The roots and rhizomes of Southeast Asian plants in the Stemonaceae family are a rich source of alkaloid extracts long used in Chinese folk medicine as antiparasitic agents, and as miticides in primitive veterinary practice. The numerous individual alkaloids isolated from these extracts possess two common features, a fused 5,7 saturated pyrroloazepine ring and one or more fused or attached alpha-methylbutyrolactone rings. These features present interesting problems in chemical synthesis and improvements in methods for elaboration of these heterocyclic systems leading to general methods for the preparation f the known Stemonacteae alkaloids are broad objectives of this research. For construction of the lactone ring, an alkene annulation reaction initiated by manganese(III) oxidation of carboxylic acid derivatives will be studied using model compounds and applied to the synthesis of two specific Stemonaceae alkaloids, croomine (A) and stenine (B). A second reaction, an unusual [4 + 2] intramolecular cycloaddition will be similarly studied, first using models, and then applied to the construction of the tricyclic homolilolidine nucleus of stenine. Although the planned routes are not entirely stereospecific, the projected routes to croomine and stenine comprise less than 15 steps each.
