Cyclobenzoin Esters as Hosts for Thin Guests

Nitriles and terminal alkynes are important compounds in industrial and academic settings. Their supramolecular binding has been challenging without the intervention of metals, because of the small dimensions of their linear –C≡N and –C≡CH groups. Using a combination of crystallography and computation, we have shown that cyclotetrabenzoin esters can host terminal triple bonds of alkynes and nitriles in their electron-poor cavities. Within these cavities, π-clouds of triple bonds can establish favorable and virtually equidistant interactions with the four aromatic walls of the cyclotetrabenzoin skeleton. Binding is selective for aliphatic nitriles and terminal alkynes, with their aromatic counterparts residing outside of the cyclotetrabenzoin cavity. These findings are of relevance in the binding, separations, and activation of these and other linear molecular guests.

Cyclobenzoin Esters as Hosts for Thin Guests

Nitriles and terminal alkynes are important compounds in industrial and academic settings. Their supramolecular binding has been challenging without the intervention of metals, because of the small dimensions of their linear –C≡N and –C≡CH groups. Using a combination of crystallography and computation, we have shown that cyclotetrabenzoin esters can host terminal triple bonds of alkynes and nitriles in their electron-poor cavities. Within these cavities, π-clouds of triple bonds can establish favorable and virtually equidistant interactions with the four aromatic walls of the cyclotetrabenzoin skeleton. Binding is selective for aliphatic nitriles and terminal alkynes, with their aromatic counterparts residing outside of the cyclotetrabenzoin cavity. These findings are of relevance in the binding, separations, and activation of these and other linear molecular guests.

Palladium-catalyzed C-H activation of simple arenes and cascade reaction with nitriles: access to 2,4,5-trisubstituted oxazoles

An efficient and straightforward protocol for the assembly of pharmaceutically and biologically valuable oxazole skeleton is achieved for the first time from readily available simple arenes and functionalized aliphatic nitriles....

Plant Nitrilase Homologues in Fungi: Phylogenetic and Functional Analysis with Focus on Nitrilases in Trametes versicolor and Agaricus bisporus

Fungi contain many plant-nitrilase (NLase) homologues according to database searches. In this study, enzymes NitTv1 from Trametes versicolor and NitAb from Agaricus bisporus were purified and characterized as the representatives of this type of fungal NLase. Both enzymes were slightly more similar to NIT4 type than to NIT1/NIT2/NIT3 type of plant NLases in terms of their amino acid sequences. Expression of the synthetic genes in Escherichia coli Origami B (DE3) was induced with 0.02 mM isopropyl β-D-1-thiogalactopyranoside at 20 °C. Purification of NitTv1 and NitAb by cobalt affinity chromatography gave ca. 6.6 mg and 9.6 mg of protein per 100 mL of culture medium, respectively. Their activities were determined with 25 mM of nitriles in 50 mM Tris/HCl buffer, pH 8.0, at 30 °C. NitTv1 and NitAb transformed β-cyano-L-alanine (β-CA) with the highest specific activities (ca. 132 and 40 U mg−1, respectively) similar to plant NLase NIT4. β-CA was transformed into Asn and Asp as in NIT4 but at lower Asn:Asp ratios. The fungal NLases also exhibited significant activities for (aryl)aliphatic nitriles such as 3-phenylpropionitrile, cinnamonitrile and fumaronitrile (substrates of NLase NIT1). NitTv1 was more stable than NitAb (at pH 5–9 vs. pH 5–7). These NLases may participate in plant–fungus interactions by detoxifying plant nitriles and/or producing plant hormones. Their homology models elucidated the molecular interactions with various nitriles in their active sites.