Dendrimer Carbodiimides Mediated Lactamization

Significance

The synthesis of three generations of a novel carbosilane dendrimeric carbodiimide and the use of these molecules in the cyclic lactamization of dipeptides was reported. The dendrimer wedges were synthesized as terminal chlorides using well-established hydrosilylation and Grignard chemistry. The carbodiimide cores were generated either by conversion of the chloride into an amine and an isocyanate followed by coupling to form the urea and subsequent dehydration, or via conversion into an azide and an isocyanate followed by the Staudinger reaction. The three new molecules were tested as mediators of cyclic lactamization and all showed improvement over DCC under relatively concentrated conditions, with the third-generation compound providing the best yields. This result was attributed to a pseudo-dilution effect caused by encapsulation of the dipeptide in the dendrimer. The urea byproduct of the lactamization was recoverable in nearly quantitative yields.