Nickel-Catalyzed Coupling Producing (2<i>Z</i>)-2,4-Alkadien-1-ols, Conversion to (<i>E</i>)-3-Alkene-1,2,5-triol Derivatives, and Synthesis of Decarestrictine D

The 3-alkene-1,2,5-triol structure is not only a major framework of biologically important molecules but also a new functional-group-rich unit for synthesis of polyols and sugars. A method furnishing such triol derivatives <b>8</b> was developed and successfully applied to synthesis of decarestrictine D (<b>18</b>). First, coupling reaction of the unprotected alcohols <b>2</b> with borates <b>4</b> was investigated to produce the dienyl alcohols <b>6</b> with NiCl₂(dppf) in Et₂O/THF (5:1) at room temperature. The hydroxyl-group-directed epoxidation of <b>6</b> followed by palladium-catalyzed reaction with AcOH (Scheme ) furnished 3-alkene-1,2,5-triol derivatives <b>8</b>. Since each step proceeded with high stereo- and regioselectivities, the stereochemistry of <b>8</b> has been correlated with the olefin geometry of <b>6</b>. With the above transformation in mind, synthesis of the full carbon skeleton of decarestrictine D (<b>18</b>) could be designed easily and was completed successfully. Furthermore, a new seco acid <b>19b</b> with the MOM protective group for the three hydroxyl groups was found to afford macrolide <b>48</b> in a yield higher than those reported previously.