Stereochemical assignment of the unique electron acceptor 5′-hydroxyphylloquinone, a polar analog of vitamin K₁ in photosystem I

<p>A unique electron-accepting analog of vitamin K₁ found in photosystem I in several species of oxygenic photosynthetic microorganisms was confirmed to be 5′-hydroxyphylloquinone (<b>1</b>) through stereo-uncontrolled synthesis. Furthermore, the stereochemistry of <b>1</b> obtained from <i>Synechococcus</i> sp. PCC 7942 was assigned to be 5′<i>S</i> using proline-catalyzed stereocontrolled reactions.</p> <p>Polar vitamin K₁ (<b>1</b>) was synthesized. Stereochemistry of natural <b>1</b> was determined to be (5′<i>S</i>) after a derivation, where the same derivative was also synthesized.</p