Tatsuro Kijima

Zinc-Mediated Allylation and Alkylation of Aminals in the Presence of TMSCl and Diisopropylamine

An alkylation of aminals with organozinc reagents derived from allyl bromide, benzyl bromide, alpha-bromoacetate, and alpha-bromonitrile proceeded efficiently in the presence of TMSCl and diisopropylamine. This reaction system was applied to the synthesis of an antispasmodic: butaverine.

Synthesis and electrochemical properties of 1,1'-bis(benzo-1,3-dithiol-2-ylidene)ferrocene derivatives as novel electron donor compounds

Abstract A number of 1,1′-bis(benzo-1,3-dithiol-2-ylidene)ferrocene derivatives 7a–b and 12–14 based on the strong electron donating ability of 1,3-dithiole and ferrocene moieties were synthesized as new π-donors. The structure and physical properties of these compounds were characterized both by experimental techniques and spectral analysis. These new classes of donor compounds were obtained in very high yields based on modification of the Wittig–Horner reaction and the 1,3-dithiole rings were separated by conjugated spacers including aryl–ferrocenyl–aryl. The electrochemical properties of the new compounds have been studied in comparison to DB-TTF 4 analogues, and the parent ferrocene donor by cyclic voltammetry (CV), using Pt electrode as the working electrode in CH2Cl2 solutions at room temperature. Three subsequent oxidation processes are observed as three oxidation waves associated only with two reduction processes. Polycrystalline samples of 14a–b are conducting σrt 14a=0.2 S cm−1 and σrt 14b=4.8×10−4 S cm−1) respectively, while compounds 15 and 16 were found essentially as insulator (σrt

Palmitoleic Acid Calcium Salt: A Lubricant and Bactericidal Powder from Natural Lipids

Palmitoleic acid is a promising bactericidal agent for cleansing products with alternative bactericidal abilities. In this study, we focus on the physical and biological activity of palmitoleic acid calcium salt (C16:1 fatty acid Ca salt) because it forms via an ion-exchange reaction between palmitoleic acid and Ca ions in tap water, and remains on the skin surface during the cleansing process. Here, we prepared C16:1 fatty acid Ca salt to investigate its crystal structure and physical and bactericidal properties. The Ca salt was a plate-shaped lamellar crystalline powder with a particle diameter of several micrometers to several tens of micrometers; it exhibited significant lubricity and alternative bactericidal activity against Staphylococcus aureus (S. aureus) and Propionibacterium acnes (P. acnes). We also examined other fatty acid Ca salts prepared from lauric acid (C12:0 fatty acid), palmitic acid (C16:0 fatty acid), and oleic acid (C18:1 fatty acid). The bactericidal activities and lubricity of the fatty acid Ca salts changed with the alkyl chain length and the degree of unsaturation. The C16:1 fatty acid Ca salt exhibited the strongest selective bactericidal ability among the four investigated fatty acid Ca salts. These findings suggest that C16:1 fatty acid and its Ca salt have potential applications in cleansing and cosmetic products.

Lipase-mediated resolution of racemic benzo-15-crown-5 ether derivatives

Racemic large secondary alcohol, 4′-hydroxyethyl-benzo-15-crown-5-ether, (±)-1 was kinetically resolved in high optical yield by asymmetric transformation with Candida antarctica lipase and Pseudomonas cepacia lipase.

Facile synthesis of 3-methoxycarbonyl-2,2,5,5-tetra-methylpyrrolidine-1-oxyl and derivatives

We have achieved an efficient alternative synthesis of blood-brain-barrier permeable nitroxyl radicals 3-methoxycarbonyl-2,2,5,5-tetra-methylpyrrolidine-1-oxyl (1a) and 3-ethoxycarbonyl-2,2,5,5-tetramethylpyrrolidine-1-oxyl (1b), which affords 1a and 1b in 65% isolated yields by four steps from 2,2,6.6-tetramethyl-4-piperidone (2), respectively. This protocol is applicable to the synthesis of 3-isopropoxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl (1c) and 3-carbonyl-2,2,5,5-tetramethylpyrro-lidine-1-oxyl (6).

Lubricant and Bactericidal Properties of Calcium Salts of Fatty Acids: Effect of Degree of Unsaturation

Fatty acids containing a C18 alkyl chain such as stearic acid (C18:0 fatty acid), oleic acid (C18:1 fatty acid) and linoleic acid (C18:2 fatty acid) are common emulsifiers in skin-care products and cosmetics and are also used in skin cleansers. In this study, we prepared calcium salts (Ca salts) of the above fatty acids to determine the effect of the degree of unsaturation of the alkyl chain. Scanning electron microscopy images and X-ray diffraction patterns show that C18:0 and C18:1 fatty acid Ca salts are plate-shaped, lamellar-crystalline powder, while C18:2 fatty acid Ca salt is amorphous powder. Therefore, C18:2 fatty acid Ca salt exhibits a lower lubrication ability than do C18:0 and C18:1 fatty acid Ca salts. In addition, the bactericidal ability against Staphylococcus aureus, Staphylococcus epidermidis and Propionibacterium acnes improved with increasing degree of unsaturation. These findings suggest that Ca salts of unsaturated fatty acids have potential applications in cleansing and cosmetic products.

Fluorescence spectroscopic study of α-chymotrypsin relevant to the enantioselectivity for optical resolution of amino acid esters in organic solvents

The fluorescence emission wavelength of α-chymotrypsin (CT) correlated with its enantioselectivity (E value) for the resolution of dl-tyrosine ethyl ester. The changes in the E value of the CT due to the changes in the solvent composition were closely related to its fluorescence properties (Δλem), which were most probably associated with the structural modification of the enzyme. A linear relationship was established between E value and Δλem in aqueous acetonitrile with high correlation coefficients (r=0.94).

Electrical communication between NAD-dependent enzyme and metal electrode using ferrocene-labeled NAD derivatives

The target N6-ferrocene substituted NAD derivatives (ferrocene-labeled NAD, Fc-NAD) were synthesized as an electron-relay NAD cofactor. The synthesized NAD derivatives possessed some biological activities as substrates in the alcohol dehydrogenase systems. The oxidation current depended on both addition of ethanol and spacer length of Fc-NAD.

First Synthesis and Properties of Calix[4]arene with Two Alternately Arranged Phloroglucinols and Two p-tert-Butylphenols

The Calix[4]arene 1 including two alternately arranged phloroglucinols and p-tert-butylphenols was synthesized via the “3+1” coupling procedure, and its pKa values were estimated to be 3–4 and 7.5, while those of the other six phenolic hydroxyls were approximately 11. Its UV–vis spectrum at pH 11 and 1H and 13C NMR spectra in NaOD-D2O solution (pH 12.8) showed a dramatic change like those of the phloroglucinol when compared to those in acidic or neutral solution, which suggests a change in the phloroglucinol moiety to the keto-form. During the solvent extraction for alkali metal species using 1, Li+ was only extracted in the low yield of 15% at pH 11. The cyclic voltammetry study of 1 was used to compare it with the phloroglucinol and p-tert-butylphenol. The redox potential of the corresponding two phloroglucinols was observed in 1.

Lipase-catalyzed enantioselective esterification of mono-aza-benzo-15-crown-5-ether derivatives in organic media.

For the purpose of developing a new chiral crown ether unit as a chiral synthon, three racemic mono azabenzo-15-crown-5-ethers, i.e. (R,S)-1-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-yl)-propan-2-ol, (R,S)-2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-yl)-1-phenyl-ethanol and (R,S)-1-[2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-ylmethyl)-phenyl]-ethanol were esterified with vinyl acetate using a lipase from Candida antarctica. The enzymatic acylation of alcohols produced monoacylated products. Two optically active azacrown ethers, (R)-propionic acid 1-methyl-2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-yl)-ethyl ester and (R)-acetic acid 1-[2-(6,7,9,10,12,13,15,16-octahydro-5,8,14,17-tetraoxa-11-aza-benzocyclopentadecen-11-ylmethyl)-phenyl]-ethyl ester were obtained within 48% and 36% yields, respectively and, at an enantiometric excess of over 99% in each case.