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131.
Shoma Mizutani Kenta Komori Tohru Taniguchi Kenji Monde Kouji Kuramochi Kazunori Tsubaki 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2016,128(33):9705-9708
A biomimetic synthesis of naturally occurring lactams rubrobramide, flavipucine, and isoflavipucine is described. The key step is a regioselective Darzens reaction between isobutyl glyoxal and an α‐bromo‐β‐ketoamide. The construction of the core tricyclic ring system of rubrobramide was achieved by a cascade reaction in a single step from an α,β‐epoxy‐γ‐lactam. Furthermore, the absolute configuration of naturally occurring (+)‐rubrobramide was determined by vibrational circular dichroism. (±)‐Flavipucine and (±)‐isoflavipucine were synthesized from an epoxyimide, which was prepared by reaction of isobutyl glyoxal with a protected α‐bromo‐β‐ketoamide. Deprotection of the epoxyimide and formation of the pyridone ring gave (±)‐flavipucine, which was converted into (±)‐isoflavipucine by thermal isomerization. 相似文献
132.
4-(Difluoroiodo)toluene-induced domino lambda(3)-iodanation-1,4-halogen shift-ring enlargement-fluorination reaction of 5-halopentynes with a four-, five-, or six-membered carbocycle afforded the ring-expanded (E)-delta-fluoro-beta-halovinyl-lambda3-iodanes stereoselectively in high yields, probably via the intermediacy of five-membered halonium ions. Use of internal alkynes makes it possible to synthesize tetrasubstituted beta-halovinyl-lambda(3)-iodanes with defined stereochemistry. 相似文献
133.
Matsuoka D Iwata T Zikihara K Kandori H Tokutomi S 《Photochemistry and photobiology》2007,83(1):122-130
Phototropin is a blue-light photoreceptor in plants that mediates phototropism, chloroplast relocation, stomata opening and leaf expansion. Phototropin molecule has two photoreceptive domains named LOV1 (light-oxygen-voltage) and LOV2 in the N-terminus and a serine/threonine kinase domain in the C-terminus, and acts as a blue light-regulated kinase. Each LOV domain binds a flavin mononucleotide as a chromophore and undergoes unique cyclic reactions upon blue-light absorption that comprises a cysteinyl-flavin adduct formation through a triplet-excited state and a successive adduct break to revert to the initial ground state. The molecular reactions underlying the photocycle are reviewed and one of the probable molecular schemes is presented. Adduct formation alters the secondary protein structure of the LOV domains. This structural change could be transferred to the linker between the kinase domain and involved in the photoregulation of the kinase activity. The structural changes as well as the oligomeric structures seem to differ between LOV1 and LOV2, which may explain the proposed roles of each domain in the photoregulation of the kinase activity. The photoregulation mechanism of phototropin kinase is reviewed and discussed in reference to the regulation mechanism of protein kinase A, which it resembles. 相似文献
134.
135.
136.
The reaction of a mixture of 2-(1-naphthyl)benzothiazoline (HL1) and 2,6-diphenylbenzo[1,2-d:4,5-d']bisthiazoline (H3L2) with nickel(II) acetate tetrahydrate yielded three kinds of square-planar nickel(II) complexes: one nickel(II) complex with innocent ligands ([Ni(L1)2] (1c)) and two nickel(II) complexes with non-innocent ligands ([Ni(L1-L1)] (1a) and [Ni(L1-L2)] (1b)). The complex 1c has two bidentate-N,S ligands, which are formed via ring opening of HL1. On the other hand, the two complexes 1a and 1b contain a tetradentate-N2S2 ligand, which is created via ring opening of HL1 and H3L2, followed by bond formation between imino carbon atoms. Complexes 1a and 1b show very intense absorptions in the near-infrared (NIR) region, characteristic of square-planar complexes with non-innocent ligands. The third nickel(II) complex having a non-innocent tetradentate-N2S2 ligand ([Ni(L2-L2)] (2)) was prepared from H3L2 and nickel(II) acetate tetrahydrate. The electronic spectrum of 2 exhibits a very intense absorption at 981 nm (epsilon = 3.6 x 10(4) M-1 cm-1), which is significantly red-shifted compared with those of 1a (837 nm and 4.4 x 10(4) M-1 cm-1) and 1b (885 nm and 4.5 x 10(4) M-1 cm-1), indicating the presence of an extended pi delocalization. The reaction of 2,6-bis(3,5-dichlorophenyl)benzo[1,2-d:4,5-d']bisthiazoline (H3L3) with nickel(II) acetate tetrahydrate also led to the formation of a nickel(II) complex with a non-innocent ligand ([Ni(L3-L3)] (3)). While complex 3 is analogous to 2, its electrical conductivity is much higher than that of 2. The molecular structures of 1b, 1c, 2, and 3 were determined by X-ray crystallography. 相似文献
137.
Yasuhiro Tanoue Akari Hara Norihisa Kai Kazunori Sakata Mamoru Hashimoto Takeshi Nagai 《Journal of heterocyclic chemistry》2007,44(5):1135-1137
138.
Hidenori Hanaoka Masaaki Nabika Kazunori Yanagi Akio Imai 《Journal of organometallic chemistry》2007,692(21):4717-4724
A series of titanium complexes bearing a SiMe2-bridged phenoxy-cyclopentadienyl ligand were synthesized and characterized, and their catalytic behavior for copolymerization of ethylene and 1-hexene was investigated. Treatment of dimethylsilyl(2,3,4,5-tetramethylcyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)-titanium dichloride (1) with appropriate nucleophiles afforded dimethoxy complex 2, dimethyl complex 3, and dibenzyl complex 4. Standing a toluene solution of 2 in air afforded a dinuclear μ-oxo complex 5 as a single isomer. 1,3-Diene complexes 6-8 were prepared by reaction of 1 with the corresponding 1,3-dienes in the presence of 2 equiv. of n-BuLi. X-ray analysis of 1,4-diphenyl-1,3-butadiene complex 6 revealed that the diene ligand coordinates to titanium in s-cis fashion with a prone orientation. The newly prepared titanium complexes were applied to copolymerization of ethylene and 1-hexene upon activation with AliBu3 and [C6H5NMe2H][B(C6F5)4]. It was found that the alkyl complexes 3-4 and the diene complexes 6-8 showed higher activities than 1 at elevated temperature. 相似文献
139.
Park JS Akiyama Y Yamasaki Y Kataoka K 《Langmuir : the ACS journal of surfaces and colloids》2007,23(1):138-146
Novel thermosensitive polyion complex (PIC) micelles were prepared in an aqueous medium based on the complexation of a pair of oppositely charged block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(amino acid)s (PiPrOx-b-PAA), containing thermosensitive PiPrOx segments. The controlled synthesis of PiPrOx-b-PAA was achieved via the ring-opening anionic polymerization of N-carboxyanhydrides (NCA) of either eta-benzyloxycarbonyl-l-lysine (Lys(Z)-NCA) or beta-benzyl-l-aspartate (BLA-NCA) with omega-amino-functionalized PiPrOx macroinitiators and the subsequent deprotection reaction under acidic or basic conditions. Gel permeation chromatography (GPC) and 1H NMR spectroscopy revealed that the syntheses of two block ionomers, poly(2-isopropyl-2-oxazoline)-b-poly(l-lysine) [PiPrOx-P(Lys)] and poly(2-isopropyl-2-oxazoline)-b-poly(aspartic acid) [PiPrOx-P(Asp)], proceeded almost quantitatively to give samples with a narrow molecular weight distribution (Mw/Mn = 1.2). The mixing of these two oppositely charged block ionomers in an aqueous medium led to the spontaneous formation of PIC micelles, which was confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The PIC micelles were spherical particles with a narrow distribution in the range of the measured concentration (0.125-1 mg/mL) and were stable without any secondary aggregates. Furthermore, the PIC micelles had a constant cloud-point temperature (Tcp) of approximately 32 degrees C under physiological conditions regardless of the total concentration, suggesting that the concentration factor is almost negligible with respect to the Tcp of the micelles presumably because of the increased local concentration of the PiPrOx segments in the shell layer. These PIC micelles have a promising application as a size-regulated smart nanocontainer loading charged compounds as well as bearing a thermosensitive outer shell that is useful for physical affinity control. 相似文献
140.
Functional and site-specific macromolecular micelles as high potential drug carriers 总被引:4,自引:0,他引:4
Sandrine Cammas-Marion Teruo Okano Kazunori Kataoka 《Colloids and surfaces. B, Biointerfaces》1999,16(1-4):207-215
Since several years, macromolecular micelles based on amphiphilic block copolymers have attracted much interest as drug carriers. These micelles show a long term blood circulation time resulting from their small diameter and the steric repulsion created by the poly(ethylene oxide) chains which constitute micelle corona, as well as from their high thermodynamic stability. Besides this long term blood circulation time generating a passive targeting, an active targeting, chemical or physical affinity targeting, might allow the preparation of more efficient drug carriers. In order to obtain such double targeting properties, we have prepared two kinds of macromolecular micelles. The first one is based on amphiphilic poly(ethylene oxide)/poly(β-benzyl
-aspartate) ---PEO/PBLA--- block copolymers having hydroxy groups at the free end of PEO chains. As a result of their structure, such micelles have hydroxy groups on their outer-shell which can be further modified in order to introduce a targeting moiety (sugar, etc.). The characteristics (diameter, critical micellar concentration (cmc), drug loading capacity) have been determined. Moreover, doxorubicin loaded -hydroxy PEO/PBLA micelles have been shown to be slightly more cytotoxic than the corresponding -methoxy PEO/PBLA micelles. The second type of micelles is based on thermosensitive amphiphilic poly(N-isopropyl acrylamide)/polystyrene ---PIPAAm/PSt--- block copolymers. Such micelles have a small diameter and a low cmc in addition to thermosensitivity properties which are similar to those of PIPAAm. 相似文献