Total synthesis of (+)-elemol by photoannelation

Abstract

A total synthesis of the monocyclic sesquiterpene elemol has been accomplished in seven steps and 16.7% overall yield. The key new carbon-carbon bonds were formed by the [2 + 2] photochemical cycloaddition reaction between 2,2,6-trimethyl-4íí-l,3-dioxin-4-one and -terpineol, a reaction that occurred with essentially complete regioselectivity (head/head) and good alkene face selectivity (3.35/1). The 35-38% enantiomeric purity of the starting (-)-a-terpineol was translated into optically active elemol predominating in the unnatural (+) enantiomer (ee = 31-40%).

Photochemische Reaktionen als Schlüsselschritte in der Naturstoffsynthese

“…Sinn finden sich in der Synthese von (+)-Elemol [332] und (+)-Valeranon. [333] 3(2H)-Furanone sind ebenfalls latente 1,3-Dicarbonylbausteine und wurden folglich für Naturstoffsynthesen im Sinne einer Sequenz [2+2]-Photocycloaddition/Fragmentierung genutzt.…”

Stereoselective Intermolecular [2 + 2]-Photocycloaddition Reactions and Their Application in Synthesis

“…these dioxinones can be found in the synthesis of elemol. 114 Chirally modified 1,3-dioxin-4-ones have been successfully used in an approach to iridoids (see also section 2.3.1.2.). 115 Related cyclic alkenones which undergo de Mayo-type reactions include 2,3-dihydro-4-pyrones 116 and furan-3(2H)-ones.…”

Corrosion News

“…Hydrolysis afforded carboxylic acid 256 , which was subjected to Peterson olefination and reduction to provide the already extensively discussed (+)‐grandisol ( 73 , Scheme ) 331. Further applications of 1,3‐dioxinones in this context can be found in the syntheses of (+)‐elemol332 and (+)‐valeranone 333…”