Convenient synthesis of microspheres by self-assembly of random copolymers in supercritical carbon dioxide

A novel and convenient synthesis of microspheres was attained by molecular self-assembly of random copolymers in supercritical carbon dioxide. Poly{2-(perfluorooctyl)ethyl acrylate-ran-2-(dimethylamino)ethyl acrylate} random copolymers (P[POA-r-DAA]), with 7:3, 8:2, and 9:1 as the molar ratios of 2-(perfluorooctyl)ethyl acrylate (POA)/2-(dimethylamino)ethyl acrylate (DAA), were soluble in supercritical CO₂ and had their cloud points at about 75 bar higher than the critical pressure of CO₂. The CO₂ density at the cloud points decreased with an increase in temperature. Although the copolymers made a slight difference in the cloud point in the absence of perfluoroazelaic acid (PA), they made a marked difference in the presence of PA. The copolymer with a lower DAA content had a cloud point at lower CO₂ density. The scanning electron microscopy observation demonstrated that the copolymers produced microspheres in the presence of PA at 0.5 as PA/DAA in the heterogeneous state below the cloud points. The microspheres were unstable to pressure and changed to unspecific forms as a result of increasing the CO₂ pressure, although the microspheres were stable to temperature. The POA/DAA ratio in the copolymer had effect not only on the cloud point but also on the size of the microspheres. The copolymer with a lower DAA content formed smaller microspheres.     

A concise synthesis of furostifoline by tetrabutylammonium fluoride-promoted indole ring formation

Furostifoline, a furo[3,2-a]carbazole alkaloid, was synthesized in 10% overall yield in four steps from 2-acetyl-3-bromofuran. The key step of this synthesis was the 2-substituted indole formation with tetrabutylammonium fluoride (TBAF) from 2-(2-propenyl)-3-((2-ethoxycarbonylamino)phenylethynyl)furan, which was easily prepared from ethyl 2-ethynylphenylcarbamate with 3-bromo-2-(2-propenyl)furan by the Sonogashira reaction.     

Highly sensitive assay for alkaline and acid phosphatase activities by high-performance liquid chromatography with electrochemical detection

A highly sensitive and specific assay for alkaline and acid phosphatases in biological materials, such as plasma and saliva, has been established. Phenol, formed enzymatically from the substrate phenylphosphate, was determined by high-performance liquid chromatography with electrochemical detection. The retention time of phenol was 7 min and no other peaks were observed. The method is rapid and sensitive with a detection limit for phenol of as little as 5 pmol. Thus, as little as 0.5 microliter of rat plasma or 10 microliters of human saliva is required for both alkaline and acid phosphatase assays. The assay is accurate and reproducible. Using this assay, alkaline and acid phosphatase activities in saliva were found to be 1.12 +/- 0.12 nmol/min/ml and 9.79 +/- 1.23 nmol/min/ml, respectively. This new assay method should be applicable to extremely small biological samples.     

Simple assay procedure for tyrosine hydroxylase activity by high-performance liquid chromatography employing coulometric detection with minimal sample preparation

A simple assay procedure for tyrosine hydroxylase activity in crude tissue samples was devised that requires minimal sample preparation and use of high-performance liquid chromatography with coulometric electrochemical detection. After incubation of enzyme samples, such as human brain homogenates or rat pheochromocytoma PC12h cells, with L-tyrosine and a tetrahydropterin cofactor, in the presence or absence of p-bromobenzyloxyamine, an inhibitor of aromatic L-amino acid decarboxylase, the reaction was terminated by addition of an equal volume of 0.1 M perchloric acid. For quantitation of L-DOPA produced, the sample was centrifuged, filtered and directly applied to the chromatographic apparatus connected to a coulometric electrochemical detector. This method makes redundant a time-consuming step in the previous methods, purification and concentration of L-DOPA or dopamine using alumina. The reaction conditions for the assay of tyrosine hydroxylase activity in brain homogenates and PC12h cells were re-examined by this method. Both tyrosine hydroxylase samples required a naturally occurring cofactor, (6R)-L-erythro-5,6,7,8-tetrahydrobiopterin [(6R)BH4], catalase and NSD-1055 for the full activity, and tyrosine hydroxylase in human brain homogenates required Fe2+ ions for its full activity. (6R)BH4 proved to be a more effective cofactor than a synthetic cofactor, (6RS)-methyl-5,6,7,8-tetrahydropterin, which is commonly used for this assay.     

Sesquiterpenoid derivatives from Ferula ferulaeoides [correction of ferulioides]. V

Nine novel prenyl-dihydrofurocoumarin-type sesquiterpenoid derivatives, 2,3-dihydro-7-hydroxy-2R*,3R*-dimethyl-2-[4,8-dimethyl-3(E),7-nonadienyl]-furo[3,2-c]coumarin, 2,3-dihydro-7-hydroxy-2S*,3R*-dimethyl-2-[4,8-dimethyl-3(E),7-nonadien-6-onyl]-furo[3,2-c]coumarin, 2,3-dihydro-7-hydroxy-2S*,3R*-dimethyl-2-[4-methyl-5-(4-methyl-2-furyl)-3(E)-pentenyl]-furo[3,2-c]coumarin, 2,3-dihydro-7-hydroxy-2R*,3R*-dimethyl-2-[4-methyl-5- (4-methyl-2-furyl)-3(E)-pentenyl]-furo[3,2-c]coumarin, 2,3-dihydro-7-methoxy-2S*,3R*-dimethyl-2-[4,8-dimethyl-3(E),7-nonadienyl]-furo[3,2-c]coumarin, 2,3-dihydro-7-methoxy-2R*,3R*-dimethyl-2-[4,8-dimethyl-3(E),7-nonadienyl]-furo[3,2-c]coumarin, 2,3-dihydro-7-methoxy-2S*,3R*-dimethyl-2-[4,8-dimethyl-3(E),7-nonadien-6-onyl]-furo-[3,2-c]coumarin, and 2,3-dihydro-7-methoxy-2S*,3R*-dimethyl-2-[4-methyl-5-(4-methyl-2-furyl)-3(E)-pentenyl]-furo[3,2-c]coumarin, were isolated from the roots of Ferula ferulaeoides [corrected]. The structures were established by comprehensive spectral analysis. The biosynthetic pathway leading to these prenyl-furocoumarin-type sesquiterpenoids is proposed based on their structures.     

Liquid—liquid distribution of ion associates of tetraiodopalladate(II) with quaternary ammonium counter ions

The distribution behaviour of ion association of Pdl^2?₄ with ten quaternary ammonium cations between chloroform and an aqueous phase was examined and extraction constants (log K_ex) were determined. Linear relationships between log K_ex and the number of methylene groups in the quaternary ammonium ions were observed. Quantitative extraction of palladium was achieved with Zeph⁺ or TBA⁺; the molar absorptivity was 2.5 × 10⁴ l mol^?1 cm^?1 at 344 nm. The effect of other ions on the spectrophotometric determination of palladium, based on their extraction, is reported.     

Copper-Catalyzed Coupling Reaction of Secondary Alkyl 2-Pyridinesulfonates with Alkyl Lithium-Based Reagents

The Cu(OTf)₂-catalyzed alkyl–alkyl coupling reaction of a secondary substrate MeCH(OSO₂Py)CH₂CH₂C₆H₄(4-OMe) with a nBuLi-based reagent prepared by transmetalation with MgBr₂ ⋅ THF₃ in THF produced a coupling product in 74 % yield. The use of soluble MgBr₂ ⋅ THF₃ in THF was required for this reaction. This method was applied to sBuLi and Ph(CH₂)₄Li. In contrast, transmetalation of MeLi with soluble MgCl₂ ⋅ THF₂ in THF produced the Me reagent, which was reactive for the coupling reaction. The reaction proceeded with inversion of the stereogenic carbon. Furthermore, (S)-14-methyloctadecan-2-one, a sex pheromone produced by lichen moths, was synthesized.     

Biomimetic oxidation of 2-methylimidazole derivative with a chemical model system for cytochrome P-450

A chemical model system for cytochrome P-450, consisting of tetraphenylporphyrin manganese chloride (TPPMnCl) and iodosylbenzene, efficiently oxidized 2-methylimidazole to 2-methylimidazolone. This system was next applied to 4-(2-methyl-1-imidazolyl)-2,2-diphenylbutyramide, a muscarinic acetylcholine receptor antagonist under clinical trial, affording the previously unisolated imidazole ring 5-mono-oxidized derivative that is considered to be the precursor of the main metabolites. This system, which is superior to the copper-ascorbate system, should be applicable to in vitro studies of various drugs containing the 2-methylimidazole moiety.     

Synthesis of meso-Free Decaphyrin(1.1.1.1.1.1.1.1.1.1) by a Hydrodebromination Protocol; Aromaticity and Solvent-Polarity Dependent Conformational Change

A meso-free β-bromodecaphyrin has been constructed by [2+3+2+3] type acid-catalyzed cross-condensation and subsequent oxidation. Hydrodebromination of this tetrabromodecaphyrin with NaBH₄ in the presence of TMEDA and palladium catalyst afforded β-unsubstituted doubly meso-free [46]decaphyrin(1.1.1.1.1.1.1.1.1.1) as the first example of β-unsubstituted meso-free regular expanded porphyrins with the number of pyrrole units larger than eight. It exhibits distinct aromaticity originating from its 46π-conjugated electronic circuit and flexible conformational change between non-twisted and doubly twisted forms depending on the solvent-polarity. Their distinct conformations have been analyzed by combined experimental and theoretical investigations.