Steroid Explained

A steroid is an organic compound with four fused rings (designated A, B, C, and D) arranged in a specific molecular configuration. Steroids have two principal biological functions: as important components of cell membranes that alter membrane fluidity; and as signaling molecules. Examples include the lipid cholesterol, sex hormones estradiol and testosterone,[1] anabolic steroids, and the anti-inflammatory corticosteroid drug dexamethasone.[2] Hundreds of steroids are found in fungi, plants, and animals. All steroids are manufactured in cells from the sterols lanosterol (opisthokonts) or cycloartenol (plants). Lanosterol and cycloartenol are derived from the cyclization of the triterpene squalene.[3]

Steroids are named after the steroid cholesterol[4] which was first described in gall stones from Ancient Greek chole- 'bile' and stereos 'solid'.[5] [6] [7]

The steroid nucleus (core structure) is called gonane (cyclopentanoperhydrophenanthrene).[8] It is typically composed of seventeen carbon atoms, bonded in four fused rings: three six-member cyclohexane rings (rings A, B and C in the first illustration) and one five-member cyclopentane ring (the D ring). Steroids vary by the functional groups attached to this four-ring core and by the oxidation state of the rings. Sterols are forms of steroids with a hydroxy group at position three and a skeleton derived from cholestane.[9] [10] Steroids can also be more radically modified, such as by changes to the ring structure, for example, cutting one of the rings. Cutting Ring B produces secosteroids one of which is vitamin D3.

Nomenclature

Rings and functional groups

See also: Gonane and Sterane. Gonane, also known as steran or cyclopentanoperhydrophenanthrene, the simplest steroid and the nucleus of all steroids and sterols,[11] [12] is composed of seventeen carbon atoms in carbon-carbon bonds forming four fused rings in a three-dimensional shape. The three cyclohexane rings (A, B, and C in the first illustration) form the skeleton of a perhydro derivative of phenanthrene. The D ring has a cyclopentane structure. When the two methyl groups and eight carbon side chains (at C-17, as shown for cholesterol) are present, the steroid is said to have a cholestane framework. The two common 5α and 5β stereoisomeric forms of steroids exist because of differences in the side of the largely planar ring system where the hydrogen (H) atom at carbon-5 is attached, which results in a change in steroid A-ring conformation. Isomerisation at the C-21 side chain produces a parallel series of compounds, referred to as isosteroids.

Examples of steroid structures are:

In addition to the ring scissions (cleavages), expansions and contractions (cleavage and reclosing to a larger or smaller rings)—all variations in the carbon-carbon bond framework—steroids can also vary:

For instance, sterols such as cholesterol and lanosterol have a hydroxyl group attached at position C-3, while testosterone and progesterone have a carbonyl (oxo substituent) at C-3. Among these compounds, only lanosterol has two methyl groups at C-4. Cholesterol which has a C-5 to C-6 double bond, differs from testosterone and progesterone which have a C-4 to C-5 double bond.

Naming convention

Almost all biologically relevant steroids can be presented as a derivative of a parent cholesterol-like hydrocarbon structure that serves as a skeleton.[13] [14] These parent structures have specific names, such as pregnane, androstane, etc. The derivatives carry various functional groups called suffixes or prefixes after the respective numbers, indicating their position in the steroid nucleus. There are widely used trivial steroid names of natural origin with significant biologic activity, such as progesterone, testosterone or cortisol. Some of these names are defined in The Nomenclature of Steroids.[15] These trivial names can also be used as a base to derive new names, however, by adding prefixes only rather than suffixes, e.g., the steroid 17α-hydroxyprogesterone has a hydroxy group (-OH) at position 17 of the steroid nucleus comparing to progesterone.

The letters α and β[16] denote absolute stereochemistry at chiral centers—a specific nomenclature distinct from the R/S convention[17] of organic chemistry to denote absolute configuration of functional groups, known as Cahn–Ingold–Prelog priority rules. The R/S convention assigns priorities to substituents on a chiral center based on their atomic number. The highest priority group is assigned to the atom with the highest atomic number, and the lowest priority group is assigned to the atom with the lowest atomic number. The molecule is then oriented so that the lowest priority group points away from the viewer, and the remaining three groups are arranged in order of decreasing priority around the chiral center. If this arrangement is clockwise, it is assigned an R configuration; if it is counterclockwise, it is assigned an S configuration.[18] In contrast, steroid nomenclature uses α and β to denote stereochemistry at chiral centers. The α and β designations are based on the orientation of substituents relative to each other in a specific ring system. In general, α refers to a substituent that is oriented towards the plane of the ring system, while β refers to a substituent that is oriented away from the plane of the ring system. In steroids drawn from the standard perspective used in this paper, α-bonds are depicted on figures as dashed wedges and β-bonds as solid wedges.[13]

The name "11-deoxycortisol" is an example of a derived name that uses cortisol as a parent structure without an oxygen atom (hence "deoxy") attached to position 11 (as a part of a hydroxy group).[13] [19] The numbering of positions of carbon atoms in the steroid nucleus is set in a template found in the Nomenclature of Steroids[20] that is used regardless of whether an atom is present in the steroid in question.[13]

Unsaturated carbons (generally, ones that are part of a double bond) in the steroid nucleus are indicated by changing -ane to -ene.[21] This change was traditionally done in the parent name, adding a prefix to denote the position, with or without Δ (Greek capital delta) which designates unsaturation, for example, 4-pregnene-11β,17α-diol-3,20-dione (also Δ4-pregnene-11β,17α-diol-3,20-dione) or 4-androstene-3,11,17-trione (also Δ4-androstene-3,11,17-trione). However, the Nomenclature of Steroids recommends the locant of a double bond to be always adjacent to the syllable designating the unsaturation, therefore, having it as a suffix rather than a prefix, and without the use of the Δ character, i.e. pregn-4-ene-11β,17α-diol-3,20-dione or androst-4-ene-3,11,17-trione. The double bond is designated by the lower-numbered carbon atom, i.e. "Δ4-" or "4-ene" means the double bond between positions 4 and 5. The saturation of carbons of a parent steroid can be done by adding "dihydro-" prefix,[22] i.e., a saturation of carbons 4 and 5 of testosterone with two hydrogen atoms is 4,5α-dihydrotestosterone or 4,5β-dihydrotestosterone. Generally, when there is no ambiguity, one number of a hydrogen position from a steroid with a saturated bond may be omitted, leaving only the position of the second hydrogen atom, e.g., 5α-dihydrotestosterone or 5β-dihydrotestosterone. The Δ5-steroids are those with a double bond between carbons 5 and 6 and the Δ4 steroids are those with a double bond between carbons 4 and 5.[23] [21]

The abbreviations like "P4" for progesterone and "A4" for androstenedione for refer to Δ4-steroids, while "P5" for pregnenolone and "A5" for androstenediol refer to Δ5-steroids.[13]

The suffix -ol denotes a hydroxy group, while the suffix -one denotes an oxo group. When two or three identical groups are attached to the base structure at different positions, the suffix is indicated as -diol or -triol for hydroxy, and -dione or -trione for oxo groups, respectively. For example, 5α-pregnane-3α,17α-diol-20-one has a hydrogen atom at the 5α position (hence the "5α-" prefix), two hydroxy groups (-OH) at the 3α and 17α positions (hence "3α,17α-diol" suffix) and an oxo group (=O) at the position 20 (hence the "20-one" suffix). However, erroneous use of suffixes can be found, e.g., "5α-pregnan-17α-diol-3,11,20-trione"[24] [''sic''] — since it has just one hydroxy group (at 17α) rather than two, then the suffix should be -ol, rather than -diol, so that the correct name to be "5α-pregnan-17α-ol-3,11,20-trione".

According to the rule set in the Nomenclature of Steroids, the terminal "e" in the parent structure name should be elided before the vowel (the presence or absence of a number does not affect such elision).[13] [25] This means, for instance, that if the suffix immediately appended to the parent structure name begins with a vowel, the trailing "e" is removed from that name. An example of such removal is "5α-pregnan-17α-ol-3,20-dione", where the last "e" of "pregnane" is dropped due to the vowel ("o") at the beginning of the suffix -ol. Some authors incorrectly use this rule, eliding the terminal "e" where it should be kept, or vice versa.[26]

The term "11-oxygenated" refers to the presence of an oxygen atom as an oxo (=O) or hydroxy (-OH) substituent at carbon 11. "Oxygenated" is consistently used within the chemistry of the steroids[27] since the 1950s.[28] Some studies use the term "11-oxyandrogens"[29] [30] as an abbreviation for 11-oxygenated androgens, to emphasize that they all have an oxygen atom attached to carbon at position 11.[31] [32] However, in chemical nomenclature, the prefix "oxy" is associated with ether functional groups, i.e., a compound with an oxygen atom connected to two alkyl or aryl groups (R-O-R),[33] therefore, using "oxy" within the name of a steroid class may be misleading. One can find clear examples of "oxygenated" to refer to a broad class of organic molecules containing a variety of oxygen containing functional groups in other domains of organic chemistry,[34] and it is appropriate to use this convention.[13]

Even though "keto" is a standard prefix in organic chemistry, the 1989 recommendations of the Joint Commission on Biochemical Nomenclature discourage the application of the prefix "keto" for steroid names, and favor the prefix "oxo" (e.g., 11-oxo steroids rather than 11-keto steroids), because "keto" includes the carbon that is part of the steroid nucleus and the same carbon atom should not be specified twice.[35] [13]

Species distribution

Steroids are found in all domains of life including bacteria, archaea, and eukaryotes. In eukaryotes, steroids are found in fungi, plants, and animals.[36] [37]

Eukaryotic and Prokaryotic

Eukaryotic cells, which include animals, plants, fungi, and protists, have complex cellular structures with a true nucleus and membrane-bound organelles.[38]

Steroids are integral to eukaryotic cellular membranes, where they help maintain membrane integrity and function.[39]

During eukaryogenesis (the emergence of modern eukaryotic cells), steroids likely played a role in the acquisition of mitochondria via endocytosis.[40]

In prokaryotes, biosynthetic pathways exist for the tetracyclic steroid framework (e.g. in myxobacteria)[41] – where its origin from eukaryotes is conjectured[42] – and the more-common pentacyclic triterpinoid hopanoid framework.[43]

Fungal

Fungal steroids include the ergosterols, which are involved in maintaining the integrity of the fungal cellular membrane. Various antifungal drugs, such as amphotericin B and azole antifungals, utilize this information to kill pathogenic fungi.[44] Fungi can alter their ergosterol content (e.g. through loss of function mutations in the enzymes ERG3 or ERG6, inducing depletion of ergosterol, or mutations that decrease the ergosterol content) to develop resistance to drugs that target ergosterol.

Ergosterol is analogous to the cholesterol found in the cellular membranes of animals (including humans), or the phytosterols found in the cellular membranes of plants.[45] All mushrooms contain large quantities of ergosterol, in the range of tens to hundreds of milligrams per 100 grams of dry weight. Oxygen is necessary for the synthesis of ergosterol in fungi.

Ergosterol is responsible for the vitamin D content found in mushrooms; ergosterol is chemically converted into provitamin D2 by exposure to ultraviolet light. Provitamin D2 spontaneously forms vitamin D2. However, not all fungi utilize ergosterol in their cellular membranes; for example, the pathogenic fungal species Pneumocystis jirovecii does not, which has important clinical implications (given the mechanism of action of many antifungal drugs). Using the fungus Saccharomyces cerevisiae as an example, other major steroids include ergosta‐5,7,22,24(28)‐tetraen‐3β‐ol, zymosterol, and lanosterol. S. cerevisiae utilizes 5,6‐dihydroergosterol in place of ergosterol in its cell membrane.

Plant

Plant steroids include steroidal alkaloids found in Solanaceae[46] and Melanthiaceae (specially the genus Veratrum),[47] cardiac glycosides,[48] the phytosterols and the brassinosteroids (which include several plant hormones).

Animal

Animal steroids include compounds of vertebrate and insect origin, the latter including ecdysteroids such as ecdysterone (controlling molting in some species). Vertebrate examples include the steroid hormones and cholesterol; the latter is a structural component of cell membranes that helps determine the fluidity of cell membranes and is a principal constituent of plaque (implicated in atherosclerosis). Steroid hormones include:

Types

By function

The major classes of steroid hormones, with prominent members and examples of related functions, are:[49] [50]

Additional classes of steroids include:

As well as the following class of secosteroids (open-ring steroids):

By structure

Intact ring system

Steroids can be classified based on their chemical composition.[51] One example of how MeSH performs this classification is available at the Wikipedia MeSH catalog. Examples of this classification include:

ClassExampleNumber of carbon atoms
CholestanesCholesterol27
CholanesCholic acid24
PregnanesProgesterone21
AndrostanesTestosterone19
EstranesEstradiol18
In biology, it is common to name the above steroid classes by the number of carbon atoms present when referring to hormones: C18-steroids for the estranes (mostly estrogens), C19-steroids for the androstanes (mostly androgens), and C21-steroids for the pregnanes (mostly corticosteroids).[52] The classification "17-ketosteroid" is also important in medicine.

The gonane (steroid nucleus) is the parent 17-carbon tetracyclic hydrocarbon molecule with no alkyl sidechains.[53]

Cleaved, contracted, and expanded rings

Secosteroids (Latin seco, "to cut") are a subclass of steroidal compounds resulting, biosynthetically or conceptually, from scission (cleavage) of parent steroid rings (generally one of the four). Major secosteroid subclasses are defined by the steroid carbon atoms where this scission has taken place. For instance, the prototypical secosteroid cholecalciferol, vitamin D3 (shown), is in the 9,10-secosteroid subclass and derives from the cleavage of carbon atoms C-9 and C-10 of the steroid B-ring; 5,6-secosteroids and 13,14-steroids are similar.[54]

Norsteroids (nor-, L. norma; "normal" in chemistry, indicating carbon removal)[55] and homosteroids (homo-, Greek homos; "same", indicating carbon addition) are structural subclasses of steroids formed from biosynthetic steps. The former involves enzymic ring expansion-contraction reactions, and the latter is accomplished (biomimetically) or (more frequently) through ring closures of acyclic precursors with more (or fewer) ring atoms than the parent steroid framework.[56]

Combinations of these ring alterations are known in nature. For instance, ewes who graze on corn lily ingest cyclopamine (shown) and veratramine, two of a sub-family of steroids where the C- and D-rings are contracted and expanded respectively via a biosynthetic migration of the original C-13 atom. Ingestion of these C-nor-D-homosteroids results in birth defects in lambs: cyclopia from cyclopamine and leg deformity from veratramine.[57] A further C-nor-D-homosteroid (nakiterpiosin) is excreted by Okinawan cyanobacteriosponges. e.g., Terpios hoshinota, leading to coral mortality from black coral disease.[58] Nakiterpiosin-type steroids are active against the signaling pathway involving the smoothened and hedgehog proteins, a pathway which is hyperactive in a number of cancers.

Biological significance

Steroids and their metabolites often function as signalling molecules (the most notable examples are steroid hormones), and steroids and phospholipids are components of cell membranes.[59] Steroids such as cholesterol decrease membrane fluidity.[60] Similar to lipids, steroids are highly concentrated energy stores. However, they are not typically sources of energy; in mammals, they are normally metabolized and excreted.

Steroids play critical roles in a number of disorders, including malignancies like prostate cancer, where steroid production inside and outside the tumour promotes cancer cell aggressiveness.[61]

Biosynthesis and metabolism

The hundreds of steroids found in animals, fungi, and plants are made from lanosterol (in animals and fungi; see examples above) or cycloartenol (in other eukaryotes). Both lanosterol and cycloartenol derive from cyclization of the triterpenoid squalene.[3] Lanosterol and cycloartenol are sometimes called protosterols because they serve as the starting compounds for all other steroids.

Steroid biosynthesis is an anabolic pathway which produces steroids from simple precursors. A unique biosynthetic pathway is followed in animals (compared to many other organisms), making the pathway a common target for antibiotics and other anti-infection drugs. Steroid metabolism in humans is also the target of cholesterol-lowering drugs, such as statins. In humans and other animals the biosynthesis of steroids follows the mevalonate pathway, which uses acetyl-CoA as building blocks for dimethylallyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP).[62]

In subsequent steps DMAPP and IPP conjugate to form farnesyl diphosphate (FPP), which further conjugates with each other to form the linear triterpenoid squalene. Squalene biosynthesis is catalyzed by squalene synthase, which belongs to the squalene/phytoene synthase family. Subsequent epoxidation and cyclization of squalene generate lanosterol, which is the starting point for additional modifications into other steroids (steroidogenesis).[63] In other eukaryotes, the cyclization product of epoxidized squalene (oxidosqualene) is cycloartenol.

Mevalonate pathway

See main article: Mevalonate pathway. The mevalonate pathway (also called HMG-CoA reductase pathway) begins with acetyl-CoA and ends with dimethylallyl diphosphate (DMAPP) and isopentenyl diphosphate (IPP).

DMAPP and IPP donate isoprene units, which are assembled and modified to form terpenes and isoprenoids[64] (a large class of lipids, which include the carotenoids and form the largest class of plant natural products).[65] Here, the isoprene units are joined to make squalene and folded into a set of rings to make lanosterol.[66] Lanosterol can then be converted into other steroids, such as cholesterol and ergosterol.[66] [67]

Two classes of drugs target the mevalonate pathway: statins (like rosuvastatin), which are used to reduce elevated cholesterol levels,[68] and bisphosphonates (like zoledronate), which are used to treat a number of bone-degenerative diseases.[69]

Steroidogenesis

See also: Steroidogenic enzyme.

Steroidogenesis is the biological process by which steroids are generated from cholesterol and changed into other steroids.[70] The pathways of steroidogenesis differ among species. The major classes of steroid hormones, as noted above (with their prominent members and functions), are the progestogens, corticosteroids (corticoids), androgens, and estrogens.[23] Human steroidogenesis of these classes occurs in a number of locations:

Alternative pathways

In plants and bacteria, the non-mevalonate pathway (MEP pathway) uses pyruvate and glyceraldehyde 3-phosphate as substrates to produce IPP and DMAPP.[64] [76]

During diseases pathways otherwise not significant in healthy humans can become utilized. For example, in one form of congenital adrenal hyperplasia a deficiency in the 21-hydroxylase enzymatic pathway leads to an excess of 17α-Hydroxyprogesterone (17-OHP) – this pathological excess of 17-OHP in turn may be converted to dihydrotestosterone (DHT, a potent androgen) through among others 17,20 Lyase (a member of the cytochrome P450 family of enzymes), 5α-Reductase and 3α-Hydroxysteroid dehydrogenase.[77]

Catabolism and excretion

Steroids are primarily oxidized by cytochrome P450 oxidase enzymes, such as CYP3A4. These reactions introduce oxygen into the steroid ring, allowing the cholesterol to be broken up by other enzymes into bile acids.[78] These acids can then be eliminated by secretion from the liver in bile.[79] The expression of the oxidase gene can be upregulated by the steroid sensor PXR when there is a high blood concentration of steroids.[80] Steroid hormones, lacking the side chain of cholesterol and bile acids, are typically hydroxylated at various ring positions or oxidized at the 17 position, conjugated with sulfate or glucuronic acid and excreted in the urine.[81]

Isolation, structure determination, and methods of analysis

Steroid isolation, depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram.[82]

The methods of isolation to achieve the two scales of product are distinct, but include extraction, precipitation, adsorption, chromatography, and crystallization. In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS, are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample.

Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography.[1] Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity.[82]

Chemical synthesis

Microbial catabolism of phytosterol side chains yields C-19 steroids, C-22 steroids, and 17-ketosteroids (i.e. precursors to adrenocortical hormones and contraceptives).[83] [84] [85] The addition and modification of functional groups is key when producing the wide variety of medications available within this chemical classification. These modifications are performed using conventional organic synthesis and/or biotransformation techniques.[86] [87]

Precursors

Semisynthesis

The semisynthesis of steroids often begins from precursors such as cholesterol, phytosterols, or sapogenins.[88] The efforts of Syntex, a company involved in the Mexican barbasco trade, used Dioscorea mexicana to produce the sapogenin diosgenin in the early days of the synthetic steroid pharmaceutical industry.[89]

Total synthesis

Some steroidal hormones are economically obtained only by total synthesis from petrochemicals (e.g. 13-alkyl steroids). For example, the pharmaceutical Norgestrel begins from methoxy-1-tetralone, a petrochemical derived from phenol.

Research awards

A number of Nobel Prizes have been awarded for steroid research, including:

See also

Bibliography

Notes and References

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  4. Web site: Harper D . sterol Etymology, origin and meaning of sterol by etymonline . 19 March 2023 . Online Etymology Dictionary . 19 March 2023 . https://web.archive.org/web/20230319092627/https://www.etymonline.com/word/sterol . live .
  5. Chevreul ME . Michel Eugène Chevreul . Recherches chimiques sur les corps gras, et particulièrement sur leurs combinaisons avec les alcalis. Sixième mémoire. Examen des graisses d'homme, de mouton, de boeuf, de jaguar et d'oie . Chemical research on fatty substances, and particularly on their combinations with alkalis. Sixth memoir. Examination of human, sheep, beef, jaguar and goose fats . 8 May 1815 . Annales de Chimie et de Physique (Annals of Chemistry and Physics) . 2 . 339–372 . Deutsche Digitale Bibliothek . 11 September 2023 . fr . 4 October 2023 . https://web.archive.org/web/20231004081946/https://www.deutsche-digitale-bibliothek.de/item/254EFGXQPJNOVNAF575XO6K7MXD7EQOZ . live .
  6. Book: Annales de chimie et de physique (Annals of Chemistry and Physics) . Arago F, Gay-Lussac JL . 1816 . Chez Crochard . fr . 346 . "Je nommerai cholesterine, de χολη, bile, et στερεος, solide, la substance cristallisée des calculs biliares humains, ... " (I will name cholesterine – from χολη (bile) and στερεος (solid) – the crystalized substance from human gallstones ...).
  7. Web site: R-2.4.1 Fusion nomenclature . 22 November 2023 . 22 November 2023 . https://web.archive.org/web/20231122015342/https://www.acdlabs.com/iupac/nomenclature/93/r93_229.htm . live .
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  15. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989, chapter 3S-4.9 . European Journal of Biochemistry . 186 . 3 . 429–458 . December 1989 . 2606099 . 10.1111/j.1432-1033.1989.tb15228.x . 3S‐4.9. Trivial names of important steroids Examples of trivial names retained for important steroid derivatives, these being mostly natural compounds of significant biological activity, are given in Table 2 . 19 February 2024 . 19 February 2024 . https://web.archive.org/web/20240219010052/https://iupac.qmul.ac.uk/steroid/3S04b.html#3S49 . live .
  16. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989, chapter 3S-1.4 . European Journal of Biochemistry . 186 . 3 . 429–458 . December 1989 . 2606099 . 10.1111/j.1432-1033.1989.tb15228.x . 3S‐1.4. Orientation of projection formulae. When the rings of a steroid are denoted as projections onto the plane of the paper, the formula is normally to be oriented as in 2a. An atom or group attached to a ring depicted as in the orientation 2a is termed α (alpha) if it lies below the plane of the paper or β (beta) if it lies above the plane of the paper. . 431 .
  17. Book: Favre HA, Powell WH . Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. 2014. 978-0-85404-182-4. 10.1039/9781849733069. P-91. 868. P‐91.2.1.1 Cahn-Ingold-Prelog (CIP) stereodescriptors. Some stereodescriptors described in the Cahn-Ingold-Prelog (CIP) priority system, called ‘CIP stereodescriptors’, are recommended to specify the configuration of organic compounds, as described and exemplified in this Chapter and applied in Chapters P‐1 through P‐8, and in the nomenclature of natural products in Chapter P-10. The following stereodescriptors are used as preferred stereodescriptors (see P‐92.1.2): (a) ‘R’ and ‘S’, to designate the absolute configuration of tetracoordinate (quadriligant) chirality centers;.
  18. Web site: 3.5: Naming chiral centers- the R and S system . 11 August 2018 . 16 October 2023 . 1 November 2023 . https://web.archive.org/web/20231101155825/https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Book:_Organic_Chemistry_with_a_Biological_Emphasis_v2.0_(Soderberg)/03:_Conformations_and_Stereochemistry/3.05:_Naming_chiral_centers-_the_R_and_S_system . live .
  19. Book: Favre HA, Powell WH . Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. 2014. 978-0-85404-182-4. 10.1039/9781849733069. P-13.8.1.1. 66. P‐13.8.1.1 The prefix ‘de’ (not ‘des’), followed by the name of a group or atom (other than hydrogen), denotes removal (or loss) of that group and addition of the necessary hydrogen atoms, i.e., exchange of that group with hydrogen atoms. As an exception, ‘deoxy’, when applied to hydroxy compounds, denotes the removal of an oxygen atom from an –OH group with the reconnection of the hydrogen atom. ‘Deoxy’ is extensively used as a subtractive prefix in carbohydrate nomenclature (see P‐102.5.3)..
  20. 1989. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989. Eur J Biochem. 186. 3. 430. 10.1111/j.1432-1033.1989.tb15228.x. 2606099. 3S-1.1. Numbering and ring letters. Steroids are numbered and rings are lettered as in formula 1. 430.
  21. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989 . Eur J Biochem . 1989 . 186 . 3 . 436–437 . 10.1111/j.1432-1033.1989.tb15228.x . 2606099 . 436-437. 3S‐2.5 Unsaturation. Unsaturation is indicated by changing -ane to -ene, -adiene, -yne etc., or -an- to -en-, -adien-, -yn- etc. Examples: Androst-5-ene, not 5-androstene; 5α-Cholest-6-ene; 5β-Cholesta-7,9(11)-diene; 5α-Cholest-6-en-3β-ol. Notes. 1) It is now recommended that the locant of a double bond is always adjacent to the syllable designating the unsaturation.[...] 3) The use of Δ (Greek capital delta) character is not recommended to designate unsaturation in individual names. It may be used, however, in generic terms, like ‘Δ5-steroids’.
  22. Book: Favre HA, Powell WH . Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. 2014. 978-0-85404-182-4. 10.1039/9781849733069. P-3. P-31.2.2 General methodology. ‘Hydro’ and ‘dehydro’ prefixes are associated with hydrogenation and dehydrogenation, respectively, of a double bond; thus, multiplying prefixes of even values, as ‘di’, ‘tetra’, etc. are used to indicate the saturation of double bond(s), for example ‘dihydro’, ‘tetrahydro’; or creation of double (or triple) bonds, as ‘didehydro’, etc. In names, they are placed immediately at the front of the name of the parent hydride and in front of any nondetachable prefixes. Indicated hydrogen atoms have priority over ‘hydro‘ prefixes for low locants. If indicated hydrogen atoms are present in a name, the ‘hydro‘ prefixes precede them..
  23. Miller WL, Auchus RJ . The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders . Endocr Rev . 32 . 1 . 81–151 . February 2011 . 21051590 . 3365799 . 10.1210/er.2010-0013.
  24. Web site: Google Scholar search results for "5α-pregnan-17α-diol-3,11,20-trione" that is an incorrect name. 2022. 1 October 2023. 6 October 2023. https://web.archive.org/web/20231006203706/https://scholar.google.com/scholar?&q=%225%CE%B1-pregnan-17%CE%B1-diol-3%2C11%2C20-trione%22. live.
  25. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989 . Eur J Biochem . 1989 . 186 . 3 . 429–458 . 10.1111/j.1432-1033.1989.tb15228.x . 2606099. 441. 3S-4. FUNCTIONAL GROUPS. 3S-4.0. General. Nearly all biologically important steroids are derivatives of the parent hydrocarbons (cf. Table 1) carrying various functional groups. [...] Suffixes are added to the name of the saturated or unsaturated parent system (see 33-2.5), the terminal e of -ane, -ene, -yne, -adiene etc. being elided before a vowel (presence or absence of numerals has no effect on such elisions)..
  26. Web site: Google Scholar search results for "5α-pregnane-17α-ol-3,20-dione" that is an incorrect name. 2022. 1 October 2023. 7 October 2023. https://web.archive.org/web/20231007002325/https://scholar.google.com/scholar?q=%225%CE%B1-pregnane-17%CE%B1-ol-3%2C20-dione%22. live.
  27. Makin HL, Trafford DJ . 1972. The chemistry of the steroids. Clinics in Endocrinology and Metabolism. 1. 2. 333–360. 10.1016/S0300-595X(72)80024-0.
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  29. Slaunwhite Jr WR, Neely L, Sandberg AA . 1964. The metabolism of 11-Oxyandrogens in human subjects. Steroids. 3. 4. 391–416. 10.1016/0039-128X(64)90003-0.
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  33. Book: Favre H, Powell W . Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry. 2014. 978-0-85404-182-4. 10.1039/9781849733069. Appendix 2. 1112. oxy* –O– P-15.3.1.2.1.1; P-63.2.2.1.1.
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  35. 1989. IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989. Eur J Biochem. 186. 3. 429–58. 10.1111/j.1432-1033.1989.tb15228.x. 2606099. The prefix oxo- should also be used in connection with generic terms, e.g., 17-oxo steroids. The term ‘17-keto steroids’, often used in the medical literature, is incorrect because C-17 is specified twice, as the term keto denotes C=O. 430.
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