A variety of metalated tosylhydrazone salts derived from benzaldehyde have been prepared and were reacted with benzaldehyde in the presence of tetrahydrothiophene (THT) (20 mol %) and Rh2(OAc)4 (1 ...mol %) to give stilbene oxide. Of the lithium, sodium, and potassium salts tested, the sodium salt was found to give the highest yield and selectivity. This study was extended to a wide variety of aromatic, heteroaromatic, aliphatic, α,β-unsaturated, and acetylenic aldehydes and to ketones. On the whole, high yields of epoxides with moderate to very high diastereoselectivities were observed. A broad range of tosylhydrazone salts derived from aromatic, heteroaromatic, and α,β-unsaturated aldehydes was also examined using the same protocol in reactions with benzaldehyde, and again, good yields and high diastereoselectivities were observed in most cases. Thus, a general process for the in situ generation of diazo compounds from tosylhydrazone sodium salts has been established and applied in sulfur-ylide mediated epoxidation reactions. The chiral, camphor-derived, 2.2.1 bicyclic sulfide 7 was employed (at 5−20 mol % loading) to render the above processes asymmetric with a range of carbonyl compounds and tosylhydrazone sodium salts. Benzaldehyde tosylhydrazone sodium salt gave enantioselectivities of 91 ± 3% ee and high levels of diastereoselectivity with a range of aldehydes. However, tosylhydrazone salts derived from a range of carbonyl compounds gave more variable selectivities. Although those salts derived from electron-rich or neutral aldehydes gave high enantioselectivities, those derived from electron-deficient or hindered aromatic aldehydes gave somewhat reduced enantioselectivities. Using α,β-unsaturated hydrazones, chiral sulfide 7 gave epoxides with high diastereoselectivities, but only moderate yields were achieved (12−56%) with varying degrees of enantioselectivity. A study of solvent effects showed that, while the impact on enantioselectivity was small, the efficiency of diazo compound generation was influenced, and CH3CN and 1,4-dioxane emerged as the optimum solvents. A general rationalization of the factors that influence both relative and absolute stereochemistry for all of the different substrates is provided. Reversibility in formation of the betaine intermediate is an important issue in the control of diastereoselectivity. Hence, where low diastereocontrol was observed, the results have been rationalized in terms of the factors that contribute to the reduced reversion of the syn betaine back to the original starting materials. The enantioselectivity is governed by ylide conformation, facial selectivity in the ylide reaction, and, again, the degree of reversibility in betaine formation. From experimental evidence and calculations, it has been shown that sulfide 7 gives almost complete control of facial selectivity, and, hence, it is the ylide conformation and degree of reversibility that are responsible for the enantioselectivity observed. A simple test has been developed to ascertain whether the reduced enantioselectivity observed in particular cases is due to poor control in ylide conformation or due to partial reversibility in the formation of the betaine.
Background and Purpose
Pulmonary arterial hypertension (PAH), a rare fatal disorder characterised by inflammation, vascular remodelling and vasoconstriction. Current vasodilator therapies reduce ...pulmonary arterial pressure but not mortality. The G‐protein coupled formyl peptide receptors (FPRs) mediates vasodilatation and resolution of inflammation, actions possibly beneficial in PAH. We investigated dilator and anti‐inflammatory effects of the FPR biased agonist compound 17b in pulmonary vasculature using mouse precision‐cut lung slices (PCLS).
Experimental Approach
PCLS from 8‐week‐old male and female C57BL/6 mice, intrapulmonary arteries were pre‐contracted with 5‐HT for concentration–response curves to compound 17b and 43, and standard‐of‐care drugs, sildenafil, iloprost and riociguat. Compound 17b‐mediated relaxation was assessed with FPR antagonists or inhibitors and in PCLS treated with TNF‐α or LPS. Cytokine release from TNF‐α‐ or LPS‐treated PCLS ± compound 17b was measured.
Key Results
Compound 17b elicited concentration‐dependent vasodilation, with potencies of iloprost > compound 17b = riociguat > compound 43 = sildenafil. Compound 17b was inhibited by the FPR1 antagonist cyclosporin H but not by soluble guanylate cyclase, nitric oxide synthase or cyclooxygenase inhibitors. Under inflammatory conditions, the efficacy and potency of compound 17b were maintained, while iloprost and sildenafil were less effective. Additionally, compound 17b inhibited secretion of PAH‐relevant cytokines via FPR2.
Conclusions and Implications
Vasodilation to compound 17b but not standard‐of‐care vasodilators, is maintained under inflammatory conditions, with additional inhibition of PAH‐relevant cytokine release. This provides the first evidence that targeting FPR, with biased agonist, simultaneously targets vascular function and inflammation, supporting the development of FPR‐based pharmacotherapy to treat PAH.
LINKED ARTICLES
This article is part of a themed issue Therapeutic Targeting of G Protein‐Coupled Receptors: hot topics from the Australasian Society of Clinical and Experimental Pharmacologists and Toxicologists 2021 Virtual Annual Scientific Meeting. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.14/issuetoc
The LUX-ZEPLIN experiment is a dark matter detector centered on a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA. This ...Letter reports results from LUX-ZEPLIN's first search for weakly interacting massive particles (WIMPs) with an exposure of 60 live days using a fiducial mass of 5.5 t. A profile-likelihood ratio analysis shows the data to be consistent with a background-only hypothesis, setting new limits on spin-independent WIMP-nucleon, spin-dependent WIMP-neutron, and spin-dependent WIMP-proton cross sections for WIMP masses above 9 GeV/c^{2}. The most stringent limit is set for spin-independent scattering at 36 GeV/c^{2}, rejecting cross sections above 9.2×10^{-48} cm at the 90% confidence level.
A practical, general, and convergent route to epoxides with control of the relative and absolute stereochemistry has been achieved by generating the reactive intermediate (the diazo compound) in situ ...from tosylhydrazone salts (see scheme, PTC=phase‐transfer catalyst, Ts=toluene‐4‐sulfonyl). High yields (58–82 %), high d.r. (88:12–98:2), and high ee values (87–94 %) have been obtained using a new class of stable chiral sulfides at low catalyst loading (5 mol %) and Rh2(OAc)4 (0.5 mol %).
We have designed and prepared a catalyst for the asymmetric reduction of ketones which combines a phosphinamide and a boron-containing heterocyclic ring. The former group acts to direct and activated ...the borane, whilst the latter provides a well defined position for location of the ketone. The resulting reduction therefore takes place in a well-defined stereochemical environment. Enantiomeric excesses of up to 59%, in a predictable absolute sense, were achieved. Evidence that O- co-ordination of borane is important in the reduction mechanism is also presented
The synthesis and use of a novel catalyst for the asymmetric reductions of ketones by borane is described. Enantiomeric excesses of up to 59%, in a predictable sense, have been obtained.
A novel class of recoverable and highly stable phosphinamide catalysts for the asymmetric reduction of ketones by borane is described. Enantiomeric excesses of up to 92% have been obtained using 10 ...mol% of the optimum catalyst.
10 mol% of phosphinamide
5 catalyses reduction of chloroacetophenone by borane to give a product of 92% e.e.
The phosphinamide N-protecting group is demonstrated to be an effective directing group for diastereoselective reductions of proximal ketones. A range of methods for the preparation of the requisite ...α-amino ketones substrates are described.
The phosphinamide N-protecting group is an effective directing group for the diastereoselective reduction reactions of proximal ketones.
The effect of the configuration of the phosphorus atom in phosphinamide reduction catalysts has been studied through the preparation and use of a series of catalysts containing stereogenic phosphorus ...atoms of known configuration. The conclusion of this work is that a stereogenic centre at phosphorus can improve the selectivity of reductions using this catalyst, but is not sufficient in itself to generate the higher levels of selectivity which have been achieved with related catalysts. The X-ray crystallographic structure of a key compound is also featured.
Phosphinamide catalysts
7 and
8, containing chiral phosphorus atoms, have been prepared and applied to the asymmetric catalysis of ketone reduction by borane. The X-ray structure of
7 is also featured.
