Modular Synthesis of Radicicol A and Related Resorcylic Acid Lactones, Potent Kinase Inhibitors

Recent progress regarding the bioactivities, biosynthesis and synthesis of naturally occurring resorcinolic macrolides

Macrolides, which comprise a family of lactones with different ring sizes, belong to the polyketide class of natural products. Resorcinolic macrolides, an important subgroup, possess interesting structures and exhibit a wide variety of bioactivities, such as anti-tumor, anti-bacteria, and anti-malaria activities, etc. This review summarizes progress in isolation, bioactivity studies, biosynthesis, and representative chemical syntheses of this group of macrolides in recent decades, encompassing 63 naturally occurring macrolides published in 120 articles.

Inhibition of HSP90 with pochoximes: SAR and structure-based insights

The pochoximes, based on the radicicol pharmacophore, are potent inhibitors of heat shock protein 90 (HSP90) that retain their activity in vivo. Herein we report an extended library that broadly explores the structure-activity relationship (SAR) of the pochoximes with four points of diversity. Several modifications were identified that afford improved cellular efficacy, new opportunities for conjugation, and further diversifications. Cocrystal structures of pochoximes A and B with HSP90 show that pochoximes bind to a different conformation of HSP90 than radicicol and provide a rationale for the enhanced affinity of the pochoximes relative to radicicol and the pochonins.

Divergent syntheses of resorcylic acid lactones: L-783277, LL-Z1640-2, and hypothemycin

The resorcylic acid lactones (RAL) are endowed with diverse biological activity ranging from transcription factor modulators (zearalenone and zearalenol) to HSP90 inhibitors (radicicol and pochonin D) and reversible (aigialomycin D) as well as irreversible kinase inhibitors (hypothemycin and other RAL containing a cis-enone). Our interest in broadening the diversity of this family beyond naturally occurring diversity has led us to seek a general approach that could be used to address the entire spectrum of functionalities present within this family. Herein, we present our efforts on accessing macrocycles bearing an alkane, alkene, or epoxide at the benzylic position from a common benzylic sulfide intermediate to access L-783277, LL-Z1640-2, and hypothemycin.

Synthesis of a resorcylic acid lactone (RAL) library using fluorous-mixture synthesis and profile of its selectivity against a panel of kinases

A library of resorcylic acid lactones (RAL) containing a cis-enone moiety targeting kinases bearing a cysteine residue within the ATP-binding pocket was prepared using a fluorous-mixture synthesis and evaluated against a panel of 19 kinases thus providing important structure-activity trends. Two new analogues were then profiled for their selectivity against a panel of 402 kinases providing the broadest evaluation of this pharmacophores' selectivity.