113 cm-1;
1H NMR (600 MHz, CDCl3) δ 7.64-7.60 (m, 4 H), 7.41 (t, J = 7.4 Hz, 2 H), 7.37 (t, J = 7.3 Hz, 4 H),
4.29-4.25 (m, 1 H), 4.14-4.11 (m, 1 H), 4.02 (dd, J = 10.3, 4.4 Hz, 1 H), 3.79 (dd, J = 10.3, 2.3 Hz, 1 H),
3.59 (tt, J = 11.0, 4.9 Hz, 1 H), 2.15-2.10 (m, 2 H), 2.09-2.04 (m, 2 H), 1.42-1.30 (m, 2 H), 1.17 (dd, J =
13
14.5, 6.8 Hz, 1 H), 1.06 (s, 9 H), 0.92 (dd, J = 14.5, 7.7 Hz, 1 H), 0.088 (s, 9 H); C NMR (100 MHz,
CDCl3) δ 153.3, 135.7, 133.9, 133.7, 129.8, 127.8, 75.6, 64.3, 59.4, 57.7, 36.8, 32.9, 26.8, 25.5, 24.1, 19.2,
-1.05; HRMS (FAB) m/z (M+H)+ calcd for [C28H41NO3Si2+H]+ 496.2703, found 496.2708.
(3R,4aS,7S)-Hexahydro-7-tert-butyldiphenylsilyloxymethyl-3-(trimethylsiliylmethyl)pyrrolo[1,2-c][
1,3]oxazin-1-one (B) .
Colorless oil; [α]23D -47.4o (c 0.65, CHCl3); IR (neat) 2954, 2854, 1694, 1427, 1291, 1250, 1111 cm-1;
1H NMR (600 MHz, CDCl3) δ 7.65 (d, J = 7.3 Hz, 2 H), 7.62 (d, J = 7.2 Hz, 2 H), 7.43-7.36 (m, 6 H),
4.62 (dd, J = 11.9, 6.9 Hz, 1 H), 4.18 (dd, J = 10.3, 3.3 Hz, 1 H), 4.14 (m, 1 H), 3.81 (tt, J = 11.0, 4.6 Hz,
1 H), 3.64 (d, J = 10.3 Hz, 1 H), 2.18-2.07 (m, 2 H), 2.04-1.98 (m, 2 H), 1.72 (dd, J = 13.2, 4.6 Hz, 1 H),
1.43 (tt, J = 11.4, 10.8 Hz, 1 H), 1.28 (dd, J = 14.5, 10.3 Hz, 1 H), 1.06 (s, 9 H), 0.95 (dd, J = 14.5, 7.4 Hz,
1 H), 0.058 (s, 9 H); 13C NMR (100 MHz, CDCl3) δ 152.5, 135.74, 135.70, 133.6, 133.4, 129.84, 129.81,
127.9, 127.8, 74.6, 63.8, 59.6, 53.6, 33.6, 33.1, 26.8, 24.9, 22.2, 19.1, -1.38; HRMS (FAB) m/z (M+H)+
calcd for [C28H41NO3Si2+H]+ 496.2703, found 496.2708.
Allylation reaction of 9c with 5.
10c, 11c and C were obtained in 36%, 15% and 9% yields, respectively. The structure of C was
determined by NOE spectral experiment. The cis:trans ratio was calculated by the following equation:
(10c+C):11c = 75:25.

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521
(2R,5R)-1-tert-Butyl
2-methyl
5-allyl-2-tert-butyldiphenylsilyloxymethylpyrrolidine-1,2-di-
carboxylate (10c).
Colorless oil; [α]21.3D +16.6o (c 1.72, CHCl3); IR (neat) 3072, 2955, 2858, 1741, 1697, 1473, 1429, 1391,
1
1367, 1256, 1173, 1149, 1112, 1042 cm-1; H NMR (400 MHz, CDCl3) δ 7.64 (m, 4 H), 7.38 (m, 6 H),
5.81 (m, 1 H), 5.07 (d, J = 16.8 Hz, 1 H), 5.03 (d, J = 9.0 Hz, 1 H), 4.40 (d, J = 14.6 Hz, 1/3 H), 4.10-3.92
(m, 8/3H), 3.64 (s, 3 H), 2.80 (m, 3/5 H), 2.63 (m, 2/5 H), 2.15-2.38 (m, 4 H), 1.72 (m, 1 H), 1.47 (s,
37/10 H), 1.22 (s, 53/10 H), 1.04 (s, 6 H), 1.03 (s, 3 H); 13C NMR (75 MHz, CDCl3) δ 174.1, 173.9, 153.3,
152.6, 136.1, 136.0, 135.8, 135.7, 135.62, 135.57, 133.8, 133.5, 133.2, 133.1, 129.80, 129.78, 129.70,
127.84, 127.78, 127.73, 116.9, 80.1, 79.7, 69.7, 69.2, 65.9, 64.9, 59.9, 59.7, 52.1, 51.0, 38.7, 37.2, 34.7,
34.2, 28.5, 28.3, 27.1, 26.9, 19.3; HRMS (FAB) m/z (M+H)+ calcd for [C31H43NO5Si+H]+ 538.2989,
found 538.2986.
(2R,5S)-1-tert-Butyl
carboxylate (11c).
2-methyl
5-allyl-2-tert-butyldiphenylsilyloxymethylpyrrolidine-1,2-di-
Colorless oil; [α]24.6D +5.63o (c 2.01, CHCl3); IR (neat) 3072, 2955, 2858, 1742, 1698, 1429, 1390, 1366,
1156, 1112, 1042 cm-1; 1H NMR (400 MHz, CDCl3) δ 7.73-7.57 (m, 4 H), 7.38 (m, 6 H), 5.76 (m, 1 H),
5.01 (d, J = 18.6 Hz, 1 H), 4.99 (d, J = 10.2 Hz, 1 H), 4.43 (d, J = 14.9 Hz, 1/3 H), 4.20-3.89 (m, 8/3 H),
3.62 (s, 3 H), 2.70-2.57 (m, 2 H), 2.24-2.20 (m, 1 H), 2.08-1.98 (m, 1 H), 1.93-1.80 (m, 1 H), 1.75-1.65
13
(m, 1 H), 1.51 (s, 3 H), 1.26 (s, 6 H), 1.07 (s, 6 H), 1.05 (s, 3 H); C NMR (75 MHz, CDCl3) δ 173.9,
173.6, 154.2, 153.8, 136.0, 135.9, 135.78, 135.75, 135.72, 133.35, 133.32, 129.80, 129.77, 129.7, 129.6,
127.8, 127.7, 116.8, 116.7, 80.1, 79.7, 70.5, 70.0, 63.9, 62.5, 59.9, 59.8, 52.02, 51.96, 39.8, 39.2, 32.5,
31.1, 28.6, 28.5, 28.3, 28.2, 27.0, 26.9, 26.5, 26.1, 19.43, 19.38; HRMS (FAB) m/z (M+H)+ calcd for
[C31H43NO5Si+H]+ 538.2989, found 538.2991.
(3R,4aR,7R)-Methyl hexahydro-7-tert-butyldiphenylsilyloxymethyl-3-(trimethylsilylmethyl)-1-oxo-
1H-pyrrolo[1,2-c][1,3]oxazine-7-carboxylate (C).
Colorless oil; [α]28.5D + 9.0o (c 0.35, CHCl3); IR (neat) 2952, 2890, 2857, 1742, 1697, 1472, 1427, 1369,
1314, 1249, 1208, 1155, 1112, 1091 cm-1; 1H NMR (600 MHz, CDCl3) δ 7.64 (d, J = 6.8 Hz, 1 H), 7.62
(d, J = 6.6 Hz, 1 H), 7.42 (t, J = 7.1 Hz, 2 H), 7.37 (t, J = 7.1 Hz, 4 H), 4.50 (d, J = 10.5 Hz, 1 H),
4.37-4.33 (m, 1 H), 3.97 (d, J = 10.5 Hz, 1 H), 3.76 (tt, J = 11.3, 4.3 Hz, 1 H), 3.65 (s, 3 H), 2.52 (td, J =
13.0, 6.7 Hz, 1 H), 2.16 (m, 1 H), 2.08 (m, 1 H), 1.93 (dd, J = 13.0, 7.2 Hz, 1 H), 1.79 (dtd, J = 12.7, 11.6,
7.3 Hz, 1 H), 1.55 (td, J = 13.1, 11.5 Hz, 1 H), 1.22 (dd, J = 14.5, 6.7 Hz, 1 H), 1.06 (s, 9 H), 1.00 (dd, J =
14.5, 7.7 Hz, 1 H), 0.10 (s, 9 H); 13C NMR (100 MHz, CDCl3) δ 172.7, 151.8, 135.6, 135.5, 133.6, 133.0,
129.74, 129.69, 127.74, 127.70, 76.8, 69.7, 63.0, 58.9, 52.2, 36.8, 31.4, 31.2, 26.9, 24.3, 19.4, -0.82;

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HETEROCYCLES, Vol. 66, 2005
HRMS (FAB) m/z (M+H)+ calcd for [C30H43NO5Si2+H]+ 554.2758, found 554.2759.
Allylation reaction of 9d with 5.
10d was obtained as a sole product. The NMR spectral data was identical with those of the authentic
data.6
Addition of allylcopper reagent to 9a-d.
To a suspention of CuBr-SMe2 (822 mg, 4 mmol) in THF (5 mL) was added dropwise allylmagnesium
o
o
bromide (1 M solution in Et2O, 4 mL, 4 mmol) at -40 C. The mixture was stirred for 45 min at -40 C
under argon, cooled to -78 oC, and stirred for 15 min. To the mixture was added dropwise BF3-Et2O (1.08
mL, 4 mmol) at -78 oC. The mixture was stirred for 15 min at -78 oC. To the mixture was added dropwise
a solution of 9a-d (1 mmol) in THF (5 mL), stirred for 15 min, and gradually warmed to 0 oC for 3 h. The
reaction mixture was quenched with sat. NH4Cl and concd NH3 (1:1, 20 mL), stirred for 1 h at rt, and
extracted with Et2O (3 x 20 mL). The combined organic layers were washed with brine (60 mL), dried
over anhydrous MgSO4, filtered, and concentrated under reduced pressure. The residue was purified by
flash column chromatography (hexane/AcOEt (20:1 to 3:1))on silica gel. The products ratios and yields
are depicted in Table 1.
Allylation of 9a with the allylcopper reagent.
10a and 11a were obtained as an inseparable mixture. These NMR spectral data were identical with those
of the authentic sample.5a
Allylation of 9b with the allylcopper reagent.
10b and 11b were obtained as an inseparable mixture. The NMR spectral data was identical with those of
10b and 11b obtained via the allylation reaction of 9b with 5.
Allylation of 9c with the allylcopper reagent.
10c and 11c were obtained. These spectral data were identical with those of 10c and 11c obtained via the
allylation reaction of 9c with 5.
Allylation of 9d with the allylcopper reagent.
10d and 11d were obtained as an inseparable mixture.
10d and 11d (8:2): IR (neat) 2977, 2953, 1746, 1732, 1700, 1655, 1457, 1436, 1379, 1252, 1171, 1042
1
cm-1; H NMR (300 MHz, CDCl3) δ 7.44-7.37 (m, 1/5 H), 7.37-7.28 (m, 4/5 H), 5.92-5.61 (m, 2 H),
5.06-4.92 (m, 2 H), 4.15-3.87 (m, 1 H), 3.73-3.63 (m, 6 H), 2.78-2.49 (m, 1 H), 2.35-1.62 (m, 5 H),

HETEROCYCLES, Vol. 66, 2005
523
13
1.41-1.27 (m, 9 H); C NMR (75 MHz, CDCl3) δ 172.8, 172.57, 172.56, 172.51, 172.4, 172.3, 166.9,
166.59, 166.58, 166.56, 152.9, 152.4, 148.4, 147.5, 147.1, 146.1, 135.5, 135.3, 135.2, 134.9, 119.3, 119.0,
118.8, 117.5, 117.35, 117.31, 80.6, 80.5, 70.1, 69.72, 69.70, 59.6, 59.5, 59.01, 58.96, 52.8, 52.6, 51.8,
51.74, 51.71, 39.0, 38.3, 38.0, 36.9, 36.1, 35.0, 28.4, 28.2, 28.0, 26.9, 25.1; HRMS (FAB) m/z (M+H)+
calcd for[C18H27NO6+H]+ 354.1916, found 354.1917.
Removal of the Boc group from 10 and 11
To a solution of an inseparable mixture of 10b and 11b in CH2Cl2 (0.1 M) were added TMSOTf (2 equiv)
o
and 2,6-lutidine (3 equiv) at 0 C. The mixture was stirred at rt, quenched with sat. NaHCO3, and
extracted with EtOAc (5 mL x 3). The combined organic layers were washed with brine, dried over
anhydrous MgSO4, filtered, and concentrated under reduced pressure to give crude amines quantitatively.
The residue was purified by preparative TLC (hexane/AcOEt (4:1)) to give 12b and its isomers. A
mixture of 10c and 11c were transformed to 12c and its isomer in the same manner.
(2S,5S)-2-Allyl-5-(tert-butyldiphenylsilyloxymethyl)pyrrolidine (12b).
Pale yellow oil; IR (neat) 2956, 2930, 2858, 1641, 1428, 1112 cm-1; 1H NMR (600 MHz, CDCl3) δ 7.66
(d, J = 6.8 Hz, 4 H), 7.43 (t, J = 7.1 Hz, 2 H), 7.38 (t, J = 7.3 Hz, 4 H), 5.77 (ddt, J = 17.1, 9.3, 7.0 Hz, 1
H), 5.08 (dd, J = 17.1, 0.8 Hz, 1 H), 5.04 (dd, J = 9.3, 0.8 Hz, 1 H), 3.56 (dd, J = 10.2, 5.5 Hz, 1 H), 3.54
(dd, J = 10.2, 6.4 Hz, 1 H), 3.43 (quint, J = 6.2 Hz, 1 H), 3.15 (quint, J = 6.5 Hz, 1 H), 2.19 (t, J = 6.6 Hz,
2 H), 1.98 (br, 1 H), 1.91-1.86 (m, 2 H), 1.48-1.35 (m, 2 H), 1.06 (s, 9 H); 13C NMR (75 MHz, CDCl3) δ
136.3, 135.6, 129.8, 127.8, 116.6, 66.6, 58.8, 56.8, 40.7, 31.0, 27.1, 26.8, 19.2;
(2R)-Isomer of 12b.
1H NMR (600 MHz, CDCl3) δ 7.67 (d, J = 6.0 Hz, 4 H), 7.43 (t, J = 7.1 Hz, 2 H), 7.38 (t, J = 7.3 Hz, 4 H),
5.83 (ddt, J = 17.1, 9.5, 7.0 Hz, 1 H), 5.11 (dd, J = 17.1, 0.8 Hz, 1 H), 5.05 (dd, J = 9.5, 0.8 Hz, 1 H), 3.73
(dd, J = 10.2, 4.6 Hz, 1 H), 3.62 (dd, J = 10.2, 5.1 Hz, 1 H), 3.28 (quint, J = 6.7 Hz, 1 H), 3.18 (quint, J =
6.6 Hz, 1 H), 2.45 (br, 1 H), 2.26 (t, J = 6.7 Hz, 2 H), 1.92-1.84 (m, 1 H), 1.78 (dq, J = 12.6, 7.8 Hz, 1 H),
1.65-1.58 (m, 1 H), 1.48-1.35 (m, 1 H), 1.06 (s, 9 H); 13C NMR (75 MHz, CDCl3) δ 135.9, 135.7, 129.8,
127.8, 116.9, 66.4, 60.1, 58.7, 40.3, 27.3, 26.8, 19.1; HRMS (FAB) m/z (M+H)+ calcd for
[C24H33NOSi+H]+ 380.2409, found 380.2416.
(2R,5R)-Methyl 5-allyl-2-tert-butyldiphenylsilyloxymethylpyrrolidine-2-carboxylate (12c).
Pale yellow oil; [α]24.2 -4.1o (c 3.57, CHCl3); IR (neat) 2931, 2858, 1738, 1429, 1234, 1113, 998 cm-1;
D
1H NMR (600 MHz, CDCl3) δ 7.68 (d, J = 6.7 Hz, 2 H), 7.65 (d, J = 6.7 Hz, 2 H), 7.43 (t, J = 6.8 Hz, 2
H), 7.38 (t, J = 6.9 Hz, 4 H), 5.80 (ddt, J = 17.1, 10.1, 7.0 Hz, 1 H), 5.10 (d, J = 17.1 Hz, 1 H), 5.04 (d, J

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HETEROCYCLES, Vol. 66, 2005
= 10.1 Hz, 1 H), 3.82 (d, J = 9.5 Hz, 1 H), 3.72 (s, 3 H), 3.64 (d, J = 9.5 Hz, 1 H), 3.11 (dt, J = 14.8, 6.6
Hz, 1 H), 2.37 (br, 1 H), 2.27 (quint, J = 6.9 Hz, 1 H), 2.21-2.15 (m, 2 H), 1.84-1.79 (m, 1 H), 1.66 (dt, J
= 13.2, 9.2 Hz, 1 H), 1.36 (ddt, J = 12.2, 9.0, 8.8 Hz, 1 H), 1.04 (s, 9 H); 13C NMR (100 MHz, CDCl3) δ
176.2, 136.0, 135.7, 135.6, 129.6, 127.6, 116.4, 70.4, 68.9, 57.7, 52.1, 40.6, 31.8, 30.8, 26.7, 19.3; HRMS
(FAB) m/z (M+H)+ calcd for [C26H35NO3Si+H]+ 438.2464, found 438.2464.
(2S)-Isomer of 12c.
Pale yellow oil; [α]24.4D -7.2o (c 1.44, CHCl3); IR (neat) 2931, 2858, 1738, 1473, 1429, 1229, 1113 cm-1;
1H NMR (600 MHz, CDCl3) δ 7.70 (d, J = 6.7 Hz, 1 H), 7.65 (d, J = 6.7 Hz, 1 H), 7.42 (t, J = 7.2 Hz, 2
H), 7.38 (t, J = 7.2 Hz, 4 H), 5.83 (ddt, J = 17.2, 10.1, 7.0 Hz, 1 H), 5.08 (d, J = 17.2 Hz, 1 H), 5.02 (d, J
= 10.1 Hz, 1 H), 3.91 (d, J = 9.3 Hz, 1 H), 3.72 (s, 3 H), 3.66 (d, J = 9.3 Hz, 1 H), 3.28 (dt, J = 14.7, 6.5
Hz, 1 H), 2.23 (quint, J = 6.8 Hz, 1 H), 2.17 (quint, J = 6.5 Hz, 1 H), 2.06 (dt, J = 13.1, 8.0 Hz, 1 H),
1.84-1.80 (m, 1 H), 1.74 (ddd, J = 13.7, 9.5, 4.8 Hz, 1 H), 1.36 (ddt, J = 11.9, 8.7, 8.6 Hz, 1 H), 1.02 (s, 9
H); 13C NMR (100 MHz, CDCl3) δ 177.0, 136.3, 135.9, 135.8, 133.6, 133.5, 129.76, 129.74, 127.8, 127.7,
116.4, 70.8, 70.5, 57.8, 52.0, 40.9, 31.1, 30.1, 26.5, 19.1; HRMS (FAB) m/z (M+H)+ calcd for
[C26H35NO3Si+H]+ 438.2464, found 438.2456.
ACKNOLEDGEMENT
Financial support was provided by JSPS KAKENHI (No. 16201045 and 16073214).
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