12. Triethylborane (first update)
Takehiko Yoshimitsu, Handbook of Reagents for Organic Synthesis; Reagents for Direct Functionalization of C-H Bonds. Ed by Fuchs, P. L. Wiley-VCH, pp.351-356 (2006).
11. Bromoallenes as Allyl Dication Equivalents in the Presence or Absence of Palladium(0): Direct Construction of Bicyclic Sulfamides Containing Five- to Eight-membered Ring by Tandem Cyclization of Bromoallenes
H. Hamaguchi, S. Kosaka, N. Fujii, H. Ohno, T. Tanaka, Chem. Eur. J., 13, 1692-1708 (2007).
Abstract: Based on our recent discovery that bromoallenes can act as allyl dication equivalents in the presence of a palladium catalyst and alcohol, we investigated tandem cyclization of bromoallenes bearing a sulfamide group. It is found that some bromoallenes act as allyl dication equivalents even in the absence of a palladium(0) catalyst to afford cyclosulfamides containing five- or six-membered rings. While the palladium-free cyclization is dependent on the substrate structure affording the bicyclic sulfamides through the first cyclization onto the proximal or central carbon of the bromoallenes, the palladium-catalyzed reaction strongly promotes the first cyclization onto the central allenic carbon to afford bicyclic sulfamides containing a seven- or eight-membered ring. We also succeeded in controlling formation of the two types of bicyclic sulfamides from single bromoallene by simply changing the reaction conditions.
大野 浩章, 田中 徹明, 化学, 61(2), 66-67 (2006).
9. Amine free crystal structure: The crystal structure of d(CGCGCG)2 and methylamine complex crystal
H. Ohishi, K. Tsukamoto, Y. Hiyama, N. Maezaki, T. Tanaka, T. Ishida, Biochem. Biophys. Res. Commun., 348(2), 794-798 (2006).
8. Stereodivergent synthesis of 1,4-bifunctional compounds by regio- and diastereoselective Pd-catalyzed allylic substitution reaction
N. Maezaki, M. Yano, Y. Hirose, K. Itoh, T. Tanaka, Tetrahedron, 62(44), 10361-10378 (2006).
Abstract: Highly stereoselective synthesis of 1,4-bifunctional compounds was accomplished via 1,2-asymmetric induction to α-oxyaldehyde and α-oxyketone followed by regio- and diastereoselective Pd-catalyzed allylic substitution reaction. We found that trifluoroacetate is a suitable leaving group for the allylic substitution reaction. Various nucleophiles containing carbon, nitrogen, and sulfur can be applied to the method. Both 1,4-syn- and 1,4-anti-adducts were synthesized with high stereoselectivity by using stereodivergent reduction of the propargyl alcohols followed by allylic substitution reaction.
7. Calixarene-Based Template for X-ray Crystallographic Analysis of Template-Assembled Synthetic Proteins
K. Tsukamoto, H. Ohishi, N. Maezaki, T. Tanaka, T. Ishida, ChemBioChem, 7, 1559-1562 (2006).
Abstract: We have developed a novel calixarene derivative as a topological template of template-assembled synthetic proteins. In addition to its high crystallinity, the bromine-containing template facilitated phasing in X-ray analysis. The X-ray structure revealed that the template takes desired flattened cone conformation and its p-bromophenylalanine moieties have flexibility suitable for introduction of the various peptide chains. The flattened cone conformation was retained in a solution.
6. Self-assembled octameric cage constructed by the potassium salt of p-tert-butylcalixarene p-bromophenylalanine derivative in the solid state
K. Tsukamoto, H. Ohishi, Y. Hiyama, N. Maezaki, T. Tanaka, T. Ishida, Chem. Commun., 3606-3608 (2006).
Abstract: Two kinds of potassium salts of p-tert-butylcalixarene p-bromophenylalanine derivative formed octameric cages in the solid state that was demonstrated by X-ray crystallographic analysis.
5. Construction of tricyclic enone, a common precursor for aphidicolane and stemodane B/C/D-ring system
T. Tanaka, S. Yamamoto, K. Hiramatsu, K. Murakami, H. Yoshino, D. Patra, C. Iwata, H. Ohno, Chem. Pharm. Bull., 54(8), 1138-1143 (2006).
Abstract: Synthesis of a tricyclic enone (B/C/D ring system), a common key precursor for the aphidicolane- and stemodane-type diterpene, is described. The key reaction for the construction of the quaternary carbon center is allylation of epoxide at the more substituted carbon with an organotitanium reagent. Asymmetric reduction with DIP-Cl followed by stereoselective cyclization of spirocyclic ketone and the functional group modification gave the desired tricyclic enone in good yield.
4. Potassium Carbonate-Promoted Stereospecific 5-Endo-Trig Cyclization of Unactivated Allenes in the Absence of Any Transition Metals
H. Ohno, Y. Kadoh, N. Fujii, T. Tanaka, Org. Lett., 8(5), 947-950 (2006).
Abstract: Formation of 3-pyrrolines from simple unactivated allenes bearing a protected amino group under basic conditions is described. Treatment of α-amino allenes with potassium carbonate in DMF under reflux in the absence of any transition-metal catalysts gave the corresponding 3-pyrrolines in good to excellent yields, by 5-endo-trig mode cycloisomerization. The reaction of internal allenes with an axial chirality afforded the corresponding 3-pyrrolines in a stereoselective manner.
3. Systematic Synthesis of Diastereomeric THF-ring Cores and Total Synthesis of Antitumor Annonaceous Acetogenins
N. Maezaki, N. Kojima, T. Tanaka, Synlett (account), 993-1003 (2006).
Abstract: We have developed a systematic synthesis of the poly-THF ring cores of antitumor Annonaceous acetogenins by utilizing asymmetric alkynylation and subsequent stereodivergent THF ring formation as key steps. The asymmetric alkynylation of α-oxyaldehyde and α-tetrahydrofuranic aldehyde with an (S)-3-butyne-1,2-diol derivative proceeded in good yield with very high diastereoselectivity. These adducts were converted into mono- and bis-THF cores via two kinds of one-pot THF ring formation, respectively. The total syntheses of murisolin, 16,19-cis-murisolin, and longimicin D, which show cytotoxic activity against the human tumor cell, were accomplished by applying the methodology.
2. Luteolin, a flavonoid, inhibits AP-1 activation by basophils
T. Hirano, S. Higa, J. Arimitsu, T. Naka, A. Ogata, Y. Shima, M. Fujimoto, T. Yamadori, T. Ohkawara, Y. Kuwabara, M. Kawai, H. Matsuda, M. Yoshikawa, N. Maezaki, T. Tanaka, I. Kawase, T. Tanaka, Biochem. Biophys. Res. Commun., 340(1), 1-7 (2006).
Abstract: Flavonoids including luteolin, apigenin, and fisetin are inhibitors of IL-4 synthesis and CD40 ligand expression by basophils. This study was done to search for compounds with greater inhibitory activity of IL-4 expression and to clarify the molecular mechanisms through which flavonoids inhibit their expression. Of the 37 flavonoids and related compounds examined, ayanin, luteolin, and apigenin were the strongest inhibitors of IL-4 production by purified basophils in response to anti-IgE antibody plus IL-3. Luteolin did not suppress Syk or Lyn phosphorylation in basophils, nor did suppress p54/46 SAPK/JNK, p38 MAPK, and p44/42 MAPK activation by a basophilic cell line, KU812 cells, stimulated with A23187 and PMA. However, luteolin did inhibit phosphorylation of c-Jun and DNA binding activity of AP-1 in nuclear lysates from stimulated KU812 cells. These results provide a fundamental structure of flavonoids for IL-4 inhibition and demonstrate a novel action of flavonoids that suppresses the activation of AP-1.
1. First Total Synthesis of Longimicin D
H. Tominaga, N. Maezaki, M. Yanai, N. Kojima, D. Urabe, R. Ueki, T. Tanaka, Eur. J. Org. Chem., 1422-1429 (2006).
Abstract: We have accomplished the first total synthesis of longimicin D (1), which has potent cytotoxicity against the human pancreatic carcinoma cell. The bis-THF core bearing congested stereocenters was constructed by our methodology for synthesis of the poly-THF cores, which consists of asymmetric alkynylation with the C4-unit and stereodivergent THF ring formation. Although we planned to join the C9-C34 bis-THF core segment 2 and the C1-C8 γ-lactone segment 3, a model study revealed that the assembly was difficult. We resolved the problem by applying asymmetric alkynylation of bis-THF aldehyde 24 with functionalized alkyne 19 involving the polymethylene chain from the C3 to C12 position.