Total Synthesis of (±)‐Integrifolin

Abstract

The total synthesis of (±)-integrifolin has been achieved for the first time through the stereoselective preparation of the bicyclo[5.3.0]decane skeleton based on the tungsten-catalyzed cyclization of acyclic trienynes under photoirradiation conditions. Further key transformations of the cyclized product are the Tamao oxidation through cyclic silyl ether, the introduction of two oxygen functionalities by the oxidation of the diene and the construction of three exo-methylene moieties.

Radical Approach to the Chiral Quaternary Center in Asperaculin A: Synthesis of 9-Deoxyasperaculin A

“…Unfortunately, the synthesis of 14 proved to be very difficult. Attempted oxidative lactonization of 12 by PhI­(OAc) 2 –TEMPO provided only the unsaturated aldehyde 13 with no trace of 14 , which might be due to the geometrical constraints preventing the functional groups coming close for the desired cyclization (Scheme ). Use of other reagents like MnO 2 , PCC, TPAP-NMO, and DMP gave only mixtures of overoxidized products.…”

“…Unfortunately, all of these attempts resulted only in failures. Then a straightforward transformation was attempted involving hydrogenation of the double bond with PtO 2 –H 2 , which freed the molecule from geometric constraints leading to a successful oxidative lactonization in the following step with PhI­(OAc) 2 –TEMPO to furnish 9-deoxyasperaculin A ( 3 ) having the elusive dioxa[5.5.5.6]­fenestrane framework of the target (Scheme ). Its formation in the desired stereochemistry was confirmed by NOE experiments (see the Supporting Information).…”

Recent advances in the syntheses of guaianolides

“…The remaining part of further oxygenation could be achieved stepwise with many available methods. An interesting strategy involving tungsten-catalyzed photocyclization of acyclic trienynes for stereoselective preparation of the bicyclo[5.3.0]decane skeleton was applied in the synthesis of (±)-integrifolin 3 by Iwasawa and co-workers 28 in 2016 (Scheme 8). Propargyl alcohol 62 (prepared in 3 steps from 5-hexyn-1-ol 61 ) was hydrosilylated by Pt-catalysis regioselectively to produce ( E )-alkenylsilane and oxidation of allyl alcohol gave enone 63 .…”

Prins cyclization of 1,3-dioxinone: synthesis of 11-epi-badkhysin

“…Representative methodologies for these medium-sized carbocyclic rings are ene-cyclization, 10 the intramolecular Nozaki-Hiyama-Kishi type coupling reaction, 11 the metathesis approach, 10a,12-15 oxi- dative ring-opening, 16 photosantonin-type ring rearrangement, 17 pinacol coupling, 18 radical cyclization, 19 and tungstencatalyzed cyclization. 20 Badkhysin, a highly functional 6,12-guaianolide type STL, was first isolated from the roots of Ferula oopoda. 21 To the best of our knowledge, badkhysin is not yet achieved by total synthesis.…”