Hyperbranched polyester support

Parquette et al. reported on a disaccharide synthesis on a hyperbranched polyester support (Boltorn hyperbranched polymer) (16) (Fig. 7.9) [44]. This polymer was obtained in a one-step synthesis and offers low cost, high-loading capacities (8.8 mmol OH-groups g ), and the intermediates were soluble in most aprotic solvents. 

Nonlinear, dendritic or hyperbranched polymers have received considerable attention in recent years. These polymers have seen little use as supports for oligosaccharide synthesis compared to Merrifield or soluble MPEG resins. Nevertheless, some interesting applications of hyperbranched polymers such as hyperbranched polyester and poly(amidoamine) to oligsaccharide synthesis have been reported. 

Hyperbranched Macromolecules. Because of their close structural and synthetic similarities to dendrimers, the comparison of hyperbranched macromolecules with their dendritic analogs has been studied by a number of groups. Ihre and Hult(7i) have recently reported the synthesis and characterization of the dendritic analogs of the commercially available hyperbranched polyesters, Boltron(D(7, based on 2,2-bis(hydroxymethyl)propionic acid, while Moor iJ) has reported a novel solid-supported synthesis of hyperbranched poly(phenylacetylenes) which are the hyperbranched analogs of Moore s well studied phaiylacetylene dendrimers(id). An intriguing study was also reported by Feast into the synthesis and physical properties of hyperbranched analogues of Tomalia s poly(amidoamine) dendrimers (77). 

The potential loading capacity of these hyperbranched polymers is similarly high as for dendrimers (5-14 mmol g ) and some hyperbranched polymers are even commercially available [13,121]. The use of these commercial materials as supports for organic synthesis, however, is hmited due to the chemical stability of the respective polymer backbone (e.g. polyamines, polyesters) and the relatively broad molecular weight distributions (typically PD>2) [13]. Therefore, new hyperbranched species have been developed. 

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