Yoshihisa Miwa

Experimental charge density and electrostatic potential in nicotinamide

The accurate crystal structure of nicotinamide, 3-pyridinecarboxamide, was determined from X-ray and neutron diffraction experiments: C(6)H(6)N(2)O, M(r) = 122.13, monoclinic, P2(1)/c, Z = 4. The electron distribution at 150 K was determined by the maximum entropy method and the electrostatic potential in the crystal was calculated by Fourier convolution of the electron distribution. The electrostatic properties of the nicotinamide molecule depend on the molecular conformation. The asymmetric electrostatic potential field observed above and below the pyridine-ring plane is related to the rotation of the carboxamide group with respect to the pyridine plane. The positive potential peak at the C4 atom of the pyridine ring extends to the C=O-group side of the plane. The asymmetry of the potential on the C4 atom is consistent with the stereospecificity of hydride transfer in NAD(+)/NADH oxidoreduction.

Indium(III)-Catalyzed Tandem Reaction with Alkynylbenzaldehydes and Alkynylanilines to Heteroaromatic Compounds

Starting from ortho-alkynylbenzaldehydes and ortho-alkynylanilines, In(OTf)3-catalyzed synthesis of ring-condensed heteroaromatic compounds was developed via a domino intramolecular nucleophilic attack/intermolecular cycloaddition/dehydration reaction.

SYNTHESIS OF CHIRAL AMINO ALLENES VIA AN ORGANOCYANOCUPRATE-MEDIATED RING-OPENING REACTION OF ENANTIOPURE ETHYNYLAZIRIDINES

Amino allenes have been synthesized from 2-ethynylaziridines via organocopper-mediated reactions. Whereas treatment of enantiomerically pure (2 R ,3 S )-2,3- trans -3-alkyl-2-ethynylaziridines with RCu(CN)M (M = Li or MgX) yield exclusively (S,S) -allenylamines in high yields, isomeric (2 S ,3 S )-2,3- cis -3-alkyl-2-ethynylaziridines afford (S,R) -allenylamines in comparable high yields.

Preparation and absolute configuration of hexahydroxyter- and octahydroxyquaternaphthalene derivatives

Abstract Oxidative coupling reactions of the stereochemically defined S -tetrahydroxybinaphthalene derivative gave a separable mixture of two diastereomers of the quaternaphthalenes of S , S , S and S , R , S configurations, whose stereostructures were confirmed by an alternative chemical transformation through the ternaphthalenes as well as the X-ray structure analysis. The CD spectra of the corresponding diastereomers were indicative of the stereochemistry across the axis.

SN2′ Ring opening of aziridines bearing an α,β-unsaturated ester group with organocopper reagents. A new stereoselective synthetic route to (E)-alkene dipeptide isosteres

Regio- and stereo-selective synthesis of (E)-alkene dipeptide isosteres has been successfully achieved by exposing both (E)- and (Z)-N-(4-methylphenyl)sulfonyl-γ,δ-epimino-α,β-enoates to organocopper reagents at –78 °C for 30 min.

Regio- and stereoselective multisubstituted enol ester synthesis.

Regio- and stereoselective cohalogenation of alkynes with NXS (X = Br, I) was achieved, and the stereoselectivity of the resulting alkenes was dependent on the substituent on the alkyne. Cohalogenation and successive cross-coupling gave multisubstituted enol esters in a one-pot process.

Regioselective Iodoazidation of Alkynes: Synthesis of α,α-Diazidoketones

Aryl alkyl alkynes reacted with N-iodosuccinimide (NIS) and trimethylsilyl azide (TMSN3), leading to α,α-diazidoketones via the regioselective addition of IN3 to alkynes. Huisgen cyclization of α,α-diazidoketones generated bis-triazole compounds.

Sesquiterpene glucosides from anti-leukotriene B4 release fraction of Taraxacum officinale.

Abstract Chemical examination of the MeOH extract of the root of Taraxacum officinale, which exhibited inhibitory activity on the formation of leukotriene B4 from activated human neutrophils, has resulted in the isolation of 14-O-β-D-glucosyl-11,13-dihydro-taraxinic acid (1) and 14-O-β-D-glucosyl-taraxinic acid (2). The absolute stereostructure of 1 has been established by X-ray chrystallographic examination.

Asymmetric Diels-Alder Cycloaddition with Chiral 2-Alkylsulfinyl-1-nitroalkenes.

Abstract The Diels-Alder reaction of chiral 2-alkylsulfinyl-1-nitroalkene 1 and Danishefskys diene (2) afforded adducts 3 and 4 in good chemical yield with a high enantiomeric excess, while diastereomeric nitroalkene 7 gave 8 and 9 , enantiomeric to 3 and 4 , respectively,

Cytotoxic cycloartane-type triterpenes from Combretum quadrangulare

Seven novel cycloartane-type triterpenes were isolated from Combretum quadrangulare, and their structures were elucidated on the basis of spectral analysis. All these compounds were tested for their cytotoxicity against murine colon 26-L5 carcinoma cells. Methyl quadrangularate B (2) and methyl quadrangularate D (4) exhibited potent cytotoxicity having ED50 values 9.54 and 5.42 microM, respectively.