1.General method for the preparation of active esters by palladium-catalyzed alkoxycarbonylation of aryl bromides.
de Almeida AM1, Andersen TL, Lindhardt AT, de Almeida MV, Skrydstrup T. J Org Chem. 2015 Feb 6;80(3):1920-8. doi: 10.1021/jo5025464. Epub 2015 Jan 21.
A useful method was developed for the synthesis of active esters by palladium-catalyzed alkoxycarbonylation of (hetero)aromatic bromides. The protocol was general for a range of oxygen nucleophiles including N-hydroxysuccinimide (NHS), pentafluorophenol (PFP), hexafluoroisopropyl alcohol (HFP), 4-nitrophenol, and N-hydroxyphthalimide. A high functional group tolerance was displayed, and several active esters were prepared with good to excellent isolated yields. The protocol was extended to access an important synthetic precursor to the HIV-protease inhibitor, saquinavir, by formation of an NHS ester followed by acyl substitution.
2.Preparation of Reactive Oligo(p-Phenylene Vinylene) Materials for Spatial Profiling of the Chemical Reactivity of Intracellular Compartments.
Nie C1, Li S1, Wang B1, Liu L1, Hu R1, Chen H1, Lv F1, Dai Z2, Wang S1. Adv Mater. 2016 Mar 22. doi: 10.1002/adma.201600106. [Epub ahead of print]
An oligo(p-phenylene vinylene) derivative (OPV-pfp) functionalized with pentafluorophenol active ester is designed and synthesized. The high reactivity of OPV-pfp with biological small molecules or macromolecules containing amino groups under physiological conditions leads to spectra changes of OPV-pfp; thus, spatial reactivity discrimination for different subcellular structures inside cells is realized by triggering and imaging the fluorescence signal change of the OPV-pfp.
3.Electronic spectra and excited state dynamics of pentafluorophenol: Effects of low-lying πσ(∗) states.
Karmakar S1, Mukhopadhyay DP1, Chakraborty T1. J Chem Phys. 2015 May 14;142(18):184303. doi: 10.1063/1.4919950.
Multiple fluorine atom substitution effect on photophysics of an aromatic chromophore has been investigated using phenol as the reference system. It has been noticed that the discrete vibronic structure of the S1←S0 absorption system of phenol vapor is completely washed out for pentafluorophenol (PFP), and the latter also shows very large Stokes shift in the fluorescence spectrum. For excitations beyond S1 origin, the emission yield of PFP is reduced sharply with increase in excess vibronic energy. However, in a collisional environment like liquid hydrocarbon, the underlying dynamical process that drives the non-radiative decay is hindered drastically. Electronic structure theory predicts a number of low-lying dark electronic states of πσ(∗) character in the vicinity of the lowest valence ππ(∗) state of this molecule. Tentatively, we have attributed the excitation energy dependent non-radiative decay of the molecule observed only in the gas phase to an interplay between the lowest ππ(∗) and a nearby dissociative πσ(∗) state.
4.Postpolymerization modification using less cytotoxic activated ester polymers for the synthesis of biological active polymers.
He L1, Szameit K, Zhao H, Hahn U, Theato P. Biomacromolecules. 2014 Aug 11;15(8):3197-205. doi: 10.1021/bm500902t. Epub 2014 Jul 18.
Activated ester polymers, pioneered by Ferruti and Ringsdorf in the 1970s, are attractive polymeric materials because they can easily be converted into functional polymers by reacting with amine nucleophiles. In the present study, methyl salicylate acrylate, salicyl acrylate, and tert-butyl salicylate acrylate monomers were polymerized yielding three novel reactive precursors suitable for the postpolymerization modification with primary and secondary amines. The reactivities of poly(pentafluorophenyl acrylate), poly(methyl salicylate acrylic ester), and poly(salicyl acrylate) toward amines were compared by kinetic studies and revealed the practical applicability of salicylic acid based derivatives for efficient postpolymerization modifications. In addition, in vitro cytotoxicity of water-soluble leaving groups, pentafluorophenol and salicylic acid, as well as water-soluble polymers containing the respective activated ester groups were investigated using HeLa cells.