Isolation and structural elucidation of natural products from Pentas bussei K. Krause, Pentas lanceolata (Forsk.) Deflers and Pentas parvifolia Hiern (Rubiaceae)

Since decades, plant-based drugs have played an essential role in the primary health care of a large part of the world's population. Several chemotherapeutic agents have been discovered as a result of chemical studies directed towards the isolation of the active substances from plants used in traditional medicine. Several plant species from the family Rubiaceae are widely used in African Folk medicines. Among them, Pentas species display a broad ranges of uses. However, the phytochemistry of these species is only scarcely investigated. From the about 40 known species, only Pentas longiflora Oliver and Pentas zanzibarica (Klotsch) Vatke have been studied. Aiming at the search for novel naturally occurring compounds which may be used as "lead" for the synthesis of potentially active compounds, this work describes the isolation and structural elucidation of natural products from Pentas bussei K. Krause, Pentas lanceolata (Forsk.) Deflers and Pentas parvifolia Hiern (Chapters II, III, IV). In addition, all the isolated natural compounds are being subjected to a bioactivity screening for antiviral (HIV and HCV) and anticancer activity (Chapter VI). Chapter V has been devoted to the synthesis and structural assignment confirmation of two natural products isolated from P. longiflora a species already investigated

Clay (Montmorillonite K10) catalysis of the Michael addition of alpha,beta-unsaturated carbonyl compounds to indoles: The beneficial role of alcohols

The Michael addition of methylvinylketone to indole can be performed under smooth conditions by running the reaction in the presence of an acidic clay catalyst (K10 Montmorillonite) and an aliphatic alcohol such as ethanol or 2-propanol. Presence of an alcohol along with a polar solvent (nitromethane) in the reaction medium considerably improves the reaction