Natural product-like combinatorial libraries based on privileged structures. 1. General principles and solid-phase synthesis of benzopyrans

Herein we report a novel strategy for the design and construction of natural and natural product-like libraries based on the principle of privileged structures, a term originally introduced to describe structural motifs capable of interacting with a variety of unrelated molecular targets. The identification of such privileged structures in natural products is discussed, and subsequently the 2,2-dimethylbenzopyran moiety is selected as an inaugural template for the construction of natural product-like Libraries via this strategy. Initially, a novel solid-phase synthesis of the benzopyran motif is developed employing a unique cycloloading strategy that relies on the use of a new, polystyrene-based selenenyl bromide resin. Once the loading, elaboration, and cleavage of these benzopyrans was established, this new solid-phase method was then thoroughly validated through the construction of six focused combinatorial libraries designed around natural and designed molecules of recent biological interest.