Ethylene glycol assisted intermolecular Pauson-Khand reaction

The use of ethylene glycol as additive in the N-oxide-promoted intermolecular Pauson-Khand reaction (PKR) has been studied. The addition of 15% ethylene glycol to the reaction mixture consistently increased (from 20% up to 2-4-fold) the reaction yield

P-Stereogenic bisphosphines with a hydrazine backbone: from N-N atropoisomerism to double nitrogen inversion

The synthesis of P-stereogenic bisphosphine ligands starting from a phosphinous acid chiral synthon and hydrazine is reported. The dialkylation of the hydrazine backbone yielded atropo- and nitrogeninversion isomers which are in slow exchange. The crystallization of one of the isomers allowed us to study the reaction kinetics of the equilibria. The new ligands were tested in the Rh catalysed asymmetric hydrogenation of various benchmark substrates attaining up to 99% ee

Rhodium-Catalyzed Pauson−Khand Reaction Using a Small-Bite-Angle P‑Stereogenic C1‑Diphosphine Ligand

The asymmetric Pauson−Khand reaction catalyzed by [Rh(COD)(MaxPHOS)]BF4 is described. Several 1,6-enynes have been chosen as model substrates affording moderate yields and selectivities of up to 86% ee. Besides binap-type ligands, we have demonstrated that the Pstereogenic C1-symmetry small-bite-angle ligand MaxPHOS is a viable ligand in this process. The formation of [2+2+2] cycloaddition compounds has shown to be a competitive process. A mechanism is proposed to account for the observed results. The intermediate rhodium dicarbonyl complex 6 was synthesized, and its solid-state structure was elucidated by X-ray crystallography

Efficient preparation of (S)- and (R)-tert-Butylmethylphosphine-Borane: a novel entry to important P-Stereogenic ligands

A novel one-pot reductive methodol. for the synthesis of optically pure tert-butylmethylphosphine-borane is reported. The prepn. uses as the starting material tert-butylmethylphosphinous acid-borane, which is available in both enantiomeric forms from cis-1,2-aminoindanol and tert-butyldichlorophosphine. The process is based on the redn. of a mixed anhydride, the configurational stability of which has been studied in several solvents and temps. Tetrabutylammonium borohydride was the best reducing agent allowing for the development of a practical process. To demonstrate the utility of the new methodol., the product obtained in this manner was used in the prepn. of Quinox-P*

Asymmetric intermolecular cobalt-catalyzed Pauson-Khand reaction using a p-stereogenic bis-phosphane

The asymmetric intermolecular and catalytic Pauson-Khand reaction has remained an elusive goal since Khand and Pauson discovered this transformation. Using a novel family of P-stereogenic phosphanes, we developed the first catalytic system with useful levels of enantioselection for the reaction of norbornadiene and trimethylsilylacetylene. The results demonstrate that Co-bisphosphane systems are sufficiently reactive and that they lead to high selectivity in the intermolecular process

Borane as an efficient directing group. Stereoselective 1,2-addition of organometallic reagents to borane P-stereogenic N-phosphanylimines

In non-coordinating solvents, borane was shown to be an efficient directing group for the stereoselective 1,2-addition of organolithium reagents to P-stereogenic N-phosphanylimines. Selectivity was reversed in coordinating solvents. This process can lead to novel ligand scaffolds for asymmetric catalysis

Intermediate care: An important contribution to integrate care for older people , in Osona.

Geriatric care, has been playing a key role in the integration of services. Development of intermediate care is a good example. In modern hospitals alternative services to hospitalization had been developed, especially those for elderly patients who are the main users of hospitals. There is an internationally significant interest to create services that occupy the virtual space between primary and hospital care, which is known as intermediate care. The main functions of intermediate care is to provide different options to hospitalization, like preventing admission or easing discharge. The process should last less than 6 weeks and can take place in hospital or at home

Insights into Structure-Activity Relationships of Somatostatin Analogs Containing Mesitylalanine.

The non-natural amino acid mesitylalanine (2,4,6-trimethyl-L-phenylalanine; Msa) has an electron-richer and a more conformationally restricted side-chain than that of its natural phenylalanine counterpart. Taking these properties into account, we have synthesized ten somatostatin analogs containing Msa residues in different key positions to modify the intrinsic conformational flexibility of the natural hormone. We have measured the binding affinity of these analogs and correlated it with the main conformations they populate in solution. NMR and computational analysis revealed that analogs containing one Msa residue were conformationally more restricted than somatostatin under similar experimental conditions. Furthermore, we were able to characterize the presence of a hairpin at the pharmacophore region and a non-covalent interaction between aromatic residues 6 and 11. In all cases, the inclusion of a D-Trp in the eighth position further stabilized the main conformation. Some of these peptides bound selectively to one or two somatostatin receptors with similar or even higher affinity than the natural hormone. However, we also found that multiple incorporations of Msa residues increased the life span of the peptides in serum but with a loss of conformational rigidity and binding affinity