Chromium complexes with carbohydrates

Earlier structural studies of carbohydrates by CD involved introduction of suitable chromophores into the sugar molecule thereby affording derivatives which exibit Cotton effects. These include, among others, xanthates (4-8) or azides (9). Later it was found that some metal ions (10), i.e. copper (11,13), vanadate (14), chromium (15), molybdate (16-22), nickel (23) or cobalt (24,25) ions form complexes with carbohydrates, which show appreciable Cotton effects. 

Chung et al. [179] demonstrated that carbohydrate auxiliaries can also be employed for the preparation of chiral (arene)tricarbonyl complexes, which are useful intermediates in organic synthesis. The D-glucose-derived benzylidene acetal 284 was reacted with hexacarbonyl chromium... 

Weyershausen, B, Nieger, M, Doetz, K H, Stereospecific exo-selective Diels-Alder reactions with carbohydrate-functionalized a-exo-methylene-2-oxacyclopentylidene chromium complexes, J. Org. Chem., 64, 4206-4210, 1999. 

P. J. Garegg and B. Samuelsson, Oxidation of primary and secondary alcohols in partially protected sugars with the chromium trioxide-pyridine complex in the presence of acetic anhydride, Carbohydr. Res., 67 (1978) 267-270. 

An interesting example of a chiral aryl chromium complex enhancing diastereoselectivity in carbohydrate auxiliary-influenced acrylate Diels Alder reactions has been described by Shing and co-workers. Thus, for example, diethylalumi-nium chloride catalyzed reactions of complex 385 with 2-methylbutadiene... 

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