Diosphenol-Based Approach to the A-Ring Functionalization of Advanced Taxol Precursors

Abstract

Several different approaches to the A-ring functionalization of an advanced, highly functionalized diosphenol precursor to Taxol are described. The first phase of the undertaking consists of an assessment of those reagents conducive to reaction at the enolic oxygen (silylation, methylation, allylation, and acylation). Transformations involving an alternative attack at the enol carbon center (bromination, selenation) have also been defined. Sodium borohydride reduction operates from the beta-face of C-14 as long as the C-1 hydroxyl is not protected so as to offer steric exclusion. Complications associated with various aspects of these methodological undertakings are addressed. The most advanced oxygenation achievements were realized by way of a noteworthy sequence involving epoxidation of the O-methyl ether, methanolysis under mildly acidic conditions, and regioselective oxidation of diol 38 to give 39.

Research Progress in the Environmentally-Friendly Michael Addition

“…通过硒杂 Michael 加成反应形成 C-Se 键的传统方 法是以苯硒酚为底物, 但反应对空气敏感, 易挥发, 具 有很严重的环境和安全问题 [89] . 而 β-硒羰基化合物是重 要的合成子, 可以作为中间体合成紫杉醇 [90] 、洛伐他 汀 [91] 、1,2,4-三取代-1,2,5,6-四氢吡啶 [92] 等. Perin 等 …”

Biogenetic-type Synthesis of 2-Hydroxy-4,4,7-trimethyl-1(4H)-naphthalenone, a Modified Apocarotenoid from Ipomoea pes-caprae

“…However, in the second method we could get almost quantitative yield of 1 when the tetralone 3 was directly oxidized using Barton oxidation. This reaction, though previously reported [19,20], was optimized by purging oxygen through a solution of potassium t-butoxide and the tetralone 3 in dry THF at room temperature for 30 min to give 1 in 98% yield. The structure of synthetic 1 was confirmed by comparison of its MP and spectral data (IR, 1 H-and 13 C NMR, EI-MS) which are in good agreement with the corresponding reported data [3,4].…”