Positive Cotton Effect Research Articles

Preparation and properties of optically active polyurethane/TiO 2 nanocomposites derived from optically pure 1,1′-binaphthyl

In this study, optically active polyurethanes (PU) were prepared from chiral 1,1′-binaphthyl (BINOL) and 2,4-toluene diisocyanate (TDI) by the simple hydrogen transfer addition reaction and the high-intensity ultrasonic was applied to the preparation of polyurethane/TiO 2 nanocomposites. The ( R)-BPU and ( S)-BPU were analyzed by 1H NMR, FT-IR spectroscopy, thermogravimetric analysis (TGA), UV–vis spectroscopy and circular dichroism (CD) spectra. The results indicated that the polymers exhibited stronger CD signals with positive and negative Cotton effect in their CD spectra. Meanwhile, the nanocomposites were characterized by IR, powder X-ray diffraction, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results manifested the improvement of heat stability of the nanocomposites with the presence of TiO 2 nanoparticles. As a result, the infrared emissivity (8–14 μm) study revealed that the nanocomposites possessed much lower infrared values compared with those of the neat polymers and nanoparticles, respectively.

Optical Band Splitting and Electronic Perturbations of the Heme Chromophore in Cytochrome c at Room Temperature Probed by Visible Electronic Circular Dichroism Spectroscopy

We have measured the electronic circular dichroism (ECD) of the ferri- and ferro-states of several natural cytochrome c derivatives (horse heart, chicken, bovine, and yeast) and the Y67F mutant of yeast in the region between 300 and 750 nm. Thus, we recorded the ECD of the B- and Q-band region as well as the charge-transfer band at ∼695 nm. The B-band region of the ferri-state displays a nearly symmetric couplet at the B 0-position that overlaps with a couplet 790 cm −1 higher in energy, which we assigned to a vibronic side-band transition. For the ferro-state, the couplet is greatly reduced, but still detectable. The B-band region is dominated by a positive Cotton effect at energies lower than B 0 that is attributed to a magnetically allowed iron→heme charge-transfer transition as earlier observed for nitrosyl myoglobin and hemoglobin. The Q-band region of the ferri-state is poorly resolved, but displays a pronounced positive signal at higher wavenumbers. This must result from a magnetically allowed transition, possibly from the methionine ligand to the d xy-hole of Fe 3+. For the ferro-state, the spectra resolve the vibronic structure of the Q v-band. A more detailed spectral analysis reveals that the positively biased spectrum can be understood as a superposition of asymmetric couplets of split Q 0 and Q v-states. Substantial qualitative and quantitative differences between the respective B-state and Q-state ECD spectra of yeast and horse heart cytochrome c can clearly be attributed to the reduced band splitting in the former, which results from a less heterogeneous internal electric field. Finally, we investigated the charge-transfer band at 695 nm in the ferri-state spectrum and found that it is composed of at least three bands, which are assignable to different taxonomic substates. The respective subbands differ somewhat with respect to their Kuhn anisotropy ratio and their intensity ratios are different for horse and yeast cytochrome c. Our data therefore suggests different substate populations for these proteins, which is most likely assignable to a structural heterogeneity of the distal Fe-M80 coordination of the heme chromophore.

Synthesis and characterization of chiral polymer complexes incorporating polybinaphthyls, bipyridine, and Eu(III)

AbstractChiral conjugated polymers P‐1 and P‐2 were synthesized by the polymerization of (S)‐3,3′‐diiodo‐2,2′‐bisbutoxy‐1,1′‐binaphthyl and (S)‐6,6′‐dibromo‐2,2′‐bisbutoxy‐1,1′‐binaphthyl, respectively, with 5,5′‐divinyl‐2,2′‐bipyridine through a Heck cross‐coupling reaction. Chiral polymer complexes P‐C‐1 and P‐C‐2 were obtained by the bipyridine chelating coordination of P‐1 and P‐2 with Eu(TTA)3·2H2O (where TTA is 2‐thenoyltrifluoroacetonate). Polymers P‐1 and P‐2 and polymer complexes P‐C‐1 and P‐C‐2 exhibited intense circular dichroism signals, with negative and positive Cotton effects in their circular dichroism spectra. The chiral polymers showed strong green‐blue fluorescence because of the efficient energy migration from the extended π‐electronic structure of the conjugated polymer main to the chiral binaphthyl core. The chiral polymer complexes could have not only polymer fluorescence but also the characteristic fluorescence of Eu(III) (5D0→7F2) at a different excited wavelength. These kinds of chiral polymer complexes incorporating polybinaphthyls, bipyridine, and Eu(III) moieties are expected to provide an understanding of the relationship between the structure and properties of chiral polymer complexes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 650–660, 2007

Chiral Aggregates Formed from Methylated Tetraenoic Fatty Acids: Formation of Both Antipodes of Chiral Aggregates from a Single Enantiomer and Time-Dependent Stereomutation

Formation and behaviors of chiral aggregates of methylated tetraenoic fatty acids (TE-FAs) were reported. In the C-24 TE-FA series, the aggregate prepared by dispersing an ethanol stock solution of C-24 TE-FA 1b into sodium phosphate buffer gave a strong positive Cotton effect, whereas the aggregate prepared from a methanol stock solution gave a negative Cotton effect. In the C-20 TE-FA series, the aggregate prepared from an ethanol stock solution of C-20 TE-FA 2b exhibited time-dependent chirality inversion. [see text].

Enantioselective Synthesis of 3‐Methylisochromans and Determination of Their Absolute Configurations by Circular Dichroism

AbstractSeven (S)‐3‐methylisochromans with different substitution patterns on their aromatic rings, and hence with different directions of their sum electric transition moments, were synthesized by ring‐closure of optically active (S)‐1‐arylpropan‐2‐ol derivatives. The (S)‐1‐arylpropan‐2‐ols were obtained by kinetic resolution and their absolute configurations were determined with the aid of a zinc porphyrin tweezer and by Mosher’s method. A systematic CD study of substituted isochroman derivatives revealed that, unlike in the cases of chiral tetralin and 2,3‐dihydrobenzo[b]furan chromophores, the presence of achiral substituents of large spectroscopic moment (e.g., OMe) on the aromatic ring does not change the helicity rule of the “unsubstituted” isochroman chromophore: (P)/(M) helicity of the isochroman heteroring resulted in positive/negative 1Lb band Cotton effects (CE) regardless of the nature(s) and position(s) of the substituent(s). (S)‐3‐Methylisochromans were oxidized at C‐1, allowing access to the corresponding dihydroisocoumarins, in which positive CE of the n→π* transitions were correlated with (P) helicity and (S) absolute configuration. On DDQ‐assisted oxidation, two trans‐1‐methoxy‐3‐methylisochroman derivatives were prepared and used to study the effect of the axial benzylic C‐1 methoxy group on the conformation of the heteroring and the 1Lb band CE. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Interactions of human serum albumin with retinoic acid, retinal and retinyl acetate

Human serum albumin (HSA), a major plasma protein and plasma-derived therapeutic, interacts with a wide variety of drugs and native plasma metabolites. In this study the interactions between HSA and small lipophilic molecules all- trans retinoic acid (RA), all- trans retinaldehyde (retinal, RAL) and all- trans retinyl acetate (RAC) were investigated by UV–vis absorption spectroscopy, fluorescence spectroscopy and circular dichroism (CD). This paper focuses on investigation of the interactions between HSA and RA by the visible CD. RAL and RAC were used in this study due to their structural identity to RA to elucidate the importance of the end functional group for the complex formation. Our data demonstrate that RA specifically binds to HSA in a stable non-covalent complex at least at two internal binding sites with close but distinct affinities. Upon titration of HSA with RA, visible CD spectra clearly demonstrate the appearance of a well-defined induced positive Cotton Effect (CE) around 350 nm. Beyond ligand-to-protein ratio of 0.8 and up to saturation (2.0), CD exhibits two major bands of opposite signs, suggesting exciton coupling between the chromophore molecules in the protein interior. The fluorescence quenching data suggest proximity of the primary RA binding site to tryptophan (W 214). RAC shows a weak association with HSA with stoichiometry close to that of RA, while interactions of RAL with HSA proceed non-specifically at multiple sites. Contrary to RA, the adducts of HSA with RAC and RAL do not show any induced chirality, thus indicating that despite their high structural similarity to RA, both compounds do not appear to occupy the internal binding sites, but associate with the protein exterior.

Resolution, Enantiomerization Kinetics, and Chiroptical Properties of 7,7‘-Dihydroxy-8,8‘-biquinolyl

(+/-)-7,7'-Dihydroxy-8,8'-biquinolyl (6) was resolved into its enantiomorphic atropisomers via reverse phase (C18) chromatographic separation of epimeric bismenthyl carbonates, (-)-lk-9 and (+)-ul-9, derived from 6 and (+)-menthyl chloroformate. The faster eluting diastereoisomer, (-)-lk-9, was revealed to possess an (aS)-configurated biaryl axis by X-ray crystallographic analysis. Saponification of the separated bismenthyl carbonates gave enantioenriched samples of biquinolyl 6, and absolute stereochemical configurations were assigned to the two optical isomers as (-)-(aS)-6 and (+)-(aR)-6 by correlation with their respective progenitors, (-)-lk-9 and (+)-ul-9. First-order rate constants for the enantiomerization of 6 in water were obtained over the temperature range 316-366 K, and activation parameters were determined as DeltaH(++) = 34.0 kcal mol(-1) and DeltaS(++) = 18.7 cal mol(-1) K(-1) by Eyring plot analysis. A low level (AM1) computational study of the rotational dynamics of 6 showed excellent agreement with kinetic experimental data and suggested that enantiomerization occurs preferentially via a syn pathway. In common with (-)-(aS)-1,1'-bi-2-naphthol (BINOL), (-)-(aS)-6 showed positive exciton chirality in its electronic circular dichroism (CD) spectrum and gave a characteristic couplet composed of a positive maximum Cotton effect at 250 nm and a negative minimum at 234 nm (Delta Delta epsilon = +40 M(-1) cm(-1) at 64% ee).

Helicity discrimination in diselenides by chiral substituents—a circular dichroism study

Diselenides substituted with chiral alkyl groups exhibit, in solution and in the crystal form, Cotton effects within the diselenide chromophore absorption region. The origin is traced to steric effects, leading to a non-uniform distribution of diastereomeric P and M forms of the diselenide chromophore. A DFT computational model presented herein allows us to predict the preferred helicity of the diselenide chromophore from the sign of the experimental n–σ ∗ Cotton effect, that is, a positive long-wavelength Cotton effect is due to a P conformer and a negative Cotton effect corresponds to an M conformer.

A High-Spin and Helical Organic Polymer: Poly{[4-(dianisylaminium)phenyl]acetylene}

A high-spin polyradical, poly{[4-(dianisylaminium)phenyl]acetylene} 1+, was synthesized as a π-conjugated polymer with an excess of the one-handed helical structure bearing stable aminium cation radicals. [4-(Dianisylamino)phenyl]acetylene (3) was synthesized and polymerized using [Rh(norbornadiene)Cl]2 in (R)-1-phenylethylamine, (S)-1-phenylethylamine, or triethylamine to produce the corresponding poly{[4-(dianisylamino)phenyl]acetylene} 1 (1(R)-PEA, 1(S)-PEA, and 1TEA). The positive and negative Cotton effects were observed at 270−450 nm for the polymers 1(R)-PEA and 1(S)-PEA, indicating that an excess of the one-handed helical polyacetylene backbone was induced by the polymerization using chiral solvents despite the achiral monomer. The oxidation of 1 with NOPF6 gave the corresponding aminium polyradicals 1+, and the circular dichroism (CD) spectrum was observed even after the oxidation of the helical polyradical 1(R)-PEA+. The SQUID and NMR shift measurements indicated a high-spin state of the polyrad...

Synthesis and characterization of chiral nickel(II) Schiff base complexes and their CD spectra-absolute configuration correlations

Some nickel(II) complexes of quadridentate Schiff bases prepared from the condensation of 2 mol of 2-hydroxyacetophenone (HACP) or dehydroacetic acid (DHA) with 1 mol of optically active propylene-1,2-diamine (pn), trans-cyclohexane-1,2-diamine (chxn) or 1,2-diphenylethylenediamine (dpen) were synthesized and characterized by EA, IR, UV–vis, and CD spectra. The absolute configurations of the three complexes were determined by X-ray single crystal structure measurement and correlated with CD spectroscopy. In this study, special attention is focussed on the CD signals of the related complexes in the d–d transition region, in the hope of obtaining a tentative correlation between the CD pattern and the absolute configuration about the central metal. A new empirical rule for the assignment of the absolute configuration around the nickel ion in each complex and the handedness of the chiral diamine contained in the Schiff base ligand is put forward. In the case of tetra-coordinated pseudo-planar Ni(II) complexes, the rule can be stated as follows: (i) a positive Cotton effect in the d–d region around 550 nm is assigned to the ( S)Δ λ-configuration for the HACP-( S)-pn-Ni, HACP-( SS)-dpen-Ni, DHA- S-pn-Ni, and DHA-( SS)-dpen-Ni derivatives; and (ii) a concomitant inversion of the Cotton effect in the same range is assigned to the ( S)Λ δ-configuration for the HACP-( SS)-chxn-Ni and DHA-( SS)-chxn-Ni derivatives.

Efficient Synthesis of a Chiral [4]Pseudocatenane and Its Derivatives: A Novel Ship's Wheel‐like Interlocked Structure

A novel chiral[4]pseudocatenane 5H(3)[PF(6)](3) was synthesized efficiently by treatment of a solution of chiral triptycene-based tri(crown ether) 1 and three equivalents of a bis[p-(but-3-enyloxy)benzyl]ammonium salt in CH(2)Cl(2) with a Grubbs II catalyst, followed by hydrogenation. It was found that the ammonium groups in 5H(3)[PF(6)](3) could be deprotonated by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in acetonitrile or dimethyl sulfoxide (DMSO). Consequently, N-acylation of the ammonium groups was easily performed in the presence of DBU, which resulted in a new class of neutral highly ordered interlocked molecules in good yields. In particular, the incorporation of stopper units, for example, diethyl phosphoramidate, lead to the isolation of the interlocked molecule 10 with an interesting ship's wheel-like structure, which was structurally studied with the help of detailed NMR experiments. Compared with 1, it was further found that the Cotton effect of (R)-1,1'-binaphthyl chromophore at 241 nm was greatly reduced in 5H(3)[PF(6)](3) and its derivatives. Moreover, a new positive Cotton effect at 248 nm appeared in the interlocked molecules; this observation could be attributed to the chirality transfer from the binaphthyl units to the macrocycles lying in the cavities of 1.

Chiral discrimination of a helically organized crown ether array parallel to the helix axis of polyisocyanate

AbstractThe asymmetric polymerization of 4′‐isocyanatobenzo‐18‐crown‐6 with the lithium amide of (S)‐(2‐methoxymethyl)pyrrolidine successfully proceeded to afford end‐functionalized poly(4′‐isocyanatobenzo‐18‐crown‐6) with (S)‐(2‐methoxymethyl)pyrrolidine (polymer 2). In the circular dichroism (CD) spectrum of 2, a clear positive Cotton effect was observed in the range of 240–350 nm corresponding to the absorption of the polymer backbone, indicating that 2 partially formed a one‐handed helical structure, which was preserved by the chirality of (S)‐(2‐methoxymethyl)pyrrolidine bonding to the terminal end in 2. In the titration experiments for the CD intensity of 2 in the presence of D‐ and L‐Phe·HClO4 (where Phe is phenylalanine), a small but remarkable difference was observed in the amount of the chiral guest needed for saturation of the CD intensity and in the saturated CD intensity, indicating that the extremely stable, one‐handed helical part should exist in the main chain of 2, which was not inverted even when the unfavorable chiral guest for the predominant helical sense, L‐Phe·HClO4, was added. In addition, helical polymer 2 exhibited a chiral discrimination ability toward racemic guests; that is, the guests were extracted from the aqueous phase into the organic phase with enantiomeric excess. The driving force of the chiral discrimination ability of 2 should certainly be attributed to the one‐handed helical structure in 2. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 325–334, 2006

Synthesis of optically active regioregular poly(thiophene)

A regioregular polythiophene bearing an optically active substituent at the 3-position of thiophene ring, Head-to-Tail poly(3-[2-(( S)-1-methyloctyloxy)ethyl]thiophene) ( HT-P( S)MOET), was synthesized using highly reactive zinc. HT-P( S)MOET had more than 95% Head-to-Tail coupling with a Mw of 3.72 × 10 4 (Mw/Mn = 1.20) as estimated by 1H-NMR spectroscopy and gel permeation chromatography. HT-P( S)MOET had strong negative Cotton effect at about 560 and 610 nm and positive Cotton effect at about 490 nm. The presence of circular dichroism effect shows that the chirality of side chains induces the optical activity in poly(thiophene) main chains. The Langmuir-Blodgett films of HT-P( S)MOET exhibited well-defined layer structure and unique optical properties.

Formation of an Inclusion Complex of a New Transition Metal Ligand in β-Cyclodextrin

The inclusion complex of a new transition metal ligand, 2,4,9-trithia-tricyclo[3.3.1.13,7]decane-7-carboxylic acid (2,4,9-trithia-adamantane-7-carboxylic acid, TPCOOH) in β-cyclodextrin was studied by 1H NMR, 2D NOESY NMR spectroscopy, host-induced CD spectroscopy, and tandem mass spectrometry. 1H NMR, MS–MS and NOESY data show that the TPCOOH guest forms a 1:1 inclusion complex with the host β-cyclodextrin. The NOESY experiments also show that TPCOOH is oriented in the complex with the thioketal end preferentially located at the larger opening of β-cyclodextrin. The orientation of the guest in the host molecule is also confirmed by the induced CD of the ligand, which shows a positive Cotton effect. An association constant of 660±20 M−1 was determined by 1H NMR titration for the complex at room temperature in D2O.

A general CD-method for the configurational assignment of erythro-8.4'-oxyneolign-8'-enes

Resolution of erythro-7-hydroxy-3′,5′-dimethoxy-3,4-methylenedioxy-8.4′-oxyneolign-8′-ene 1c was achieved by preparing the diastereomeric esters with (–)-(R)-α-methoxyphenylacetic acid. The correlation of its CD properties with the absolute configuration established a general CD method for the configurational assignment of erythro-8.4′-oxyneolignenes: positive Cotton effects of the two low-energy CD transitions derive from 7R,8S configuration while the negative ones from 7S,8R. This rule allows the configurational assignment of erythro-8.4′-oxyneolignenes with different aromatic substitution pattern by a CD measurement.

Optical activity of the guest azobenzene molecule generated by inclusion complexation with steroidal bile acids

The crystalline inclusion complexes of azobenzene 1 with cholic CA and deoxycholic DCA acid were prepared and their solid state CD spectra measured. The positive Cotton effect sign, corresponding to the lowest energy n–π* transition, was correlated with the M, M helicity of the twisted guest molecule. The absolute sense of twist of the enclathrated guest molecule 1 was deduced from the X-ray structure of the 1· CA complex. In addition, the solid state CD spectrum of the enantiomorphous crystals of methyl yellow 2 was measured. The source of the optical activity is a slight twisting of the constituent molecules and their helical arrangement in the crystal.

Helicity Induction of Polyisocyanate with a Crown Cavity on the Main Chain Synthesized by Cyclopolymerization of α,ω-Diisocyanate

Polymerization of a novel α,ω-diisocyanate monomer, 1,14-bis(4-isocyanatophenoxy)-3,6,9,12-tetraoxatetradecane (1), was carried out in DMF using MeLi to afford a gel-free linear polymer according to a cyclopolymerization mechanism. The resulting polymer was assignable to poly(phenyl isocyanate) with a C2 symmetrical crown cavity on the main chain (2). The circular dichroism (CD) spectrum of 2 in the presence of the perchloric acid salt of l-phenylglycine (l-Pgly·HClO4) showed a negative Cotton effect with a high intensity of −3.2 × 104 deg cm2 dmol-1 in the range from 245 to 330 nm, corresponding to the absorption of the polymer backbone, while a positive Cotton effect was observed for d-Pgly·HClO4, and the CD spectrum pattern was a mirror image of that of 2 with l-Pgly·HClO4. Thus, this suggested that the novel type of poly(phenyl isocyanate) with the crown cavity on the main chain (2) formed a one-handed helical structure driven by the host−guest complexation with the chiral guest molecules. Although the solvent significantly influenced the CD intensities of 2, the CD intensities hardly changed at any temperature.

Chiroptical analysis of marine sponge alkaloids sharing the pyrrolopyrazinone core.

A systematic experimental study has been conducted on the chiroptical properties of bi- and tricyclic pyrrolopyrazinones, which occur as the core in a variety of marine pyrrole-imidazole alkaloids, such as the immunosuppressive palau'amine. On the basis of the chiral-pool synthesis of conformationally fixed dipyrrolopyrazinones, it was possible to predict the CD spectrum of (-)-dibromophakellin above 240 nm. 2,2,2-Trifluoroethanol was identified as a superior solvent for this analysis. Positive Cotton effects at 250 nm can be used to determine the helicity of dibrominated pyrrolopyrazinones, while the intensity of the Cotton effect at 285 nm is governed by the relative stereochemistry. The influence of bromination of the pyrrole ring also becomes predictable. One of the tricycles can be considered as "conformationally frozen longamide A". Our study also gives the first comparative Röntgen analyses of diastereomeric Mosher esters of N,O-hemiacetals, with the results underlining the fact that caution is advised in the application of the advanced Mosher method.

Transfer of chirality by dithiophosphate ligands and chiral discrimination in the stereoselective formation of square-planar Ni(II) complexes.

In the formation reaction of Ni(2+) with the chiral racemic ligand, (R)(R)bdtp(-)/(S)(S)bdtp(-), bdtp(-) = [SSPOCH)CH(3))CH(CH(3))O](-), cyclo- O,O'-[1,2-dimethylethylene] dithiophosphato ion, the meso-complex Ni[(R)(R)(lambda)bdtp][(S)(S)(delta)-bdtp] is stereoselectively produced. The meso-complex was compared with the enantiopure crystals of (+)(589)Ni[(R)(R)(lambda)bdtp](2) or (-)(589)Ni[(S)(S)(delta)bdtp](2), as well as racemic crystals, rac-(+/-)Ni[bdtp](2), which were prepared from the solution containing the two enantiomers in a 1:1 ratio. Dissociation constants in solutions indicate different stability of the meso and enantiopure complexes depending on the solvent, whereas a more efficient crystal packing, weak H-bonding, and nonbonding interactions contribute to stabilization of the meso-species over the racemic one. Molecular structures show that the outer five-membered ligand ring adopts the half-chair conformation C(2) with either the lambda or the delta chirality and the methyl groups are in equatorial (e) positions. Enantiopure ligands of (+)(589)Ni[(R)(R)(lambda)bdtp](2) and (-)(589)Ni[(S)(S)(delta)bdtp](2) induce chirality into the symmetric SSNiSS chromophore with slightly helical distortion. Thus, their CD spectra exhibit weak negative or positive Cotton effects at 662 nm. CD spectra in L(+)- and D(-)diethyltartrate of the meso-complex and racemic crystal, rac-(+/-)Ni[bdtp](2), exhibit different weak Cotton effects of opposite sign. Complexes dissociate in methanol; rac-(+/-)Ni[bdtp](2) in methanol undergoes a crystallization-induced second-order asymmetric transformation which finally yields crystals of the meso-Ni[(R)(R)(lambda)bdtp][(S)(S)(delta)bdtp] complex.

Controlling the Helicity of Tubular J-Aggregates by Chiral Alcohols

The achiral 3,3‘-bis(3-carboxypropyl)-5,5‘,6,6‘-tetrachloro-1,1‘-dioctylbenzimidacarbocyanine dye (C8O3) self-aggregates in aqueous solution to form optically active helical J-aggregates. A three-phasic circular dichroism (CD) spectrum with positive Cotton effect at 568 nm, negative Cotton effect at 582 nm, and positive Cotton effect at 605 nm (+,−,+) is usually found and ascribed to molecular excitons. The predominance of the (+,−,+) signature means that the generation of chirality is enantioselective. The CD signal increases by a factor of about 100 when the chiral (R)-2-octanol is added to an aggregated solution, and the CD signal is further amplified by a factor of about 5 when the alcohol is present in the solvent prior to aggregation. The signature of the CD signal reverses if the enantiomeric (S)-2-octanol is used instead, and for a molar alcohol/dye ratio R of about 20, the spectra become mirror images in good approximation; i.e., the chirality of the alcohol and the CD spectra of aggregates are c...