, 2004, 14(6), 310–312
C(14)
20
15
C(13)
N(1)
C(6)
C(5)
O(1)
10
5
C(4)
O(5)
C(9)
(+)-3
(–)-3
C(10)
C(3)
C(2)
C(7)
O(3)
O(2)
C(8)
0
C(11)
250
300
350
O(4)
C(12)
–5
–10
l/nm
Figure 3 The general view of 2.
with the torsion angles C(14)C(10)C(11)C(12) and N(1)C(10)-
C(11)C(12) equal to 12.4° and 160.3°, respectively. Thus, the
presence of the methyl groups at C(3) and C(4) atoms leads to
significant weakening of the N–C=C conjugation. The six-
membered ring is characterised by a twist conformation. The
mutual disposition of the ester groups in 4 is different with the
torsion angles C(10)C(11)C(12)O(2) and O(4)C(14)C(10)C(11)
equal to 7.9 and 117.2°, respectively, which probably lead to a
shortening of the C(11)–C(12) bond [1.4654(9)Å] in comparison
with the C(10)–C(14) one [1.5168(9) Å].
–15
–20
Figure 2 CD spectra of (+)-3 and (–)-3; the solvent is 20% (v/v) propan-
2-ol in hexane.
ture of 4 was unambiguously confirmed by XRD data (Figure 5).
The 1H NMR spectrum of 4 remained unchanged even at –70 °C
(in CD2Cl2), i.e., the rotation around the N–substituent bond is
not restricted sterically. The XRD revealed that ester groups are
in the cis configuration (Figure 5). In spite of possible conjuga-
tion between the nitrogen electron lone pair and the C(10)–C(11)
double bond the dihedral angle between the N(1)C(3)C(4)C(10)
and C(12)C(11)C(10)C(14) planes is equal to 27.6°. At the
same time, the nitrogen atom N(1) is slightly pyramidal [the
deviation of N(1) from the C(3), C(4) C(10) plane is equal to
0.0804(7) Å]. Note that the C(10)–C(11) double bond is twisted
H(9A)
C(9)
H(9A')
H(1N) O(1A)
N(1)
O(2A)
‡
At 120 K, the crystals of 2·0.5C6H6 (C16H22NO5) are monoclinic,
space group C2/c, a = 16.784(2), b = 16.711(2) and c = 13.025(1) Å, b =
= 114.784(2)°, V = 3316.9(6) Å3, Z = 8, M = 308.35, dcalc = 1.235 g cm–3,
m(MoKα) = 0.92 cm–1, F(000) = 1320.
At 120 K, the crystals of 4 (C15H23NO5) are triclinic, space group P1,
a = 6.7421(9), b = 8.1017(12), c = 14.881(2) Å, a = 90.746(7)°, b =
= 94.234(7)°, g = 110.268(6)°, V = 759.77(18) Å3, Z = 2, M = 297.34,
dcalc = 1.300 g cm–3, m(MoKα) = 0.97 cm–1, F(000) = 320.
Figure 4 Fragment of the crystal structure of 2·0.5C6H6 illustrating the
formation of bifurcated N–H···O bonds [N(1)–H(1N)···O(1) (x, –y, z + 1/2):
N(1)···O(1) 2.807(3) Å, H(1N)···O(1) 2.03 Å, N(1)–H(1N)O(1) 146°;
N(1)–H(1N)···O(2) (x, –y, z + 1/2): N(1)···O(2) 2.936(3) Å, H(1N)···O(1)
2.28 Å, N(1)–H(1N)O(1) 132°] and C–H···π contacts [C(9)H(9A)···XBz
(centroid of benzene): C(9)···XBz 3.707(3) Å, H(9A)···XBz 2.83 Å, C(9)–
H(9A)XBz 139°].
Intensities of 11022 (2·0.5C6H6) and 20677 (4) reflections were
measured with a Smart 1000 CCD diffractometer at 120 K [l(MoKα) =
= 0.71072 Å, 2q < 60° (2·0.5C6H6) 90° (4)] and 4799 (2·0.5C6H6) and
9891 (4) independent reflections [Rint = 0.0151 (2·0.5C6H6), 0.0190 (4)]
were used in the further refinement. The structures were solved by a
direct method and refined by the full-matrix least-squares technique
against F2 in the anisotropic-isotropic approximation. The analysis of
the Fourier synthesis have revealed that the benzene molecule and one
of Et groups in (2·0.5C6H6) are disordered by two positions. The hydro-
gen atoms for an ordered part were located from the Fourier density
synthesis. The positions of the remaining hydrogen atoms were calcu-
lated from a geometrical point of view. The refinement converged to
wR2 = 0.1072 and GOF = 1.042 for all independent reflections [R1 =
= 0.0434 was calculated against F for 3716 observed reflections with
I > 2s(I)] for 2·0.5C6H6; to wR2 = 0.0978 and GOF = 0.992 for all
independent reflections [R1 = 0.0492 was calculated against F for 7098
observed reflections with I > 2s(I)] for 4. All calculations were per-
formed using SHELXTL PLUS 5.0.
This work was supported by the Russian Academy of Sciences
and the Russian Foundation for Basic Research (grant nos. 03-03-
32019 and DFG-RFBR 03-03-04010).
O(4)
C(7)
C(15)
C(14)
C(8)
O(2)
C(5)
C(2)
C(3)
C(4)
O(5)
O(1)
N(1)
C(6)
C(12)
C(10)
C(1)
C(13)
C(11)
O(3)
C(9)
Figure 5 The general view of 4. Selected bond lengths (Å): O(1)–C(1)
1.2198(9), O(2)–C(12) 1.2173(8), O(3)–C(12) 1.3525(9), O(3)–C(13)
1.4415(9), O(4)–C(14) 1.2053(9), O(5)–C(14) 1.3388(9), O(5)–C(15)
1.4485(9), N(1)–C(10) 1.3790(8), N(1)–C(4) 1.5049(9), N(1)–C(3)
1.5121(9), C(10)–C(11) 1.3618(9), C(10)–C(14) 1.5168(9), C(11)–C(12)
1.4654(9); selected bond angles (°): C(10)–N(1)–C(4) 118.72(5), C(10)–
N(1)–C(3) 121.24(5), C(4)–N(1)–C(3) 119.15(5), O(1)–C(1)–C(5) 122.81(8),
O(1)–C(1)–C(2) 122.77(8), C(5)–C(1)–C(2) 114.41(6), C(11)–C(10)–N(1)
125.14(6), C(11)–C(10)–C(14) 116.31(6), N(1)–C(10)–C(14) 118.16(6),
C(10)–C(11)–C(12) 123.98(6).
Atomic coordinates, bond lengths, bond angles and thermal param-
eters have been deposited at the Cambridge Crystallographic Data Centre
conts/retrieving.html (or from the CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336 033; or deposit@ccdc.cam.ac.uk).
Any request to the CCDC for data should quote the full literature citation
and CCDC reference numbers 257661 and 257662. For details, see ‘Notice
to Authors’, Mendeleev Commun., Issue 1, 2004.
References
§
Chromatographic separation was performed using a Laboratory
1 E. L. Eliel, S. H. Wilen and L. N. Mander, Stereochemistry of Organic
Compounds, Wiley, New York, 1994, p. 1142.
pristroje Praha chromatograph with an injector with a 20-µl sample loop.
Conditions: Chiralpak AD stationary phase (250×4.6 mm i.d.) available
from Diacel Chemical Industries (Japan); mobile phase, 20% (v/v)
propan-2-ol in hexane; flow rate of 2 ml min–1; temperature, ambient;
detection UV 254 nm.
A solution of 3 mg of compound 3 in 50 µl of propan-2-ol was
injected into the chromatograph in four portions.
Retention times of enantiomers are t1 = 6.042 min and t2 = 6.667 min;
the void time is t0 = 1.56 min, as determined by the injection of tri-tert-
butylbenzene. Separation factor a = (t2 – t0)/(t1 – t0) = 1.39.
2 M. Oki, in Topics in Stereochemistry, eds. N. L. Allinger, E. L. Eliel and
S. H. Wilen, Scientific Publishers, New York, 1983, vol. 14.
3 X. Mei and Ch. Wolf, Chem. Commun., 2004, 2078.
4 J. Claiden, A. Lund, L. Vallvezdú and M. Helliwell, Nature, 2004, 431,
966.
5 F. Andreoli, N. Vanthuyne and C. Roussel, Final Program of 16th
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Mendeleev Commun. 2004 311