Chemistry of unique chiral olefins. 1. Synthesis, enantioresolution, circular dichroism, and theoretical determination of the absolute stereochemistry of trans- and cis-1,1',2,2',3,3',4,4'-Octahydro-4,4'- biphenanthrylidenes

Article abstract of DOI:10.1021/ja970667u

Unique chiral olefins, (E)-1,1',2,2',3,3',4,4'-octahydro-4,4'-biphenanthrylidene (1) and its (Z)-isomer 2, were synthesized. When these compounds are directly enantioresolved by using the HPLC Okamoto column with a chiral stationary phase, optically pure enantiomers were obtained. The CD spectra of these chiral olefins exhibit very intense Cotton effects in the ¹B(b) transition region reflecting their strongly twisted π-electron systems. The CD and UV spectra of chiral olefins (M,M)-E-1 and (M,M)-(Z)-2 were theoretically calculated by the π-electron self-consistent field/configuration interaction/dipole velocity molecular orbital method. From the calculation results, the absolute stereostructures of these chiral olefins were theoretically determined to be [CD(+)239.0]-(M,M)-(E)-1 and [CD(+)238.1]-(M,M)-(Z)-2, respectively.

Full text of DOI:10.1021/ja970667u

J. Am. Chem. Soc. 1997, 119, 7241-7248
7241
Chemistry of Unique Chiral Olefins. 1. Synthesis,
Enantioresolution, Circular Dichroism, and Theoretical
Determination of the Absolute Stereochemistry of trans- and
cis-1,1′,2,2′,3,3′,4,4′-Octahydro-4,4′-biphenanthrylidenes
Nobuyuki Harada,*,1a Akira Saito,1a Nagatoshi Koumura,1a Hisashi Uda,1a
Ben de Lange,1b Wolter F. Jager,1b Hans Wynberg,1b and Ben L. Feringa*,1b
Contribution from the Institute for Chemical Reaction Science, Tohoku UniVersity,
2-1-1 Katahira, Aoba, Sendai 980-77, Japan, and Department of Organic and Molecular
Inorganic Chemistry, Groningen Centre for Catalysis and Synthesis, UniVersity of Groningen,
Nijenborgh 4, 9747 AG Groningen, The Netherlands
ReceiVed March 3, 1997X
Abstract: Unique chiral olefins, (E)-1,1′,2,2′,3,3′,4,4′-octahydro-4,4′-biphenanthrylidene (1) and its (Z)-isomer 2,
were synthesized. When these compounds are directly enantioresolved by using the HPLC Okamoto column with
a chiral stationary phase, optically pure enantiomers were obtained. The CD spectra of these chiral olefins exhibit
very intense Cotton effects in the 1Bb transition region reflecting their strongly twisted π-electron systems. The CD
and UV spectra of chiral olefins (M,M)-(E)-1 and (M,M)-(Z)-2 were theoretically calculated by the π-electron self-
consistent field/configuration interaction/dipole velocity molecular orbital method. From the calculation results, the
absolute stereostructures of these chiral olefins were theoretically determined to be [CD(+)239.0]-(M,M)-(E)-1 and
[CD(+)238.1]-(M,M)-(Z)-2, respectively.
Introduction
Chart 1
There are various kinds of chiral compounds devoid of centers
of chirality. Those compounds cannot take a planar structure
because of strong steric hindrance. One of these compounds
incorporates the class of binaphthyl derivatives with the axis
of chirality; some chiral binaphthyl compounds have been used
for synthetic reactions as chiral auxiliaries, chiral reagents, chiral
catalysts, or chiral hosts of chiral recognition. Another class
of chiral compounds without center of chirality is that of
helicenes. A hexahelicene composed of six condensed benzene
rings is a very interesting compound, whose structure and
chemical behavior have been studied well.2,3 Investigating a
class of such chiral compounds devoid of centers of chirality,
one group of the authors reported almost 20 years ago the
synthesis and partial enantioresolution of chiral olefins, (E)-
1,1′,2,2′,3,3′,4,4′-octahydro-4,4′-biphenanthrylidene (1) and its
(Z)-isomer (2), in a preliminary form (Chart 1).4 These chiral
olefins are members of an unique class of helical-shaped
sterically overcrowded alkenes, several of which show intriguing
photochromic and stereochemical properties5 and which form
the basis for so-called chiroptical molecular switches.6
actually resolved into enantiomers by the HPLC method using
a chiral stationary phase.4,7 The CD spectra of these chiral
olefins exhibited intense Cotton effects reflecting their strongly
twisted π-electron systems. In spite of their unique structures
and behavior, their absolute configuration has remained un-
determined. In this paper, we report the theoretical determi-
nation of the absolute stereochemistry of these chiral olefins in
addition to the details of synthesis, enantioresolution, config-
uration and conformation, and CD spectra.8
These chiral olefins (1 and 2) cannot take a planar structure
because of steric hindrance, and hence, those compounds were
X Abstract published in AdVance ACS Abstracts, July 15, 1997.
(1) (a) Tohoku University. (b) University of Groningen.
(2) (a) Lightner, D. A.; Hefelfinger, D. T.; Frank, G. W.; Powers, T.
W.; Trueblood, K. N. Nature 1971, 232, 124. (b) Brown, A.; Kemp, C.
M.; Mason, S. F. J. Chem. Soc. A 1971, 751, 756.
(3) See also heterohelicenes: Groen, M. B.; Wynberg, H. J. Am. Chem.
Soc. 1971, 93, 2968 and references cited therein.
(4) Feringa, B.; Wynberg, H. J. Am. Chem. Soc. 1977, 99, 602.
(5) Jager, W. F.; de Jong, J. C.; de Lange, B.; Huck, N. P. M.; Meetsma,
A.; Feringa, B. L. Angew. Chem., Int. Ed. Engl. 1995, 34, 348. Feringa, B.
L.; Jager, W. F.; de Lange, B.; Meijer, E. W. J. Am. Chem. Soc. 1991, 113,
5468 and references cited therein.
(6) Huck, N. P. M.; Jager, W. F.; de Lange, B.; Feringa, B. L. Science
1996, 273, 1686. Feringa, B. L.; Huck, N. P. M.; van Doren, H. A. J. Am.
Chem. Soc. 1995, 117, 9929. Feringa, B. L.; Huck, N. P. M.; Schoevaars,
A. M. AdV. Mater. 1996, 8, 681 and references cited therein.
To determine the absolute stereochemistry of chiral com-
pounds having a twisted π-electron system, we have used the
(7) See also: Saito, A. M.S. Thesis, Tohoku University, 1987.
(8) The theoretical determination of these chiral olefins was reported in
a preliminary paper: Harada, N.; Saito, A.; Uda, H.; Feringa, B. L.;
Wynberg, H. Conference Proceedings, F.E.C.S. 2nd International Confer-
ence on Circular Dichroism, Budapest, August 1987.
S0002-7863(97)00667-7 CCC: $14.00 © 1997 American Chemical Society

7242 J. Am. Chem. Soc., Vol. 119, No. 31, 1997
Harada et al.
theoretical method to calculate the CD spectra by the π-electron
self-consistent field/configuration interaction/dipole velocity
molecular orbital method (SCF-CI-DV MO method).9-11 For
example, by applying this method, we have succeeded in
determining the absolute configuration of many natural and
unnatural compounds with a twisted π-electron system, i.e.,
dihydroazulene derivatives isolated from liverworts,12 marine
natural products of halenaquinol family isolated from tropical
marine sponges,13,14 chiral troponoid spiro compounds,15 chiral
cyanin dyes,16 biflavone of natural atropisomer isolated from
plants,17,18 and ternaphthalene compounds.19 The reliability of
this theoretical method has been established by many application
examples of synthetic chiral aromatic compounds.11 The chiral
olefins 1 and 2 also belong to the class of chiral compounds
with twisted π-electron systems, and therefore, the theoretical
method would be useful for these compounds. We have
succeeded in determining the absolute stereochemistry of these
chiral olefins in a nonempirical manner, as described below.
The mechanism of the intense CD Cotton effect is also
discussed.
Definition of the Absolute Configuration of Chiral Olefins
(E)-1 and (Z)-2. Unlike helicenes, these chiral olefins have
two moieties of helicity, i.e., helicity between one naphthalene
plane and central double bond and another helicity between the
other naphthalene plane and central double bond. Therefore,
the enantiomer shown in Figure 1a is defined as (M,M)-(E)-
olefin 1.20 The other enantiomer in Figure 1b is (P,P)-(E)-olefin
1. It should be noted that if (M,P)-(E)-olefin 1 can exist, it is
an optically inactive meso-olefin. For cis-olefin 2, the absolute
configuration was similarly defined (Figure 1). (M,P)-(Z)-Olefin
2 is a meso-compound, although it may be extremely unstable
and unfavorable due to steric hindrance.
Figure 1. Stereoscopic view of chiral olefins, (M,M)-(E)-1, (P,P)-
(E)-1, (M,M)-(Z)-2, and (P,P)-(Z)-2, calculated by the MOPAC 93 AM1
programs.
stereoscopic views are illustrated in Figure 1. The atomic coordinates
obtained were used for the following calculation of CD and UV spectra.
Computational Methods: Numerical Calculation of CD and UV
Spectra. The CD and UV spectra of (M,M)-(E)-1 and (M,M)-(Z)-2
were calculated by the π-electron SCF-CI-DV MO method.9-11 In the
MO calculation, the configuration interactions between all singly excited
states were included, and the following standard values of atomic orbital
parameters were used: for aromatic carbon, W(C) ) -11.16 eV, (rr|rr)
(C) ) 11.13 eV, â(C-C, 1.388 Å) ) -2.32 eV, ∇ (C-C, 1.388 Å)
) 4.70 × 107 cm-1. The electric repulsion integral (rr|ss) was estimated
by the Nishimoto-Mataga equation. The resonance integral and del
values were calculated by employing the following equations, respec-
tively,
Computational Section
Computational Methods: Molecular Structure. The molecular
geometry of (M,M)-(E)-1, (P,P)-(E)-1, (M,M)-(Z)-2, and (P,P)-(Z)-2
was optimized using the MOPAC 93 AM1 programs.21 Their
(9) Moscowitz, A. Tetrahedron 1961, 13, 48.
(10) Kemp, C.; Mason, S. F. Tetrahedron 1966, 22, 629. See also ref
2b.
â ) [S/S(C-C, 1.388 Å)]â(C-C, 1.388 Å) cos θ
(1)
(11) Harada, N.; Nakanishi, K. Circular Dichroic Spectroscopy - Exciton
Coupling in Organic Stereochemistry; University Science Books: Mill
Valley, CA, and Oxford University Press: Oxford, 1983.
(12) Harada, N.; Kohori, J.; Uda, H.; Nakanishi, K.; Takeda, R. J. Am.
Chem. Soc. 1985, 107, 423. Harada, N.; Kohori, J.; Uda, H.; Toriumi, K.
J. Org. Chem. 1989, 54, 1820.
(13) Kobayashi, M.; Shimizu, N.; Kitagawa, I.; Kyogoku, Y.; Harada,
N.; Uda, H. Tetrahedron Lett. 1985, 26, 3833. Harada, N.; Sugioka, T.;
Ando, Y.; Uda, H.; Kuriki, T. J. Am. Chem. Soc. 1988, 110, 8483. Harada,
N.; Uda, H.; Kobayashi, M.; Shimizu, N.; Kitagawa, I. J. Am. Chem. Soc.
1989, 111, 5668. Harada, N.; Sugioka, T.; Soutome, T.; Hiyoshi, N.; Uda,
H.; Kuriki, T. Tetrahedron: Asymmetry 1995, 6, 375 and references cited
therein.
(14) See also: Harada, N.; Sugioka, T. In Studies in Natural Products
Chemistry; Atta-ur-Rahman, Ed.; Elsevier Science Publishers: Amsterdam,
1995; Vol. 17, p 33.
(15) Harada, N.; Uda, H,; Nozoe, T.; Okamoto, Y.; Wakabayashi, H.;
Ishikawa, S. J. Am. Chem. Soc. 1987, 109, 1661.
(16) Berova, N.; Gargiulo, D.; Derguini, F.; Nakanishi, K.; Harada, N.
J. Am. Chem. Soc. 1993, 115, 4769 and references cited therein.
(17) Harada, N.; Ono, H.; Uda, H.; Parveen, M.; Khan, N. U.-D.; Achari,
B.; Dutta, P. K. J. Am. Chem. Soc. 1992, 114, 7687.
∇ ) [ ∇ (empir, 1.388 Å)/ ∇ (theor, 1.388 Å)] ∇ (theor) cos θ
(2)
where S is the overlap integral and θ is the dihedral angle.
In the calculation of CD and UV spectra, the component CD and
UV bands were approximated by the Gaussian distribution.11
∆ꢀ(σ) )
ꢀ(σ) )
∆ꢀk exp[-((σ - σk)/∆σ)2]
ꢀk exp[-((σ - σk)/∆σ)2]
(3)
(4)
∑
∑
where 2∆σ is the 1/e width of the bands. The ∆σ values were adopted
from the observed UV spectra of chiral olefins 1 and 2. The numerical
calculations were carried out on the Sun S-4/10 Work Station in our
group and/or the NEC ACOS-3900 computer at the Computer Center
of Tohoku University.
(18) Recently, it was claimed that the X-ray crystallographic analysis
led to the absolute configuration opposite to that obtained by theoretical
calculation of CD spectra reported in ref 17 (Zhang, F.-J.; Lin, G.-Q.; Huang,
Q.-C. J. Org. Chem. 1995, 60, 6427). However, the claim was later
retracted: Additions and Corrections J. Org. Chem. 1996, 61, 5700.
(19) Harada, N.; Hiyoshi, N.; Vassilev, V. P.; Hayashi, T. Chirality. In
press. Harada, N.; Vassilev, V. P.; Hiyoshi, N. Enantiomer 1997, 2, 123.
(20) Cahn, R. S.; Ingold, C.; Prelog, V. Angew. Chem., Int. Ed. Engl.
1966, 5, 385.
Results and Discussion
Synthesis of Chiral Olefins: trans- and cis-1,1′,2,2′,3,3′,4,4′-
Octahydro-4,4′-biphenanthrylidenes. As reported in a pre-
liminary paper,4 chiral olefins, trans-1 and cis-2 were first
synthesized by one group of the authors. As shown in Scheme
1, 3-(2-naphthoyl)propionic acid (5a), which was prepared from
naphthalene (3) and succinic anhydride (4) according to the
(21) Stewart, J. J. P. MOPAC 93; Fujitsu Limited: Tokyo, Japan, 1993.

Chemistry of Unique Chiral Olefins. 1
J. Am. Chem. Soc., Vol. 119, No. 31, 1997 7243
Scheme 1a
adopts a boat conformation, giving rise to a large helicity
between naphthalene ring and central double bond, while the
central double bond is little deviated from a flat structure. The
characteristic geometrical values are as follows: central double
bond, C4-C4′ ) 1.350 Å; average value of the dihedral angle
between naphthalene plane and central double bond, C4′-C4-
C4a-C4b ) -56.9°; dihedral angles, C3′-C4′-C4-C4a )
-4.5° (average), C3′-C4′-C4-C3 ) +169.9°, C4′a-C4′-
C4-C4a ) -178.9°; distance, H1eq-H10 (eq ) equatorial)
) 2.39 Å, H3ax-H5′ ) 2.34 Å, H3eq-H5′ ) 2.72 Å. Those
values are almost in agreement with the experimental values
obtained by the X-ray analysis of 1 as shown below.
The stable conformation of cis-olefin 2 is also of C2-symmetry
and strongly twisted, two naphthalene rings closely overlapping
to each other: C4b-C4′b ) 3.507 Å. The cyclohexylidene
ring takes a boat conformation, and the torsional angle between
naphthalene ring and central double bond is also very large:
central double bond, C4-C4′ ) 1.356 Å; average value of the
dihedral angle between naphthalene plane and central double
bond, C4′-C4-C4a-C4b ) -51.0°; dihedral angles, C4′a-
C4′-C4-C4a ) -7.2°, C3′-C4′-C4-C3 ) -12.2°, C4′a-
C4′-C4-C3 ) +170.3° (average); distance, H1eq-H10 ) 2.38
Å, H1ax-H5′ ) 2.27 Å. The NOESY relation of H1eq-H10
and H1ax-H5′ is thus supported by the calculation.
X-ray Crystallographic Analysis of (()-trans-Olefin 1.
The structure of trans-olefin 1 was established by the X-ray
crystallographic analysis of its racemate. Although authors in
the Netherlands already reported the X-ray crystallographic
analysis and crystal structure of 1,25 authors in Japan also
performed the X-ray analysis to confirm its structure, because
the melting point (234-235 °C) of the sample prepared in the
Netherlands is much different from that (mp 213 °C) of the
sample in Japan.
a Key: (a) H2NNH2‚H2O, KOH/diethylene glycol; (b) PCl5; (c)
SnCl4/benzene; (d) TiCl3, LiAlH4/THF.
procedure of Haworth,22 was reduced by the Huang-Minlon
reaction to yield 4-(2-naphthyl)butanoic acid (6). Acid 6 was
converted to 2,3-dihydro-4(1H)-phenanthrenone (7) by the
Friedel-Crafts reaction (see the Supporting Information).23
Ketone 7 was then dimerized by the McMurry reaction24 using
a low-valent titanium reagent. After separation and purification
of the residue by HPLC on silica gel (hexane/benzene 10:1),
the desired chiral olefin trans-1 was obtained as a less-polar
product in low yield of 8.3-9.4%. trans-Olefin 1 was
recrystallized from hexane giving colorless crystals: mp 213
°C. cis-Olefin 2 was similarly obtained as a more polar product
in low yield of 2.5-4.5%: mp 192-195 °C (hexane). We have
examined the crude product of the coupling reaction in order
to isolate meso-olefins. However, all attempts were unsuccess-
ful.
Single crystals of colorless prisms suitable for X-ray analysis
were obtained by recrystallization from hexane: mp 213 °C.
The crystal was found to be monoclinic: space group C2/c (No.
15). One asymmetrical unit contained a half molecule of 1.
The skeletal structure was solved by direct methods and
successive Fourier syntheses. All hydrogen atoms were found
by the difference Fourier syntheses. Full-matrix least-squares
refinement of positional and thermal parameters led to the final
convergence with R ) 0.0688 and Rw ) 0.0577. The trans-
geometry of 1 was thus established as shown in Figure 2.
The geometry of compound 1 in the solid state is character-
ized as follows: central double bond, C4-C4′ ) 1.318 Å;
average value of the dihedral angle between naphthalene plane
and central double bond, C4-C4′-C4′a-C4′b ) -60.6°;
dihedral angles, C3-C4-C4′-C4′a ) -8.3° (average), C3-
C4-C4′-C3′ ) +163.2°, C4a-C4-C4′-C4′a ) -179.8°;
dihedral angle between planes C3-C4-C4′ and C4a-C4-C4′
) -171.5°. The central double bond is thus a little twisted,
and the sp2 carbon atoms are deviated from a plane structure.
These geometrical parameters are almost in agreement with the
previous X-ray results.25 The previous X-ray analysis revealed
that the crystal used was tetragonal, taking space group I4h, and
its melting point was different from that of the sample used
here. Therefore, this compound may undergo polymorphism.
The proton-proton distance correlating to the 1H NMR
NOESY phenomena was calculated from the X-ray data:
H1eq-H10 ) 2.36 Å, H3ax-H5′ ) 2.57 Å, H3eq-H5′ ) 2.79
Å. The X-ray analysis thus confirmed the relationship between
proton-proton distance and NOESY data.
The structure of chiral olefins 1 and 2 were determined mainly
by NMR spectra. 1H and 13C NMR spectra of trans- and cis-
olefins indicated their structures to have C2-symmetry, and all
signals were fully assigned by the analysis of HSQC, HMBC,
and NOESY spectra (see the Experimental Section and the
1
Supporting Information). In the H NMR spectrum of trans-
olefin 1, all aromatic protons appear in the region of regular
aromatic protons, δ 7.3-8.3 ppm. On the other hand, the
aromatic protons of cis-olefin 2 appear in a higher magnetic
field, δ 6.6-7.3 ppm. These upper-field shifts are due to the
diamagnetism generated by the aromatic ring current of
overlapped two naphthalene rings in cis-olefin 2. The assign-
ment of trans- and cis-geometry was further confirmed by the
analysis of NOESY spectra. The 1H-1H NOESY spectrum of
trans-olefin 1 exhibits a cross peak between H3 and H5′; this
phenomenon can be explained only by the trans-structure. In
the case of cis-olefin 2, a cross peak between H1ax (ax ) axial)
and H5′ was observed in the NOESY spectrum, indicating the
cis-olefin structure.
Conformation of Chiral Olefins: trans-1 and cis-2. The
chiral olefins 1 and 2 cannot take planar structures because of
steric hindrance and hence are strongly twisted. Their preferred
conformations were calculated by using the MOPAC 93 AM1
programs (Figure 1). The conformations of 1 and 2 calculated
are of C2-symmetry in agreement with the NMR results
described above. For trans-olefin 1, the cyclohexylidene ring
(22) Haworth, R. D. J. Chem. Soc. 1932, 1125.
(23) Bachemann, W. E.; Cortes, G. D. J. Am. Chem. Soc. 1943, 65, 1329.
Agranat, I.; Shih, Y.-S. Synthesis 1974, 865.
(24) McMurry, J. E. Acc. Chem. Res. 1974, 7, 281. McMurry, J. E. Acc.
Chem. Res. 1983, 16, 405. Dams, R.; Malinowski, M.; Westdorp, I.; Geise,
H. Y. J. Org. Chem. 1982, 47, 158.
Enantioresolution of (()-(E)-Olefin 1 by HPLC. In the
previous preliminary paper,4 the HPLC alumina column im-
(25) Feringa, B.; Wynberg, H.; Duisenberg, A. J. M.; Spek, A. L. Recl.
TraV. Chim. Pays-Bas. 1979, 98, 1.

7244 J. Am. Chem. Soc., Vol. 119, No. 31, 1997
Harada et al.
2 of the first-eluted fraction was obtained in an almost
enantiopure form. As reported in the second paper of this series,
we found the unexpected thermal racemization of cis-olefin 2
at room temperature,28 and therefore, the CD and UV spectra
were immediately measured after enantioresolution. From the
CD data, the first-eluted enantiomer was designated as
[CD(+)238.1]-(Z)-2. The CD spectrum of the second-eluted
fraction was similarly measured, and its CD Cotton effects
observed were opposite in sign to those of the first-eluted
enantiomer, although its CD Cotton effects were considerably
weak. The second-eluted enantiomer was thus designated as
[CD(-)238.1]-(Z)-2.
CD and UV Spectra of the First-Eluted Enantiomers
[CD(+)239.0]-(E)-Olefin 1 and [CD(+)238.1]-(Z)-Olefin 2.
Both chiral olefins 1 and 2 are composed of two naphthalene
chromophores connected with the central double bond, and
therefore, the π-electron conjugation is widespread almost over
the molecular system. The UV spectrum of (E)-1, however,
shows intense absorption bands similar to those of naphthalene,
maintaining the nature of naphthalene chromophore: UV
(MeOH) λmax 329.8 nm (ꢀ 17 400), 318.8 (17 300), 232.2
(61 800), 216.2 (82 800) (Table 1 and Figure 3). Therefore,
the absorption band of medium intensity at 329.8 nm may be
assigned to the 1La transition of naphthalene, although it shows
Figure 2. ORTEP drawing of racemic trans-olefin (()-(E)-1. The
figure does not express its absolute stereochemistry. The atoms are
drawn at 50% probability.
pregnated with (+)-2-(((2,4,5,7-tetranitro-9-fluorenylidene)-
amino)oxy)propionic acid (TAPA) was used for enantio-
resolution. Since the resolutions on the chiral TAPA column
were however difficult, we explored other chiral HPLC columns.
The HPLC column with a chiral stationary phase of (+)-
poly(triphenylmethyl methacrylate) developed by Okamoto and
co-workers has been extensively employed for enantioresolution
of various racemates.26 The Okamoto column (commercially
available as Chiralpak OT(+) from Daicel Co. Ltd) was used
for direct enantioresolution of trans-olefin 1. After several trials,
we found that hydrocarbon 1 could be completely resolved into
enantiomers under the reverse phase condition using methanol
as eluent and a column temperature of 3 °C. The sample of
(()-trans-1 was injected as a methanol solution, and separation
of enantiomers was monitored by a UV detector. Both
enantiomers were completely resolved by this method: R )
2.01, Rs ) 1.51 (see the Supporting Information). On the other
hand, cis-olefin 2 was not separated. Since a small amount of
the polymer of the chiral stationary phase was present as a
contaminant, the fraction of each enantiomer resolved was
purified by HPLC (ODS-C18, MeOH). From the first eluted
fraction, chiral olefin [CD(+)239.0]-(E)-1 was obtained;27 the
1H NMR data of optically active 1 were identical with those of
(()-1. From the second-eluted fraction, chiral olefin
[CD(-)239.0]-(E)-1 was obtained, and its CD Cotton effects
were opposite in sign but almost equal in intensity to those of
[CD(+)239.0]-(E)-1.
1
a red shift of ca. 55 nm when compared with the La band of
naphthalene at 275 nm. The remaining two intense bands at
232.2 and 216.2 nm may be due to the 1Bb transition of
naphthalene. Those phenomena can be interpreted as follows:
since the dihedral angle between the naphthalene chromophore
and the central double bond in trans-olefin 1 is as large as 60°,
the π-electron conjugation between naphthalene and double-
bond chromophores are strongly inhibited. Therefore, the
π-electron system of trans-olefin 1 retains the nature of the
naphthalene chromophore.
The CD spectrum of the first-eluted enantiomer [CD-
(+)239.0]-(E)-1 exhibits very intense Cotton effects of a
complex pattern: CD (MeOH) λext 331.8 nm (∆ꢀ +26.0), 253.4
(-20.9), 239.0 (+58.2), 224.8 (-76.4), 214.2 (-153.3) (Table
1 and Figure 3). A positive Cotton effect of medium intensity
1
at 331.8 nm is assigned to the La transition, but the origin of
the negative Cotton effect at 253.4 nm is unknown, since its
wavelength position is deviated from the UV absorption
maximum. In the 1Bb transition region, a strong positive Cotton
effect at 239.0 nm and two very intense negative Cotton effects
at 224.8 and 214.2 nm are observed. The CD amplitude, A
()∆ꢀpeak - ∆ꢀtrough), in this region is +211.5. These strong
CD Cotton effects reflect the fact that the π-electron system of
trans-1 is strongly twisted.
Enantioresolution of (()-(Z)-Olefin 2 by HPLC. cis-Olefin
2 could not be resolved under the reverse phase condition using
methanol as eluent. When the solvent was changed from
methanol to hexane, we found that cis-olefin 2 was partially
separated into enantiomers at 3 °C: R ) 1.09 (see the
Supporting Information). On the other hand, trans-olefin 1
could not be resolved under this normal phase condition. Since
the separation of two enantiomers of 2 was not perfect, the first-
eluted fraction was recycled five times, where in each time the
band of the second-eluted enantiomer was shaved from the
recycle path. After recycling the fraction five times, cis-olefin
The UV spectrum of (Z)-2 also resemble those of naphtha-
lene: UV (MeOH) λmax 329.3 nm (ꢀ 7 800)sh, 301.9 (11 300),
222.8 (71 900) (Table 1 and Figure 4). The absorption band
of medium intensity at 301.9 nm is assigned to the 1La transition
of naphthalene and the intense band at 223.0 nm to the Bb
transition. The π-electron system of cis-olefin 2 also retains
the characteristics of naphthalene chromophore.
1
The CD spectrum of the first-eluted enantiomer [CD-
(+)238.1]-(Z)-2 also shows very intense Cotton effects of
complex pattern: CD (MeOH) λext 339.0 nm (∆ꢀ -12.3), 303.8
(-8.4), 281.5 (+8.5), 256.0 (-63.2), 238.1 (+189.7), 223.5
(-239.3) (Table 1 and Figure 4). A negative weak Cotton effect
(26) Okamoto, Y.; Suzuki, K.; Ohta, K.; Hatada, K.; Yuki, H. J. Am.
Chem. Soc. 1979, 101, 4763. Okamoto, Y.; Honda, S.; Okamoto, I.; Yuki,
H.; Murata, S.; Noyori, R.; Takaya, H. J. Am. Chem. Soc. 1981, 103, 6971
and references cited therein.
1
at 339.0 nm is assigned to the La transition, but the origin of
the weak positive Cotton effect at 281.5 nm and the negative
(27) For definition of enantiomer by using CD data, see: Harada, N.;
Iwabuchi, J.; Yokota, Y.; Uda, H.; Okamoto, Y.; Yuki, H.; Kawada, Y. J.
Chem. Soc., Perkin Trans. 1 1985, 1845. Harada, N. Enantiomer 1996, 1,
81.
(28) For papers of this series, see: (a) (part 2) Harada, N.; Saito, A.;
Koumura, N.; Roe, D. C.; Jager, W. F.; Zijlstra, R. W. J.; de Lange, B.;
Feringa, B. L. J. Am. Chem. Soc. 1997, 119, 7249. (b) (part 3) Harada, N.;
Koumura, N.; Feringa, B. L. J. Am. Chem. Soc. 1997, 119, 7256.

Chemistry of Unique Chiral Olefins. 1
J. Am. Chem. Soc., Vol. 119, No. 31, 1997 7245
Table 1. Observed and Calculated UV and CD Spectra of Chiral Olefins and Related Compounds
obsd (MeOH or hexane)
calcd (π-SCF-CI-DV MO)
compound
(M,M)-(E)-1a
UV, λmax nm (ꢀ)
CD, λext nm (∆ꢀ)
331.8 (+26.0)
UV, λmax nm (ꢀ)
CD, λext nm (∆ꢀ)
295.9 (+7.9)
329.8 (17 400)
318.8 (17 300)
295.9 (18 700)
253.4 (-20.9)
239.0 (+58.2)
224.8 (-76.4)
214.2 (-153.3)
232.2 (61 800)
216.2 (82 800)
240.4 (+87.9)
219.3 (-256.0)
223.2 (94 400)
274.7 (7 000)
(M,M)-(E)-8
273.2 (+4.2)
230.4 (+248.0)
211.9 (-244.2)
219.3 (119 100)
329.0 (6 400)
(M,M)-(Z)-2b,c
329.3 (7 800)sh
301.9 (11 300)
339.0 (-12.3)
303.8 (-8.4)
281.5 (+8.5)
256.0 (-63.2)
238.1 (+189.7)
223.5 (-239.3)
331.1 (-48.8)
260.4 (-12.8)
232.6 (+76.7)
215.5 (-158.0)
223.0 (73 700)
211.9 (57 600)
271.7 (2 200)
(M,M)-(Z)-9
270.2 (-9.5)
234.7 (+215.9)
215.5 (-372.8)
208.3 (79 300)
a Observed in MeOH. b Observed in hexane. c sh: shoulder.
Figure 3. Observed CD and UV spectra of the first-eluted trans-olefin
[CD(+)239.0]-(M,M)-(E)-1 in methanol.
Figure 4. Observed CD and UV spectra of the first-eluted cis-olefin
[CD(+)238.1]-(M,M)-(Z)-2 in hexane.
Cotton effect at 256.0 nm is again unknown. In the 1Bb
transition region, very intense positive and negative Cotton
effects are observed at 238.1 and 223.5 nm, respectively. The
CD amplitude, A ()+429.0), is much larger than that of trans-
olefin 1. These intense CD Cotton effects indicate that the
π-electron system of cis-2 is also strongly twisted.
Theoretical Determination of the Absolute Stereochem-
istry of trans-Olefin [CD(+)239.0]-(E)-1. To determine the
absolute stereochemistry of these chiral olefins in a nonempirical
manner, their CD and UV spectra were calculated by the
π-electron SCF-CI-DV MO method.9-11 As the model system
used for the theoretical calculation of CD spectra, the (M,M)-
(E)-enantiomer 1 was arbitrarily chosen. The atomic coordinates
of π-electron carbon atoms were obtained from the MOPAC
93 AM1 calculation results. The angular dependence of the
resonance integral was calculated by eq 1, where angle θ was
estimated from the dihedral angle between naphthalene plane
and central double bond. The shape of component CD and UV
bands was approximated by the Gaussian distribution as shown
in eqs 3 and 4. The 2∆σ values, 1/e bandwidth, were adopted
from the observed UV spectra of chiral olefin 1.
The UV spectrum of (M,M)-(E)-enantiomer 1 was well
reproduced by the calculation: calculated, λmax 295.9 nm (ꢀ
18 700) and 223.2 (94 400); observed, λmax 329.8 nm (ꢀ 17 400),

7246 J. Am. Chem. Soc., Vol. 119, No. 31, 1997
Harada et al.
Chart 2. Hypothetical Model Compounds 8 and 9
Table 2. Calculated Dipole and Rotational Strengths of the
Transitions of Chiral Olefins and Their Hypothetical Model
Compounds
compound/
transition no.
wavelength
(λ), nm
dipole strength
rotational strength
(1036D), cgs unit
(1040R), cgs unit
(M,M)-(E)-1
22.6
1
2
3
4
5
6
296.7
248.9
227.3
223.9
219.2
216.2
+22.6
+74.5
2.9
20.6
58.1
1.5
+1467.8
-1907.4
+24.9
7.6
+83.3
(M,M)-(E)-8
7.8
1
2
3
4
274.6
271.0
222.9
219.5
+9.4
+2.4
+2281.2
-2200.0
0.1
32.9
71.0
(M,M)-(Z)-2
1
2
3
4
5
6
7
8
9
330.2
281.5
260.8
243.4
242.6
235.4
226.7
219.3
215.6
8.5
3.7
0.2
6.2
6.2
5.7
5.2
0.3
36.0
-163.7
-31.7
-9.3
-400.9
+384.7
+1.6
+334.0
-13.7
-615.0
Figure 5. CD and UV spectral curves of trans-olefin (M,M)-(E)-1
calculated by the π-electron SCF-CI-DV MO method.
318.8 (17 300), 232.2 (61 800), and 216.2 (82 800) (Figure 5
and Table 1). The calculated 1La band appeared in much shorter
wavelength region than the observed one. The CD spectrum
of (M,M)-(E)-enantiomer 1 was also calculated by the π-electron
SCF-CI-DV MO method: calculated, λext 295.9 nm (∆ꢀ +7.9),
240.4 (+87.9), and 219.3 (-256.0); observed, λext 331.8 nm
(∆ꢀ +26.0), 253.4 (-20.9), 239.0 (+58.2), 224.8 (-76.4), and
214.2 (-153.3) (Figure 5 and Table 1). Although the location
and intensity of the calculated CD Cotton effect of 1La transition
are much different from the observed ones, its positive sign
agrees with that of observed one. In the 1Bb transition region,
the intense positive and negative Cotton effects around 240 and
220 nm, respectively, were well reproduced by the π-electron
SCF-CI-DV MO calculations. The basic pattern of the calcu-
lated and observed CD spectra thus agree with each other, and
therefore, the absolute stereochemistry of the first-eluted trans-
olefin [CD(+)239.0]-(E)-(1) was nonempirically determined to
be (M,M) by the theoretical calculation of its CD spectrum.
To clarify the mechanism of the intense CD Cotton effects
in the 1Bb transition region, the following computational
experiments were performed. We supposed a hypothetical
compound (M,M)-(E)-8 where the central double bond was
blocked by an appropriate substituent, e.g., epoxide or cyclo-
propane moiety, but the coordinates of the remaining atoms were
kept as the same as those of the original trans-olefin (M,M)-
(E)-1 (Chart 2). In this compound, the π-electron system is
composed of two isolated naphthalene chromophores, and
therefore, intense bisignate split Cotton effects due to the exciton
coupling between two naphthalene chromophores are expected.
In fact, the calculation of CD and UV spectra of this hypothetical
model compound gave intense positive first and negative second
Cotton effects in the 1Bb transition region as shown in Table 1
(see the Supporting Information). In Table 2, the calculated
dipole and rotational strengths of the transitions of chiral olefin
(M,M)-(E)-1 and model compound (M,M)-(E)-8 are listed. The
(M,M)-(Z)-9
1
2
3
4
277.2
270.5
231.0
216.2
0.9
1.7
9.8
+12.6
-38.3
+691.9
-1062.0
48.0
transitions of numbers 3 and 4 of (M,M)-(E)-8 have the character
of exciton coupling, where intense rotational strengths but of
opposite sign are accompanied. The dipole strength of transition
number 3 at longer wavelength side is weaker than that of
transition number 4 in (M,M)-(E)-8. These characteristic
patterns are also observed in the transitions numbers 3 and 4 of
olefin (M,M)-(E)-1. Therefore, it is interpreted that the observed
Cotton effects of [CD(+)238.5]-(E)-1 in the 1Bb transition region
are keeping the nature of the exciton coupling between the long
axis polarized transition moments of two naphthalene chro-
mophores.
Theoretical Determination of the Absolute Stereochem-
istry of cis-Olefin [CD(+)238.1]-(Z)-2. The UV spectrum of
(M,M)-(Z)-enantiomer 2 was also reproduced by the calcula-
tion: calculated, λmax 329.0 nm (ꢀ 6 400) and 211.9 (57 600);
observed, λmax 329.3 nm (ꢀ 7 800)sh, 301.9 (11 300), and 223.0
(73 700) (Figure 6 and Table 1). Unlike trans-olefin 1, the
calculated 1La band appeared in a longer wavelength region than
the observed one. The CD spectrum of (M,M)-(Z)-enantiomer
2 was also calculated by the π-electron SCF-CI-DV MO
method: calculated, λext 331.1 nm (∆ꢀ -48.8), 260.4 (-12.8),
232.6 (+76.7), and 215.5 (-158.8); observed, λext 339.0 nm
(∆ꢀ -12.3), 303.8 (-8.4), 281.5 (+8.5), 256.0 (-63.2), 238.1
(+189.7), and 223.5 (-239.3) (Table 1). Although the shape
of the calculated CD curve in the 1La transition region is much

Chemistry of Unique Chiral Olefins. 1
J. Am. Chem. Soc., Vol. 119, No. 31, 1997 7247
a Jeol JNM-LA600 (600 MHz) spectrometer. 13C NMR spectra were
obtained on a Jeol JNM-LA400 (100 MHz) spectrometer. All NMR
data are reported in ppm (δ) downfield from tetramethylsilane, and
the NMR data of C2-symmetrical compounds are listed for a half
molecule. Optical rotations [R]D were measured on a Jasco DIP-1000
spectropolarimeter. UV and CD spectra were recorded on Jasco Ubest-
50 and Jasco J-400X or J-720WI spectrometers, respectively. MS
spectra were obtained with a Jeol JMS DX-300/JMA-3100/3500
spectrometer by the electron ionization (EI) procedure (70 eV), unless
otherwise noted. X-ray single-crystal diffraction measurement was
performed on a Rigaku AFC-6B automated four-circle diffractometer.
1
The purities of the title compounds were shown to be g95% by H
NMR, TLC, HPLC, and/or elemental analysis.
(()-(E)-1,1′,2,2′,3,3′,4,4′-Octahydro-4,4′-biphenanthrylidene (1)
and Its cis-Isomer (()-(Z)-(2). To a mixture of TiCl3 (7.15 g, 45.9
mmol) and dry tetrahydrofuran (THF, 15 mL) cooled at 0 °C was added
dropwise a mixture of LiAlH4 (0.87 g, 23.0 mmol) and dry THF (10
mL) under a stream of argon gas, and the reaction mixture was stirred
for 10 min. To the reaction mixture was added a solution of ketone 7
(3.0 g, 15.3 mmol) in dry THF (20 mL), and the reaction mixture was
gently refluxed overnight. THF was removed under a reduced pressure,
and the residue was extracted with ethyl acetate three times. The
organic layer was washed with brine, dried with anhydrous MgSO4,
and evaporated to dryness. After the crude product obtained was
purified by a short column chromatography on silica gel (benzene),
the hydrocarbon fractions were further purified by repeating HPLC on
silica gel (hexane/benzene 10:1) several times. From the less-polar
fraction, trans-olefin (()-1 was obtained as a crystalline material, which
was recrystallized from hexane giving colorless crystals (0.228 g,
8.3%): mp 213 °C; TLC (silica gel, hexane/benzene 10:1) Rf 0.61; IR
(KBr) νmax 3054, 2958, 2848, 1591, 1509, 1441, 1384, 1297, 1210,
1026, 958, 867, 815, 751 cm-1; 1H NMR (600 MHz, CDCl3) δ 1.50 (1
H, dddt, J ) 12.7, 10.1, 7.1, 5.1 Hz, H2ax), 1.74 (1 H, dddt, J ) 12.7,
7.1, 5.8, 4.0 Hz, H2eq), 2.23 (2 H, t, J ) 7.1 Hz, H3), 2.59 (1 H, ddd,
J ) 14.7, 10.1, 5.8 Hz, H1ax), 2.75 (1 H, ddd, J ) 14.7, 5.1, 4.0 Hz,
H1eq), 7.36 (1 H, d, J ) 8.2 Hz, H10), 7.46 (1 H, ddd, J ) 8.2, 6.7,
1.3 Hz, H7), 7.52 (1 H, ddd, J ) 8.4, 6.7, 1.1 Hz, H6), 7.77 (1 H, d,
J ) 8.2 Hz, H9), 7.89 (1 H, dd, J ) 8.2, 1.3 Hz, H8), 8.28 (1 H, dd,
J ) 8.4, 1.1 Hz, H5); 13C NMR (100 MHz, CDCl3) δ 22.8 (C2), 29.8
(C1), 30.2 (C3), 124.5 (C7), 125.9 (C6), 126.0 (C5), 126.3 (C10), 126.9
(C9), 128.5 (C8), 131.0 (C4b), 132.0 (C4), 132.4 (C8a), 135.6 (C4a),
Figure 6. CD and UV spectral curves of cis-olefin (M,M)-(Z)-2
calculated by the π-electron SCF-CI-DV MO method.
different from the observed one, the negative sign of the Cotton
effect around 330 nm agrees with that of observed one. The
intense positive and negative Cotton effects in the 1Bb transition
region were also reproduced by the π-electron SCF-CI-DV MO
calculations, although the CD ∆ꢀ values are still much different
from those of observed ones. Since the principal Cotton effects
of the calculated and observed CD spectra thus agree with each
other, the absolute stereochemistry of the first-eluted cis-olefin
[CD(+)238.1]-(Z)-2 was also nonempirically determined to be
(M,M) by the theoretical calculation of its CD spectrum.
The mechanism of the intense CD Cotton effects of cis-olefin
[CD(+)238.1]-(Z)-2 in the 1Bb transition region was also
clarified by the calculation of the hypothetical model compound
(M,M)-(Z)-9 as for [CD(+)239.0]-(E)-1 (Chart 2). The calcula-
tion gave intense positive first and negative second Cotton
effects due to the exciton coupling between two naphthalene
chromophores in the 1Bb transition region (Table 1). The nature
of the exciton coupling seen in the transitions of numbers 3
and 4 of model compound (M,M)-(Z)-9 is retained in the
transitions of numbers 7 and 9 of cis-olefin (M,M)-(Z)-2 (Table
2). Therefore, the observed Cotton effects of [CD(+)238.1]-
1
138.8 (C10a); H-1H NOESY and HMBC (600 MHz, CDCl3), see
tables in Supporting Information; HSQC (600 MHz, CDCl3) H1ax-
C1, H1eq-C1, H2ax-C2, H2eq-C2, H3-C3, H5-C5, H6-C6, H7-
C7, H8-C8, H9-C9, H10-C10; UV (MeOH) λmax 316.0 nm (ꢀ
16 900), 231.5 (62 500), 215.7 (84 300); MS m/z 360 (parent). Anal.
Calcd for C28H24: C, 93.29; H, 6.71. Found: C, 93.22; H, 6.76.
From the more polar fraction, cis-olefin (()-2 was obtained as a
crystalline material, which was recrystallized from hexane giving
colorless crystals (0.069 g, 2.5%): mp 192-195 °C; TLC (silica gel,
hexane/benzene 10:1) Rf 0.56; IR (KBr) νmax 3049, 2949, 2887, 1595,
1
1509, 1430, 1377, 1235, 1025, 845, 813, 749 cm-1; H NMR (600
MHz, CDCl3) δ 1.67 (1 H, ddddd, J ) 15.4, 11.4, 8.6, 8.4, 4.3 Hz,
H2ax), 2.31 (1 H, ddddd, J ) 15.4, 8.4, 5.0, 4.3, 3.5 Hz, H2eq), 2.65
(1 H, ddd, J ) 14.7, 8.6, 3.5 Hz, H3ax), 2.90 (1 H, ddd, J ) 14.7,
11.4, 5.0 Hz, H1ax), 2.96 (1 H, ddd, J ) 14.7, 4.3, 4.3 Hz, H1eq),
3.18 (1 H, ddd, J ) 14.7, 8.4, 8.4 Hz, H3eq), 6.65 (1 H, ddd, J ) 8.4,
6.8, 1.3 Hz, H6), 6.83 (1 H, ddd, J ) 8.1, 6.8, 1.3 Hz, H7), 7.00 (1 H,
dd, J ) 8.4, 1.3 Hz, H5), 7.19 (1 H, d, J ) 8.3 Hz, H10), 7.21 (1 H,
dd, J ) 8.1, 1.3 Hz, H8), 7.26 (1 H, d, J ) 8.3 Hz, H9); 13C NMR
(100 MHz, CDCl3) δ 23.0 (C2), 28.9 (C3), 31.2 (C1), 123.4 (C7), 123.9
(C6), 124.6 (C5), 126.1 (C10), 126.4 (C9), 126.7 (C8), 129.2 (C4b),
1
(Z)-2 in the Bb transition region are considered to be mainly
arising from the exciton coupling between two naphthalene
chromophores.
The theoretical CD method is thus powerful for determination
of the absolute stereochemistry of chiral compounds with a
twisted π-electron system. The absolute stereochemistry of
chiral olefins 1 and 2 theoretically determined was later
experimentally proved by the X-ray crystallographic analysis
of their derivatives as described in the third paper of this series.28
1
131.4 (C4), 131.9 (C8a), 135.8 (C4a), 138.8 (C10a); H-1H NOESY
and HMBC (600 MHz, CDCl3), see tables in Supporting Information;
HSQC (600 MHz, CDCl3) H1ax-C1, H1eq-C1, H2ax-C2, H2eq-
C2, H3ax-C3, H3eq-C3, H5-C5, H6-C6, H7-C7, H8-C8, H9-
C9, H10-C10; UV (hexane) λmax 301.9 nm (ꢀ 11 300), 222.8 (71 900);
MS m/z 360 (parent). Anal. Calcd for C28H24: C, 93.29; H, 6.71.
Found: C, 93.24; H, 6.86.
Experimental Section
General Procedures. Melting points are uncorrected. IR spectra
were obtained as KBr disks on a Jasco FT/IR-8300 spectrophotometer.
1H NMR spectra were recorded on a Jeol JNM-LA400 (400 MHz) or
X-ray Crystallography of (()-(E)-Olefin (1). Crystals were
obtained as colorless prisms by crystallization from hexane: mp 213
°C. A single crystal (dimensions of 0.36 × 0.23 × 0.22 mm) was

7248 J. Am. Chem. Soc., Vol. 119, No. 31, 1997
Harada et al.
selected for data collection and mounted on a Rigaku AFC-6B
automated four-circle diffractometer. The crystal was found to be
monoclinic, and the unit cell parameters and orientation matrix were
obtained. Data collection was carried out by using a 2θ - θ scan:
formula, C28H24; Mr ) 360.50; space group C2/c (No. 15); a )
19.188(2), b ) 6.6750(4), and c ) 15.337(2) Å, â ) 90.35(1)°; V )
1964.4(3) Å3; Z ) 4; Dx ) 1.219 g cm-3; Dm ) 1.211 g cm-3 by
flotation using a CCl4/hexane solution; radiation, Cu KR (1.541 78 Å);
monochromator, graphite crystal; linear absorption coefficient, 4.43
cm-1; temperature, 20 °C; scan speed, 2.0°/min; scan range, 1.3° +
0.3° tan θ; 2θ scan limits, 2° - 130°; standard reflections, 3 per 50
reflections; indices, (1,1,3), (1,1,0), (3,1,1); crystal stability, no indica-
tion of standard reflection decay during data collection; total reflections
scanned, 3780; unique data Fo > 3σ(Fo), 1544. One asymmetrical unit
contained a half molecule of 1. The skeletal structure was solved by
direct methods and successive Fourier syntheses. All hydrogen atoms
were found by the difference Fourier syntheses. Full-matrix least-
squares refinement of positional and thermal parameters led to the final
convergence with R ) 0.0688 and Rw ) 0.0577.
Enantioresolution of (()-(E)-Olefin 1 by HPLC. The HPLC
column with a chiral stationary phase of (+)-poly(triphenylmethyl
methacrylate) (Chiralpak OT(+) from Daicel Co. Ltd.) was installed
in a HPLC system, cooled at 3 °C by circulating cold methanol in a
column jacket, and equilibrated with methanol as eluent. The sample
of (()-trans-1 was injected as a methanol solution, and the separation
of enantiomers was monitored by a UV detector. Since a small amount
of the polymer of the chiral stationary phase was present as a
contaminant, the fraction of each enantiomer resolved was purified by
HPLC (ODS-C18, MeOH). From the first eluted fraction, chiral olefin
[CD(+)239.0]-(E)-1 was obtained; the 1H NMR data of optically active
1 were identical with those of (()-1: CD (MeOH), see Table 1, where
the concentration of the sample was determined from the UV absorption
intensity. From the second-eluted fraction, chiral olefin [CD(-)239.0]-
(E)-1 was obtained, and its CD Cotton effects were opposite in sign
but almost equal in intensity to those of [CD(+)239.0]-(E)-1.
methacrylate) connected in series with a short HPLC column of silica
gel was installed in a HPLC system, cooled at 3 °C by circulating cold
methanol, and equilibrated with hexane as eluent. The sample of (()-
cis-2 was injected as a hexane solution, and the separation of
enantiomers was monitored by a UV detector. The first-eluted fraction
was collected and recycled five times. After separation, the CD
spectrum of the first-eluted fraction was immediately measured: CD
(MeOH), see Table 1, where the concentration of the sample was
determined from the UV absorption intensity. Since the 1H NMR data
of optically active 2 thus separated were identical with those of (()-2,
the enantiomer of the first-eluted fraction was defined as [CD(+)238.1]-
(Z)-2. The CD spectrum of the second-eluted fraction was measured,
and its CD Cotton effects observed were opposite in sign to those of
the first-eluted enantiomer, although its CD Cotton effects were
considerably weak. The second-eluted enantiomer was thus designated
as [CD(-)238.1]-(Z)-2.
Acknowledgment. This work was supported in part by
grants from the Ministry of Education, Science, Sports, and
Culture, Japan (General (A) No. 07408032, General (B) No.
01470026, Priority Areas Nos. 02250103, 03236101, 04220101,
and 06240204, Developmental Research No. 05554017, and
International Joint Research No. 02044014 to N.H.). Part of
this research (B.d.L., W.F.J., B.L.F) was supported by the
Stichting Technische Wetenschappen (STW) and the Dutch
Foundation for Scientific Research (NWO).
Supporting Information Available: Experimental proce-
dures for the synthesis of 5a, 6, and 7, as well as their
spectroscopic and physical data, NOESY and HMBC data of
(E)-1 and (Z)-2, HPLC figure for enantioresolution of (E)-1 and
(Z)-2, and calculated CD and UV spectral curves of (M,M)-
(E)-8 and (M,M)-(Z)-9 (7 pages). See any current masthead
page for ordering and Internet access instructions.
Enantioresolution of (()-(Z)-Olefin 2 by HPLC. The HPLC
column with a chiral stationary phase of (+)-poly(triphenylmethyl
JA970667U