据报道,钯催化的 dl-和内消旋 1,2-二乙烯基亚乙基碳酸酯的 1:1 混合物的不对称烯丙基烷基化。这是第一次,催化循环的电离和亲核加成步骤都作为对映体区分步骤,以产生高对映体过量的单一产物。反应以> 98% ee 进行以有效地从丙烯醛生成有用的手性构件。iso-cladospolide B 和 11-epi-iso-cladospolide B 的绝对和相对构型通过全合成验证,解决了文献中的明显差异。
An enantio- and stereo-controlled synthesis of<scp>L</scp>-erythro- and<scp>D</scp>-threo-C<sub>18</sub>-sphingosines via the anomalous version of the katsuki–sharpless asymmetric epoxidation reaction
A new enantiocontrolled synthesis of L-erythro- and D-threo-sphingosines has been established starting from (R,R)- and meso-1,2-divinylethylene glycols via the anomalous version of the KatsukiâSharpless asymmetric epoxidation reaction as the key step.
Protecting-Group-Free Route to Hydroxylated Pyrrolidine and Piperidine Derivatives through Cu(I)-Catalyzed Intramolecular Hydroamination of Alkenes
作者:Masaya Sawamura、Hirohisa Ohmiya、Mika Yoshida
DOI:10.1055/s-0030-1258527
日期:2010.9
An efficient approach to hydroxylated pyrrolidine and piperidinederivatives through the intramolecular hydroamination catalyzed by a Cu(I)-Xantphos system is described. The transformation allows for the short synthesis of N-alkylated aza-sugars without a protection-deprotection event of the hydroxy groups.
A new synthesis to bis-butenolide derivatives from inexpensive divinylglycol is described, employing a sequential double acylation followed by a double ring-closing metathesis. The selectivity is affected by the choice of catalyst.
Double asymmetric iodoamination; synthesis of C 2 symmetric and meso-amino alcohols
作者:Sung Ho Kang、Do Hyun Ryu
DOI:10.1039/cc9960000355
日期:——
Alkenic diols 2 and 14 are iodocyclized providing dihydro-1,3-oxazine 3 and dihydrooxazole 15 in 90 and 93% de, respectively, which are precursors of various C2 symmetric and meso-amino alcohols.
Ex‐changing places: A highlyenantioselectivedesymmetrization of 1,2‐diols has been developed in which the catalyst utilizes reversible covalent bonding to the substrate to achieve both high selectivity and rate acceleration (see scheme, PMP=pentalmethylpiperidine, TBS=tert‐butyldimethylsilyl). Induced intramolecularity is responsible for the enhanced rate, thus allowing the reaction to be performed at