Some carbohydrate derivatives of ferrocene

Abstract

Some carbohydrate derivatives of ferrocene have been synthesised with regard to their possible use as water-soluble sources of iron in biological systems. Ferrocenylmethyl and ferrocenylethyl B-D-glucopyranosides have been prepared by the Koenigs-Knorr method. The former was also prepared by a modified Fischer synthesis. Ferrocenylmethyl B-D-glucopyranoside was rapidly hydrolysed by acid at a rate comparable with the rates for glucofuranosides. An analysis of the properties of ferrocene and the factors influencing the rates of hydrolysis of glycosides indicated a significant polar assistance from the ferrocenylmethyl substituent to the rate of hydrolysis. A Friedel-Crafts reaction between ferrocene and 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide did not yield the desiredglucosyl ferrocene derivative. As an alternative approach to the preparation of the glucosyl ferrocene derivative cyclopentadienylmagnesium bromide was reacted with 2,3,4,6-tetra-O-acetyl-a-D-glucopyranosyl bromide to give 1-(2,3,4,6-tetra-O-acetyl-B-D-glueopyranosyl) cyclopenta-1,3-diiene but an attempted condensation of this product with ferric chloride failed to give the desired ferrocene derivative. Ferrocenemonoaldehyde condensed with D-glucitol to give 2,4-O-ferrocenylidene-D-glucitol. Two isomeric products were isolated and the evidence suggested that they were related as diastereoisomers. Ferrocenemonoaldehyde condensed with D-mannitol to give 1,3-O-ferrocenylidene-D-mannitol and 1,3:4,6-di-O-ferrocenylidene-D-mannitol.The acetals were very acid labile and the constitutional factors influencing the rates of hydrolysis were analysed. Acetylferrocene was reacted with D-mannitol under a variety of conditions but no evidence for ketal formation was obtained. The optical rotatory dispersion of ferrocenylmtethyl B-D-glucopyranoside and 2,4-O-ferrocanylidene-D-glucitol was investigated. Organic two phase paper chromatographic procedure was found suitable for the fractionation of some ferrocene derivatives.