Survey of Synthetic Approaches to Natural (Peyssonenynes) and Unnatural Acetoxyenediynes

Four convergent synthetic approaches to acetoxyenediynes have been explored to gain access to peyssonenynes A and B, which are natural products isolated from the red alga Peyssonelia caulifera. After optimization of the routes with a palmitic acid based model system, the synthesis of the peyssonenynes was completed by using, as the key steps, 1) Ni/Cu co‐catalyzed cross‐coupling of terminal alkynes, 2) Sonogashira cross‐coupling, 3) the addition of a diynyl anion to a Weinreb amide, and 4) the previously reported Cadiot–Chodkiewicz cross‐coupling reaction. Because bulky amide bases stereoselectively provided the (E)‐ and (Z)‐acetoxyenynes from the precursor ynones, the cross‐coupling routes to obtaining the acetoxyenediynes by using these stereochemically homogeneous intermediates are comparable to the alternatives in which enolacetate formation of the acetoxyenediyne motif takes place at a late stage in the synthesis.