Preparation of molecularly imprinted polymers for strychnine by precipitation polymerization and multistep swelling and polymerization and their application for the selective extraction of strychnine from nux‐vomica extract powder

Monodisperse molecularly imprinted polymers for strychnine were prepared by precipitation polymerization and multistep swelling and polymerization, respectively. In precipitation polymerization, methacrylic acid and divinylbenzene were used as a functional monomer and crosslinker, respectively, while in multistep swelling and polymerization, methacrylic acid and ethylene glycol dimethacrylate were used as a functional monomer and crosslinker, respectively. The retention and molecular recognition properties of the molecularly imprinted polymers prepared by both methods for strychnine were evaluated using a mixture of sodium phosphate buffer and acetonitrile as a mobile phase by liquid chromatography. In addition to shape recognition, ionic and hydrophobic interactions could affect the retention of strychnine in low acetonitrile content. Furthermore, molecularly imprinted polymers prepared by both methods could selectively recognize strychnine among solutes tested. The retention factors and imprinting factors of strychnine on the molecularly imprinted polymer prepared by precipitation polymerization were 220 and 58, respectively, using 20 mM sodium phosphate buffer (pH 6.0)/acetonitrile (50:50, v/v) as a mobile phase, and those on the molecularly imprinted polymer prepared by multistep swelling and polymerization were 73 and 4.5. These results indicate that precipitation polymerization is suitable for the preparation of a molecularly imprinted polymer for strychnine. Furthermore, the molecularly imprinted polymer could be successfully applied for selective extraction of strychnine in nux‐vomica extract powder.     

3,6-Dialkyl-2-hydroxypyrazine 1-oxides as acyl carriers

3,6-Dialkyl-2-hydroxypyrazine 1-oxides were found to be useful as acyl carriers. Benzoyl derivatives were convenient reagents for benzoylation of amines and hydroxy compounds.     

Synthesis of a new potential tridentate anthracene ligand bearing deprotectable methoxymethoxy (OMOM) group at 1,8-positions: attempt to synthesize anionic hypervalent carbon compounds

A novel potential tridentate ligand bearing deprotectable coordinating atoms, 1,8-bis(methoxymethoxy)-9-bromoanthracene (15), was synthesized. The key steps are as follows: 1) stepwise mono-oxygenation from 1,8-dibromo-9-methoxyanthracene by use of electrophilic oxaziridine and gaseous dioxygen, and 2) selective reduction of the methoxy group by LDBB (lithium di-tert-butylbiphenylide) followed by treatment with BrCF(2)CF(2)Br. The corresponding 1,8-bis(methoxymethoxy)-9-lithio-anthracene (14), which should be a useful versatile trianion equivalent, could be generated by treatment of the bromide with one equivalent of nBuLi. The lithioanthracene reacted with hexafluoroacetone to give the deprotected ether 17 together with the adduct alcohol 16. The ether could easily be deprotected to give 1,2-dihydro-1,1-bis(trifluoromethyl)-2-oxa-9-hydroxyanthrylene (8), which was deprotonated with KH in the presence of [18]crown-6 to give the corresponding anion (9-K([18]crown-6)). The X-ray structure and NMR spectra of 9-K([18]crown-6) showed that it has an unsymmetrical structure probably due to the interaction between the oxygen atom of the phenoxide and the potassium cation surrounded by the crown ether.     

2-Acyloxypyrazines. Convenient acylating agents for amines

2-Acyloxypyrazines were found to be useful acylating reagents for amines. The preference of the acylation was for primary amines rather than secondary ones and also for aliphatic amines rather than aromatic ones.     

Solution and biologically relevant conformations of enantiomeric 11-cis-locked cyclopropyl retinals

To gain information on the conformation of the 11-cis-retinylidene chromophore bound to bovine opsin, the enantiomeric pair (2a and 2b) of 11-cis-locked bicyclo[5.1.0]octyl retinal (retCPr) 2 was prepared and its conformation was investigated by NMR, geometry optimization, and CD calculations. This compound is also of interest since it contains a unique moiety in which a chiral cyclopropyl group is flanked by triene and enal chromophores, and hence would clarify the little-known chiroptical contribution of a cyclopropyl ring linked to polyene systems. NMR revealed that the seven-membered ring of retCPr adopts a twist chair conformation. The NMR-derived structure constraints were then used for optimizing the geometry of 2 with molecular mechanics and ab initio methods. This revealed that enantiomer 2a with a 11 beta,12 beta-cyclopropyl group exists as two populations of diastereomers depending on the twist around the 6-s bond; however, the sense of twist around the 12-s is positive in both rotamers. The theoretical Boltzmann-weighted CD obtained with the pi-SCF-CI-DV MO method and experimental spectra were consistent, thus suggesting that the conjugative effect of the cyclopropyl moiety is minimal. It was found that only the beta-cyclopropyl enantiomer 2a, but not the alpha-enantiomer 2b, binds to opsin. This observation, together with earlier retinal analogues incorporation results, led to the conclusion that the chromophore sinks into the N-terminal of the opsin receptor from the side of the 4-methylene and 15-aldehyde, and that the binding cleft accommodates 11-cis-retinal with a slightly positive twist around C12/C13. A reinterpretation of the previously published negative CD couplet of 11,12-dihydrorhodopsin also leads to a chromophoric C12/C13 twist conformation with the 13-Me in front as in 1b. Such a conformation for the chromophore accounts for both the observed biostereoselectivity of retCPr 2a and the observed negative couplet of 11,12-dihydro-Rh7.     

Synthesis of 4-heterocyclyl-hexahydro-8-methoxyfuro[3,2-c]quinolines by Lewis acid catalyzed [4 + 2]cycloaddition reaction

Synthesis of 2-substituted quinoline derivatives by Lewis acid catalyzed [4 + 2]cycloaddition was investigated.     

Rapid analysis of amino acids in Japanese green tea by microchip electrophoresis using plastic microchip and fluorescence detection

Microchip electrophoresis for the short-time analysis of amino acids in Japanese green tea was developed. The amino acids in Japanese green tea were derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F). The derivatives were filtered and directly analyzed by electrophoresis on a plastic microchip with a 31-mm long separation channel with fluorescence detection. Amino acid analysis of Japanese green tea was improved by removing polyphenols using a polyvinylpolypyrrolidone pretreatment. Elution profiles of NBD-amino acids were examined under different running buffer conditions, and the sodium dodecyl sulphate in the running buffer exhibited a dramatically high-separation efficiency of amino acids by inhibiting their adsorption on the channel walls. Under the optimized conditions (5 mM phosphate buffer (pH 5.5) containing 0.05 mM sodium dodecylsulfate as running buffer), the main amino acids contained in Japanese green tea were well separated within 2 min, and theanine (1475 mg/100 g tea leaf), Arg (408 mg/100 g tea leaf) and Gln (217 mg/100 g tea leaf) were detected in Japanese green tea.     

Isolation and structures of citropone-A and -B from citrus plants,first examples of naturally-occurring homoacridone alkaloids containing a tropone ring system

The first isolation of homoacridone alkaloids, citropone-A ($\text{1}$) and -B ($\text{2}$), from the root bark of $\text{Citrus}$$\text{grandis}$ Osbeck f. $\text{buntan}$ Hayata and $\text{C}$. $\text{natsudaidai}$ Hayata is described.     

Palladium-catalysed direct synthesis of benzo[b]thiophenes from thioenols

The one-pot conversion of thioenols into benzo[b]thiophenes was achieved by using a simple palladium catalyst such as PdCl(2) or PdCl(2)(cod).     

Electronic energy band structure of the double perovskite Ba2MnWO6

The electronic and magnetic structures of the double perovskite oxide Ba 2MnWO6 (BMW) were determined by employing the density functional theory within the generalized gradient approximation (GGA) + U approach. BMW is considered a prototype double perovskite due to its high degree of B-site ordering and is a good case study for making a comparison between computations and experiments. By adjusting the U-parameter, the electronic energy band structure and magnetic properties, which were consistent with the experimental results, were obtained. These computations revealed that the valence bands are mainly formed from Mn 3d and O 2p states, while the conduction bands are derived from W 5d and O 2p states. The localized bands composed from Mn 3d states are located in the bandgap. The results imply that the formation of polarons in the conduction band initiate the resonance Raman modes observed as a series of equidistant peaks.