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The development of catalytic enantioselective carbon-carbon bond-forming reactions, particularly those that produce quaternary stereocenters, is one of the most difficult challenges in stereoselective organic synthesis. 1,2 In 1970, Steglich reported that 4-(dimethylamino)pyridine (DMAP) and 4-(pyrrolidino)pyridine (PPY) catalyze the rearrangement of O-acylated azlactones to their C-acylated isomers, thereby generating both a new carbon-carbon bond and a new quaternary stereocenter (eq 1). 3,4 The products Table 2. Enantioselective Rearrangements of O-Acylated Azlactones Catalyzed by (-)-PPY* Scheme 1

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PNU-286607 is the first member of a promising, novel class of antibacterial agents that act by inhibiting bacterial DNA gyrase, a target of clinical significance. Importantly, PNU-286607 displays little cross-resistance with marketed antibacterial agents and is active against methicillin-resistant staphylococcus aureus (MRSA) and fluoroquinoline-resistant bacterial strains. Despite the apparent stereochemical complexity of this unique spirocyclic barbituric acid compound, the racemic core is accessible by a two-step route employing a relatively obscure rearrangement of vinyl anilines, known in the literature as the "tert-amino effect." After a full investigation of the stereochemical course of the racemic reaction, starting with the meso cis-dimethylmorpholine, a practical asymmetric variant of this process was developed.

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