Endoperoxides steroidal

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 . 

Endoperoxides derived from cyclohexa-1,3-dienes are the most abundant in this category due to the greater stability compared to their analogues and to the substrate availability [5c,8d]. This subunit is present in a great number of terpene and steroid products. Most of steroid endoperoxides are 5,8-derivatives in which the oxygen bridge has the a-configuration [l,5c,8d]. The steric demand of the methyl at C-10 appears... 

According to Bergmann and Hirschmann,198 only homoannular dienes of the steroids are expected to give endoperoxides. The for-... 

Non-steroidal anti-inflammatory drugs inhibit cyclooxygenase, the enzyme that limits the conversion of arachidonic acid to cyclic endoperoxide, an intermediate in prostaglandin production. This blocks the binding of agents released by the prostaglandin cascade to nociceptive receptors. 

Meade EA, Smith WL, DeWitt DL. Differential inhibition of prostaglandin endoperoxide synthase (cyclooxygenase) isozymes by aspirin and other non-steroidal anti-inflammatory drugs. J. Biol. 

First statement Aspirin and ibuprofen are non-steroidal anti-inflammatory drugs (NSAIDs) and theoretically the best OTC analgesics for dysmenorrhoea. Second statement NSAIDs act by promoting the action of the enzyme cyclooxygenase, thus preventing the formation of prostaglandin endoperoxides from arachidonic acid produced when tissue is damaged. 

Epidioxides (sometimes called endoperoxides) can be prepared from acenes, from suitable steroids, and from dienes of low molecular weight ([Pg.274]

During the last ten years numerous discoveries were made in this field, and research was initiated in a large number of new areas. Among the mile-stones of this last decade were the isolation of the potent endoperoxide intermediates the discovery of non-steroidal anti-inflammatory drugs as inhibitors of the fatty acid cyclooxygenase the discovery of the mutually antagonistic endoperoxide products. 

Steroidal dienes undergoes stereospecific photo-oxygenation, the endoperoxide being formed by the addition of molecular singlet oxygen to the least hindered face of molecule. 

A synthetically useful example for perfect regioselective control was reported for furan photooxygenation in the presence of a tricarbonyliron-protected cyclohexadiene. Numerous examples are known for terpene and steroid substrates with 1,3-cyclohexadiene subunits in which endoperoxides have been isolated in good to excellent yields, e.g., dehydro-6-ionone 25 gives the endoperoxide 26 in 50% yield by using rose bengal as the sensitizer in methanol. ... 

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