2-(2-Pyridyl)ethylsilyl Group as a New Class of Electroauxiliary. Fine Tuning of the Electron Transfer Driven Reactions by the Dynamic Coordination to Silicon
The introduction of 2-(2-pyridyl)ethyl group on silicon decreases the oxidation potentials of silyl-substituted heteroatom compounds. The molecular orbital calculations indicate that this effect is attributed to the dynamic coordination of the pyridyl group to silicon in the cation radical intermediate. Such coordination also facilitates the selective C-Si bond cleavage.
A Formal Total Synthesis of the Sesterterpenoid (±)-Dysidiolide and Approaches to the Syntheses of (±)-6-Epi-, (±)-15-Epi-, and (±)-6,15-Bisepidysidiolide
作者:Edward Piers、Sébastien Caillé、Gang Chen
DOI:10.1021/ol0061541
日期:2000.8.1
A formal totalsynthesis of the sesterterpenoid (+/-)-dysidiolide (1), a structurally novel sponge metabolite that inhibits the cdc25A protein phosphatase, and approaches to the syntheses of (+/-)-15-epi- (34), (+/-)-6-epi- (36), and (+/-)-6, 15-bisepidysidiolide (39) are described.
An oxygenated substituent at the 2-position (taxane numbering) plays a critical role to determine the endo/exo cyclization into the 8-membered ring system involved in the taxane skeleton, and the aromatic taxinine derivative was prepared from the corresponding 2α,9β,10α–exo cyclized compound through thermal exo-to-endo isomerization and a Lewis acid induced inversion on the C-9 and C-10 sites.