Carbohydrates have a widespread Occurrence in nature and are indispensable compounds to living organisms.' Naturally rare carbohydrates have also proved to be involved in many glycoproteins, glycolipids, and antibiotics and play important roles in various biological processesS2 Further, in some enzymatic reactions of carbohydrates, alkali, alkaline earth, and some of transition metal ions were suggested to act in cooperation with sugars.3 In this regard, it is very important to investigate the interactions between sugars and metal ions including the stereochemical behavior of sugars in transition metal complexes. We have studied the synthesis and characterization of nickel(I1) and cobalt(II1) complexes containing N-glycosides derived from the reaction of sugars and diamine^.^ Here, we wish to report a synthesis of novel seven-coordinated cage-type cobalt complexes containing N-glycosides from mannose-type aldoses (D-mannose or L-rhamnose (=6-deoxy-~-mannose)) and tris(Zaminoethy1)amine (tren) and an unprecedented inversion of configuration around the metal center induced by an interaction between sugars and tetrahedral oxoanions. A methanolic solution containing D-mannose (D-Man) or L-rhamnose (L-Rha) (4 equiv) and tren (1 equiv) was incubated at 60 OC for 1 h. Then, CoXz.6HzO (X = C1-, B r ) (1 equiv) was added to the solution and the mixture was refluxed for 1 h. The resultant solution was purified on a Sephadex LH-20 gel permeation column. The wine-red major band was collected and concentrated, and an addition of ethanol gave microcrystals of [Co((aldose)3-tren)]Xz.nHzO (la, aldose = D-Man, X = C1-; lb, aldose = L-Rha, X = C1-; 2a, aldose = D-Man, X = B r ; 2b, aldose = L-Rha, X = B r ) , where (aldose)3-tren is tris(N-aldosyl2-aminoeth~l)amine.~ When CoSOcnHzO was used as a metal source, similar complexes formulated as [C~((aldose)~-tren)]S04.nH20 (3a, aldose = D-Man; 3b, aldose = L-Rha) were ~ b t a i n e d . ~ The electronic absorption (AB) spectra of 1-3 in solution showed a characteristic band around 20 X lo3 cm-I, corresponding to d-d transitions of Co(I1) ions. The transmittance spectra (Nujol mull) also showed a similar absorption indicating no significant structural change around the metal on dissolution. In the circular dichroism (CD) spectra, a large Cotton effect was observed at about 20 X 103 cm-l, suggesting the coordination of sugar moieties to the cobalt ion. Further, it should be noted that the sign of the Cotton effect of 1 and 2 containing halide