Total Synthesis of (+)-α-Onocerin in Four Steps via Four-Component Coupling and Tetracyclization Steps
作者:Yuan Mi、Jürg V. Schreiber、E. J. Corey
DOI:10.1021/ja027373f
日期:2002.9.1
rings in one step by cation-olefin tetracyclization. New and general methodology for the conversion of vinyl tert-butyldimethylsilyl ethers to vinyl triflates with retention of E or Z olefinic geometry also was utilized in the synthesis of 1. A short enantioselective synthesis of a non-C2-symmetric diastereomer of 1 is also described which uses the new methodology.
结构独特的 C2 对称四环三萜 (+)-α-橙黄素 (1) 的对映选择性合成非常短(四步,总产率为 31%)。这种机制的简洁性取决于四个片段(两个手性环氧酮分子和两个乙烯基锂分子)的组装以一步生成手性双环氧化物 4,以及所有四个碳环在一个步骤中的有效形成逐步进行阳离子-烯烃四环化。在 1 的合成中也使用了将乙烯基叔丁基二甲基甲硅烷基醚转化为乙烯基三氟甲磺酸酯的新通用方法,同时保留了 E 或 Z 烯烃几何结构。还描述了 1 的非 C2 对称非对映异构体的短对映选择性合成它使用了新的方法论。
Systematic Biases in Measured PM<sub>10</sub>Values with U.S. Environmental Protection Agency-Approved Samplers at Owens Lake, California
作者:D.M. Ono、E. Hardebeck、J. Parker、B.G. Cox
DOI:10.1080/10473289.2000.10464163
日期:2000.7
all samplers, except for a Wedding sampler that was not cleaned for the purpose of this study. On average, the TEOM and Partisol samplers agreed to within 6%, and the dichot, Graseby, and Wedding samplers measured lower PM10 concentrations by about 10, 25, and 35%, respectively. Surprisingly, the "clean" Wedding sampler consistently measured the same concentration as the "dirty" Wedding sampler through