Taxusin synthesis

Uses of FeCl3/Ac20 methodology in synthesis include the taxusin synthesis of Holton et al. (Sch. 2) [15], the Forsyth and Clardy synthesis of (+)-didemnenones A and B [16], and the synthesis of a nodulation factor (NodRf-III) by Fraser-Reid and coworkers [17]. 

Kuwajima s Synthesis of ( )-Taxusin. Two key transformations are involved in Kuwajima s synthesis30 (1) construction of the tricyclic taxane skeleton via cyclization of the eight-membered B ring between C-9 and C-10 and (2) subsequent installation of the C-19 methyl group onto the ring system. 

Finally, the C-20 group is introduced to the C ring, thus finishing the synthesis of ( )-taxusin in 25 steps (Scheme 7-47). 

Paquette, L. A. Zhao, M. Enantiospecific total synthesis of natural (+)-taxusin. 1. Retrosynth-... 

During a second-generation synthesis this problem was solved by application of a different reaction sequence. Even the introduction of additional hydroxyl functionalities could be accomplished, thus guiding the development from a naturally occurring terpene to the unnatural enantiomer of taxusin (104). This first synthesis of (-)-taxusin is presented in Scheme 32. 

The above results were again applied by Holton in the even more challenging synthesis of taxusin (83). The cornerstone of the strategy is the fragmentation of the hydroxylated alkene (91) to the ketone (92) via the unstable epoxide (Scheme 31). This (-)-taxusin (83) synthesis requires more than 30... 

Amongst those researchers that have studied the anionic oxy-Cope rearrangement, the achievements of Paquette are especially noteworthy. Not only has he been successful at utilizing it for complex natural product synthesis, " he and his coworkers have also provided novel insights into the subtle details which influence patterns of reactivity in these well-studied systems. Primary amongst these studies were those directed at natural (+)-taxusin - which featured the anionic oxy-Cope rearrangement/enolate... 

There has been great interest in the synthesis of taxanes, as a consequence of the important anticancer properties of taxol, the best known member of this class of compounds. In Holton s landmark synthesis of (-)-taxusin (56), a number of interesting observations characteristic of the general aspects of chelation-controlled processes can be made (Scheme 2.6) [65]. The addition of 1-lithio-l-methoxyethene to 54 proceeds optimally in hexane to furnish adduct 55 with >30 1 diastereoselectivity. 

Since Still introduced the use of a-alkoxyorganostannanes as precursors of a-alk-oxyorganolithium by hn-lithium exchange [335], this chemistry was exploited in a variety of applicahons including the stereocontrolled synthesis of complex natural molecules, such as Zoanthamine [336] and Aspidospermin [337] alkaloids and (+)-Taxusin [338]. 

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