The Influence of Small Biomolecules, Salts and Buffers on the Molecular Recognition of Amide Naphthotube in Aqueous Solutions.

We found the binding affinities of amide naphthotube to neutral organic molecules in water are not influenced by most of small biomolecules, inorganic salts, and PBS and Tris buffers but are reduced in HEPES buffer through competitive binding. Nevertheless, salts do change the binding affinities of amide naphthotube to charged molecules through a screening effect.

ZnCl2-promoted domino reaction of 2-hydroxybenzonitriles with ketones for synthesis of 1,3-benzoxazin-4-ones.

A ZnCl2-promoted synthesis of 1,3-benzoxazin-4-one from 2-hydroxybenzonitriles and ketones was developed. This method displays facile access to a diverse range of substituted 1,3-benzoxazin-4-ones in good yields. This synthetic protocol has advantages: (i) easy availability of starting material; (ii) strong corrosive acid-free condition; (iii) high yield.

A 2,3-dialkoxynaphthalene-based naphthocage.

A 2,3-dialkoxynaphthalene-based naphthocage has been synthesized. This naphthocage prefers to bind small organic cations with its low-symmetry conformation, which is in contrast to 2,6-dialkoxynaphthalene-based naphthocages. Self-sorting of these two naphthocages with two structurally similar guests tetramethylammonium and tetraethylammonium was achieved as well.

Unexpected solvent effect on the binding of positively-charged macrocycles to neutral aromatic hydrocarbons.

Two positively-charged naphthotubes with imidazolium as the bridges were synthesized and their structures have been characterized by 1H NMR, MS, and X-ray crystallography. These naphthotubes are capable of binding aromatic hydrocarbons. Surprisingly, the binding affinities are much higher in CD3CN than in CD2Cl2. The solvent effect on the ion pairing interactions and competitive binding of CD2Cl2 was invoked to explain this unusual phenomenon.

Probing the guest-binding preference of three structurally similar and conformationally adaptive macrocycles.

A hybrid macrocycle was synthesized by combining the repeat units in oxatub[4]arene and zorb[4]arene, and its recognition behavior and conformational analysis were studied. Three structurally similar and conformationally adaptive macrocycles show different guest-binding selectivities and preferences even in a complex mixture containing three macrocycles and three guests.

Fluorescent monitoring of the reaction kinetics of nonfluorescent molecules enabled by a fluorescent receptor.

A facile fluorescent method was developed to quantitatively monitor the hydrolysis kinetics of nonfluorescent esters by using a fluorecent endo-functionalized molecular tube and its recognition ability towards small polar molecules in water. It is possible to determine the apparent rate constants and study the structure-activity relationship.

Allosteric cooperativity in ternary complexes with low symmetry.

Two new naphthotubes with ester linkers were synthesized and characterized. With the syn isomers of an ester naphthotube and an ether naphthotube, strong positive allosteric cooperativity in a ternary complex with two different hosts on one guest was achieved. This paves the way to construct robust supramolecular architectures with high complexity and diversity.

A semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J based on the spinosyn A aglycone.

Spinetoram, a mixture of 3'-O-ethyl-5,6-dihydrospinosyn J (XDE-175-J, major component) and 3'-O-ethylspinosyn L (XDE-175-L, minor component), is a novel kind of green and efficient insecticide with a broad range of action against various insects. Nowadays, spinetoram is widely used in agriculture and food storage. This work reports a 7-step semisynthesis of 3'-O-ethyl-5,6-dihydrospinosyn J from spinosyn A aglycone. The C9-OH and C17-OH of the aglycone are successively connected to 3-O-ethyl-2,4-di-O-methylrhamnose and D-forosamine after selective protection and deprotection steps. Then, with 10% Pd/C as catalyst, the 5,6-double bond of the macrolide was selectively reduced to afford 3'-O-ethyl-5,6-dihydrospinosyn J. In addition, the 3-O-ethyl-2,4-di-O-methylrhamnose is synthesized from rhamnose which is available commercially, while the D-forosamine and aglycone are obtained via the hydrolysis of spinosyn A. High yields were obtained in each step, and all intermediates in the synthesis were characterized by 1H NMR, 13C NMR and MS techniques. This study can be helpful for developing an efficient chemical synthesis of spinetoram, and it also offers opportunities to synthesize spinosyn analogues and rhamnose derivatives.

A convenient four-component one-pot strategy toward the synthesis of pyrazolo[3,4-d]pyrimidines.

An efficient one-pot synthesis of pyrazolo[3,4-d]pyrimidine derivatives by the four-component condensation of hydrazines, methylenemalononitriles, aldehydes and alcohols has been developed via two different reaction pathways. The structures of target products were characterized by IR spectroscopy, NMR ((1)H and (13)C) spectroscopy and HRMS (ESI) spectrometry. The crystal structure of 4-ethoxy-6-(2-nitrophenyl)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine was determined by single crystal X-ray diffraction.

N-(2-Methyl-3-oxo-1,3-diphenyl-prop-yl)acetamide.

In the title compound, C18H19NO2, the dihedral angle between the benzene rings is 42.0 (1)°. In the crystal, mol-ecules are linked by N-H⋯O and C-H⋯π inter-actions.

Pseudoaglycone of spinosyn a.

THE TITLE COMPOUND [SYSTEMATIC NAME: 9-ethyl-13-hy-droxy-14-methyl-2-(3,4,5-trimeth-oxy-6-methyl-tetra-hydro-2H-pyran-2-yl-oxy)-3,3a,5b,6,9,10,11,12,13,14,16a,16b-dodeca-hydro-1H-as-indaceno[3,2-d][1]oxacyclo-dodecine-7,15(2H,5aH)-dione], C(33)H(50)O(9), was obtained by hydrolysis of Spinosyn A. The fused cyclo-pentene ring adopts a twisted conformation, while the fused cyclo-hexene and cyclo-pentane rings are in envelope conformations with the same C atom at the flaps. In the crystal, mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds into a layer parallel to the ab plane.

6'-Bromo-1'H-spiro-[cyclo-hexane-1,2'-pyrido[2,3-d]pyrimidin]-4'(3'H)-one.

The title compound, C(12)H(14)BrN(3)O, is built up from two fused six-membered rings and one six-membered ring linked through a spiro C atom. The hydro-pyrimidine ring has an envelope conformation and the cyclo-hexane ring is in a chair conformation. In the crystal, mol-ecules are linked by N-H⋯O and N-H⋯N hydrogen bonds, forming a mol-ecular tape along the b axis.