A Divergent Route to Eravacycline.

A convergent route to eravacycline (1) has been developed by employing Michael-Dieckmann cyclization between enone 3 and a fully built and protected left-hand piece (LHP, 2). After construction of the core eravacycline structure, a deprotection reaction was developed, allowing for the isoxazole ring opening and global deprotection to be achieved in one pot. The LHP is synthesized from readily available 4-fluoro-3-methylphenol in six steps featuring a palladium-catalyzed phenyl carboxylation in the last step.

Synthesis and biological evaluation of 8-aminomethyltetracycline derivatives as novel antibacterial agents.

The C-8 position of the tetracyclines has been largely underexplored because of limitations in traditional semisynthetic techniques. Employing a total synthetic approach allowed for modifications at the C-7 and C-8 positions, enabling the generation of structure-activity relationships for overcoming the two most common tetracycline bacterial-resistance mechanisms: ribosomal protection (tet(M)) and efflux (tet(A)). Ultimately, several compounds were identified with balanced activity against both Gram-positive and Gram-negative bacteria, including pathogens bearing both types of tetracycline-resistance mechanisms.

Fluorocyclines. 2. Optimization of the C-9 side-chain for antibacterial activity and oral efficacy.

Utilizing a fully synthetic route to tetracycline analogues, the C-9 side-chain of the fluorocyclines was optimized for both antibacterial activity and oral efficacy. Compounds were identified that overcome both efflux (tet(K), tet(A)) and ribosomal protection (tet(M)) tetracycline-resistance mechanisms and are active against Gram-positive and Gram-negative organisms. A murine systemic infection model was used as an oral efficacy screen to rapidly identify compounds with oral bioavailability.

Fluorocyclines. 1. 7-fluoro-9-pyrrolidinoacetamido-6-demethyl-6-deoxytetracycline: a potent, broad spectrum antibacterial agent.

This and the accompanying report (DOI: 10.1021/jm201467r ) describe the design, synthesis, and evaluation of a new generation of tetracycline antibacterial agents, 7-fluoro-9-substituted-6-demethyl-6-deoxytetracyclines ("fluorocyclines"), accessible through a recently developed total synthesis approach. These fluorocyclines possess potent antibacterial activities against multidrug resistant (MDR) Gram-positive and Gram-negative pathogens.

A Versatile Route to 2-Substituted Cyclic 1,3-Dienes via a Copper(I)-Catalyzed Cross-Coupling Reaction of Dienyl Triflates with Grignard Reagents.

A general synthesis of 2-substituted cyclic 1,3-dienes in two steps from alpha,beta-unsaturated ketones has been developed. Formation of a dien-2-yl triflate followed by a copper(I)-catalyzed cross-coupling reaction with a Grignard reagent gives 2-substituted dienes in fair to excellent yields. Alkyl, aryl, and allyl Grignard reagents can be used.

Total Synthesis of (-)-Cylindricine C.

(-)-Cylindricine C has been synthesized from commercially available ()-(-)-1,2,4-butanetriol in 11 steps with an overall yield of 12%. The key step utilizes a CrCl reduction of an azide to form the corresponding amine with a subsequent double Michael addition to create the tricyclic skeleton of cylindricine from a monocyclic substrate.