Yoshifusa Arai

Stereoselective radical cyclization for the synthesis of bicyclic higher-carbon sugars. Synthesis of the sugar moiety of octosyl acids

The Bu3SnH - AIBN induced radical cyclization of 6-bromo-6-deoxy-3-O-[(E)-2-ethoxycarbonylethenyl]-1,2-O-isopropylidene-α-???-allofuranose (1) gave ethyl 3,7-anhydro-6,8-dideoxy-1,2-O-isopropylidene-α-???-glycero-???-allo-nonofuranuronate (2) in 80% yield. Similar cyclizations of furanose derivatives and a synthesis of the sugar moiety of octosyl acids were described.

X-ray Analysis of Successive Reaction in Crystalline State Photoisomerization of Cobaloxime Complexes

Abstract The γ-cyanopropyl group bonded to the cobalt atom in some cobaloxime complexes was isomerized to the α-cyanopropyl group through β-cyanopropyl group on exposure to visible light in the solid state. For the complex with 1-phenylethylamine as an axial base ligand almost chiral α-cyanopropyl group was produced with retention of the single crystal form. The mechanism is discussed on the basis of the structural change.

Synthesis of higher-carbon sugars by tributyltin hydride-azobisisobutyronitrile induced radical additions

Abstract The Bu 3 SnH - AIBN induced radical additions of 3,5-di- O -acetyl-6-deoxy-6-iodo-1,2- O -isopropylidene-α- D -gluco- and -allofuranose ( 1 and 10 ), and methyl 5-deoxy-5-iodo-2,3- O -isopropylidene-β- D -ribofuranoside ( 19 ) to dimethyl maleate, methyl acrylate, acrylonitrile, methyl vinyl ketone, and vinylene carbonate gave various types of higher-carbon sugars.

Chiral Lattice-Controlled Asymmetric (β-α)PHOTOISOMERIZATION OF 2-SUBSTITUTED ETHYL COBALOXIME COMPLEXES

Abstract Chiral lattice-controlled asymmetric photoisomerization of 2-methoxycarbonyl-ethyl, 2-carbamoylethyl, 2-(N-methylcarbamoyl)ethyl and 2-(N-phenylcarbamoyl)ethyl cobaloxime complexes was found to occur which afforded corresponding, optically active 1-substituted ethyl cobaloxime complexes in enantioselectivities ranging from 4 to 69%ee.

Mechanism of Solid-State Racemization for Optically Active Alkyl Cobaloxime Complexes — Synthesis and Solid-State Reaction of Deuterium-Labeled Complexes

Abstract The deutelium-labeled chiral 1,2-disubstituted ethyl cobaloxime complexes were synthesized, and the rate constants of the solid-state photo-racemization and photoisomerization of these complexes were determined. The reaction mechanism for the solid-state photoracemization was elucidated by rationalization of these results.

(2-Carbamoyl­ethyl)­bis­(di­methyl­glyoximato-N,N′)[(R)-1-(1-naphthyl)­ethyl­amine]­cobalt(III) ethanol solvate and bis­(di­methyl­glyoximato-N,N′)[2-(N-methyl­carbamoyl)­ethyl][methyl (S)-phenyl­alaninate-N]­cobalt(III)

The 2-carbamoylethyl and 2-(methylcarbamoyl)ethyl groups in the title cobaloxime complexes, [Co(C(4)H(7)N(2)O(2))(2)(C(3)H(6)NO)(C(12)H(13)N)].C(2)H(6)O and [Co(C(4)H(7)N(2)O(2))(2)(C(4)H(8)NO)(C(10)H(13)NO(2))], were isomerized to 1-carbamoylethyl and 1-(methylcarbamoyl)ethyl groups, respectively, on exposure to visible light in the solid state. Although both the crystal structures and the intermolecular hydrogen bonds are different in the two crystals, similar reaction rates were observed.

Intramolecular hydrogen shift in 3-O-benzyl-6-deoxy-D-hexofuranosyl-6 radicals and a criterion for determination of the configuration at 1′-position of 6-deoxy-3-O-(1-phenylalkyl)-1,2-O-isopropylidene-D-allofuranoses

The Bu3SnH - AIBN induced radical additions of 5-O-acetyl-3-O-benzyl-6-deoxy-6-iodo-1, 2-O-isopropylidene-α-D-allofuranose (2) to electron deficient olefins gave 6-deoxy-3-O-(1-phenylalkyl) derivatives as by-products. The configurations at C-1′ of them were determined on the basis of chemical shifts of their 1H-nmr spectra.

The Role of Hydrogen Bond and Crystal Solvent in the Solid-state (β-α) Photoisomerization of Novel 2-(N-phenylcarbamoyl)ethyl Cobaloxime Complexes [1]

Abstract The 2-(phenylcarbamoyl)ethyl group bonded to the cobalt atom in cobaloxime complexes was isomerized on exposure to visible light in the solid-state. The three complexes with different amines as axial base ligands were prepared and their crystal structures were determined by X-ray analysis. The reaction rates in the solid-state were mainly affected by the hydrogen bonds of the reactive group with the neighboring molecules and the occupation of crystal solvent molecules around the reactive group.