C. Monneret

Synthesis of methyl 4-amino-2,4,6-trideoxy-3-O-methyl-l-arabino-hexopyranosides (methyl α- and β-l-holantosaminide) and of methyl 4-amino-2,4,6-trideoxy-3-O-methyl-α-l-lyxo-hexopyranoside (methyl α-l-3-epiholantosaminide)

Abstract Methyl 4-amino-2,4,6-trideoxy-3- O -methyl-β- l - arabino -hexopyranoside was synthesized in eight steps, in 40% overall yield, from methyl 4,6- O -benzylidene-2-deoxy-α- d - ribo -hexopyranoside. The inversion of configuration at C-5 was achieved through 5,6-unsaturated methyl 2,6-dideoxy-3- O -methyl-α- d - erythro -hex-5-enopyranoside, followed by stereospecific reduction to give methyl β- l -diginoside. Treatment of methyl 2,6-dideoxy-3- O - p -tolylsulfonyl-α- l - arabino -hexopyranoside with sodium methoxide afforded stereoselectively the 3- O -methyl derivative, which was converted into a mixture of methyl α- l -holantosamine and its 4-amino- l - lyxo -epimer. The latter compound was also synthesized stereospecifically via the 4-azido derivative.

Synthèse et réactivite du méthyl-2-O-benzoyl-3-bromo-3,6-didésoxy-α-l-altropyranoside et du méthyl-2-O-benzoyl-3-bromo-3,6-didésoxy-4-O-méthyl-α-l-altropyranoside

Abstract Methyl 2- O -benzoyl-3-bromo-3,6-dideoxy-α- l -altropyranoside ( 4 ) and methyl 2- O -benzoy]-3-bromo-3,6-dideoxy-4- O -methyl-α- l -altropyranoside ( 5 ) have been prepared from methyl-α- l -rhamnopyranoside, respectively, in 2 and 3 steps. Reduction of 4 with lithium aluminium hydride followed by acid hydrolysis afforded the 3,6-dideoxy- l - arabino -bexose ( l -ascarylose). The anhydro sugars 8 and 9 have been used as intermediates in the stereoselective synthesis of 6-deoxy-3- O -methyl- l -altropyranose ( l -vallarose) and of 3-amino-3-degxy- l -altro sugars. Under azidolysis conditions, and according to the temperature, 5 gave unsaturated sugars such as 20 and the derived 26 , or azido compounds such as 21 and 24 , and the derived sugar methyl 2-amino-2,3,6-trideoxy-α- l - threo -hexopyranosid-4-ulose ( 25 ).

Synthèses de 3,6-didésoxy-sucres: Synthèses du méthyl-3,6-didésoxy-4-O-méthyl-α-L-arabino-hexopyranoside (méthyl-4-O-méthylascaryloside) et du méthyl-3,6-didésoxy-α-D-arabino-hexopyranoside (méthyl-α-tyveloside)

Abstract Methyl 4- O -methyl-ascaryloside was synthesized from methyl 2,3- O -benzylidene-4- O -methyl-α- L -rhamnopyranoside, and methyl α-tyveloside from methyl 4- O -benzoyl-6-bromo-6-deoxy-α-D-mannopyranoside. Treatment of methyl 2,3:4,6-di- O -benzylidene-α-D-mannopyranoside with N -bromosuccinimide and reduction with lithium aluminum hydride gave methyl α-tyveloside and methyl 4,6-dideoxy-α-D- arabino -hexopyranoside.

Synthèse et réactivité vis-à-vis de réactifs nucléophiles des méthyl-3,4-anhydro-2,6-didésoxy-α- et -β-l-lyxo- et -ribo-hexopyranosides

Abstract The ring-opening reactions of methyl 3,4-anhydro-2,6-dideoxy-α- and -β- l - lyxo - and - ribo -hexopyranosides with sodium azide, ammonia, methyl- and dimethylamine, and sodium methoxide were studied. Regioselectivity is explained in terms of steric and conformational factors.

Synthèse de disaccharides naturels, fragments d'anthracyclines oligosaccharidiques

Abstract Methyl 2,6-dideoxy-4-O-(2,3,6-trideoxy-α- l -glycero-hexopyranosyl-4-ulose)-β- l -lyxo-hexopyranoside and methyl 2,6-dideoxy-4-O-(2,3,6-trideoxy-α- l -erythro-hexopyranosyl)-β- l -lyxo-hexopyranoside, fragments of C→B type of trisaccharides naturally occurring in antitumor anthracycline antibiotics, were prepared starting from 4-O-acetyl- l -amicetal and methyl 3-O-benzyl-2-deoxy-β- l -fucopyranoside in five and four steps, respectively.

Ouverture par le N-bromosuccinimide des acétals benzylidéniques de méthyl-hexosides de configuration manno et synthèse de la N-acétyl-l-mycosamine

Abstract Methyl 2,3:5,6-di-O-benzylidene-α- d -mannofuranoside and methyl 2,3-O-benzylidene-α- l -rharmnofuranoside were prepared according to a new procedure by simultaneous glycosidation and acetalation of d -mannose and l -rhamnose. Treatment of these compounds and of 1,6-anhydro-2,3-O-benzylidene- d -mannose with N-bromosuccinimide gave exclusively the 3-bromo compounds by regiospecific opening of the acetal ring. Thus, starting from rhamnose, N-acetyl- l -mycosamine (3-amino-3,6-dideoxy- l -mannose) was prepared in seven steps with a 32% overall yield.

Synthese d'un disaccharide, constituant naturel d'anthracyclines antibiotiques et antitumorales

Zusammenfassung The methyl glycoside of 2,3,6-trideoxy-3-dimethylamino-4-0-(2,6-dideoxy-α- L -lyxo-hexopyranosyl)- L -lyxo-hexopyranose, a disaccharide naturally occurring in anti-tumor anthracycline antibiotics, was prepared as well as the methyl and benzyl glycosides of the corresponding di-O-acetyl N-acetyl derivative.

Réarrangement des méthyl-3,6-didésoxy-α-d-et -l-arabino-hexopyranosides en présence de benzaldéhyde et d'un acide de lewis

Abstract Methyl 2- O -benzoyl-5- O -benzyl-3,6-dideoxy-α- d - or - l - arabino -hexofuranosides were regiospecifically obtained by treatment of methyl 3,6-dideoxy-α- d - or - l - arabino -hexopyranosides with benzaldehyde in the presence of a Lewis acid in an excellent yield (70–95%). The formation of these derivatives ( 2 or 9 ) is probably due to the intermediary formation of a bis(acetal), followed by inter- or intra-molecular hydride transfer. After selective deprotection of OH -5, 5-acetamido- and 5-amino-3,5,6-trideoxyhexose derivatives were prepared from 9 . Selective deprotection at O-2 and azidolysis of methyl 5- O -benzyl-3,6-dideoxy-2- O -tosyl-α- d - arabino -hexofuranoside or of the corresponding 2- O -trifluoromethylsulfonyl derivative gave 2-amino-2,5,6-trideoxyhexoses. Reduction and acetylation of the azidodeoxysugar led to methyl 2-acetamido-2,3,6-trideoxy-α- d - ribo -hexofuranoside in an overall yield, from 2 , of 50%.

Stereospecific synthesis of methyl 2,6-diacetamido-2,3,6-trideoxy-α-D-ribohexofuranoside and hexopyranoside, derivatives of tobrosamine

Abstract Title derivatives of 2,6-diamino-2,3,6-trideoxy- D -ribo-hexose (tobrosamine), the amino-sugar component of the antibiotic nebramycin factor 6, have been prepared in a stereospecific manner, based on the Tischenko rearrangement of methyl 3,6-dideoxy-α-arabino-hexopyranoside in the presence of benzaldehyde and Lewis acids.

Alcaloïdes stéroïdiques ☆: CXL. Trois nouveaux aminodésoxyglyco-stéroïdes isolés des feuilles de L'holarrhena antidysenterica (Roxb.) wall. : l'holarosine b et les holantosines e et f. Un nouveau sucre aminé, la D-holacosamine

Abstract Holarosine B, 3β-(4-amino-2,4,6-trideoxy-3- O -methyl-β- D - ribo -hexopyranosyl) oxy-14β-hydroxy-5α,17βH-card-20(22)-enolide, and holantosines E and F have been isolated from H. antidysenterica leaves. Holantosines E and F are β- D -glycosides of a new amino sugar, D -holacosamine or 4-amino-4-deoxy-sarmentose, and holantogenine or anhydroholantogenine.