Cis Steroids

Problem 27.9 Lithocholic acid is an A-B cis steroid found in human bile. Draw lithocliolic acid showing chair conformations as in Figure 27.11, and tell whether the hydroxyl group at C3 is axial or equatorial. 

The following mode) is that of cholic acid, a constituent of human bile. Locate the three hydroxyl groups, and identify each as axial or equatorial. Is cholic acid an A-B trans steroid or an A-B cis steroid ... 

Apart from PET-reductive cyclization, chemical reduction has also been applied to the total synthesis of natural products such as capnellenediol 186 [184]. Naphthalene sodium is shown to be a suitable oxidant for generating ketyl radical anions which cyclize efficiently in a 5-exo-dig mode. In contrast, electroreductive cyclization of 184 does not lead to 185, but exclusively to the thermodynamically preferred 5-exo isomer with a remaining double bond in the endocyclic position [185] (Scheme 35). The steroid precursor 4.5-secocholes-tan-5-one 187, in which the lOa-side chain is varied, has been cyclized under the same conditions [186-188] (Scheme 36). Reduction with naphthalene sodium or sodium in ether exclusively produces the A B-cis steroid 188 with an exo double... 

Withanolides. Withanolides are Cis-steroidal lactones that are isolated from the Solanaceae plant family. Withanolides are characterized by an ergostane-type skeleton, the Cl 7-side chain of which is transformed into a six-member lactone ring. The withanolides and the related crgostancs arc tile only known natural steroids obtained Ifum the same family dial have representatives with both a- and -orientations of the Cl7 side chain. 

Regardless of the mechanistic details, it is the obvious correlation of the y-gauche effect with steric crowding which provides the bulk of the information on steroid stereochemistry. Early evidence of this was reported (51) for a series of a/b-cis steroids (i.e. 5/7). It is found that the C-19 methyl signal moves to high frequency by 11-12 ppm, compared with that of their 5cr counterparts. Very shortly thereafter the same... 

Cholic acid is an A-B cis steroid because the groups at the fusion of ring A and ring B have a cis relationship. 

Problem 27.9 Lithochoiic arid is an A-B cis steroid found in human bile. Draw lithocholic aacl... 

I) Consider three structurally similar Cis steroids —testosterone, an-drostenedione, and dehydroepiandrosterone. Each of these compounds is secreted into the blood stream by glands, and after provoking its biochemical effect, is metabolized and excreted. If the only source of the plasma pool were provided by the glandular secretion of the hormone, then the secretion rate would be used to calculate the plasma concentration. However, the picture in the case of the three Ci steroids is complicated by the fact that the three compounds are peripherally interconvertible. Since both glandular secretion and peripheral conversion of precursors contribute to the plasma pool, the production rate is used to... 

The adrenal cortex also secretes small quantities of the estrogenic steroids (Cis steroids)." However, 17P-estradiol and estrone are largely derived from the gonads and from peripheral conversion of testosterone and androstenedione by the aromatase enzyme located in other tissues, such as fat and the liver. 

Naftolin, F., Neutral Ci -steroids and steroid sulfates in human pregnancy. Steroids 8, 179-193 (1966). 

ANALYTICAL USE OF CTD-CIS STEROIDS FOR INFORMATION ON THE CaiEMOTOPOGRAPHY OF THE DIGITALIS RECOGNITION MATRIX 155... 

Table 4.1. IMPACT OF CHANGES IN THE GEOMETRY OF CID-cis STEROIDS OF THE DIGITALIS TYPE ON THE APPARENT GIBBS ENERGY OF INTERACTION (-AG ) WITH NaYK -ATPase PREPARATIONS FROM HUMAN HEART (HH), HUMAN BRAIN CORTEX (HB), AND GUINEA-PIG HEART (GH) REPERCUSSIONS ON THE ENERGETIC CONTRIBUTIONS OF THE SIDE-CHAINS AT C-3fi AND C-np. METHODOLOGICAL DETAILS IN [87,88].

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