Diastereoselective Synthesis of the Borylated d-Galactose Monosaccharide 3-Boronic-3-Deoxy-d-Galactose and Biological Evaluation in Glycosidase Inhibition and in Cancer for Boron Neutron Capture Therapy (BNCT).

Drug leads with a high Fsp3 index are more likely to possess desirable properties for progression in the drug development pipeline. This paper describes the development of an efficient two-step protocol to completely diastereoselectively access a diethanolamine (DEA) boronate ester derivative of monosaccharide d-galactose from the starting material 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose. This intermediate, in turn, is used to access 3-boronic-3deoxy-d-galactose for boron neutron capture therapy (BNCT) applications. The hydroboration/borane trapping protocol was robustly optimized with BH3.THF in 1,4-dioxane, followed by in-situ conversion of the inorganic borane intermediate to the organic boron product by the addition of DEA. This second step occurs instantaneously, with the immediate formation of a white precipitate. This protocol allows expedited and greener access to a new class of BNCT agents with an Fsp3 index = 1 and a desirable toxicity profile. Furthermore, presented is the first detailed NMR analysis of the borylated free monosaccharide target compound during the processes of mutarotation and borarotation.

New Insights into Boron Essentiality in Humans and Animals.

Boron (B) is considered a prebiotic chemical element with a role in both the origin and evolution of life, as well as an essential micronutrient for some bacteria, plants, fungi, and algae. B has beneficial effects on the biological functions of humans and animals, such as reproduction, growth, calcium metabolism, bone formation, energy metabolism, immunity, and brain function. Naturally organic B (NOB) species may become promising novel prebiotic candidates. NOB-containing compounds have been shown to be essential for the symbiosis between organisms from different kingdoms. New insights into the key role of NOB species in the symbiosis between human/animal hosts and their microbiota will influence the use of natural B-based colon-targeting nutraceuticals. The mechanism of action (MoA) of NOB species is related to the B signaling molecule (autoinducer-2-borate (AI-2B)) as well as the fortification of the colonic mucus gel layer with NOB species from B-rich prebiotic diets. Both the microbiota and the colonic mucus gel layer can become NOB targets. This paper reviews the evidence supporting the essentiality of the NOB species in the symbiosis between the microbiota and the human/animal hosts, with the stated aim of highlighting the MoA and targets of these species.

Two photon absorption energy transfer in the light-harvesting complex of photosystem II (LHC-II) modified with organic boron dye.

The plant light-harvesting complexes of photosystem II (LHC-II) play important roles in collecting solar energy and transferring the energy to the reaction centers of photosystems I and II. A two photon absorption compound, 4-(bromomethyl)-N-(4-(dimesitylboryl)phenyl)-N-phenylaniline (DMDP-CH2Br), was synthesized and covalently linked to the LHC-II in formation of a LHC-II-dye complex, which still maintained the biological activity of LHC-II system. Under irradiation with femtosecond laser pulses at 754 nm, the LHC-II-dye complex can absorb two photons of the laser light effectively compared with the wild type LHC-II. The absorbed excitation energy is then transferred to chlorophyll a with an obvious fluorescence enhancement. The results may be interesting and give potentials for developing hybrid photosystems.