Browsing by Author "Gao, Hongyin"

Now showing 1 - 6 of 6
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    Amination and hydroxylation of arylmetal compounds
    (2019-12-03) Gao, Hongyin; Zhou, Zhe; Kurti, Laszlo; Rice University; United States Patent and Trademark Office
    In one aspect, the present disclosure provides methods of preparing a primary or secondary amine and hydroxylated aromatic compounds. In some embodiments, the aromatic compound may be unsubstituted, substituted, or contain one or more heteroatoms within the rings of the aromatic compound. The methods described herein may be carried out without the need for transition metal catalysts or harsh reaction conditions.
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    Antimicrobial activity of a natural compound and analogs against multi-drug-resistant Gram-positive pathogens
    (American Society for Microbiology, 2024) Shah, Kush N.; Shah, Parth N.; Agobe, Francesca O.; Lovato, Kaitlyn; Gao, Hongyin; Ogun, Oluwadara; Hoffman, Cason; Yabe-Gill, Marium; Chen, Qingquan; Sweatt, Jordan; Chirra, Bhagath; Muñoz-Medina, Ricardo; Farmer, Delaney E.; Kürti, László; Cannon, Carolyn L.
    The increasing prevalence of methicillin-resistant Staphylococcus aureus (MRSA) has sparked global concern due to the dwindling availability of effective antibiotics. To increase our treatment options, researchers have investigated naturally occurring antimicrobial compounds and have identified MC21-A (C58), which has potent antimicrobial activity against MRSA. Recently, we have devised total synthesis schemes for C58 and its chloro-analog, C59. Here, we report that both compounds eradicate 90% of the 39 MRSA isolates tested [MIC90 and minimum bactericidal concentration (MBC90)] at lower or comparable concentrations compared to several standard-of-care (SoC) antimicrobials including daptomycin, vancomycin, and linezolid. Furthermore, a stable, water-soluble sodium salt of C59, C59Na, demonstrates antimicrobial activity comparable to C59. C59, unlike vancomycin, kills stationary-phase MRSA in a dose-dependent manner and completely eradicates MRSA biofilms. In contrast to vancomycin, exposing MRSA to sub-MIC concentrations of C59 does not result in the emergence of spontaneous resistance. Similarly, in a multi-step study, C59 demonstrates a low propensity of resistance acquisition when compared to SoC antimicrobials, such as linezolid and clindamycin. Our findings suggest C58, C59, and C59Na are non-toxic to mammalian cells at concentrations that exert antimicrobial activity; the lethal dose at median cell viability (LD50) is at least fivefold higher than the MBC90 in the two mammalian cell lines tested. A morphological examination of the effects of C59 on a MRSA isolate suggests the inhibition of the cell division process as a mechanism of action. Our results demonstrate the potential of this naturally occurring compound and its analogs as non-toxic next-generation antimicrobials to combat MRSA infections
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    Non-Deprotonative Primary and Secondary Amination of (Hetero)Arylmetals
    (American Chemical Society, 2017) Zhou, Zhe; Ma, Zhiwei; Behnke, Nicole Erin; Gao, Hongyin; Kürti, László; BioScience Research Collaborative
    Herein we disclose a novel method for the facile transfer of primary (−NH2) and secondary amino groups (−NHR) to heteroaryl- as well as arylcuprates at low temperature without the need for precious metal catalysts, ligands, excess reagents, protecting and/or directing groups. This one-pot transformation allows unprecedented functional group tolerance and it is well-suited for the amination of electron-rich, electron-deficient as well as structurally complex (hetero)arylmetals. In some of the cases, only catalytic amounts of a copper(I) salt is required.
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    Practical Organocatalytic Synthesis of Functionalized Non-C2-Symmetrical Atropisomeric Biaryls
    (Wiley, 2016) Gao, Hongyin; Xu, Qing-Long; Keene, Craig; Yousufuddin, Muhammed; Ess, Daniel H.; Kürti, László
    An organic acid catalyzed direct arylation of aromatic C(sp2)H bonds in phenols and naphthols for the preparation of 1,1′-linked functionalized biaryls was developed. The products are non-C2-symmetrical, atropoisomeric, and represent previously untapped chemical space. Overall this transformation is operationally simple, does not require an external oxidant, is readily scaled up (up to 98 mmol), and the structurally diverse 2,2′-dihydroxy biaryl (i.e., BINOL-type), as well as 2-amino-2′-hydroxy products (i.e., NOBIN-type) are formed with complete regioselectivity. Density-functional calculations suggest that the quinone and imino-quinone monoacetal coupling partners are exclusively arylated at their α-position by an asynchronous [3,3]-sigmatropic rearrangement of a mixed acetal species which is formed in situ under the reaction conditions.
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    Rapid heteroatom transfer to arylmetals utilizing multifunctional reagent scaffolds
    (Springer Nature, 2016) Gao, Hongyin; Zhou, Zhe; Kwon, Doo-Hyun; Coombs, James; Jones, Steven; Behnke, Nicole Erin; Ess, Daniel H.; Kürti, László; BioScience Research Collaborative
    Arylmetals are highly valuable carbon nucleophiles that are readily and inexpensively prepared from aryl halides or arenes and widely used on both laboratory and industrial scales to react directly with a wide range of electrophiles. Although C−C bond formation has been a staple of organic synthesis, the direct transfer of primary amino (−NH2) and hydroxyl (−OH) groups to arylmetals in a scalable and environmentally friendly fashion remains a formidable synthetic challenge because of the absence of suitable heteroatom-transfer reagents. Here, we demonstrate the use of bench-stable N−H and N−alkyl oxaziridines derived from readily available terpenoid scaffolds as efficient multifunctional reagents for the direct primary amination and hydroxylation of structurally diverse aryl- and heteroarylmetals. This practical and scalable method provides one-step synthetic access to primary anilines and phenols at low temperature and avoids the use of transition-metal catalysts, ligands and additives, nitrogen-protecting groups, excess reagents and harsh workup conditions.
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    Transition metal-free direct dehydrogenative arylation of activated C(sp3)–H bonds: synthetic ambit and DFT reactivity predictions
    (Royal Society of Chemistry, 2018) Lovato, Kaitlyn; Guo, Lirong; Xu, Qing-Long; Liu, Fengting; Yousufuddin, Muhammed; Ess, Daniel H.; Kürti, László; Gao, Hongyin
    A transition metal-free dehydrogenative method for the direct mono-arylation of a wide range of activated C(sp3)-H bonds has been developed. This operationally simple and environmentally friendly aerobic arylation uses tert-BuOK as the base and nitroarenes as electrophiles to prepare up to gram quantities of structurally diverse sets (>60 examples) of α-arylated esters, amides, nitriles, sulfones and triaryl methanes. DFT calculations provided a predictive model, which states that substrates containing a C(sp3)-H bond with a sufficiently low pK a value should readily undergo arylation. The DFT prediction was confirmed through experimental testing of nearly a dozen substrates containing activated C(sp3)-H bonds. This arylation method was also used in a one-pot protocol to synthesize over twenty compounds containing all-carbon quaternary centers.