(RS)-Tricarbon­yl(η4-1,3-diacet­oxy-5,5-dimethyl­cyclo­hexa-1,3-diene)iron(0)

In the title compound, [Fe(C12H16O4)(CO)3], the diene moiety of the mol­ecule is virtually planar, with a C—C—C—C torsion angle of −1.4 (2)°. The six-membered ring exhibits a boat conformation, with torsion angles of 46.2 (2) and 46.5 (3)° for a double-bond and the two attached Csp 3 atoms. The Fe atom is coordinated to all four of the diene C atoms, with bond lengths between 2.041 (2) and 2.117 (2) Å. The Fe(CO)3 tripod adopts a conformation with one CO ligand eclipsing the Csp 3—Csp 3 single bond

Acyloxybutadiene Iron Tricarbonyl Complexes as Enzyme-Triggered CO-Releasing Molecules (ET-CORMs)

Molecular hazardous materials transport: Enzyme-triggered CO-releasing molecules (ET-CORMs) offer new options for the delivery of CO. The cleavage of dienylester iron tricarbonyl complexes by an esterase under mild oxidative conditions generates CO, which causes a strong inhibiting activity of the compounds to inducible nitric oxide synthase as shown in a cellular assay

On the Diastereoselectivity of the Complexation of Ketopinic Acid-Derived 2-Acyloxy-1,3-cyclohexadienes and the Configurational Stability of Dienol-Fe(CO)(3) Complexes. A Case Study

In the course of an attempt to synthesize 2-acyloxycyclohexa-1,3-diene-Fe (CO)(3) complexes in nonracemic form, we reinvestigated the fully diastereoselective Fe(CO)(3) complexation of (S,S)-2-ketopinoyloxy-1,3-cyclohexadiene, which had been described by Yeh and co-workers (Organometallics 2001, 20, 289-295). However, after cleaving off the chiral auxiliary unit, we only obtained racemic complexes, also for a related substrate. For this reason, we performed control experiments to exclude possible racemization mechanisms and confirmed the configurational integrity of the dienol-Fe(CO)(3) intermediates using stereochemically defined dihydrocarvone-derived complexes. We finally could show that the complexation described by Yeh actually proceeds without any detectable diastereoselectivity. At the end, the virtually inseparable diastereomers of the chiral complexation products could be distinguished by careful NMR and chiral HPLC analyses

Vinylogous Winstein Rearrangement: Unexpected Isomerization of an Azide-Substituted Cyclohexadiene-Fe(CO)3 Complex

In the course of our research into enzyme-triggered CO-releasing molecules (ET-CORMs), we were interested in using 2-acetoxy-5-azido-1,3-cyclohexadiene-Fe(CO)3 (rac-2) as a building block for further structural modification by means of Cu -catalyzed azide-alkyne cycloaddition (CuAAC click chemistry). Treatment of [2-acetoxy-cyclohexadienyl-Fe(CO)3]+[PF6]- with Zn(N3)2, TMS-N3, or NaN3 surprisingly afforded 2-acetoxy-1-azido-2,4-cyclohexadiene-Fe(CO)3 (rac-9) as the main product. We could show that rac-2 is primarily formed under kinetic control but undergoes a rapid isomerization to rac-9 (as the thermodynamic product) in a formal vinylogous Winstein rearrangement under concomitant migration of the Fe(CO)3 moiety. This unprecedented reaction displays a 1st order kinetics and appears to proceed via an ionic (rather than a concerted intramolecular) mechanism as supported by crossover experiments using deuterated compounds. The CuAAC reaction of rac-9 with propargylic alcohol afforded triazole rac-13, which was demonstrated (by headspace-gas chromatography (GC)) to act as an ET-CORM in the presence of porcine liver esterase

A Portable Multi-Modal Cushion for Continuous Monitoring of a Driver’s Vital Signs

With higher levels of automation in vehicles, the need for robust driver monitoring systems increases, since it must be ensured that the driver can intervene at any moment. Drowsiness, stress and alcohol are still the main sources of driver distraction. However, physiological problems such as heart attacks and strokes also exhibit a significant risk for driver safety, especially with respect to the ageing population. In this paper, a portable cushion with four sensor units with multiple measurement modalities is presented. Capacitive electrocardiography, reflective photophlethysmography, magnetic induction measurement and seismocardiography are performed with the embedded sensors. The device can monitor the heart and respiratory rates of a vehicle driver. The promising results of the first proof-of-concept study with twenty participants in a driving simulator not only demonstrate the accuracy of the heart (above 70% of medical-grade heart rate estimations according to IEC 60601-2-27) and respiratory rate measurements (around 30% with errors below 2 BPM), but also that the cushion might be useful to monitor morphological changes in the capacitive electrocardiogram in some cases. The measurements can potentially be used to detect drowsiness and stress and thus the fitness of the driver, since heart rate variability and breathing rate variability can be captured. They are also useful for the early prediction of cardiovascular diseases, one of the main reasons for premature death. The data are publicly available in the UnoVis dataset

Synthesis and performance of Acyloxy-diene-Fe(CO)(3) complexes with variable chain lengths as enzyme-triggered carbon monoxide-releasing molecules

Novel η4-acyloxy-cyclohexadiene-Fe(CO)3 complexes (with variable length of the acyloxy chain) were synthesized as potential enzyme-triggered carbon monoxide (CO)-releasing molecules (ET-CORMs). The molecular structure of two complexes was additionally confirmed by X-ray crystallography. The enzyme-triggered CO-releasing activity of the compounds was assessed under physiological conditions (37 °C, 0.1 M phosphate buffer, pH = 7.4) by headspace gas chromatography (GC) and additionally by means of a myoglobin assay (UV). The relative rate of CO release and the amount of liberated CO were found to depend on the length of the acyloxy chain and its position at the diene unit (outer or inner position). Some of the new ET-CORMs exhibited very good biological activity as assessed in different cellular assays (cytotoxicity, protective effect against hypothermia-associated cell damage, and inhibition of TNF-α-mediated VCAM-1 expression)

Iron Dienylphosphate Tricarbonyl complexes as water-soluble enzyme-triggered CO-releasing molecules (ET-CORMs)

A series of racemic phosphoryloxy-substituted (eta(4)-cyclohexadiene)Fe(CO)(3) complexes was synthesized by exploiting the O-phosphorylation of (dienol)Fe(CO)(3) intermediates generated in situ from the corresponding triisopropylsiloxy-protected complexes. The phosphorylated products were fully characterized by spectroscopic methods, including single-crystal X-ray diffraction in four cases. Monodeprotection of two dimethyl phosphate derivatives with trimethylamine led to the tetramethylammonium salts of the (cyclohexadienyl methyl phosphate)Fe(CO)(3) complexes. These compounds are the first water-soluble enzyme-trigged CO-releasing molecules (ET-CORMs). The phosphatase-induced CO release was monitored by means of GC. The biological activity was assessed in different cellular assays. The compounds were shown to be only slightly toxic, and a moderate anti-inflammatory potential was determined in an assay based on the inhibition of inducible NO synthase (iNOS)-induced NO production