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?-C-H Mono- and Dihalogenation of Alcohols.

ABSTRACT: Alkoxy radicals have long been known to enable remote C-H functionalization via 1,5-hydrogen atom abstraction. However, methods for their generation traditionally have relied upon highly oxidizing metals, ultraviolet radiation, or preformed peroxide intermediates, which has prevented the development of many desirable transformations. Herein we report a new bench-stable precursor that decomposes to free alkoxy radicals via a previously unreported single-electron oxidation pathway. This new precursor enables the fluorination and chlorination of remote C-H bonds under exceptionally mild conditions with exceedingly high monoselectivity. Iterative use of this precursor enables the introduction of a second halogen atom, granting access to remote dihalide motifs, including CF₂ and CFCl.

SUBMITTER: Herron AN

PROVIDER: S-EPMC7266640 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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δ-C-H Mono- and Dihalogenation of Alcohols.

Herron Alastair N AN Liu Dongxin D Xia Guoqin G Yu Jin-Quan JQ

Journal of the American Chemical Society 20200130 6

Alkoxy radicals have long been known to enable remote C-H functionalization via 1,5-hydrogen atom abstraction. However, methods for their generation traditionally have relied upon highly oxidizing metals, ultraviolet radiation, or preformed peroxide intermediates, which has prevented the development of many desirable transformations. Herein we report a new bench-stable precursor that decomposes to free alkoxy radicals via a previously unreported single-electron oxidation pathway. This new precur ...[more]

PMID: 31999441

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Project description:Plasmodium falciparum is the etiological agent of human malaria, one of the most widespread diseases in tropical and subtropical world regions. One of the biggest problems in controlling the disease is the emergence of drug resistance, which leads to the need to discover new antimalarial compounds. One of the most promissory drugs purposed is fosmidomycin, an inhibitor of the biosynthesis of isoprene units by the methylerythritol 4-phosphate (MEP) pathway which in some cases failed in clinic studies. Once formed, isoprene units are condensed to form longer structures such as farnesyl and geranylgeranyl pyrophosphate (GGPP), which are necessary for heme O and A formation, ubiquinone, and dolichyl phosphate biosynthesis as well as for protein isoprenylation. Even though the natural substrates of polyprenyl transferases and syntheses are polyprenyl pyrophosphates, it was already demonstrated that isoprenoid alcohols (polyprenols) such as farnesol (FOH) and geranylgeraniol (GGOH) can rescue parasites from fosmidomycin. This study better investigated how this rescue phenomenon occurs by performing drug-rescue assays. By this, it was observed that phytol (POH), a 20-carbon plant isoprenoid, rescues parasites from the fosmidomycin effect, similarly to FOH or GGOH. Contrarily, neither dolichols nor nonaprenol rescue parasites from fosmidomycin. Considering this, here we characterized the transport of FOH, GGOH, and POH. Once incorporated, it was observed that these substances are phosphorylated, condensed into longer isoprenoid alcohols, and incorporated into proteins and dolichyl phosphates. Through proteomic and radiolabelling approaches, it was found that prenylated proteins are naturally attached to several isoprenoids including GGOH, dolichol, and POH if exogenously added. Furthermore, results suggest the presence of at least two promiscuous protein prenyltransferases in the parasite: one enzyme which can use FPP among other unidentified substrates and another enzyme that can use GGOH, POH, and dolichols among other substrates not identified here. Thus, was obtained further evidence for dolichols and other isoprenoid products attached to proteins. This study helps better understand apicoplast-targeting antimalarials mechanism of action as well as novel posttranslational modifications of proteins.

Dataset Information

?-C-H Mono- and Dihalogenation of Alcohols.

Publications

δ-C-H Mono- and Dihalogenation of Alcohols.

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