Rokuro Sudoh

Stereoselective synthesis of the thermodynamically less stable manno isomers from a nitro sugar

Abstract Reaction of methyl 4,6- O -benzylidene-2,3-dideoxy-3-nitro-o-α-D- erythro -hex-2-enopyranoside (2) with hydrazoic acid, hydrogen cyanide, theophylline, and 2,6-dichloropurine under weakly acidic or neutral conditions resulted in the stereo-selective formation of addition products having the thermodynamically less-stable manno configuration, whereas reaction of 2 with more-basic reagents yielded mainly products having the more stable gluco configuration.

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.

C-glycosyl derivatives in nitro sugar chemistry: Synthesis of D-ribofuranosylnitromethane derivatives and their epimerization under neutral conditions

Abstract The nitromethane condensation-product ( 3 ) from 2,3- O -isopropylidene- D -ribose ( 2 ) underwent dehydration and subsequent thermal cyclization in dimethyl sulfoxide to give a mixture of α- and β- D -ribofuranosylnitromethane derivatives ( 5 and 6 ) in a ratio of 7:2. Heating of 6- O -benzoyl-1-deoxy-1-nitro- D -altritol ( 10 ) in water afforded α- and β- C -glycosyl derivatives ( 11 and 12 ) in a ratio of 2:3. Pure 11 and 12 gave the same mixture of 11 and 12 when heated in water, and similar epimerization of the isopropylidene acetals 5 , 6 , 13 , and 14 proceeded readily upon heating, leading mainly to the thermodynamically more-stable α anomers.

Studies on nitro sugars : Part II. Synthesis of benzyl 3,5-DI-O-benzyl-2-deoxy-2-Nitro-α-D-xylofuranoside and its transglycosylation with alkali

Abstract Oxidation of benzyl 3,5-di- O -benzyl-2-oximino-α- D - threo -pentofuranoside ( 6 ) with trifluoroperoxyacetic acid afforded benzyl 3,5-di- O -benzyl-2-deoxy-2-nitro-α- D -xylofuranoside ( 8 ) in 83% yield. Transglycosylation of 8 to give the corresponding methyl xyloside ( 10 ) was achieved in alkaline methanol at room temperature, proceeding probably via an intermediate 2-nitroglycal ( 9 ). The structures of 8 and 10 were determined from their specific rotations and p.m.r. spectra.

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.

Denitration of carbohydrate α-nitroepoxides by nucleophiles

Abstract Several nucleophiles were separately treated with methyl and phenyl 2,3-anhydro-4,6- O -benzylidene-3-deoxy-3-nitro-β- d -allopyranoside, to give 2-substituted aldos-3-ulose derivatives. In the latter case, the subsequent β-elimination of the aglyconic phenyl group always occurred to afford the corresponding glycal. Reaction mechanisms thereof are also discussed.

Preparation of 4,6-O-benzylidene-2-C- and -3-C-p-tolylsulfonylhex-2-enopyranoside derivatives and a 2-C-p-tolylsulfonylhex-2-enitol derivative

Abstract 4,6- O -Benzylidenehex-2-enopyranoside derivatives having a 2- C - or 3- C-p -tolylsulfonyl group were synthesized from appropriate nitro sugars by the addition of p -toluenesulfinic acid followed by elimination of nitrous acid. 1,5-Anhydro-4,6- O -benzylidene-2,3-dideoxy-2- C-p -tolylsulfonyl- d - erythro -hex-2-enitol was similarly prepared. Methyl 4,6- O -benzylidene-2,3-dideoxy-2- C - and -3- C-p -tolylsulfonyl-α- d - erythro -hex-2-enopyranosides were alternatively ynthesized from methyl 2,3-anhydro-α- d -allo- and -mannopyranosides, respectively, by cleavage of the oxirane ring with sodium p -toluenethiolate, followed by oxidation.

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.