Bernard Gentile

3-C-(Acylméthylène)-3-désoxy-1,2:5,6-di-O-isopropylidène-α-d-ribo- et -xylo-hexofuranoses

Abstract 1,2:5,6-Di-O-isopropylidene-α- d -ribo- and -xylo-hexofuranos-3-uloses (1 and 2) were treated with the following stabilized phosphorus ylides: (ethoxycarbonylmethylene)triphenylphosphorane, (acetylmethylene)triphenylphosphorane, and (benzoylmethylene)triphenylphosphorane. With the keto sugar having a xylo configuration, a mixture of the geometrical isomers of expected α,β-unsaturated esters or of the enones was obtained in excellent yield. In addition to the usual compounds, the keto sugar 1 gave side-products originating from an epimerization at C-4 or from an allylic prototropy. When 1 and 2 were treated with an excess of (formylmethylene)-triphenylphosphorane, they not only gave monoalkylidenation products, but they also underwent a dialkylidenation. During the course of these reactions, epimerization at C-4 in the unusual direction xylo to ribo, as well as in the more common direction, ribo to xylo, was observed. In dimethyl sulfoxide solution, the cis-3-C-(acetylmethylene)-3-deoxy-1,2:5,6-di-O-isopropylidene-α- d -ribo- and -xylo-hexofuranoses underwent, at an appreciable speed at temperatures above 100°, an allylic prototropic reaction leading to the formation of 3-deoxy-1,2:5,6-di-O-isopropylidene-3-C-(2-oxopropyl)-α- d -erythro-hex-3-enofuranose. The kinetic parameters of the allylic transposition reactions of these two compounds are very similar.

1,2-O-Isopropylide`ne-pentodialdofuranoses

Abstract 1,2- O -Isopropylidenepentodialdofuranoses having ribo , lyxo , and arabino configurations, as well as analogs having one (C-3) or two (C-3 and C-4) hybrid sp 2 carbon atoms were synthesized. The orientation of these compounds at the C-4 C-5 bond is practically independent of the modifications of the substitution at C-3. It seems to be directed by orbital factors favoring a conformer having a carbonyl group and an O-C-4 bond nearly eclipsed.

Synthesis of photoaffinity labeling derivatives of d-glucose and d-galactose

Abstract Two new photoaffinity reagents having photoreactive groups attached to C-6 of d -galactose have been prepared. 6- N -(4-Azido-2-hydroxybenzoyl)- d -glucopyranosylamine and 6- N -(4-azido-2-hydroxybenzoyl)- d -galactopyranosylamine were synthesized by acylation of the protected amino sugars with 4-azidosalicoyl chloride or by treating the amine with 4-azidosalicylic acid. Subsequent iodination of the aromatic ring yields the diiodo derivative. Deprotection yields the sugar derivatized at C-6 by the diiodinated photoaffinity reagent. Photoaffinity reagents having high specific activity may be prepared by this procedure.