An efficient AgOTf-catalyzed sequential reaction involving the oxidative ring-opening of aziridines by DMSO and aza-Michael addition has been developed. A series of 2,3-dihydro-4(1H)-isoquinolones were afforded in moderate to good yields by the formation of one new CO bond and one new C–N bond. The features of this sequential reaction include high bonding efficiency, use of a catalytic amount of catalysts, a broad substrate scope and mild conditions. This methodology provides a good choice for constructing the libraries of 2,3-dihydro-4(1H)-isoquinolones.

AbstractHighly selective recognition of acidic amino acids, such as glutamic acid and aspartic acid, by a positively charged calixpyridinium is reported. The complexation behavior of the calixpyridinium host towards a dipeptide containing the glutamic acid residue and a glutamic acid metabolite is also described.

We have successfully constructed a supramolecular assembly based on the anionic recognition of calixpyridinium for the first time employing native biocompatible polysaccharide hyaluronan as the guest, which showed hyaluronidase-responsive disassembly and temperature-responsive morphological conversion from a nanosphere to a nanosquare upon increasing the temperature.

We have successfully implemented the supramolecular tandem assay principle for the real-time, continuous, direct, and label-free monitoring of alkaline phosphatase activity through a fluorescence “switch-off” assay based on a novel calixpyridinium/dye reporter pair. Because several diseases can be preliminarily diagnosed in light of an abnormal level of alkaline phosphatase in serum, the application of tandem assays to selectively monitor alkaline phosphatase activity has feasible implications in disease diagnosis.

The inclusion complex of p-sulfonatocalix[5]arene (SC5A) with N-methyl-N′-(naphthalen-2-ylmethyl)-4,4′-bipyridinium (MVNp2+) guest was successfully prepared in single-crystal form. The obtained structure shows that SC5A is significantly distorted from the common ‘cone’ conformation induced by the complexation of MVNp2+. Moreover, the crystal packing of MVNp2+⊂SC5A reveals that the SC5A hosts do not assemble into a typical bilayer array, but arrange themselves into an unseen face-to-back bis-chain. As a result, hydrophobic molecular channels are fabricated rarely by SC5A hosts. A host–guest solution study was further performed by using NMR spectroscopy and microcalorimetry, the results of which are in accordance with the above crystallographic results. The molecular binding behaviors of SC5A with N-methyl-N′-adamantane carbomethyl-4,4′-bipyridinium (MVAd2+) guest that is structurally similar to MVNp2+ but with a different side group were also studied by using NMR spectroscopy and microcalorimetry in solution, the results of which are similar to those of SC5A with MVNp2+ guest as well.

The binding modes, inclusion abilities, and thermodynamic parameters for the intermolecular complexation of p-sulfonatocalix[4]arene (SC4A), p-sulfonatocalix[5]arene (SC5A), and p-sulfonatothiacalix[4]arene (STC4A), with methyl viologen (MV2+), ethyl viologen (EV2+), propyl viologen (PV2+), butyl viologen (BV2+), and benzyl viologen (BnV2+), were systematically investigated by NMR spectroscopy, molecular mechanics calculation, and microcalorimetry in neutral aqueous solutions. The obtained results show that all the sulfonated calixarene hosts can form stable inclusion complexes with viologen guests driven by much favorable enthalpy changes. All the viologen guests are encapsulated into the smaller SC4A cavity in their axial orientation. The larger SC5A cavity can accommodate all the viologen guests at its upper-rim midsection in the latitudinal orientation. The binding modes of more flexible STC4A with the smaller MV2+ and EV2+ guests are similar to those of SC5A with the two guests, while the binding modes of STC4A with the larger PV2+ and BV2+ guests are similar to those of SC4A with the two guests. The host selectivity for all the investigated viologen guests is the same: SC5A > SC4A > STC4A. The magnitude of the host selectivity is associated with the size of the guest. Moreover, the thermodynamic origin of the host selectivity for these viologen guests can be explained well by host–guest binding modes.

A new Lewis acid promoted three-component reaction between the aziridine, arene and aldehyde has been developed. This reaction involves sequential ring opening of aziridine and Pictet–Spengler condensation and gives a broad range of cis-1,4-disubstituted tetrahydroisoquinolines in moderate yields with good diastereoselectivities under mild conditions. The methodology provides a rapid and convergent synthesis for the scaffold of tetrahydroisoquinoline and serves as a good tool for constructing the libraries of substituted tetrahydroisoquinolines.

The molecular binding behaviors of p-sulfonatocalix[4]arene (SC4A), p-sulfonatocalix[5]arene (SC5A), and p-sulfonatothiacalix[4]arene (STC4A) with 5,6-dihydropyrazion[1,2,3,4-lmn][1,10]phenanthroline-4,7-diium (DP2+) were systematically investigated by crystallography, NMR spectroscopy, and microcalorimetry at pH 1–2. The obtained results showed that, in both aqueous solution and the solid state, DP2+ was immersed into the cavity of the sulfonated calixarene host in a slantwise degree with the aromatic moiety being included first. The different slantwise degree of the guest in the host cavity determined whether the host–guest capsule could be formed in the solid state. Furthermore, all three sulfonated calixarene hosts showed high affinities with DP2+ in the magnitude of 105–106 M–1 in aqueous solution, and the binding modes for host–guest complexation were explained from a thermodynamic viewpoint.

We have successfully implemented the supramolecular tandem assay principle for the real-time, continuous, direct, and label-free monitoring of alkaline phosphatase activity through a fluorescence “switch-off” assay based on a novel calixpyridinium/dye reporter pair. Because several diseases can be preliminarily diagnosed in light of an abnormal level of alkaline phosphatase in serum, the application of tandem assays to selectively monitor alkaline phosphatase activity has feasible implications in disease diagnosis.

The binding modes, inclusion abilities, and thermodynamic parameters for the intermolecular complexation of p-sulfonatocalix[4]arene (SC4A), p-sulfonatocalix[5]arene (SC5A), and p-sulfonatothiacalix[4]arene (STC4A), with methyl viologen (MV2+), ethyl viologen (EV2+), propyl viologen (PV2+), butyl viologen (BV2+), and benzyl viologen (BnV2+), were systematically investigated by NMR spectroscopy, molecular mechanics calculation, and microcalorimetry in neutral aqueous solutions. The obtained results show that all the sulfonated calixarene hosts can form stable inclusion complexes with viologen guests driven by much favorable enthalpy changes. All the viologen guests are encapsulated into the smaller SC4A cavity in their axial orientation. The larger SC5A cavity can accommodate all the viologen guests at its upper-rim midsection in the latitudinal orientation. The binding modes of more flexible STC4A with the smaller MV2+ and EV2+ guests are similar to those of SC5A with the two guests, while the binding modes of STC4A with the larger PV2+ and BV2+ guests are similar to those of SC4A with the two guests. The host selectivity for all the investigated viologen guests is the same: SC5A > SC4A > STC4A. The magnitude of the host selectivity is associated with the size of the guest. Moreover, the thermodynamic origin of the host selectivity for these viologen guests can be explained well by host–guest binding modes.

We have successfully constructed a supramolecular assembly based on the anionic recognition of calixpyridinium for the first time employing native biocompatible polysaccharide hyaluronan as the guest, which showed hyaluronidase-responsive disassembly and temperature-responsive morphological conversion from a nanosphere to a nanosquare upon increasing the temperature.