Merrifield solid-phase synthesis Wang resin

Scheme 50 Solid phase synthesis of penicillin using Merrifield resin and Wang resin...

Solid-phase techniques for the synthesis of bicylic (3-lactams have also been reviewed by Mata. Mata has also reported strategies for the solid-phase synthesis (and functionalization) of such compounds, with the aim of accessing libraries of antibiotics as well as enzyme inhibitors. For example, the feasibility of attaching penicillin antibiotics to Wang or Merrifield resin was investigated. 

The A -diphenylmethylene protection has also been used in the solid-phase mode for the synthesis of either unnatural amino acidst 1 or peptides (Scheme 67)J 1 Thereby, both Merrifield or Wang resins were used and the best base proved to be the organic soluble, nonionic phosphazene bases of Schwesinger, e.g. 2-tert-(butylimino)-2-(ethylamino)-l,3-di-methyl-l,3,2-diazaphosphinane (BEMP). As electrophiles alkyl halides,aldehydes, and Michael acceptors have been used. 

Polystyrene resin, frequently used resin material for solid-phase peptide synthesis (SPPS). The polymeric support for SPPS must be chemically inert, mechanically stable, completely insoluble in the solvents used, and easily separated by filtration. For many applications a copolymer of polystyrene with 1% of divinyl benzene as crosslinker is used. The dry resin beads are able to swell up to the five-or sixfold volume in the different organic solvents mainly used for peptide synthesis (e.g., dichloromethane or dimethylfor-mamide). For SPPS the resin material must be chemically functionalized in order to allow for attachment of a handle/liker (e.g. Wang resin), or the first amino acid (—> Merrifield resin). Hydrophilic tentacle polymers gels (TentaGel) are obtained by grafting polyethylene glycol (PEG) chains with an arbitrary degree of polymerization onto porous polystyrene beads. 

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