New Synthesis of Natural Carotene Isorenieratene (ϕ,ϕ‐Carotene) and its 3,3′‐Dimethoxy Analogue

The main pigments of Brevibacterium linens are the aromatic carotenoids 3,3′‐dihydroxyisorenieratene (φ,φ‐carotene‐3,3′‐diol), the corresponding monohydroxy compound, and the hydrocarbon isorenieratene. We report herein new syntheses of isorenieratene (?,?‐carotene) and its xanthophyll analogue, 3,3′‐dimethoxy‐?,?‐carotene, which may be considered a protected form of the natural xanthophyll, 3,3′‐dihydroxy‐?,?‐carotene.     

Metal-organic frameworks based on trigonal prismatic building blocks and the new "acs" topology

Cationic and mixed-valent forms of Fe3O(CO2)6 trigonal prismatic clusters have been linked by ditopic links, namely, 1,4-benzenedicarboxylate (1,4-BDC) and 1,3-benzenedicarboxylate (1,3-BDC), to produce two 3-periodic metal-organic frameworks (MOFs), [Fe3O(1,4-BDC)3 (DMF)3][FeCl4] x (DMF)3 (MOF-235) and Fe3O(1,3-BDC)3 (py)3 x (py)0.5(H2O)1.5 (MOF-236) (DMF = N,N-dimethylformamide, py = pyridine), respectively. These MOFs exemplify a new, high-symmetry topology termed acs which we identify here as the default arrangement for linking trigonal prisms together.     

Didecarboxylative Iron‐Catalyzed Bidirectional Aldolization towards Diversity‐Oriented Ketodiol Synthesis

1,3‐Acetonedicarboxylic acid was selectively activated by Fe(acac)₃, providing a synthetic platform for rapid synthesis of keto‐3,3′‐diols. The bidirectional aldol reaction was efficient for challenging aliphatic aldehydes, providing a rapid route to potentially bioactive complex structures.     

Grafting of Lanthanum Complexes on a Functionalized Graphene Surface: Theoretical Investigation on Ethylene and 1,3-Butadiene Homo- and Co-Polymerization

In this contribution, we describe the use of graphene as an efficient catalyst support and the role it plays in increasing the Lewis acidity of the supported metal complexes. By a density functional theory study, we show that the [La(N(SiMe₃)₂)₃] complex can be easily grafted on graphene-OH and -COOH functionalized surfaces. Two stable mono-grafted compounds, (gO)-[La(N(SiMe₃)₂)₂] and (gOO)-[La(N(SiMe₃)₂)₂], are formed, behaving as stronger Lewis acids than the previously reported silica grafted analogues. To study the role of the graphene support in catalysis, we also computed the catalytic activity of the alkylated (gO)-[La(CH₃)₂] and (gOO)-[La(CH₃)₂] complexes in the ethylene and 1,3-butadiene homo- and co-polymerization reactions. Both compounds are efficient catalysts for the homo-polymerization of the ethylene and 1,3-butadiene. For the 1,3-butadiene homo-polymerization, the stereoselectivity outcome of the reaction differs according to the grafting site. The results computed for the co-polymerization reaction, finally, show that the high stability of the allylic products leads to the formation of block copolymers.     

A note on super-hedging for investor–producers

We study the situation of an agent who can trade on a financial market and can also transform some assets into others by means of a production system, in order to price and hedge derivatives on produced goods. This framework is motivated by the case of an electricity producer who wants to hedge a position on the electricity spot price and can trade commodities which are inputs for his system. This extends the essential results of Bouchard and Nguyen (Math Finance, 2011) to continuous time markets. We introduce the generic concept of conditional sure profit along the idea of the no sure profit condition of Rásonyi (Optimality and risk-modern trends in mathematical finance: the Kabanov Fetschrift, 2009). The condition allows one to provide a closedness property for the set of super-hedgeable claims in a very general financial setting. Using standard separation arguments, we then deduce a dual characterization of the latter and provide an application to power futures pricing.     

Asymmetric aziridination with chiral allyl aminosulfoxonium ylides: synthesis of alkenyl aziridine carboxylates and palladium-catalyzed E,trans/E,cis-isomerization of an alkenyl aziridine

Chiral cyclic and acyclic allyl aminosulfoxonium ylides have been generated from aminosulfoxonium-substituted β,γ-unsaturated α-amino acids (method A) and 1-alkenyl aminosulfoxonium salts (method B) upon treatment with DBU. Their application to the asymmetric aziridination of N-tert-butyl-sulfonyl imino ester, generated either in situ (method A) or externally added (method B), gave the corresponding alkenyl aziridine carboxylates with medium to high diastereoselectivity and enantioselectivity. A highly stereoselective Pd(0)-catalyzed isomerization of an E,trans-configured alkenyl aziridine methanol derivative to its E-cis-isomer is described, which proceeded with retention of the double bond configuration.     

Dendritic Iron(II) Porphyrins as Models for Hemoglobin and Myoglobin: Specific Stabilization of O2 Complexes in Dendrimers with H‐Bond‐Donor Centers

Two types of dendritically functionalized iron(II) porphyrins were prepared (Scheme) and investigated in the presence of 1,2‐dimethylimidazole (1,2‐DiMeIm) as the axial ligand as model systems for T(tense)‐state hemoglobin (Hb) and myoglobin (Mb). Equilibrium O₂‐ and CO‐binding studies were performed in toluene and aqueous phosphate buffer (pH 7). UV/VIS Titrations (Fig. 4) revealed that the two dendritic receptors 1 ⋅ Fe ^II ‐1,2‐DiMeIm and 2 ⋅ Fe ^II ‐1,2‐DiMeIm (Fig. 2) with secondary amide moieties in the dendritic branching undergo reversible complexation (Fig. 5) with O₂ and CO in dry toluene. Whereas the CO affinity is similar to that measured for the natural receptors, the O₂ affinity is greatly enhanced and exceeds that of T‐state Hb by a factor of ca. 1500 (Table). The oxygenated complexes possess half‐lives of several h (Fig. 6). This remarkable stability originates from both dendritic encapsulation of the iron(II) porphyrin and formation of a H‐bond between bound O₂ and a dendritic amide NH moiety (Fig. 11). Whereas reversible CO binding was also observed in aqueous solution (Fig. 10), the oxygenated iron(II) complexes are destabilized by the presence of H₂O with respect to oxidative decay (Fig. 9), possibly as a result of the weakening of the O₂⋅⋅⋅H−N H‐bond by the competitive solvent. The comparison between the two dendrimers with amide branchings and ester derivative 3 ⋅ Fe ^II ‐1,2‐DiMeIm (Fig. 2), which lacks H‐bond donor centers in the periphery of the porphyrin, further supports the role of H‐bonding in stabilizing the O₂ complex against irreversible oxidation. All three derivatives bind CO reversibly and with similar affinity (Fig. 8) in dry toluene, but the oxygenated complex of 3 ⋅ Fe ^II ‐1,2‐DiMeIm undergoes much more rapid oxidative decomposition (Fig. 7).     

On the singular set of the parabolic obstacle problem

This paper is devoted to regularity results and geometric properties of the singular set of the parabolic obstacle problem with variable right-hand side. Making use of a monotonicity formula for singular points, we prove the uniqueness of blow-up limits at singular points. These results apply to parabolic obstacle problem with variable coefficients.