Shape of the steroid

Norman AW, Henry HL, Bishop JE, Song XD, Bula C, and Okamura WH (2001) Different shapes of the steroid hormone lalpha,25(OH)(2)-vitaminD(3) act as agonists for two different receptors in the vitamin D endocrine system to mediate genomic and rapid responses. Steroids 66,147-58. 

L-shape of the steroid skeleton. The geometry actually found is a flattened chair for ring C and a nearly planar skeleton ... 

The stercochcmisto of the H ut CS is always indicated in the name. The stercoehetitistry of the other H atoms is not indicated unless it dilTers from Sor-eholestane. Changing the stereochemistry of any of the ring juncture or backbone carbons (.shown in Fig. 2. >l with a heavy line on 5a-choles-tane) greatly changes the shape of the. steroid, as seen in the examples of 5a,8cr-andFostane and S/3-androstane (Fig. 2. -2). 

Altering the stereochemistry at any of the ring-juncture with a heavy-dark line (see general steroid formula s Fig. 23.1) changes immensely the prevailing shape of the steroid , as may be observed in the above cited examples of S -androstane and 5a, 8a-androstane. 

Predict the stereochemistry of the product obtained by catalytic hydrogenation of cholesterol. The six-membered rings are all in the chair conformation, and the methyl groups at the bridgehead positions are axial. (Refer to Section 4.19 to determine the shape of the steroid.)... 

Although many sterols and bile acids were isolated in the nineteenth century, it was not until the twentieth century that the stmcture of the steroid nucleus was first elucidated (5). X-ray crystallographic data first suggested that the steroid nucleus was a thin, lath-shaped stmcture (6). This perhydro-l,2-cyclopentenophenanthrene ring system was eventually confirmed by the identification of the Diels hydrocarbon [549-88-2] (4) and by the total synthesis of equilenin [517-09-9] (5) (7). 

Efforts to improve IUDs have led to the use of medicated devices. Two types of agents are generally used—contraceptive metals and steroid hormones. The metal device is exemplified by the CU-7, a polypropylene plastic device in the shape of the number 7. Copper is released by a combination of ionization and chelation from a copper wire wrapped around the vertical limb. This system is effective for up to 40 months. 

Treatment of the 11 P-hydroxysteroid with tosyl chloride produces a tosylate ester, providing a good leaving group for a base-catalysed E2 elimination (see Section 6.4.1). The favoured product is the more-substituted 9, 11-alkene (see Section 6.4.1). A consideration of the steroid shape (see Box 3.19) shows that the 9a-proton and the 1 Ip-tosylate are both axial and, therefore, anti to each other they are thus ideally positioned for an elimination... 

Upon entering the cell, the steroid molecule initially binds to the steroid receptor protein (E domain) to form the steroid-hormone-receptor complex. This complex concomitantly binds to an additional eight or more other peptides (also via the E domain) these peptides are termed chaperone peptides and consist of macromolecules such as heat shock proteins (e.g., hsp70, hsp90). The chaperone peptides help to twist and turn the steroid receptor protein into an improved three-dimensional shape for final and optimal binding of the steroid molecule. Following binding of the chaperone peptides, the steroid-hormone-receptor complex becomes a mature steroid-hormone-receptor... 

However, some ketones, such as 1-keto and 11-keto steroids have some molecular components lying in front of the carbonyl carbon (even in front of its oxygen), or in front octant regions. Clarification of the boundary between front octants and back octants was the subject of intensive theoretical and experimental studies, [6-11] which led to a clarification on the shape of the third nodal surface as convex (B, Figure 7). For most applications of the Octant Rule it is sufficient to consider only the back octants, and the special circumstances which require consideration of front octants will be obvious from the structure of the ketone. In practical applications of the Octant Rule, the octant diagrams are used to... 

Stiver and Yates have studied the photochemical reactions of some hydroxy-keto steroids (28, 29). Irradiation of the isomeric compounds (28a, 29a) showed that the products obtained, (30) and (31) respectively, had retained the configuration of the carbon to which the hydroxy group is attached. The use of deuteriated derivatives (28b, 29b) has identified the hydrogen abstraction processes involved in the conversion of these ketones into the lactones (30b) and (31b) respectively. The authors " propose that there are two major factors which control the stereospecificity of the reactions. These are the shape of the hydroxy-bearing C-atom and the hydrogen transfer within the biradical formed on Norrish Type I fission. The stability of the biradical intermediate clearly plays an important part in determining the outcome of the reactions. 

If the orientation of the principal optical directions can be found with respect to the unit cell vectors of the crystal, the orientations of the molecules in the unit cell, especially those with very anisotropic shapes and considerable unsaturation, may be found. This information was useful in the determination of the shape and size of the steroid nucleus (see Figure 1.11, Chapter 1). The relationship of molecular shape to refractive index is listed in Table 5.2, and the different refractive indices of naphthalene are shown in Figure 5.11. 

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