A general and very efficient synthesis of new carbohydrate-substituted porphyrins is described. Reaction of porphyrin 6 with different glycosyl imidates 7 a ± g leads to the formation of carbohydrate-substituted porphyrins 9 a ± g in good yield. Subsequent demetallation and removal of the carbohydrate protection groups leads to the metal-free compounds 11 a ± g. In aqueous solution, compounds 11 a ± g tend to form defined water-soluble aggregates in a self-assembling process. In methanol/water mixtures the aggregation process depends upon the configuration of the anomeric carbon in the carbohydrate moiety. The porphyrinic aggregates are characterized by strong exciton splitting in the Soret absorption spectrum and a red shift for all absorption bands. Interaction of the porphyrinic aggregates with phosphatidylethanolamine and DMPC liposomes leads to very efficient incorporation of mainly monomeric porphyrins 11 a ± g into the liposomes, as was indicated by very large binding constants. At low liposome concentrations noncovalent porphyrin dimers were detected.
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