Tohru Sakakibara

Direct formation of C-glycofuranosyl derivatives by the reaction of d-aldoses with nitromethane and methyl nitroacetate

Abstract Under appropriate conditions, condensation of d -ribose (1) with nitromethane afforded d -ribofuranosylnitromethanes (3 and 4) directly, in high yields. On the other hand, similar reactions of 5-deoxy- d -xylose (9) gave acyclic products (11), which were readily converted into the cyclized products (12 and 13) upon heating in water. Condensation of 9 with methyl nitroacetate, however, furnished a cyclic product (10) directly. The stereochemistry of the products is discussed on the basis of chemical reactions as well as instrumental data.

Addition of hydrazoic acid to methyl 6-O-benzoyl-2,3-dideoxy-α-D-glycero-hex-2-enopyranosid-4-ulose

Abstract The title compound 4 reacted with hydrazoic acid to give exclusively an adduct having the threo configuration, whose structure was established by reduction to the lyxo derivatives 8 and 10 . The reaction of 4 with hydrogen peroxide afforded the epoxide 12 , the lyxo structure of which was deduced by conversion into the alcohol 13 . Tributylborane also reacted with the enone 4 , giving the adduct 15 , whose configuration was tentatively assigned to be threo .

Stereochemistry of nucleophilic addition reactions 13 : Kinetically controlled nucleophilic addition reactions to methyl 4,6-0-benzylidene-2,3- dideoxy-2-nitro-β-D-erythro-hex-2-enopyranoside: an important role of a(1,3) strain

Abstract An improved synthesis of methyl 4,6-0-benzylidene-2,3-dideoxy-2-nitro-β-D- erythro -hex-2-enopyranoside and its reactions with various nucleophiles are described; all the nucleophiles were found to approach exclusively or predominantly from the equatorial side of the molecule, giving the β-D-glucopyranoside derivatives as the major or exclusive product. The stereochemical course of approach of a nucleophile observed in the present reactions and in the literature are discussed.

Stereoselective nucleophilic addition reactions to nitro sugars

Nucleophile(s) almost exclusively added from the equatorial side of 2-nitro-β-D-2-enopyranoside and the axial side of 2-nitro-D-ribo-1-enitol. On the other hand, methoxide and tert-butyl peroxide ions approached from the equatorial side of 2-nitro-α-D-2-enopyranoside, whereas methanol and hydrogen peroxide ion from the axial side.

Preparation of 4,6-O-benzylidene-3-deoxy-3-C-nitro-d-glucal and -d-allal and 1,5-anhydro-4,6-O-benzylidene-2,3-dideoxy-3-C-nitro-d-threo-hex-2-enitol

Abstract Oxidation of 1,5-anhydro- d -mannitol with sodium metaperiodate, followed by nitromethane cyclization and benzylidenation afforded 1,5-anhydro-3-nitrohexitol derivatives having the d - gluco , d - manno , and d - galacto configurations. Conversion of the nitro alcohols into the nitro alkenes was accompanied by double-bond migration of the nitro 2,3-alkenes to give the 1,2-unsaturated derivatives.

Kinetically controlled nucleophilic addition-reactions to methyl 4,6-O-benzylidene-2,3-dideoxy-2-nitro-α-d-erythro-hex-2-enopyranoside☆

Abstract Axial attack mainly occurred in the reactions of methyl 4,6- O -benzylidene-2,3-dideoxy-2-nitro-α- d - erythro -hex-2-enopyranoside with sodium borodeuteride, hydrogen peroxide, hydrogen cyanide, and methanol, whereas equatorial attack predominated in the reaction with sodium methoxide and tert -butyl peroxide.

Synthesis, stereochemistry, and epimerization of methyl 4,6-O-benzylidene-2,3-dicyano-2,3-dideoxy-β-D-hexopyranosides having the allo, altro, gluco, and manno configurations☆

Abstract The reaction of methyl 4,6- O -benzylidene-2,3-dideoxy-3-nitro-β- D - erythro -hex-2-enopyranoside with hydrogen cyanide in the presence of catalytic amounts of potassium cyanide afforded the title compounds. The reaction is shown to involve the probable addition of hydrogen cyanide to an intermediate 2-cyano-hex-2-enopyranoside, followed by epimerization. The stereochemistry of this reaction and the epimerization of the products are described.

Reaction of 1-O-acetyl-4,6-O-benzylidene-2,3-dideoxy-3-nitro-α-D-erythro-hex-2-enopyranose and its anomer with hydrazoic acid

Abstract The title compounds ( 6 and 7 ) were prepared by acetylation of 4,6- O -benzylidene-3-deoxy-3-nitro-α- D -glucopyranose ( 3 ) followed by elimination of acetic acid. Reaction of the β anomer ( 7 ) with hydrazoic acid gave the thermodynamically more-stable glucopyranose 8 exclusively, whereas similar reaction of the α anomer ( 6 ) afforded the less-stable mannopyranose 10 as the major product and the gluco isomer 11 as the minor product. Striking solvent-effects were observed in the latter reaction, including the epimerization of 10 to 11 in dimethyl sulfoxide and N,N -dimethylformamide, but not in other solvents (chloroform, ethyl acetate, and tetrahydrofuran). The reaction of 6 with hydrogen cyanide also gave the mannopyranose 9 in good yield.

Preparation of methyl 4,6-O-benzylidene-2,3-dideoxy-2,3-dinitro-α-D-glucopyranoside and its selective conversion into the corresponding 2-nitro-2-enopyranoside

Abstract Treatment of methyl 4,6- O -benzylidene-2,3-dideoxy-3-nitro-α- D - erythro -hex-2-enopyranoside ( 3 ) with sodium nitrite in benzene-water in the presence of small amounts of tributylhexadecylphosphonium bromide as a phase-transfer catalyst afforded the 2-nitro alkene 4 in 47% yield. A similar reaction in the presence of 1.3 equiv. of acetic acid gave the 2,3-dinitro derivative 5 in 58% yield; it was selectively converted into the 2-nitro alkene 4 . In these reactions, nitrite ion undergoes addition from the axial and equatorial sides of 3 and 4 , respectively.

The Michael reaction of a methyl 2-C-nitro-α-d-hex-2-enopyranoside: Preparation and structural determination of the adducts having the d-altro-, d-gluco, and d-manno configurations

Abstract The reactions of methyl 4,6- O -benzylidene-2,3-dideoxy-2- C -nitro-α- d - erythro -hex-2-enopyranoside ( 1 ) with 2,4-pentanedione and diethyl malonate afforded adducts having the d - altro , d - gluco , and d - manno configurations. Besides the adducts having the d - gluco and d - altro configurations, a 1,5-anhydro-2- C -nitrohex-1-enitol derivative was isolated in the reaction of 1 with dimethyl malonate. The product ratio was found to depend on the solvent. The nucleophilic addition and subsequent protonation appear to be respectively controlled kinetically and thermodynamically.