A two-weight Sobolev inequality for Carnot-Carathéodory spaces

Ricerche di Matematica - Let $$X = \{X_1,X_2, \ldots ,X_m\}$$ be a system of smooth vector fields in $${{\mathbb R}^n}$$ satisfying the Hörmander’s finite rank condition. We prove the...     

Expanding the scope of atropisomeric monodentate P-donor ligands in asymmetric catalysis. Asymmetric allylic alkylation of 1,3-diphenylpropenyl-1-esters by Pd/BINEPINE catalysts

Monodentate binaphthophosphepines (BINEPINES) have been tested in the palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenylallyl esters. Stereoselectivities of up to 92% ee have been achieved in the alkylation of the acetate ester with the C-nucleophile, generated in situ by the action of BSA (N,O-bis(trimethylsilyl)acetamide) on dimethylmalonate in the presence of a catalytic amount of sodium acetate.     

Survival of B c mesons in a hot plasma within a potential model

We extend a previous work on the study of heavy charmonia and bottomonia in a deconfined quark-gluon plasma by considering the B _c family of mesons. With the introduction of this bound state of a charm and a beauty quark, we investigate at finite temperature the behavior of the quarkonium, in an energy region between the ψ and the Y states.     

Synthesis and biological evaluation of azido- and aziridino-hydroxyl-beta-lactams through stereo- and regioselective epoxide ring opening

Two new classes of azido- and aziridino-hydroxyl-beta-lactam containing structures have been prepared by means of a stereo- and regioselective epoxide ring opening. The straightforwardness of the procedure makes this strategy useful for the synthesis of potentially bioactive compounds. Some selected examples showed promising activity in acyl CoA-cholesterol acyltransferase inhibition assays.     

Novel biotinylated bile acid amphiphiles: micellar aggregates formation and interaction with hepatocytes

Amphiphilic bile acids linked through an oligoethylene glycol to a biotin moiety were synthesized and shown to create micellar structures in aqueous environment, interact with avidin and be efficiently incorporated into hepatocyte cells, suggesting their potential as a drug delivery system against liver diseases.     

Baryonic masses based on the NJL model

We employ the Nambu-Jona-Lasinio model to determine the vacuum pressure on the quarks in a baryon and hence their density inside. Then we estimate the baryonic masses by implementing the local density approximation for the mean-field quark energies obtained in a uniform and isotropic system. We obtain a fair agreement with the experimental masses. Received: 27 September 2002 / Accepted: 4 October 2002 / Published online: 4 February 2003 RID="a" ID="a"e-mail: giacosa@tphys.physik.uni-tuebingen.de Communicated by A. Molinari     

Expedient stereoselective synthesis of coronafacic acid through intramolecular Diels-Alder cyclization

A stereoselective synthesis of coronafacic acid, a natural component of the phytotoxin coronatin, was achieved using an intramolecular Diels-Alder reaction as the key step. The triene precursor bearing a substituted diene and a vinylketone as dienophile was synthesized and then tested in the thermal intramolecular cyclization. We have devised a new strategy to assemble the E,Z-diene through the stereoselective aldol reaction of an ester enolate followed by a stereoselective dehydration. Following the thermal cyclization, the corresponding hydrindanone thereby obtained with the desired relative stereochemistry could easily be converted into the natural product. The synthesis of the coronafacic acid was accomplished in six steps in 29% overall yield.     

Correction: HCOOH disproportionation to MeOH promoted by molybdenum PNP complexes

Correction for ‘HCOOH disproportionation to MeOH promoted by molybdenum PNP complexes’ by Elisabetta Alberico et al., Chem. Sci., 2021, 12, 13101–13119, DOI: 10.1039/D1SC04181A.

The authors regret that in Scheme 2 of the original article, complexes 7 and 8 were drawn incorrectly. The solid-state structure of both complexes, as established by X-ray analysis, had been previously reported (7 (ref. 1) and 8 (ref. 2)). In both complexes, the PNP ligand adopts a facial tridentate coordination to molybdenum and not a meridional one, as erroneously shown in Scheme 2 of the original article. The correct ligand arrangements in the metal coordination sphere for complexes 7 and 8 are reported below in Scheme 1.Open in a separate windowScheme 1Mo–PNP complexes tested in the dehydrogenation of HCOOH.Open in a separate windowScheme 2Proposed mechanisms for HCOOH dehydrogenation (red), disproportionation (blue) and decarbonylation (green) promoted by 5. Evidence for the formation of a Mo(iv) species is based on the detection by NMR of H₂ and HD following addition of DCOOD to Mo(H)_n species (see Fig. SI-31).Please note that complex 8 is also shown in Scheme 4 in the proposed mechanism for HCOOH decarbonylation (green part), and in Fig. 2. In both cases, the correct structure for complex 8 is reported below in Scheme 2 and Fig. 1.Open in a separate windowFig. 1 ¹H and ³¹P{¹H} NMR spectra of a toluene-d₈ solution of {Mo(CH₃CN)(CO)₂(HN[(CH₂CH₂P)(CH(CH₃)₂)₂]₂} 4 in the presence of 100 equivalents of HCOOH ([Mo] 10⁻² M, [HCOOH] 1 M), before (a) and after heating at 90 °C for 1 hour (b). Spectra were recorded at room temperature. Signals related to complex 5 are marked by red dots.Open in a separate windowFig. 2Molecular structure of {Mo(CO)₂(CH₃CN)[CH₃N(CH₂CH₂P(CH(CH₃)₂)₂)₂]} 9. Displacement ellipsoids correspond to 30% probability. Hydrogen atoms are omitted for clarity.Furthermore, a mistake was made in the caption of Fig. 6, showing the solid-state structure of complex 9: the latter has been incorrectly described as a Mo(i)-hydride species {Mo(H)(CO)₂(CH₃CN)[CH₃N(CH₂CH₂P(CH(CH₃)₂)₂)₂]}. The correct formula, in agreement with the X-ray structure, is as follows and is shown above in Fig. 2: {Mo(CO)₂(CH₃CN)[CH₃N(CH₂CH₂P(CH(CH₃)₂)₂)₂]}.The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.