the catalyst which bears an imidazol-2-ylidene ligand. The EIZ ratio obtained in this macrocyclizationreaction was determined by the protecting groups at the remote phenolic OH group of the cyclization precursor. The elaboration of the resulting cycloalkene 37 into the final target involved a CrCl2-mediated synthesis of vinyliodide 49 which, after deprotection, did undergo a copper-catalyzed cross-coupling
A range of double unsaturated amides (15, 19, and 21), obtained by cross-coupling reactions was reacted with aldehydes to hemiaminals. Heating the hemiaminals in the presence of Ac2O and pyridine affected clean conversion to the corresponding enamides, such as 42, 45, and 47. Alternatively, N,S-acetals were prepared which were oxidized to the sulfones. Treatment with base also gave the enamides, favoring
alcohols can be oxidised with activated manganese dioxide in the presence of stabilised Wittig reagents to generate α,β-unsaturated esters directly. This simple procedure, which can also be utilised with diols to give double homologation, is generally useful and particularly valuable if the intermediate aldehydes are difficult to isolate, toxic or prone to isomerisation.
Synthesis and Cytotoxicity of a Salicylihalamide A Analogue
作者:Shaoshan Tang、Karen L. Erickson
DOI:10.1021/np070694q
日期:2008.5.1
The synthesis of a simple analogue of salicylibalamide A with a truncated lactone ring (2) was achieved in 10 steps. Its cytotoxicity profile in the NCI 60-cell-line human tumor assay differed significantly from that of salicylihalamide A in both level and specificity.
DMP-mediated one-pot oxidative olefination of silyl ethers
作者:Guisheng Deng、Baihua Xu、Chunyu Liu
DOI:10.1016/j.tet.2005.04.021
日期:2005.6
Silyl ethers of arylic, allylic, propargylic and unactivated alcohols could be deprotected and oxidized with Dess-Martin periodinane, and the resulting aldehydes could be directly converted to the corresponding alpha,beta-unsaturated esters in one pot with stabilized phosphoranes. Good selectivities were achieved upon a variety of protecting groups of alcohol by using this method. Other advantages of the protocol included simplicity of operations and high efficiency, as well as good to excellent yields. (c) 2005 Elsevier Ltd. All rights reserved.