Mestranol, in oral contraceptives

Carignan, G. Lodge, B.A. Skakum, W. Quantitative einalysis of ethynodiol diacetate and ethinyl estra-diol/mestranol in oral contraceptive tablets by high-performance liquid chromatography. J.Pharm.Sci., 1982, 71, 264-266... 

Synthetic steroid hormones retain the common steroid nucleus, but they may contain novel substituents that affect their pharmacological activity. The two most widely used synthetic steroid estrogens are ethinyl estradiol (Estinyl) and mestranol, found in oral contraceptives. Synthetic steroids containing an ethinyl substitution are metabolized more slowly. Thus, these synthetic steroid hormones have better oral absorption properties and extended biological half-lives than the natural estrogens. 

Today, a variety of therapeutic estrogens are produced semisynthetically from estrogen intermediates synthesized from diosgenin and other natural precursors. Two semisynthetic, orally active estrogens are ethinyl estradiol (5.27) and its 3-methyl ether (5.28, mestranol). Both of these are used in oral contraceptives (see section 5.8.3). Quinestrol (5.29) is another semisynthetic estrogen. The most important property of the semisynthetic estrogens is their increased oral effectiveness. 

Mestranol and mestranol-containing oral contraceptive preparations seem to impair glucose tolerance possibly more than ethynyloestradioi and oral contraceptive preparations derived therefrom [208], particularly where there is a history of gestational (subclinical) diabetes. This situation may be reversed in the presence of progestagen (vide infra). 

Devise a synthesis of mestranol, a synthetic estrogen used in oral contraceptives, from the female sex hormone estradiol. You may use any needed organic compounds or inorganic reagents. 

Further investigations resulted in the discovery that etherification of the 3-hydroxy group of ethinyl estradiol resulted in formation of potent orally active oestrogens such as mestranol (the 3-methyl ether) and quinestrol (the 3-cyclopentyl ether), although this is not now used in oral contraceptives (Fig. 20.27). 

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. 

The oral contraceptive agent Mestranol is synthesized using a carbonyl addition reaction like that shown in Problem 8.42. Draw the structure of the ketone needed. 

Two synthetic estrogens are used in hormonal contraceptives in the United States, ethinyl estradiol (EE) and mestranol. Mestranol must be converted to EE in the liver to be active. It is approximately 50% less potent than EE. Most combined oral contraceptives (OCs) contain estrogen at doses of 20 to 50 meg of EE daily. The contraceptive ring produces one-half the serum concentration of EE derived from a 30-mcg OC. 

Estrogens Mestranol i /0H Oral contraceptive - Effluents <1-8 ng L 1 [30] Degraded in aerobic... 

Oppenauer oxidation of the enol ether (34) affords the corresponding 17 ketone (37) (the enol ether is stable to the basic oxidation conditions). This ketone affords the corresponding 17a-ethynyl compound on reaction with metal acetylides. Hydrolysis of the enol ether under mild conditions leads directly to ethynodrel (39), an orally active progestin. This is the progestational component of the first oral contraceptive to be offered for sale. Treatment of the ethynyl enol ether with strong acid leads to yet another oral progestin employed as a contraceptive, norethindrone (40). ° In practice these and all other so-called combination contraceptives are mixtures of 1-2% mestranol... 

Today, the major oral contraceptives on the market in the United States are mixtures of the estrogen, 17[Pg.236]

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