Hong-Bing Liu

Bio: Hong-Bing Liu is an academic researcher from National Institutes of Health. The author has contributed to research in topics: Trigonostemon & Conformational isomerism. The author has an hindex of 16, co-authored 35 publications receiving 633 citations. Previous affiliations of Hong-Bing Liu include RMIT University & Chinese Academy of Sciences.

Phainanoids A-F, a new class of potent immunosuppressive triterpenoids with an unprecedented carbon skeleton from Phyllanthus hainanensis.

Abstract: Phainanoids A–F (1–6), six highly modified triterpenoids with a new carbon skeleton by incorporating two unique motifs of a 4,5- and a 5,5-spirocyclic systems, were isolated from Phyllanthus hainanensis. Their structures with absolute configurations were determined by spectroscopic data, chemical methods, and X-ray crystallography. Compounds 1–6 exhibited exceptionally potent immunosuppressive activities in vitro against the proliferation of T and B lymphocytes. The most potent one, phainanoid F (6), showed activities against the proliferation of T cells with IC50 value of 2.04 ± 0.01 nM (positive control CsA = 14.21 ± 0.01 nM) and B cells with IC50 value of <1.60 ± 0.01 nM (CsA = 352.87 ± 0.01 nM), which is about 7 and 221 times as active as CsA, respectively. The structure–activity relationships of 1–6 are discussed.

Recent advances in the catalytic preparation of cyclic organic carbonates

Abstract: The catalytic formation of cyclic organic carbonates (COCs) using carbon dioxide (CO2) as a renewable carbon feed stock is a highly vibrant area of research with an increasing amount of researchers focusing on this thematic investigation. These organic carbonates are highly useful building blocks and nontoxic reagents and are most commonly derived from CO2 coupling reactions with oxirane and dialcohol precursors using homogeneous catalysis methodologies. The activation of suitable reaction partners using catalysis as a key technology is a requisite for efficient CO2 conversion as its high kinetic stability poses a barrier to access functional organic molecules with added value in both academic and industrial laboratories. Although this area of science has been flourishing for at least a decade, in the past 2–3 years, significant advancements have been made to address the general reactivity and selectivity issues that are associated with the formation of COCs. Here, we present a concise overview of these a...

Enzymatic Halogenation and Dehalogenation Reactions: Pervasive and Mechanistically Diverse

Abstract: Naturally produced halogenated compounds are ubiquitous across all domains of life where they perform a multitude of biological functions and adopt a diversity of chemical structures. Accordingly, a diverse collection of enzyme catalysts to install and remove halogens from organic scaffolds has evolved in nature. Accounting for the different chemical properties of the four halogen atoms (fluorine, chlorine, bromine, and iodine) and the diversity and chemical reactivity of their organic substrates, enzymes performing biosynthetic and degradative halogenation chemistry utilize numerous mechanistic strategies involving oxidation, reduction, and substitution. Biosynthetic halogenation reactions range from simple aromatic substitutions to stereoselective C–H functionalizations on remote carbon centers and can initiate the formation of simple to complex ring structures. Dehalogenating enzymes, on the other hand, are best known for removing halogen atoms from man-made organohalogens, yet also function naturally,...

Recent Developments in the Synthesis of Cyclic Carbonates from Epoxides and CO 2

Abstract: The use of CO2 as a C1 building block will be of essential importance in the future. In this context the synthesis of cyclic carbonates from epoxides and CO2 gained great attention recently. These products are valuable compounds in a variety of chemical fields. The development of new catalysts and catalytic systems for this atom-economic, scalable, and industrially relevant reaction is a highly active research field. Over the past 17 years great advances have been made in this area of research. This chapter covers the survey of the important known classes of homogeneous catalysts for the addition of CO2 to epoxides. Besides pioneering work, recent developments and procedures that allow this transformation under mild reaction conditions (reaction temperatures of ≤100 °C and/or CO2 pressures of 0.1 MPa) are especially emphasized.

Catalytic Transformations of Functionalized Cyclic Organic Carbonates.

Abstract: Functionalized cyclic organic carbonates and related heterocycles have emerged as highly versatile heterocyclic substrates for ring-opening and decarboxylative catalytic transformations allowing for the development of new stereo- and enantioselective C-N, C-O, C-C, C-S and C-B bond formation reactions Transition-metal-mediated conversions have only recently been rejuvenated as powerful approaches towards the preparation of more complex molecules This minireview will highlight the potential of cyclic carbonates and structurally related heterocycles with a focus on their synthetic value and the mechanistic manifolds that are involved upon their conversion