Showing papers by "Yoshihisa Inoue published in 2000"
TL;DR: In this paper, the 1:1 inclusion complexation of 43 enantiomeric pairs of chiral guests with β-cyclodextrin at 25 °C was determined by microcalorimetry.
Abstract: The complex stability constant (K), standard free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) for the 1:1 inclusion complexation of 43 enantiomeric pairs of chiral guests with β-cyclodextrin at 25 °C have been determined by microcalorimetry. The overall complexation thermodynamics are related to variations in the structure of the cyclic and acyclic guest, including its aromatic or aliphatic nature, the chain length, branching, flexibility, charge, and incorporated oxygen atom. The differences in the thermodynamic parameters due to the chirality are comprehensively discussed in terms of the stereochemistry, skeleton, chain length, and functional groups of the guest, and the mode of penetration upon inclusion complexation. The enthalpy−entropy compensation plot, using the differential thermodynamic parameters (ΔΔH° and ΔTΔS° at 298.15 K) for the chiral recognition equilibrium, gave an excellent straight line of unit slope, from which the isokinetic, or isoenantiodifferentiating, temperature was calculat...
248 citations
105 citations
TL;DR: Interestingly, the product ee's obtained with benzoate 3a and methyl phthalate 3b are not a simple function of either temperature or solvent, but are nicely correlated with the host occupancy or the percentage of occupied host, which means that the entropy factor plays an insignificant role in this supramolecular photochirogenesis system.
Abstract: Supramolecular enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z) to the chiral (E)-isomer (1E) via inclusion and sensitization by modified alpha-, beta-, and/or gamma-cyclodextrin derivatives, possessing benzoate (2a, 3a, 4a), isomeric phthalates (3b-d), and tethered benzamide (3e) chromophores, has been investigated in aqueous methanol solutions at varying temperatures. The photostationary-state 1E/1Z ratios obtained upon sensitization with 2-4 in 1:1 water-methanol reached 0.4-0.8, which are higher than the value of ca. 0.25 reported for sensitizations by conventional alkyl benzoates in hydrocarbon solvents, although the ratio was reduced to 0.2-0.4 in water or methanol. The sensitizations of 1Z by alpha- and gamma-cyclodextrin benzoates (2a, 4a) with size-mismatched cavities gave 1E of poor enantiomeric excesses (ee's) smaller than 3 and 5%, respectively. In contrast, beta-cyclodextrin derivatives (3a-e) afforded much higher ee's of up to 24%, depending on the solvent composition. Thus, the modification of cyclodextrin with a sensitizing group successfully enhanced the product through the excited-state supramolecular interaction within the cavity. Interestingly, the product ee's obtained with benzoate 3a and methyl phthalate 3b are not a simple function of either temperature or solvent, but are nicely correlated with the host occupancy or the percentage of occupied host. This means that the entropy factor plays an insignificant role in this supramolecular photochirogenesis system, which is in sharp contrast to the decisive role of entropy in the conventional (nonsupramolecular) counterpart performed in homogeneous solutions, where an inversion of product chirality by temperature variation is reported to occur.
69 citations
TL;DR: In this paper, the effect of temperature on optical yield was investigated over a wide range, and the results showed that the enthalpy term dominated at lower temperatures, while the entropy term becomes more important above T0, switching the product chirality.
67 citations
TL;DR: In this article, the stability constants (K), standard free energies (G°), enthalpies (ΔH°), and entropy changes (TΔS°) for the complexation of γ-cyclodextrin with N-carbobenzyloxy (CBZ)-d/l-phenylalanine, CBZ-d/ l-tyrosine,CBZ-D/l -tryptophan, CBz-D, Histidine, CB Z-glycine, 3phenylpropionic acid, 4-
Abstract: The stability constants (K), standard free energies (ΔG°), enthalpies (ΔH°), and entropy changes (TΔS°) for the complexation of γ-cyclodextrin with N-carbobenzyloxy (CBZ)-d/l-phenylalanine, CBZ-d/l-tyrosine, CBZ-d/l-tryptophan, CBZ-d/l-histidine, CBZ-glycine, 3-phenylpropionic acid, 4-phenylbutyric acid, 5-phenylvaleric acid, and 6-phenylhexanoic acid have been determined in phosphate buffer solution (pH 6.9) at 298.15 K by titration microcalorimetry. The trends observed in the thermodynamic parameters for 1:1 and/or 2:1 host−guest complexation correlate with the systematic structural changes of the guest molecules. On the basis of the results obtained, we further discuss the possible thermodynamic implication for the entropic control of supramolecular systems.
49 citations
TL;DR: The role of the ligand's structure and absolute configuration in the supramolecular chirality induction in achiral bis(zinc porphyrin) has been studied and the amines with bulkier substituents resulted in stronger CD signals due to increased helical displacement in the anti conformer.
48 citations
TL;DR: A series of PRNAs were synthesized, in which the 5‘-amino-5’-deoxypyrimidine ribonucleoside moiety was appended to a mono- or oligo(γ-l-glutamic acid) backbone thro...
Abstract: The effect of adding borax and boric acids on the nucleobase orientation and recognition behavior of novel mono- and oligomeric peptide ribonucleic acids (PRNAs) has been investigated. The base orientation of 5‘-amino-5‘-deoxyuridine and 5‘-amino-5‘-deoxycytidine was shown by CD and NOE difference spectral studies to switch from anti to syn in borate buffer or upon addition of borax. The origin of this phenomenon is elucidated to be the cooperative effect of the cyclic borate esterification of the sugar's cis-2‘,3‘-diol and the hydrogen-bonding interaction between the sugar's 5‘-amino proton and the base's 2-carbonyl oxygen. Because this new strategy for switching the base orientation through the addition of borate is potentially applicable to the recognition control of nucleic acids if the sugar's 5‘-proton and cis-2‘,3‘-diol remain unmodified, we synthesized a series of PRNAs, in which the 5‘-amino-5‘-deoxypyrimidine ribonucleoside moiety was appended to a mono- or oligo(γ-l-glutamic acid) backbone thro...
48 citations
TL;DR: Thymidine and uridine, as well as calf thymus DNA, have been shown for the first time to function as chiral photosensitizers in aqueous solution, to effect the enantiodifferentiating photoisomerization of (Z)-cyclooctene, giving the chiral (E)-isomer in enantiomeric excesses of up to 15%.
Abstract: Thymidine and uridine, as well as calf thymus DNA (ctDNA), have been shown for the first time to function as chiral photosensitizers in aqueous solution, to effect the enantiodifferentiating photoisomerization of (Z)-cyclooctene, giving the chiral (E)-isomer in enantiomeric excesses of up to 15%.
34 citations
TL;DR: In this paper, the first asymmetric synthesis of ruthenium trisbipyridine derivatives starting from corresponding racemic RRThenium bis(bibyridine) complexes is described, which can be easily converted to the products with a retention of configuration at the metal center.
32 citations
TL;DR: A correlation between the conformation and chiral recognition characteristics of a series of modified amino acid complexes with β- and γ-cyclodextrins has been determined, using titration microcalorimetry and 1H NMR techniques.
31 citations
TL;DR: In this paper, the authors applied dynamic CD and 1H NMR spectroscopies for studying the phenomenon of chirality inversion in the supramolecular system consisting of bis(Zn porphyrin) and (R)-amine upon stepwise titration with (S)-amine.
Abstract: Dynamic CD and 1H NMR spectroscopies have been applied for studying the phenomenon of chirality inversion in the supramolecular system consisting of bis(Zn porphyrin) and (R)-amine upon stepwise titration with (S)-amine. The initially induced CD signals corresponding to the coupled B transitions of bis(Zn porphyrin) are gradually decreased during this process and transformed into its mirror images that are the Cotton effects with the same extrema positions, but with opposite signs. In the 1H NMR spectra of this system upon titration there is inversion of the proton signals which are in close proximity to the neighboring porphyrin plane, and are thus the most affected by its ring current effect. The observed spectral changes are caused by shifting of the equilibrium from the left- to right-handed screw in bis(Zn porphyrin) upon titration with the amine of the opposite absolute configuration. The CD and 1H NMR experiments used to determine the reaction kinetics explicitly corroborate each others results. Th...
TL;DR: A single crystal of mono(6-anilino-6-deoxy)-beta-cyclodextrin was prepared, and its crystal structure was determined by X-ray crystallographic analysis, which clearly revealed that the anilino groups are consecutively included intermolecularly into the adjacent cyclodeXTrin cavities in the crystal, thus giving rise to a consolidated column.
TL;DR: In conclusion, the inclusion complexation behavior of newly synthesized bis(β-cyclodextrin) with an oligo(ethylenediamine) tether has been investigated with representative fluorescent dyes and found to give enhanced binding and selectivity for the Cu(II)-ligated host.
TL;DR: In this paper, photosensitized cyclodimerization of (Z)-cyclohexene (1Z) was performed over a range of temperatures in the presence of chiral benzene(poly)carboxylate sensitizers, giving trans-anti-trans-, cis-trans- and cis-anti cis-[2 + 2]-cyclodimers 2−4.
Abstract: The photosensitized cyclodimerization of (Z)-cyclohexene (1Z) was performed over a range of temperatures in the presence of chiral benzene(poly)carboxylate sensitizers, giving trans-anti-trans-, cis-trans- and cis-anti-cis-[2 + 2]-cyclodimers 2–4. Of the two chiral cyclodimers (2, 3), only 2 was obtained optically active with enantiomeric excesses as high as 68.3% at −78 °C, whereas 3 was consistently racemic under various reaction conditions employed. The detailed reaction mechanism and the origin of enantiodifferentiation have been elucidated and involve the initial enantiodifferentiating photoisomerization of 1Z to the highly reactive (E)-isomer (1E) and the subsequent stereospecific concerted cyclodimerization with 1Z giving optically active 2 which is competing with the non-stereospecific stepwise cyclodimerization to racemic 2 and 3.
TL;DR: In the presence of a catalytic amount of the acid and ethanol as a nucleophile, the same compound undergoes facile transesterification upon irradiation, affording its ethyl ester in almost quantitative yield.
TL;DR: Two novel heteroatom-bridged bis(benzo-12-crown-4 ether)s have been synthesized and characterized, revealing that both disulfide and diselenide functionalities in 4 and 5 are equally effective Ag(+)-selective binding sites as the 1,7-dithia-4-oxa functionality in 6 and 7, irrespective of the different atom type.
Abstract: Two novel heteroatom-bridged bis(benzo-12-crown-4 ether)s, i.e., bis(2-nitro-4,5-(1,4,7,10-tetraoxadecamethylene)phenyl) disulfide (4) and diselenide (5), have been synthesized and characterized by elemental analysis and mass, IR, UV, and (1)H NMR spectroscopy. An X-ray crystallographic structure was obtained for 4. Ion-selective electrodes (ISE) for Ag(+), containing 4 and 5 in PVC membrane as neutral carriers, were prepared, and their selectivity coefficients for Ag(+) () were determined against other heavy metal ions, alkali and alkaline-earth metal ions, and ammonium ion using the matched potential method. These ISEs showed excellent Ag(+) selectivities, log /= -1.2). These values are comparable to those reported for the representative Ag(+)-selective thioethers 6 and 7, revealing that both disulfide and diselenide functionalities in 4 and 5 are equally effective Ag(+)-selective binding sites as the 1,7-dithia-4-oxa functionality in 6 and 7, irrespective of the different atom type and relative position of the sulfur/selenium donors in the ligands. Also discussed are the steric and electronic effects of the nitro groups in 4 and 5 on the Nernstian slopes obtained with the 4- and 5-based ISEs.
TL;DR: The detailed reaction mechanism and the origin of the enantiodifferentiation have been elucidated, and the crucial role played by the ‘microenvironmental polarity’ around the chromophore in determining the photoreactivity and the ee of the product is also discussed.
Abstract: The enantiodifferentiating photosensitized cyclodimerization of cyclohexa-1,3-diene 1 was performed over a range of temperatures in the presence of chiral arene(poly)carboxylates, giving endo- and exo-[4 + 2] cyclodimers (2a, 2b) and anti- and syn-[2 + 2] cyclodimers (3a, 3b). Among the three chiral cyclodimers (2a, 2b, 3a), only 2b was obtained as an optically active species with an enantiomeric excess (ee) of up to 8.2%. The detailed reaction mechanism and the origin of the enantiodifferentiation have been elucidated, and the crucial role played by the ‘microenvironmental polarity’ around the chromophore in determining the photoreactivity and the ee of the product is also discussed.
TL;DR: In the case of free-base and Zn porphyrin conjugates, quenching of photoexcited Ru(bpy) 3 emission and the appearance of considerable free base and free n porphrin emissions were found.
TL;DR: It is interesting to note that the simple extension of the alkyl side chains in 4 and 5 can alter the cation selectivity profiles of 1 and 3, thus exhibiting an exceptionally high La(3+)/Ce(3+) selectivity of 11.
Abstract: Three new disubstituted benzo-15-crown-5 derivatives (3-5) have been synthesized from 4',5'-bis(bromomethyl)benzo-15-crown-5 (2) and the corresponding alkanols in the presence of Na(2)S(2), and their complexation thermodynamics with light lanthanoid(III) nitrates (La-Gd) have been studied in anhydrous acetonitrile at 25 degrees C. Plots of K(S) against the reciprocal ionic diameter of lanthanoid exhibited monotonically declining pattern for the parent benzo-15-crown-5 (1) and 3 but showed a characteristic peak at Ce(3+) for 4 and 5. It is interesting to note that the simple extension of the alkyl side chains in 4 and 5 can alter the cation selectivity profiles of 1 and 3. Possessing two 2-oxapropyl groups, 3 gave a comparable K(S) for La(3+) but a significantly decreased K(S) for Ce(3+) compared with the corresponding values for 1, thus exhibiting an exceptionally high La(3+)/Ce(3+) selectivity of 11. Thermodynamically, the complexation of lanthanoid perchlorates with 1 is absolutely entropy-driven in acetonitrile, while the complexation of lanthanoid nitrates with 3-5 is primarily driven by exothermic enthalpy changes with accompanying moderate entropic gain or small entropic loss.
TL;DR: In this paper, the cyclodextrin cavity was revealed to have a stable self-inclusion complex in aqueous solution, and also the short linkage between the m-toluidino and cyclodesxtrin moieties made the ring of 2 deformed to some extent, and the complex stability constants of 1 and 2 for a series of aliphatic alcohols were determined by using spectropolarimetric titrations.
Abstract: Mono(6-anilino-6-deoxy)-β-cyclodextrin (1) and mono[6-(m-toluidino)-6-deoxy]-β-cyclodextrin (2) were synthesized and characterized. Circular dichroism and fluorescence spectral studies and fluorescence lifetime measurements have been performed to elucidate the conformations of 1 and 2 in aqueous buffer solution. 1-D and 2-D NMR spectra of 2 have been measured in D2O to deduce its structure and detailed conformation in solution. From the circular dichroism, fluorescence, and NMR spectroscopic studies, it was revealed that the substituents appended to 1 and 2 penetrate into the cyclodextrin cavity forming a stable self-inclusion complex in aqueous solution, and also that the short linkage between the m-toluidino and cyclodextrin moieties makes the cyclodextrin ring of 2 deformed to some extent. The complex stability constants (K S) of 1 and 2 for a series of aliphatic alcohols have been determined by using spectropolarimetric titrations in aqueous phosphate buffer solution (pH 7.20) at 25°C to eluc...
01 Oct 2000
TL;DR: Oligothymidine sequence is essential for efficient enantioselective photoisomerization of 1Z, giving the chiral (E)-isomer in enantiomeric excesses of up to 15%.
Abstract: DNA and RNA have been shown for the first time to function as chiral photosensitizers in aqueous solution, to effect the enantiodifferentiating photoisomerization of (Z)-cyclooctene (1Z), giving the chiral (E)-isomer in enantiomeric excesses (ee's) of up to 15%. In order to elucidate the effect of nucleotide sequence, enantiodifferentiating photoisomerization of 1Z was also performed using oligo and homopolynucleotides as chiral sensitizer. The -18.8% ee was observed by using d(T)15.d(A)15 as sensitizer, whereas sensitization by the poly(U).poly(A) duplex gave only racemic (E)-cyclooctene. From these results, oligothymidine sequence is essential for efficient enantioselective photoisomerization of 1Z.
TL;DR: In order to design functional peptides, two strategies were employed to incorporate rigid unnatural amino acids into peptides to make the peptide backbone rigid and to conjugate peptides with unnatural and inherently functional molecules.
Abstract: In order to design functional peptides, we employed two strategies. The first one is to incorporate rigid unnatural amino acids into peptides to make the peptide backbone rigid. Functions were expected to appear through the conformational control by the strategy. A series of cyclic peptides constituted of alternating natural amino acids and 3-aminobenzoic acid, used as an unnatural amino acid, were synthesized. These cyclic peptides were found to function as strong binders for phosphomonoester, catalysts for ester hydrolysis, and/or ion channels. The second strategy is to conjugate peptides with unnatural and inherently functional molecules. Following this strategy, oligo(L-leucine)- or oligo(L-phenylalanine)-modified ruthenium tris(bipyridine) complexes were synthesized. Distance dependence of the photoinduced electron transfer from the ruthenium complexes and the function as sensors for phosphate anion (H(2)PO(-)(4)) are discussed.
TL;DR: In this article, the 1 : 1 inclusion complexation of various aliphatic alcohols has been performed at 25-40 °C in aqueous solution to give the complexstability constants and the thermodynamic parameters.
Abstract: The spectrophotometric titrations have beenperformed at 25–40 °C in aqueous solution to give the complexstability constants and the thermodynamic parametersfor the stoichiometric 1 : 1 inclusion complexation ofvarious aliphatic alcohols withmono[6-(phenylseleno)-6-deoxy]-β-cyclodextrin (2),mono[6-(o-, m-,p-tolylseleno)-6-deoxy]-β-cyclodextrin (3–5),mono[6-(p-chloro-phenyl-seleno)-6-deoxy]-β-cyclodextrin(6), mono[6-(benzylseleno)-6-deoxy]-β-cyclodextrin (7) and mono[6-(naphthaleneseleno)-6-deoxy]-β-cyclodextrin(8). On thebasis of the present and previous results, themolecular binding abilities and selectivities forguest aliphatic alcohols of the host β-cyclodextrinderivatives (2–8) are discussed comparatively and globallyfrom the thermodynamic point of view. Thethermodynamic parameters obtained are criticalfunctions of the size/shape of aliphatic alcohols, andthe position and type of the substituent introduced tothe aromatic ring of β-cyclodextrin's sidearm,which are elucidatedin terms of the conformational, electrostatic,hydrogen-bonding, and hydrophobic effects.
TL;DR: In this article, the performance of cyclodextrin derivatives was investigated spectroscopically using the appended aromatic group as a spectral probe, using the spectroflurometric or spectropolarimetric titrations have been performed at 25°C in aqueous phosphate buffer solution.
Abstract: Molecular recognition behavior of eight cyclodextrin derivatives, i.e. mono(6-pyridinio-6-deoxy)-α-cyclodextrin (1α), mono(6-pyridinio-6-deoxy)-β-cyclodetrin (1β), mono(6-pyridinio-6-deoxy)-γ-cyclodextrin (1γ), mono[6-(p-picolinio)-6-deoxy]-β-cyclodextrin (2β), mono(6-anilino-6-deoxy)-β-cyclodextrin (3β), mono[6-(m-toluidino)-6-deoxy]-β-cyclodextrin (4β), mono[6-O-(8-quinolyl)]-β-cyclodextrin (5β), and novel mono[6-(2-naphthylamino)-6-deoxy]-β-cyclodextrin (6β), with a series of aliphatic alcohols and carboxylic acid has been investigated spectroscopically. Using the appended aromatic group as a spectral probe, spectroflurometric or spectropolarimetric titrations have been performed at 25°C in aqueous phosphate buffer solution (pH 7.20, 0.1 M) to determine the complex stability constants (Ks ) and Gibbs free energy changes (-δG°) for the stoichiometric 1:1 inclusion complexation of cyclodextrin derivatives with the guests. The results obtained demonstrate that the modified cyclodextrins are highl...
TL;DR: In this article, the effect of ring size on the complexation behavior of light lanthanoid(III) nitrates (La-Gd) with N-benzylaza-21-crown-7 3.
Abstract: Calorimetric titrations have been performed in anhydrous acetonitrile at 25°C to give the complex stability constants (K s) and the thermodynamic parameters (ΔGΔ, ΔHΔ and ΔSΔ) for the complexation of light lanthanoid(III) nitrates (La-Gd) with N-benzylaza-21-crown-7 3. Data analyses, assuming 1:1 stoichiometry, were successfully applied to all light lanthanoid-azacrown ether combinations employed. Using the present and previous data on 15- to 21- membered N-benzylazacrown ethers 1–3, the effect of ring size upon complexation behavior was discussed comparatively and globally from the thermodynamic point of view. The complexation behaviors are analyzed in terms of the size-fit concept, N-substituent coordination numbers, and lanthanoid's surface charge density. Thermodynamically the complexation of light lanthanoids with azacrown ethers is enthalpy-driven, while the cation selectivity is generally entropy-driven in acetonitrile.
01 Oct 2000
TL;DR: It is demonstrated that the recognition behavior ofPRNA with complementary oligopurinenucleotides can be controlled externally through the orientational switching of the pyrimidine nucleobase of PRNA induced by added borates.
Abstract: A novel nucleic acid model, i.e. peptide ribonucleic acid (PRNA), tethering 5'-amino-5'-deoxypyrimidine ribonucleoside as a recognition site for nucleic acids, has been designed and synthesized. We have demonstrated that the recognition behavior of PRNA with complementary oligopurinenucleotides can be controlled externally through the orientational switching of the pyrimidine nucleobase of PRNA induced by added borates. We extend this methodology of controlling the nucleobase orientation and recognition behavior of novel mono and oligomeric PRNAs containing 5'-amino-5'-deoxypyrimidine and/or purinenucleosides. In case of the PRNA oligomer containing pyrimidine-purine mixed sequence, efficient orientational switching of nucleobases induced by added borates was also observed.
TL;DR: In this article, two polymorphs, forms alpha and beta, were prepared and characterized by means of X-ray powder diffractometry, thermal analysis, infrared spectroscopy and 13C-NMR analysis, both in the solution and solid phases.
Abstract: For 4-amino-5-chloro-2-methoxy-N-[(2S,4S)-1-ethyl-2-hydroxymethyl-4-pyrrolid inyl]benzamide (TKS159), two polymorphs, forms alpha and beta, were prepared and characterized by means of X-ray powder diffractometry, thermal analysis, infrared spectroscopy and 13C-NMR spectroscopy, both in the solution and solid phases. The X-ray powder diffraction analysis gave different patterns for forms alpha and beta. In the thermogravimetry and differential thermal analysis profiles, form beta exhibited characteristic endo- and exothermic peaks at 112.7 degrees C and 116.2 degrees C, respectively, due to the partial melting-induced phase transition to form alpha without accompanying weight loss, and these were followed by an additional endothermic peak at 138.2 degrees C due to fusion. For form alpha, only an endothermic peak at 137.8 degrees C due to fusion was observed. The IR spectroscopic analyses of forms alpha and beta gave different absorption bands assigned to N-H and O-H stretching, N-H bending, and C=O stretching vibrations. From the data obtained by thermal analysis, form alpha was shown to be thermodynamically more stable than form beta.
TL;DR: In this paper, the effect of self-including host substituent upon the inclusion complexation of arylseleno β-cyclodextrins with alkanol guests was investigated in aqueous buffer solution at 25°C.
Abstract: The effect of self-including host substituent upon the inclusion complexation of arylseleno β-cyclodextrins with alkanol guests has been investigated in aqueous buffer solution at 25°C, by using spectropolarimetric titrations, and the results show that the stability constants of the host–guest complexes formed are correlated with the Hammett's σ value of the host's substituent.
TL;DR: In this article, the effect of temperature on optical yield was investigated over a wide range, and the results showed that the enthalpy term dominated at lower temperatures, while the entropy term becomes more important above T0, switching the product chirality.
Abstract: Photochirogensis, or photochemical induction of molecular
chirality, is an attractive alternative to thermal or enzymatic asymmetric
synthesis. Using the inherent advantage that the photochemical reaction is
driven by light absorption, the effect of temperature on optical yield was
investigated over a wide range. Unexpectedly, the stereochemistry of
photoproduct was frequently inverted at a critical temperature
(T0), above which the optical yield increased with
increasing temperature. The Eyring treatment of the relative rate constant
for the production of each enantiomer revealed that the unusual temperature
dependency originates from the non-zero differential entropy of activation
for the enantiodifferentiating process. In this case, the enthalpy term
dominates at lower temperatures, while the entropy term becomes more
important above T0, switching the product chirality.
The absolute configuration of photoproduct obtained at temperatures lower
than T0 was correlated to that of the chiral
sensitizer, except for those containing very bulky chiral auxiliaries, and
the stereochemical outcomes are discussed on the basis of the molecular
model examinations. Interestingly, similar switching behaviour was induced
by varying the pressure from 0.1 to 400 MPa. The pressure effect was
investigated at different temperatures to construct three-dimensional
diagrams that correlate the optical yield with temperature and pressure as
mutually independent factors. The combined use of temperature and pressure
provides us with a convenient, powerful tool for controlling the product
chirality and optical yield in asymmetric photochemistry.