Lidija Barišić

Ferrocene compounds ☆: Part XXXIII. Synthesis and characterization of amino acids containing skeletal 1,1′-ferrocenylene unit

Abstract The syntheses of 1′-(3-aminopropyl)ferrocene-1-carboxylic acid (7), 1′-amino-1-ferrocenebutyric acid (14) and their derivatives are reported. Reactions of 1′-methoxycarbonyl-1-ferrocenebutyric acid (3) or methyl 1′-carboxy-1-ferrocenebutyrate (10) with ethyl chloroformate/triethylamine/sodium azide gave methyl 1′-(3-azidocarbonylpropyl)ferrocene-1-carboxylate (4) and methyl 1′-azidocarbonyl-1-ferrocenebutyrate (11). These azides were rearranged by heating in acetic anhydride and hydrolyzed into N-acetyl derivatives of 7 and 14. The crucial intermediates 4 and 11 were transformed by the action of t-BuOH into Boc-7 and Boc-14. The crystal and molecular structures of the intermediates methyl 1′-(3-acetamidopropyl)ferrocene-1-carboxylate (5) and tert-butyl 1′-(3-methoxycarbonylpropyl)-1-ferrocenecarbamate (15) have been determined by the single crystal X-ray analysis. Compound 5 crystallizes in two polymorphic forms (5a and 5b); one of them (5b) contains two crystallographically independent molecules. The molecules 5a and 5b differentiate only in the conformation of (CH2)3NHAc part of the molecules exhibiting conformational polymorphism. The crystal structure is dominated by the intermolecular hydrogens bonds of NH⋯O type (2.820(1)–2.840(2) A) linking molecules into endless chains in all three structures. The chains are further interconnected by the CH⋯O hydrogen bonds (3.483(1)–3.267(2) A) in 5a and 15, but not in 5b.The structural features of 5 and 15 determined by the single crystal X-ray analysis, reveal existence of intermolecular hydrogens bonds of NH⋯O type (2.820(1)–2.840(2) A).

Changes in 4-vinylsyringol and other phenolics during rapeseed oil refining

The aim of the present study was to examine changes in phenolic compounds during refining of rapeseed oil. In crude rapeseed oil, 4-vinylsyringol (canolol) is the dominant phenolic compound, accounting for 85% of total phenolics. Refining decreased the total amount of phenolic compounds by 90%. NMR and MS analyses of edible rapeseed oil phenolic extracts identified 4-vinylsyringol dimer as the dominant phenolic compound. This phenolic compound appears to form through acid-catalyzed dimerization-aromatic substitution of 4-vinylsyringol monomers. Analysis of rapeseed oils from different stages of the refining process suggest that 4-vinylsyringol dimer forms during the neutralization phase, when H3PO4 acts as a catalyst, or during bleaching, when acid-activated bleaching earth acts as the catalyst. Whether 4-vinylsyringol forms during one or the other phase appears to depend on the phospholipid content of the crude oil. These insights may be useful for designing rapeseed oil refining processes that maximize levels of 4-vinylsyringol dimer.

Chemometric evaluation of binary mixtures of alginate and polysaccharide biopolymers as carriers for microencapsulation of green tea polyphenols

ABSTRACT In this study principal component analysis and artificial neural networks were used to evaluate the potential of using binary mixtures of sodium alginate and other polysaccharide biopolymers as the carriers for microencapsulation of green tea bioactive compounds. Using binary mixtures of alginate and adjunct biopolymers increased the particle size (from 722 to 1344 µm) and textural parameters of the microbeads. Chemometric techniques revealed the combination of biopolymers and their ratio as the main factors influencing the encapsulation performance. The combination of alginate with hydroxypropyl methylcellulose and locust bean gum enabled to retain the highest (-)-epigallocatechin gallate and caffeine contents, the highest total phenols encapsulation efficiency, and their most retarded release in water, confirming these as the best delivery systems of polyphenol-type active compounds and signifying their potent food applications.

Methyl 4-(1'-carboxyferrocen-1-yl)butyrate.

The title compound, [Fe(C6H5O2)(C10H13O2)], contains a heteroannularly substituted ferrocene unit, with the two substituents, viz. 3-(methoxycarbonyl)propyl and carboxyl, both capable of forming O-H...O hydrogen bonds. The keto ester group is stereochemically hindered by the trimethylene spacer and does not participate in intramolecular hydrogen-bond formation. Instead, the carboxy groups form self-complementary intermolecular hydrogen bonds [O...O = 2.650 (2) A], which join the molecules into centrosymmetric dimers with a graph-set descriptor R(2)2(8).