<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The reaction proceeds via the 1, 3‐dioxane‐4‐ol intermediates (III) that can be trapped by Pinnick oxidation as α‐hydroxymethylalkanoic acids or by Wittig reaction with (IX) as 2‐methyl‐4‐hydroxymethyl‐alk‐2‐enoic acid esters.</p> </abstract>