Stereoselective synthesis of (Z)-alpha-halo-alpha,beta-unsaturated esters, and amides from aldehydes and trihaloesters or amides promoted by manganese

Preliminary results of a Mn-promoted sequential process directed toward the stereoselective synthesis of different (Z)-alpha-halo-alpha,beta-unsaturated compounds are described.     

Simultaneous Flow Injection Analysis of Paracetamol and Ascorbic Acid with Multiple Pulse Amperometric Detection

The present work reports a simple and quick strategy for simultaneous determination of paracetamol (PC) and ascorbic acid (AA) in pharmaceutical formulations using flow injection method with multiple pulse amperometric detection. The method allows the resolution of the mixture without chemical pretreatment of the sample or electrode modification or the use of chemometric techniques for data analysis. The compounds are detected by applying four sequential pulses (waveform) in function of time to a three‐electrode amperometric system that uses a wall‐jet cell with gold as working electrode. AA is direct detected at +0.40 V and PC is indirectly detected at 0.0 V by the reduction (desorption) of the oxidation product (N‐acetyl‐p‐benzoquinoneimine) electrochemically generated at +0.65 V. The fourth potential pulse (?0.05 V) is applied for the complete regeneration (cleaning) of the gold electrode surface. The linear response range was optimized between 5 and 24 mg L^?1 for AA and 50 and 240 mg L^?1 for PC. The difference between the two responses ranges (10‐fold) present correlation with the concentration of these compounds in two different pharmaceutical formulations available in the Brazilian market. The analytical frequency was calculated in 60 injections per hour. The use of the proposed methodology for PC quantification in the presence of higher AA concentrations was also carried out. Using the standard addition method, it was possible to detect PC in trace levels (LD=0.2 mg L^?1) in the presence of 880‐fold more of AA (176 mg L^?1).     

Differential Equations with Infinitely Many Derivatives and the Borel Transform

Differential equations with infinitely many derivatives, sometimes also referred to as “nonlocal” differential equations, appear frequently in branches of modern physics such as string theory, gravitation and cosmology. We properly interpret and solve linear equations in this class with a special focus on a solution method based on the Borel transform. This method is a far-reaching generalization of previous studies of nonlocal equations via Laplace and Fourier transforms, see for instance (Barnaby and Kamran, J High Energy Phys 02:40, 2008; Górka et al., Class Quantum Gravity 29:065017, 2012; Górka et al., Ann Henri Poincaré 14:947–966, 2013). We reconsider “generalized” initial value problems within the present approach and we disprove various conjectures found in modern physics literature. We illustrate various analytic phenomena that can occur with concrete examples, and we also treat efficient implementations of the theory.     

Asymmetric synthesis of 3,4-anti- and 3,4-syn-substituted aminopyrrolidines via lithium amide conjugate addition

The diastereoselective conjugate addition of homochiral lithium amides to methyl 4-(N-allyl-N-benzylamino)but-2-enoate has been used as the key step in a simple and efficient protocol for the preparation of 3,4-substituted aminopyrrolidines. This protocol provides a complementary and stereoselective route to both anti- and syn-3-amino-4-alkylpyrrolidines as well as anti- and syn-3-hydroxy-4-aminopyrrolidines, in high de and ee viabeta-amino enolate functionalisation. This methodology has been applied to the synthesis of anti-(3S,4S)- and syn-(3R,4S)-3-methoxy-4-(N-methylamino)pyrrolidine.