Reduced immunotoxicity and preservation of antibacterial activity in a releasable side-chain carbapenem antibiotic.

A carbapenem antibiotic, L-786,392, was designed so that the side chain that provides high-affinity binding to the penicillin-binding proteins responsible for bacterial resistance was also the structural basis for ameliorating immunopathology. Expulsion of the side chain upon opening of the beta-lactam ring retained antibacterial activity while safely expelling the immunodominant epitope. L-786,392 was well tolerated in animal safety studies and had significant in vitro and in vivo activities against methicillin- and vancomycin-resistant Staphylococci and vancomycin-resistant Enterococci.

Synthesis and biological activity of 13-epi-avermectins: potent anthelmintic agents with an increased margin of safety.

Chemical conversion of the potent anthelmintic natural products avermectin B1 (1) and avermectin B2 (3) to the corresponding 13-epi analogs (15 and 9) is described. The novel analogs retain the full potency of the natural products but are substantially safer.

[3H]paraherquamide binding to Caenorhabditis elegans. Studies on a potent new anthelmintic agent.

Paraherquamide was identified recently as a potent anthelmintic agent. In this paper we describe the identification and characterization of a specific, high-affinity paraherquamide binding site in a membrane preparation isolated from the free-living nematode, Caenorhabditis elegans. [3H] Paraherquamide bound specifically to C. elegans membranes with an apparent dissociation constant, Kd, of 263 nM. A series of paraherquamide analogs were examined, and their relative affinity for the paraherquamide binding site correlated with their nematocidal activity. Phenothiazines were the only other class of anthelmintics tested which inhibited specific [3H]paraherquamide binding. These results suggest that the anthelmintic activity of paraherquamide and phenothiazine is mediated via an interaction with a common binding site.

Selective estrogen receptor modulator medicinal chemistry at Merck. A review.

Selective estrogen receptor modulators (SERMs) have been the subject of extensive medicinal chemistry efforts at several pharmaceutical companies, including Merck. The Merck effort produced a wide variety of SERMs including ER-alpha selective antagonists and ER-beta agonists in addition to balanced (non-selective) analogs. This article will provide a broad overview of the Merck SERM medicinal chemistry effort as published in the literature through early 2008.

Synthesis and antibacterial activity of O-methyl derivatives of azalide antibiotics: I. 4", 11 and 12-OMe derivatives via direct methylation.

A series of O-Me derivatives of 9-deoxo-8a-aza-8a-homoerythromycin has been prepared and evaluated for antibacterial activity. The relative rates of methylation of the four available hydroxyls (4", 6, 11 and 12) in 2',3'-bis-Cbz protected 9-deoxo-8a-aza-8a-homoerythromycin were compared to those given in a published report for the similarly protected 9a-azalide. An incongruity in the results prompted reinvestigation of the O-methylation of the 9a-azalide, and an error in structure assignment in the published report was discovered: the compound reported as the 6-OMe-9a-azalide has been determined to be the 12-OMe derivative.

Synthesis and antibacterial activity of O-methyl derivatives of azalide antibiotics: II. 6-OME derivatives via clarithromycin.

Direct O-methylation of various derivatives of 9-deoxo-8a- and 9a-aza-8a-homo-erythromycin (2',3'-bis-Cbz protected) gives 6-OMe derivatives only in a small number of special cases. The 6-OMe-azalides can, however, be synthesized beginning from clarithromycin.

Synthesis of gem-difluoro-avermectin derivatives: potent anthelmintic and anticonvulsant agents.

A series of gem-difluoro-avermectin derivatives was synthesized from the corresponding ketones at positions 4", 4', 13, and 23 using diethylaminosulfur trifluoride (DAST). These fluorinated avermectins exhibit potent antiparasitic activity in a new Haemonchus contortus larval assay and are equipotent to ivermectin. In addition, 23-gem-difluoro-ivermectin displays useful anticonvulsant activity in mouse models.

Synthesis and activity of 2-(sulfonamido)methyl-carbapenems: discovery of a novel, anti-MRSA 1,8-naphthosultam pharmacophore.

A series of 1beta-methyl carbapenems substituted at the 2-position with lipophilic, acyclic and cyclic (sulfonamido)methyl groups was prepared and evaluated for activity against resistant gram-positive bacteria. From these studies, the 1,8-naphthosultamyl group emerged as a novel, PBP2a-binding, anti-MRSA pharmacophore worthy of further exploration.

Synthesis and properties of 2-(naphthosultamyl)methyl-carbapenems with potent anti-MRSA activity: discovery of L-786,392.

A series of 1beta-methyl-2-(naphthosultamyl)methyl-carbapenems bearing dicationic groups on the naphthosultamyl moiety was prepared and evaluated for activity against resistant gram-positive bacteria. Based on a combination of excellent in vitro antibacterial activity, acceptable mouse acute toxicity, and a desirable fragmentation pattern on beta-lactam ring opening, the analog 2g (L-786,392) was selected for extended evaluation.