RESUMO
Dimethylthiocarbamates (DMTCs), prepared from the corresponding alcohols using commercial dimethylthiocarbamoyl chloride, are spectrally simple, achiral, and nonpolar. DMTCs are moderately to highly stable to a wide range of reagents and conditions including metal hydrides, hydroboration, ylides, NaOH, HCl, organolithiums, Grignards, DDQ, PCC, Swern, n-Bu(4)NF, CrCl(2), heat, and Lewis acids. They are readily removed by NaIO(4) or H(2)O(2) in the presence of other common alcohol protecting groups. [structure: see text]
Assuntos
Álcoois/química , Tiocarbamatos/química , Estrutura MolecularRESUMO
Addition of Zn(n-Bu(3)Sn)(2) to prochiral aldehydes affords anti-alpha,beta-dialkoxy- and anti-alpha-alkoxy-beta-aminostannanes in good yield (up to 77%) and excellent diastereoselectivity (up to 98% de). syn-Isomers are accessed from the initial adducts via Mitsunobu inversion/saponification. The corresponding thionocarbamates undergo mild Cu(I)-mediated cross-coupling with a variety of organic halides, inter alia, allylic, cinnamylic, propargylic, and acetylenic, with retention of configuration. [reaction: see text]
Assuntos
Cobre/química , Compostos Orgânicos de Estanho/síntese química , Estrutura Molecular , EstereoisomerismoRESUMO
(Z)-alpha-Fluoro-, (Z)-alpha-chloro-, and (Z)-alpha-bromoacrylates were obtained with unprecedented yield and stereocontrol (>99%) via addition of the corresponding commercial trihaloacetates to aldehydes at room temperature using stoichiometric Cr(II) salts or catalytic Cr(II) with a regeneration system. The intermediate 2,2-dihalo-3-hydroxy adducts could be isolated in good yields under conditions of limited reagent at 0 degrees C.
Assuntos
Acetatos/química , Acrilatos/síntese química , Aldeídos/química , Alcenos/síntese química , Cromo/química , Hidrocarbonetos Halogenados/síntese química , Hidrocarbonetos Halogenados/química , EstereoisomerismoRESUMO
BIBR 1532 has been reported to be a potent, small molecule inhibitor of human telomerase, suggesting it as a lead for the development of anti-telomerase therapy. We confirm the ability of BIBR 1532 to inhibit telomerase and report the discovery of an equally potent analogue. Importantly, IC(50) values in cell extract are considerably higher than those previously reported using assays for purified enzyme, indicating that substantial improvement may be necessary.
Assuntos
Aminobenzoatos , Inibidores Enzimáticos/farmacologia , Naftalenos , Telomerase/antagonistas & inibidores , Desenho de Fármacos , Inibidores Enzimáticos/síntese química , Amplificação de Genes , Células HeLa , Humanos , Indicadores e Reagentes , Relação Estrutura-Atividade , Telomerase/genéticaRESUMO
A variety of 3-substituted furans, including the natural products perillene and dendrolasin, are obtained in good yield via reductive annulation of 1,1,1-trichloroethyl propargyl ethers using catalytic Cr(II) regenerated by Mn/TMSCl. [reaction: see text]
Assuntos
Furanos/síntese química , Monoterpenos , Monoterpenos Acíclicos , Alquilação , Cloretos , Compostos de Cromo , Indicadores e ReagentesRESUMO
(Z)-2-Chloroalk-2-en-1-ols are obtained in excellent yields from a wide variety of aldehydes by addition of (E)-chromium vinylidene carbenoids, stereospecifically generated from trichloroalkanes using CrCl(2) in THF at room temperature. [reaction: see text]
Assuntos
Álcoois/síntese química , Cromo/química , Metano/análogos & derivados , Metano/síntese química , Compostos de Vinila/química , Álcoois/química , Hidrocarbonetos , Metano/químicaRESUMO
[reaction: see text] A wide spectrum of alcohols and phenols are readily transformed to the corresponding 2-tetrahydrofuranyl ethers in good to excellent yields using CrCl2 and CCl4 in THF under nearly neutral conditions at room temperature.