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Subject - Organic Chemistry, Biochemistry

Steroids are compounds having the rigid C17 ring system of gonanes as the basic skeleton. They differ according to the number of double bonds, the type, number and position of functional groups, the number of methyl groups, the alkyl side chains, and the configuration of bonds. Usually, they are solids (from the Greek steros, solid). Because of their rigid molecular structure they show good crystallizibility which allows for the formation of defined aggregates with other molecules and for oligomeric inclusion compounds in solution.

Gonane is a perhydrogenated 1,2-cyclopentanophenanthrene. Many steroids contain two angular methyl groups (C18,C19) at C10 and C13 and a sidechain at C17. The rings are labelled A, B, C, and D. In 5α-gonane, which does not occur in nature, rings B and C as well as rings C and D are trans configured. The corresponding hydrocarbon with arbitrary stereochemistry is called sterane.

In animals, humans, plants and fungi, compounds having a steroidal skeleton are found as vitamins (provitamin D), as bile acids, as sapogenins (digitonin), as cardiac-active substances and toad poisons, as male and female sexual hormones, as adrenocortical hormones, and as steroidal alkaloids.

Fig.1
Basic skeleton of 5α-steroids

See also: cholesterol