Synthesis and structure-activity relationships of novel lincomycin derivatives. Part 2. Synthesis of 7(S)-7-deoxy-7-(4-morpholinocarbonylphenylthio)lincomycin and its 3-dimensional analysis with rRNA

Lincosamide Antibiotics: Structure, Activity, and Biosynthesis

Lincosamides are naturally occurring antibiotics isolated from Streptomyces sp. Currently, lincomycin A and its semisynthetic analogue clindamycin are used as clinical drugs. Due to their unique structures and remarkable biological activities, derivatizations of lincosamides via semi-synthesis and biosynthetic studies have been reported. This review summarizes the structures and biological activities of lincosamides, and the recent studies of lincosamide biosynthetic enzymes.

Characterization of compound A, a novel lincomycin derivative active against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of causative bacteria for hospital- and community-acquired infections. In order to overcome MRSA infection, we synthesized compound A, a lincomycin derivative, and evaluated the biological properties. The MIC₅₀ and MIC₉₀ values of compound A against MRSA clinical isolates, which were susceptible to clindamycin, from infected skin in Japan were 0.12 and 0.25 μg ml^-1, respectively, and those against hospital-acquired MRSA with clindamycin resistance were 1.0 and 2.0 μg ml^-1, respectively. Linezolid non-susceptible MRSA selected in the laboratory had mutations in the 23S rRNA gene and exhibited cross-resistance to compound A. MRSA non-susceptible to compound A selected in laboratory was not cross-resistant to linezolid, implying that the binding site to 23S rRNA partly overlaps with clindamycin and linezolid. The in vivo efficacies of compound A against mouse skin abscess model infected with clindamycin-susceptible and -resistant MRSA were superior to those of clindamycin and linezolid, respectively. The well-known linezolid-induced myelosuppression is caused by its inhibitory effect on mitochondrial function, but inhibition was weaker for compound A than that of linezolid. In short, compound A has broader anti-MRSA activities than clindamycin and linezolid due to additional binding site, and demonstrated preferable safety profile as a potential anti-MRSA drug.

Synthesis and antibacterial activity of novel lincomycin derivatives. IV. Optimization of an N-6 substituent

The design and synthesis of lincomycin derivatives modified at the C-6 and C-7 positions are described. A substituent at the C-7 position is a 5-aryl-1,3,4-thiadiazol-2-yl-thio group that generates antibacterial activities against macrolide-resistant Streptococcus pneumoniae and Streptococcus pyogenes carrying an erm gene. An additional modification at the C-6 position was explored in application of information regarding pirlimycin and other related compounds. These dual modifications were accomplished by using methyl α-thiolincosaminide as a starting material. As a result of these dual modifications, the antibacterial activities were improved compared with those of compounds with a single modification at the C-7 position. The antibacterial activities of selected compounds in this report against macrolide-resistant S. pneumoniae and S. pyogenes with an erm gene were superior to those of telithromycin.

Synthesis and antibacterial activity of novel lincomycin derivatives. III. Optimization of a phenyl thiadiazole moiety

Lincomycin derivatives that have a 5-(2-nitrophenyl)-1,3,4-thiadiazol-2-yl thio moiety at the 7-position were synthesized. 5-Substituted 2-nitrophenyl derivatives showed potent antibacterial activities against Streptococcus pneumoniae and Streptococcus pyogenes with erm gene. Antibacterial activities of the 4,5-di-substituted 2-nitrophenyl derivatives were generally comparable to those of telithromycin (TEL) against S. pneumoniae with erm gene and clearly superior to those of TEL against S. pyogenes with erm gene. Compounds 6 and 10c that have a methoxy group at the 5-position of the benzene ring exhibited activities comparable to TEL against Haemophilus influenzae. These results suggest that lincomycin derivatives modified at the 7-position would be promising compounds as a clinical candidate. We would like to dedicate this article to the special issue for late Professor Dr. Hamao Umezawa in The Journal of Antibiotics.The Journal of Antibiotics advance online publication, 5 July 2017; doi:10.1038/ja.2017.59.

Synthesis and structure-activity relationships of novel lincomycin derivatives part 3: discovery of the 4-(pyrimidin-5-yl)phenyl group in synthesis of 7(S)-thiolincomycin analogs

Novel lincomycin derivatives possessing an aryl phenyl group or a heteroaryl phenyl group at the C-7 position via sulfur atom were synthesized by Pd-catalyzed cross-coupling reactions of 7(S)-7-deoxy-7-thiolincomycin (5) with various aryl halides. This reaction is the most useful method to synthesize a variety of 7(S)-7-deoxy-7-thiolincomycin derivatives. On the basis of analysis of structure-activity relationships of these novel lincomycin derivatives, we found that (a) the location of basicity in the C-7 side chain was an important factor to enhance antibacterial activities, and (b) compounds 22, 36, 42, 43 and 44 had potent antibacterial activities against a variety of Streptococcus pneumoniae with erm gene, which cause severe respiratory infections, even compared with our C-7-modified lincomycin analogs (1-4) reported previously. Furthermore, 7(S)-configuration was found to be necessary for enhancing antibacterial activities from comparison of configurations at the 7-position of 36 (S-configuration) and 41 (R-configuration).