Studies in Natural Products

This thesis consists of four chapters. The first chapter gives a general introduction dealing with the nature of secondary metabolites and the skeletal types found in the Hepaticae. This is followed by an examination of the chemical constituents found in Marsupella species. Three amorphane (muurolane) type sesquiterpenoids were isolated from Marsupella aquatica and their structures shown to be [1R*, 6S*, 10S*] 2R*,3S*-diacetoxyamorpha-4,7(11)-dien-8-one, [1R*, 6S*, 10S*] 2R*,3S*-diacetoxy-7xi 11xi-epoxyamorph-4-en-8-one, and [1R*, 6S*, 10S*] 2S*-acetoxyamorpha-4,7(11)-dien-8-one. The third chapter consists of an investigation of the liverwort Nardia scalaris. Two compounds, ent-(14S)-kaur-16-en-14-yl hydrogen malonate and the longipinane sesquiterpenoid, marsupellone, were isolated. The last chapter deals with a discussion of the Annonaceous acetogenins and some other chemical constituents found in Annonaceous species. A new acetogenin derivative which contains a gamma-lactone ring and an ene-diyne chromophore was isolated for the first time from Milliusa velutina