Construction of Acyclic All-Carbon Quaternary Stereocenter Based on Asymmetric Michael Addition of Chiral Amine.

Acyclic asymmetric quaternary stereocenters, which are composed of four carbon-carbon bonds, were finely constructed by utilizing a face-selective alkylation of enolate intermediates derived from an asymmetric Michael addition reaction of a chiral lithium amide with trisubstituted (E)-α,β-unsaturated esters. The present face-selective alkylation was able to employ diverse alkyl halides as an electrophile to afford various Michael adducts having an all-carbon quaternary stereocenter. With regard to the deprotection of the chiral auxiliary, N-iodosuccinimide used in our previous study did not work in the present cases; however, we found that pyridine iodine monochloride in the presence of HO was effective to remove the bornyl group and the benzyl group on the amino group to provide the β-amino ester derivative.

A Facile and Convenient Synthesis of Trisubstituted (E)-α,β-Unsaturated Esters by Tandem Acetylation-E1cB Reaction.

A facile and convenient synthesis of trisubstituted (E)-α,β-unsaturated esters was developed by improving our previously established method. The new method circumvented the separation of the intermediates, which have an activating group of the hydroxyl group in β-hydroxy esters, furnishing α,β-unsaturated esters in shorter steps than the previous method: an acetylation of β-hydroxy group and subsequent E1cB reaction proceeded in tandem. In addition, the new method can not only employ a diastereomeric mixture of the substrate for the E1cB reaction, it has a wide substrate scope as well, which would enable the synthesis of various trisubstituted (E)-α,β-unsaturated esters.

Carotenoid Stereochemistry Affects Antioxidative Activity of Liposomes Co-encapsulating Astaxanthin and Tocotrienol.

We previously found that antioxidative activity of liposomes co-encapsulating astaxanthin (Asx) and tocotrienols (T3s) was higher than the calculated additive activity, which results from intermolecular interactions between both antioxidants (J. Clin. Biochem.

Synergistic antioxidative effect of astaxanthin and tocotrienol by co-encapsulated in liposomes.

Astaxanthin and vitamin E are both effective antioxidants that are frequently used in cosmetics, as food additives, and in to prevent oxidative damage. A combination of astaxanthin and vitamin E would be expected to show an additive anntioxidative effect. In this study, liposomes co-encapsulating astaxanthin and the vitamin E derivatives α-tocopherol (α-T) or tocotrienols (T3) were prepared, and the antioxidative activity of these liposomes toward singlet oxygen and hydroxyl radical was evaluated .

Conformation and atropisomeric properties of indometacin derivatives.

The stereochemistry around the N-benzoylated indole moiety of indometacin was studied by restricting the rotation about the N-C7' and/or C7'-C1' bond. In the 2',6'-disubstituted ones, an atropisomeric property was found and the atropoisomers were separated and isolated as stable forms. Their biological abilities to inhibit cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were examined.

Novel approach to determining the absolute configurations at the C3-positions of various types of sterols based on an induced circular dichroism.

Circular dichroism (CD) spectra of the 2,2'-binaphthyl ester derived from Δ(5)-sterols showed not bisignate CD but diagnostic CD bands at around 210 and 240 nm. These bands might be attributable to an interaction between an olefinic chromophore and a binaphthyl one. Various types of unsaturated sterols were thus derivatized followed by complete hydrogenation, to give saturated sterols.

Straightforward approach to the discrimination of (4R)- and (4S)-beta-isocryptoxanthin from a conformationally insensitive CD band.

A straightforward strategy is reported for chiral discrimination in a specified carotenoid using a CD band, which is insensitive to conformational changes, computed by quantum chemical calculation.

One-pot construction of multiple contiguous chiral centers using Michael addition of chiral amine.

Multiple contiguous chiral centers were constructed in one pot using three types of multistep reactions initiated with the Michael addition of N-benzyl-2(R)-methoxy-(+)-10-bornylamide to alpha,beta-unsaturated esters, i.e., asymmetric Michael-aldol reaction, double Michael addition, and double Michael-aldol reaction.

Main phenolic compounds from the flower of Trachelospermum asiaticum var. intermedium (Apocynaceae).

Six phenolic compounds were isolated from the flowers of Trachelospermum asiaticum var. intermedium (Apocynaceae). These structures were determined on the basis of spectral data.

Analysis of CYP3A inhibitory components of star fruit (Averrhoa carambola L.) using liquid chromatography-mass spectrometry.

In this study, we analyzed the CYP3A inhibitory components of star fruit Averrhoa carambola L., using liquid chromatography-mass spectrometry (LC-MS). The stereoisomer of procyanidin B1 and B2 and/or the trimer consisting of catechin and/or epicatechin were suggested to be potent inhibitory components.

Isolation of cytochrome P450 3A (CYP3A) inhibitors from Hyuganatsu, Citrus tamurana Hort.

The present study was conducted to identify cytochrome P450 3A (CYP3A) inhibitory components of Hyuganatsu, Citrus tamurana Hort., by investigating the effects on midazolam 1'-hydroxylase activity of human liver microsomes. As a consequence, limonin and nomilin were identified as CYP3A inhibitors from the endocarp of Hyuganatsu.

Structural studies of zoospore attractants from Trachelospermum jasminoides var. pubescens: taxifolin 3-O-glycosides.

(2S, 3S)-Taxifolin 3-O-arabinoside, a new dihydroflavonol glycoside, together with the known substances, (2R 3R)-taxifolin 3-O-arabinoside, astragalin, isoquercitrin, and cosmosiin, were isolated from the leaves of Trachelospermum jasminoides var. pubescens. Structural elucidation was carried out by spectroscopic methods, and the absolute configurations of C-2 and C-3 in taxifolin 3-O-arabinosides were determined on the basis of circular dichroism.

Advanced method for assignment of absolute configuration utilizing an induced CD and computational technique: its application to natural products possessing a secondary alcohol.

A modified procedure for determining absolute configurations using an induced CD method and molecular mechanics calculations is disclosed. The practical usefulness of the present technique was demonstrated by its application to a few natural products.

Crystal structure of Diels-Alder cycloadduct formed from 1-(1,2,3-1H-benzotriazol-1-yl)-2-(4-methylphenyl)-2H-isoindole and dimethyl acetylenedicarboxylate.

The structure of the Diels-Alder cycloadduct formed from 2-(1,2,3-1H-benzotriazol-1-yl)-2-(p-tolyl)-2H-isoindole and dimethyl acetylenedicarboxylate was proved as 11-aza-1-(1,2,3-1H-benzotriazol-1-yl)-11-(4-methylphenyl)-tricyclo-[5.2.1.

Crystal structure of dissymmetrically trihydrated N,N',N''-tribenzoylmelamine (TBM).

In the crystal structure of TBM-trihydrate three waters of crystallization were found to locate dissymmetrically. Thus, one of them forms a chelated ring with the neighboring C=O and N-H of TBM. Two other ones bind each other through hydrogen bonding and two sets of which form a cyclic dimer by hydrogen bonding (namely, water-tetramer).

Dihydroxybergamottin caproate as a potent and stable CYP3A4 inhibitor.

We investigated the inhibitory activity of the furanocoumarin derivatives from grapefruit juice to the drug metabolizing enzyme, cytochrome P450 (CYP) 3A4. Although two known furanocoumarin dimers GF-I-1 (1) and GF-I-4 (2) showed potent CYP3A4 inhibition with IC50 value of 0.07 microM, a semi-synthetic dihydroxybergamottin caproate (11), which was more stable and more simple than the dimers, exhibited comparable activity against CYP3A4.