Showing papers by "Chizuko Kabuto published in 1993"

Revised Structure and Stereochemistry of Hypothemycin

Abstract: A cytotoxic 14-membered resorcylic macrolide, isolated from Coriolus versicolor (L. : FR.) QUEL., was found to be identical with hypothemycin, previously isolated from Hypomyces trichothecoides TSUBAKI. The structure of hypothemycin has been elucidated to be 1 rather than the originally proposed 2.

Synthesis of polycyclic cyclobutane derivatives by tandem intramolecular Michael-aldol reaction under two complementary conditions: TBDMSOTf-Et3N and TMSI-(TMS)2NH

Abstract: The treatment of α,β-unsaturated esters having a ketone function at an appropriate position with either TBDMSOTf in the presence of Et 3 N or TMSI in the presence of (TMS) 2 NH provided, via a tandem intramolecular Michael-aldol reaction sequence, several different types of cyclobutane derivatives. The two reaction conditions were complementary. Tricyclo[4.2.1.03-8]nonanes 34 and 35, tricyclo[5.1.1.0 3,8 ]nonane 40, tricyclo[5.4.0.0 3,7 ]undecane 51, tetracyclo[5.4.0.0 3,7 .0 9,11 ]undecane 45, and the bicyclo[3.2.0]heptanes 36, 57, and 38, which have structures either partially or completely similar to those of endiandric acids A (1a), B (1b), and C (2), trihydroxydecipiadiene (3), lintenone (4), italicene (3), and filifolone (6), were stereoselectively synthesized by the tandem reaction

Unusual hexameric structure in the crystal of sodium propylenediaminetetraacetatoeuropium(III)

Abstract: The unique hexameric crystal structure of the title complex, hexasodium bis{cyclotris[propylenediaminetetraacetato-µ-O,O′-diaquaeuropium(III)]}, has been shown by X-ray analysis.

Crystal Structure of the Adduct of Thiourea with 2,6-Diethylnaphthalene

Abstract: The crystal structure of 2,6-diethylnaphthalene thiourea adduct was solved by single crystal X-ray diffraction method. The crystal is monoclinic, space group P2l/c, with a = 12.571(3), b = 9.282(2), c = 14.634(3) A, β = 92.14(2)°, V = 1706.3(6) A3 and Z = 2. The final R value was 0.083. The structure was composed of thiourea (host) molecules enclosing channels with hexagonal-prism and 2,6-diethylnaphthalene (guest) molecules in the channels. The cross-section of the channel was deformed hexagon. In the channel, the occupying channel length of the guest molecule was 12.571(3) A

p- and m-Phenylenebis[trifluoro(phenyl)silicates] and Related Monosilicates

Abstract: Novel anionic pentacoordinate silicates, p-and m-phenylenebis[trifluoro(phenyl)silicates] and related mono-silicates were synthesized and their structures were determined by means of X-ray crystallography and NMR spectroscopy. Addition of a fluoride ion to a difluoro(phenyl)silyl group caused the significant decrease of the σP+ value as determined by 13C NMR spectroscopy.

Structure of Adduct Formed from α-Trichlorostannyl Ketone and Trichloroethynyltin a Direct Evidence for the Carbostannylation of Alkynyl Metals

Abstract: An adduct formed from 2-trichlorostannyl-3-pentanone and phenylethynyltrichlorotin was isolated, and the structure was determined by spectroscopy and X-ray crystallography. It provides a direct evidence for the carbostannylation of alkynyl metals.

Synthesis of Cyclotetragermanes of the Type of (R(Ph)Ge)4 and Conversion to (R(Cl)Ge)4. The First Functionalized Cyclotetragermanes.

Abstract: Condensations of R(Ph)GeCl2 (R = t-Bu and R = CEt2Me) with Mg/MgBr2 in THF produced cyclotetragermanes [R(Ph)Ge]4, which were converted to [R(Cl)Ge]4 by treatment with HCl/AlCl3 or with CF3SO3H followed by CH3COCl. The crystal structure of [t-Bu(Cl)Ge]4 was established by X-ray diffraction. Unusual configurational behavior of cyclotetragermanes is also described.