Chemoenzymatic syntheses of cis- and trans-3-hydroxy-5-methylpiperidin-2-ones

An approach to the enantioselective synthesis of cis- and trans-3-hydroxy-5 -methylpiperidin-2-ones from racemic methyl 4-methyl-5-nitro-2-oxopentanona te 8 is described via the first example of a lactate dehydrogenase catalyse d combined kinetic resolution and reduction of a 2-oxo acid. In an alternat ive approach, stereoselective conjugate addition of nitromethane to a croto nyl camphorsultam gave access to the enantiopure 2-oxo esters (S)-8 and (R) -8 which, in turn, may be converted to the 3-hydroxy-5-methyl delta-lactams . (C) 2000 Elsevier Science Ltd. All rights reserved.