Steroid chemical properties

The steroid is a fused tetracyclic compound composed of three hexacarbocyclohexanes (A, B, C) and a five carbon ring (D). Carbon atom numbering order.
The number and position of double bonds in the various natural steroid molecules, the type, number and position of the substituent groups, the configuration between the substituent group and the cyclic core, and the configuration between the ring and the ring are different.

The six-carbon rings A, B, and C in natural steroid molecules have a "chair" conformation (cyclohexane structure), which is the most stable conformation (the only exception is that the A ring in the estrogen molecule is a flat aromatic ring Conformation).
The junction between the A ring and the B ring can be either cis or trans, and the C/D junction is generally trans (Figure 2); the only exceptions are cardiac glycosides and scorpions.
The orientation of the substituent groups attached to each carbon atom of the tetracyclic skeleton of the steroid is represented by α- or β-: it is represented by β (with a solid line) above the plane of the skeleton, and is represented by α (with a broken line) below. For example: the hydroxyl group on the cholesterol molecule C-3, and the two horn methyl groups and side chains of C-18 and C-19 are both β-oriented.
The parent compound of the steroid is typically a saturated hydrocarbon. According to the system nomenclature of IUP-AC-IUB, the class, number and orientation of the steroid substituent groups are systematically described based on the parent compound name plus the prefix and suffix.
In addition, since 1930, a variety of steroids and their metabolites have been isolated from organisms such as animals and plants, and these common names have been derived from their sources (such as cholesterol, testosterone, stigmasterol), structural features or biological functions, and some still Adopted. For example, the system name of cholesterol is cholest-5-ene-3β·ol; the system name of testosterone is 17β-hydroxy-androst-4-en-3·one; the system name of stigmasterol is cardamom-5,22 -Diene-3?-alcohol; the system name of the progesterone is 5? pregnane-3?20?diol.