Steroid Nomenclature

Question 1

Steroid Structure

Answer 1

• Characteristic fused ring structure

- Similar chemistry and nomenclature from sharing similar structure

Question 2

Steroid Backbone

Answer 2

• Phenanthrene - 3 fused benzenes
• Polycyclic aromatic hydrocarbon
• 17 carbons including cyclopentene
• Complex 3D structure, NOT flat

Question 3

Class/Roots

Answer 3

• Cholestane - 27 carbons
• Pregnane - 21 carbons (ethane on carbon 17)
• Andro - 19 carbons (nothing on carbon 17)
• Estra - 18 carbons (nothing on carbon 17 and hydrogen on carbon 19)

Question 4

Configuration

Answer 4

-Cis/trans based on groups at the fusion of rings
-C18 & C19 are always perpendicular to ring
-All solid components (including C18 and C19) are on beta plane
-All dashed lines are on alpha plane
-The chemistry of the C5 hydrogen, if present, should ALWAYS be in the steroids name since it is a shape determinant of the ring
EX: 5-alpha = trans-trans-trans
5-beta = cis-trans-trans

Question 5

Suffixes

Answer 5

• ane = fully saturated hydrocarbon
• ene = double bond on any ring
• diene/triene = two or three double bonds
• ol = hydroxyl group
• one = keto group
• aldehyde = aldosterone

Bottom 3 occur in natural steroid

Question 6

Prefixes

Answer 6

• alpha, beta, delta (unsaturated)
• dihydro - 2 hydrogen added
• tetrahydro - 4 hydrogens added
• Nor - loss of CH3 group
• Propionate - propionic acid ester