Heterocyclic combinatorial library design

A linker originally designed for solid-phase synthesis of peptides is the backbone amide linker (11) (BAL), this anchoring approach has now been extended to the combinatorial synthesis of diverse amide [31], hydroxamate [32], oligosaccharide [33] and heterocyclic small molecule libraries [34-36]. 

A particularly effective strategy for the design of new heterocyclic libraries employs a tandem N-acyliminium ion cyclization/nucleophilic addition for ring-forming processes [108] (Scheme 19). The described methodology provides access to bi-, tri-, and tetracyclic derivatives of l-acyl-3-oxopiperazines. The bicyclic variants in particular represent an interesting probe for a constrained type I p-turn motif with potential for combinatorial diversification. 

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