An efficient protocol for regioselective ring opening of epoxides using sulfated tungstate: application in synthesis of active pharmaceutical ingredients atenolol, propranolol and ranolazine

Hydrogen Bonds and n → π* Interactions in the Acetylation of Propranolol Catalyzed by Candida antarctica Lipase B: A QTAIM Study

Enzyme-substrate interactions play a crucial role in enzymatic catalysis. Quantum theory of atoms in molecules (QTAIM) calculations are extremely useful in computational studies of these interactions because they provide very detailed information about the strengths and types of molecular interactions. QTAIM also provides information about the intramolecular changes that occur in the catalytic reaction. Here, we analyze the enzyme-substrate interactions and the topological properties of the electron density in the enantioselective step of the acylation of (R,S)-propranolol, an aminoalcohol with therapeutic applications, catalyzed by Candida antarctica lipase B. Eight reaction paths (four for each enantiomer) are investigated and the energies, atomic charges, hydrogen bonds, and n → π* interactions of propranolol, the catalytic triad (composed of D187, H224, and S105), and the oxyanion hole are analyzed. It is found that D187 acts as an electron density reservoir for H224, and H224 acts as an electron density reservoir for the active site of the protein. It releases electron density when the tetrahedral intermediate is formed from the Michaelis complex and receives it when the enzyme-product complex is formed. Hydrogen bonds can be grouped into noncovalent and covalent hydrogen bonds. The latter are stronger and more important for the reaction than the former. We also found weak n → π* interactions, which are characterized by QTAIM and the natural bond orbital (NBO) analysis.

Ln(OTf)3-catalysed highly regioselective alcoholysis of 2,3-epoxy alcohols

Regioselectivity of Ln(OTf)3-catalysed alcoholysis of 2,3- and 3,4-epoxy alcohols was closely investigated to expand the scope of the transformations. The synthetic use was demonstrated by application to the construction of 4-propoxy-5-hydroxy-2,3-pentanedione (C4-propoxy-HPD), which is a potent synthetic mediator in AI-2 quorum sensing.

Cu(2+), Zn(2+), and Ni(2+) Complexes of C2-Symmetric Pseudopeptides with an Aromatic Central Spacer

Two new tetradentate C2-symmetric pseudopeptidic ligands derived from Val and Phe containing two amino and two amido groups and a central o-substituted aromatic spacer have been prepared. Their complexes with Cu(2+), Zn(2+), and Ni(2+) have been studied by potentiometry, UV-vis spectrophotometry, FT-IR, and ESI-MS. The presence of the aromatic spacer provides Cu(2+) complexes with stability constants several orders of magnitude higher than those observed for related ligands containing aliphatic central spacers. Besides, the formation of [MH-2L] complex species is favored. Crystal structures for the corresponding Cu(2+) and Ni(2+) have been obtained, revealing the metal atom in an essentially square-planar geometry, although, in several instances, the oxygen atom of an amide carbonyl of a second complex species can act as a fifth coordination site. In the case of Zn(2+), the only crystal structure obtained displays a square-pyramidal arrangement of the metal center. Finally, preliminary experiments show the catalytic activity of some of these complexes, in particular, Zn(2+) complexes, for epoxide ring-opening with using aniline as the nucleophile in a ligand accelerated process.

Synthesis of β-phthalimido-alcohols via regioselective ring opening of epoxide by using reusable basic magnetic nano particles and their biological investigation

In this work, regioselective ring opening of epoxides including aromatic and aliphatic epoxides to give β-phthalimido-alcohols has been reported.

In silico approach towards lipase mediated chemoenzymatic synthesis of (S)-ranolazine, as an anti-anginal drug

An in silico modelling based biocatalytic approach for the synthesis of drugs and drug intermediates in enantiopure forms is a rationalized methodology over the organo-chemical routes.

Enantioselective syntheses of β-amino alcohols catalyzed by recyclable chiral Fe(iii) metal complex

An efficient asymmetric desymmetrization of meso-epoxides with anilines catalyzed by a series of simple and environmentally benign in situ generated Fe(iii) complexes based on chiral tridentate ligands L1–L7 was carried out at rt.

Lipase-catalyzed green synthesis of enantiopure atenolol

A new green route is proposed for the synthesis of enantiopure atenolol (a β₁-blocker).

Tungsten-catalyzed regioselective and stereospecific ring opening of 2,3-epoxy alcohols and 2,3-epoxy sulfonamides

The first catalytic, highly C3-selective, stereosepecific ring-opening reaction of 2,3-epoxy alcohols and 2,3-epoxy sulfonamides has been accomplished. This process was efficiently promoted by W-salts, and the developed method was applicable to various epoxides with diverse N- and O-nucleophiles affording the products in good to excellent yields (up to 95%) and generally with high regioselectivities (C3:C2 up to >99:1).