| Abstract
| - N-Acyloxyiminium ions generated from 4-substituted l-pyroglutamic esters with 4-(3-butenyl), 4-(3-butynyl), 4-(3-cinnamylmethyl), and 4-allenic tethers undergo rapid Lewis acid mediated carbocyclization to give stereodefined azacyclic compounds depending on the nature of the nucleophilictether. In general, reactions of alkenes and alkynes with terminal alkyl or aryl substituents, aswell as allenes, proceed through transient vinylic carbocations that are attacked internally by theN-Boc group to give tricyclic dihydrooxazinones. Diastereotopic bis-4-(3-butenyl) and 4-(3-butynyl)tethers undergo stereochemically controlled attack favoring an antiperiplanar rather than synclinalapproach to give enantiopure 6-halo octahydroindole-2-carboxylic acids and 6-halo hexahydroindole-2-carboxylic acids as their methyl esters, respectively. The aza bicyclic and tricyclic compoundsare excellent scaffolds for diversification.
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