Synthesis and SARs of novel lincomycin derivatives Part 5: optimization of lincomycin analogs exhibiting potent antibacterial activities by chemical modification at the 6- and 7-positions.

In order to modify lincomycin at the C-6 and C-7 positions, we prepared target molecules, which have substituted pipecolinic acid at the 6-amino group and a para-substituted phenylthio group at the C-7 position, in application of palladium-catalyzed cross-coupling as a key reaction. As the result of structure-activity relationship (SAR) studies at the 6-position, analogs possessing 4'-cis-(cyclopropylmethyl)piperidine showed significantly strong antibacterial activities against Streptococcus pneumoniae and Streptococcus pyogenes with an erm gene. On the basis of SAR, we further synthesized novel analogs possessing 4'-cis-(cyclopropylmethyl)piperidine by transformation of a C-7 substituent.

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.

Synthesis and structure-activity relationships of novel lincomycin derivatives. Part 1. Newly generated antibacterial activities against Gram-positive bacteria with erm gene by C-7 modification.

We synthesized 7(S)-7-deoxy-7-arylthiolincomycin derivatives possessing a heterocyclic ring at the C-7 position via sulfur atom by either Mitsunobu reaction of 2,3,4-tris-O-(trimethylsiliyl)lincomycin or SN2 reaction of 7-O-methanesulfonyl-2,3,4-tri-O-trimethylsiliyllincomycin. As a result, 7(S)-7-deoxy-7-arylthiolincomycin derivatives 16, 21 and 27 exhibited antibacterial activities against respiratory infection-related Gram-positive bacteria with erm gene, although clindamycin did not have any activities against those pathogens. Furthermore, 7(S)-configuration of lincomycin derivatives was found to be necessary for enhancing antibacterial activities from the comparison results of configurations of 16 (S-configuration) and 30 (R-configuration) at the 7-position.

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.

Lincomycin derivatives, which possess a hetero ring at the C-7 position via sulfur atom, were synthesized by three types of reactions: (1) Mitsunobu reaction of 2,3,4-tris-O-(trimethylsiliyl)lincomycin (1) with the corresponding thiol, (2) SN2 reaction of 7-O-methanesulfonyl-2,3,4-tris-O-(trimethylsiliyl)lincomycin (2) with the corresponding thiol and (3) Pd-catalyzed cross-coupling reaction of 7-deoxy-7-epi-7-mercaptolincomycin (35) with the corresponding aryl halides. As a result, compound 28 had potent antibacterial activities against major pathogens, which caused respiratory infections, even compared with clindamycin. On the other hand, compound 38 showed most potent activities against a variety of Streptococcus pneumoniae with erm gene.