Dehydro-P-ionone

Ethers and esters derived from the alcohol also show activity in vivo. The ring structure of retinol ((i-ionone), or the more unsaturated ring in 3-dehydroretinol (dehydro-P-ionone), is essential for activity hydrogenation destroys biological activity. Of all known derivatives, all-/ran,v-retinol and its aldehyde, retinal, exhibit the greatest biological potency in vivo 3-dehydroretinol has about 40% of the potency of all-bms-retinol. 

In addition to differences in thek methodology to extend the carbon chain, these manufacturers differ in thek syntheses of P ionone. P Ionone is commercially prepared via an acid-cataly2ed rearrangement of pseudoionone (26). This intermediate is manufactured on an industrial scale from either citral (27) or dehydro-hnalool (28) (21) (Fig. 5). 

Triphenylstannane reduced the double bond in dehydro-)J-ionone in 84% yield [872], Complex copper hydrides prepared in situ from lithium aluminum hydride and cuprous iodide in tetrahydrofuran at 0° [873], or from lithium trimethoxyaluminum hydride or sodium bis(methoxy-ethoxy)aluminum hydride and cuprous bromide [874] in tetrahydrofuran at 0° reduced the a,p double bonds selectively in yields from 40 to 100%. Similar selectivity was found with a complex sodium bis(iron tetracarbonyl)hydride NaHFe2(CO)g [875]. 

Norisoprenoids detected in negligible amounts or not found in the free fraction of studied wines, were relatively abundant in the bound fraction. The Qs-norisoprenoid pattern was composed by 3-hydroxy-P-damascone, 3-oxo-a-ionol, 3-hydroxy-7,8-dihydro-(3-ionol and, in smaller concentrations, a-ionone and 4-oxo-isophorone. By contrast, (3-damascenone -detected in the free fraction in wines- was not detected in bound form as this compwimd is formed principally from the precursors 3-hydroxy-P-damascone and 3-hydroxy-7,8-dehydro-P-ionol the highest concentration of both compounds found in fraction of aroma of Rojal wines could be related to that in the free fraction Rojal wines paosented lower concentration of P-damascenone. 

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