Structure and synthesis of FK409, a novel vasodilator isolated from Streptomyces as a semi-artificial fermentation product

The structures of FK409 (1), a semi-artificial fermentation product and its precursor (2) have been established on the basis of chemical and spectroscopic evidence and confirmed by conversion of 2 to 1 via a synchronous nitrosation-nitration reaction.     

Polydimethylsiloxane‐coated partitioning sample collection device for the precise quantification of polycyclic aromatic hydrocarbons in air

A novel partitioning collection device comprising a glass cartridge packed with poly(dimethylsiloxane)‐coated macroporous silica particles was developed for the precise quantification of polycyclic aromatic hydrocarbons in air. The analyte collection and elution performances achieved using different amounts of poly(dimethylsiloxane) coating were quantitatively evaluated. The sample retention power increased with increasing the coating, and more than 250 L of air could be collected without analyte breakthrough at a sampling temperature of 35°C. During the air collection, the moisture in the air was not retained on the particles due to the hydrophobic surface of the sorbent. A complete and rapid elution of the collected analytes from the device was accomplished by the passage of only 10 mL of acetone with ultrasonication for 1 min. The proposed method was successfully applied for the determination of airborne polycyclic aromatic hydrocarbons in tunnel air.     

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.     

α‐exomethylene lactone possessing acetal–ester linkage: Polymerization and postpolymerization modification for water‐soluble polymer

2,6‐Dimethyl‐5‐methylene‐1,3‐dioxa‐4‐one (DMDO), a cyclic acrylate possessing acetal–ester linkage, was obtained as a mixture of cis‐ and trans‐isomers (95:5) from Baylis–Hillman reaction of an aryl acrylate. The radical and anionic polymerizations of DMDO yielded the corresponding vinyl polymers without any side reactions such as cleavage of the acetal–ester linkage. The polymerization behaviors were significantly different from that of the acyclic acrylate, α‐(hydroxymethyl)acrylic acid, which was expected inactive against polymerization due to the steric hindrance around the vinylidene group by the α‐substituent. The acetal–ester linkage of the obtained polymer ( P1 ) was completely cleaved via acid hydrolysis to afford a water soluble polymer, P2 . © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 955–961     

π‐Electron Systems That Form Planar and Interlocked Anion Complexes and Their Ion‐Pairing Assemblies

Interactions between designed charged species are important for the ordered arrangements of π‐electron systems in assembled structures. As precursors of π‐electron anion units, new arylethynyl‐substituted dipyrrolyldiketone boron complexes, which showed anion‐responsive behavior, were synthesized. They formed a variety of receptor–anion complexes ([1+1] and [2+1] types) in solution, and the stabilities of these complexes were discussed in terms of their thermodynamic parameters. Solid‐state ion‐pairing assemblies of [1+1]‐ and [2+1]‐type complexes with countercations were also revealed by single‐crystal X‐ray analysis. In particular, a totally charge‐segregated assembly was constructed based on negatively and positively charged layers fabricated from [2+1]‐type receptor–anion complexes and tetrabutylammonium cations, respectively. Furthermore, the [1+1]‐type anion complex of the receptor possessing long alkyl chains exhibited mesophases based on columnar assembled structures with contributions from charge‐by‐charge and charge‐segregated arrangements, which exhibited charge‐carrier transporting properties.     

Anionic alternating copolymerization of α‐arylacrylates with methyl methacrylate: Effect of monomer sequence on fluorescence

Anionic polymerizations of acrylates possessing 1‐pyrenyl (Py1), 1‐naphthyl (Np1), 2‐naphthyl (Np2), and 2‐fluorenyl (Fl2) groups as α‐substituents were investigated as well as the properties of the obtained polymers. Py1 and Np1 did not undergo polymerization, whereas Np2 and Fl2, annulated α‐phenylacrylates at 3,4‐position of the phenyl group, afforded homo‐oligomers and alternating copolymers with methyl methacrylate (MMA). The oligomer of Fl2 [oligo(Fl2)] exhibited strong excimer emission in diluted solution. In contrast, dominant monomer emission was observed for the alternating copolymer with MMA [poly(Fl2‐co‐MMA)]. In the alternating copolymer, MMA units could function as spacers preventing the association of pendant fluorene moieties to suppress the excimer formation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2806–2814     

A facile method for generation of carbon oxide sulfide

Carbon oxide sulfide was easily generated upon heating of amine salts of carbamothioic acids at 85°C which were produced in situ from amines, carbon monoxide, and elemental sulfur in the presence of a catalytic amount of selenium under mild conditions.