Abstract
New tetramethoxy-(tetra-hydrazinecarboxamide) cyclophanes with unexpected anti /anti conformation were prepared from the addition of chiral di oxolane-based dicarbohydrazides to 4,4 ′-diisocyanato-3,3 ′-dimethoxy-1,1 ′-biphenyl in anhydrous THF. The molecular recognition of the macrocycles to a selection of chiral carboxylic gue sts, i.e. , L-(+)-tartaric, D-(-)-tartaric, D-(-)quinic, L-(-)-malic, D-(+)-galacturonic and D-glucuronic acids, was investigated by using direct injection electrospray ionization time-of-flight (E SI-TOF) and tandem mass spectrometry. A series of 1,3-dioxolane-4,5-dicarbonyl- bis -(N-substituted)-hydrazinecarboxamides, which mimic the backbone structure of the new cyclophanes, were also synthesized by addition of dioxolane dicarbohydrazides to aromatic isocyanates and their complexation with the aforementioned carboxylic guests was investigated by using direct inje ction ESI-TOF MS and MS/MS.
Highlights
Molecular recognition has been given considerable attention during the past several decades.[1,2] It refers to the interactions taking place between two or more molecules via noncovalent bonds, such as hydrogen bonds (H-bonds), metal coordination, van der Waals and hydrophobic forces or π-π stacking
Synthesis and conformational analysis Recently, we reported the synthesis of a new class of chiral C2-symmetrical macrocycles, named tetra-(hydrazinecarboxamide) cyclophanes, in a [2+2] macrocyclization reaction.[25]
It is noteworthy that the cyclophane macrocycles, which were obtained by addition of the dioxolane dicarbohydrazides 1-5 to either 4,4′-oxybis(isocyanatobenzene) 7 or bis(4-isocyanatophenyl)methane 8 adopted a syn/anti conformation, which was stabilized by two intramolecular H-bonds (NH...CO).[25]
Summary
Molecular recognition has been given considerable attention during the past several decades.[1,2] It refers to the interactions taking place between two or more molecules via noncovalent bonds, such as hydrogen bonds (H-bonds), metal coordination, van der Waals and hydrophobic forces or π-π stacking. We assessed the molecular recognition affinity of the new cyclophanes to a selection of chiral carboxylic guests by using direct injection ESI-TOF MS and MS/MS. We discuss the synthesis of new oxygenated tetra-(hydrazinecarboxamide) cyclophanes with unexpected anti/anti orientation of the amide functionalities and assess their solution-phase recognition to a selection of carboxylic guests by using direct injection ESI-TOF MS and MS/MS.
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