抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

The direct functionalization of C-H bonds in organic compounds has recently emerged as a powerful and ideal method for the formation of carbon-carbon and carbon-heteroatom bonds. This Review provides an overview of C-H bond functionalization strategies for the rapid synthesis of biologically active compounds such as natural products and pharmaceutical targets.

C-H bond functionalization: emerging synthetic tools for natural products and pharmaceuticals

In the investigation of efficient chemical transformations, the carbon-carbon bond-forming reactions play an outstanding role. In this context, organocatalytic processes have achieved considerable attention. 1 Beside their facile reaction course, selectivity, and environmental friendliness, new synthetic strategies are made possible. Particularly, the inversion of the classical reactivity (Umpolung) opens up new synthetic pathways. 2 In nature, the coenzyme thiamine (vitamin B1), a natural thiazolium salt, utilizes a catalytic variant of this concept in biochemical processes as nucleophilic acylations. 3 The catalytically active species is a nucleophilic carbene. 4

Organocatalysis by N-Heterocyclic Carbenes

Asymmetric enamine catalysis.

We describe a single-step conversion of various N-vinyl and N-aryl amides to the corresponding pyridine and quinoline derivatives, respectively. The process involves amide activation with trifluoromethanesulfonic anhydride in the presence of 2-chloropyridine followed by π-nucleophile addition to the activated intermediate and annulation. Compatibility of this chemistry with sensitive N-vinyl amides, epimerizable substrates, and a variety of functional groups is noteworthy.

Direct synthesis of pyridine derivatives.

The fungal metabolite (+)-11,11'-dideoxyverticillin A, a cytotoxic alkaloid isolated from a marine Penicillium sp., belongs to a fascinating family of densely functionalized, stereochemically complex, and intricate dimeric epidithiodiketopiperazine natural products. Although the dimeric epidithiodiketopiperazines have been known for nearly 4 decades, none has succumbed to total synthesis. We report a concise enantioselective total synthesis of (+)-11,11'-dideoxyverticillin A via a strategy inspired by our biosynthetic hypothesis for this alkaloid. Highly stereo- and chemoselective advanced-stage tetrahydroxylation and tetrathiolation reactions, as well as a mild strategy for the introduction of the epidithiodiketopiperazine core in the final step, were developed to address this highly sensitive substructure. Our rapid functionalization of the advanced molecular framework aims to mimic plausible biosynthetic steps and offers an effective strategy for the chemical synthesis of other members of this family of alkaloids.

https://science.sciencemag.org/content/sci/324/5924/238.full.pdf

Total synthesis of (+)-11,11'-dideoxyverticillin A.

meta-C–H olefination, arylation, and acetoxylation of indolines have been developed using nitrile-containing templates. The combination of a monoprotected amino acid ligand and the nitrile template attached at the indolinyl nitrogen via a sulfonamide linkage is crucial for the meta-selective C–H functionalization of electron-rich indolines that are otherwise highly reactive toward electrophilic palladation at the para-positions. A wide range of synthetically important and advanced indoline analogues are selectively functionalized at the meta-positions.

Pd(II)-catalyzed meta-C-H olefination, arylation, and acetoxylation of indolines using a U-shaped template

N-heterocyclic carbene-catalyzed amidation of unactivated esters with amino alcohols.

We describe a two-step conversion of various N-vinyl and N-aryl amides to the corresponding substituted pyridines and quinolines, respectively. The process involves the direct conversion of amides, including sensitive N-vinyl amides, to the corresponding trimethylsilyl alkynyl imines followed by a ruthenium-catalyzed protodesilylation and cycloisomerization. A wide range of new alkynyl imines are prepared and readily converted to the corresponding azaheterocycles.

Mohammad Movassaghi

Papers

Direct synthesis of pyridine derivatives.

Total synthesis of (+)-11,11'-dideoxyverticillin A.

Pd(II)-catalyzed meta-C-H olefination, arylation, and acetoxylation of indolines using a U-shaped template

N-heterocyclic carbene-catalyzed amidation of unactivated esters with amino alcohols.

Synthesis of Substituted Pyridine Derivatives via the Ruthenium-Catalyzed Cycloisomerization of 3-Azadienynes