New strategy for the synthesis of the taxane diterpenes: Formation of the BC-rings of taxol via a [5+2]-pyrylium ylide-alkene cyclization, ring expansion strategy

Progress in the Construction of Cyclooctanoid Systems: New Approaches and Applications to Natural Product Syntheses

“…Magnus and co-workers have created the B ring of taxane via reduction of the internal cyclopropyl bond in the keto ether 546 with sodium naphthalenide to furnish 547 in a highly selective manner and in quantitative yield, Scheme 112 …”

Taxane Diterpene Synthesis Studies. Part 2: Towards Taxinine—Enantiospecific Construction of an AB-ring Substructure Incorporating both Quaternary Carbon Centres and Attempts to Annulate the C-ring

“…That having been said, the preparation of closely related taxoids such as taxusin have been described by several groups. [7] Herein we detail an approach to the enantiomer of the natural product, namely ent-1 (Diagram 1), that has culminated in the stereocontrolled synthesis of AB-ring substructures incorporating the synthetically demanding C8 quaternary carbon centre [8] as well as that at C15.…”

Asymmetric Total Synthesis of Havellockate

“…The synthesis of aldehyde 6 commences with known enone 8 , which undergoes bromination followed by conjugate addition/elimination to afford β-cyanoenone 10 (Scheme A) . Luche reduction and subsequent alcohol protection furnishes nitrile 11 , which is converted to aldehyde 6 by reduction with DIBAL.…”

“…The synthesis of aldehyde 6 commences with known enone 8, 9 which undergoes bromination followed by conjugate addition/elimination to afford β-cyanoenone 10 (Scheme 1A). 10 Luche reduction and subsequent alcohol protection furnishes nitrile 11, which is converted to aldehyde 6 by reduction with DIBAL. The sulfone coupling partner is accessed from known acyl oxazolidinone 12 11 by γdeprotonation followed by α-alkylation with tert-butyl bromoacetate, which proceeds in >20:1 dr. Reductive auxiliary removal then affords enantioenriched alcohol 13 (Scheme 1B).…”