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The anomeric effect (the tendency of heteroatomic substituents adjacent to a heteroatom within the cyclohexane ring to prefer the axial orientation instead of the sterically less hindered equatorial position) is traditionally explained through either the dipole moment repulsion or the hyperconjugation effect. In this work, by employing our recent work in density functional steric analysis, we provide a novel two-component explanation, which is consistent with the common belief in chemistry that the effect has a stereoelectronic origin. With α-D-glucopyranose as the prototype, we systematically explore its conformational space and generate 32 isomers, leading to a total of 80 axial-equatorial conformation pairs. The energy difference analysis of these pairs shows that while statistically speaking the tendency is valid, the anomeric effect is not always true and can be violated. Three energy components, exchange-correlation, classical electrostatic, and density functional steric, are found to be directly proportional to the total energy difference between axial and equatorial isomers. We also found that the total dipole moment change, not the hyperconjugation effect, is a reasonable indicator of the total energy difference. However, all these correlations alone are not strong enough to provide a compellingly convincing explanation for the general validity of the effect. With the help of strong correlations between energy components, an explanation with two energy components, steric and electrostatic, was proposed in this work. We show that the axial-equatorial energy difference in general, with the anomeric effect as a special case, is dictated by two factors of the stereoelectronic origin, steric hindrance and classical electrostatic interactions, synchronously working together. Another explanation in terms of exchange-correlation and electrostatic interactions has also been obtained in this work.

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Molecular acidity is one of the important physiochemical properties of a molecular system, yet its accurate calculation and prediction are still an unresolved problem in the literature. In this work, we propose to make use of the quantities from the information-theoretic (IT) approach in density functional reactivity theory and provide an accurate description of molecular acidity from a completely new perspective. To illustrate our point, five different categories of acidic series, singly and doubly substituted benzoic acids, singly substituted benzenesulfinic acids, benzeneseleninic acids, phenols, and alkyl carboxylic acids, have been thoroughly examined. We show that using IT quantities such as Shannon entropy, Fisher information, Ghosh-Berkowitz-Parr entropy, information gain, Onicescu information energy, and relative Rényi entropy, one is able to simultaneously predict experimental pKa values of these different categories of compounds. Because of the universality of the quantities employed in this work, which are all density dependent, our approach should be general and be applicable to other systems as well. © 2017 Wiley Periodicals, Inc.

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An enantioselective oxa-Michael-Henry reaction of substituted salicylaldehydes with nitroolefins that proceeds though an aromatic iminium activation (AIA) has been developed by using a chiral secondary amine organocatalyst and salicylic acid as a co-catalyst. The corresponding 3-nitro-2H-chromenes were obtained in moderate-to-good yields with up to 91% ee under mild conditions. Based on the experimental results and ESI-mass spectrometric detection of the intermediates, a plausible transition state has been proposed to explain the origin of the activation and the asymmetric induction.

NotePaeonia suffruticosa ANDR. (Paeoniaceae) is found extensively in China. It is an important Chinese medicinal plant from the section Moutan of the genus Paeonia. This genus consists of ca. 35 species placed in three sections: Moutan, Oneapia, and Paeonia.1) The root cortex of this plant (Chinese name: mudanpi) is a well-known Chinese herbal medicine widely used as an analgesic, anaphylactic, antioxidative, and antiinflammatory agent. Numerous studies on the chemistry and pharmacology of this species have been performed.2) Previous phytochemical studies indicated that stilbenes were the primary bioactivity constituents of peony seeds. These stilbenes exhibit potent biological activities such as cytotoxic, antimutagenic, ecdysteroid antagonist, antioxidant, hyperpigmentation, antitumor, and anti-inflammatory activity and can improve bone disease. [3][4][5][6][7][8] In the course of searching for new bioactive natural products from the seeds of this plant, 11 stilbenes, trans-(1) and cis-suffruticosol D (2), trans-resveratrol (3), 9) trans-e-viniferin (4), 7)cis-e-viniferin (5), 7) gnetin H (6), 7) cis-gnetin H (7), suffruticosol A (8),3) suffruticosol B (9), 3) suffruticosol C (10), 3) and cis-ampelopsin E (11), 10) were isolated from the ethyl acetate extract of the seeds of P. suffruticosa. Among them, 1, 2, and 7 were new compounds. Here, we report the isolation and extensive structural elucidation of the new compounds. Results and Discussiontrans-Suffruticosol D (1) Three new oligostilbenes, trans-suffruticosol D (1), cis-suffruticosol D (2), and cis-gnetin H (7), were isolated along with the eight known stilbenes, trans-resveratrol (3), trans-e e-viniferin (4), cis-e e-viniferin (5), gnetin H (6), suffruticosol A (8), suffruticosol B (9), suffruticosol C (10), and cis-ampelopsin E (11) from the seeds of Paeonia suffruticosa. Compounds 3-6 were isolated for the first time from this plant species, and compound 11 was isolated for the first time from the genus Paeonia. The structures of the new compounds were elucidated based on spectral analyses, including 1D and 2D NMR experiments. The absolute configuration of compound 1 was determined by quantum chemical calculation of the electronic circular dichroism and comparison with the experimental circular dichroism spectrum.