Vlado Štimac

Synthesis and biological activity of 4″-O-acyl derivatives of 14- and 15-membered macrolides linked to ω-quinolone-carboxylic unit

The synthesis and antimicrobial activity of a new class of macrolide antibiotics which consist of a macrolide scaffold and a quinolone unit covalently connected by an appropriate linker are described. Optimization of several synthetic steps and structural properties of lead compound 26 are discussed. Promising antibacterial properties of this compound and some of its analogues are reported.

Synthesis and Antibacterial Activity of Isomeric 15-Membered Azalides

A series of 3-keto and 3-O-acyl derivatives of both 6-O-alkyl-8a-aza-8a-homoerythromycin A and 6-O-alkyl-9a-aza-9a-homo-erythromycin A were synthesised and tested against Gram-positive and Gram-negative bacteria. Derivatives of 8a-aza-8a-homoerythromycin A have potent antibacterial activity against not only azithromycin-susceptible strains, but also efflux (M) and inducible macrolide-lincosamide-streptogramin (iMLSB) resistant Gram-positive pathogens, while the corresponding 9a-isomers were less active. Introduction of an additional ring such as 11,12-cyclic carbonate reduced antibacterial activity of both series. 3-Keto and 3-O-(4-nitrophenyl)acetyl derivatives of 6-O-methyl-8a-aza-8a-homo-erythromycin A show typical macrolide pharmacokinetics in preliminary in vivo studies in mice, and their in vivo efficacy is demonstrated.

Synthesis of macrolones with central piperazine ring in the linker and its influence on antibacterial activity

Three macrolides, clarithromycin, azithromycin and 11-O-Me-azithromycin have been selected for the construction of a series of new macrolone derivatives. Quinolone-linker intermediates are prepared by Sonogashira-type C(6)-alkynylation of 6-iodoquinolone precursors. The final macrolones, differing by macrolide moiety and substituents at the position N-1 of the quinolone or by the presence of an ethyl ester or free acid on the quinolone unit attached via a linker. The linker comprises of a central piperazine ring bonded to the 4″-O position of cladinose by 3-carbon ester or ether functionality. Modifications of the linker did not improve antibacterial properties compared to the previously reported macrolone compounds. Linker flexibility seems to play an important role for potency against macrolide resistant respiratory pathogens.

Novel desosamine-modified 14- and 15-membered macrolides without antibacterial activity

Novel modifications of the desosamine sugar of 14- and 15-membered antibacterial macrolides, in which the desosamine was fused with N-substituted-1,3-oxazolidin-2-ones, were developed in order to completely suppress antibacterial activity and make them promising agents for other biological targets. The synthesis of such bicyclic desosamine derivatives, especially 1,3-oxazolidin-2-one formation, was optimized and conducted under mild conditions without a need for protection/deprotection steps for other functional groups. A focused series of novel desosamine-modified macrolide derivatives was prepared and their antibacterial activities tested. It was shown that these macrolide derivatives do not possess any residual antibacterial activity.

Synthesis and biological properties of 4″- O -acyl derivatives of 8a-Aza-8a-homoerythromycin

A series of 4″-O-acyl derivatives of 8a-aza-8a-homoerythromycins A were synthesized and tested against Gram-positive and Gram-negative bacteria. Derivatives of 8a-aza-8a-homoerythromycin A have potent anti-bacterial activity against not only azithromycin-susceptible strains, but also efflux (M) and inducible macrolide–lincosamide–streptogramin-resistant Gram-positive pathogens. These compounds show moderate to high clearance and low oral bioavailability in preliminary in vivo pharmacokinetic studies in rat.