METAL-COMPLEXES OF CARBOHYDRATES - ISOLATION AND CHARACTERIZATION OF COBALT(III) COMPLEXES CONTAINING N-SUBSTITUTED GLYCOSYLAMINE LIGANDS DERIVED FROM ETHANE-1,2-DIAMINE AND GLUCOSAMINE

Reaction between cis- or trans-[Co(en)(2)Cl-2](+) (en = ethane-1,2-dia mine) and D-glucosamine (2-amino-2-deoxy-D-glucopyranose) in neutral a queous solution results in a very complicated product mixture includin g as a major component several isomeric complex ions in which the co-o rdination sphere is formally made up of two ethane-1.2-diamine units a nd one sugar unit. Separation of these complexes by ion-exchange chrom atography, and subsequent spectroscopic and structural studies have sh own that they are diastereomeric forms in which the co-ordination sphe re actually contains one bidentate ethane-1,2-diamine chelate and a mu ltidentate ligand which is an N-(2'-aminoethyl)amino-substituted glyco sylamine derived from glucosamine. fructosamine or mannosamine. The pr esence of the fructosamine moiety reveals that the complex formation r eaction is accompanied by the Amadori rearrangement of glucosamine, wh ile the presence of the mannosamine moiety indicates that this rearran gement may be reversible and possibly stereospecific in particular dia stereoisomers. Crystal structure determinations have definitively char acterised eight of the reaction products as: 1 a complex of the 1-N-(2 '-aminoethyl)amino-substituted glucosamine in which the sugar, althoug h chelated to the metal as part of a tridentate ligand, is in its open -chain form and in which the four nitrogen atoms derived from the orig inal two ethane-1 ,a-diamine units are essentially coplanar; 2 a compl ex of tridentate 1-N-(2'-aminoethyl)amino-substituted glucosamine in w hich the sugar has its pyranose form and the chelate edges spanned by the original ethane-1,2-diamine units are in the Delta configuration; 3 a complex of 1-N-(2'-aminoethyl)amino-substituted glucosamine in whi ch the sugar is in its open-chain form and the ligand is bound in a qu adridentate manner, with the chelate edges spanned by the original :et hane-1,2-diamine units in the Delta configuration; 4 a complex of 1-N- (2'-aminoethyl)amino-substituted mannosamine in which the sugar has a furanose form and is part of a quadridentate ligand, and the chelate e dges spanned by the original ethane-1,2-diamine units are in the Delta configuration; 5 a complex of quadridentate -(2'-aminoethylamino)-1-d eoxy-fructopyranosylamine in which the chelate edges spanned by the or iginal ethane-1,2-diamine units are in the Delta configuration; 6 a co mplex of quadridentate -(2'-aminoethylamino)-1-deoxy-fructofuranosylam ine in which the chelate edges spanned by the original ethane-1,2-diam ine units are in the Delta configuration; 7 the same complex as 6 but in the form where its co-ordinated sugar hydroxyl group is deprotonate d; and 8 a complex of 1-(2'-aminoethylamino)-1-deoxyfructopyranosylami ne in which the chelate edges spanned by the original ethane-1,2-diami ne units are in the Delta configuration.