Complementary Specificity of Unspecific Peroxygenases (UPOs) Enables Access to Diverse Products from Terpene Oxygenation

Unspecific Peroxygenases (UPOs) have emerged as attractive biocatalysts for selective oxygenations as, unlike cytochromes P450, they can be employed as easy-to-use lyophilised powders and depend only upon hydrogen peroxide as the external oxidant. The application of UPOs to a range of synthetic challenges relies on the characterisation of activity and specificity of complementary enzymes. Here we show that two UPOs, artUPO and rAaeUPO-PaDa-I-H, which are representative members of the ‘short’ Family I and ‘long’ Family II UPOs, display complementary activity in a series of scalable, preparative biotransformations of a diverse array of terpenes. The UPOs were also applied to the biotransformation of chrysanthemic acid derived fragments relevant in the agrichemical industry, culminating in the highly diastereoselective and enantioselective oxidation of a racemic synthetic pyrethroid derivative via kinetic resolution

Late Pleistocene-Holocene coastal adaptation in central Mediterranean: Snapshots from Grotta d’Oriente (NW Sicily)

Marine faunal remains from Grotta d’Oriente (Favignana Island, NW Sicily) offer invaluable snapshots of human-coastal environment interaction in the central Mediterranean from the Late Pleistocene to the Middle Holocene. The long-term shellfish and fish records reflect human exploitation of coastal environments undergoing considerable reorganizations during the postglacial sea level rise and the progressive isolation of Favignana from mainland Sicily. We detected an intensification of marine resource exploitation between ∼9.6 ka and ∼7.8 ka BP, which corresponds with the isolation of Favignana Island and, later on, with the introduction of early agro-pastoral economy in this region. We suggest that a higher investment in marine resource exploitation by late foragers and early farmers in NW Sicily was also supported by an increase in marine productivity in the south Tyrrhenian Sea in the Middle Holocene

Oxidative addition of N-halosuccinimides to palladium(0): The discovery of neutral palladium(II) imidate ligands, which enhance Stille coupling of allylic and benzylic halides

The Stille coupling of organostannanes and organohalides, mediated by air and moisture stable palladium(II) phosphine complexes containing succinimide or phthalimide (imidate) ligands, has been investigated. An efficient synthetic route to several palladium(II) complexes containing succinimide and phthalimide ligands, has been developed. cis-Bromobis(triphenylphosphine)(N-succinimide)palladium(II) [(Ph3P)2Pd(N-Succ)Br] is shown to mediate the Stille coupling of allylic and benzylic halides with alkenyl, aryl and allyl stannanes. In competition experiments between 4-nitrobromobenzene and benzyl bromide with a cis-stannylvinyl ester, (Ph3P)2Pd(N-Succ)Br preferentially cross-couples benzyl bromide, whereas with other commonly employed precatalysts 4-nitrobromobenzene undergoes preferential cross-coupling. Furthermore, preferential reaction of deactivated benzyl bromides over activated benzyl bromides is observed for the first time. The type of halide and presence of a succinimide ligand are essential for effective Stille coupling. The type of phosphine ligand is also shown to alter the catalytic activity of palladium(II) succinimide complexes

A versatile, non-biomimetic route to the preussomerins: syntheses of (+ -)-preussomerins F, K and L

The first total syntheses of the title fungal metabolites preussomerins F, K and L are described and their structures confirmed thereby. The syntheses were achieved following a versatile, unified, non-biomimetic approach, which is easily extendable to prepare other known and novel members of this family. Key steps include the functionalisation of a 2-arylacetal anion, tandem one-pot Friedel–Crafts cyclisation–deprotection, regioselective substrate-directable hydrogenation and reductive-opening of epoxides

Mesogenic, trimeric, halogen-bonded complexes from alkoxystilbazoles and 1,4-dihalotetrafluorobenzene

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Experimental and computational studies of structure and bonding in parent and reduced forms of the azo dye Orange II

The structure and bonding of the azo dye Orange II (Acid Orange 7) in parent and reduced forms have been studied using NMR, infrared, Raman, UV−visible, and electron paramagnetic resonance (EPR) spectroscopy, allied with density functional theory (DFT) calculations on three hydrazone models (no sulfonate, anionic sulfonate, and protonated sulfonate) and one azo model (protonated sulfonate). The calculated structures of the three hydrazone models are similar to each other and that of the model without a sulfonate group (Solvent Yellow 14) closely matches its reported crystal structure. The 1H and 13C NMR resonances of Orange II, assigned directly from 1D and 2D experimental data, indicate that it is present as ≥95% hydrazone in aqueous solution, and as a ca. 70:30 hydrazone:azo mixture in dimethyl sulfoxide at 300 K. Overall, the experimental data from Orange II are matched well by calculations on the hydrazone model with a protonated sulfonate group; the IR, Raman, and UV−visible spectra of Orange II are assigned to specific vibrational modes and electronic transitions calculated for this model. The EPR spectrum obtained on one-electron reduction of Orange II by the 2-hydroxy-2-propyl radical (•CMe2OH) at pH 4 is attributed to the hydrazyl radical produced on protonation of the radical anion. Calculations on reduced forms of the model dyes support this assignment, with electron spin density on the two nitrogen atoms and the naphthyl ring; in addition, they provide estimates of the structures, vibrational spectra, and electronic transitions of the radicals

Phosphinite Ligand Effects in Palladium(II)-Catalysed Cycloisomerisation of 1,6-Dienes: Bicyclo[3.2.0]heptanyl Diphosphinite (B[3.2.0]DPO) Ligands Exhibit Flexible Bite Angles, an Effect Derived from Conformational Changes (exo- or endo-Envelope) in the Bicyclic Ligand Scaffold

Changes in bidentate ligand structure significantly affect catalytic activity in mono-cationic Pd(II)-catalysed 1,6-diene cycloisomerisation processes to give cyclopentene products. A bicyclo[3.2.0]heptanyl diphosphinite ligand (B[3.2.0]DPO, 3) is the first phosphorus-based bidentate ligand capable of promoting regioselective 1,6-diene cycloisomerisation. Trace quantities of water are essential for catalytic activity, as is the precise order of mixing of 1,6-diene, Pd(II) pro-catalyst and additives. Conformational changes in the ligand backbone seem to be important in stabilising the active catalyst species, assumed to be a cationic Pd(II) hydride species. DFT calculations support a change in bite angle on the cationic Pd(II) hydride species from circa 90° (cis) to 170° (trans); in the latter geometry an agostic interaction of the C4 endo hydrogen of the bicyclic ring-system with Pd(II) stabilises the cationic metal centre. This unique ligand property could be exploited in other transition metal catalysed processes

A new reaction pathway in organophosphorus chemistry: competing SN2- and AE'-pathways for nucleophilic attack at a phosphorus-cage compound

Competition: A combination of 31P NMR spectroscopic and calculational studies have shown that nucleophilic substitution in the phosphorus-carbon cage compound ClP3(CtBu)2 occurs through competing SN2- and AE-type reaction pathways (see scheme for model compound ClP3(CH)2). The AE mechanism results in the formation of a C2v-symmetric intermediate prior to release of the chloride ion