cis-(6RS,13RS)-3,3,10,10-Tetramethyl-6,13-diphenyl-1,8-dioxa-4, 11-diazacyclotetradecane-2,5,9,12-tetraone and two of its precursors

Article abstract of DOI:10.1107/S010827010601420X

The title macrocycle, C₂₆H₃₀N₂O ₆, (VI), was obtained by 'direct amide cyclization' from the linear precursor 3-hydroxy-N-[1-methyl-1-(N-methyl-N-phenylcarbamoyl)ethyl]-2- phenylpropanamide, the N-methylanilide

Full text of DOI:10.1107/S010827010601420X

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
oligoamides with HCl gas in toluene at 373 K yields nine- to
24-membered cyclic depsipeptides in good yields via the
formation of 1,3-oxazol-5(4H)-ones as intermediates (Obrecht
È
& Heimgartner, 1987; Koch et al., 2000, 2001; Kottgen et al.,
2006).
ISSN 0108-2701
cis-(6RS,13RS)-3,3,10,10-Tetramethyl-
6,13-diphenyl-1,8-dioxa-4,11-diaza-
cyclotetradecane-2,5,9,12-tetraone
and two of its precursors
Anthony Linden,* Boyan Iliev and Heinz Heimgartner
Institute of Organic Chemistry, University of Zurich, Winterthurerstrasse 190,
È
Our recent studies have shown that, when ꢁ-hydroxy acid
amides analogous to compound (III) are used, 14-membered
cyclodepsipeptides were formed instead of the expected
seven-membered monomers. Again, the corresponding 1,3-
oxazol-5(4H)-ones were shown to be intermediates (Iliev et al.,
2003, 2006). Furthermore, in comparable experiments with
racemic starting materials, the cyclodimers obtained were
trans-con®gured and no cis isomers could be detected. Other
cyclization methods that started from hydroxy acids [e.g.
(IV)], which were derived from ꢀ,ꢀ-disubstituted analogues of
compound (III), gave the same result (Iliev et al., 2003, 2006).
Further studies showed that, in order for the reactions to have
a practical value, it is a requirement that the ꢁ-hydroxy acid is
ꢀ,ꢀ-disubstituted. When that was not the case, water elim-
ination occurred and no cyclic products could be isolated,
although the intermediate oxazolone, like compound (V),
could be detected by means of IR spectroscopy and its
presence proven chemically (Iliev et al., 2006). Only in a single
case, when the starting ꢁ-hydroxy acid amide, (III), contained
the ꢀ-phenyl-ꢁ-hydroxy acid moiety, could crystals of a 14-
membered cyclodepsipeptide be isolated, namely the title
compound, (VI). The hydroxy acid, (IV), was obtained after
selective hydrolysis of (III) by treatment with 3 N HCl in
tetrahydrofuran. The intermediate oxazolone, (V), could be
isolated after treatment of (IV) with N,N0-dicyclohexyl-
carbodiimide in ethyl acetate. As part of the full character-
ization of the reaction products shown in the scheme and in
order to con®rm the stereochemistry of compound (VI), the
crystal structures of compounds (IV), (V) and (VI) were
determined and are described here.
CH-8057 Zurich, Switzerland
È
Correspondence e-mail: alinden@oci.unizh.ch
Received 13 April 2006
Accepted 19 April 2006
Online 24 May 2006
The title macrocycle, C26H30N2O6, (VI), was obtained by
`direct amide cyclization' from the linear precursor 3-hydroxy-
N-[1-methyl-1-(N-methyl-N-phenylcarbamoyl)ethyl]-2-phenyl-
propanamide, the N-methylanilide of rac-2-methyl-2-[(3-
hydroxy-2-phenylpropanoyl)amino]propanoic acid, C13H17-
NO4, (IV). The reaction proceeds via the intermediate rac-2-
(2-hydroxy-1-phenylethyl)-4,4-dimethyl-1,3-oxazol-5(4H)-one,
C13H15NO3, (V), which was synthesized independently and
whose structure was also established. Unlike all previously
described analogues, the title macrocycle has the cis-diphenyl
con®guration. The 14-membered ring has a distorted rect-
angular diamond-based [3434] con®guration and inter-
molecular NÐHÁ Á ÁO hydrogen bonds link the molecules
into a three-dimensional framework. The propanoic acid
precursor forms a complex series of intermolecular hydrogen
bonds, each of which involves pairwise association of
molecules and which together result in the formation of
extended two-dimensional sheets. The oxazole intermediate
forms centrosymmetric hydrogen-bonded dimers in the solid
state.
Comment
Cyclic depsipeptides are renowned for their biological activity,
mainly as antibiotics, due to their ability to allow cations
selectively to pass through the cell membrane (Ballard et al.,
2002). A useful method for the synthesis of some analogues,
which contain ꢀ,ꢀ-disubstituted ꢀ-amino acids, from linear
precursors is the so-called `direct amide cyclization' (Obrecht
& Heimgartner, 1984, 1987). The starting materials for the
cyclization are hydroxy oligoamides, such as compound (III)
(see scheme), which possess one or several ꢀ,ꢀ-disubstituted
ꢀ-amino acids and which are conveniently accessible from the
corresponding hydroxy acids [e.g. (I)] and 2H-azirin-3-amines
[e.g. (II)] via the `azirine/oxazolone method' (Wipf & Heim-
gartner, 1990; Heimgartner, 1991). Treatment of the hydroxy
Compound (IV) crystallizes in a centrosymmetric space
group and is therefore a racemate: the selected reference
molecule has the R con®guration at C5 (Fig. 1). The geometric
parameters involving the non-H atoms are within normal
ranges. The molecule possesses three hydrogen-bond donors,
which are all involved in intermolecular interactions (Table 1).
These interactions combine to link the molecules into
extended two-dimensional sheets which lie parallel to the
(001) plane (Fig. 2). Within the sheets, several hydrogen-
bonding motifs (Bernstein et al., 1995) can be discerned. The
carboxylic acid H atom interacts with the carbonyl O atom of
the carboxylic acid group of a neighbouring molecule, which,
Acta Cryst. (2006). C62, o339±o343
DOI: 10.1107/S010827010601420X
# 2006 International Union of Crystallography o339

organic compounds
in turn, acts as a donor for an identical interaction back to the
original molecule. These interactions result in pairs of mol-
ecules being linked into dimers across crystallographic centres
of inversion. This pattern can be described by a graph-set
motif of R22(8), which is one of the classic motifs found in the
crystal structures of carboxylic acids. The H atom of the
hydroxy group forms an intermolecular hydrogen bond with
the amide O atom of a different neighbouring molecule.
Again, this interaction links pairs of molecules into centro-
symmetric dimers and the pattern can be described by a graph-
set motif of R22(12). In a similar fashion, the amide H atom
forms an intermolecular hydrogen bond with the hydroxy O
atom of a third neighbouring molecule. This interaction also
links pairs of molecules into centrosymmetric dimers with the
R22(12) motif. The interactions involving the H atoms of
the hydroxy and amide groups can also be combined in an
alternating fashion to yield extended co-operative
Á Á ÁOÐHÁ Á ÁO CÐNÐHÁ Á ÁOÐHÁ Á Á chains, which run
parallel to the [100] direction and can be described by a binary
graph-set motif of C22(6).
Free re®nement of the carboxylic acid H atom in (IV)
resulted in a rather long O2ÐH2 distance, while the asso-
ciated hydrogen-bonding HÁ Á ÁO and OÁ Á ÁO distances in the
R22(8) motif between the opposing carboxylic acid functions in
two adjacent molecules are quite short (Table 2). This indi-
cates that the pairwise intermolecular hydrogen-bonding
interactions are quite strong. In such cases, some practitioners
have described observations that suggest there may be a
tendency for the hydrogen bonds to become more symme-
trical, disordered across the OÁ Á ÁO vector, or even perfectly
symmetrical (Gilli et al., 1994; Alfonso et al., 2001). The re®ned
position of atom H2, at ®rst glance, seems to support the idea
of partial symmetricalization of the H-atom position, but other
evidence suggests that the re®ned position may be misleading.
Firstly, the re®ned isotropic atomic displacement parameter of
atom H2 is somewhat larger than normal and larger than those
of the hydroxy and amide H atoms, whose positions and
atomic displacement parameters were also re®ned. Secondly, a
contoured difference Fourier map produced by PLATON
(Spek, 2003), in which the site-occupation factor of atom H2
had been set to 0.001, clearly shows that the electron density
does indeed extend a low ridge towards the acceptor O atom,
but that the maximum of the electron density is quite clearly
de®ned and is located closer to atom O2 than the re®ned
position of atom H2 (Fig. 3). The maximum is estimated to be
Figure 1
A view of the R enantiomer in racemic (IV), showing the atom-labelling
scheme. Displacement ellipsoids are drawn at the 50% probability level
and H atoms are represented by circles of arbitrary size.
Figure 3
Figure 2
A contoured difference Fourier map slice in the plane of the carboxylic
acid group of (IV), with the site-occupancy factor of atom H2 set to 0.001.
The re®ned positions of the atoms are shown by + marks. The contour
A hydrogen-bonded sheet in (IV). The hydrogen bonds are shown by
dashed lines and the R22(8), two R22(12) and C22(6) motifs are clearly
visible.
intervals are 0.1 e A 3. [Symmetry code: (i) x + 1, y + 2, z.]
Ê
ꢀ
o340 Linden et al. C13H17NO4, C13H15NO3 and C26H30N2O6
Acta Cryst. (2006). C62, o339±o343

organic compounds
about 6ꢁ being observed within the lactam groups. The corners
of an ideal [3434] rectangle are characterized by two conse-
cutive torsion angles of the same sign and values of Æ60ꢁ, and
it is here that the ring in (VI) shows the greatest deviation
from ideality. The dimethyl-substituted corners have a sharper
turn, as demonstrated by both torsion angles being up to 17ꢁ
less than 60ꢁ. The phenyl-substituted corners are completely
outside the expected pattern, with one torsion angle having a
magnitude of about 127ꢁ and the following torsion angle being
opposite in sign and with a magnitude of about 64ꢁ. The ®ve-
atom and four-atom planes formed by the lactone and lactam
sides of the rectangle, respectively, are reasonably planar, with
the maximum deviations in each type of plane being 0.023 (2)
Ê
about 0.83 A from atom O2, which is surprisingly close to the
Ê
normally expected OÐH distance of 0.84 A at the tempera-
ture of the measurement (160 K). This result suggests that the
re®ned position of atom H2 does not necessarily truly repre-
sent the majority of the electron-density distribution in this
case and that there may be little, if any, symmetricalization of
the hydrogen bond. The result further shows the importance
of examining contoured difference Fourier maps whenever
potentially unusual H-atom positions are being investigated.
Compound (V) also crystallized as a racemate and again the
reference molecule was selected as having the R con®guration
(Fig. 4). The oxazole ring is planar, with this plane making an
angle of 87.02 (6)ꢁ with the plane of the phenyl ring. The
hydroxy H atom forms an intermolecular hydrogen bond with
the N atom of the oxazole ring of a neighbouring molecule
which, in turn, acts as a donor for an identical interaction back
to the original molecule (Table 2). These interactions link
centrosymmetrically related pairs of molecules into dimers
and can be described by a graph-set motif of R22(12).
Compound (VI) crystallized as a racemate, albeit in a non-
centrosymmetric space group. The compound has the
6RS,13RS con®guration, which means that the phenyl substi-
tuents have a cis relationship: the selected reference molecule
has a 6R,13R con®guration (Fig. 5). The cis orientation of the
phenyl groups was unexpected, as all previous analogous
reactions starting from racemic materials had yielded trans-
con®gured cyclodimers (Iliev et al., 2003, 2006). The 14-
membered ring conformation, while corrugated, is not folded.
When viewed perpendicular to the mean ring plane, the ring
appears to have a distorted variant of the rectangular
diamond-lattice [3434] conformation often observed for this
size of organic macrocycle (Groth, 1979; Chan et al., 1985) and
predicted to be slightly more stable than the [3344] and [3335]
conformations (Dale, 1973). The lactone and lactam groups sit
along the `3' and `4' sides of the rectangle, respectively, while
the phenyl and methyl substituents occur at the corners. The
torsion angles along the sides of the rectangle (Table 3) are
close to the ideal value of 180ꢁ, with the greatest deviation of
Ê
and 0.042 (3) A, respectively. The greater deviation from
planarity of the sides containing the lactam groups is in
keeping with the greater deviation of the lactam torsion angle
from 180ꢁ. Most signi®cantly, instead of the planes of opposing
¯anks being parallel, as in the ideal diamond-based confor-
mation, the planes of the two lactam sides intersect at an angle
of 24.4 (4)ꢁ, while those of the two lactone sides intersect at an
angle of 80.6 (4)ꢁ, which means that the lactone carbonyl
groups are turned well away from one another. The described
distortions may all be a consequence of twists in the macro-
cyclic ring conformation, induced by the cis-positioned phenyl
substituents preferring to occupy equatorial positions. The
phenyl ring planes are approximately perpendicular to the
mean plane of the macrocyclic ring. One of the phenyl rings is
disordered with an approximately 2:1 ratio of orientations, and
the two orientations differ by a twist of 22.0 (1)ꢁ about the
C17Á Á ÁC20 axis.
The lactam groups in the molecules of (VI) are oriented
such that their donor H atoms point towards the same side of
the macrocyclic ring and, in addition, the molecules pack such
that all of the NÐH bonds in the structure face in roughly the
same direction. The crystallographic c-glide plane does not ¯ip
any molecules up the other way, as it lies approximately
perpendicular to the mean plane of the macrocyclic ring. In
the structures of the previously examined analogues (Iliev et
Figure 5
Figure 4
A view of the 6R,13R enantiomer in racemic (VI), showing the atom-
labelling scheme. Displacement ellipsoids are drawn at the 50%
probability level and H atoms are represented by circles of arbitrary
size. Only the major conformation of the disordered phenyl ring is shown.
A view of the R enantiomer in racemic (V), showing the atom-labelling
scheme. Displacement ellipsoids are drawn at the 50% probability level
and H atoms are represented by circles of arbitrary size.
ꢀ
Acta Cryst. (2006). C62, o339±o343
Linden et al.
C13H17NO4, C13H15NO3 and C26H30N2O6 o341

organic compounds
amounts by treatment of (III) (170 mg, 0.5 mmol) in toluene (100 ml)
at 373 K with HCl (gas) for 8 min, followed by chromatographic
puri®cation (silica gel, dichloromethane±acetone 20:1).
Compound (IV)
Crystal data
3
Ê
C13H17NO4
Mr = 251.28
Triclinic, P1
a = 6.6567 (2) A
Ê
b = 9.1317 (3) A
V = 631.98 (3) A
Z = 2
3
Dx = 1.320 Mg m
Mo Kꢀ radiation
Ê
1
Figure 6
The crystal packing in (VI), showing the intermolecular hydrogen bonds
as dashed lines.
ꢃ = 0.10 mm
T = 160 (1) K
Ê
c = 10.8486 (3) A
ꢀ = 99.2298 (16)ꢁ
ꢁ = 98.278 (2)ꢁ
Tablet, colourless
0.25 Â 0.17 Â 0.10 mm
ꢂ = 99.5405 (19)ꢁ
al., 2003, 2006), the centrosymmetric nature of the molecules
meant that the amide H atoms pointed to opposite sides of the
macrocyclic ring. This difference has consequences for the
hydrogen-bonding pattern. In the previous structures,
hydrogen bonds formed between the lactam NÐH groups and
the lactone O atoms of neighbouring molecules and assembled
the centrosymmetric molecules into stacks of ladder-like
columns, where the macrocycle acted as the ladder rung and
the hydrogen bonds were the rung supports, with the direc-
tional sense of the support (the NÐH ! O direction) on
opposing sides of a rung being opposite. In (VI), the lactam
NÐH groups also form intermolecular hydrogen bonds with
the lactone O atoms of neighbouring molecules (Table 4), but
instead of a ladder-like arrangement, the hydrogen bonds link
to diagonally offset neighbouring molecules, with each of the
two symmetry-independent interactions going off in different
directions (Fig. 6). Taken individually, the interactions link the
molecules into extended chains, each of which has a graph-set
motif of C(5). The chains involving N4ÐH and N11ÐH run in
the [101] and [001] directions, respectively. In essence, each
molecule donates hydrogen bonds to two neighbouring mol-
ecules and accepts two hydrogen bonds from two other mol-
ecules, so that, taken together, these interactions serve to link
the molecules into an extended three-dimensional framework.
Data collection
Nonius KappaCCD area-detector
diffractometer
' and ! scans with ꢄ offsets
15315 measured re¯ections
2900 independent re¯ections
2129 re¯ections with I > 2ꢅ(I)
Rint = 0.061
ꢆmax = 27.5ꢁ
Re®nement
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.052
wR(F2) = 0.139
S = 1.06
2898 re¯ections
178 parameters
H atoms: see below
w = 1/[ꢅ2(Fo2) + (0.0656P)2
+ 0.1385P]
2
where P = (Fo + 2Fc2)/3
(Á/ꢅ)max = 0.001
3
Ê
Áꢇmax = 0.31 e A
3
Ê
0.30 e A
Áꢇmin
Extinction correction: SHELXL97
=
Extinction coef®cient: 0.067 (12)
Table 1
Hydrogen-bond geometry (A, ) for (IV).
ꢁ
Ê
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
O2ÐH2Á Á ÁO1i
O7ÐH7Á Á ÁO4ii
N3ÐH3Á Á ÁO7iii
1.08 (3)
0.95 (3)
0.89 (2)
1.55 (4)
1.74 (3)
1.98 (2)
2.6307 (16)
2.6780 (16)
2.8523 (18)
174 (3)
167 (2)
166 (2)
Symmetry codes: (i) x ‡ 1; y ‡ 2; z; (ii) x ‡ 1; y ‡ 1; z; (iii) x, y ‡ 1, z.
Compound (V)
Crystal data
Experimental
C13H15NO3
Mr = 233.27
Z = 4
Dx = 1.316 Mg m
Mo Kꢀ radiation
ꢃ = 0.09 mm
T = 160 (1) K
Prism, colourless
0.35 Â 0.20 Â 0.20 mm
3
Compound (III) was prepared in 88% yield by the reaction of dl-
tropic acid, (I) (332 mg, 2 mmol), and 2,2,N-trimethyl-N-phenyl-2H-
azirin-3-amine, (II) (370 mg, 2.11 mmol), in tetrahydrofuran (20 ml)
at room temperature, according to a known protocol (Obrecht &
Heimgartner, 1987). Hydroxy acid (IV) was obtained by treatment of
(III) (340 mg, 1 mmol) with a 3 N solution of HCl in tetrahydrofuran
(3 ml) for 4 h at room temperature and subsequent extraction with
ethyl acetate. Suitable crystals of (IV) were obtained by slow
recrystallization from a mixture of dichloromethane±2-propanol±
hexane (m.p. 498±501 K). The treatment of (IV) (126 mg, 0.5 mmol)
with N,N0-dicyclohexylcarbodiimide (104 mg, 0.5 mmol) in ethyl
acetate (10 ml) overnight at room temperature, followed by ®ltration,
washing with ethyl acetate and recrystallization of the residue from
acetonitrile, yielded 93 mg (79%) of (V) (m.p. 392±395 K). The
treatment of (IV) (126 mg, 0.5 mmol) with Bu2SnO (50 mg) in xylene
(150 ml) under re¯ux for 2 d (Iliev et al., 2003), followed by
evaporation of the solvent, washing with diethyl ether and recrys-
tallization from acetone±hexane±2-propanol, yielded 9 mg (5%) of
(VI) as colourless crystals. The same compound was isolated in small
Monoclinic, P21=c
1
Ê
a = 10.1934 (2) A
Ê
b = 9.9466 (2) A
Ê
c = 11.9331 (3) A
ꢁ = 103.3915 (9)ꢁ
3
Ê
V = 1177.00 (4) A
Data collection
Nonius KappaCCD area-detector
diffractometer
' and ! scans with ꢄ offsets
28758 measured re¯ections
3422 independent re¯ections
2638 re¯ections with I > 2ꢅ(I)
Rint = 0.047
ꢆmax = 30.0ꢁ
Re®nement
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.042
wR(F2) = 0.108
S = 1.04
3421 re¯ections
161 parameters
H atoms: see below
w = 1/[ꢅ2(Fo2) + (0.0472P)2
+ 0.2303P]
2
where P = (Fo + 2Fc2)/3
(Á/ꢅ)max = 0.001
3
Ê
Áꢇmax = 0.23 e A
3
Ê
0.21 e A
Áꢇmin
Extinction correction: SHELXL97
=
Extinction coef®cient: 0.020 (4)
ꢀ
o342 Linden et al. C13H17NO4, C13H15NO3 and C26H30N2O6
Acta Cryst. (2006). C62, o339±o343

organic compounds
Table 2
Hydrogen-bond geometry (A, ) for (V).
indicates that the compound in the crystal is racemic. In the absence
of signi®cant anomalous dispersion effects, Friedel opposites were
merged prior to the ®nal cycles of re®nement and the absolute
structure was assigned arbitrarily. The amide, hydroxy and carboxylic
acid H atoms of (IV), the hydroxy H atom of (V) and the amide H
atoms of (VI) were placed in the positions indicated by difference
electron-density maps and their positions were allowed to re®ne
together with individual isotropic displacement parameters. In each
structure, the methyl H atoms were constrained to an ideal geometry
ꢁ
Ê
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
O15ÐH15Á Á ÁN1i
0.915 (19)
1.92 (2)
2.8316 (12)
174.8 (16)
Symmetry code: (i) x ‡ 2; y ‡ 1; z ‡ 1.
Compound (VI)
Ê
[CÐH = 0.98 A and Uiso(H) = 1.5Ueq(C)], but were allowed to rotate
Crystal data
freely about the CÐC bonds. All other H atoms were placed in
geometrically idealized positions and constrained to ride on their
Ê
parent C atom at distances of 0.95, 0.99 or 1.00 A for phenyl,
C26H30N2O6
Mr = 466.53
Monoclinic, Cc
a = 15.9437 (2) A
b = 19.1979 (4) A
Z = 4
Dx = 1.228 Mg m
Mo Kꢀ radiation
ꢃ = 0.09 mm
T = 160 (1) K
Prism, colourless
0.15 Â 0.15 Â 0.10 mm
3
methylene or methine groups, respectively, and with Uiso(H) =
1.2Ueq(C). For (IV), (V) and (VI), two, one and four low-angle
re¯ections, respectively, were omitted from the ®nal cycles of
re®nement because their observed intensities were much lower than
the calculated values as a result of being partially obscured by the
beam stop.
1
Ê
Ê
Ê
c = 11.2587 (2) A
ꢁ = 132.9182 (7)ꢁ
3
Ê
V = 2523.69 (8) A
Data collection
For all compounds, data collection: COLLECT (Nonius, 2000); cell
re®nement: DENZO-SMN (Otwinowski & Minor, 1997); data
reduction: DENZO-SMN and SCALEPACK (Otwinowski & Minor,
1997); structure solution: SIR92 (Altomare et al., 1994); structure
re®nement: SHELXL97 (Sheldrick, 1997); molecular graphics:
ORTEPII (Johnson, 1976); software used to prepare material for
publication: SHELXL97 and PLATON (Spek, 2003).
Nonius KappaCCD area-detector
diffractometer
! scans with ꢄ offsets
16028 measured re¯ections
2217 independent re¯ections
1883 re¯ections with I > 2ꢅ(I)
Rint = 0.058
ꢆmax = 25.0ꢁ
Re®nement
Re®nement on F2
R[F2 > 2ꢅ(F2)] = 0.038
wR(F2) = 0.097
S = 1.07
2215 re¯ections
357 parameters
H atoms: see below
w = 1/[ꢅ2(Fo2) + (0.0575P)2
+ 0.2754P]
where P = (Fo2 + 2Fc2)/3
(Á/ꢅ)max = 0.001
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GD3017). Services for accessing these data are
described at the back of the journal.
3
Ê
Áꢇmax = 0.22 e A
3
Ê
0.17 e A
Áꢇmin
Extinction correction: SHELXL97
=
Extinction coef®cient: 0.0056 (10)
References
Table 3
Selected torsion angles (ꢁ) for (VI).
Alfonso, M., Wang, Y. & Stoeckli-Evans, H. (2001). Acta Cryst. C57, 1184±
1188.
O1ÐC2ÐC3ÐN4
C2ÐC3ÐN4ÐC5
C3ÐN4ÐC5ÐC6
N4ÐC5ÐC6ÐC7
C5ÐC6ÐC7ÐO8
C6ÐC7ÐO8ÐC9
C7ÐO8ÐC9ÐC10
51.6 (3)
42.9 (4)
173.7 (2)
126.5 (3)
63.0 (3)
O8ÐC9ÐC10ÐN11
C9ÐC10ÐN11ÐC12
C10ÐN11ÐC12ÐC13
N11ÐC12ÐC13ÐC14
C12ÐC13ÐC14ÐO1
C13ÐC14ÐO1ÐC2
C14ÐO1ÐC2ÐC3
48.8 (3)
44.2 (3)
173.8 (3)
127.6 (3)
64.5 (3)
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Int. Ed. Engl. 34, 1555±1573.
179.9 (2)
178.2 (2)
179.3 (2)
177.6 (2)
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909±915.
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1079±1094.
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Table 4
Hydrogen-bond geometry (A, ) for (VI).
ꢁ
Ê
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
N4ÐH4Á Á ÁO2i
0.80 (3)
0.85 (4)
2.37 (3)
2.16 (4)
3.138 (3)
2.983 (4)
160 (3)
161 (3)
N11ÐH11Á Á ÁO9ii
Symmetry codes: (i) x
1
2
;
y ‡ 32; z 12; (ii) x; y ‡ 2; z ‡ 12.
Koch, K. N., Linden, A. & Heimgartner, H. (2000). Helv. Chim. Acta, 83, 1881±
1900.
Koch, K. N., Linden, A. & Heimgartner, H. (2001). Tetrahedron, 57, 2311±
2326.
In the structure of compound (VI), one of the phenyl rings is
disordered over two orientations which result from a pivot about the
C17Á Á ÁC20 axis of the ring. Two positions were de®ned for each of the
other four atoms of this ring and re®nement of constrained site-
occupation factors for the two orientations yielded a value of 0.67 (3)
for the major conformation. All CÐC bond lengths within both
orientations of the disordered ring were restrained to be similar,
while neighbouring atoms within and between each conformation of
the disordered ring were restrained to have similar atomic displace-
ment parameters. Compound (VI) crystallized in a non-centrosym-
metric space group with a polar axis, but the presence of glide planes
È
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Sweet, pp. 307±326. New York: Academic Press.
È
Sheldrick, G. M. (1997). SHELXL97. University of Gottingen, Germany.
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ꢀ
Acta Cryst. (2006). C62, o339±o343
Linden et al.
C13H17NO4, C13H15NO3 and C26H30N2O6 o343