Stenine group synthesis

Quite recently, a domino Diels-Alder/Prins/pinacol reaction was reported by Barriaulfs group [38]. This novel method is very reliable and efficient for the synthesis of highly functionalized bicyclo[m.n.l]alkanones. In addition, Aube and coworker [39] used a combination of a Diels-Alder and a Schmidt reaction within the total synthesis of the Stemona alkaloid stenine [40]. 

The first total synthesis of (—)-tuberostemonine (4) was described by Wipf and coworkers 66). The oxidation of IV-carbobenzyloxy tyrosine with hypervalent iodine afforded, after benzoylation of the tertiary hydroxyl group, bicyclic 113 which was employed by Wipf and coworkers in their synthesis of (—)-stenine (Scheme 2) and served here as the scaffold for the installation of the stereogenic centers of (—)-tuberostemonine (4) (Scheme 6). Substitution of PBnj for the previously used PBuj allowed them to... 

Shea s group applied this type 2 A-acylnitroso intramolecular Diels-Alder cyclization to the synthesis of tricyclic BCD core of stenine. The C2-tethered cyclic diene 103 was converted to the corresponding hydroxamic acid by treatment with NH20H-HC1, which, upon oxidation with BU4NIO4, was converted to 104 as a 6 1 mixture of diastereomers. Reductive N-0 bond cleavage of 104 yielded the alcohol 105 and its diastereomer (not shown). Further elaboration of 105 provided the tricyclic core structure 106 of stenine (Scheme 4.22) [41],... 

The Keck radical allylation is a representative example of a radical fragmentation reaction employing the reagent allyltributyltin in the allylation process. " The first synthesis of the Stemona alkaloid stenine by Hart in 1990 established an iodolactonization/Keck allylation (93 —> 94) sequence (Scheme 25.44) as a solution to the problem of stereoselective ethyl group installation. ... 

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