Increased enantioselectivity in the addition of diethylzinc to benzaldehyde by the use of chiral ligands containing the alpha-phenylethylamino group in combination with achiral ligands

Chiral ligands (S,S)-1, (S,S)-2, (S,S)-3, (S)-4, (S)-5, (S,S)-6, (S,S)-7, and (S,S)-8 turned out to be effective promoters in the enantioselective addition of diethylzinc to benzaldehyde. Interestingly, diamine (S,S)-3 and amino alcohols (S)-5 and (S,S)-7 induce the preferential formation of carbinol (R)-10 (unlike stereoinduction) whereas amido analogues (S,S)-2, (S)-4, and (S,S)-6 favor (S)-10 (like stereoinduction). Molecular modeling at the semiempirical PM3 level provided a reasonable interpretation based on conformational effects in the corresponding transition structures. Combinations of chiral ligands 1-8 with an achiral, flexible ligand (9) gave rise to an activated catalytic system that resulted in faster and higher yielding reactions. Furthermore, substantial increases in the observed enantiomeric excesses of product 10 confirmed the relevant role of achiral bis(sulfonamide) 9 as activator and "chiral environment amplifier".     

Application of Geopolymer in Stabilization/Solidification of Hazardous Pollutants: A Review

Geopolymers, as a kind of inorganic polymer, possess excellent properties and have been broadly studied for the stabilization/solidification (S/S) of hazardous pollutants. Even though many reviews about geopolymers have been published, the summary of geopolymer-based S/S for various contaminants has not been well conducted. Therefore, the S/S of hazardous pollutants using geopolymers are comprehensively summarized in this review. Geopolymer-based S/S of typical cations, including Pb, Zn, Cd, Cs, Cu, Sr, Ni, etc., were involved and elucidated. The S/S mechanisms for cationic heavy metals were concluded, mainly including physical encapsulation, sorption, precipitation, and bonding with a silicate structure. In addition, compared to cationic ions, geopolymers have a poor immobilization ability on anions due to the repulsive effect between them, presenting a high leaching percentage. However, some anions, such as Se or As oxyanions, have been proved to exist in geopolymers through electrostatic interaction, which provides a direction to enhance the geopolymer-based S/S for anions. Besides, few reports about geopolymer-based S/S of organic pollutants have been published. Furthermore, the adsorbents of geopolymer-based composites designed and studied for the removal of hazardous pollutants from aqueous conditions are also briefly discussed. On the whole, this review will offer insights into geopolymer-based S/S technology. Furthermore, the challenges to geopolymer-based S/S technology outlined in this work are expected to be of direct relevance to the focus of future research.     

Long-range exciton-coupled circular dichroism: application for determination of the absolute configuration of oligonaphthalenes

Hexadecanaphthalenes (S,S,S,S,S,S,S,S,S,S,S,S,S,S,S)-4b and (S,S,S,S,S,S,S,R,S,S,S,S,S,S,S)-4b that possess two tetraphenylporphyrins (TPP) on the upper and lower naphthalene rings were synthesized. Long-range exciton-coupled CD in the Soret region of TPP (about 66 A) was observed. [structure: see text]     

Importance of properties of the lowest and higher singlet excited states on the resonant two-photon ionization of stilbene and substituted stilbenes using two-color two-lasers

Radical cations of trans-stilbene and substituted trans-stilbenes (stilbenes and the radical cations denote Sand S(*+), respectively) were generated from the resonant two-photon ionization (TPI) in acetonitrile with irradiation of one-laser (266- or 355-nm laser) and with simultaneous irradiation of two-color two-lasers (266- and 532-nm or 355- and 532-nm lasers) with the pulse width of 5 ns each. The formation yields of S(*+), the TPI efficiency, depended on the properties of S in the lowest and higher singlet excited state (S(S(1)) and S(S(n))), generated from one-photon excitation with 266- or 355-nm laser and from two-photon excitation with simultaneous irradiation of 266- and 532-nm or 355- and 532-nm lasers, respectively. The TPI efficiency using two-color two-lasers increased compared with that using one-laser. It is confirmed that the TPI proceeds through two-step two-photon excitation with the S(0) --> S(1) --> S(n)() transition. In addition to the electronic character of S(S(0)) which depends on the substituent of S, oxidation potential, and molar absorption coefficient of the S(0) --> S(1) absorption as well-known important factors for the TPI efficiency, it is shown that properties of S(S(1)) and S(S(n)) such as lifetimes, electronic characters of S(S(1)) and S(S(n)), molar absorption coefficient of the S(1) --> S(n) absorption, and ionization rate from S(S(n)) are also important.     

The accessibility of antigenic determinants of ribosomal protein S4 in situ.

Antibodies to Escherichia coli ribosomal protein S4 react with S4 in subribosomal particles, eg, the complex of 16S RNA with S4, S7, S8, S15, S16, S17, and S19 and the RI reconstitution intermediate, but they do not react with intact 30S subunits. Antibodies were isolated by three different methods from antisera obtained during the immunization of eight rabbits. Some of these antibody preparations, which contained contaminant antibodies directed against other ribosomal proteins, reacted with subunits, but this reaction was not affected by removal of the anti-S4 antibody population. Other antibody preparations did not react with subunits. It is concluded that the antigenic determinants of S4 are accessible in some protein deficient subribosomal particles but not in intact 30S subunits.     

皂素皂苷脂肪链中甲基绝对构型的确定

利用Sharpless环氧化和Roush反应合成了皂素苷脂肪链中C9脂肪酸单体的两个非对映异构体,即(3S,5S,6S)-3,5-二羟基-6-甲基-δ-辛酸内酯和(3S,5S,6R)-3,5-二羟基-6-甲基-δ-辛酸内酯。通过与天然样品进行理化数据对比,确定了皂素皂苷脂肪链中甲基的绝对构型为S。     

Ultrafast nonradiative decay of electronically excited States of malachite green: ab initio calculations

We have investigated the nonradiative deactivation process of malachite green in the singlet excited states, S(1) and S(2), by high-level ab initio quantum chemical calculations using the CASPT2//CASCF approach. The deactivation pathways connecting the Franck-Condon region and conical intersection regions are identified. The initial population in the S(1) state is on a flat surface and the relaxation involves a rotation of phenyl rings, which leads the molecule to reach the conical intersection between the S(1) and S(0) states, where it efficiently decays back to the ground state. There exists a small barrier connecting the Franck-Condon and conical intersection regions on the S(1) potential energy surface. The decay mechanism from the S(2) state also involves the twisting motion of phenyl rings. In contrast to the excitation to the S(1) state, the initial population is on a downhill ramp potential and the barrierless relaxation through the rotation of substituted phenyl rings is expected. During the course of relaxation, the molecule switches to the S(1) state at the conical intersection between S(2) and S(1), and then it decays back to the ground state through the intersection between S(1) and S(0). In relaxation from both S(1) and S(2), large distortion of phenyl rings is required for the ultrafast nonradiative decay to the ground state.     

Fatty Acid Composition of Sideritis Species

Seed oils of 15Sideritisspecies collected from different regions in Turkey(S. athoa, S. brevidens, S. caesarea, S. condensata, S. congesta, S. dichotoma, S. erythrantha var. cedretorum, S. germanicopolitana ssp. germanicopolitana, S. hololeuca, S. lanata, S. libanotica ssp. violascens, S. lycia, S. niveotomentosa, S. perfoliata, S. phrygia, S. pisidica)were obtained by a Soxhlet apparatus using hexane. The oil yields were found to be between 5.6-36.3%. Fatty acids in the oils were converted to methyl esters and their compositions were determined by GC/MS. The main fatty acid components of the oils from all the species are linoleic (45.4-64.0%), oleic (12.3-26.5%), 6-octadecynoic (4.5-26.8%), palmitic (0.3-9.4%), and linolenic (0.8-2.0%) acids.     

Ultrafast relaxation dynamics of the excited states of Michler's thione

Ultrafast relaxation dynamics of the S2 and S1 states of 4,4'-bis(N,N-dimethylamino)thiobenzophenone (Michler's thione, MT) have been investigated in different kinds of solvents, using steady-state absorption and emission as well as femtosecond transient absorption and fluorescence up-conversion spectroscopic techniques. Steady-state fluorescence measurements, following photoexcitation to the S2 state of MT, reveal weak fluorescence from the S2 state (phi F approximately 10(-3) in nonpolar and 10(-4) in polar solvents) but much weaker fluorescence from the S1 state. Yield of fluorescence from the S2 state is reduced in polar solvents because of reduced energy gap between the S2 and S1 states, Delta E(S2-S1), as well as interaction with the solvent molecules. Occurrence of S2-fluorescence in polar solvents, despite small energy gap, suggests that symmetry allowed S2(1A1) --> S0 (1A1) radiative and symmetry forbidden S2(1A1) --> S1 (1A2) nonradiative transitions are the factors responsible for the S2 fluorescence in MT. Lifetime of the S2 state is shorter (varying in the range 0.28-3.5 ps in different solvents) than that predicted from the Delta E(S2-S1) value and this can be attributed to its flexible molecular structure, which promotes an efficient intramolecular radiationless deactivation pathways. The lifetime of the S1 state (approximately 1.9-6.5 ps) is also very short because of small energy difference between the S1 and T1 states (Delta E(S1-T1) approximately 300 cm(-1)) in cyclohexane and hydrogen-bonding interaction as well as the presence of the isoenergetic T1(pipi*) state to enhance the rate of the intersystem crossing process from the S1(npi*) state in protic solvents.     

Insights into dynamics of the S2 state of thiophosgene from ab initio calculations

The S2 potential energy surface for Cl2CS dissociation has been characterized with a combined complete active space self-consistent field and multireference configuration interaction method. The S3/S2 minimum-energy intersection has been determined with the state-averaged complete active space self-consistent field method. The S2 direct dissociation was found to have a barrier of 6.0 kcal/mol, leading to formation of Cl(X2P)+ClCS(A2A") in the excited electronic state. Dynamics of the S2 state of Cl2CS can be summarized as follows: (1) The S2-S0 fluorescence occurs with high quantum yield at low excess energies; (2) Both the S(2) dissociation and the S2-->S3 internal conversion cause the loss of the S2-S0 fluorescence upon photoexcitation at 235-253 nm; (3) The S2-->S3 internal conversion (IC) followed by the direct IC to the ground electronic state results in the fragments produced in the ground state, while the S2 dissociation leads to formation of the fragments in excited electronic states.     

Luminescence properties of the mixed J-aggregate of oxacyanine dye and thiacyanine dye. Formation of a persistence-type aggregate

The monolayer assemblies incorporating the J-aggregates of oxacyanine dye, N,N'-dioctadecyloxacyanine perchlorate (S9), and thiacyanine dye, N,N'-dioctadecylthiacyanine perchlorate (S11), S9(J) + S11(J), have been fabricated by the Langmuir-Blodgett (LB) technique. The mole fraction X of S11, X = [S11]/([S9] + [S11]), was varied from 0 to 1. Steady-state absorption spectra, fluorescence spectra, and picosecond fluorescence decay curves of the monolayer assemblies have been measured. Spectroscopic properties of the monolayer assemblies incorporating the individual dye aggregates, S9 J-aggregate (S9(J), X = 0) or S11 J-aggregate (S11(J), X = 1), are characterized by a distinct J-band and resonance fluorescence at lambda(ab) = 403 nm and lambda(em) = 403 nm for S9(J) and lambda(ab) = 456 nm and lambda(em) = 463 nm for S11(J). On the other hand, absorption spectra of the S9(J) + S11(J) assemblies for X = 0.1-0.9 display two absorption bands, a shorter wavelength one and a longer wavelength one, whose peak positions are blue-shifted from those of the corresponding J-bands of the S9 J-aggregate and the S11 J-aggregate, respectively. Furthermore, fluorescence spectra are characterized by a single band (longer wavelength fluorescence) which is somewhat blue-shifted from the resonance fluorescence of the S11 J-aggregate. The fluorescence lifetimes of the S11 J-aggregate and isolated S11 molecules in LB films appear to be tau = 110 and 1900 ps, respectively, while the fluorescence lifetime of the longer wavelength fluorescence of the S9(J) + S11(J) assemblies takes practically a constant value of tau = 170-180 ps for X = 0.2-0.8. These observations would indicate that S9 and S11 molecules in the S9(J) + S11(J) assembly can form a specific mixed aggregate distinct from the individual S9 and S11 J-aggregates. From detailed considerations of the former works on luminescence properties of the S9 J-aggregate doped with isolated S11 molecules, as well as the mosaic-type mixed J-aggregate (M-aggregate) composed of a certain thiacyanine dye, 3,3'-disulfopropyl- 5,5'-dichlorothiacyanine sodium salt, and thiacarbocyanine dye, meso-substituted 3,3'-disulfopropyl-5,5'-dichlorothiacarbocyanine potassium salt, it is suggested that S9 and S11 can form a homogeneous aggregate of the persistence type (HP-aggregate). The HP-aggregate is distinguished from the M-aggregate because it is characterized by homogeneous mixing of two component dyes and persistence of two absorption bands.     

Hydrogenation versus transfer hydrogenation of ketones: two established ruthenium systems catalyze both

The established standard ketone hydrogenation (abbreviated HY herein) precatalyst [Ru(Cl)(2)((S)-tolbinap)[(S,S)-dpen]] ((S),(S,S)-1) has turned out also to be a precatalyst for ketone transfer hydrogenation (abbreviated TRHY herein) as tested on the substrate acetophenone (3) in iPrOH under standard conditions (45 degrees C, 45 bar H(2) or Ar at atmospheric pressure). HY works at a substrate catalyst ratio (s:c) of up to 10(6) and TRHY at s:c<10(4). Both produce (R)-1-phenylethan-1-ol ((R)-4), but the ee in HY are much higher (78-83 %) than in TRHY (4-62 %). In both modes, iPrOK is needed to generate the active catalysts, and the more there is (1-4500 equiv), the faster the catalytic reactions. The ee is about constant in HY and diminishes in TRHY as more iPrOK is added. The ketone TRHY precatalyst [Ru(Cl)(2)((S,S)-cyP(2)(NH)(2))] ((S,S)-2), established at s:c=200, has also turned out to be a ketone HY precatalyst at up to s:c=10(6), again as tested on 3 in iPrOH under standard conditions. The enantioselectivity is opposite in the two modes and only high in TRHY: with (S,S)-2, one obtains (R)-4 in up to 98 % ee in TRHY as reported and (S)-4 in 20-25 % ee in HY. iPrOK is again required to generate the active catalysts in both modes, and again, the more there is, the faster the catalytic reactions. The ee in TRHY are only high when 0.5-1 equivalents iPrOK are used and diminish when more is added, while the (low) ee is again about constant in HY as more iPrOK is added (0-4500 equiv). The new [Ru(H)(Cl)((S,S)-cyP(2)(NH)(2))] isomers (S,S)-9 A and (S,S)-9 B (mixture, exact structures unknown) are also precatalysts for the TRHY and HY of 3 under the same conditions, and (R)-4 is again produced in TRHY and (S)-4 in HY, but the lower ee shows that in TRHY (S,S)-9 A/(S,S)-9 B do not lead to the same catalysts as (S,S)-2. In contrast, the ee are in accord with (S,S)-9 A/(S,S)-9 B leading to the same catalysts as (S,S)-2 in HY. The kinetic rate law for the HY of 3 in iPrOH and in benzene using (S,S)-9 A/(S,S)-9 B/iPrOK or (S,S)-9 A/(S,S)-9 B/tBuOK is consistent with a fast, reversible addition of 3 to a five-coordinate amidohydride (S,S)-11 to give an (S,S)-11-substrate complex, in competition with the rate-determining addition of H(2) to (S,S)-11 to give a dihydride [Ru(H)(2)((S,S)-cyP(2)(NH)(2))] (S,S)-10, which in turn reacts rapidly with 3 to generate (S)-4 and (S,S)-11. The established achiral ketone TRHY precatalyst [Ru(Cl)(2)(ethP(2)(NH)(2))] (12) has turned out to be also a powerful precatalyst for the HY of 3 in iPrOH at s:c=10(6) and of some other substrates. Response to the presence of iPrOK is as before, except that 12 already functions well without it at up to s:c=10(6).     

A density functional theory study of sulfur poisoning

Density functional theory calculations have been used to investigate the chemisorption of H, S, SH, and H(2)S as well as the hydrogenation reactions S+H and SH+H on a Rh surface with steps, Rh(211), aiming to explain sulfur poisoning effect. In the S hydrogenation from S to H(2)S, the transition state of the first step S+H-->SH is reached when the S moves to the step-bridge and H is on the off-top site. In the second step, SH+H-->H(2)S, the transition state is reached when SH moves to the top site and H is close to another top site nearby. Our results show that it is difficult to hydrogenate S and they poison defects such as steps. In order to address why S is poisoning, hydrogenation of C, N, and O on Rh(211) has also been calculated and has been found that the reverse and forward reactions possess similar barriers in contrast to the S hydrogenation. The physical origin of these differences has been analyzed and discussed.     

Solvent-dependent activation of intermediate excited states in the energy relaxation pathways of spheroidene

In carotenoids internal conversion between the allowed (S(2)) and forbidden (S(1)) excited states occurs on a sub-picosecond timescale; the involvement of an intermediate excited state(s) (S(x)) mediating the process is controversial. Here we use high time resolution (sub-20 fs) broadband (1.2-2.5 eV) pump-probe spectroscopy to study the solvent dependence of excited state dynamics of spheroidene, a naturally-occurring carotenoid with ten conjugated double bonds. In the high polarizability solvent, CS(2), we find no evidence of an intermediate state, and the traditional three-level (S(0), S(1), S(2)) model fully accounts for the S(2)→ S(1) process. On the other hand, in the low polarizability solvent, cyclohexane, we find that rapid (~30 fs) relaxation to an intermediate state, S(x), lying between S(1) and S(2) is required to account for the data. We interpret these results as due to a shift of the S(2) energy, which positions the state above or below the energy of S(x) in response to changes in solvent polarizability.     

Reaction coordinate analysis of the S1-S0 internal conversion of azulene

The reaction coordinate of the S(1)-S(0) internal conversion of azulene has been analyzed using ab initio complete active space self-consistent field method. The stable geometry in S(0) (S(0) geometry) takes a bond-equalized structure where all the peripheral skeletal bond distances are similar to an aromatic CC bond distance. The transannular bond is similar to a normal C-C single bond. The first event upon electronic excitation into S(1) at S(0) geometry is characterized by the following two simultaneous changes in the skeletal bonds; the transannular bond in S(1) increases its double bond character and the aromaticity of the peripheral bonds disappears. In consequence, the most stable azulene in S(1) (S(1) geometry) has a biradical character. To reach the conical intersection between S(1) and S(0) (S(1)S(0)-CIX) where radiationless relaxation takes place, the seven-membered ring greatly deviates from a planar structure. After a transition into S(0) at S(1)S(0)-CIX, the bond-equalized structure is recovered immediately and then the nonplanarity decreases so that azulene again takes the stable planar S(0) geometry. In order to deepen the understanding of the S(1)-S(0) internal conversion, the dipole moments along the reaction coordinate have been analyzed.     

Recombination analysis of autosomal short tandem repeats in Chinese Han families

Recombination fractions between forensic STRs can be extrapolated from the International HapMap Project, but the concordance between recombination fractions predicated from genetic maps and derived from observation of STR transmissions in families is still ambiguous for autosomal STRs because of limited family studies. Therefore, the main goal of this study is to compare recombination fractions estimated by pedigree analysis with those derived from HapMap phase SNP data. Genotypes of nine autosomal STR pairs (TPOX‐D2S1772, D5S818‐CSF1PO, D7S3048‐D7S820, D8S1132‐D8S1179, TH01‐D11S2368, vWA‐D12S391, D13S325‐D13S317, D18S51‐D18S1364, and D21S11‐PentaD) from 207 two‐generation families with two to five children (the number of families with five, four, three, and two children was 2, 3, 20, and 182, respectively) were used to analyze the recombination. The linkage analysis showed that significant linkage was observed at six STR pairs (D5S818‐CSF1PO, D8S1132‐D8S1179, TH01‐D11S2368, vWA‐D12S391, D13S325‐D13S317, and D18S51‐D18S1364) with genetic distances <36.22 cM in HapMap. Their recombination fractions calculated from family data were very close to those derived from HapMap. However, three STR pairs of TPOX‐D2S1772, D7S3048‐D7S820, and D21S11‐PentaD showed no significant linkage with genetic distances from 43.38 to 91.49 cM. Our results indicate that recombination fractions extrapolated from HapMap can provide a substitute if empirical data are unavailable for the linkage STR pair with a genetic distance spanned <36.22 cM.     

Structures and vibrational spectra of the sulfur-rich oxides SnO (n = 4-9): the importance of pi*-pi* interactions

The structures of a large number of isomers of the sulfur oxides S(n)O with n = 4-9 have been calculated at the G3X(MP2) level of theory. In most cases, homocyclic molecules with exocyclic oxygen atoms in an axial position are the global minimum structures. Perfect agreement is obtained with experimentally determined structures of S(7)O and S(8)O. The most stable S(4)O isomer as well as some less stable isomers of S(5)O and S(6)O are characterized by a strong pi*-pi* interaction between S==O and S==S groups, which results in relatively long S--S bonds with internuclear distances of 244-262 pm. Heterocyclic isomers are less stable than the global minimum structures, and this energy difference approximately increases with the ring size: 17 (S(4)O), 40 (S(5)O), 32 (S(6)O), 28 (S(7)O), 45 (S(8)O), and 54 kJ mol(-1) (S(9)O). Owing to a favorable pi*-pi* interaction, preference for an axial (or endo) conformation is calculated for the global energy minima of S(7)O, S(8)O, and S(9)O. Vapor-phase decomposition of S(n)O molecules to SO(2) and S(8) is strongly exothermic, whereas the formation of S(2)O and S(8) is exothermic if n<7, but slightly endothermic for S(7)O, S(8)O, and S(9)O. The calculated vibrational spectra of the most stable isomers of S(6)O, S(7)O, and S(8)O are in excellent agreement with the observed data.     

Theoretical study of photodissociation dynamics on the lowest-lying Rydberg state of ketene

In the present study, an attempt is made to reveal the main mechanism of photodissociation on the lowest-lying Rydberg state (1)B(1) of ketene, referred to as the second singlet excited state S(2), by means of the complete active space self-consistent field and the second-order multiconfigurational perturbation theory methods. The located S(2)S(1)T(1) three-surface intersection plays an important role in the dissociation process. It is shown that the intersection permits an efficient internal conversion from S(2) to S(1) state, but prohibits the intersystem crossing from S(2) to T(1) state because of the small spin-orbital coupling value of 0.136 cm(-1). The main photodissociation process could be described as follows: after one photon absorption to the S(2) state, ketene preferentially relaxes to the minimum S(2)C(2v), and undergoes a transition state S(2)TS with small potential barrier along the C(s)-I (out-of-plane bent) symmetry, and passes through the S(2)S(1)T(1) intersection to reach S(1) surface, then arrives at the transition state S(1)TS along the minimum energy path. As is well known, S(1)-->S(0) internal conversion around the Franck-Condon region is expected to be very efficient, and eventually the hot S(0) molecule has accumulated enough energy to yield the CH(2) (a (1)A(1)) and CO (X (1)Sigma(+)) products.     

硫代硫酸盐浸金过程中连多硫酸根的高效毛细管电泳法分析

采用高效毛细管电泳对硫代硫酸盐提金浸出液中的S3O62-和S4O62-进行分析研究,对缓冲溶液,电压、和检测波长对分析的影响进行了探讨。适宜的分离条件为:5 mmol/L(NH4)2SO4、5 mmol/L NaH2PO4,pH 6的缓冲溶液;重力进样5s,电压-20kV,波长214nm,有效长度为30 cm。在0.1～6 mmol/L和0.05～4mmol/L范围内S3O62-和S4O62-浓度与峰面积呈线性关系,在此进样条件下,S3O62-与S4O62-浓度高于80与50 mmol/L时信噪比大于2。实际浸金液用缓冲溶液稀释100倍后,S3O62-与S4O62-可实现基线分离,其它离子几乎不干扰检测。     

Molecular modeling of salt (lithium chloride) effects on the enantioselectivity of diethylzinc addition to benzaldehyde in the presence of chiral beta-amino alcohols

Beta-amino alcohols (S,S,S)-1 and (R,R,S)-1, derived from cyclohexene oxide and containing alpha-phenylethyl auxiliaries, were examined as chiral promoters in the addition of diethylzinc to benzaldehyde. In agreement with literature precedent, the N-alpha-phenylethyl chiral auxiliary had no significant impact on enantioinduction, which is determined by the configuration of the framework's C(OH), with unlike induction. Contrary to some literature reports, stereoinduction by lithium salt derivatives of (S,S,S)-1 and (R,R,S)-1 was lower than that obtained with the free amino alcohol. Remarkable lithium chloride salt effects were observed in the reaction. In particular, an opposite chiral induction was found with (S,S,S)-1-Li(2) as ligand and in the presence of "inert" salt. N-Alkylated derivatives (S,S,S)-3-7 proved to be more efficient ligands, providing higher yields and enantioselectivities in the formation of carbinols (R)- or (S)-2. BP86/DN**//PM3 theoretical calculations proved remarkably successful in reproducing the experimental observations and permitted expansion of Noyori's catalytic cycle [J. Am. Chem. Soc. 1995, 117, 6327] to understand the relevant N-substitution and medium salt effects that determine the enantioselection in this catalytic asymmetric reaction.