Image formation by dyeing of copolymers bearing photogenerated acid and base groups with dye bath containing acid and basic dyes

Copolymers bearing photoacid generating groups and/or photobase generating groups were dyed after UV irradiation with a dye bath containing both an acid dye and a basic dye. Acetophenone O‐acryloyloxime (AAPO) was used as a monomer bearing acyloxyimino (AOI) group that generates a primary amino group upon irradiation, which is followed by hydrolysis. Phenacylsulfonylstyrene (PSSt) and 1,2,3,4‐tetrahydronaphthylideneamino p‐styrenesulfonate (NISS) were chosen as monomers having β‐keto sulfone (β‐KS) and iminosulfonate (IS) groups, respectively, which yielded acid groups when irradiated. Copolymers of AAPO and methyl methacrylate (MMA) were dyed with only the acid dye, and those of PSSt or NISS were dyed with only the basic dye after irradiation. AAPO‐PSSt‐MMA films became dyeable with the acid dye when irradiated for a short time and with the basic dye with further irradiation. However, AAPO‐NISS‐MMA copolymers showed the reverse dyeing behavior. IR spectra revealed that AOI groups were photochemically decomposed prior to the β‐KS groups for AAPO‐PSSt‐MMA, and AOI and IS groups decomposed simultaneously for AAPO‐NISS‐MMA. These results suggested the possibility of adsorption of different ionic dyes on the films by a change of irradiation time; in fact, color patterns could be obtained in a single staining process using the dye bath. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3043–3051, 2000     

Relative and absolute stereochemistry of quinadoline B, an inhibitor of lipid droplet synthesis in macrophages

New fungal metabolites, designated quinadolines A (1) and B (2), were isolated from culture broth of Aspergillus sp. FKI-1746, and their structures were elucidated by NMR spectroscopy. The complete relative and absolute stereochemistry of 2 was determined by X-ray crystallography and amino acid analysis using a chiral column. Quinadolines moderately inhibited lipid droplet synthesis in mouse macrophages.     

Exhaustive search of the configurational space of heat-shock protein 90 with its inhibitor by multicanonical molecular dynamics based dynamic docking

Multicanonical molecular dynamics based dynamic docking was used to exhaustively search the configurational space of an inhibitor binding to the N-terminal domain of heat-shock protein 90 (Hsp90). The obtained structures at 300 K cover a wide structural ensemble, with the top two clusters ranked by their free energy coinciding with the native binding site. The representative structure of the most stable cluster reproduced the experimental binding configuration, but an interesting conformational change in Hsp90 could be observed. The combined effects of solvation and ligand binding shift the equilibrium from a preferred loop-in conformation in the unbound state to an α-helical one in the bound state for the flexible lid region of Hsp90. Thus, our dynamic docking method is effective at predicting the native binding site while exhaustively sampling a wide configurational space, modulating the protein structure upon binding.     

Asymmetric total synthesis of (+)-K01-0509 B: determination of absolute configuration

K01-0509 B is a novel natural product which contains a carbamoylated cyclic guanidine. Our asymmetric total synthesis features a Sharpless asymmetric epoxidation and a stereocontrolled construction of the cyclic guanidine via an asymmetric nitroaldol reaction, followed by intramolecular SN2 cyclization. These reactions allowed the cyclic guanidine and the adjacent hydroxy group to be assembled, facilitating the asymmetric total synthesis and determination of the absolute stereochemistry of K01-0509 B. [reaction: see text].     

Estimation of molecular diffusivity in aqueous solution of acetonitrile by the Wilke-Chang equation

It was tried to estimate the molecular diffusivity (D(m)) of solutes in the mixtures of acetonitrile (ACN) and water by the Wilke-Chang equation. Although the information about association coefficient (α) is necessary for the calculation, it has never been proposed for ACN. The value of α was estimated as 1.37 from D(m) of benzene in ACN at 303 K experimentally measured by the peak parking method. The values of α, i.e. 2.6, 1.9, 1.5, and 1.0, which have respectively been proposed for four solvents, i.e. water, methanol, ethanol, and benzene, were correlated with two physico-chemical parameters of the solvents, i.e. solubility parameter and E(T) value. The α value for ACN was plotted around the two correlations, indicating its appropriateness. The values of D(m) calculated by the Wilke-Chang equation using the α value for ACN were compared with those measured by the peak parking method and the Aris-Taylor method in aqueous solutions of ACN. The mean square deviation of the estimation of D(m) was calculated as 8.8 and 14%. It was demonstrated that the Wilke-Chang equation can be used for estimating D(m) with a reasonable accuracy in the mixtures consisting of ACN and water.     

Preparation of poly(p‐oxybenzoyl) crystals using direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides

Poly(p‐oxybenzoyl) (POB) crystals were prepared by reaction‐induced crystallization during direct polymerization of p‐hydroxybenzoic acid in the presence of boronic anhydrides. Polymerizations were carried out at 300 °C in dibenzyltoluene at a concentration of 1% with three kinds of anhydrides of boronic acid such as 3,4,5‐trifluorophenylboronic acid (TFB), 4‐methoxyphenylboronic acid (MPB) and 4‐biphenylboronic acid (BPB). The POB crystals were formed as precipitates in the solution and the morphology was considerably influenced by both the structure of the boronic anhydride and its concentration (c_B). Needle‐like crystals were firmed in the presence of TFB anhydride (TFBA) at c_Bs of 5 and 10 mol % by the spiral growth of lamellae. Spherical aggregates of slab‐like crystals were formed at c_Bs from 50 to 100 mol %. The polymerization with MPB anhydride and BPB anhydride (BPBA) also yielded the needle‐like crystals at c_Bs of 50 and 5 mol %, respectively. The polymerization with TFBA at lower c_B was favorable to prepare the needle‐like crystal. Molecular weight was also influenced by the structure of the boronic anhydride and c_B. M_n increased generally with c_B and BPBA gave the highest M_n of 14.7 × 10³ at c_B of 100 mol %. The loose packing of the molecules in the crystal caused by the bulkiness of the end‐groups made the polymerization in the crystals more efficiently. Morphology and molecular weight of the POB crystals could be controlled by the chemical structure and the content of boronic anhydride. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis and photo-induced dissolution of polymers bearing imino sulfonate groups

Novel photosensitive polymers were synthesized by the copolymerization of methyl methacrylate and 1,2,3,4-tetrahydro-1-naphthylideneimino p-styrenesulfonate (NISS) and by the ternary polymerization of methyl methacrylate, methacrylic acid, and 9-fluorenylideneiminop-styrene-sulfonate (FISS). NISS and FISS units showed good sensitivity to light of wavelengths below 300 nm and below 366 nm, respectively. Although the polymers were insoluble in aqueous alkaline solutions, on irradiation with UV light they became soluble in aqueous alkaline solutions. A remarkable decrease in molecular weight of the polymers was observed during the photolysis of imino sulfonate groups incorporated into the polymers, which assisted the dissolution of the irradiated polymers.     

Degradation of crosslinked unsaturated polyesters in sub-critical water

The degradation of unsaturated polyesters crosslinked with styrene was performed in sub-critical water (SCW) in the absence and presence of organic additives. The unsaturated polyesters were de-crosslinked by hydrolysis of ester chains to form polystyrene derivatives on SCW treatment at 300 °C. With an increase in treating time, carboxylic acid groups in the polystyrene derivatives were turned into carboxylic anhydride groups in SCW. The de-crosslinking rate was much enhanced on SCW treatment in the presence of hydroxy compounds with a long alkyl chain and alkylamines, while carboxylic acids, benzenesulfonate salts, and quaternary ammonium salts were ineffective even though they had a long alkyl chain. The degree of de-crosslinking was reduced in the presence of diamines and amino acids because re-crosslinking at both ends of the additive molecules proceeded.     

Total synthesis of borrelidin

The total synthesis of borrelidin has been achieved. The best feature of our synthetic route is macrocyclization at C11-C12 for the construction of an 18-membered ring after esterification between two segments. A detailed examination of the macrocyclization led us to the samarium(II) iodide-mediated intramolecular Reformatsky-type reaction as the most efficient synthetic approach. The two key segments were synthesized through regioselective methylation, directed hydrogenation, stereoselective Reformatsky-type reaction, and MgBr2.Et2O-mediated chelation-controlled allylation.     

Anion-selective properties of alkali metal-free lead phosphate glasses containing silver chloride and their application in an ion-selective electrode

Alkali-free lead phosphate glasses containing silver chloride have been developed for anion responsive sensors. From measurements of the final glass compositions by electron probe microanalysis, it became clear that some of chloride ions in the glass bulk were not volatilized during the glass melting process. Compared with phosphate glasses containing silver oxide, the new glass electrodes containing silver chloride could respond more rapidly, although the response behaviour for anionic species were similar. From the electrode potential vs. time curve for the anionic species, the potential rapidly reached equilibrium when these concentrations varied from 10^?5 to 10^?2 M. The response times, t₉₅, to thiocyanate of the new glass electrode and the phosphate glass electrode containing silver oxide were 30 and 110 s, respectively. Moreover, the response time required for an initial potential change with a concentration jump of thiocyanate with the new glass electrode was found to be independent of the membrane thickness within about 2 mm and of the measuring temperature between 15 and 40°C. It is concluded that the diffusion process of species such as silver ion in the glass bulk does not take part in the initial part of the response behaviour.