Chemical Strategies Toward Prodrugs and Fluorescent Probes for Gasotransmitters

Three gaseous molecules are widely accepted as important gasotransmitters in mammalian cells, namely NO, CO and H2S. Due to the pharmacological effects observed in preclinical studies, these three gasotransmitters represent promising drug candidates for clinical translation. Fluorescent probes of the gasotransmitters are also in high demand; however, the mechanisms of actions or the roles played by gasotransmitters under both physiological and pathological conditions remain to be answered. In order to bring these challenges to the attention of both chemists and biologists working in this field, we herein summarize the chemical strategies used for the design of both probes and prodrugs of these three gasotransmitters.

Thermal decomposition of hexamethylenetetramine: mechanistic study and identification of reaction intermediates via a computational and NMR approach

In a joint DFT and chemometrics study applied to NMR spectra, we disclose the structure of the main decomposition products of hexamethylenetetramine. The combination of these techniques enabled us to propose the structures of near-identical intermediates of the process and to unveil the structure of the main decomposition product of this priviliged structure.

Ultrasound responsive carbon monoxide releasing micelle

Carbon monoxide (CO), an endogenously produced gasotransmitter, has shown various therapeutic effects in previous studies. In this work, we developed an ultrasound responsive micelle for localized CO delivery. The micelle is composed of a pluronic shell and a core of a CO releasing molecule, CORM-2. The mechanism is based on the ultrasound response of pluronics, and the reaction between CORM-2 and certain biomolecules, e.g. cysteine. The latter allows CO release without significantly breaking the micelles. In a 3.5 mM cysteine solution, the micelles released low level of CO, indicating effective encapsulation of CORM-2. Treatment with a low intensity, non-focused ultrasound led to four times as much CO as the sample without ultrasonication, which is close to that of unencapsulated CORM-2. Significantly reduced proliferation of prostate cancer cells (PC-3) was observed 24 h after the PC-3 cells were treated with the CORM-2 micelles followed by ultrasound activation.

Metal-free carbon monoxide-releasing micelles undergo tandem photochemical reactions for cutaneous wound healing

Carbon monoxide (CO) has shown broad biomedical applications. The site-specific delivery and controlled release of CO is of crucial importance to achieve maximum therapeutic benefits. The development of carbon monoxide (CO)-releasing polymers (CORPs) can increase the stability, optimize pharmacokinetic behavior, and reduce the side effects of small molecule precursors. However, almost all established CORPs were synthesized through a post functional approach, although the direct polymerization strategy is more powerful in controlling the chain compositions and architectures. Herein, a direct polymerization strategy is proposed toward metal-free CO-releasing polymers (CORPs) based on photoresponsive 3-hydroxyflavone (3-HF) derivatives. Such CO-releasing amphiphiles self-assemble into micelles, having excellent water-dispersity. Intriguingly, photo-triggered tandem photochemical reactions confer successive fluorescence transitions from blue-to-red-to-colorless, enabling self-reporting CO release in vitro and in vivo as a result of the incorporation of 3-HF derivatives. More importantly, the localized CO delivery of CORPs by taking advantage of the spatiotemporal control of light stimulus outperformed conventional metal carbonyls such as CORMs in terms of anti-inflammation and cutaneous wound healing. This work opens a novel avenue toward metal-free CORPs for potential biomedical applications.

Crystal structure of memantine–carboxyborane

The synthesis and crystal structure of the title compound, C13H24BNO2 [systematic name: 3,5-dimethyladamantanylamine–boranecarboxylic acid or N-(carboxyboranylidene)-3,5-dimethyladamantan-1-amine], derived from the anti-Alzheimer's disease drug memantine is reported. The C—N—B—CO2 unit is almost planar (r.m.s. deviation = 0.095 Å). The extended structure shows typical carboxylic acid inversion dimers linked by pairwise O—H...O hydrogen bonds [O...O = 2.662 (3) Å]. The amino group forms a weak N—H...O hydrogen bond [N...O = 3.011 (3) Å], linking the dimers into [001] chains in the crystal. Highly disordered solvent molecules were treated using the SQUEEZE routine of PLATON [Spek (2015). Acta Cryst. C71, 9–18], which treats the electron density as a diffuse contribution without assignment of specific atom locations. A scattering contribution of 255 electrons was removed. The crystal studied was refined as a two-component twin.

Poly(butyl cyanoacrylate) nanoparticle containing an organic photoCORM

A new organic photoCORM encapsulated in a poly(butyl cyanoacrylate) nanoparticle showed nearly quantitative CO release under visible light and low cytotoxicity.

ROS-mediated carbon monoxide and drug release from drug-conjugated carboxyboranes

Dual nature of amine carboxyboranes for combined CO and drug delivery is facilitated by ROS.

Visible-light-activated photoCORMs: rational design of CO-releasing organic molecules absorbing in the tissue-transparent window

Rational design of visible-light-activatable transition-metal-free CO-releasing molecules with an emphasis on mechanistic details of the CO release.

Synthesis of biologically active boron-containing compounds

Boron-containing compounds which possess unique and attractive properties have received increasing attention from the pharmaceutical industry and academia recently. They have shown interesting and useful biological activities, including antibacterial, antifungal, antiparasitic, antiviral, and anti-inflammatory activities. In this review, the synthetic strategies for various boron-containing compounds, including peptidyl boronic acids, benzoxaboroles, benzoxaborines, benzodiazaborines, amine carboxyboranes, and amine cyanoboranes are summarized. Representative structures of each structural class and recently developed biologically active boron-containing compounds are used as examples in this review.

pH-Sensitive metal-free carbon monoxide prodrugs with tunable and predictable release rates

Carbon monoxide prodrugs with triggered release profiles are highly desirable for targeted CO delivery to minimize their untoward side-effects.

Nonmetallic carbon monoxide releasing molecules (CORMs)

Recent progress on nonmetallic carbon monoxide releasing molecules (CORMs) is reviewed.