Synthesis of Enantiomerically Pure (−)‐Hypnophilin

Abstract

Enantiomerically pure (—)‐hypnophilin 2 can be prepared on a 100 mg scale in a simple reaction from catalpol 1. The stereoselectivity of the individual steps was demonstrated by X‐ray structure analyses of two important intermediate products.

Total Synthesis of (−)-Coriolin

“…The different rotation values for the same compound 15 have been reported by Demuth (−115.4°),10d by Weinges (+34°), and now by us (+42.5°). Furthermore, compound 18 was reported to have a rotation of −105.2° by Demuth,10d which is quite different from our observation (+90.4°).…”

“…Indeed, enone 14 was obtained in good yield by successive treatment of enone 13 with a mixture of thiophenol and the corresponding lithium salt followed by an aqueous NaOH solution (Scheme ). Removal of the benzyl group by boron tribromide afforded the known alcohol 15 ; , accordingly, the stereochemistry of the tricyclic system was confirmed at this stage . The ( S )-configuration at the C2 position (coriolin numbering) indicates that the second [3+2] annulation reaction occurred at the convex face of vinyl sulfide 11 .…”

Synthesis of Polyquinane Natural Products: An Update

“…Weinges and co-workers − have restructured the iridoid catalpol ( 271 ) into the diquinane 272 through a series of transformations. Further conversion of the diquinane 272 into Matsumoto's 138k intermediate 273 constituted a formal synthesis of coriolin ( 212 ) (Scheme ).…”

“…Weinges and co-workers [141][142][143] Weinges and co-workers 144,145 have also accomplished the enantioselective syntheses of (-)-coriolin ( 212) and (+)-coriolin-B ( 274) from (S)-carvone, through an extension of their hirsutene strategy (Schemes 65 and 66). The lactone 275 obtained from (S)-carvone was transformed into enyne 276, and the triquinane 277 was assembled employing a samarium iodide-mediated tandem radical cyclization reaction.…”

Three-Component Coupling via the Squarate Ester Cascade as a Concise Route to the Bioactive Triquinane Sesquiterpene Hypnophilin

“…The isolation and characterization of this linearly fused triquinane attracted early attention as a consequence of its reputed antibacterial and antitumor properties . Three syntheses of 12 have since been disclosed from laboratories headed by Little, Curran, and Weinges . Application of the 1,3-diyl trapping reaction and a tandem radical cyclization featured prominently in the first two routes.…”