Alain Olesker

Synthesis of α-azido aldehydes. Stereoselective formal access to the immunosuppressant myriocin

Abstract Stereoselective preparation of an acyclic α-azido aldehyde permitted access in a few steps to a key intermediate in a formal synthesis of myriocin.

Synthesis of two enantiomeric tetrasubstituted cyclohexanones from 6-deoxyhex-5-enopyranoside derivatives

Abstract The conversion of various 6-deoxyhex-5-enopyranoside derivatives in the presence of a catalytic amount of mercury(II) sulfate into chiral cyclohexanones has been studied. Under the experimental conditions used, the stereochemistry at position 5 of the tetrasubstituted cyclohexanones appears to depend on the conformation of the starting carbohydrate derivatives which was indicated by the 13C-n.m.r. data. Reaction of methyl 4-O-benzoyl-2,3-di-O-methyl-β- l -arabino- and -α- d -arabino-hex-5-enopyranoside furnished the enantiomeric 2-benzoyloxy-5-hydroxy-3,4-dimethoxycyclohexanones 19 and 21, respectively.

Cycloaddition Reactions of Carbohydrate Derivatives. Part III. A New Route to Swainsonine Analogs.

Abstract Swainsonine analogs 10 and 12 have been synthesized from D- and L-arabinose, respectively, using cyclocondensation of azomethines with Danishefskys diene followed by stereoselective carbonyl and double bond reduction of the resulting pyridones, chain shortening and ring closure by reductive amination.

Total structure of the polythiazole-containing antibiotic micrococcin P. A 13C nuclear magnetic resonance study

The structure of the antibiotic micrococcin P has been determined by 13C n.m.r. spectroscopy.

Cycloaddition reactions of carbohydrate derivatives. Part VI. Quinolizidine analogs of castanospermine

Abstract Octahydroquinolizine-1,2,3,8-tetraols 12, 16 and 23, analogs of castanospermine, were synthesized from D-glucose, L-arabinose and D-mannose, respectively, using hetero-Diels-Alder reactions of sugar-derived azomethines as the key step.

The synthesis of 1L-1,2-anhydro-myo-inositol and 1L- and DL-1,2-anhydro-chiro-inositol

Abstract Two optically active inositol epoxides have been synthesised as potential glycosidase inhibitors. 1 L -1,2-Anhydro- myo -inositol was prepared from 1 L -1- O -toluene- p -sulphonyl- chiro -inositol and 1 L -1,2-anhydro- chiro -inositol was prepared from 1 L -1- O -toluene- p -sulphonyl- myo -inositol in good yield and without epoxide migration. DL -1,2-Anhydro- chiro -inositol was also prepared, by a novel route. The anhydroinositols were given preliminary tests for biological activity.

Efficient routes to pyranosidic homologated conjugated enals and dienes from monosaccharides

Abstract Three new processes for the obtention of pyranosidic dienes type B, and D and homologated conjugated enals A, have been designed in the context of the preparation of useful chiral building blocks from monosaccharides. Addition of vinylmagnesium bromide onto ulose 1 , followed by acetal ring opening; benzoate protection at C-4 and C-6; and dehydration of the tertiary hydroxyl group, mediated by thionyl chloride, reveals to be a straigthforward route to diene 11 . Analogous dehydration on conformationally rigid 2 was not regioselective and afforded isomeric dienes 3 and 6 in a 1:1 ratio. Addition of 2-lithio-1,3 dithiane onto locked 2,3-anhydropyranoses 21 and 22 followed by unravelling of the S,S-acetal moiety led efficiently to homologated α-enals 26 , 27 , 31 , and 30 and hence to dienes 34 , 14 , 20 and 13 through Wittig methylenation. Finally α-alkoxyvinyl ethers, prepared either by Wittig-Horner reaction of α-alkoxy-uloses, or by hetero Diels-Alder reaction of conjugated-enals, afforded in good to excellent yields pyranosidic α-enals 37 , 42 , 43 , 44 , 50 and 51 on treatment with pyridinium hydrochloride in pyridine or a mixture acetic acid-water (4:1).

Stereospecific access to branched-chain carbohydrate synthons.

Abstract Appropriate precursors for the synthesis of D-vancosamine and L-evernitrose have been stereospecifically obtained from methyl 4,6-O-benzylidene-2-deoxy-α- and β-D-threo-hexopyranosid-3-ulose.

Total synthesis of a monocyclic analogue of compactin

Abstract Total synthesis of Karanewskys monocyclic Compactin analogue 4 has been accomplished.

Stereoselective synthesis of the tetrasubstituted cyclohexane core of a monocyclic mevinic acid analogue

Abstract Stereoselective synthesis of a 1,2,3,4-tetrasubstituted cyclohexane 23 , intermediate towards Karanewskys monocyclic Compactin analogue 3 , has been performed starting from levoglucosan 4 .