Continued from 3S-1. General
Contents
3S-2. Fundamental carbocycles, unsaturation and alkyl substitution at C-17
2.1 Gonane
2.2 Estrane (oestrane)
2.3 Androstane
2.4 Parent hydrocarbons with side chain at C-17
The parent tetracyclic hydrocarbon without methyl groups at C-10 and C-13 and without a side chain at C-17 is named gonane; see formulae 9 and 10.
The hydrocarbon with a methyl group at C-13 but without a methyl group at C-10 and without a side chain at C-17 is named estrane (alternative spelling: oestrane), as shown in 11 and 12. (See addendum for pronunciation of estrene.)
The hydrocarbon with methyl groups at C-10 and C-13 but without a side chain at C-17 is named androstane 13 and 14.
Note For the names of hydrocarbons having a methyl group attached to C-10 and a hydrogen atom attached to C-13, or compounds where an ethyl group replaces a methyl group, see 3S-6. Ring expansion or contraction is covered by 3S-7.
3S-2.4. Parent hydrocarbons with side chain at C-17
The names used for the hydrocarbons 15 and 16 with methyl groups at both C-10 and C-13 and a side chain R are listed in Table 1. (See addendum for pronunciation of pregnene.)
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Table 1. Hydrocarbons with side chain at C-17
| Side chain | Configuration | 5![[alpha]](../greek/ALPHA.GIF) -Series (15) | 5![[beta]](../greek/BETA.GIF) -Series (16) |
|---|---|---|---|
 | - | 5-pregnane (not allopregnane) | 5-pregnane |
 | 20R | 5-cholane (not allocholane) | 5-cholane |
 | 20R | 5-cholestane | 5-cholestane (not coprostane) |
 | 20R,24S | 5-ergostane | 5-ergostane |
 | 20R,24R | 5-campestane | 5-campestane |
 | 20R,24S | 5-poriferastane | 5-poriferastane |
 | 20R,24R | 5-stigmastane | 5-stigmastane |
 | 20S,22R,23R,24R | 5-gorgostane | 5-gorgostane |
Notes
(1) The names of the hydrocarbons given in Table 1 imply the configuration at the chiral centres in the side chain as given in the second column. The conventions of the sequence rule, however, mean that R may change to S without a change at the relevant atom when there is a change in the substitution or unsaturation, e.g. compare 6 and 7.
(2) Some tetracyclic triterpenoids may be regarded as trimethyl steroids, the three additional methyl groups being numbered 28 (attached to C-4 with -configuration), 29 (attached to C-4 with -configuration) and 30 (attached to C-14); this numbering corresponds to that used for the triterpenoids. This type of nomenclature is especially useful for the parent hydrocarbons of biogenetic precursors of steroids. For example, lanostane 17 is 4,4,14-trimethyl-5-cholestane, the former name implying the 5,8,9,10,13,14,17,20R configuration. The change of configuration at C-9 in cycloartane 18 is implied in the name, although it must be specified if called 4,4,14-trimethyl-9,19-cyclo-5,9-cholestane. (See also addendum)
(3) For the names of hydrocarbons that are related to those given in Table 1 by the addition or removal of one or more carbon atoms, see 3S-6. For ring expansion or contraction see 3S-7.
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