Direct functionalization of BODIPY dyes by oxidative nucleophilic hydrogen substitution at the 3- or 3,5-positions.

BODIPY dyes are shown to be susceptible to oxidative nucleophilic substitution of the alpha-hydrogens, incorporating nitrogen and carbon nucleophiles in a single, high yielding step. The reaction is an excellent alternative to conventional functionalization of this popular fluorophore.

Influence of reducing carbohydrates on (6S)-5-methyltetrahydrofolic acid degradation during thermal treatments.

The mechanism and kinetics of the degradation of (6S)5-methyl-5,6,7,8-tetrahydrofolic acid in an aqueous solution in the presence of reducing carbohydrates such as glucose and fructose were investigated for thermal treatments. Preliminary experiments indicated that the presence of reducing carbohydrates, especially fructose (1.6 mM-1.5 M), strongly enhanced folate degradation at moderate temperatures (50-90 degrees C, 0-60 min). Identification of the predominant folate degradation products by LC-MS and NMR pointed to the formation of N(2alpha)-[1-(carboxyethyl)]-5-methyl-5,6,7,8-tetrahydrofolic acid diastereomers besides other folate degradation products upon prolonged heating (24 h, 100 degrees C) of (6S)5-methyl-5,6,7,8-tetrahydrofolic acid in fructose or dihydroxyacetone solutions. Using a Bayesian multiresponse kinetic modeling approach, kinetic characterization and elucidation of the degradation mechanism in the presence of equimolar amounts of dihydroxyacetone, fructose, and glucose were achieved. On the basis of the established degradation mechanism for (6S)5-methyl-5,6,7,8-tetrahydrofolic acid oxidation in the literature, it was shown that nonenzymatic glycation occurred due to reaction of dihydroxyacetone with 5-methyl-7,8-dihydrofolic acid. During thermal treatments (85-110 degrees C, 0-60 min), the nonenzymatic glycation reaction was characterized by an activation energy of 61.3 +/- 9.3 and 77.6 +/- 7.8 kJ mol(-1) in the presence of, respectively, dihydroxyacetone and fructose. Addition of L-ascorbic acid (1.13 mM) to folate samples (0.04 mM) with equimolar amounts of fructose prior to heating (100 degrees C, 0-45 min) was shown to retard the formation of 5-methyl-7,8-dihydrofolic acid and hence prevented the formation of the carboxyethylated derivatives under the investigated conditions.

Mechanism and related kinetics of 5-methyltetrahydrofolic acid degradation during combined high hydrostatic pressure-thermal treatments.

The mechanism and kinetics of the degradation of 5-methyltetrahydrofolic acid during thermal and combined high pressure-thermal treatments in an aqueous solution were investigated. In a first approach the degradation was described by a first-order kinetic model using single-response modeling, and the combined pressure-temperature dependence of the resulting degradation rate constants was empirically described. To obtain a mechanistic insight, degradation products were purified and identified by LC-MS and NMR. Quantification of an s-triazine derivative, 5-methyldihydrofolic acid, and p-aminobenzoyl-l-glutamate as predominant degradation products at atmospheric pressure resulted in elucidation and kinetic characterization of the folate degradation mechanism by Bayesian multiresponse modeling. The postulated mechanism was evaluated at elevated hydrostatic pressure. On the basis of the pressure and temperature dependence of the reaction rates, some degradation reactions were either accelerated or decelerated upon application of pressure. Multiresponse kinetics can be a valuable tool to assess the impact of high hydrostatic pressure and other processing techniques on nutrients, and incorporating mechanistic insights can advance the current kinetic approach for process optimization.