https://wiki.tiffa.net/w/index.php?action=history&feed=atom&title=Translations%3AVitamin_D%2F88%2Fen 2026-06-01T08:12:03Z Revision history for this page on the wiki MediaWiki 1.43.0 https://wiki.tiffa.net/w/index.php?title=Translations:Vitamin_D/88/en&diff=110213&oldid=prev 2024-01-25T23:41:41Z

<p>Importing a new version from external source</p> <p><b>New page</b></p><div>=== Photochemistry ===<br /> [[File:Vitamin D biosynthesis in fungi and animals.svg|thumb|upright=1.35|The photochemistry of vitamin D biosynthesis in animal and fungi]]<br /> [[File:Calcitriol-Biosynthese 2.svg|thumb|upright=1.35|Thermal isomerization of [[previtamin D3|previtamin{{nbsp}}D&lt;sub&gt;3&lt;/sub&gt;]] to vitamin D&lt;sub&gt;3&lt;/sub&gt;]]<br /> The transformation that converts 7-dehydrocholesterol to vitamin D&lt;sub&gt;3&lt;/sub&gt; occurs in two steps. First, 7-dehydrocholesterol is [[photolysis|photolyzed]] by ultraviolet light in a 6-electron [[conrotatory]] ring-opening [[electrocyclic reaction]]; the product is [[previtamin D3|previtamin{{nbsp}}D&lt;sub&gt;3&lt;/sub&gt;]]. Second, previtamin{{nbsp}}D&lt;sub&gt;3&lt;/sub&gt; spontaneously [[isomer]]izes to vitamin{{nbsp}}D&lt;sub&gt;3&lt;/sub&gt; ([[cholecalciferol]]) in an [[antarafacial]] [[Sigmatropic shift#.5B1,7.5D Shifts|sigmatropic [1,7] hydride shift]]. At room temperature, the transformation of previtamin{{nbsp}}D&lt;sub&gt;3&lt;/sub&gt; to vitamin D&lt;sub&gt;3&lt;/sub&gt; in an organic solvent takes about 12 days to complete. The conversion of previtamin{{nbsp}}D&lt;sub&gt;3&lt;/sub&gt; to vitamin D&lt;sub&gt;3&lt;/sub&gt; in the skin is about 10 times faster than in an organic solvent.</div>

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