Structure of 24-ethyl-lanostane, a prototypical steroid with 32 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown withIUPAC-approved ring lettering and atom numbering.[1]: 1785f
The steroid nucleus (core structure) is calledgonane (cyclopentanoperhydrophenanthrene).[9] It is typically composed of seventeencarbon atoms, bonded in four fused rings: three six-membercyclohexane rings (rings A, B and C in the first illustration) and one five-membercyclopentane ring (the D ring). Steroids vary by thefunctional groups attached to this four-ring core and by theoxidation state of the rings.Sterols are forms of steroids with ahydroxy group at position three and a skeleton derived fromcholestane.[1]: 1785f [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 producessecosteroids one of which isvitamin D3.
Space-filling representation
Ball-and-stick representation
5α-dihydroprogesterone (5α-DHP), a steroid. The shape of the four rings of most steroids is illustrated (carbon atoms in black, oxygens in red and hydrogens in grey). Thenonpolar "slab" ofhydrocarbon in the middle (grey, black) and thepolar groups at opposing ends (red) are common features of natural steroids.5α-DHP is an endogenoussteroid hormone and abiosynthetic intermediate.
Gonane, perhydrocyclopenta[a]phenanthrene, the main structure of steroids, often referred to as the steroid nucleus.Steroid 5α and 5βstereoisomers[1]: 1786f
Gonane, also known as steran or cyclopentanoperhydrophenanthrene, the nucleus of all steroids and sterols,[11][12] is composed of seventeencarbon atoms in carbon-carbon bonds forming fourfused rings in athree-dimensional shape. The threecyclohexane rings (A, B, and C in the first illustration) form the skeleton of aperhydro derivative ofphenanthrene. The D ring has acyclopentane structure. When the two methyl groups and eight carbonside 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.[13]
Progesterone, a steroid hormone involved in the female menstrual cycle, pregnancy, and embryogenesis
Medrogestone, a synthetic drug with effects similar to progesterone
β-Sitosterol, a plant orphytosterol, with a fully branched hydrocarbon side chain at C-17 and an hydroxyl group at C-3
In addition to the ring scissions (cleavages),expansions andcontractions (cleavage and reclosing to a larger or smaller rings)—all variations in the carbon-carbon bond framework—steroids can also vary:
in the number of methyl groups attached to the ring (and, when present, on the prominent side chain at C17),
in the functional groups attached to the rings and side chain, and
in theconfiguration of groups attached to the rings and chain.[2]: 2–9
For instance,sterols such as cholesterol and lanosterol have ahydroxyl group attached at position C-3, whiletestosterone andprogesterone have a carbonyl (oxo substituent) at C-3. Among these compounds, onlylanosterol 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.
Almost all biologically relevant steroids can be presented as a derivative of a parentcholesterol-likehydrocarbon structure that serves as askeleton.[14][15] These parent structures have specific names, such aspregnane,androstane, etc. The derivatives carry variousfunctional groups called suffixes or prefixes after the respective numbers, indicating their position in the steroid nucleus.[16] There are widely used trivial steroid names of natural origin with significant biologic activity, such asprogesterone,testosterone orcortisol. Some of these names are defined in The Nomenclature of Steroids.[17] 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 steroid17α-hydroxyprogesterone has ahydroxy group (-OH) at position 17 of the steroid nucleus comparing to progesterone.
The letters α and β[18] denote absolutestereochemistry atchiral centers—a specific nomenclature distinct from theR/S convention[19] of organic chemistry to denote absolute configuration of functional groups, known asCahn–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.[20] 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.[14]
The name "11-deoxycortisol" is an example of a derived name that uses cortisol as a parent structure without anoxygenatom (hence "deoxy") attached to position 11 (as a part of a hydroxy group).[14][21] The numbering of positions ofcarbon atoms in the steroid nucleus is set in a template found in the Nomenclature of Steroids[22] that is used regardless of whether an atom is present in the steroid in question.[14]
Unsaturated carbons (generally, ones that are part of a double bond) in the steroid nucleus are indicated by changing -ane to -ene.[23] 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) or4-androstene-3,11,17-trione (also Δ4-androstene-3,11,17-trione). However, the Nomenclature of Steroids recommends thelocant 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 orandrost-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,[24] i.e., a saturation of carbons 4 and 5 of testosterone with twohydrogen 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 or5β-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.[25][23]
The suffix -ol denotes ahydroxy 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"[26] [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 thevowel (the presence or absence of a number does not affect such elision).[14][16] 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.[27]
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[28] since the 1950s.[29] Some studies use the term "11-oxyandrogens"[30][31] as an abbreviation for 11-oxygenated androgens, to emphasize that they all have an oxygen atom attached to carbon at position 11.[32][33] However, in chemical nomenclature, the prefix "oxy" is associated with ether functional groups, i.e., acompound with an oxygen atom connected to twoalkyl oraryl groups (R-O-R),[34] 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,[35] and it is appropriate to use this convention.[14]
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.[36][14]
Steroids are present across all domains of life, includingbacteria,archaea, andeukaryotes. In eukaryotes, steroids are particularly abundant in fungi, plants, and animals.[37][38]
Eukaryotic cells, encompassing animals, plants, fungi, and protists, are characterized by their complex cellular structures, including a true nucleus and membrane-bound organelles.[39] Sterols, a subgroup of steroids, play crucial roles in maintaining membrane fluidity, supporting cell signaling, and enhancing stress tolerance. These compounds are integral to eukaryotic membranes, where they contribute to membrane integrity and functionality.[40]
Duringeukaryogenesis—the evolutionary process that gave rise to modern eukaryotic cells—steroids likely facilitated the endosymbiotic acquisition of mitochondria.[41]
Prokaryotic sterol synthesis involves the tetracyclic steroid framework, as found inmyxobacteria,[43] as well ashopanoids, pentacyclic lipids that regulate bacterial membrane functions.[44] These sterol biosynthetic pathways may have originated in bacteria or been transferred fromeukaryotes.[45]
Sterol synthesis depends on two key enzymes:squalene monooxygenase andoxidosqualene cyclase. Phylogenetic analyses of oxidosqualene cyclase (Osc) suggest that some bacterial Osc genes may have been acquired viahorizontal gene transfer from eukaryotes, as certain bacterial Osc proteins closely resemble their eukaryotic homologs.[42]
Fungal steroids include theergosterols, which are involved in maintaining the integrity of the fungal cellular membrane. Variousantifungal drugs, such asamphotericin B andazole antifungals, utilize this information to killpathogenic fungi.[46] Fungi can alter their ergosterol content (e.g. through loss of function mutations in the enzymesERG3 orERG6, inducing depletion of ergosterol, or mutations that decrease the ergosterol content) to develop resistance to drugs that target ergosterol.[47]
Ergosterol is analogous to thecholesterol found in the cellular membranes of animals (including humans), or thephytosterols found in the cellular membranes of plants.[47] All mushrooms contain large quantities of ergosterol, in the range of tens to hundreds of milligrams per 100 grams of dry weight.[47] Oxygen is necessary for the synthesis ofergosterol in fungi.[47]
Ergosterol is responsible for thevitamin D content found in mushrooms; ergosterol is chemically converted into provitamin D2 by exposure toultraviolet light.[47] Provitamin D2 spontaneously forms vitamin D2.[47] However, not all fungi utilize ergosterol in their cellular membranes; for example, the pathogenic fungal speciesPneumocystis jirovecii does not, which has important clinical implications (given the mechanism of action of many antifungal drugs). Using the fungusSaccharomyces cerevisiae as an example, other major steroids includeergosta‐5,7,22,24(28)‐tetraen‐3β‐ol,zymosterol, andlanosterol.S. cerevisiae utilizes5,6‐dihydroergosterol in place of ergosterol in its cell membrane.[47]
Animal steroids include compounds ofvertebrate andinsect origin, the latter includingecdysteroids such asecdysterone (controlling molting in some species). Vertebrate examples include thesteroid hormones and cholesterol; the latter is a structural component ofcell membranes that helps determine the fluidity ofcell membranes and is a principal constituent ofplaque (implicated inatherosclerosis). Steroid hormones include:
Anabolic steroids,natural and synthetic, which interact with androgen receptors to increase muscle and bone synthesis. In popular use, the term "steroids" often refers to anabolic steroids.
Steroids can be classified based on their chemical composition.[53] One example of howMeSH performs this classification is available at the Wikipedia MeSH catalog. Examples of this classification include:
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).[54] The classification "17-ketosteroid" is also important in medicine.
The gonane (steroid nucleus) is the parent 17-carbon tetracyclic hydrocarbon molecule with noalkyl sidechains.[55]
Secosteroids (Latinseco, "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 secosteroidcholecalciferol,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.[56]
Norsteroids (nor-, L.norma; "normal" in chemistry, indicating carbon removal)[57] and homosteroids (homo-, Greekhomos; "same", indicating carbon addition) are structural subclasses of steroids formed from biosynthetic steps. The former involves enzymicring expansion-contraction reactions, and the latter is accomplished (biomimetically) or (more frequently) throughring closures ofacyclic precursors with more (or fewer) ring atoms than the parent steroid framework.[58]
Combinations of these ring alterations are known in nature. For instance,ewes who graze oncorn lily ingestcyclopamine (shown) andveratramine, two of a sub-family of steroids where the C- and D-rings are contracted and expanded respectively via abiosynthetic migration of the original C-13 atom. Ingestion of these C-nor-D-homosteroids results in birth defects in lambs:cyclopia fromcyclopamine and leg deformity from veratramine.[59] A further C-nor-D-homosteroid (nakiterpiosin) is excreted byOkinawancyanobacteriosponges. e.g.,Terpios hoshinota, leading to coral mortality from black coral disease.[60] Nakiterpiosin-type steroids are active against the signaling pathway involving thesmoothened andhedgehog proteins, a pathway which is hyperactive in a number of cancers.[citation needed]
Steroids and their metabolites often function assignalling molecules (the most notable examples are steroid hormones), and steroids andphospholipids are components ofcell membranes.[61] Steroids such as cholesterol decreasemembrane fluidity.[62]Similar tolipids, 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 likeprostate cancer, where steroid production inside and outside the tumour promotes cancer cell aggressiveness.[63]
The hundreds of steroids found in animals, fungi, andplants are made fromlanosterol (in animals and fungi; see examples above) orcycloartenol (in other eukaryotes). Both lanosterol and cycloartenol derive fromcyclization of thetriterpenoidsqualene.[4] Lanosterol and cycloartenol are sometimes called protosterols because they serve as the starting compounds for all other steroids.
Steroid biosynthesis is ananabolic pathway which produces steroids from simple precursors. A unique biosynthetic pathway is followed in animals (compared to many otherorganisms), making the pathway a common target forantibiotics and other anti-infection drugs. Steroid metabolism in humans is also the target of cholesterol-lowering drugs, such asstatins. In humans and other animals the biosynthesis of steroids follows the mevalonate pathway, which usesacetyl-CoA as building blocks fordimethylallyl diphosphate (DMAPP) andisopentenyl diphosphate (IPP).[64][better source needed]
In subsequent steps DMAPP and IPP conjugate to formfarnesyl diphosphate (FPP), which further conjugates with each other to form the linear triterpenoid squalene. Squalene biosynthesis is catalyzed bysqualene synthase, which belongs to thesqualene/phytoene synthase family. Subsequentepoxidation and cyclization of squalene generate lanosterol, which is the starting point for additional modifications into other steroids (steroidogenesis).[65] In other eukaryotes, the cyclization product of epoxidized squalene (oxidosqualene) is cycloartenol.
DMAPP and IPP donateisoprene units, which are assembled and modified to formterpenes andisoprenoids[66] (a large class of lipids, which include thecarotenoids and form the largest class of plantnatural products).[67] Here, the activated isoprene units are joined to makesqualene and folded into a set of rings to makelanosterol.[68] Lanosterol can then be converted into other steroids, such as cholesterol andergosterol.[68][69]
Human steroidogenesis, with the major classes of steroid hormones, individual steroids andenzymatic pathways.[72] Changes in molecular structure from a precursor are highlighted in white.
Steroidogenesis is the biological process by which steroids are generated from cholesterol and changed into other steroids.[73] Thepathways of steroidogenesis differ among species. The major classes of steroid hormones, as noted above (with their prominent members and functions), are theprogestogens,corticosteroids (corticoids),androgens, andestrogens.[25][74] Human steroidogenesis of these classes occurs in a number of locations:
Progestogens are the precursors of all other human steroids, and all human tissues which produce steroids must first convert cholesterol topregnenolone. This conversion is the rate-limiting step of steroid synthesis, which occurs inside themitochondrion of the respective tissue. It is catalyzed by the mitochondrial P450scc system.[75][76]
Estradiol is converted from testosterone directly (in males), or via the primary pathway DHEA – androstenedione – estrone and secondarily via testosterone (in females).[25]
Notes: "Theconcentration of a steroid in the circulation is determined by the rate at which it is secreted from glands, the rate of metabolism of precursor or prehormones into the steroid, and the rate at which it is extracted by tissues and metabolized. Thesecretion rate of a steroid refers to the total secretion of the compound from a gland per unit time. Secretion rates have been assessed by sampling the venous effluent from a gland over time and subtracting out the arterial and peripheral venous hormone concentration. Themetabolic clearance rate of a steroid is defined as the volume of blood that has been completely cleared of the hormone per unit time. Theproduction rate of a steroid hormone refers to entry into the blood of the compound from all possible sources, including secretion from glands and conversion of prohormones into the steroid of interest. At steady state, the amount of hormone entering the blood from all sources will be equal to the rate at which it is being cleared (metabolic clearance rate) multiplied by blood concentration (production rate = metabolic clearance rate × concentration). If there is little contribution of prohormone metabolism to the circulating pool of steroid, then the production rate will approximate the secretion rate."Sources: See template.
Steroids are primarily oxidized bycytochrome P450 oxidase enzymes, such asCYP3A4. These reactions introduce oxygen into the steroid ring, allowing the cholesterol to be broken up by other enzymes into bile acids.[82] These acids can then be eliminated by secretion from theliver inbile.[83] The expression of theoxidase gene can beupregulated by the steroid sensorPXR when there is a high blood concentration of steroids.[84] Steroid hormones, lacking the side chain of cholesterol and bile acids, are typicallyhydroxylated at various ring positions oroxidized at the 17 position,conjugated with sulfate orglucuronic acid and excreted in the urine.[85]
Isolation, structure determination, and methods of analysis
Steroidisolation, depending on context, is the isolation of chemical matter required forchemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more[86] 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.[87][page needed]
The methods of isolation to achieve the two scales of product are distinct, but includeextraction, precipitation,adsorption,chromatography, andcrystallization. In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such asLC-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 includedNMR and small-moleculecrystallography.[2]: 10–19 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.[87]
1969 (Chemistry)Derek Barton andOdd Hassel — Development of the concept of conformation in chemistry, emphasizing the steroid nucleus[99]
1975 (Chemistry)Vladimir Prelog — In part, for developing methods to determine the stereochemical course of cholesterol biosynthesis frommevalonic acid viasqualene[100]
^Rhen T, Cidlowski JA (October 2005). "Antiinflammatory action of glucocorticoids--new mechanisms for old drugs".The New England Journal of Medicine.353 (16):1711–1723.doi:10.1056/NEJMra050541.PMID16236742.S2CID5744727.
^ab"Lanosterol biosynthesis".Recommendations on Biochemical & Organic Nomenclature, Symbols & Terminology. International Union Of Biochemistry And Molecular Biology. Archived fromthe original on 8 March 2011. Retrieved28 November 2006.
^Arago F, Gay-Lussac JL (1816).Annales de chimie et de physique (Annals of Chemistry and Physics) (in French). Chez Crochard. p. 346."Je nommeraicholesterine, de χολη, bile, et στερεος, solide, la substance cristallisée des calculs biliares humains, ... " (I will namecholesterine – from χολη (bile) and στερεος (solid) – the crystalized substance from human gallstones ... )
^Also available in print atHill RA, Makin HL, Kirk DN, Murphy GM (1991).Dictionary of Steroids. London, GBR: Chapman and Hall. pp. xxx–lix.ISBN978-0-412-27060-4. Retrieved20 June 2015.
^"IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989".Eur J Biochem.186 (3): 430. 1989.doi:10.1111/j.1432-1033.1989.tb15228.x.PMID2606099. p. 430:3S‐1.0. Definition of steroids and sterols. Steroids are compounds possessing the skeleton of cyclopenta[a]phenanthrene or a skeleton derived therefrom by one or more bond scissions or ring expansions or contractions. Methyl groups are normally present at C-10 and C-13. An alkyl side chain may also be present at C-17. Sterols are steroids carrying a hydroxyl group at C-3 and most of the skeleton of cholestane.
^ab"IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989".Eur J Biochem.186 (3):429–458. 1989.doi:10.1111/j.1432-1033.1989.tb15228.x.PMID2606099. p. 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).
^"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.doi:10.1111/j.1432-1033.1989.tb15228.x.PMID2606099. p. 431:3S‐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.
^Favre HA, Powell WH (2014). "P-91".Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry.doi:10.1039/9781849733069.ISBN978-0-85404-182-4. p. 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;
^Favre HA, Powell WH (2014). "P-13.8.1.1".Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry.doi:10.1039/9781849733069.ISBN978-0-85404-182-4. p. 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).
^"IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989".Eur J Biochem.186 (3): 430. 1989.doi:10.1111/j.1432-1033.1989.tb15228.x.PMID2606099. p. 430:3S-1.1. Numbering and ring letters. Steroids are numbered and rings are lettered as in formula 1
^ab"IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989".Eur J Biochem.186 (3):436–437. 1989.doi:10.1111/j.1432-1033.1989.tb15228.x.PMID2606099. p. 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'
^Favre HA, Powell WH (2014). "P-3".Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry.doi:10.1039/9781849733069.ISBN978-0-85404-182-4.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.
^Makin HL, Trafford DJ (1972). "The chemistry of the steroids".Clinics in Endocrinology and Metabolism.1 (2):333–360.doi:10.1016/S0300-595X(72)80024-0.
^Bongiovanni AM, Clayton GW (March 1954). "Simplified method for estimation of 11-oxygenated neutral 17-ketosteroids in urine of individuals with adrenocortical hyperplasia".Proceedings of the Society for Experimental Biology and Medicine.85 (3):428–429.doi:10.3181/00379727-85-20905.PMID13167092.S2CID8408420.
^Slaunwhite Jr WR, Neely L, Sandberg AA (1964). "The metabolism of 11-Oxyandrogens in human subjects".Steroids.3 (4):391–416.doi:10.1016/0039-128X(64)90003-0.
^Barnard L, du Toit T, Swart AC (April 2021). "Back where it belongs: 11β-hydroxyandrostenedione compels the re-assessment of C11-oxy androgens in steroidogenesis".Molecular and Cellular Endocrinology.525: 111189.doi:10.1016/j.mce.2021.111189.PMID33539964.S2CID231776716.
^Favre H, Powell W (2014). "Appendix 2".Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013. The Royal Society of Chemistry.doi:10.1039/9781849733069.ISBN978-0-85404-182-4. p. 1112:oxy* –O– P-15.3.1.2.1.1; P-63.2.2.1.1
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