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Theme 2 colloquium: "Directionality of unconventional intermolecular interactions & pyrene based carbohydrate receptors" (Lecture)

Tuesday 12 March 2019Add to my calendar
from 16:00
dr. Tiddo Mooibroek (Van 't Hoff Institute for Molecular Science, UvA)

dr. Tiddo Mooibroek

Intermolecular interactions (e.g. hydrogen bonding) underpin the field of supramolecular chemistry. A firm understanding of intermolecular interactions in their entirety is thus of interest to supramolecular chemists [1]. A key question to address the potential usefulness of such interactions is whether they can manifest themselves in a directional fashion within solid state structures. This question will be answered in the affirmative for several interactions during the first part of this presentation, using a statistical analysis method [2] to evaluate crystal structure data [3].

The second part of this presentation will deliberate on several synthetic receptors that can bind carbohydrates in water [4]. Carbohydrates are Nature’s most versatile class of molecules and fulfil various functions in the immune response system [5]. Selective recognition of a particular (oligo-)saccharide could thus be exploited as an analytical means in biomedical research. For some illnesses, selective sensing could potentially be used as a diagnostic tool [5,6]. However, binding carbohydrates selectively and in their natural environment (water) is challenging due to their hydromimetic hydroxyl exterior and the subtle differences between structural isomers [6]. This challenge has been confronted using macrocyclic cages of a general ‘temple’ design that comprises complementary supramolecular synthons for interacting with a carbohydrate; polar ‘pillars’ for hydrogen bonding and hydrophobic aromatic surfaces for CH-π interactions (see examples below) [7]. A remarkable selectivity has been demonstrated using biphenyl-based synthetic lectins with three (1) [4a] or four (2) [4b] pillars, although the binding affinities are generally moderate (Ka < 100 M-1).
fig Tiddo Mooibroek mrt2019

It was wondered what the effect would be of incorporating a larger condensed aromatic in these designs, leading to ten pyrenyl macrocycles including 3–6 [4c-4g]. Some of these proved to be very potent receptors for charge-neutral carbohydrates in water, with selective binding affinities (Ka) exceeding 10.000 M-1 for 3 vs oligoglucose [4c] and 4 vs GlcNAc-β-OR [4d]. Natural carbohydrate receptors (lectins) typically have affinities below 1.000 M-1 for such sugars. These pyrenyl-receptors thus out-perform Nature and represent a milestone towards truly applicable synthetic carbohydrate receptors.

1) a) Chem. Soc, Rev., 2017, 46, 1720; b) Chem. Rec., 2016, 1, 473; c) ChemPhysChem, 2015, 12, 2496.
2) CrystEngComm., 2012, 3, 1027.
3) a) Nature Commun., 2017, 8, 14822; b) CrystEngComm, 2017, 19, 4485; c) Cryst. Growth Des., 2016, 16, 5520; d) Chem. Commun., 2015, 51, 8, 1491; e) Chem. Commun., 2014, 84, 12626; f) Chem. Eur. J., 2014, 33, 10245; g) Chem. Sci. 2014, 5, 2191; h) Angew. Chem. Int. Ed., 2013, 47, 12317; i) CrystEngComm., 2013, 15, 4565; j) CrystEngComm., 2013, 15, 1802; k) CrystEngComm., 2012, 14, 8462; l) CrytsEngComm., 2012, 11, 3902.
4) a) Angew. Chem. Int. Ed., 2009, 48, 1775; b) Chem. Commun., 2013, 49, 3110; c) Nature Chemistry, 2016, 8, 69; d) Angew. Chem. Int. Ed., 2016, 55, 3387; e) Org. Biomol. Chem., 2016, 14, 1930; f) Angew. Chem. Int. Ed., 2016, 55, 9311; g) Chem. Sci., 2017, 8, 4056.
5) The Sugar Code, Wiley-VCH, 2009, Weinheim, Germany.
6) Carbohydrate Rrecognition, Wiley-VCH, 2011, Weinheim, Germany.
7) Angew. Chem. Int. Ed., 1999, 38, 2978.

This lecture fits in the IMM Theme 2 – Chemistry of Complex Systems – colloquium series, in which researchers from IMM Theme 2 as well as high-profile researchers from outside Radboud University present work that is of interest to scientists across Theme 2. These lectures take place on the second Tuesday of every month and are open to everyone in who is interested.

dr. Evan Spruijt & dr. Peter Korevaar