Kimiaki Furuichi

SUSCEPTIBILITY OF LEUCROSE TO CARBOHYDRASES

Oligosaccharides were synthesized from sucrose using the dextransucrase of Leuconostoc mesenteroides, and the products were isolated by chromatography. The oligosaccharide obtained as the main product was identified as leucrose by 13C-NMR. Production of leucrose from sucrose was greatly increased when the reaction was done with fructose as an acceptor. The susceptibility of leucrose to carbohydrases was tested, and leucrose was also a useful substrate for detecting or measuring α-glucosidase in enzyme mixtures such as culture filtrates of microorganisms.

New ketone synthesis viaβ-hydroxy o-nitrophenyl selenoxides; a one-step synthesis of deoxy-keto sugars

β-Hydroxy o-nitrophenyl selenides and their O-alkyl or O-acyl derivatives were prepared and converted into ketones or the corresponding enol derivatives in satisfactory yields; these reactions were applied to the synthesis of sugar derivatives.

Syntheses, physical properties and X-ray structures of benzocycloheptene-1,4,7-trione and its 6-phenylthio- and 6,8-bis(phenylthio) derivatives. Novel A, A-D and D-A-D molecular units aiming at organic conductors

6-Phenylthio- and 6,8-bis(phenylthio)benzocycloheptene-1,4,7-triones 2 and 3 have been synthesized as prototypes for a new type of organic conductor. Their characteristic features of structures and physical properties are discussed in comparison with those of the parent trione 1 and related compounds. The single crystal X-ray analyses showed that a segregated column stacking existed in a crystal of 3 and a crystal of benzene adduct of 2, but not in 1 and pure 2. The pendant phenyl groups supported by sulfur atoms in 2 and 3 were found to be facing to the quinone carbonyl and may be responsible to the molecular arrangements in their crystals. Estimations of crystal structures by the crystal molecular packing analysis showed that the segregated column stacking was stable in 3, but unstable in 1. The derivatives of 3 seem to be potential candidates for organic conductors of D–A–D type.

Cyclopentane-annelated pyranosides: a new approach to chiral iridoid synthesis

1-α-O-Methyl-loganin (1) was synthesised from methyl 2,3-anhydro-α-D-lyxopyranoside by cyclopentane annulation using the pyranose ring as the tetrahydrocoumalate skeleton.

Claisen rearrangement of hexenopyranoside allyl ethers: A new approach to α-branched-chain dicarbonyl sugars

Abstract The β-hydroxy phenylselenides prepared by cleavage of 2,3-anhydropyranosides with sodium phenylselenide were quantitatively transformed into the corresponding allyl ethers. Oxidation of the allyl ethers, followed by thermal elimination and rearrangement, gave C -allylhexosuloses in good yield. Rearrangement of ethers 10a and 10c was especially stereoselective, giving axially oriented C -allylhexosulose derivatives, which were readily epimerized to their equatorial isomers in quantitative yield. In the Claisen rearrangement of the crotyl ether 14c , the chirality of the sugar was transferred to the newly formed asymmetric carbon atom. This procedure provides a convenient method to convert an anhydro sugar into a C -allylhexosulose derivative.

X-Ray structures and physical properties of tropone-annelated p-benzoquinones substituted with X-Ar groups α to tropone carbonyls and first examples of the trione substituted with an electron-withdrawing group

6,8-Dibenzyl-, 6,8-bis(p-dimethylaminobenzyl)- and 6,8-diphenoxy-benzocycloheptene-1,4,7-triones have been synthesized and their physical properties (IR, UV, NMR spectra and redox potentials) compared with those of 6,8-bis(phenylthio)benzocycloheptene-1,4,7-trione. The first redox potentials fall in the order OPh > CH2Ph > SPh > CH2C6H4NMe2-(p) but the second fall in the order OPh > SPh > CH2Ph > CH2C6H4NMe2-(p), the latter order is in accord with that of their σI values. The molecular structures of the first three compounds, determined by the single crystal X-ray analyses, were found to be very similar, except for the bond angle at the atom connecting tropone with the phenyl rings. The crystal structures of compounds 4 and 5 were almost identical, but were quite different from that of the SPh analogue 3. Success in the synthesis of benzocycloheptene-1,4,7-triones substituted with an electron withdrawing group on C-6 is also described. Electron transfer was not appreciable in a crystal of the complex of benzo[1,2;4,5]dicycloheptene-3,6,9,12-tetrone with TTF according to the crystal structure analysis.

Enhancement of electron affinity of benzocycloheptene-1,4,7-trione by substitution

To obtain new efficient electron acceptors, three bromine-substituted benzocycloheptene-1,4,7-triones, 14, 15, 16, and 7-dicyanomethylene-7H-benzocycloheptene-1,4-dione 36 have been synthesized. The electron affinities of the bromine-substituted quinones were found to be raised considerably as the number of bromine atoms increased compared with the parent trione 3. A linear correlation between E1redox and ELUMO(MNDO) has been shown. The dicyanomethylene substitution (36) of the tropone carbonyl of 3 caused an increase in the electron affinity by E1+ 0.2 V. To obtain an acceptor carrying electron-withdrawing substituents on C6 and C8 of 3, the 6,8-dimethoxycarbonyl derivative 18 was oxidized and gave a ring-contracted product 22 in fair yield. The formation is discussed in terms of electron distribution in the molecule of the expected product 19.