Steroidal molecule

Steroids are synthetic products of cholesterol [57-88-5]. The chemical stmcture of a steroid hormone is determined by sequential enzymatic processing of the cholesterol molecule. Steroid products differ among steroid-secreting glands because of differences in enzyme processing, eg, the production of estrogen by the ovary requires enzymatic steps that do not occur in the adrenal cortex. 

On reversed phase layers, in contrast, detergents yield dark blue zones on a pale background. Here it is the lipophilic part of the detergent molecule that is aligned with the surface RP chain and the dye is attracted to the anionic part of the molecule. Steroid derivatives can also be detected with aqueous solutions of dyes [91]. 

Molecular mechanics calculations have been carried out on a wide range of chemical compounds including hydrocarbons, heteroatomic molecules, steroids, carbohydrates and proteins. Furthermore, a variety of information has been obtained such as heats of formation, rotational barriers, and rates of reaction (18,2,19). The major advantage of this method over other computational methods is that it is reasonably fast to perform in comparison to formal molecular orbital calculations. 

Serious doubt as to the correctness of the Windaus structure came as a result of an x-ray study of ergosterol by J. D. Bernal in 1932. He pointed out that the x-ray evidence indicated ergosterol to be a long, rather flat molecule. Steroids... 

All the lipid molecules are originally synthesized from the iso-prene units in isopentenyl pyrophosphate molecules. Steroid and terpene molecules are assembled by head-to-tail condensation of these groups. 

Because of their utmost importance as bioactive molecules, steroids have been the most thoroughly studied family as far as microbiological hydroxylations are concerned. 

Permeation of large lipophilic molecules—steroid transport... 

Saponins that have in the molecule steroids as aglycones (steroid saponins) contain aglycones based on C27 structures of spirostanol or furostanol formed by modifications of the cholesterol side chain. 

Steroid and thyroid hormones must enter their target cells to exert their effect which is manifested as a change in the pattern of protein synthesis. Steroid hormone activity (Figure 10.10b) is limited to responsive eukaryotic cells in which cytosolic protein receptor molecules are located. Thyroid hormones bind to nuclear protein receptor molecules. Steroids may enter a non-target cell by diffusion but, in the absence of appropriate receptors, depart from the cell. In target tissues, the hormone is bound to specific receptor molecules to form a steroid-receptor complex which is activated by its... 

Within the lipid family, there are specific structures that distinguish the different types of lipids. Lipids such as waxes, fats, oils, and phospholipids are esters that can be hydrolyzed to give fatty acids along with other molecules. Steroids are characterized by the steroid nucleus of four fused carbon rings. They do not contain fatty acids and cannot be hydrolyzed. Figure 15.1 illustrates the types and general structure of Upids we will discuss in this chapter. 

Farnesol pyrophosphate is an immediate precursor of squalene, the key intermediate in steroid and triterpenoid biogenesis, which arises from the coupling of two farnesol pyrophosphate molecules or of C,s units derived therefrom. The numerous types of sesquiter-penoid carbon skeletons represent various modes of cyclization of farnesol (sometimes with rearrangement) and it is probable that farnesol pyrophosphate is also the source of these compounds. 

This sequence can be canied out in one or two steps and makes an important molecule for steroid syntheses. Further details are given in Fleming pages 59, 75 and 171 if you are interested. 

Further development How would you make TM 413 using the alkyl bromide you have just made This molecule is obviously on the way to a steroid and you can read more about it in Helv. Chim. Acta.. 1947, 3 1422 and J. Amer. Chem. Soc.. 1942, 974. 

Strategy Problem 6 A labelled compound for biosynthetic studies. Mevaloitic acid (TM 418) is an intermediate in the biosynthesis of terpenes and steroids (Tedder, volume 4, p.217 ff). To study exactly what happens to each carbon atom during its transformation into, say, hmonene (418A), we need separate samples of mevalonic acid labelled with in each carbon atom in the molecule. This turns our normal strategy on its head since we must now look for one carbon discoimections. You can use reagents like Na CN, and... 

A major difficulty with the Diels-Alder reaction is its sensitivity to sterical hindrance. Tri- and tetrasubstituted olefins or dienes with bulky substituents at the terminal carbons react only very slowly. Therefore bicyclic compounds with polar reactions are more suitable for such target molecules, e.g. steroids. There exist, however, several exceptions, e. g. a reaction of a tetrasubstituted alkene with a 1,1-disubstituted diene to produce a cyclohexene intermediate containing three contiguous quaternary carbon atoms (S. Danishefsky, 1979). This reaction was assisted by large polarity differences between the electron rich diene and the electron deficient ene component. 

A major trend in organic synthesis, however, is the move towards complex systems. It may happen that one needs to combine a steroid and a sugar molecule, a porphyrin and a carotenoid, a penicillin and a peptide. Also the specialists in a field have developed reactions and concepts that may, with or without modifications, be applied in other fields. If one needs to protect an amino group in a steroid, it is advisable not only to search the steroid literature but also to look into publications on peptide synthesis. In the synthesis of corrin chromophores with chiral centres, special knowledge of steroid, porphyrin, and alkaloid chemistry has been very helpful (R.B. Woodward, 1967 A. Eschenmoser, 1970). 

Cholesterol was isolated m the eighteenth century but its structure is so complex that Its correct constitution was not determined until 1932 and its stereochemistry not verified until 1955 Steroids are characterized by the tetracyclic ring system shown m Figure 26 9a As shown m Figure 26 9b cholesterol contains this tetracyclic skeleton modified to include an alcohol function at C 3 a double bond at C 5 methyl groups at C 10 and C 13 and a C Hn side chain at C 17 Isoprene units may be discerned m var lous portions of the cholesterol molecule but the overall correspondence with the iso prene rule is far from perfect Indeed cholesterol has only 27 carbon atoms three too few for It to be classed as a tnterpene... 

Experimental procedures have been described in which the desired reactions have been carried out either by whole microbial cells or by enzymes (1—3). These involve carbohydrates (qv) (4,5) steroids (qv), sterols, and bile acids (6—11) nonsteroid cycHc compounds (12) ahcycHc and alkane hydroxylations (13—16) alkaloids (7,17,18) various pharmaceuticals (qv) (19—21), including antibiotics (19—24) and miscellaneous natural products (25—27). Reviews of the microbial oxidation of aUphatic and aromatic hydrocarbons (qv) (28), monoterpenes (29,30), pesticides (qv) (31,32), lignin (qv) (33,34), flavors and fragrances (35), and other organic molecules (8,12,36,37) have been pubflshed (see Enzyp applications, industrial Enzyt s in organic synthesis Elavors AND spices). 

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