The numbering of additional carbon atoms on a steriod sidechain was changed in the IUPAC-IUB Nomenclature of Steroid (Recommendations 1989). The older numbering is still used by Chemical Abstracts Service. The differences in the two numbering systems are shown in the following general formulae. As a consequence the numbering of campestane, ergostane, gorgostane, poriferastane and stigmastane was changed accordingly.
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| IUPAC-IUBMB numbering | CAS numbering |
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| Androstane | Bufanolide |
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| Campestane IUPAC numbering | Campestane CAS numbering |
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Cardanolide  | Cholane |
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| Ergostane IUPAC numbering | Ergostane CAS numbering |
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| Estrane | Furostan |
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| Gorgostane IUPAC numbering | Gorgostane CAS numbering |
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| Poriferastane IUPAC numbering | Poriferastane CAS numbering |
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| Pregnane | Spirostan |
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| Stigmastane IUPAC numbering | Stigmastane CAS numbering |