Estrogens, Methylated

Schriesheim found a solution of potassium f-butoxide in dimethyl sulfoxide useful as a homogeneous basic medium for study of the rate constants, activation energies, and entropies for the isomerization of olefins. Birch et al. found the reagent useful for the isomerization of (2), the primary product of Birch reduction of an estrogen methyl ether (1), to the conjugated diene (3). 

Methylation phenolic hydroxyl [estrogens] methyl ether... 

Finally the chemical aromatization of Ring A which occurs in nature in the biosynthesis of estrogens must be mentioned. It can be done by thermal cleavage of the C-19 methyl group in 1,4-dien-3-ones (H.H. Inhoffen, 1940 C. Djerassi, 1950) and was later achieved at lower temperatures with lithium — biphenyl in THF (H.L. Dryden, Jr., 1964). 

The two synthetic steroidal estrogens which have attained the greatest degree of therapeutic use are ethinyl estradiol [57-63-6] (EE) (5) and its 3-methyl ether, mestranol [72-33-3]((5). In contrast to the naturally occurring estrone derivatives, these acetylenic analogues are orally active and are the main estrogenic components of combination oral contraceptives (see Contraceptives) and certain estrogen replacement products. 

Reaction of estrone with a metal acetylide affords 17a-ethynyl-173-hydroxy-estradiol (etbynylestradiol, 30a EE). This compound is equipotent with estradiol by subcutaneous administration, but it is 15 to 20 times as active when administered orally. Ethynylation of the methyl ether of estradiol analogously affords mestranol (30b), It should be noted that the same factors apply in these reactions as in previously discussed reductions at 17 almost the sole products of these reactions are those which result from attack of reagent from the least hindered a side of the steroid. Ethynylestradiol and mestranol are of special commercial significance since the majority of the oral contraceptives now on sale incorporate one or the other of the compounds as the estrogenic component. 

Figure 7.7 Separation of ethynyl estrogens on silica gel 60 HPTLC plates using two 15-min developments in the solvent system hexane-chloroform-carbon tetrachloride-ethanol (7 18 22 1 v/v). Identification O methyl green (lane marker) 1 17a-ethynylestradiol ...

Experimental studies showed antitumoral effects of raloxifene in different in vitro preparations and animal models. Raloxifene has been able to inhibit the mitogenic effect induced by estrogens on ZR-75-1 cells, an estrogen responsive human breast cancer cell line (Poulin et al. 1989). In a well-accepted rat model of breast cancer induced by nitroso-methyl urea (NMU) raloxifene significantly suppressed the development of breast tumors and acted synergistically with 9 cis-retinoic acid (Anzano et al. 1996). 

Using a preemptive approach, Lebo et al. (2004) have shown that oleic acid and methyl oleate can be removed from triolein prior to use of the triolein in SPMDs (see Chapters 4 and 5). Dialysates from SPMDs prepared using triolein purified by the Lebo et al. (2004) method exhibited lower acute toxicity (Microtox assay) than SPMDs prepared with unpurified triolein. Also, the YES assay demonstrated that the purification method had removed all background estrogenic activity from SPMD extracts. Eor these reasons, the use of triolein purified by the method of Lebo et al. (2004) is standard for all SPMD studies conducted at CERC, USGS. Also, SPMDs with triolein purified by the Lebo et al. (2004) method are available from the commercial vendor upon request. 

Initially characterized as an autoantigen in a human connective tissue disease [62]. May be associated with methylation induced gene silencing and heterochromatin [64,65,103]. Interacts with a component of DNA repair machinery [308]. Functions in estrogen dependent repression of Snail. Aberrant Snail expression results in loss of expression of the cell adhesion molecule E-cadherin, an event associated with invasive growth of breast cancers [309]. 

---