Do hydrocarbons have strain limits? 4-6 Carbocyclic Products in Nature Four are used for: 66.5 kcal mo ical struc -0rgnnc specificity (taxonomy) 19 kcal mol Unknown 166 kcal mo 61 kcal mors 品ca arbon Tree S6ewetpfy6igYfncaturlproductswmith er methyls because unction or regulators of Three common steroids are: 8 SbcCGdfateacdnvowednemudksiaton,destionane heoe5psoa9aeaehyeeag2naneaeehehnce 55 Do hydrocarbons have strain limits? Many interesting molecules have been synthesized to examine the limits of strain in hydrocarbon bonds: 66.5 kcal mol-1 61 kcal mol-1 166 kcal mol-1 Unknown 129 kcal mol-1 4-6 Carbocyclic Products in Nature Natural products are organic compounds produced by living organisms. Four classification schemes are used for natural products: •Chemical structure •Physiological activity •Organism or plant specificity (taxonomy) •Biochemical origin Terpenes and steroids have received much attention from organic chemists. Terpenes are constructed in plants from isoprene units. Terpenes are volatile compounds usually containing 10 (monoterpenes), 15 (sesquiterpenes) , or 20 (ditepenes) carbon atoms. Terpenes are synthesized in plants by linking two or more 5 carbon fragments called isoprene (2-methyl-1,3-butadiene). Examples of terpenes include: • Chrysanthemic acid Natural insecticide • Grandisol Boll weevil sex attractant • Menthol Peppermint oil • Camphor Camphor Tree • β-Cadinene Juniper and ceder trees • Taxol Pacific yew tree, Anti-tumor drug Steroids are tetracyclic natural products with powerful physiological activities. Steroids frequently function as hormones, or regulators of biological activities. Synthetic steroids are used in the treatment of cancer, arthritis, allergies, and in birth control. Steroids consist of 3 fused cyclohexane rings fused to a cyclopentane ring. The ring junctions are usually trans. The rings are labeled A,B,C,D. Methyl groups at C10 and C13 and oxygen at C3 and C17 are common. Due to the trans ring fusion, an all chair conformation is assumed with the ring junction hydrogens and methyl groups in axial positions. Groups attached above the plane of the steroid ring structure are termed β while those below are termed α. Axial methyl groups are referred to as angular methyls because they sharply protrude from the framework. Three common steroids are: Cholesterol is present in almost all human and animal tissue. It can precipitate in the arteries, causing arteriosclerosis and heart disease. It is a precursor for bile acids and steroid hormones. Cholic acid is a bile acid involved in emulsification, digestion and absorption of fats. Cortisone is involved in regulating electrolyte and water balance in the body, as well as carbohydrate and protein metabolism