Stanislas Czernecki

Azido-phenylselenylation of protected glycals

Abstract Anti-Markovnikov azido-phenylselenylation of diversely protected glycals affords protected phenyl 2-azido-2-deoxy-α-selenoglycopyranosides. From D -glucal, the α-manno and α-gluco isomers are obtained, whereas from D -galactal, a complete stereocontrol is observed, affording exclusively the α-galacto isomer in 70% yield.

Tetra-n-propylammonium tetra-oxoruthenate(VII): a reagent of choice for the oxidation of diversely protected glycopyranoses and glycofuranoses to lactones☆

Abstract 2,3,4,6-Tetra- O -benzyl- d -glucopyranose, 2,3,5-tri- O -allyl- d -ribofuranose, 2,3,5-tri- O -allyl- and -tri- O -benzyl- d -arabinofuranose, and 2-deoxy-3,5-di- O -allyl- d - erythro -pentofuranose were oxidized to their corresponding lactones 6–10 by dimethyl sulfoxide activated by oxalyl chloride, pyridinium dichromate in the presence of molecular sieves and acetic acid, and tetra- n -propylammonium tetra-oxoruthenate(VII) using 4-methylmorpholine N -oxide as cooxidant. With the latter reagent, analytically pure lactones were obtained in 83–98% yield. A multistep preparation of 3,4,6-tri- O -benzyl-2-deoxy- d - arabino -hexono-1,5-lactone ( 14 ) from 3,4,6-tri- O -benzyl-1,5-anhydro-2-deoxy- d - arabino -hex-1 enitol (65% overall yield) is described.

Versatile behavior of o-stannylated-d-glucal towards halogens

O-Tributylstannyl-D-glucal undergoes allylic oxidation when treated with N-iodosucinimide (NIS) in benzene, whereas oxidative 1,6-halocyclization occurs with NIS in acetonitrile or molecular halogens in various solvents.

Stereocontrolled synthesis of β-C-glycosides and amino β-C-glycosides by Wittig olefination of perbenzylated glyconolactones derivatives

Abstract Wittig olefination of perbenzylated glyconolactones afforded stereoselectively the Z-C-glycosylidenes which were transformed to the corresponding β-C-glycosides and amino β-C-glycosides by hydrogenation followed by acetylation.

Reaction of organocuprate reagents with protected 1,2-anhydro sugars. Stereocontrolled synthesis of 2-deoxy-C-glycosyl compounds☆

Abstract The reaction of protected 1,2-anhydro-α- d -gluco- and β- d -manno-pyranoses with alkyl and phenyl organocuprates afforded the corresponding C -glycosyl compounds in acceptable to high yield. Complete stereocontrol was obtained, leading respectively to the β- d or the α- d anomer. With the perbenzylated manno derivative, deoxygenation at C-2 was achieved in high yield, affording 2-deoxy-α- d - C -glycosyl compounds.

Selenoglycosides 5.1 Stereocontrolled Synthesis of Seleno-Disaccharides

Abstract Stereocontrolled synthesis of α and β linked seleno-disaccharides is achieved by reaction of a diglycosyl-diselenide with a deoxyhalo sugar derivative under reducing conditions.

Synthesis of (2-deoxy-α-d-glyc-2-enopyranosyl)arenes by stereospecific counjugate-addition of organocopper reagents to peracetylated hex-1-enopyran-3-uloses

Abstract The reaction of peracetylated 1,5-anhydro-2-deoxyhex-1-eno-3-uloses with higher-order cyanoorganocuprate in oxolane at low temperature in the presence of acetic anhydride afforded the corresponding glycosylarenes in good yields. A complete stereocontrol could be achieved, leading to the α- d anomer without epimerization at C-4.The configuration of the new products was established by spectroscopic methods and transformation into the crystalline parent oximes, the conformation of which is discussed in terms of stereoelectronic effects.

Convenient Preparation of Perbenzylated 2-Azido and 2-N-Acetylamino-2-Deoxy-d-Hexono-1,5-Lactones by Oxidation of the Corresponding Lactols

Abstract 2-Azido-3,4,6-tri-O-benzyl-2-deoxy-d-galacto, gluco and mannopyranoses (1, 2, 3) were oxidized with DMSO in the presence of acetic anhydride. From 1 and 2 the corresponding lactone derivatives were obtained in good yield (89-92%), whereas from 3, glucono-1,5-lactone was obtained (92%) after complete epimerization at C-2. 2-N-Acetylamino-3,4,6-tri-O-benzyl-2-deoxy-d-galacto, gluco and mannopyranoses (7, 8, 9) were obtained from the corresponding 2-azido phenylselenoglycopyranosides (13, 14, 15) by reduction, N-acetylation and hydrolysis catalyzed by mercury trifluoroacetate. Oxidation of 7 and 8 by tetra-n-propylammonium tetra-oxoruthenate (VII) in the presence of 4-methylmorpholine-N-oxide afforded the corresponding lactones in good yield (90%) and high purity. Epimerization at C-2 occurred during oxidation of 9 and perbenzylated d-glucono-1,5-lactone (11) was obtained (90%).

A NOVEL 2'-DEOXYNUCLEOSIDE DESIGNED FOR ENHANCED RECOGNITION OF A.T. BASE-PAIRS

Abstract The title base modified purine deoxynucleoside 1, designed to be incorporated in triplex-forming oligodcoxynucleotides selectively binding to the A.T. base pair, was prepared by non ionic azido-phenylselenylation reaction applied to a 6-vinylpurine substrate.

Studies directed towards the synthesis of miharamycin B

Abstract The northern part of Miharamycin B which differs from the natural product by the absence of a 2-carbon branched chain in the sugar moiety, was prepared by a sequence of selective transformations from methyl 2,3,4-tri-O-benzyl-α-D-gluco-hexodialdo-1,5-pyranoside 3 . The key step is a regioselective glycosylation of 2-aminopurine.