In the course of the synthetic studies on gymnodimine, a potent shellfish toxin, the asymmetric construction of the azaspirocyclic part was achieved by the (-)-siam·Cu(SbF6)2 complex catalyzed intermolecular Diels-Alder reaction in high exo- and enantioselectivities.
Total Synthesis of (−)-Zampanolide and Questionable Existence of (−)-Dactylolide as the Elusive Biosynthetic Precursor of (−)-Zampanolide in an Okinawan Sponge
作者:Jun’ichi Uenishi、Takuya Iwamoto、Junichi Tanaka
DOI:10.1021/ol901167g
日期:2009.8.6
concise totalsynthesis of (−)-zampanolide, (−)-1, and (−)-dactylolide, (−)-2, is described. Synthetic highlights include (i) a mild Horner-Wadsworth-Emmons reaction providing the seco acid, (ii) an unusual stepwise cross-coupling reaction of a 1,1-dibromodiene with inversion of olefin geometry, and (iii) specific O-Michael reaction conditions using catalytic LHMDS with TMEDA for the synthesis of functionalized
Studies on the Mechanism of B(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>-Catalyzed Hydrostannylation of Propargylic Alcohol Derivatives
作者:Martins S. Oderinde、Michael G. Organ
DOI:10.1002/anie.201204060
日期:2012.9.24
Sleight of hydride: B(C6F5)3 catalyzes the hydrostannylation of propargylicalcohols in a regio‐ and stereoselective manner (see scheme). This Lewis acid first abstracts a hydride from the stannane, thus forming a borohydride/stannyl cation pair, the stability of which depends on solvent and ligands. Deuterium‐labeling experiments showed that the source that delivers a hydride to the alkenyl cation
氢化物的轻度:B(C 6 F 5)3以区域和立体选择性的方式催化炔丙醇的加氢甲锡化反应(参见方案)。该路易斯酸首先从锡烷中提取氢化物,从而形成硼氢化物/锡烷基阳离子对,其稳定性取决于溶剂和配体。氘标记实验表明,将氢化物传递至烯基阳离子的来源不是硼氢化物,而是锡烷的第二分子。
Total Synthesis of (-)-Austalide B. A Generic Solution to Elaboration of the Pyran/p-Cresol/Butenolide Triad
作者:Leo A. Paquette、Ting-Zhong Wang、Matthew R. Sivik
DOI:10.1021/ja00104a012
日期:1994.12
The toxic meroterpenoid (-)-austalide B has been prepared in its natural form by chemical modification of the readily available optically active enedione 11. Following stereocontrolled Robinson annulation to give 13 and fully regiocontrolled gem-dimethylation of this intermediate, the highly functionalized tetracyclic ortho ester 22 was produced in four additional steps. At this point, it proved an easy matter to obtain 23 by Baeyer-Villiger oxidation. For the purpose of annealing rings E and F, carbomethoxy trinate 41 was prepared and coupled to 42 through the agency of Pd-2(dba)(3) and (furyl)(3)P. With arrival at 39, it proved possible by sequential intramolecular Claisen condensation, O-methylation, and modest warming to produce 50. Deprotection of the secondary hydroxyl and inversion of its configuration delivered synthetic austalide B, which exhibited melting point, specific rotation, infrared, and NMR properties (H-1 and C-13) identical to the natural material obtained from South Africa.
Transannular Diels-Alder route to systems related to dynemicin A
作者:John A. Porco、Frank J. Schoenen、Thomas J. Stout、Jon Clardy、Stuart L. Schreiber