TRIP-Catalyzed Asymmetric Synthesis of (+)-Yatein, (−)-α-Conidendrin, (+)-Isostegane, and (+)-Neoisostegane

Abstract

The asymmetric allylation under the assistance of catalytic amounts of 3,3′-bis­(2,4,6-triisopropylphenyl)-1,1′-binaphthyl-2,2′-diyl hydrogen phosphate (TRIP) allows the concise construction of the lignan scaffold from simple aldehydes and allylic bromides with full control of the two formed stereocenters. This young methodology has been employed to synthesize four naturally and pharmaceutically active lignans. Members of the dibenzylbutyrolactone, the tetraline, and the dibenzocyclooctadiene classes have been synthesized in 40–47% overall yield along four-step synthetic routes.

Asymmetric Allylation Catalyzed by Chiral Phosphoric Acids: Stereoselective Synthesis of Tertiary Alcohols and a Reagent‐Based Switch in Stereopreference

“…These mild reagents allow insertion of the metal into the carbon‐halogen bond in the presence of esters in an apolar medium (e. g. toluene) – the requirement for asymmetric induction in the developed system [11] . This facilitates the existing routes to natural products like lignans substantially [12] . Additionally, the obtained products provide extremely versatile starting materials for a plethora of transformations [e. g., preparation of α‐keto esters, [13] (stereoselective) reduction of the obtained double bond, [14] conjugated 1,4‐addition of carbo‐ [15] and thia‐ [16] nucleophiles, Heck reactions, [17] and double bond isomerization [18] ].…”

Recent strategies and tactics for the enantioselective total syntheses of cyclolignan natural products

“…3A). 84 This paper discusses the total synthesis of (À)-a-conidendrin (142), as well as isostegane, neoisostegane, and (À)-yatein (15). Asymmetric TRIP-catalyzed allylation of benzyl protected vanillin 151 with bromolactone 152 yielded b-substituted a-methylenebutyrolactone 153 with nearly perfect diastereo-and enantioselectivity (d.r.…”

Diastereoselective allylation-based asymmetric total synthesis of 1,10-seco-guaianolides

“…2 a – c ,3,4 Various strategies have been devised to obtain this motif including the most common Barbier allylation of aldehydes using allyl bromolactones to directly set the exo -methylene group at the early stages. 2 c ,5 In this regard, a variety of metals such as Zn, 6 In, 6 a Cr, 7 Pd, 8 and Sn 9 and chiral ligands like BINOL-derived phosphoric acids 6 b and carbazole-containing bisoxazolines 7 b have been used in diastereoselective Barbier-type allylation to access the functionalized α- exo -methylene-γ-butyrolactone core 4 / 5 (Scheme 1a). Interestingly, in 2013, Xu reported a Pd-catalyzed allylation using Me 2 Zn giving the α- exo -methylene-γ-butyrolactone core 5 with a syn -configuration (Scheme 1a).…”