Total Syntheses of Norrisolide‐Type Spongian Diterpenes Cheloviolene C, Seconorrisolide B, and Seconorrisolide C

Abstract

The first total syntheses of three unusual norrisolidetype rearranged spongian diterpenes, cheloviolene C, seconorrisolide B, and seconorrisolide C, have been accomplished via a common intermediate through late-stage ring-scissoring. The synthesis features a Wolff ring contraction for the synthesis of the trans-hydrindane system, and a crucial retro Diels-Alder reaction/intramolecular ene cyclization for the rapid stereoselective construction of the furo[2,3-b]furan system, which is commonly seen in rearranged spongian diterpenes.

Marine natural products

“…500 A number of terpenoids and steroids were also synthesised for the rst time in 2020. [501][502][503][504][505] In what may be a world rst, three Australian groups have independently reported the reassignment of the same class of sponge metabolite; all three publications were received at the respective journal editorial offices within four months of each other in late 2019, and all were published in January or early February of 2020. Reinspection of the NMR data of echinosulfone A suggested the originally published structure may be incorrect.…”

Ring contraction in synthesis of functionalized carbocycles

“…The synthesis of seconorrisolide C (25) used a Wolff rearrangement to prepare the [6,5]-bicycle 127 115 (Scheme 6(E)). Similar to Li's approach in the synthesis of taiwaniaquinone A (20) 103 and taiwaniadduct D ( 21) 104 (see Scheme 6(A)), the treatment of diazoketone 125 with collidine and benzyl alcohol at 160 1C produced ester 127 in 73% yield, a synthetic precursor of seconorrisolide C (25) (contractive synthesis: steps, 13 steps; 115 alternative synthesis: N/A).…”

“…(D) The enantioselective synthesis of precursor 125 of (À)-psiguadial B (24) through tandem Wolff rearrangement/asymmetric ketene addition 111. (E) Synthesis of seconorrisolide C (25) used a Wolff rearrangement to prepare the [6.5] bicycle 127 115. (F) Wolff rearrangement used to prepare tricycle 129 in the enantiospecific synthesis of (À)-presilphiperfolan-8-ol (26) 116.…”

Bio‐inspired Small Molecular Catalysis

“…The protocol has been widely used in the synthesis of natural products and bioactive compounds, as shown in Scheme 9. [ 75‐80 ] Other newly developed methodologies can also be utilized in the synthesis of natural products. For example, the chiral primary amine catalyzed photoalkylation reaction can be applied in asymmetric synthesis of four Ganoderma meroterpenoids natural products with different structural frameworks.…”