The present thesis has been divided into two sections The first part concerns the isolation and identification of the secondary metabolites of the leaves and pecioles of Echinodorus grandiflorus from Curitiba-PR. Conventional phytochemical analysis resulted in the identification of 11 compounds : phytol (8), hardwickic acid, methyl ester (14a), echinoic acid (16), four clerodane derivatives 17a, 18, 19 and 20a, two steroid derivatives and two fatty acids. Compounds 16, 18 and 20a have not been previously reported in the literature. The absolute configuration of clerodane 18 was determined as (-)-16-hydroxycleroda-3,13-dien-16,15-olide-19oic acid, ( 4aa,6a,8aa)-1-carboxy-5(S)-[2(2,5-dihydro-5-hidroxy-2-oxo-4-furanyl)-ethyl-5,6,8a-trimethyl-3, 4, 4a, 5, 6, 7, 8, 8a-octahydro-naphthalene by hemisynthesis using (-)-hardwickic acid , a natural compound of known absolute configuration, as starting material. With the objetive of optimizing a rapid method to control the composition of Echinodorus grandiflorus and Echinodorus macrophyllus both known as "chapéu de couro" and applied in folk medicine as diuretic and to treat rheumatisms, we have first established a valid protocol derivatizing the crude methanolic extracts of Echinodorus grandiflorus in three different ways: 1) silylation with bis-( trimethylsilyltrifluoroacetamid) 2) methylation with diazomethane 3) methylation followed by silylation Evaluation of the three methodologies with the Echinododrus grandiflorus revealed that the methylation produced artefacts by the addition of the diazomethane molecule to the alfa-beta unsaturated carboxylic acid and lactones moieties. The sylilation with bis- (trimethylsilyltrifluoroacetamid) was the derivatization of our choice. The comparison analysis of the GC/MS of the silylated crude extracts of Echinodorus macrophyllus, E. tenellus, E. longipetalus, E. aschersonianus revealed that clerodane and cembranes are characteristic compounds of E. grandiflorus while in the other members of this genus these compounds are in either minor or trace amounts. The second part of this thesis deals with the application of beta pinene and its oxydation products possessing cyclopentane and cychexane moieties to the production of chirons. The experimental results reveal that these substrates are not adequate good candidates to further chemical transformations due to their tendency to rearrange.