Search results for "azetidine"

Evidence of a 1,4-dipole intermediate in the reaction of 1-phenyl-4-vinylpyrazole with ptad

1985

Abstract 1-Phenyl-4-vinylpyrazole reacts with 1-phenyl-1,2,4-triazoline-3,5-dione in methylene chloride to form an unstable azetidine (4). An intermediate 1,4-dipole is probably involved since, when the reaction is conducted in acetone, a 1:1:1 adduct (3) is isolated.

The efficacy and safety of ezetimibe/simvastatin combination compared with intensified lipid-lowering treatment strategies in diabetic subjects with …

2012

Aims The objective was to assess the consistency of effect of switching to ezetimibe/simvastatin 10/20 mg versus doubling the baseline statin dose (to simvastatin 40 mg or atorvastatin 20 mg) or switching to rosuvastatin 10 mg across subgroups of subjects with (n = 617) and without (n = 191) metabolic syndrome (MetS). Methods This was a post hoc analysis of a randomized, double-blind, 6-week study of adults 18–79 years with cardiovascular disease and diabetes mellitus with low-density lipoprotein cholesterol (LDL-C) ≥70 and ≤160 mg/dl. The percent change in LDL-C and other lipids was estimated within each subgroup separately. Safety and tolerability were assessed. Results In subjects with M…

Water-Assisted Alkaline Hydrolysis of Monobactams: A Theoretical Study

2002

A theoretical study of the water-assisted alkaline hydrolysis of 2-azetidinone, 3-formylamino-2-azetidinone and 3-formylamino-2-azetidine-1-sulfonate ion is carried out at the B3LYP/6-31+G* level. The effect of bulk solvent is taken into account using the PCM solvation model while specific solvent effects are represented by the inclusion of an ancillary water molecule along the reaction profile. The calculated free energy barriers in solution are in reasonable agreement with experimental values. The observed substituent effects due to the presence of the 3-formylamino and the SO(3) groups attached to the beta-lactam ring are crucial factors determining the hydrolysis of monobactam antibioti…

Efficacy and safety of ezetimibe added to atorvastatin versus atorvastatin uptitration or switching to rosuvastatin in patients with primary hypercho…

2013

Hypercholesterolemic patients (n = 1,547) at high atherosclerotic cardiovascular disease risk with low-density lipoprotein cholesterol (LDL-C) levels ≥100 and ≤160 mg/dl while treated with atorvastatin 10 mg/day entered a multicenter, randomized, double-blind, active-controlled, clinical trial using two 6-week study periods. Period I compared the efficacy/safety of (1) adding ezetimibe 10 mg (ezetimibe) to stable atorvastatin 10 mg, (2) doubling atorvastatin to 20 mg, or (3) switching to rosuvastatin 10 mg. Subjects in the latter 2 groups who persisted with elevated LDL-C levels (≥100 and ≤160 mg/dl) after period I, entered period II; subjects on atorvastatin 20 mg had ezetimibe added to th…

Theoretical Study on the Photo-Oxidation and Photoreduction of an Azetidine Derivative as a Model of DNA Repair

2021

Photocycloreversion plays a central role in the study of the repair of DNA lesions, reverting them into the original pyrimidine nucleobases. Particularly, among the proposed mechanisms for the repair of DNA (6-4) photoproducts by photolyases, it has been suggested that it takes place through an intermediate characterized by a four-membered heterocyclic oxetane or azetidine ring, whose opening requires the reduction of the fused nucleobases. The specific role of this electron transfer step and its impact on the ring opening energetics remain to be understood. These processes are studied herein by means of quantum-chemical calculations on the two azetidine stereoisomers obtained from photocyc…

Stereocontrolled synthesis of azeto[2,1-b] quinazolines bearing three stereocenters via the intramolecular [2+2] cycloaddition between ketenimines an…

2004

Abstract A highly stereoselective synthesis of azeto[2,1- b ]quinazolines bearing three stereocenters (C1, C2, and C8) has been achieved via intramolecular [2+2] cycloaddition between ketenimine and imine functions supported on an ortho -benzylic scaffold. An asymmetric center adjacent to the iminic nitrogen atom, the future C8 carbon of the bicyclic product, efficiently controls the absolute configuration of the two new stereogenic carbon atoms of the azetidine ring, C1 and C2.

Lipid-altering efficacy of switching to ezetimibe/simvastatin 10/20 mg versus rosuvastatin 10 mg in high-risk patients with and without metabolic syn…

2011

Metabolic syndrome (MetS) is a clustering of atherosclerotic coronary heart disease risk factors. This post-hoc analysis compared the effects of switching to ezetimibe/simvastatin 10/20 mg or rosuvastatin 10 mg in a cohort of 618 high-risk hypercholesterolaemic patients with ( n=368) and without ( n=217) MetS who had previously been on statin monotherapy. Patients were randomised 1:1 to double-blind ezetimibe/simvastatin 10/20 mg or rosuvastatin 10 mg for 6 weeks. Least squares mean percent change from baseline and 95% confidence intervals in lipid efficacy parameters were calculated for the population and within subgroups. Treatment with ezetimibe/simvastatin was significantly more effect…

Five-Membered Heterocyclic Rings and Their Fused Derivatives

2015

Ring splitting of azetidin-2-ones via radical anions

2012

The radical anions of azetidin-2-ones, generated by UV-irradiation in the presence of triethylamine, undergo ring-splitting via N-C4 or C3-C4 bond breaking, leading to open-chain amides. This reactivity diverges from that found for the neutral excited states, which is characterised by alpha-cleavage. The preference for beta-cleavage is supported by DFT theoretical calculations on the energy barriers associated with the involved transition states. Thus, injection of one electron into the azetidin-2-one moiety constitutes a complementary activation strategy which may be exploited to produce new chemistry.

Asymmetric synthesis of α,β-diamino acid derivatives with an aziridine-, azetidine- and γ-lactone-skeleton via Mannich-type additions across α-chloro…

2012

The efficient asymmetric synthesis of new chiral γ-chloro-α,β-diamino acid derivatives via highly diastereoselective Mannich-type reactions of N-(diphenylmethylene) glycine esters across a chiral α-chloro-N-p-toluenesulfinylimine was developed. The influence of the base, LDA or LiHMDS, used for the formation of the glycine enolates, was of great importance for the anti-/syn-diastereoselectivity of the Mannich-type reaction. The γ-chloro-α,β-diamino acid derivatives proved to be excellent building blocks for ring closure towards optically pure anti- and syn-β,γ-aziridino-α-amino esters, and subsequent ring transformation into trans-3-aminoazetidine-2-carboxylic acid derivatives and α,β-diami…