Recent advances in the medicinal chemistry of novel erythromycin-derivatized antibiotics.

Development of novel erythromycin-based antibiotics has been one of the most studied topics in the past three decades. Such tremendous efforts have generated a number of beneficiary drugs such as clarithromycin, azithromycin and telithromycin. However, widespread application of antibiotics in clinical practice has triggered an increasing emergence of bacterial resistance. Therefore, discovery of novel macrolide antibiotics to suppress the resistance is urgent for human healthcare. This review focuses on advances in the area since 2004.

Synthesis of 3,6-bicyclolides: a novel class of macrolide antibiotics.

The synthesis of 3,6-bicyclolides from erythromycin A oxime is described. This novel class of bridged bicyclic macrolides demonstrates potent in vitro and in vivo activities against a broad spectrum of bacteria including resistant respiratory tract pathogens.

Design, synthesis, and antibacterial activities of novel 3,6-bicyclolide oximes: length optimization and zero carbon linker oximes.

We designed and synthesized a series of novel 3,6-bicyclolide oximes, possessing linkers of varying lengths to the secondary binding site. The E isomers exhibited excellent antibacterial profiles against a broad spectrum of resistant pathogens.

Total synthesis of the ristocetin aglycon.

The first total synthesis of the ristocetin aglycon is described employing a modular and highly convergent strategy. An effective 12-step (12% overall) synthesis of the ABCD ring system 3 from its amino acid subunits sequentially features an intramolecular aromatic nucleophilic substitution reaction for formation of the diaryl ether and closure of the 16-membered CD ring system (65%), a respectively diastereoselective (3:1, 86%) Suzuki coupling for installation of the AB biaryl linkage on which the atropisomer stereochemistry can be further thermally adjusted, and an effective macrolactamization (51%) for closure of the 12-membered AB ring system. A similarly effective 13-step (14% overall) synthesis of the 14-membered EFG ring system 4 was implemented employing a room-temperature intermolecular S(N)Ar reaction of an o-fluoronitroaromatic for formation of the FG diaryl ether (69%) and a key macrolactamization (92%) with formation of the amide linking residues 1 and 2. The two key fragments 3 and 4 were coupled, and the remaining 16-membered DE ring system was closed via diaryl ether formation to provide the ristocetin tetracyclic ring system (15 steps, 8% overall) enlisting an unusually facile (25 degrees C, 8 h, DMF, >/=95%) and diastereoselective (>/=15:1) aromatic nucleophilic substitution reaction that benefits from substrate preorganization.

A new and improved method for deglycosidation of glycopeptide antibiotics exemplified with vancomycin, ristocetin, and ramoplanin.

A general method for the deglycosidation of glycopeptide antibiotics has been developed. Treatment of vancomycin, ristocetin, and ramoplanin with anhydrous HF results in efficient cleavage of the sugars to provide the corresponding aglycons in high yield.