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We report the diastereoselective and chromatography-free syntheses of four 2-phenyl-6-alkyl-3-aminopiperidines. Ring construction was accomplished through a nitro-Mannich reaction linking a nitroketone and phenylmethanimine, followed by a ring-closure condensation. Relative stereocontrol was achieved between C-2 and C-3 by kinetic protonation of a nitronate or by equilibration of the nitro group under thermodynamic control. Stereocontrol at C-6 was accomplished by utilizing a variety of imine reduction methods. The C-2/C-6-cis stereochemistry was established via triacetoxyborohydride iminium ion reduction, whereas the trans relationship was set either by triethylsilane/TFA acyliminium ion reduction or by Lewis acid catalyzed imine reduction with lithium aluminum hydride.

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Synthesis and Structure-Activity Relationships of Thiotetronic Acid Analogues of Thiolactomycin.-Synthetic efforts to improve the antibacterial activity of thiolactomycin (VI), a thiotetronic acid natural product, via semisynthetic modifications of thiolactomycin [→(XI), (XII)] and 3-acetylthiotetronic acid analogues [→(III), (V)] are described. Some analogues show improved activity over thiolactomycin against Staphylococcus aureus and comparable activity against Pasteurella multocida. -(SAKYA, SUBAS M.; SUAREZ-CONTRERAS, MELANI; DIRLAM, JOHN P.; O'CONNELL, THOMAS N.; HAYASHI, SHIGERU F.; SANTORO, SHERYL L.; KAM-ICKER, BARBARA J.; GEORGE, DAVID M.; ZIEGLER, CARL B.; Bioorg.