Benzoin

Supramolecular chirality and crystallization from biocatalytic self-assembly in lipidic cubic mesophases.[Pubmed:30874704]

Nanoscale. 2019 Mar 28;11(13):5891-5895.

Biocatalytic self-assembly in a nanoconfined environment is widely used in nature to construct complex structures that endow special characteristics to life. There is tremendous interest in mimicking such bottom-up processes to fabricate functional materials. In this study, we have investigated a novel biomimetic scaffold based on lipidic cubic mesophases (LCMs), which provide a special nanoconfined environment for biocatalytic self-assembly and subsequent formation of organic crystals. (R)-Benzoin generated in situ from benzaldehyde in a reaction catalyzed by the enzyme benzaldehyde lyase (BAL) exhibits - when confined within LCMs - enhanced chirality compared to (R)-Benzoin in solution or (R)-Benzoin-doped LCMs. We infer that a metastable state is formed under kinetic control that displays enhanced supramolecular chirality. As they age, these metastable structures can further grow into thermodynamically stable crystals. The biomimetic, nanoconfined environment provided by the LCMs plays a key role in the development of supramolecular chirality and subsequent crystallization.

Comparing Negative Pressure Wound Therapy with Instillation and Conventional Dressings for Sternal Wound Reconstructions.[Pubmed:30859044]

Plast Reconstr Surg Glob Open. 2019 Jan 4;7(1):e2087.

Background: Muscle flap reconstruction has become a mainstay of therapy following treatment of sternal wound complications; however, success depends on removing wound exudate and infectious material from the wound before reconstruction and closure. Importantly, time to closure is a key factor affecting morbidity/mortality and cost-to-treat for this wound type. Methods: A retrospective analysis of 30 patients who were treated for sternal wound complications between June 2015 and October 2017 was performed. After surgical debridement, group 1 patients (n = 15) received negative pressure wound therapy (NPWT) with instillation and dwell time (NPWTi-d), instilling 1/8-strength Dakin's solution with a 20-minute dwell time followed by 2 hours of NPWT (-125 mm Hg); group 2 patients (n = 15) were treated with wet-to-moist dressings soaked in 1/8-strength Dakin's solution. After muscle flap reconstruction and closure with sutures, group 1 patients received closed incision negative pressure therapy, and group 2 patients received Benzoin and wound closure strips. Data collected included time to closure, therapy duration, number of debridements/dressing changes, drain duration, and complications. Results: There was a significantly shorter time to closure (P < 0.0001) for group 1 when compared with group 2. In addition, there were fewer therapy days (P = 0.0041), fewer debridements/dressing changes (P = 0.0011), and shorter drain duration (P = 0.0001) for group 1 when compared with group 2. Conclusions: We describe a novel regimen consisting of adjunctive NPWTi-d, along with debridement and systemic antibiotics, followed by closed incision negative pressure therapy after muscle flap reconstruction and closure, to help manage preexisting sternal wounds that had failed to close following a previous cardiac procedure.

Can the Radical Channel Contribute to the Catalytic Cycle of N-Heterocyclic Carbene (NHC) in Benzoin Condensation?[Pubmed:30457867]

J Org Chem. 2018 Nov 20.

NHC can catalyze Benzoin condensation via the key Breslow intermediate. EPR spectroscopy recently confirmed the existence of the radical species, but its catalytic role is still unclear. Herein, we use density functional approaches to study the radical-associated pathway in comparison with the non-radical mechanism reported previously. Theoretical investigations show that the non-radical path (DeltaG = 18.7 kcal/mol) is more kinetically favorable than the radical route (DeltaG = 27.6 kcal/mol), which is initialized by the hydrogen abstraction between the Breslow intermediate and benzaldehyde, leading to a radical pair. The product formation is thus dominated by the non-radical pathway. In addition, the Breslow intermediate is less stable than its keto form, which blocks the Benzoin condensation and the radical species could play an important role to assist the tautomerization and to promote the catalytic reaction.

Benzoins and cyclobenzoins in supramolecular and polymer chemistry.[Pubmed:30264062]

Chem Commun (Camb). 2018 Oct 23;54(85):11989-11997.

Benzoin condensation is one of the oldest rigorously described organic reactions, having been discovered in 1832 by Liebig and Wohler. It creates a new C-C bond and a stereocenter from ubiquitous aldehyde starting materials under simple cyanide-catalyzed conditions. We have recently discovered cycloBenzoins: a class of macrocyclic compounds prepared by a Benzoin cyclooligomerization of simple aromatic dialdehydes. CycloBenzoins' internal cavities suggest they should be intriguing solution-phase supramolecular hosts, while their crystallographic packing aligns these cavities into potentially useful pores in the solid state. Well-precedented derivatization chemistry allows rapid functionalization into heteroacenes, which are optoelectronic materials and models for graphene defects. This Feature Article summarizes our work on cycloBenzoins, together with other applications of Benzoins in supramolecular chemistry and materials science.