Structure and atropisomerisation of new diastereomeric gossypol Schiff bases with (R)-(+)-2-amino-3-benzyloxy-1-propanol studied by NMR,ECD and DFT methods

Gossypol Schiff base with (R)-(+)-2-amino-3-benzyloxy-1-propanol 1 was synthesised and resolved by HPLC method into diastereomers to study their atropisomerisation process. The spectroscopic analysis performed by one- and two-dimensional NMR, UV–vis and FT-IR methods indicated that the compound exists in solution as an enamine-oxo tautomer. The ECD measurements and TD-DFT calculations allowed us to unambiguously determine the configuration about the axially chiral biaryl moiety of 1. The conditions of the atropisomerisation processes of diastereopure gossypol Schiff bases (S_AX,R)-1 and (R_AX,R)-1 were determined on the basis of ECD and NMR measurements. Exposure of the diastereomers of 1 to sunlight and to the light at λ = 254 nm significantly accelerated the atropisomerisation when compared to its rate in the dark.     

Optimal and one-complemented subspaces

Let X be a real Banach space and let V ⊂ X be a closed linear subspace. In [4, Prop. 5] it has been proven that if X is strictly convex, reflexive and smooth and V is an optimal subset of X then V is one-complemented in X. In this note we would like to extend this result to non-smooth Banach spaces. In particular, we show that any existence subspace of c,c _o and l ₁ is one-complemented. Also some results concerning non-smooth Musielak-Orlicz sequence spaces equipped with the Luxemburg norm will be presented. The first author was supported by Polish State Committee for Scientific Research Grant KBN 1 PO3A O10 26. Authors’ addresses: Grzegorz Lewicki, Department of Mathematics, Jagiellonian University, 30-059 Kraków, Reymonta 4, Poland; Giulio Trombetta, Department of Mathematics, University of Calabria, 87036 Arcavacata di Rende, Cosenza, Italy     

Asymptotic Behavior of Factorization and Projection Constants

This paper is concerned with estimates of important factorization constants that appear in Banach space theory. We prove upper bounds of the Hilbertian norm of projections on finite-dimensional spaces of interpolation spaces generated by certain abstract interpolation functors and show applications to Calderón–Lozanovskii spaces. We also prove estimates of the p-factorization norm and projection constants for finite-dimensional Banach lattices. We show as a consequence of our results that in a large class of n-dimensional Banach sequence lattices \(E_n\) the projection constants \(\lambda (E_n)\) satisfy \(\lim _{n\rightarrow \infty }\lambda (E_n)/\sqrt{n} = c\), where \(c=\sqrt{2/\pi }\) in the real case and \(c= \sqrt{\pi }/2\) in the complex case. Applications are given to vector-valued sequence spaces.     

Derived Equivalence Classification of the Gentle Two-Cycle Algebras

We complete a derived equivalence classification of the gentle two-cycle algebras initiated in earlier papers by Avella-Alaminos and Bobinski–Malicki.     

Non-linear Heat and Mass Transfer During Convective Drying of Kaolin Cylinder Under Non-steady Conditions

The self-consistent model of heat and mass transfer during convective drying of capillary porous media describing both the first and the second periods of drying is presented in Musielak (Wydawnictwo Politechniki Poznańskiej, seria Rozprawy, nr 386 (2004a); Chem. Process Eng. 25, 393–409 (2004b)). The results of simulations of processes in steady conditions are shown (Musielak Wydawnictwo Politechniki Poznańskiej, seria Rozprawy, nr 386 (2004a); Chem. Process Eng. 25, 393–409 (2004b)). The main aim of the present work is to compare experimental results with those from numerical simulations. Three convective drying processes have been performed experimentally. The first and the second periods of drying are considered, during which the humidity of air in the dryer changes due to evaporation. The first process is used to establish drying parameters, whereafter the two remaining processes are simulated. Good agreement between experimental and simulation results is found, both qualitative and quantitative.     

Spherical silica particles decorated with graphene oxide nanosheets as a new sorbent in inorganic trace analysis

Graphene oxide (GO) is a novel material with excellent adsorptive properties. However, the very small particles of GO can cause serious problems is solid-phase extraction (SPE) such as the high pressure in SPE system and the adsorbent loss through pores of frit. These problems can be overcome by covalently binding GO nanosheets to a support. In this paper, GO was covalently bonded to spherical silica by coupling the amino groups of spherical aminosilica and the carboxyl groups of GO (GO@SiO₂). The successful immobilization of GO nanosheets on the aminosilica was confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy. The spherical particle covered by GO with crumpled silk wave-like carbon sheets are an ideal sorbent for SPE of metal ions. The wrinkled structure of the coating results in large surface area and a high extractive capacity. The adsorption bath experiment shows that Cu(II) and Pb(II) can be quantitatively adsorbed at pH 5.5 with maximum adsorption capacity of 6.0 and 13.6 mg g⁻¹, respectively. Such features of GO nanosheets as softness and flexibility allow achieving excellent contact with analyzed solution in flow-rate conditions. In consequence, the metal ions can be quantitatively preconcentrated from high volume of aqueous samples with excellent flow-rate. SPE column is very stable and several adsorption–elution cycles can be performed without any loss of adsorptive properties. The GO@SiO₂ was used for analysis of various water samples by flame atomic absorption spectrometry with excellent enrichment factors (200–250) and detection limits (0.084 and 0.27 ng mL⁻¹ for Cu(II) and Pb(II), respectively).     

Synthesis of new dendrimers—trimesic acid derivatives

The efficient synthesis of new dendrimeric polyesters up to generation 3 that consist of 1,3,5-benzenetricarboxylic acid building blocks with potential applications in drug delivery is described. The dendrimers possess hydroxy or allyl functional groups on the surface and were prepared through a divergent approach using readily available 2-(hydroxymethyl)-2-ethylpropan-1,3-diol and 1,3,5-benzenetrimethanol as central cores, with 3,5-bis[(allyloxy)methyl]benzoic acid being an essential unit of the dendrimer. The latter compound was synthesized, in high yield, from 1,3,5-benzenetricarboxylic acid, applying selective hydrolysis of the corresponding triester as the key step.     

The frequently overlooked importance of solvent in free radical syntheses

This tutorial review is designed to dispel the myth, still believed by many synthetic organic chemists, that radical-based syntheses are free from significant solvent effects. However, many synthetically valuable radical reactions do exhibit large kinetic solvent effects. It is therefore important to select the solvent for any proposed radical synthesis with considerable care if good product yields are to be achieved.