Dominique Schwarzenbach

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.

Sucres insaturés fluorés

Abstract Treatment of 1,2:5,6-di- O -isopropylidene-α- d - ribo - and xylo -hexofuranos-3-uloses with (difluoromethylene)triphenylphosphorane and (chlorofluoromethylene)-triphenylphosphorane gave unsaturated, ramified halogeno sugars in good yield. Treatment of the chlorofluoromethylene derivatives with lithium aluminum hydride gave stereospecifically the corresponding fluoromethylene derivatives with inversion of configuration at the double bond. The configuration was determined by 1 h- and 19 F-n.m.r. spectrometry.

Synthesis of part of the antigenic repeating-unit of streptococcus pneumoniae type II

Abstract Condensation of methyl 4- O -acetyl-3- O -(2,3,4-tri- O -acetyl-α- l -rhamnopyranosyl)-α- l -rhamnopyranoside with 2,3,4,6-tetra- O -benzyl-α- d -glucopyranosyl chloride gave a mixture of methyl O -[2,3,4,6-tetra- O -benzyl-α- ( 4 ) and -β- d -glucopyranosyl]-(1→2)- O -[(2,3,4-tri- O -acetyl-α- l -rhamnopyranosyl)-(1→3)]-4- O -acetyl-α- l -rhamnopyranoside ( 9 ) in 43:7 proportion in 63% yield. After chromatographic separation, removal of the benzyl and acetyl groups gave methyl O -α- d -glucopyranosyl-(1→2)-[ O -α- l -rhamnopyranosyl-(1→3)]-α- l -rhamnopyranoside and the β anomer. Removal of benzyl groups of 4 was followed by tritylation, acetylation, and detritylation of the α- d -glucopyranosyl group, and finally condensation with benzyl (2,3,4-tri- O -benzyl- d -glucopyranosyl chloride)uronate gave a mixture of two tetrasaccharides ( 15 and 16 ), containing the α- and β- d -glucopyranosyluronic acid groups in the ratio 81:19, and an overall yield of 71%. After chromatographic separation, alkaline hydrolysis and hydrogenation of 15 gave methyl O -α- d -glucopyranosyluronic acid-(1→6)- O -α- d -glucopyranosyl-(1→2)-[ O -α- l -rhamnopyranosyl-(1→3)]-α- l -rhamnopyranoside. The β- d anomer was obtained by similar treatment of 16 . 6- O -α- d -glucopyranosyluronic acid-α,β- d -glucopyranose was synthesized as a model compound.