Reactions of some ortho and para halogenated aromatic nitriles with ethylenediamine: selective synthesis of imidazolines

The reaction of ethylenediamine (EDA) with ortho and/or para halogenated benzonitriles did not lead to the imidazolines expected: a competitive aromatic nucleophilic substitution (S_NAr) was observed instead. The selective synthesis of these imidazolines was performed by nucleophilic addition of EDA to thiobenzamide derivatives. The difference in reactivity between the nitrile and thioamide derivatives was estimated by a frontier orbital approach at the RHF/6-31G** level which predicted a greater reactivity of substituted thiobenzamides towards the nucleophilic addition of EDA.     

Deprotonation of cationic tungsten(IV) aqua-oxo-alkyne complexes to form dioxo-vinyl tungsten(VI) complexes

Chiral tungsten(IV) aqua-oxo-alkyne complexes, [Tp'W(O)(H2O)(RC identical to CR)][OTf] (R = H (1); R = Me (2)); (Tp' = hydridotris(3,5-dimethylpyrazolyl)borate; OTf = trifluoromethanesulfonate), have been prepared by halide abstraction from iodide precursors. These cationic complexes have been characterized with triflate as the counteranion. The tautomeric dihydroxo isomer has not been observed. The neutral triflate adduct Tp'W(O)(OTf)(HC identical to CH) (3) has also been isolated. Cationic complexes 1 and 2 undergo deprotonation and isomerization when exposed to Al2O3 to give the dioxo-vinyl compounds Tp'W(O)2(CH=CH2) (6) and Tp'W(O)2[C(Me)=C(H)(Me)] (7), reflecting the conversion of the WIV(OH)(RC identical to CR) fragment to WVI(=O)(RC=CHR). The presumed intermediates, neutral oxo-hydroxo compounds Tp'W(O)(OH)(RC identical to CR) (R = H (9); R = Me (10)), can be accessed by deprotonation of 1 or 2 with NaOH. Conversion of 9 to 6 was achieved thermally upon heating at 100 degrees C for 2 days. X-ray structural data have provided solid-state structures of both the cationic aqua complex 2 and the dioxo-vinyl complex 6.     

5-甲基-[(2E,6E)-3,7,11-三甲基-9-氧代十二碳二烯]苯醌和氢醌的首次全合成

以2-甲基对苯二酚和香叶基溴为起始原料, 经过酚羟基保护, 溴代, Li₂CuCl₄催化的芳基溴与Grignard试剂的偶联以及Julia偶联等一系列反应, 完成了裸鳃亚动物的代谢产物, 5-甲基-[(2E,6E)-3,7,11-三甲基-9-氧代十二碳二烯]苯醌(1)和氢醌(2)的首次全合成, 将1用NaBH₄还原, 得到(±)-3, (±)-3也是此类天然产物之一.     

Capturing Biological Activity in Natural Product Fragments by Chemical Synthesis

Natural products have had an immense influence on science and have directly led to the introduction of many drugs. Organic chemistry, and its unique ability to tailor natural products through synthesis, provides an extraordinary approach to unlock the full potential of natural products. In this Review, an approach based on natural product derived fragments is presented that can successfully address some of the current challenges in drug discovery. These fragments often display significantly reduced molecular weights, reduced structural complexity, a reduced number of synthetic steps, while retaining or even improving key biological parameters such as potency or selectivity. Examples from various stages of the drug development process up to the clinic are presented. In addition, this process can be leveraged by recent developments such as genome mining, antibody–drug conjugates, and computational approaches. All these concepts have the potential to identify the next generation of drug candidates inspired by natural products.     

Time-resolved dimerization of a PAS-LOV protein measured with photocoupled small angle X-ray scattering

Time-resolved small-angle X-ray scattering (SAXS) has been used to probe photoexcitation of the blue-light signal transduction protein Vivid (VVD). Laser excitation of sample in a continuous flow cell enables time-resolved measurement of the initial response of VVD to illumination. Good signal-to-noise is achieved without relying on multiple exposures of the same sample or limiting exposure times to prevent radiation damage. The SAXS data demonstrate that VVD dimerizes within tens of milliseconds of light-state activation. Time-resolved SAXS in a flow cell format is a general method for connecting chemical changes in photoreceptors to conformationally driven output signals.     

(-)-（3S, 6R）-3, 6-羟基-10-甲基十一酸及其三聚体的全合成

以廉价易得的异戊基溴为起始原料,以烯丙基二异松莰烷基硼烷参与的不对称烯丙基化反应和Yamaguchi酯化反应为关键步骤,实现了对(-)-(3S,6R)-3,6-二羟基-10-甲基十一酸(总收率27.5％)及其三聚体(总收率24.5％)的不对称全合成。