Search

An enantioselective synthetic approach for preparing manginoids and guignardones, two types of biogenetically related meroterpenoids, is reported. This bioinspired and divergent synthesis employs an oxidative 1,3‐dicarbonyl radical‐initiated cyclization and cyclodehydration of the common precursor to forge the central ring of the manginoids and guignardones, respectively, at a late stage. Key synthetic steps include silica‐gel‐promoted semipinacol rearrangement to form the 6‐oxabicyclo[3.2.1]octane skeleton and the Suzuki–Miyaura reaction of vinyl bromide to achieve fragment coupling. This synthesis protocol enables the asymmetric syntheses of four fungal meroterpenoids from commercially available materials. [ABSTRACT FROM AUTHOR]

An enantioselective synthetic approach for preparing manginoids and guignardones, two types of biogenetically related meroterpenoids, is reported. This bioinspired and divergent synthesis employs an oxidative 1,3‐dicarbonyl radical‐initiated cyclization and cyclodehydration of the common precursor to forge the central ring of the manginoids and guignardones, respectively, at a late stage. Key synthetic steps include silica‐gel‐promoted semipinacol rearrangement to form the 6‐oxabicyclo[3.2.1]octane skeleton and the Suzuki–Miyaura reaction of vinyl bromide to achieve fragment coupling. This synthesis protocol enables the asymmetric syntheses of four fungal meroterpenoids from commercially available materials. [ABSTRACT FROM AUTHOR]

A divergent synthetic approach to biogenetically related diterpenoids such as ent‐kauranes, ent‐trachylobanes, ent‐beyerane, and ent‐atisane has been developed. The unified synthetic route involves the De Mayo reaction to rapidly generate the bicyclo[3.2.1]‐octane moiety of ent‐kaurane. The key reactions also include bioinspired nucleophilic cyclopropanation generating the [3.2.1.02,7]‐tricyclic core of ent‐trachylobane and regioselective cyclopropane fragmentation furnishing ent‐beyerane and ent‐atisane through the nucleophilic attack and protonation of the cyclopropane ring. This strategy enables the asymmetric total syntheses of six diterpenoids from the commercially available geraniol. [ABSTRACT FROM AUTHOR]

A divergent synthetic approach to biogenetically related diterpenoids such as ent‐kauranes, ent‐trachylobanes, ent‐beyerane, and ent‐atisane has been developed. The unified synthetic route involves the De Mayo reaction to rapidly generate the bicyclo[3.2.1]‐octane moiety of ent‐kaurane. The key reactions also include bioinspired nucleophilic cyclopropanation generating the [3.2.1.02,7]‐tricyclic core of ent‐trachylobane and regioselective cyclopropane fragmentation furnishing ent‐beyerane and ent‐atisane through the nucleophilic attack and protonation of the cyclopropane ring. This strategy enables the asymmetric total syntheses of six diterpenoids from the commercially available geraniol. [ABSTRACT FROM AUTHOR]

Cyclopropane, dihydropyrrole, and azepane ring systems were synthesized conveniently from sulfinate‐tethered triazoles. The divergent synthetic strategy started with the unique 1,3‐sulfinate migration of an α‐imino carbene. The efficient reaction allowed control of the zwitterion bearing multiple reactive sites depending on the increased stability of the resulting carbocation and anion. The sulfinate was converted to a sulfone after the group migration, and a stable anion bearing two electron‐withdrawing groups was thus formed. Catalytic amounts of iodide acted as a switch for the synthesis of cyclopropanes and dihydropyrroles. The reaction merits including readily available substrates, mild reaction conditions, and excellent functional group compatibility qualified this protocol a possible synthetic tool for cyclic compounds, especially for N‐heterocycles. [ABSTRACT FROM AUTHOR]

Main observation and conclusion: An efficient rhodium(II)‐catalyzed [4+3] cyclization reaction of 1‐sulfonyl‐1,2‐3‐triazoles and indoles was developed. Azepino[5,4,3‐ cd]indoles, which are widely distributed in ergot alkaloids with various biological activities, could be obtained in good to excellent yields. In addition, the total synthesis of (±)‐aurantioclavine was completed in four steps from the known compound 1a adopting this [4+3] cyclization as a key step. [ABSTRACT FROM AUTHOR]