Total Syntheses of (−)‐Transtaganolide A, (+)‐Transtaganolide B, (+)‐Transtaganolide C, and (−)‐Transtaganolide D and Biosynthetic Implications

The Ketene‐Surrogate Coupling: Catalytic Conversion of Aryl Iodides into Aryl Ketenes through Ynol Ethers

“…[9] In contrast, the crosscoupling of alkoxyacetylenes remains poorly developed. In this context, Stille coupling of alkoxyethynyl tin reagents has been described, [10] but Sonogashira coupling could directly connect the aryl iodides and ynol ethers without necessitating prefunctionalization of the acetylene motif. While the Sonogashira coupling between menthol-derived ynol ethers and terminal vinyl iodides has been investigated, [11] the only Sonogashira coupling between an ynol ether and an aryl halide of which we are aware proceeded in only 11 % yield.…”

Total Syntheses of Basiliolide A1, Basiliolide A2, Basiliolide C, and their Structural Analogues

“…The NMR spectroscopic data of the synthetic (±)‐basiliolide C ( 4 ) are identical to those reported in the literature ,. [10e]…”

“…In 2013, Stoltz's group reported asymmetric syntheses of transtaganolides and basiliolides by introducing a chiral TMS (trimethylsilyl) group to the Claisen rearrangement/Diels–Alder substrate as a chiral auxiliary. [10d] To develop an asymmetric synthesis based on our synthetic route, we can use an asymmetric catalytic cyclopropanation, since this would set the stage for the establishment of the stereogenic centres at C‐8 and C‐9 of 9 . The asymmetric catalytic cyclopropanation of ( E )‐ 5 was studied with a variety of Cu II[17] and Rh II[18–20] catalysts.…”

“…Only Stoltz's group have successfully established the seven‐membered acyl ketene acetal (C‐ring) using a formal [5+2] annulation. They found that the biological activities of the synthetic transtaganolide C (basiliolide A 2 )[10e] were consistent with those of the natural compound, which indicates that its activity was not caused by a trace amount of thapsigargin contaminating the isolated sample. Our group previously reported a diastereoselective synthesis of (±)‐basiliolide B and epi ‐8‐basiliolide B, featuring a cyclopropanation/ring‐opening strategy to diastereoselectively establish the stereogenic centre at C‐8, IMDA for the synthesis of the decalin core, and a biomimetic O ‐acylation for the C‐ring formation.…”

“…Because of this, our group has begun a long‐term project towards the development of an efficient synthesis of the basiliolides and their structural analogues for a systematic mechanistic study. In addition to our own synthetic efforts, the groups of Dudley, Johansson, Sterner, and Stoltz have reported the synthesis of the ABD‐ring of the basiliolide skeleton through a bioinspired Claisen rearrangement (only moderate diastereoselectivity at C‐8) and intramolecular Diels–Alder (IMDA) cycloaddition. Only Stoltz's group have successfully established the seven‐membered acyl ketene acetal (C‐ring) using a formal [5+2] annulation.…”