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

The Huisgen 1,3-dipolar cycloaddition reaction of organic azides and alkynes has gained considerable attention in recent years due to the introduction in 2001 of Cu(1) catalysis by Tornoe and Meldal, leading to a major improvement in both rate and regioselectivity of the reaction, as realized independently by the Meldal and the Sharpless laboratories. The great success of the Cu(1) catalyzed reaction is rooted in the fact that it is a virtually quantitative, very robust, insensitive, general, and orthogonal ligation reaction, suitable for even biomolecular ligation and in vivo tagging or as a polymerization reaction for synthesis of long linear polymers. The triazole formed is essentially chemically inert to reactive conditions, e.g. oxidation, reduction, and hydrolysis, and has an intermediate polarity with a dipolar moment of ∼5 D. The basis for the unique properties and rate enhancement for triazole formation under Cu(1) catalysis should be found in the high ∆G of the reaction in combination with the low character of polarity of the dipole of the noncatalyzed thermal reaction, which leads to a considerable activation barrier. In order to understand the reaction in detail, it therefore seems important to spend a moment to consider the structural and mechanistic aspects of the catalysis. The reaction is quite insensitive to reaction conditions as long as Cu(1) is present and may be performed in an aqueous or organic environment both in solution and on solid support.

Cu-catalyzed azide-alkyne cycloaddition.

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

Functionalizing traditionally inert carbon–hydrogen bonds represents a powerful transformation in organic synthesis, providing new entries to valuable structural motifs and improving the overall synthetic efficiency. C–H bond activation, however, often necessitates harsh reaction conditions that result in functional group incompatibilities and limited substrate scope. An understanding of the reaction mechanism and rational design of experimental conditions have led to significant improvement in both selectivity and applicability. This critical review summarizes and discusses endeavours towards the development of mild C–H activation methods and wishes to trigger more research towards this goal. In addition, we examine select examples in complex natural product synthesis to demonstrate the synthetic utility of mild C–H functionalization (84 references).

Towards mild metal-catalyzed C–H bond activation

C-H bonds are ubiquitous in organic compounds. It would, therefore, appear that direct functionalization of substrates by activation of C-H bonds would eliminate the multiple steps and limitations associated with the preparation of functionalized starting materials. Regioselectivity is an important issue because organic molecules can contain a wide variety of C-H bonds. The use of a directing group can largely overcome the issue of regiocontrol by allowing the catalyst to come into proximity with the targeted C-H bonds. A wide variety of functional groups have been evaluated for use as directing groups in the transformation of C-H bonds. In 2005, Daugulis reported the arylation of unactivated C(sp(3))-H bonds by using 8-aminoquinoline and picolinamide as bidentate directing groups, with Pd(OAc)2 as the catalyst. Encouraged by these promising results, a number of transformations of C-H bonds have since been developed by using systems based on bidentate directing groups. In this Review, recent advances in this area are discussed.

Catalytic Functionalization of C(sp2) ? H and C(sp3) ? H Bonds by Using Bidentate Directing Groups

The present invention provides isolated homogeneous polyfunctionalized proteins (e.g., erythropoietin), isolated glycopeptides, and a method for preparing polyfunctionalized peptides and/or proteins via cysteine-free native chemical ligation. In certain embodiments, the invention provides an isolated homogeneous polyfunctionalized protein having the structure (I). In certain other embodiments, the invention provides an isolated glycopeptide having Formula (II). In certain other embodiments, the inventive method is a method for preparing a polyfunctionalized peptide comprising a peptidic backbone made up of four or more amino acids, wherein two or more non-adjacent amino acids are independently substituted with a moiety having the structure (III) -LH. wherein A and L1 are as defined herein.

Homogeneous erythropoietin and other peptides and proteins, methods and intermediates for their preparation

Provided are methods and compositions from reprogramming human glial cells into human neurons. The reprogramming is achieved using combinations of compounds that can modify signaling via Transforming growth factor beta (TGF-β), Bone morphogenetic protein (BMP), glycogen synthase kinase 3 (GSK-3), and γ-secretase/Notch pathways. The reprogramming is demonstrated using groups of three or four compounds that are chosen from the group thiazovivin, LDN193189, SB431542, TTNPB, CHIR99021, DAPT, VPA, SAG, purmorphamine. Reprogramming is demonstrated using the group of LDN193189/CHIR99021/DAPT, the group of B431542/CHIR99021/DAPT, the group of LDN193189/DAPT/SB431542, the group of LDN193189/CHIR99021/SB431542, a three drug combination of SB431542/CHIR99021/DAPT. Reprogramming using functional analogs of the compounds is also provided, as are pharmaceutical formulations that contain the drug combinations.

Chemical reprogramming of human glial cells into neurons for brain and spinal cord repair

A new palladium-catalyzed picolinamide (PA)-directed ortho-iodination reaction of e-C(sp(2))-H bonds of γ-arylpropylamine substrates is reported. This reaction proceeds selectively with a variety of γ-arylpropylamines bearing strongly electron-donating or withdrawing substituents, complementing our previously reported PA-directed electrophilic aromatic substitution approach to this transformation. As demonstrated herein, a three step sequence of Pd-catalyzed γ-C(sp(3))-H arylation, Pd-catalyzed e-C(sp(2))-H iodination, and Cu-catalyzed C-N cyclization enables a streamlined synthesis of tetrahydroquinolines bearing diverse substitution patterns.

https://www.beilstein-journals.org/bjoc/content/pdf/1860-5397-12-119.pdf

Palladium-catalyzed picolinamide-directed iodination of remote ortho-C−H bonds of arenes: Synthesis of tetrahydroquinolines

A versatile Cu-catalyzed direct ortho-C(sp2)-H amination of benzamides and picolinamides with alkylamines has been achieved. This method employs cheap and eco-friendly copper as a catalyst and oxygen as an oxidant, and also has the advantages of straightforward steps and excellent functional group compatibility. Further application of our approach was demonstrated by the synthesis of TCMDC-125116, SPHINX, and SRPIN340.

Copper-catalyzed ortho-C(sp2)-H amination of benzamides and picolinamides with alkylamines using oxygen as a green oxidant.

P–N and P=N bonds play important roles in the design and synthesis of functional molecules such as bioactive compounds and organic ligands for catalysis. Existing methods for P–N coupling mostly re...

https://www.chinesechemsoc.org/doi/pdf/10.31635/ccschem.021.202101056

Gong Chen

Papers

Homogeneous erythropoietin and other peptides and proteins, methods and intermediates for their preparation

Chemical reprogramming of human glial cells into neurons for brain and spinal cord repair

Palladium-catalyzed picolinamide-directed iodination of remote ortho-C−H bonds of arenes: Synthesis of tetrahydroquinolines

Copper-catalyzed ortho-C(sp2)-H amination of benzamides and picolinamides with alkylamines using oxygen as a green oxidant.

Nitrene-Mediated P–N Coupling Under Iron Catalysis