HYDROXY-FUNCTIONALIZED DENDRITIC BUILDING-BLOCKS

A convenient and practical multi-gram procedure for the synthesis of s econd- (G2; 4a, 5a, 5d) and third-generation (G3; 6a) dendrons with or thogonally protected functional groups in the periphery (hydroxy) and at the focal point (carboxylic acid) is described. It uses the amply a vailable first-generation dendrons with amine and carboxylic ester fun ctions (1) and tetrahydropyranyl-protected hydroxy and carboxylic acid functions (2b, 3), respectively, which are connected via amides by pe ptide methods. Purification is either done by recrystallization or sim ple filtration through silica gel and yields the products as analytica lly pure materials on a several-gram scale (even for G3). The dendrons ' protective groups are proven to be orthogonal (500-MHz NMR) which ma kes them useful components (building blocks) of a future dendron const ruction kit for a versatile synthesis of, for example, dendronized pol ymers.