A reductive cyclization approach to (-)-histrionicotoxin 235A and lepadiformine B

The first part of the dissertation details investigations into a reductive cyclization approach to (--)-histrionicotoxin. Assembly of the spiropiperidine core was accomplished by a convergent nitrile anion alkylation and subsequent diastereoselective reductive cyclization. Exploration of several phosphate and sulfonate leaving groups for the reductive cyclization was undertaken. Complementary diastereoselectivity was obtained from cyclization of the chloride and thus both spiropiperidine epimers were prepared. Attempts to install the (Z)-enyne side chains present in (--)-histrionicotoxin are described.;The second part of the dissertation presents an investigation into the stereodivergent nature of the phosphate verses chloride reductive cyclization by application to spiropyrrolidines. An account of the attempted enantioselective synthesis of lepadiformine B is described.