Polymerization of coordinated monomers. XV. 13C-NMR study on the alternating copolymers of methyl methacrylate with styrene

By the use of various metal halides methyl methacrylate and styrene were copolymerized to produce equimolar alternating sequences and different cotacticities. The ¹³C-NMR spectra of these copolymers were simple in comparison to those of random copolymers because of the fixed monomer sequence which yielded sharply split triplets for carbonyl, methoxy, and quaternary carbons. The relative intensities in these split peaks varied according to the metal halide used. A comparison of the intensities made it possible to obtain clear-cut and quantitative information on the methyl methacrylate-centered triad cotacticity of the copolymers. The spectral assignment with respect to the methoxy carbon was definitely justified by the combined use of partly relaxed Fourier transform and selective decoupling techniques. The spectrum of aromatic C₁ carbon in styrene units also split into three main peaks. From their relative intensities the splitting was attributed to styrene-centered triad cotacticity. The assignment of this carbon was compared with two other assignments made for random copolymers of methyl methacrylate with styrene; they were contradictory, however. Furthermore, an apparent discrepancy was observed between methyl methacrylate-and styrene-centered tactic triads of these alternating copolymers. The origin of this discrepancy suggests a close relationship with the copolymerization mechanism.     

Ternary Molecular Complex in the Alternating Copolymerization of Methyl Methacrylate with Styrene Using Stannic Chloride

The equimolar alternating copolymerization of methyl methacrylate (MMA) with styrene (St) in the presence of stannic chloride in toluene (Tl) is investigated kinetically. The concentrations of the ternary molecular complexes, [SnCl₄-MMA … St] and [SnCl₄-MMA … T1], are calculated by use of the formation constants of the ternary molecular complexes. The rates of copolymerization under photo-irradiation and with tri-n-butyl boron-benzoyl peroxide as an initiator are proportional to the 1.5th order and 1. Oth order, respectively, of the concentration of the ternary molecular complex [SnCl₄ · MMA … St]. The alternating copolymerization precedes the homopolymerization of the methyl methacrylate charged in excess. The alternating regulation of the copolymerization is ascribed to the homopolymerization of the ternary molecular complex from the kinetic results. The magnitudes of the shifts for     

Syntheses of prodelphinidin B1, B2, and B4 and their antitumor activities against human PC-3 prostate cancer cell lines

Total synthesis of prodelphinidin B1, B2, and B4 has been accomplished. The key step is Lewis acid-mediated equimolar condensations between an epigallocatechin and/or a gallocatechin nucleophile and an epigallocatechin and/or a gallocatechin electrophile. The antitumor effects of synthetic prodelphinidin B1–B4 against human PC-3 prostate cancer cell lines have been investigated. These compounds showed significant antitumor effects. Their activity seemed to be little bit stronger than EGCG and prodelphinidin B3, known antitumor agent.     

Synthesis of Murisolin, (15R, 16R, 19R, 20S)‐Murisolin A,and (15R, 16R, 19S, 20S)‐16,19‐cis‐Murisolin and Their Inhibitory Action with Bovine Heart Mitochondrial Complex I

The asymmetric total synthesis of murisolin, (15R, 16R, 19R, 20S)‐murisolin A, and (15R, 16R, 19S, 20S)‐16,19‐cis‐murisolin was performed by using an epoxy alcohol as a versatile chiral building block for synthesizing the stereoisomers of mono‐THF annonaceous acetogenins. The inhibitory activity of these murisolin compounds was examined with bovine heart mitochondrial complex I, and they showed almost the same activity.     

Investigation of Metal Ion Complexation of π-Coordinate Calixarene Derivatives by Electrospray-Ionization Mass Spectrometry

Complexation of π-coordinate calix[4]arene derivatives toward soft metal ions, silver and thallium (I) ions, has been studied by electrospray-ionization mass spectrometry. Competitive metal–ion complexation of three calix[4]arene derivatives demonstrates a significant effect of olefinic substituents and its location on the silver ion complexation, but there was no effect of them on the thallium ion complexation. The stability constants for the metal ion complexes of the calixarene derivatives in methanol have been successfully determined by a mass-spectrometric method using 18-crown-6 as the reference ligand.     

Analysis of Oxyluciferin Photoluminescence Pathways in Aqueous Solutions

We evaluated the pK_a values of oxyluciferin and its conjugate acids and bases theoretically with the help of experimental correction values, from which free energies for the first excited and the ground states of all the species were estimated. On the basis of these results, we calculated pH‐dependent absorption spectra, where the relative absorption intensities of various species strongly depend on photoexcitation energy, and we further analyzed the photoluminescence pathways of oxyluciferin in aqueous solutions with various pH. In the case of 350 nm photoexcitation, in particular, experiments have shown that dominant emission color is green and it attenuates with pH decreasing, while blue (3 < pH < 8) and red (pH < 3) emissions appear. Our present results clarify the pathways of these photoluminescence depending on the pH values and thus should be useful in further analyses of photoluminescence pathways for other photoexcitation wavelength in comparison with experiments.     

An envelope-like effect of infinitely many inequality constraints on second-order necessary conditions for minimization problems

A group of curves generates a new curve which is called an envelope. When one deals with a minimization problem with infinitely many inequality constraints, one must encounter an envelopelike effect caused by the constraints. In this paper we present second-order necessary conditions, which involve a new term besides the second derivative of the Lagrange function.We apply our results to minimizing problems of sup-type functions. One will observe in examples that the new term given in this paper explains well the behavior of the second directional derivative of the sup-type function.     

Release Behavior of Flavor Encapsulated CD in Slurry Solution Under Boiling Conditions

Cyclodextrin (CD) can control flavor release rate and protect the flavor from volatilization by the formation of inclusion complex with flavor compounds. However, the flavor release rate during cooking, particularly in boiling water has hardly been understood. In this study, flavor release rate of flavor encapsulated CD in slurry or turbid solution under boiling condition was investigated. The release rate constants of methyl caproate and d-limonene depended on the CD concentration, whereas, those of phenyl ethanol hardly did. The plot of a reciprocal number of apparent release rate constant to CD concentration for d-limonene stability constant under boiling condition was obtained. Stability constants for d-limonene in α-CD and β-CD were 185 and 38 M⁻¹, respectively. These stability constants were smaller than the order of 1000 M⁻¹ at room temperature. These results suggested that the addition of CD for protection of flavors in boiling water might have small effect in comparison to that at room temperature. The behavior of flavor release in the boiling water correlated well with the first-order release rate equation, which can be described by the film theory of the interfacial mass transfer.     

Electron spin resonance study on polymerization of conjugated dienes by homogeneous catalyst derived from n-butyl titanate and triethylaluminum

Polymerizations of butadiene, penta-1,3-diene, and isoprene with n-butyl titanate–triethylaluminum catalyst are examined by ESR measurements on the polymerization state. At Al/Ti molar ratios greater than 2.9 where the conjugated dienes are polymerized, the polymerization system of butadiene always gives an ESR signal with a g value of 1.983 and with a hyperfine structure of about 19 components. This signal does not appear at all, even in the presence of the monomer, at Al/Ti molar ratios smaller than two where butadiene is not polymerized. The absorption intensity of the signal coincides fairly well with the concentration of polymer chain calculated from polymer yield and the molecular weight. On the basis of these facts, the signal is assigned to the growing end of polybutadiene with this catalyst. The structure of the growing end is proposed to have both two substituted π-allyl groups and an alkoxy group in coordination to titanium (III), by analysis of the hyperfine structure. The polymerization system of penta-1,3-diene and that of isoprene respectively, give a new signal with a g value of 1.983, although the signal for the former monomer has a hyperfine structure of 11 components and that for the latter monomer has no hyperfine structure. A structure for the growing end in the polymerization of each of these two monomers analogous to that of the growing end of polybutadiene is proposed.