Akinori Seta

Photoaddition reactions of 3-nitro-2-enopyranoside derivatives in 1,3-dioxolane

Abstract Irradiation of 3-nitro-2-enopyranoside derivatives having α- d -erythro, β- d -hreo, and α- d -threo configurations in 1,3-dioxolane afforded adducts in moderate yields. Structural assignment of the adducts, including conformational analyses of the 1,3-dioxolanyl moiety, were performed.

Novel synthesis of γ-hydroxy-α-nitro-olefins

Treatment of α-unsubstituted αβ-epoxyketoximes with trifluoroperoxyacetic acid affords the corresponding γ-hydroxy-α-nitro-olefins in high yields.

Preparation of methyl 4,6-di-O-acetyl-3-C-nitro-2-enopyranoside derivatives and their reduction with sodium borodeuteride

Abstract The conformationally flexible title compounds were prepared and subjected to reduction with sodium borodeuteride. Deuteride ion attacks exclusively from the side opposite of the anomeric methoxyl group. However, the stereoselectivity of a similar reduction of the corresponding 4,6-O- benzylidene -β- d -threo-2- enopyranoside derivative, adopting the 0H5 conformation, was exceptionally low, suggesting that reduction of the 4,6-diacetate having the β- d -threo configuration did not occur from the stable 0H5 conformation, but from an unstable ( ( 5 H 0 ) one.

First preparation of pyranosid nitroolefin having a peroxy group and its reaction with some nucleophiles

Abstract Treatment of nitroalkene 1 with t-butyl hydroperoxide and m-chloroperbenzoic acid gave the S n 2′ product and 2,3-anhydro derivative, respectively, in high yields. The former product is proved to be useful intermediate for introduction of nucleophiles at C-4.

Anomeric effect on kinetic acidity: Examples for the oxygen atom of ethers to accelerate abstraction of an α-hydrogen atom

Abstract In contrast with general observation, two different types of experiments indicate that the abstraction of α-hydrogen atom of ether having proper conformation is slightly enhanced by the oxygen atom in line with our previous AM1 calculation.

New aspect of thermodynamic stability of 3-C-nitro-d-glucal derivatives

Abstract Themodynamic stability of 3-C-nitro- d -glucol and - d -allal derivatives as well as the corresponding 5a-carba sugars was reproduced by ab initio (6-31G ∗ ) calculations. The calculations also predicted that 3-C-nitro- d -gulal should be more stable than its 3-epimer, in spite of strong bios for a nitro group at C-3 to occupy the equatorial position. This prediction was experimentally proved.

Preparation of a methyl 3,4-dideoxy-3-C-nitro-α-d-threo-hex-3-enopyranoside bearing a peroxy function at C-2 and its reactions with some nucleophiles

Abstract Treatment of 4,6-diacetate 3 with tert -butyl hydroperoxide gave the S N 2′ product 6 in high yield, the formation of which presumeably involves an intermediary nitronate. The thus prepared 6 reacted with nucleophiles to afford 2,3-anhydro derivatives having the talo configuration.

Anomeric effect on acidity; experimental and theoretical studies on proton abstraction at anomeric center of 1,5-anhydro-4,6-O-benzylidene-2,3-dideoxy-3-C-nitro-D-hex-2-enitol

Abstract The quasi-equatorial hydrogen atom at the anomeric center of the title compound was experimentally proved to be slightly more acidic than the quasi-axial one; this is supported by AM1 calculation.

Formation of dihydrofuran derivatives by intramolecular substitution of the manno adducts formed by Michael reaction of a 1-O-acetyl-3-C-nitro-2-enopyranose derivative with 2,4-pentanedione and dibenzoylmethane

Abstract Michael reaction of 1- O -acetyl-4,6- O -benzylidene-2,3-dideoxy-3- C -nitro-α- d - erythro -hex-2-enopyranose with 2,4-pentanedione afforded two cyclized products, together with adducts having the α- d - gluco and α- d - manno configurations. The dihydrofuran structures of the cyclized products were determined from spectral data, supported by semi-empirical molecular orbital (AM1) calculations. Cyclization occurred from the manno adduct through nucleophilic expulsion of the anomeric acetoxyl group by an enolate generated from the C-2 substituent. Such a proposed intramolecular SN2 mechanism was supported by a similar reaction with dibenzoylmethane.

Nucleophilic addition reactions of 1,5-anhydro-4,6-O-benzylidene-2,3-dideoxy-3-C-nitro-d-erythro-hex-2-enitol and its 5a-carba derivative

Abstract Reactions of the title compounds with several nucelophiles suggested that the ring oxygen atom (O-5) accelerated the reactivity of the nitro alkene moiety, but scarcely affected the stereoselectivity of the nucleophilic attack.