This thesis consists of four chapters. The first chapter, which is a General Introduction, deals with (i) the nature of secondary metabolites and (ii) the terpenoids and aromatic constituents of the liverworts. Chapter 2 describes several efforts to synthesise a lunularic acid derivative which occurs in the liverwort Plagiochila spinulosa. A Wittig reaction of 2-nitroveratraldehyde and 4-methoxybenzyl phosphonium chloride afforded a mixture of stilbenes which on reduction gave 2-amino-3,4,4'-trimethoxybibenzyl. This amino-bibenzyl was subjected to a Sandmeyer reaction in the hope of producing 2-cyano-3,4,4'-trimethoxybibenzyl. Unfortunately, the desired compound was obtained only in very low yield. The major product was 3,5,6-trimethoxy- 9,10-dihydrophenanthrene, the result of a Pschorr cyclisation. A similar Wittig route was used to prepare 2- bromo-3,4,4'-trimethoxybibenzyl. Attempts at carboxylation resulted only In debromination. Chapter 3 concerns a discussion of the constituents of Plagiochila spinulosa. Five dihydrophenanthrene derivatives were isolated together with methyl 2-methyl-3,4-methylene-dioxy-6-methoxybenzoate and an unusual natural product spinuloplagin B which is a diterpenoid-bibenzyl conjugate. A synthesis of 2-hydroxy-3,7-dimethoxy-9,10,-dihydrophen-anthrene is also described. The final chapter considers the metabolites of Frullania tamarisci. In addition to the known compounds (-) frullanolide and tamariscol, a new dimeric sesquiterpenoid lactone was isolated
