Natural steroid ergosterol

We report here the synthesis, biological activities and metabolism of the active forms of naturally occurring vitamin D analogues, especially active form of vitamin D4 (1comparison with those of l(X,25(OH)2D3. In addition, we introduce application of the synthetic procedure developed for the preparation of active forms of vitamin D analogues described here to the synthesis of biologically active natural steroids and the intermediates in ergosterol biosynthesis. 

P-Hydroxy steroids which contain the 5,7-diene system and can be activated with uv light to produce vitamin D compounds are called provitamins. The two most important provitamins are ergosterol (1) and 7-dehydrocholesterol (3). They are produced in plants and animals, respectively, and 7-dehydrocholesterol is produced synthetically on a commercial scale. Small amounts of hydroxylated detivatives of the provitamins have been synthesized in efforts to prepare the metaboHtes of vitamin D, but these products do not occur naturally. The provitamins do not possess physiological activities, with the exception that provitamin D is found in the skin of animals and acts as a precursor to vitamin D, and synthetic dihydroxalated... 

Peroxy derivatives of steroids have been isolated from both marine and terrestrial sources. They are most commonly 5a, 8a-endoperoxides with variations in the side-chains. The ergosterol peroxide 102 is the most ubiquitous endoperoxide-containing natural product and is isolated from a large number of sources. Ergosterol peroxide 102 was found to have antitumour activity against breast cancer and carcinosarcoma cell lines. A number of other steroidal endoperoxides have been reported which differ in the nature of the side-chain. Compound 103 was found to be an inhibitor of tumour promotion in mouse studies . 

A common feature of all products from the azole class is that their fungicidal activity is due to interference with the biosynthesis of fungal steroids, which are essential for cell wall construction in many of these organisms. The interference in ergosterol biosynthesis can occur at one or more points in the biosynthetic pathway depending on the nature of the azole. 

Nonetheless, the most fascinating and complex lipid type is sterols. They have a rigid steroid ring stmcture, which is a simple hydroxyl group as their polar head and a short flexible tail at the other end of the molecule. Of the many sterols found, two sterols exist whose significance in cells is above the others. Cholesterol is abundant in eukaryotic cells, and ergosterol is abundant in fungi. The reasons why nature has chosen these two specific sterols are not well understood. One is tempted to think that the properties of all sterols should be similar,... 

The branched isoprene unit, which is also synthesized from the C, pool, is the basic structure of terpenoids. Less condensed structures are used as volatile pheromones, e.g., jasmonic acid, menthol, or camphor, or as natural rubber material. More condensed structures such as steroids and hopanoids are part of membranes, influencing their fluidity. They are also highly specific to their source organisms. Best known are cholesterol (in animals and plants), ergosterol (in fungi), and brassicasterol (in diatoms). Besides cellulose, hopanoids are the most abundant biomolecules. 

The conversion of ergosterol (provitamin Da) (la) or 7-dehydro-cholesterol (provitamin Da) (lb) into the corresponding vitamins by sequential photolysis and thermolysis is an important commercial process and has received considerable study. Also, the nature of the steroid molecule, its conformational restrictions and rigid backbone, makes it... 

Therapy Vitamin D occurs In two forms 1) vitamin D2 or ergocalclferol, which Is produced by ultraviolet Irradiation of ergosterol, a plant steroid and 2) vitamin D3 or cholecalclferol, the naturally occurring form of the vitamin In animal tissues ... 

Calciferol is the anti-rachitic steroid obtained artificially. It was first regarded as being identical with vitamin D, and ergosterol was accepted as being the natural provitamin. However, in 1934, Waddell found that both irradiated cholesterol and cod-liver oil concentrates were more effective than calciferol, when given in equivalent dosage to rachitic chickens, and now it is believed that several different vitamins of the D type exist, including D, the anti-rachitic factor in natural liver oils, Dg, or calciferol, and Dg, the factor obtained from 7-dehydrocholesterol, which is its provitamin in crude cholesterol. 

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