Steroids Overview Quiz

Steroids

• Steroids are organic compounds characterized by four rings arranged in a specific molecular configuration, known as the cyclopentanoperhydrophenanthrene nucleus.
• The four rings consist of three six-member cyclohexane rings (A, B, and C) and one five-member cyclopentane ring (D).
• Steroids are distinguished by the functional groups attached to this core structure and the oxidation state of the rings.

Numbering of Steroids

• The steroid core structure comprises 17 carbon atoms bonded in four fused rings.
• Angular methyl groups are typically found at C-10 and C-13 positions.
• An alkyl group may be present at C-17. Sterols typically have a hydroxyl group at C-3.
• A side chain is attached at the 17th position.

Properties of Steroids

• Steroids exhibit a relatively flat and rigid molecular structure.
• They possess high crystalline properties.
• Steroids are both hydrophilic and lipophilic.
• They do not contain fatty acids.
• Cholesterol, a well-known steroid, is exclusively found in animals.

SAR of Steroids

• The aromatic ring with a C-3 hydroxyl group is essential for activity.
• The 17β-hydroxyl group, maintaining a constant distance from the 3-OH, is crucial for activity.
• Unsaturation of ring B reduces activity.
• Modifications at the 16th and 17th positions can enhance activity.

Nomenclature of Steroids

• Steroids are primarily named as derivatives of basic steroidal ring systems.
• These ring systems are categorized based on the number of carbon atoms they contain:
  • Gonane (C17):
  • Estrane (C18): Examples include estrogens (estradiol, estrone, estriol).
  • Androstane (C19): Examples include androgens (testosterone).
  • Pregnane (C21): Examples include progesterone and corticosteroids.
  • Cholane (C24): Examples include bile acids.
  • Cholestane (C27): Examples include cholesterol.

Configuration of Steroids

• β Configuration: Substituents attached to the ring system from above are designated as β, with lines represented as thickened.
• α Configuration: Substituents attached to the ring system from below are designated as α, with lines represented as broken or dotted.
• Unknown Configuration: If the configuration of the substituent is unknown, it is represented with a wavy line.

Stereochemistry of Steroids

• The stereochemistry of the rings significantly influences the biological activity of specific steroid classes.
• The steroid nucleus contains six asymmetric carbon atoms (5, 8, 9, 10, 13, 14), potentially leading to 64 optically active forms.
• Steroids can exist in two conformations: chair form and boat form.

Notable Steroids:

• Estrogens:

  • Estrone
  • Estradiol
  • Estriol
  • All derived from the Estrane ring system.
  • C18

• Androgens:

  • Testosterone
  • Derived from the Androstane ring system.
  • C19
  • Androst-4-en-17β-ol-3-one

• Progesterone:

  • Derived from the Pregnane ring system.
  • C21
  • Progest-4-en-3,20-dione

• Cortisone:

  • Derived from the Pregnane ring system.
  • C21
  • 17α,21-dihydroxypregn-4-en-3,11,20-trione

• Bile acid-cholic acid:

  • Derived from the Cholane ring system.
  • C24
  • 3,7,12-Trihydroxycholan-24-oic acid

• Cholesterol:

  • Derived from the Cholestane ring system.
  • C27
  • Choles-5-en-3β-ol