Question:
Steroidal cholestane ring fused with
Steroidal cholestane ring fused with
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Remember the tetracyclic steroid nucleus involves key fusion points at carbons 5, 6, 8, 9, 10, and 13 — important for structural identification in medicinal chemistry.
Updated On: Jul 14, 2026
- 5, 6, 7, 9, 10, 13
- 5, 6, 8, 9, 10, 11
- 5, 6, 8, 9, 10, 13
- 5, 6, 8, 9, 10, 14
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The Correct Option is C
Approach Solution - 1
- Cholestane is a saturated derivative of cholesterol and serves as the parent compound for many steroids.
- It consists of a perhydrocyclopentanophenanthrene nucleus, which includes three six-membered rings (A, B, and C) and one five-membered ring (D).
- These four rings are fused together at the carbon positions 5, 6, 8, 9, 10, and 13, forming a tetracyclic skeleton.
- This numbering follows IUPAC nomenclature, and these positions are critical for defining stereochemistry and biological activity of steroid molecules.
- It consists of a perhydrocyclopentanophenanthrene nucleus, which includes three six-membered rings (A, B, and C) and one five-membered ring (D).
- These four rings are fused together at the carbon positions 5, 6, 8, 9, 10, and 13, forming a tetracyclic skeleton.
- This numbering follows IUPAC nomenclature, and these positions are critical for defining stereochemistry and biological activity of steroid molecules.
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Approach Solution -2
The question asks which set of carbon positions the four rings of the cholestane (steroid) nucleus are fused at. Let's check each numbered set against the standard steroid ring-fusion numbering.
- 5, 6, 7, 9, 10, 13: Position 7 is a ring-interior carbon in ring B, not a fusion carbon. Since one of the six numbers is wrong, this set cannot be the correct fusion pattern.
- 5, 6, 8, 9, 10, 11: Position 11 also lies within ring C rather than at a ring junction. Swapping in 11 in place of the true junction carbon 13 makes this set incorrect.
- 5, 6, 8, 9, 10, 13: Rings A and B share carbons 5 and 6, rings B and C share carbons 8 and 9, carbon 10 is the angular carbon joining rings A and B, and carbon 13 is the angular carbon joining rings C and D. All six numbers correspond exactly to the true ring-junction carbons of the perhydrocyclopentanophenanthrene skeleton.
- 5, 6, 8, 9, 10, 14: Position 14 sits inside ring C/D but is not itself a fusion carbon between C and D; that role belongs to carbon 13. This makes the set incorrect.
Only the set 5, 6, 8, 9, 10, 13 lines up exactly with the carbons where the three six-membered rings and the one five-membered ring of the cholestane nucleus meet.
Therefore, the correct answer is 5, 6, 8, 9, 10, 13.
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