Reversible addition-fragmentation transfer substrates

In recent years, focus has moved to the use of living radical polymerization techniques such as atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain transfer (RAFT) for the production of well-defined polymer coatings. Both the grafting from and grafting to approaches have been explored for the attachment of MPC-based polymers onto a variety of substrates. Grafting from requires the incorporation of initiator sites onto the biomaterial surface prior to the polymerization reaction. This usually involves a series of... 

Baum M, Brittain WJ Synthesb of polymer brushes on silicate substrates via reversible addition fragmentation chain transfer technique. Macromolecules 35 610—615, 2002. 

The transketolase (TK EC 2.2.1.1) catalyzes the reversible transfer of a hydroxy-acetyl fragment from a ketose to an aldehyde [42]. A notable feature for applications in asymmetric synthesis is that it only accepts the o-enantiomer of 2-hydroxyaldehydes with effective kinetic resolution [117, 118] and adds the nucleophile stereospecifically to the re-face of the acceptor. In effect, this allows to control the stereochemistry of two adjacent stereogenic centers in the generation of (3S,4R)-configurated ketoses by starting from racemic aldehydes thus this provides products stereochemically equivalent to those obtained by FruA catalysis. The natural donor component can be replaced by hydroxy-pyruvate from which the reactive intermediate is formed by a spontaneous decarboxylation, which for preparative purposes renders the overall addition to aldehydic substrates essentially irreversible [42]. 

---