Synthesis of yellow and red fluorescent 1,3a,6a-triazapentalenes and the theoretical investigation of their optical properties

To expand the originally developed fluorescent 1,3a,6a-triazapentalenes as fluorescent labelling reagents, the fluorescence wavelength of the 1,3a,6a-triazapentalenes was extended to the red color region. Based on the noteworthy correlation of the fluorescence wavelength with the inductive effect of the 2-substituent, electron-deficient 2-(2-cyano-4-methoxycarbonylphenyl)-1,3a,6a-triazapentalene and 2-(2,6-dicyano-4-methoxycarbonylphenyl)-1,3a,6a-triazapentalene were synthesized. The former exhibited yellow fluorescence and the latter exhibited red fluorescence, and both compounds exhibited large Stokes shifts, and the 1,3a,6a-triazapentalene system enabled the same fluorescent chromophore to cover the entire region of visible wavelengths. The potential applications of the 1,3a,6a-triazapentalenes as fluorescent probes in the fields of the life sciences were investigated, and the 1,3a,6a-triazapentalene system was clearly proven to be useful as a fluorescent reagent for live cell imaging. Quantum chemical calculations were performed to investigate the optical properties of the 1,3a,6a-triazapentalenes. These calculations revealed that the excitation involves a significant charge-transfer from the 1,3a,6a-triazapentalene skeleton to the 2-substituent. The calculated absorption and fluorescence wavelengths showed a good correlation with the experimental ones, and thus the system could enable the theoretical design of substituents with the desired optical properties

Synthesis and Evaluation of 1,3a,6a-triazapentalene (TAP)-bonded system

A method of synthesizing a directly connected 1,3a,6a-triazapentalene (TAP) ring system as a linearly bonded aromatic system with a planar form was established. Various TAP-dimers and a 2-alkyl-TAP-trimer were synthesized and their fluorescence properties were evaluated. Although the direct connection of the TAP ring with other TAP rings did not affect the fluorescence properties in diluted solvent, TAP-dimers showed unique fluorescence properties derived from the aggregation state under highly concentrated conditions. In particular, TAP-dimer 5f showed aggregation-induced emission in highly concentrated solution, and 5b showed typical mechanochromic fluorescence in the solid state despite their compact molecular size

A suitable stereoisomer of vibrioferrin probes for iron uptake of Vibrio parahaemolyticus

Suitable Stereostructures of vibrioferrin probes for iron uptake of Vibrio parahaemolyticus was revealed. Stereoisomers of dansyl labeled vibrioferrin at the 2′′-position were synthesized and their uptake activities were evaluated. Vibrio parahaemolyticus take in both isomers at the 2′′-position. In addition to Vibrio parahaemolyticus, several bacteria have also taken up the (R)-isomer

Development of a mugineic acid family phytosiderophore analog as an iron fertilizer

Iron (Fe) is an essential nutrient, but is poorly bioavailable because of its low solubility in alkaline soils; this leads to reduced agricultural productivity. To overcome this problem, we first showed that the soil application of synthetic 2′-deoxymugineic acid, a natural phytosiderophore from the Poaceae, can recover Fe deficiency in rice grown in calcareous soil. However, the high cost and poor stability of synthetic 2′-deoxymugineic acid preclude its agricultural use. In this work, we develop a more stable and less expensive analog, proline-2′-deoxymugineic acid, and demonstrate its practical synthesis and transport of its Fe-chelated form across the plasma membrane by Fe(III)•2’-deoxymugineic acid transporters. Possibility of its use as an iron fertilizer on alkaline soils is supported by promotion of rice growth in a calcareous soil by soil application of metal free proline-2’-deoxymugineic acid

Transformations of 1-(Oxiranylmethyl)-1,2,3-triazoles into 2-(Oxiranylmethyl)-1,2,3-triazoles and Alkanenitriles

New reactions for the transformation of 1-(oxiranylmethyl)-1,2,3-triazoles into 2-(oxiranylmethyl)-1,2,3-triazoles or alkanenitriles were established. Successive treatment of the substrate with triflic acid and t-BuOH afforded 4,6-dihydro-5-hydroxy-1,3a,6a-triazapentalene derivative. Under the influence of NaH, the bicyclic compound was converted to a 2-(oxiranylmethyl)-1,2,3-triazole or an alkanenitrile. The reaction pathway depends on the substituent pattern of the epoxide side chain