Highly diastereoselective N-nitrosation of chiral (E)-2-(benzylidene-amino)ethanols with nitric oxide

Article abstract of DOI:10.1016/j.tetasy.2008.08.024

N-Nitrosation of (E)-(S)-2-(benzylidene-amino)ethanols 2 with nitric oxide occurred highly diastereoselectively, to give the (2S,4S)-diastereomer dominant N-nitroso-(2S,4S)-1,3-oxazolidines in good yield. Intermediate 2 was prepared from the reaction of b

Full text of DOI:10.1016/j.tetasy.2008.08.024

Tetrahedron: Asymmetry 19 (2008) 2078–2083
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Tetrahedron: Asymmetry
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Highly diastereoselective N-nitrosation of chiral
(E)-2-(benzylidene-amino)ethanols with nitric oxide
Lijun Peng a, Jiantao Wang a, Chuanmin Sun a, Zhongquan Liu b, Longmin Wu a,
*
a State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, PR China
b Institute of Organic Chemistry, Gannan Normal University, Ganzhou 341000, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 23 July 2008
Accepted 16 August 2008
N-Nitrosation of (E)-(S)-2-(benzylidene-amino)ethanols 2 with nitric oxide occurred highly diastereo-
selectively, to give the (2S,4S)-diastereomer dominant N-nitroso-(2S,4S)-1,3-oxazolidines in good yield.
Intermediate 2 was prepared from the reaction of benzaldehyde 1 with (S)-2-aminoethanol.
Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction
2. Results and discussion
N-Nitroso compounds have been considered to cause mutagen-
esis and carcinogenesis,1 in addition to being utilized for enzyme
inhibition and active site mapping.2 As such, suppressing the for-
mation of nitrosamines has been thought to protect biological tis-
sues from cancer. Meanwhile, some nitrosamines have been widely
used as nitric oxide (NO) releasing drugs in biomedicine.3 There-
fore, nitrosation studies may mimic interactions between biologi-
cal tissues and nitrosating species, such as NO, N2O3, NO+, NO2/
N2O4, and NOSCN, which generate mutagenic nitrosamines/pep-
tides and nitrosate and deaminate DNA.4
The reaction of benzaldehydes 1 with enantiopure (S)-2-amino-
ethanols afforded (E)-(S)-2-(benzylidene-amino) ethanols 2 in the
primary steps. The resulting 2 reacted with NO in high diastereo-
selectivity to give (2S,4S)-diastereomer dominant N-nitroso-
(2S,4S)-1,3-oxazolidines 3 in good yield with various ratios of
(E)-(2S,4S)-3 to (Z)-(2S,4S)-3 (Scheme 1). The newly established
tertiary carbon center was constructed highly diastereoselectively
with an (S)-configuration.
Initial experiments using 2b as a representative were concen-
trated on finding a suitable temperature, at which the reaction
occurred with higher stereoselectivity. It was found that the ratio
of (2S,4S)-3b to (2R,4S)-3b reached up to 95/5 at room temperature
and up to 99/1 at 0 °C. It seemed that lower temperatures favored
the stereochemistry more.
In our previous work,5 we reported the reaction of NO with (E)-
2-(benzylidene-amino)ethanol, which afforded an (E)-rotamer
dominant mixture of (E)- and (Z)-N-nitroso-2-aryl-1,3-oxazolidine,
wherein a tertiary carbon center was newly established. In con-
junction with our continuing interest in the N-nitrosation of
amines,5 further studies were carried out to extend the 2-amino-
ethanol scope for chiral (S)-2-aminoethanols. It was found that
the construction of a new tertiary carbon center in N-nitroso-2-
aryl-1,3-oxazolidines occurred highly diastereoselectively.
In a representative experiment, treatment of 1 mmol of o-chloro-
benzaldehyde 1b with 1 mmol of (S)-2-amino-3-phenylpropan-
1-ol {½a 2D0
¼ ꢁ23 (c 3.0, ethanol)} and 3 mmol of MgSO4 in 30 mL
ꢀ
of anhydrous tetrahydrofuran (THF) for 1 h gave rise to a mixture
of chain- and ring-2b with an (S)-configuration. Purified NO was
R
(S )
R
R
R
(S )
(S )
(S )
OH
H
R
CHO
(S )
O
HN
O
N
O
N
O
N
N
N
(S )
NO (trace O2)
THF, 0 oC, 2 h
(S )
H2N
OH
O
X
THF, MgSO4, 1h
X
X
X
X
Z-(2S,4S)-3
E-(2S,4S)-3
Overall yield up to 91%
ring-2
1
chain-2
Scheme 1.
* Corresponding author. Tel.: +86 931 8913210; fax: +86 931 8915557.
E-mail address: nlaoc@lzu.edu.cn (L.M. Wu).
0957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.08.024

L. Peng et al. / Tetrahedron: Asymmetry 19 (2008) 2078–2083
2079
bubbled through the above-mentioned stirred solution at 0 °C for
ca. 2 h. The stock solution was kept at a pressure of up to +10 mm
H2O column over local atmospheric pressure. After completion of
the reaction, as indicated by TLC, the mixture was concentrated un-
der vacuum, isolated and purified by column chromatography on
silica gel (200–300 mesh, ethyl acetate-petroleum ether), and
recrystallized from ethyl acetate, yielding colorless crystal 3b
(278 mg, 92% yield), N-nitroso-4-benzyl-2-(40-chlorophenyl)-1,3-
oxazolidine.
The two isomers of 3b, major 3b (99%) and minor 3b (1%), were
isolated. They were characterized by 1H and 13C NMR, MS, HRMS,
and X-ray crystallography diffraction. X-ray analysis carried out
on single crystals of major 3b slowly grown in a mixed solvent of
ethyl acetate and petroleum ether (1:20, v/v) (Fig. 1, the deposition
number: CCDC 630583) clearly shows that major 3b has a (2S,4S)-
configuration with an (E)-conformation in the solid, where the
(4S)-configuration of (S)-2-amino-3-phenylpropan-1-ol is known.
Figure 2. Molecular structure of (2R,4S)-3b (CCDC 632602).
As such, major 3b is termed (2S,4S)-3b {½a D20
¼ ꢁ49 (c 0.90,
ꢀ
CHCl3)}. It is present in a single (E)-conformation in the solid. 1H
NMR data for (2S,4S)-3b indicate that its two rotamers, (E)-
(2S,4S)-3b and (Z)-(2S,4S)-3b, are in equilibrium with a ratio of
1.4:1 in solution. Minor 3b was characterized to possess a
(2R,4S)-configuration {½a D20
¼ þ144 (c 0.4, CHCl3)}, a diastereomer
ꢀ
of (2S,4S)-3b, and termed (2R,4S)-3b. X-ray crystallography
Figure 3. Molecular structure of (2S,4S)-3d (CCDC 632025).
Figure 1. Molecular structure of (2S,4S)-3b (CCDC 630583).
Figure 4. Molecular structure of (2R,4S)-3i (CCDC 630584).
H
H
O
O
(S)
(S)
(S)
R
R
H
Ph
N
N
Ph
H
(E)-chain-2
(Z)-chain-2
H
H+
H
_
_
R
R
R
.
N
(S)
N
(S)
N
O
(S)
.
(S)
- H+
R
H
(a)
Ph
(S)
H
O
+
Ph
(S)
H
Ph
(S)
H
O
O
H
N
H
Ph
H
H
H
(E)-chain-2
(2S,4S)-ring-2''
(2S,4S)-ring-2
(2S,4S)-ring-2'
O
-
OH
(b)
(S)
(S)
R
R
H
(S)
(S)
O
O
R
R
+
H
+
H
HN
HN
HN
Ph
H
Ph
N
(S)
(R)
Ph
H
Ph
chain-2'
(2S,4S)-ring-2
(2R,4S)-ring-2
(E)-chain-2
Scheme 2.

2080
L. Peng et al. / Tetrahedron: Asymmetry 19 (2008) 2078–2083
Table 1
N-Nitrosation of (E)-(S)-2-(benzylidene-amino)ethanols with NO in THF
Entry
Benzaldehyde
X
R
Chain-2/ring-2a
Yield of 3b (%)
(2S,4S)-3/(2R,4S)-3c
(E)-(2S,4S)-3/(Z)-(2S,4S)-3d
(E)-(2R,4S)-3/(Z)-(2R,4S)-3d
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
H
p-Cl
o-Cl
p-NO2
p-OCH3
o-OCH3
p-CH3
H
p-Cl
o-Cl
p-NO2
p-OCH3
o-OCH3
p-CH3
Bn
Bn
Bn
Bn
Bn
Bn
Bn
Ph
Ph
Ph
Ph
Ph
Ph
Ph
98:2
96:4
95:5
90:10
87:13
90:10
94:6
99:1
98:2
95:5
92:8
95:5
93:7
94:6
87
92
91
91
85
83
87
90
91
89
90
84
83
88
98:2
99:1
99:1
92:8
97:3
95:5
95:5
93:7
98:2
99:1
93:7
96:4
95:5
93:7
1.9:1
1.4:1
1.5:1
1.4:1
1.5:1
1.6:1
2.3:1
2.2:1
2.3:1
2.0:1
1.7:1
1.9:1
2.3:1
1.4:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
1:1
a
The ratio of chain-2 to ring-2 was evaluated using the characteristic 1H NMR peaks at 8.69–8.14 (N@CH) and 5.69–5.30 ppm (N–CH–O).
Isolated yields after column chromatography.
b
c
The ratio was estimated using individual isolated yields.
d
The ratios were evaluated using the characteristic 1H NMR peaks at 6.516–6.917 ((E)-3, N–CH–O) and 6.293–6.541 ppm ((Z)-3, N–CH–O).
diffraction (Fig. 2, the deposition number: CCDC 632602) showed
The diastereomeric nature of all the –N–CH–O protons of prod-
uct 3 in their 1H NMR spectra, due to the bent nature of the N@O
bond and its mutual exchange, was clearly observed.5,7 The 1H
NMR peak separation seems to be strongly dependent on the
4-substituent. A benzyl group leads to a bigger separation of
0.27–0.42 ppm, whereas a phenyl group causes a smaller separa-
tion of less than 0.1 ppm (Table 2). The ratio of (E)-(2S,4S)-3 to
(Z)-(2S,4S)-3 in Table 1 was determined from the 1H NMR peak
area ratio of –N–CH–O corresponding to these two compounds.
Otherwise, the electronic feature of substituents on the benz-
ene ring of the benzaldehyde affects more or less the product
yield. An OCH3 substituent on the benzene ring of benzaldehyde
seems to give rise to a lower yield, as in the case of 1e, 1f, 1l,
and 1m.
the presence of a single (E)-conformation in solid. In solution,
(2R,4S)-3b exists in both (E)-(2R,4S)-3b and (Z)-(2R,4S)-3b confor-
mations with a ratio of 1:1. Similarly, Figures 3 and 4 show that
both (2S,4S)-3d and (2R,4S)-3i are present in a single (E)-conforma-
tion in the solid.
It is assumed that the N-nitrosation would not significantly
influence the chiral configuration of C-2 in ring-2. Hence, the ste-
reochemistry occurs in the cycloaddition of chain-2 during the tau-
tomerism of 2. The observed diastereoselectivity maybe attributed
to three effects: (a) The imine moiety in chain-2 is in a more stable
(E)-conformation, (b) its N@C double bond is polarized to result in
most d+ on the carbon atom. This favors an intramolecular nucleo-
philic attack of the Lewis basic oxygen on the carbon atom with d+
to undergo a cycloaddition (path a in Scheme 2), giving an interme-
diate (2S,4S)-ring-20 with an (S)-configuration at C-2. Path b via a
secondary carbocation chain-20 formed from protonation by the
hydroxyl group is obviated from the guess mechanisms because
it will lead to a final 50:50 mixture of (2S,4S)- and (2R,4S)-3b,
and (c) a stereoelectronic effect strongly influences the stereo-
chemistry of the (2S,4S)-ring-20 in the cycloaddition reaction. This
stereoelectronic effect is caused by the nitrogen electron pair,
which is oriented anticlinal to both the R (benzyl or phenyl) and
phenyl groups on the five-membered ring during the cycloaddition
reaction.6 Such a stereoelectronic effect lowers the energy of
(2S,4S)-ring-20, accordingly. Only an (S)-configuration at C-4 can
lead to these favorable orientations.
3. Conclusion
We have demonstrated that NO-mediated N-nitrosation con-
verts (E)-(S)-2-(benzylidene-amino)ethanols to N-nitroso-(2S,4S)-
1,3-oxazolidines, and the reaction occurs efficiently and highly
diastereoselectively. The resulting oxazolines are present in a
single (E)-conformation in solid, but they exist in both (E)- and
(Z)-conformations with various ratios in solution. The products
maybe used as potential NO donors. The homolytic dissociation
energy of N–NO bonds has been estimated to be 28 kcal molꢁ1 8
.
4. Experimental
4.1. General
Table 2
1H NMR data for –N–CH–O protons of 3
All reagents were purchased from Alfa Aesar, and used as
received. Solvents for reaction were treated by standard proce-
dures prior to use.9 Analytical thin-layer chromatography (TLC)
was performed on silica gel precoated glass plates (0.25 mm thick-
ness, 60F-254, E. Merck). Visualization was accomplished by an
irradiation with a UV light at 254 nm. Flash chromatography was
carried out using silica gel (200–300 mesh). NO was produced by
the reaction of a 1 M H2SO4 solution with a saturated aqueous
solution of NaNO2 under an argon atmosphere. H2SO4 was added
dropwise. NO was carried by argon and purified by passing through
a series of scrubbing flasks containing 4 M NaOH, distilled water,
and CaCl2 in this order.
Product
X
R
(E)-(2S,4S)-
3 (ppm)
(Z)-(2S,4S)-
3 (ppm)
d(E)–(Z) (ppm)
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
H
p-Cl
o-Cl
p-NO2
p-OCH3
o-OCH3
p-CH3
H
p-Cl
o-Cl
P-NO2
p-OCH3
o-OCH3
p-CH3
Bn
Bn
Bn
Bn
Bn
Bn
Bn
Ph
Ph
Ph
Ph
Ph
Ph
Ph
6.67
6.68
6.95
6.82
6.60
6.92
6.65
6.77
6.73
6.95
6.86
6.69
6.92
6.64
6.36
6.34
6.54
6.42
6.33
6.54
6.33
6.70
6.64
6.81
6.69
6.52
6.82
6.59
0.31
0.34
0.41
0.40
0.27
0.38
0.32
0.07
0.09
0.14
0.17
0.17
0.10
0.05
1H and 13C NMR spectra were recorded in CDCl3 on a Varian
MercuryPlus 300 or a Varian Avance 600 MHz NMR spectrometer.
MS data were obtained with EI (70 eV) on an HP 5988 spectro-

L. Peng et al. / Tetrahedron: Asymmetry 19 (2008) 2078–2083
2081
meter by a direct inlet at 70 eV. High-resolution mass spectral
4.2.4. Compound (E)-(2S,4S)-3d and (Z)-(2S,4S)-3d
analysis (HRMS) data were obtained on a Bruker Daltonics Apex
II FT-ICR using an electrospray ionization technique. IR spectra
were recorded on a Perkin Elmer Paragon 1000 spectrometer,
and are reported in cmꢁ1. X-ray crystallography diffractions were
Colorless crystals, mp 69 °C; ½a D20
¼ ꢁ52 (c 1.00, CHCl3); IR (KBr)
ꢀ
mmax 3440 (vs), 3078 (vs), 2926 (s), 1952 (s), 1523 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 313 (M+, 35), 283 (70), 191 (75), 150
(100), 91 (90), 89 (30); HR-MS-ESI m/z calcd for C16H15N3O4 + Na
336.0954, found 336.0959, error ꢁ2.0 ppm. (E)-(2S,4S)-3d: 1H
NMR (300 MHz, CDCl3) d 7.10–8.27 (m, 9H, –Ph-p-NO2, –Ph), 6.82
(s, 1H, –N–CH–O), 4.71–4.75 (m, 1H, –N–CH), 4.12–4.25 (m, 2H,
–O–CH2), 3.06–3.15 (m, 1H, –CH2–Ph), 2.64–2.72 (dd, J = 9.0,
13.2 Hz, 1H, –CH2–Ph); 13C NMR (75 MHz, CDCl3) d 142.9, 135.7,
134.2 (2C), 128.5 (2C), 128.3 (2C), 127.7 (2C), 123.0, 90.8, 69.9,
60.6, 55.4, 36.6. (Z)-(2S,4S)-3d: 1H NMR (300 MHz, CDCl3) d 7.10–
8.27 (m, 9H, –Ph-p-NO2, –Ph), 6.42 (s, 1H, –N–CH–O), 5.22–5.27
(m, 1H, –N–CH), 4.12–4.25 (m, 2H, –O–CH2), 3.35–3.42 (m, 1H, –
CH2–Ph), 3.06–3.15 (m, 1H, –CH2–Ph); 13C NMR (75 MHz, CDCl3)
d 142.3, 135.4, 134.0 (2C), 128.4 (2C), 128.0 (2C), 127.1 (2C),
123.3, 88.6, 69.6, 60.6, 55.8, 39.6.
carried out on
Diffractometer.
a
Bruker SMART APEX II Single-Crystal
4.2. Characterization data for N-nitroso-1,3-oxazolidines (3)
4.2.1. Compound (E)-(2S,4S)-3a and (Z)-(2S,4S)-3a
Colorless crystals, mp 62–63 °C; ½a D20
¼ ꢁ45 (c 0.85, CHCl3); IR
ꢀ
(KBr) mmax 3434 (vs), 3010 (vs), 2892 (s), 1904 (s), 1558 (s, msym
NO) cmꢁ1; MS (EI, 70 eV) m/z 268 (M+, 25), 238 (50), 208 (65),
105 (100), 91 (90); HR-MS-ESI m/z calcd for C16H16N2O2 + Na
291.1205, found 291.1207, error ꢁ1.8 ppm. (E)-(2S,4S)-3a: 1H
NMR (600 MHz, CDCl3) d 7.35–7.46 (m, 10H, –Ph), 6.67 (s, 1H,
–N–CH–O), 4.75–4.77 (m, 1H, –N–CH), 4.06–4.18 (m, 2H, –O–
CH2), 3.19–3.21 (dd, J = 4.2, 14.6 Hz, 1H, –CH2–Ph), 2.60–2.65 (dd,
J = 9.6, 14.6 Hz, 1H, –CH2–Ph); 13C NMR (150 MHz, CDCl3) d
138.5, 134.2, 133.6, 129.5 (2C), 128.4 (2C), 127.9 (2C), 127.3 (2),
126.9, 91.0, 69.5, 56.3, 36.2. (Z)-(2S,4S)-3a: 1H NMR (600 MHz,
CDCl3) d 7.35–7.46 (m, 10H, –Ph), 6.36 (s, 1H, –N–CH–O), 5.20–
5.22 (m, 1H, –N–CH), 4.06–4.18 (m, 2H, –O–CH2), 3.40–3.44 (dd,
J = 6.2, 13.8 Hz, 1H, –CH2–Ph), 3.10–3.13 (dd, J = 9.4, 13.2 Hz, 1H,
–CH2–Ph); 13C NMR (150 MHz, CDCl3) d 135.8, 138.0, 135.0,
131.1, 129.3 (2C), 128.4 (2C), 128.0 (2C), 127.6 (2C), 88.7, 69.1,
60.3, 39.4.
4.2.5. Compound (E)-(2S,4S)-3e and (Z)-(2S,4S)-3e
Colorless crystals, mp 62 °C; ½a D20
¼ ꢁ43 (c 1.00, CHCl3); IR (KBr)
ꢀ
mmax 3442 (vs), 3051 (vs), 2944 (s), 1964 (s), 1528 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 298 (M+, 85), 267 (25), 238 (30), 136
(100), 117 (55), 91 (80); HR-MS-ESI m/z calcd for C17H18N2O3 + H
299.1393, found 299.1395, error ꢁ1.2 ppm. (E)-(2S,4S)-3e: 1H
NMR (300 MHz, CDCl3) d 6.86–7.46 (m, 9H, –Ph-p-OCH3, –Ph),
6.60 (s, 1H, –N–CH–O), 4.68–4.73 (m, 1H, –N–CH), 4.13–4.23 (m,
2H, –O–CH2), 3.84 (s, 3H, –O–CH3), 3.02–3.13 (m, 1H, –CH2–Ph),
2.64–2.72 (dd, J = 8.9, 12.8 Hz, 1H, –CH2–Ph); 13C NMR (75 MHz,
CDCl3) d 136.5, 135.2, 129.6, 128.6 (2C), 128.3 (2C), 128.0 (2C),
127.7 (2C), 123.0, 92.8, 69.9, 60.6, 58.1, 36.6. (Z)-(2S,4S)-3e: 1H
NMR (300 MHz, CDCl3) d 6.86–7.46 (m, 9H, –Ph-p-OCH3), 6.33 (s,
1H, –N–CH–O), 5.22–5.27 (m, 1H, –N–CH), 4.12–4.25 (m, 2H, –O–
CH2), 3.784(s, 3H, –O–CH3), 3.35–3.42 (m, 1H, –CH2–Ph), 3.06–
3.15 (m, 1H, –CH2–Ph); 13C NMR (75 MHz, CDCl3) d 136.1, 134.8,
129.1, 128.1 (2C), 127.9 (2C), 127.1 (2C), 126.9 (2C), 123.3, 89.6,
69.0, 60.6, 58.7, 39.4.
4.2.2. Compound (E)-(2S,4S)-3b and (Z)-(2S,4S)-3b
Colorless crystals, mp 63.4 °C; ½a D20
¼ ꢁ49 (c 0.90, CHCl3); IR
ꢀ
(KBr) mmax 3427 (vs), 3024 (vs), 2892 (s), 1914 (s), 1582 (s, msym
NO) cmꢁ1; MS (EI, 70 eV) m/z 302 (M+, 18), 272 (65), 192 (70),
118 (100), 91 (90), 89 (30); HR-MS-ESI m/z calcd for
C
16H15N2O2Cl + Na 325.0818, found 325.0826, error ꢁ2.4 ppm.
(E)-(2S,4S)-3b: 1H NMR (600 MHz, CDCl3) d 7.16–7.43 (m, 9H,
–Ph-p-Cl, –Ph), 6.68 (s, 1H, –N–CH–O), 4.69–4.73 (m, 1H, –N–
CH), 4.05–4.16 (m, 2H, –O–CH2), 3.17–3.19 (dd, J = 3.6, 13.2 Hz,
1H, –CH2–Ph), 2.59–2.63 (dd, J = 9.6, 13.2 Hz, 1H, –CH2–Ph); 13C
NMR (150 MHz, CDCl3) d 136.2, 135.7, 134.9, 129.3, 129.0 (2C),
128.8 (2C), 128.3 (2C), 127.1 (2C), 91.6, 69.8, 56.7, 36.8.
(Z)-(2S,4S)-3b: 1H NMR (600 MHz, CDCl3) d 7.16–7.43 (m, 9H,
–Ph-p-Cl, –Ph), 6.34 (s, 1H, –N–CH–O), 5.17–5.19 (m, 1H, –N–
CH), 4.05–4.16 (m, 2H, –O–CH2), 3.41–3.45 (dd, J = 6.0, 13.8 Hz,
1H, –CH2–Ph), 3.08–3.12 (dd, J = 9.6, 13.2 Hz, 1H, –CH2–Ph); 13C
NMR (150 MHz, CDCl3) d 135.8, 135.0, 134.0, 129.2, 129.0 (2C),
128.2 (2C), 128.0 (2C), 127.3(2C), 89.3, 69.4, 60.7, 38.6.
4.2.6. Compound (E)-(2S,4S)-3f and (Z)-(2S,4S)-3f
Colorless crystals, mp 60 °C; ½a D20
¼ ꢁ40 (c 1.20, CHCl3); IR (KBr)
ꢀ
mmax 3442 (vs), 3051 (vs), 2944 (s), 1964 (s), 1528 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 298 (M+, 70), 267 (45), 238 (40), 136
(100), 117 (65), 91 (70); HR-MS-ESI m/z calcd for C17H18N2O3 + H
299.1388, found 299.1395, error ꢁ3.6 ppm. (E)-(2S,4S)-3f: 1H
NMR (300 MHz, CDCl3) d 7.46–8.34 (m, 9H, –Ph-o-OCH3, –Ph),
6.92 (s, 1H, –N–CH–O), 4.64–4.70 (m, 1H, –N–CH), 4.11–4.20 (m,
2H, –O–CH2), 3.72 (s, 3H, –O–CH3), 3.01–3.12 (m, 1H, –CH2–Ph),
2.63–2.71 (m, 1H, –CH2–Ph); 13C NMR (75 MHz, CDCl3) d 138.3,
132.4, 129.3, 129.0 (2C), 128.8, 128.5, 128.3, 128.0, 127.9 (2C),
123.0, 91.8, 69.9, 60.6, 55.8, 36.6. (Z)-(2S,4S)-3f: 1H NMR
(300 MHz, CDCl3) d 7.46–8.34 (m, 9H, –Ph-o-OCH3, –Ph), 6.54 (s,
1H, –N–CH–O), 5.13–5.18 (m, 1H, –N–CH), 4.11–4.25 (m, 2H, –O–
CH2), 3.68 (s, 3H, –O–CH3), 3.31–3.42 (m, 1H, –CH2–Ph), 3.03–
3.11 (m, 1H, –CH2–Ph); 13C NMR (75 MHz, CDCl3) d 138.1, 132.6,
129.1, 128.9 (2C), 128.4, 128.1, 128.0, 127.3, 126.9 (2C), 123.3,
90.4, 69.0, 60.6, 55.7, 39.6.
4.2.3. Compound (E)-(2S,4S)-3c and (Z)-(2S,4S)-3c
Colorless crystals, mp 62 °C; ½a D20
¼ ꢁ48 (c 1.00, CHCl3); IR (KBr)
ꢀ
mmax 3430 (vs), 3028 (vs), 2890 (s), 1930 (s), 1581 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 302 (M+, 20), 272 (65), 192 (66), 118
(100), 91 (80), 89 (40); HR-MS-ESI m/z calcd for C16H15N2O2Cl +
Na 325.0818, found 325.0826, error ꢁ2.2 ppm. (E)-(2S,4S)-3c: 1H
NMR (300 MHz, CDCl3) d 7.33–7.53 (m, 9H, –Ph-o-Cl, –Ph), 6.95
(s, 1H, –N–CH–O), 4.71–4.75 (m, 1H, –N–CH), 4.25–4.32 (m, 2H,
–O–CH2), 3.27–3.30 (dd, J = 3.2, 13.6 Hz, 1H, –CH2–Ph), 2.63–2.68
(dd, J = 9.2, 13.8 Hz, 1H, –CH2–Ph); 13C NMR (75 MHz, CDCl3) d
135.7, 135.2, 134.9, 129.1 (2C), 128.8, 128.5, 128.3, 127.8, 127.6
(2C), 127.0, 90.7, 68.2, 59.2, 36.4. (Z)-(2S,4S)-3c: 1H NMR
(300 MHz, CDCl3) d 7.33–7.53 (m, 9H, –Ph-o-Cl, –Ph), 6.54 (s, 1H,
–N–CH–O), 5.20–5.22 (m, 1H, –N–CH), 4.12–4.20 (m, 2H, –O–
CH2), 3.46–3.50 (dd, J = 5.8, 13.8 Hz, 1H, –CH2–Ph), 3.12–3.16 (dd,
J = 9.0, 13.0 Hz, 1H, –CH2–Ph); 13C NMR (75 MHz, CDCl3) d 138.2,
136.5, 135.1, 130.5 (2C), 129.8, 128.4, 128.1, 128.0, 127.5 (2C),
127.3, 88.7, 67.4, 60.2, 39.6.
4.2.7. Compound (E)-(2S,4S)-3g and (Z)-(2S,4S)-3g
Colorless crystals, mp 55 °C; ½a D20
ꢀ
¼ ꢁ38 (c 1.00, CHCl3); IR (KBr)
m
max 3438 (vs), 3032 (vs), 2925 (s), 1935(s), 1520(s,
m
sym NO) cmꢁ1
;
MS (EI, 70 eV) m/z 282 (M+, 40), 252 (55), 222 (60), 119 (100), 91
(70); HR-MS-ESI m/z calcd for C17H18N2O3 + H 283.1434, found
283.1446, error ꢁ4.2 ppm. (E)-(2S,4S)-3g: 1H NMR (300 MHz,
CDCl3) d 7.36–8.14 (m, 9H, –Ph-p-CH3, –Ph), 6.65 (s, 1H, –N–CH–
O), 4.54–4.60 (m, 1H, –N–CH), 4.05–4.16 (m, 2H, –O–CH2), 3.01–
3.12 (m, 1H, –CH2–Ph), 2.63–2.71 (m, 1H, –CH2–Ph), 2.36 (s, 3H,
–CH3); 13C NMR (75 MHz, CDCl3) d 138.3, 130.4, 129.3, 128.8

2082
L. Peng et al. / Tetrahedron: Asymmetry 19 (2008) 2078–2083
(2C), 128.3 (2C), 128.1 (2C), 127.2 (2C), 123.4, 91.5, 69.9, 60.5, 36.5,
21.3. (Z)-(2S,4S)-3g: 1H NMR (300 MHz, CDCl3) d 7.36–8.14 (m, 9H,
–Ph-p-CH3, –Ph), 6.33 (s, 1H, –N–CH–O), 5.12–5.14 (m, 1H, –N–
CH), 4.11–4.23 (m, 2H, –O–CH2), 3.30–3.45 (m, 1H, –CH2–Ph),
3.05–3.13 (m, 1H, –CH2–Ph), 2.32 (s, 3H, –CH3); 13C NMR
(75 MHz, CDCl3) d 137.4, 130.2, 129.1, 128.2 (2C), 128.0 (2C),
127.3 (2C), 126.4 (2C), 123.3, 90.2, 69.3, 60.6, 39.6, 29.5.
(70); HR-MS-ESI m/z calcd for C15H13N3O4 + Na 322.0795, found
322.0801, error ꢁ2.2 ppm. (E)-(2S,4S)-3k: 1H NMR (300 MHz,
CDCl3) d 7.24–8.31 (m, 9H, –Ph-p-NO2, –Ph), 6.86 (s, 1H, –N–CH–
O), 5.35–5.39 (q, J = 6.9 Hz, 1H, –N–CH), 4.66–4.71 (dd, J = 6.9,
9.0 Hz, 1H, –O–CH2), 4.12–4.17 (dd, J = 7.2, 9.3 Hz, 1H, –O–CH2);
13C NMR (75 MHz, CDCl3) d 141.5, 136.7, 129.2, 129.0, 128.7 (2C),
127.8 (2C), 126.1 (2C), 123.9 (2C), 91.0, 72.8, 59.4. (Z)-(2S,4S)-3k:
1H NMR (300 MHz, CDCl3) d 7.24–8.31 (m, 9H, –Ph-p-NO2, –Ph),
6.69 (s, 1H, –N–CH–O), 5.70–5.73 (q, J = 6.0 Hz, 1H, –N–CH),
4.57–4.62 (dd, J = 6.0, 9.3 Hz, 1H, –O–CH2), 4.24–4.29 (dd, J = 6.6,
9.0 Hz, 1H, –O–CH2); 13C NMR (75 MHz, CDCl3) d 141.8, 136.2,
129.4, 128.5, 128.2 (2C), 127.5 (2C), 127.1 (2C), 123.8 (2C), 89.5,
73.2, 63.0.
4.2.8. Compound (E)-(2S,4S)-3h and (Z)-(2S,4S)-3h
Colorless crystals, mp 53 °C; ½a D20
¼ ꢁ35 (c 0.40, CHCl3); IR (KBr)
ꢀ
mmax 3428 (vs), 3005 (vs), 2834 (s), 1924 (s), 1553 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 254 (M+, 20), 223 (15), 194 (65), 104
(100), 91 (60); HR-MS-ESI m/z calcd for
C15H14N2O2 + Na
277.0960, found 277.0950, error +3.6 ppm. (E)-(2S,4S)-3h: 1H
NMR (600 MHz, CDCl3) d 7.30–7.60 (m, 10H, –Ph), 6.77 (s, 1H,
–N–CH–O), 5.34–5.39 (q, J = 6.9 Hz, 1H, –N–CH), 4.61–4.69 (dd,
J = 7.5, 9.0 Hz, 1H, –O–CH2), 4.07–4.12 (dd, J = 6.6, 9.3 Hz, 1H,
–O–CH2); 13C NMR (150 MHz, CDCl3) d 138.5, 137.2, 135.6, 130.5,
128.4 (2C), 128.0 (2C), 127.9 (2C), 126.9 (2C), 91.0, 71.5, 61.3.
(Z)-(2S,4S)-3h: 1H NMR (600 MHz, CDCl3) d 7.30–7.60 (m, 10H,
–Ph), 6.70 (s, 1H, –N–CH–O), 5.68–5.72 (q, J = 6.0 Hz, 1H, –N–CH),
4.53–4.61 (dd, J = 6.9, 9.0 Hz, 1H, –O–CH2), 4.20–4.24 (dd, J = 6.6,
9.3 Hz, 1H, –O–CH2); 13C NMR (150 MHz, CDCl3) d 137.8, 137.0,
134.0, 131.0, 128.7 (2C), 128.5 (2C), 128.3 (2C), 127.6 (2C), 90.0,
72.7, 62.3.
4.2.12. Compound (E)-(2S,4S)-3l and (Z)-(2S,4S)-3l
Colorless crystals mp 50 °C; ½a D20
¼ ꢁ41 (c 1.10, CHCl3); IR (KBr)
ꢀ
mmax 3424 (vs), 3068 (vs), 2932 (s), 1955 (s), 1574 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 284 (M+, 60), 254 (20), 224 (40), 136
(100), 117 (75), 91 (50); HR-MS-ESI m/z calcd for C16H16N2O3 + H
285.1232, found 285.1237, error ꢁ2.2 ppm. (E)-(2S,4S)-3l: 1H
NMR (300 MHz, CDCl3) d 6.82–7.56 (m, 9H, –Ph-p-OCH3, –Ph),
6.69 (s, 1H, –N–CH–O), 5.30–5.35 (q, J = 6.3 Hz, 1H, –N–CH),
4.61–4.66 (dd, J = 6.9, 9.0 Hz, 1H, –O–CH2), 4.04–4.10 (dd, J = 6.6,
9.0 Hz, 1H, –O–CH2), 4.03 (s, 3H, –O–CH3); 13C NMR (75 MHz,
CDCl3) d 136.5, 135.2, 129.3, 128.6, 128.2 (2C), 128.0 (2C), 127.4
(2C), 123.2 (2C), 91.2, 71.8, 61.7, 55.2. (Z)-(2S,4S)-3l: 1H NMR
(300 MHz, CDCl3) d 6.82–7.56 (m, 9H, –Ph-p-OCH3, –Ph), 6.52 (s,
1H, –N–CH–O), 5.68–5.72 (q, J = 6.0 Hz, 1H, –N–CH), 4.53–4.57
(dd, J = 6.6, 9.0 Hz, 1H, –O–CH2), 4.17–4.21 (dd, J = 6.0, 9.0 Hz, 1H,
–O–CH2), 3.83 (s, 3H, –O–CH3); 13C NMR (75 MHz, CDCl3) d
136.2, 134.8, 129.7, 128.5, 128.1 (2C), 127.3 (2C), 126.1 (2C),
123.3 (2C), 90.2, 73.0, 62.7, 55.2.
4.2.9. Compound (E)-(2S,4S)-3i and (Z)-(2S,4S)-3i
Colorless crystals, mp 57 °C; ½a D20
¼ ꢁ37 (c 0.50, CHCl3); IR (KBr)
ꢀ
mmax 3402 (vs), 3041 (vs), 2880 (s), 1918 (s), 1564 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 288 (M+, 18), 257 (10), 228 (40), 165
(90), 104 (100); HR-MS-ESI m/z calcd for
C15H13N2O2Cl + Na
311.0550, found 311.0558, error ꢁ2.4 ppm. (E)-(2S,4S)-3i: 1H
NMR (300 MHz, CDCl3) d 7.22–7.51 (m, 9H, –Ph-p-Cl, –Ph), 6.73
(s, 1H, –N–CH–O), 5.32–5.37 (q, J = 6.6 Hz, 1H, –N–CH), 4.62–4.68
(dd, J = 7.5, 9.3 Hz, 1H, –O–CH2), 4.05–4.11 (dd, J = 6.6, 9.0 Hz, 1H,
–O–CH2); 13C NMR (75 MHz, CDCl3) d 137.2, 136.0, 133.7, 129.1,
128.9 (2C), 128.3 (2C), 128.1 (2C), 126.1 (2C), 91.8, 72.5, 59.3.
(Z)-(2S,4S)-3i: 1H NMR (300 MHz, CDCl3) d 7.22–7.51 (m, 9H,
–Ph-p-Cl, –Ph), 6.64 (s, 1H, –N–CH–O), 5.66–5.70 (q, J = 6.3 Hz,
1H, –N–CH), 4.53–4.58 (dd, J = 6.9, 9.3 Hz, 1H, –O–CH2), 4.19–
4.23 (dd, J = 6.0, 9.0 Hz, 1H, –O–CH2); 13C NMR (75 MHz, CDCl3) d
137.3, 135.2, 135.4, 129.8, 129.5 (2C), 129.0 (2C), 128.0 (2C),
127.3 (2C), 90.0, 72.7, 62.9.
4.2.13. Compound (E)-(2S,4S)-3m and (Z)-(2S,4S)-3m
Colorless crystals, mp 46 °C; ½a D20
¼ ꢁ39 (c 1.00, CHCl3); IR (KBr)
ꢀ
mmax 3447 (vs), 3065 (vs), 2938 (s), 1949 (s), 1570 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 284 (M+, 60), 254 (55), 224 (60), 136
(100), 117 (50), 91 (34); HR-MS-ESI m/z calcd for C16H16N2O3 + H
285.1238, found 285.1237, error +1.0 ppm. (E)-(2S,4S)-3m: 1H
NMR (300 MHz, CDCl3) d 6.90–7.65 (m, 9H, –Ph-o-OCH3, –Ph),
6.92 (s, 1H, –N–CH–O), 5.34–5.39 (q, J = 6.6 Hz, 1H, –N–CH),
4.64–4.69 (dd, J = 6.6, 9.0 Hz, 1H, –O–CH2), 4.09–4.15 (dd, J = 6.3,
9.3 Hz, 1H, –O–CH2), 4.23 (s, 3H, –O–CH3); 13C NMR (75 MHz,
CDCl3) d 136.2, 135.0, 129.8, 129.7, 129.1 (2C), 128.3, 128.1,
128.0, 127.3 (2C), 123.2, 91.2, 71.6, 61.5, 55.4. (Z)-(2S,4S)-3m: 1H
NMR (300 MHz, CDCl3) d 6.82–7.56 (m, 9H, –Ph-o-OCH3, –Ph),
6.82 (s, 1H, –N–CH–O), 5.68–5.72 (q, J = 6.0 Hz, 1H, –N–CH),
4.53–4.57 (dd, J = 6.6, 9.0 Hz, 1H, –O–CH2), 4.17–4.21 (dd, J = 6.0,
9.0 Hz, 1H, –O–CH2), 3.83 (s, 3H, –O–CH3); 13C NMR (75 MHz,
CDCl3) d 136.0, 134.5, 129.3, 129.0, 128.7 (2C), 128.5, 128.2,
127.5, 125.8 (2C), 123.3, 90.1, 72.8, 62.7, 55.2.
4.2.10. Compound (E)-(2S,4S)-3j and (Z)-(2S,4S)-3j
Colorless crystals, mp 55 °C; ½a D20
¼ ꢁ32 (c 0.70, CHCl3); IR (KBr)
ꢀ
mmax 3434 (vs), 3058 (vs), 2885 (s), 1925 (s), 1547 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 288 (M+, 23), 258 (40), 228 (55), 165
(70), 104 (100); HR-MS-ESI m/z calcd for
C15H13N2O2Cl + Na
311.0562, found 311.0558, error +1.2 ppm. (E)-(2S,4S)-3j: 1H
NMR (300 MHz, CDCl3) d 7.33–7.64 (m, 9H, –Ph-o-Cl, –Ph), 6.95
(s, 1H, –N–CH–O), 5.42–5.47 (q, J = 7.5 Hz, 1H, –N–CH), 4.68–4.72
(dd, J = 7.5, 9.3 Hz, 1H, –O–CH2), 4.09–4.15 (dd, J = 7.2, 9.6 Hz, 1H,
–O–CH2); 13C NMR (75 MHz, CDCl3) d 137.5, 136.4, 133.2, 129.8
(2C), 129.3, 129.3, 128.5, 128.1, 128.0, 126.5 (2C), 91.3, 72.2,
59.2. (Z)-(2S,4S)-3j: 1H NMR (300 MHz, CDCl3) d 7.22–7.51 (m,
9H, –Ph-o-Cl, –Ph), 6.81 (s, 1H, –N–CH–O), 5.77–5.82 (q,
J = 6.0 Hz, 1H, –N–CH), 4.60–4.64 (dd, J = 6.3, 9.0 Hz, 1H, –O–
CH2), 4.21–4.25 (dd, J = 6.9, 9.0 Hz, 1H, –O–CH2); 13C NMR
(75 MHz, CDCl3) d 137.8, 136.2, 135.8, 130.1 (2C), 129.7, 129.4,
129.2, 129.0, 128.5, 127.2 (2C), 89.7, 72.4, 62.5.
4.2.14. Compound (E)-(2S,4S)-3n and (Z)-(2S,4S)-3n
Colorless crystals, mp 43 °C; ½a D20
¼ ꢁ32 (c 0.90, CHCl3); IR (KBr)
ꢀ
mmax 3447 (vs), 3065 (vs), 2938 (s), 1949 (s), 1570 (s, msym NO)
cmꢁ1; MS (EI, 70 eV) m/z 268 (M+, 30), 238 (65), 208 (44), 119
(100), 91 (80); HR-MS-ESI m/z calcd for
C16H16N2O2 + H
269.1286, found 269.1288, error ꢁ1.5 ppm. (E)-(2S,4S)-3n: 1H
NMR (300 MHz, CDCl3) d 6.78–7.52 (m, 9H, –Ph-p-CH3, –Ph), 6.64
(s, 1H, –N–CH–O), 5.31–5.36 (q, J = 6.3 Hz, 1H, –N–CH), 4.62–4.67
(dd, J = 6.3, 9.3 Hz, 1H, –O–CH2), 4.08–4.14 (dd, J = 6.0, 9.3 Hz, 1H,
–O–CH2), 2.43 (s, 3H, –CH3); 13C NMR (75 MHz, CDCl3) d 136.4,
135.3, 129.3, 128.6, 128.4 (2C), 128.0 (2C), 127.3 (2C), 123.0 (2C),
91.4, 71.3, 61.3, 21.3. (Z)-(2S,4S)-3n: 1H NMR (300 MHz, CDCl3) d
6.78–7.52 (m, 9H, –Ph-p-CH3, –Ph), 6.59 (s, 1H, –N–CH–O), 5.64–
5.68 (q, J = 6.3 Hz, 1H, –N–CH), 4.52–4.56 (dd, J = 6.3, 9.3 Hz, 1H,
4.2.11. Compound (E)-(2S,4S)-3k and (Z)-(2S,4S)-3k
Colorless crystals, mp 55 °C; ½a D20
ꢀ
¼ ꢁ39 (c 1.20, CHCl3); IR (KBr)
m
max 3480 (vs), 3014 (vs), 2836 (s), 1931 (s), 1526(s,
m
sym NO) cmꢁ1
;
MS (EI, 70 eV) m/z 299 (M+, 40), 268 (56), 239 (70), 150 (100), 91

L. Peng et al. / Tetrahedron: Asymmetry 19 (2008) 2078–2083
2083
–O–CH2), 4.18–4.22 (dd, J = 6.3, 9.0 Hz, 1H, –O–CH2), 2.38 (s, 3H,
–CH3); 13C NMR (75 MHz, CDCl3) d 136.2, 134.3, 129.5, 128.3,
128.1 (2C), 127.2 (2C), 125.4 (2C), 123.3 (2C), 90.2, 72.4, 62.3, 29.2.
(2S,4S)-3d is shown in Figure 3. The crystallographic data have been
deposited at the Cambridge Crystallographic Data Center as supple-
mentary publication No. CCDC 632025.
4.2.15. Crystal data for (2S,4S)-3b
4.2.18. Crystal data for (2R,4S)-3i
C
16H15N2O2Cl, Mr = 302.75, space group P21 with cell parame-
C
15H13N2O2Cl, Mr = 288.72, space group P212121 with cell
parameters: a = 7.5655(2) Å, b = 12.6030(3) Å, c = 14.4639(3) Å,
90.00°, b = 90.00°, calcd = 1.391 mg/
= 90.00°, V = 1379.10(6) Å3,
m3, Z = 4, T = 294(2) K, = 0.279 cmꢁ1
F000 = 600, ꢁ9 6 h 6 6,
ters: a = 6.5605(3) Å, b = 0034(4) Å, c = 16.4669(9) Å, = 90.00°,
b = 100.873(2)°,
Z = 2, T = 294(2) K,
8, ꢁ16 6 l 6 19, 5.04° 6 2h 6 50.98°, 2718 data collected, 2181 un-
ique data (Rint = 0.0186), 128 refined parameters. GOF(F2) = 1.025,
R1 = 0.0406, wR2 = 0.0792. The X-ray crystallographic structure of
(2S,4S)-3b is shown in Figure 1. The crystallographic data have
been deposited at the Cambridge Crystallographic Data Center as
supplementary publication No. CCDC 630583.
a
a =
c
= 90.00°, V = 743.00(7) Å3,
l
q
calcd = 1.353 mg/m3,
c
q
=0.263 cmꢁ1, F000 = 316, ꢁ7 6 h 6 7, ꢁ8 6 k 6
l
,
ꢁ16 6 k 6 16, ꢁ16 6 l 6 18, 4.28° 6 2h 6 54.52°, 3084 data col-
lected, 2294 unique data (Rint = 0.0270), 128 refined parameters.
GOF(F2) = 1.046, R1 = 0.0401, wR2 = 0.0699. The X-ray crystallo-
graphic structure of (2R,4S)-3i is shown in Figure 4. The crystallo-
graphic data have been deposited at the Cambridge
Crystallographic Data Center as supplementary publication No.
CCDC 630584.
4.2.16. Crystal data for (2R,4S)-3b
C
16H15N2O2Cl, Mr = 302.75, space group P212121 with cell
parameters: a = 5.7523(14) Å, b = 9.054(2) Å, c = 28.648(7) Å,
90.00°, b = 90.00°, calcd = 1.348 mg/
= 90.00°, V = 1492.1(6) Å3,
m3, Z = 4, T = 294(2) K, = 0.262 cmꢁ1
F000 = 632, ꢁ6 6 h 6 6,
Acknowledgment
a
=
c
q
Project No. 20572040 was supported by National Natural Sci-
ence Foundation of China.
l
,
ꢁ8 6 k 6 10, ꢁ34 6 l 6 34, 4.72° 6 2h 6 50.98°, 2750 data col-
lected, 1531 unique data (Rint = 0.0543), 128 refined parameters.
GOF(F2) = 1.038, R1 = 0.0446, wR2 = 0.0741. The X-ray crystallo-
graphic structure of (2R,4S)-3b is shown in Figure 2. The crystallo-
graphic data have been deposited at the Cambridge
Crystallographic Data Center as supplementary publication No.
CCDC 632602.
References
1. (a) White, E. H.; Darbeau, R. W.; Chen, Y.; Chen, D.; Chen, S. J. Org. Chem. 1996,
61, 7986; (b) Darbeau, R. W.; Gibble, R. E.; Pease, R. S.; Siso, L. M.; Heurtin, D. J. J.
Chem. Soc., Perkin Trans. 2 2001, 1084.
2. Darbeau, R. W.; Pease, R. S.; Perez, E. V. J. Org. Chem. 2002, 67, 2942.
3. Wang, P. G.; Xian, M.; Tang, X.; Wu, X.; Wen, Z.; Cai, T.; Janczuk, A. J. Chem. Rev.
2002, 102, 1091.
4. Grigory, V. Z.; Dmitry, M. R. Org. Lett. 2003, 5, 1253.
5. Peng, L. J.; Liu, Z. Q.; Wang, J. T.; Wu, L. M. Tetrahedron Lett. 2007, 48,
7418.
6. Vasella, A.; Voeffray, R. Helv. Chim. Acta 1982, 65, 1134.
7. Zolfigol, M. A.; Shirini, F.; Choghamarani, A. G.; Taqian-Nasab, A.; Keypour, H.;
Salehzadeh, S. J. Chem. Res. (S) 2000, 420.
4.2.17. Crystal data for (2S,4S)-3d
C16H15N3O4, Mr = 313.31, space group P21 with cell parameters:
a = 6.7170(3) Å, b = 13.5145(7) Å, c = 8.2169(4) Å, = 90.00°, b =
a
96.578(2)°,
T = 294(2) K,
c q
= 90.00°, V = 740.99(6) Å3, calcd = 1.404 mg/m3, Z = 2,
l
= 0.103 cmꢁ1, F000 = 328, ꢁ7 6 h 6 8, ꢁ16 6 k 6 13,
8. (a) Zhu, X. Q.; Xian, M.; Wang, K.; Cheng, J. P. J. Org. Chem. 1999, 64, 4187; (b)
Cheng, J. P.; Wang, K. Tetrahedron Lett. 1998, 39, 7925.
9. Armarego, W. L. F.; Perrin, D. D. Purification of Laboratory Chemicals;
Butterworth-Heinemann: Oxford, 1997.
ꢁ9 6 l 6 9, 5.00° 6 2h 6 50.98°, 2071 data collected, 1617 unique
data (Rint = 0.0309), 128 refined parameters. GOF(F2) = 1.040,
R1 = 0.0420, wR2 = 0.0855. The X-ray crystallographic structure of