The chemical reactivities of DOPA and dopamine derivatives and their regioselectivities upon oxidative nucleophilic trapping

Pseudo-bottle-brush decorated thin-film composite desalination membranes with ultrahigh mineral scale resistance

High water recovery is crucial to inland desalination but is impeded by mineral scaling of the membrane. This work presents a two-step modification approach for grafting high-density zwitterionic pseudo-bottle-brushes to polyamide reverse osmosis membranes to prevent scaling during high-recovery desalination of brackish water. Increasing brush density, induced by increasing reaction time, correlated with reduced scaling. High-density grafting eliminated gypsum scaling and almost completely prevented silica scaling during desalination of synthetic brackish water at a recovery ratio of 80%. Moreover, scaling was effectively mitigated during long-term desalination of real brackish water at a recovery ratio of 90% without pretreatment or antiscalants. Molecular dynamics simulations reveal the critical dependence of the membrane's silica antiscaling ability on the degree to which the coating screens the membrane surface from readily forming silica aggregates. This finding highlights the importance of maximizing grafting density for optimal performance and advanced antiscaling properties to allow high-recovery desalination of complex salt solutions.

An electrochemical access to 2-amino-2,3-dihydro-1,4-benzodioxanes derived from hydroxytyrosol

The anodic oxidation of a natural antioxidative catechol, hydroxytyrosol, was developed in an acetonitrile/dimethylsulfoxide (or acetonitrile/water) solvent mixture to produce in a stable way the resulting non-activated o-quinone and generate structural analogues. 2-Amino-2,3-dihydro-1,4-benzodioxane derivatives were obtained as two regioisomers in good to high overall yields (65-90%) and 1 : 3 ratios, through an inverse electron demand Diels-Alder (IEDDA) reaction between the electrogenerated o-quinone and tertiary enamines. The insertion of an electron withdrawing (or electron donating) group on the catechol modified their relative proportions, so that the reaction became regiospecific. With some aliphatic enamines, a competitive 1,6-Michael addition took place, affording 2-hydroxy-1,2,4,5-tetrahydrobenzo[d]oxepine compounds.

Catecholamine Derivatives as Novel Crosslinkers for the Synthesis of Versatile Biopolymers

Catecholamine metabolites are not only involved in primary metabolism, but also in secondary metabolism, serving a diverse array of physiologically and biochemically important functions. Melanin, which originates from dopa and dopamine, found in the hair, eye, and skin of all animals, is an important biopolymeric pigment. It provides protection against damaging solar radiation to animals. N-Acetyldopamine and N-β-alanyldopamine play a crucial role in the hardening of the exoskeletons of all insects. In addition, insects and other arthropods utilize the melanogenic process as a key component of their defense systems. Many marine organisms utilize dopyl peptides and proteins as bonding materials to adhere to various substrata. Moreover, the complex dopa derivatives that are precursors to the formation of the exoskeletons of numerous marine organisms also exhibit antibiotic properties. The biochemistry and mechanistic transformations of different catecholamine derivatives to produce various biomaterials with antioxidant, antibiotic, crosslinking, and gluing capabilities are highlighted. These reactivities are exhibited through the transient and highly reactive quinones, quinone methides, and quinone methide imine amide intermediates, as well as chelation to metal ions. A careful consideration of the reactivities summarized in this review will inspire numerous strategies for synthesizing novel biomaterials for future medical and industrial use.

A Bioinspired Synthesis of 1,4-Benzothiazines by Selective Addition of Sulfur Nucleophiles to ortho-Quinones

Herein, we report a bioinspired approach to the synthesis of 1,4-benzothiazines by drawing inspiration from the biosynthesis of pheomelanin pigments (pheomelanogenesis). In this context, general conditions for the regioselective coupling reaction between ortho-quinones and thiols were developed. The mild conditions proved amenable to a wide scope of both thiol and ortho-quinone coupling partners while simultaneously suppressing redox-exchange. The utility of this methodology was demonstrated by a synthesis of 1,4-benzothiazines, following a biomimetic, oxidative cyclization.

An alternative approach to the synthesis of the three fragments of anachelin H

The synthesis of the fully protected peptide, polyketide and alkaloid fragments of anachelin H is presented. The peptide fragment was prepared using a liquid phase peptide synthesis; the polyketide fragment was synthetized using a cross metathesis and an intramolecular oxa-Michael reaction as the key steps to introduce the desired stereochemistry; finally, the alkaloid fragment was obtained by an oxidative cyclization of a catechol derivative using potassium ferricyanide. The synthesis of all fragments was based on the use of natural amino acids as sources of asymmetry. The independent synthesis of the three fragments should allow more efficient biological studies on the fragments instead of the whole natural product. Experiments to illustrate the coupling of fragments and the effectiveness of the convergent strategy are also described.

Recent Trends in Mussel-Inspired Catechol-Containing Polymers (A Review)

Syntheses and applications of mussel-inspired polymeric materials have gained a foothold in research in recent years. Mussel-inspired chemistry coupled to Michael addition and Schiff’s base reactions was the key success for this intensive research. Unequivocally, The basic building brick of these materials is catechol-containing moiety, namely, 3,4-dihydroxyphenyl-L-alanine (L-DOPA or DOPA) and dopamine (DA). These catechol-based units within the chemical structure of the material ensure chiefly its adhesive characteristic to adherends of different natures. The newly-made catechol-bearing polymeric materials exhibit unique features, implying their importance in several uses and applications. Technology advent is being advantaged with these holdfast mussel protein-like materials. This review sheds light into the recent advances of such mussel-inspired materials for their adhesion capacity to several substrata of different natures, and for their applications mainly in antifouling coatings and nanoparticles technology.

A one step method for the functional and property modification of DOPA based nanocoatings

Biomimetic poly(catecholamine) coatings have gained much attention in recent years due to their versatility as functional materials. Despite this, only limited methods are available to modify the function and property of poly(catecholamine) coatings, primarily through post-modification methods. Our approach reported herein provides a simple approach to the fabrication of novel functionalized poly(catecholamine) coatings. The strategy employs the copolymerization of N-Ac-3,4-dihydroxyphenylalanine methyl ester (NADOPAMe) with nucleophilic additives, giving rise to nano-coatings on various surfaces including plastic, metal, glass and polymers. With the appropriate choice of nucleophilic additives, coatings with desired properties can be achieved. This is demonstrated through the fabrication of a redox responsive coating based on NADOPAMe with cysteamine as additive, which shows a concentration-dependent glutathione (GSH) responsive behavior. The ability to utilize this as a controlled release system is also demonstrated.