Porphyrin-Stabilized Nitrenium Dication

An azepine-fused Ni^II-porphyrin dimer was synthesized by oxidative amination of β–β linked Ni^II-porphyrin dimer, and its N-aryl congener was synthesized by twofold Buchwald–Hartwig amination of β-to-β linked and dichlorinated Ni^II-porphyrin dimer. Oxidation of the NH congener gave neutral aminyl radical and nitrenium ion successively in a similar manner to the previously reported NH-bridged Ni^II-porphyrin dimer. Oxidation of the N-aryl congener afforded formal nitrenium dication in a single-step two-electron oxidation. Stable nitrenium dications that are isoelectronic to neutral trivalent boron compounds and tertiary carbocations are rare. The chemical stability of the nitrenium dication was improved by chlorine substitution at the most reactive β-position. The structural, optical, magnetic, electrochemical properties of these compounds were fully characterized.     

An Optically and Thermally Switchable Electronic Structure Based on an Anthracene–BODIPY Conjugate

An optically and thermally responsive boron dipyrromethene (BODIPY) dye, namely, meso‐2‐(9,10‐dihydro‐9,10‐ethanoanthracene‐11,12‐dione) (DK)‐linked, bicyclo[2.2.2]octadiene (BCOD)‐fused BODIPY ( BCOD‐DK ), was synthesized. The weakly luminous structure of BCOD‐DK can be changed quantitatively to that of the strongly fluorescent BODIPY BCOD‐Ant by optical excitation at the DK unit, which induces double decarbonylation of the DK unit to give an anthracene unit. The solvent effect on the fluorescence properties of BCOD‐DK suggests that the dramatic change in fluorescence intensity is controlled by intramolecular electron transfer from the BODIPY moiety to the meso‐DK substituent. BCOD‐DK is converted to meso‐ DK benzene‐fused BODIPY ( Benzo‐DK ) by heating at 220 °C with 64–70 nm redshift of absorption and fluorescence peaks without changing the fluorescence quantum yield of Φ_F=0.08 in dichloromethane. Benzo‐DK can be converted to strongly fluorescent meso ‐ anthracene benzene‐fused BODIPY Benzo‐Ant by optical excitation. Thus, BCOD‐DK can show four different optical performances simply by irradiation and heating, and hence may be applicable for optical data storage and security data encryption.     

Three new nortriterpene glycosides and two new triterpene glycosides from the bulbs of Scilla scilloides

Three new norlanostane-type triterpene glycosides, scillanostasides A, B, and C, and two new lanostane-type triterpene glycosides, scillanostasides D and E, were isolated from the bulbs of Scilla scilloides Druce (Liliaceae) along with one known norlanostane-type triterpene heptaglycoside, scillascilloside G-1. Their chemical structures were determined on the basis of spectroscopic data as well as chemical evidence.     

Discrimination of Isobaric Leu/Ile Residues by MALDI In-Source Decay Mass Spectrometry

MALDI in-source decay (ISD) has been used for top-down sequencing of proteins. The use of the matrix 1,5-diaminonapthalene (1,5-DAN) gave abundant w ions, which are formed from the unimolecular dissociation of z? radical fragments via α cleavage reaction and thus help identify which of the isobaric amino acids, Leu or Ile, is present. The high abundance of w ions in MALDI-ISD with 1,5-DAN results from the low collision rate in the MALDI plume. MALDI-ISD with 1,5-DAN appears to be an useful method for the top-down sequencing of proteins, including discrimination of Leu and Ile near the C-terminal end.      

Creation of magnetic cerasomes through electroless plating and their manipulation using external magnetic fields

Magnetic cerasome, an artificial cell membrane having ultrathin magnetic metal layers on the surface, was prepared through electroless plating of magnetic metal alloy onto an organic–inorganic vesicular nanohybrid “cerasome.” Morphological and functional characteristics of the magnetic cerasome were evaluated using various physical measurements: scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, electron tomography, and vibrating sample magnetometry. The results proved that high morphological stability of the cerasome was important for constructing the magnetic lipid vesicle and that insertion of an alkylated metal ligand into the cerasome was essential to the magnetic metal alloy deposition on the cerasome surface. Fluorescence microscopic observations revealed that the magnetic cerasomes were collected reversibly on the slide glass surface and manipulated depending on external motion of a magnet. The potential use of the magnetic cerasomes as a novel vesicular nanohybrid is also described in this report.     

Negative-mode MALDI mass spectrometry for the analysis of pigments using tetrathiafulvalene as a matrix

Negative-mode matrix-assisted laser desorption/ionization-mass spectrometry (MALDI-MS) analysis of industrial pigments was performed using tetrathiafulvalene (TTF), an electron donating compound, as a matrix. Comparing with other matrices such as tetracyanoquinodimethane (TCNQ), dithranol, 2-hydroxy-6-nitroaniline (HNA), and harmine hydrochloride, the most abundant analyte ions were produced by the TTF as radical or deprotonated anions. In addition, fragment ions in the negative mode of operation are also found to be much less abundant than those in the positive mode of operation.     

Catalytic asymmetric conjugate reduction with ethanol: A more reactive system Pd(II)-Pr-DUPHOS complex with molecular sieves 4A

We describe herein the catalytic asymmetric conjugate reduction of α,β-unsaturated carbonyl compounds using a novel cationic Pd-ⁱPr-DUPHOS complex. In this reaction, EtOH worked well as a solvent and a reducing agent, and the reaction was completed within several hours in most cases to afford the reduced compounds almost quantitatively with modest to good enantioselectivity (up to 72% ee). It was found that the Pd-ⁱPr-DUPHOS complex was more reactive than the previously reported Pd-BINAP complex when molecular sieves 4A was added as an additive. Based on an X-ray structural analysis of [Pd{(S,S)-ⁱPr-duphos}](OTf)₂ complex, a working hypothesis of the reaction mechanism is also described.     

Systemically Injectable Enzyme‐Loaded Polyion Complex Vesicles as In Vivo Nanoreactors Functioning in Tumors

The design and construction of nanoreactors are important for biomedical applications of enzymes, but lipid‐ and polymeric‐vesicle‐based nanoreactors have some practical limitations. We have succeeded in preparing enzyme‐loaded polyion complex vesicles (PICsomes) through a facile protein‐loading method. The preservation of enzyme activity was confirmed even after cross‐linking of the PICsomes. The cross‐linked β‐galactosidase‐loaded PICsomes (β‐gal@PICsomes) selectively accumulated in the tumor tissue of mice. Moreover, a model prodrug, HMDER‐βGal, was successfully converted into a highly fluorescent product, HMDER, at the tumor site, even 4 days after administration of the β‐gal@PICsomes. Intravital confocal microscopy showed continuous production of HMDER and its distribution throughout the tumor tissues. Thus, enzyme‐loaded PICsomes are useful for prodrug activation at the tumor site and could be a versatile platform for enzyme delivery in enzyme prodrug therapy.