3S-2.4

This version of 3S-2.4 does not use the HTML table format.

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.

Table 1. Hydrocarbons with side chain at C-17

Side chain Configuration 5-Series (15) 5-Series (16)

- 5-pregnane (not allopregnane) 5-pregnane

20R 5-cholane (not allocholane) 5-cholane

20R 5-cholestane (not coprostane) 5-cholestane

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.

(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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