Alkaloid A cyclic organic compound that contains nitrogen in a negative oxidation state and is of limited distribution among living organisms. Over 10,000 alkaloids of many different structural types are known; and no other class of natural products possesses such an enormous variety of structures. Therefore, alkaloids are difficult to differentiate from other types of
A reaction in which two or more unsaturated compounds form a cyclic adduct or in which a cyclic compound is formed by addition between unsaturated parts of the same molecule. In cycloaddition, there is no net reduction in bond multiplicity. The Diels-Alder reaction is an example. Cycloadditions may be stepwise reactions or may be peri-cyclic