Abstract:
As part of a programme directed towards the synthesis of the bicyclic spiroimine ring systems present in the marine toxins, the spirolides and gymnodimine, a study of the Diels-Alder addition of dienes (165), (180), cyclopentadiene (181) and 2,3-dimethyl-1,3- butadiene (182) to a-methylene lactam (121) was undertaken. A systematic study of the use of a variety of Lewis acids to catalyze the Diels-Alder reaction was carried out. Extension of this work to an asymmetric variant of these Diels-Alder reactions was investigated using the chiral Lewis acids [(S,S)-'Bu-BOX]Cu(OTf)2 and [(S^-'Bu- BOX]Cu(SbF6)2- Additional attempted transformations, included the use of a Gassman strategy along with an organocatalytic approach to prepare the spiroimine unit of the spirolides. Finally a regioselective and versatile method for the synthesis of model spirocyclic scaffolds (244-248) and (249-253) via 1,3-dipolar cycloaddition and addition of various carbon nucleophiles to a novel spirocyclic nitrone (243) is reported.