The first synthesis of tetraglucosyl glucitol having phytoalexin-elicitor activity in rice cells based on a sequential glycosylation strategy

We describe a highly convergent approach for the synthesis of the tetraglucosyl glucitol 1 and its derivatives 4, 5 and 6 which exhibit phytoalexin-elicitor activity in rice cells based on sequential glycosylation.     

A conformationally reliable spacer for molecular tweezers

[figure: see text] A reliable and rigid spacer, trans,trans,trans-perhydronaphthacene, for molecular tweezers was designed. A synthesis and molecular recognition study of its 1,14-disubstituted derivatives was carried out.     

NAA and UV Laser Ablation ICP-MS for Platinum Group Elements and Gold Determination in NiS Fire Assay Buttons: A Comparison between Two Methods

NAA and UV laser ablation ICP-MS were used to determine platinum group elements (PGEs) and gold in the geological reference materials UMT-1, WPR-1, WMG-1, GPT-4 and GPt-6, after NiS fire assay. Both methods presented results were good agreement with the recommended values. NAA gave more accurate values for Ir (relative errors between 0 to 9%) and UV-LA-ICP-MS presented better results for Pt (relative errors less than 12%, except for WPR-1). UV-LA-ICP-MS showed better sensitivity than NAA for Pd and Os. On the other hand, NAA showed lower detection limits for Ir and Au. Advantages and disadvantages of each method are discussed.     

A Combined Experimental and Computational Study on the Cycloisomerization of 2‐Ethynylbiaryls Catalyzed by Dicationic Arene Ruthenium Complexes

Ruthenium‐catalyzed cycloisomerization of 2‐ethynylbiaryls was investigated to identify an optimal ruthenium catalyst system. A combination of [η⁶‐(p‐cymene)RuCl₂(PR₃)] and two equivalents of AgPF₆ effectively converted 2‐ethynylbiphenyls into phenanthrenes in chlorobenzene at 120 °C over 20 h. Moreover, 2‐ethynylheterobiaryls were found to be favorable substrates for this ruthenium catalysis, thus achieving the cycloisomerization of previously unused heterocyclic substrates. Moreover, several control experiments and DFT calculations of model complexes were performed to propose a plausible reaction mechanism.