Pectenotoxin-2 Synthetic Studies. 3. Assessment of the Capacity for Stereocontrolled Cyclization To Form the Entire C1−C26 Subunit Based upon the Double Bond Geometry Across C15-C16
作者:Patrick D. O'Connor、Christopher K. Knight、Dirk Friedrich、Xiaowen Peng、Leo A. Paquette
DOI:10.1021/jo062513f
日期:2007.3.1
Second-generation synthetic routes to enantiopure sulfone 21 and aldehyde 24 are described. The union of these two intermediates by means of a Julia-Kocienski coupling gave rise to a series of E-configured building blocks that did not prove amenable to transannular cyclization. Alternatively, when the C15-C16 double bond was introduced with Z-geometry by Wittig olefination, spontaneous closure to generate a tetrahydrofuran culminated an ensuing direct dihydroxylation step. The structural assignment to 35, undergirded by detailed H-1 and C-13 NMR studies, is consistent with proper transannular bonding so as to deliver the entire C1-C26 fragment of PTX2.