Synthesis of (.+-.)-8-Deisopropyladunctin B

A gem‐Dibromocyclopropane Ring‐Expansion/Mizoroki‐Heck Cyclisation Route to Tetrahydrodibenzofurans

“…Notable examples include the morphinan alkaloids such as codeine ( 1 ), [2] the biogenetically related galanthamine ( 2 ) [3] and the ribisins such as congener A ( 3 ) [4] (Figure 1). The significance of this framework has prompted the development of a range of methods for their preparation [1–4] including ones involving relay catalysis, [1a] the arylation of iodonium ylides, [1b] intramolecular nucleophilic additions, [1d] dearomative processes, [1e,f,n,2a] rearrangement reactions of various forms, [1h,j,k,l,m,3c] Mitsunobu cyclisations, [4e] and enzymatic dihydroxylations [4d] . However, the most common approaches have involved palladium‐catalyzed processes [4a] amongst which Mizoroki‐Heck cyclisation reactions [1g,1i,1 ° ,1p,2b,3a,3b] are predominant.…”

Enantioselective Total Syntheses of (+)-Hostmanin A, (−)-Linderol A, (+)-Methyllinderatin and Structural Reassignment of Adunctin E

“…Adunctin B ( 1 ), E ( 4 ), and linderol A ( 6 ) have four contiguous stereocenters at 1″, 4″, 5″, and 6″ positions. Interesting structural features coupled with potent biological activities of adunctins and linderols have proven to be a fertile ground for total synthesis …”

“…Most of the previously reported syntheses of adunctin B ( 1 ) and linderol A ( 6 ) are racemic, tedious (15–20 step long linear sequences) and are not stereoselective. Herein, we report protecting group free, concise, and gram-scale enantioselective total syntheses of (+)-methyllinderatin ( 5 ), (+)-hostmanin A ( 7 ), and (−)-linderol A ( 6 ) and the structural reassignment of adunctin E ( 4 ).…”

Total Synthesis of Adunctin B

“…The first racemic synthesis of adunctin B ( 2 ) was reported by Arimitsu et al in 2011 from commercially available 4,6-dimethoxysalicylaldehyde with 1.22% overall yield in 16 steps, using the coumarin rearrangement strategy, previously developed in their lab. Encouraged by our recent syntheses of methyllinderatin, linderol A, and adunctin E, we became interested in the total synthesis of adunctin B. Herein, we report a concise total synthesis of (±)-adunctin B ( 2 ) using a highly atom economic and diastereoselective Friedel–Crafts reaction, followed by palladium catalyzed Wacker-type oxidative cyclization.…”