Approaches to the synthesis of natural products and the development of some synthetic methods based on dithiocarbamates

The cytochalasans are a class of fungal metabolites which produce unusual effects on mammalian cells. Chapter One describes an approach to the hydrogenated isoindolone system of these compounds which employs an intramolecular Diets-Alder reaction as the key step. Attempts to prepare 5-benzyl-3-ethoxycarbonyl-l,5-dihydro-2-oxo-2H-pyrrole, an important intermediate in this scheme are discussed. Chapter Two describes some uses of allyl, vinyl, butadienyl and acetylenic dithiocarbamates. Allyl dithiocarbamate formed a sulphur stabilized anion and underwent reaction with a variety of electrophiles. The anion of vinyl dithiocarbamate was also alkylated and the products hydrolysed with titanium tetrachloride to afford the corresponding ketones thus providing an acyl anion equivalent. The parent acetylenic dithiocarbamate was prepared and its anion alkylated. Rearrangement to the corresponding allene was investigated; subsequent hydrolysis would have afforded a carbonyl compound hence creating a g-acylvinyl anion equivalent. Two butadienyl dithiocarbamates were prepared. The anion of the 1-substituted diene reacted with alkyl halides and aldehydes and both dienes underwent the Diets-Alder reaction with a variety of dienophiles. Chapter Three describes a potential route to zoapatanol and montanol, two structurally related diterpenoids isolated from zoapatle, a plant used by the Mexicans to induce labour, abortion and menstruation. The route involves stereospecific displacement of iodide by a cuprate to form a trisubstituted double bond, followed by cyclisation.