Chiral Template-Directed Regio‑, Diastereo‑, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium–Carboxylate Salt Bridge Formation

A series of optically active amidine dimers composed of <i>m</i>-terphenyl backbones joined by a variety of linkers, such as achiral and chiral <i>p</i>-phenylene and chiral amide linkers, were synthesized and used as templates for the regio- (head-to-tail (HT) or head-to-head (HH)), diastereo- (<i>anti</i> or <i>syn</i>), and enantioselective [4 + 4] photocyclodimerization of an achiral <i>m</i>-terphenyl-based carboxylic acid monomer bearing a prochiral 2-substituted anthracene at one end (<b>1</b>) through complementary amidinium–carboxylate salt bridges. The amidine dimers linked by <i>p</i>-phenylene linkages almost exclusively afforded the chiral <i>syn</i>-HT and <i>anti</i>-HH dimers at 25 °C, while those joined by amide linkers produced all four dimers. The <i>p</i>-phenylene-linked templates tended to enhance the <i>syn</i>-HT-photodimer formation at high temperatures with no significant changes in the product enantiomeric excess (ee), while the <i>anti</i>-HH-photodimer formation remarkably increased with the decreasing temperature accompanied by a significant enhancement of the product ee up to −86% at −50 °C. Temperature-dependent inversion of the chirality of the <i>anti</i>-HH dimer was observed when the chiral phenylene-linked amidine dimer was used and the product ee was changed from 22% at 50 °C to −86% at −50 °C. A similar enhancement of the enantioselectivity of the <i>anti</i>-HH dimer was also observed for the chiral amide-linked template, producing the <i>anti</i>-HH dimer with up to −88% ee at −50 °C. The observed difference in the regio-, diastereo-, and enantioselectivities due to the difference in the linker structures of the amidine dimers during the template-directed photodimerization of <b>1</b> was discussed on the basis of a reversible conformational change in the amidine dimers complexed with <b>1</b>

Cobalt(II)-Salen-Linked Complementary Double-Stranded Helical Catalysts for Asymmetric Nitro-Aldol Reaction

Double-helical, bimetallic chiral Co­(II)-salen complexes stabilized by chiral amidinium–carboxylate salt bridges efficiently catalyzed the asymmetric nitro-aldol (Henry) reaction, producing products with up to an 89% enantiomeric excess (ee); the reactivity and enantioselectivity were higher than those catalyzed by the corresponding single strands. The key role of the chiral double-helical framework for the supramolecular bimetallic catalysis has been revealed by a double-helical catalyst carrying achiral Co­(II)-salen units that promoted the Henry reaction, yielding the product with a 50%–45% ee, while the corresponding single strands showed poor or no enantioselectivity

Cobalt(II)-Salen-Linked Complementary Double-Stranded Helical Catalysts for Asymmetric Nitro-Aldol Reaction

Double-helical, bimetallic chiral Co­(II)-salen complexes stabilized by chiral amidinium–carboxylate salt bridges efficiently catalyzed the asymmetric nitro-aldol (Henry) reaction, producing products with up to an 89% enantiomeric excess (ee); the reactivity and enantioselectivity were higher than those catalyzed by the corresponding single strands. The key role of the chiral double-helical framework for the supramolecular bimetallic catalysis has been revealed by a double-helical catalyst carrying achiral Co­(II)-salen units that promoted the Henry reaction, yielding the product with a 50%–45% ee, while the corresponding single strands showed poor or no enantioselectivity

Donor-Substituted Octacyano[4]dendralenes: Investigation of π‑Electron Delocalization in Their Radical Ions

Symmetrically and unsymmetrically electron-donor-substituted octacyano[4]­dendralenes were synthesized and their opto-electronic properties investigated by UV/vis spectroscopy, electrochemical measurements (cyclic voltammetry (CV) and rotating disk voltammetry (RDV)), and electron paramagnetic resonance (EPR) spectroscopy. These nonplanar push–pull chromophores are potent electron acceptors, featuring potentials for first reversible electron uptake around at −0.1 V (vs Fc⁺/Fc, in CH₂Cl₂ + 0.1 M <i>n</i>-Bu₄NPF₆) and, in one case, a remarkably small HOMO–LUMO gap (Δ<i>E</i> = 0.68 V). EPR measurements gave well-resolved spectra after one-electron reduction of the octacyano[4]­dendralenes, whereas the one-electron oxidized species could not be detected in all cases. Investigations of the radical anions of related donor-substituted 1,1,4,4-tetracyanobuta-1,3-diene derivatives revealed electron localization at one 1,1-dicyanovinyl (DCV) moiety, in contrast to predictions by density functional theory (DFT) calculations. The particular factors leading to the charge distribution in the electron-accepting domains of the tetracyano and octacyano chromophores are discussed

Donor-Substituted Octacyano[4]dendralenes: Investigation of π‑Electron Delocalization in Their Radical Ions

Symmetrically and unsymmetrically electron-donor-substituted octacyano[4]­dendralenes were synthesized and their opto-electronic properties investigated by UV/vis spectroscopy, electrochemical measurements (cyclic voltammetry (CV) and rotating disk voltammetry (RDV)), and electron paramagnetic resonance (EPR) spectroscopy. These nonplanar push–pull chromophores are potent electron acceptors, featuring potentials for first reversible electron uptake around at −0.1 V (vs Fc⁺/Fc, in CH₂Cl₂ + 0.1 M <i>n</i>-Bu₄NPF₆) and, in one case, a remarkably small HOMO–LUMO gap (Δ<i>E</i> = 0.68 V). EPR measurements gave well-resolved spectra after one-electron reduction of the octacyano[4]­dendralenes, whereas the one-electron oxidized species could not be detected in all cases. Investigations of the radical anions of related donor-substituted 1,1,4,4-tetracyanobuta-1,3-diene derivatives revealed electron localization at one 1,1-dicyanovinyl (DCV) moiety, in contrast to predictions by density functional theory (DFT) calculations. The particular factors leading to the charge distribution in the electron-accepting domains of the tetracyano and octacyano chromophores are discussed

Characterization of transplanted human VPC-derived vascular cells.

<p>a) Flow cytometric analysis of cell surface markers on expanded human VPC-derived VEGF-R2⁺VE-cadherin⁺ cells ( = EC). b) Immunofluorescence image of CD31 (green) and αSMA (red) with nuclear staining (blue) in expanded EC. Scale bar: 100 µm. c) Immunostaining of mural cell markers (brown) with hematoxyline counter-staining of expanded VPC-derived VEGF-R2⁺VE⁻cadherin- cells ( = MC). Scale bar: 100 µm. d, e) RT-PCR analysis of mural cell (d) and skeletal/cardiac specific (e) markers in human VPC-derived vascular cells.</p

Fluorescence-conjugated monoclonal antibodies used for FACS analysis

<p>Fluorescence-conjugated monoclonal antibodies used for FACS analysis</p

Primers for reverse transcription-polymerase chain reaction

1<p>Ref. 21.</p>2<p>We used a single pair of PCR primers that cover the sequence specific to SM2, because these two isoforms are produced from a single gene by alternative splicing.</p>3<p>Ref. 22.</p>4<p>Ref. 23.</p

Smooth muscle specific antibodies used for analysis

<p>Smooth muscle specific antibodies used for analysis</p

Incorporated human VPC-derived vascular cells at the sites of vascular regeneration.

<p>a) Transplanted CM-DiI (red) labeled pEPC or VPC-derived vascular cells in ischemic hindlimbs at day 7 were detected by the fluorescence stereomicroscope. Scale bar: 500 µm. b, c) Immunostaining of frozen sections harvested from ischemic limb tissues at day 14. Fluorescence staining of GSL I-isolectin B4 (green) and human CD31 (blue) with nuclear staining (red) in human VPC-derived EC+MC (b), pEPC, and uEPC (c) transplanted mice. Scale bar: 20 µm. d) Immunostaining of αSMA (green)/human SM1 (blue) with nuclear staining (red) in human VPC-derived EC+MC-transplanted mice at day 14. Scale bar: 20 µm.</p