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. Consequently, novel derivatives possessing a para-heteroaromatic-phenylthio group at the C-7 position exhibited significantly strong activities against S. pneumoniae and S. pyogenes with an erm gene even when compared with those of telithromycin. Finally, in vivo efficacy of selected two derivatives was evaluated in a rat pulmonary infection model with resistant S. pneumoniae with erm + mef genes. One of them exhibited strong and constant in vivo efficacy in this model, and both compounds showed strong in vivo efficacy against resistant S. pneumoniae with a mef gene.

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A new and efficient method for catalytic hydrolysis of thioglycosides was successfully developed. Various thioglycosides were smoothly hydrolyzed to afford the corresponding 1-hydroxy sugars in high yields. The hydrolysis of disaccharides was took place smoothly without accompanying no anomerization of existing glycosidic bond.

A one-pot synthesis of trisaccharides was successfully carried out by combination of two types of the trityl tetrakis(pentafluorophenyl)borate catalyzed stereoselective glycosylation reactions. Selective activation of a glycosyl phenyl carbonate in the presence of a thioglycoside allows two successive glycosyl coupling in one-pot manner to afford several protected trisaccharides, Glcβ1-6Glcβ1-6Glc, in good to high yields.

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