Design and Synthesis of Molecular Scaffolds with Anti-infective Activity

A modular and enantioselective synthesis of the pleuromutilin antibiotics

The tricyclic diterpene fungal metabolite (+)-pleuromutilin has served as a starting point for antibiotic development. Semisynthetic modification of its glycolic acid subunit at C14 provided the first analogs fit for human use, and derivatization at C12 led to 12-epi-pleuromutilins with extended-spectrum antibacterial activity, including activity against Gram-negative pathogens. Given the inherent limitations of semisynthesis, however, accessing derivatives of (+)-pleuromutilin with full control over their structure presents an opportunity to develop derivatives with improved antibacterial activities. Here we disclose a modular synthesis of pleuromutilins by the convergent union of an enimide with a bifunctional iodoether. We illustrate our approach through synthesis of (+)-12-epi-mutilin, (+)-11,12-di-epi-mutilin, (+)-12-epi-pleuromutilin, (+)-11,12-di-epi-pleuromutilin, and (+)-pleuromutilin itself in 17 to 20 steps.

Diterpenoids of terrestrial origin

This review covers the isolation and chemistry of diterpenoids from terrestrial as opposed to marine sources and includes labdanes, clerodanes, abietanes, pimaranes, kauranes, cembranes and their cyclization products. The literature from January to December, 2016 is reviewed.

Diastereoselective syntheses of substituted cis-hydrindanones featuring sequential inter- and intramolecular Michael reactions

The hydrindane (bicyclo[4.3.0]nonane) structural motif (1) and related cis-1-hydrindanone skeleton (2) are common substructures in many natural products. Herein, we describe efficient access to substituted cis-1-hydrindanones enabled by a sequence of Michael reactions. A copper-catalyzed intermolecular Michael addition of a cyclic silyl ketene acetal to a β-substituted-α-alkoxycarbonyl-cyclopentenone enables construction of a quaternary center and is followed, after incorporation of an additional Michael acceptor, by a second, intramolecular addition of a nucleophilic β-ketoester. This strategy affords stereoselective access to substituted bicyclic cis-hydrindanone ring systems containing up to three contiguous stereocenters.