Publicaties

Peptides have been reported to serve as precursors in the generation of alkylpyrazines, key aroma compounds in heated foods. Most previous studies, concerned with the generation of pyrazines via the Maillard reaction, were conducted using model systems of varying complexities. However, the formation of pyrazines in real food systems has received less attention. The aim of this study was to investigate the impact of adding protein hydrolysates as ...

Essential precursors of the cocoa-specific roasting-flavor notes were formed during proteolysis of the cocoa vicilin-class(7S) globulin by a mixture of cocoa aspartic protease and carboxypeptidase. These could be partially purified by ligand-exchange chromatography. Many constituents of this peptide fraction were destroyed by post-treatment with pepsin, but the cocoa-specific flavor-precursor peptides were largely resistant against pepsin ...

The generation of pyrazines in model systems containing enzymatically hydrolyzed whey protein under dry heating conditions was studied. Pyrazines are important Maillard flavor compounds. Hydrolysates, obtained with different peptidases (pepsine, chymosine, thermolysin and a non-specific peptidase from Aspergillus melleus), contained a varying peptide profile and free amino acid content. The impact of each hydrolysate on the generation of flavor ...

The first synthesis of racemic 2-(aminomethyl)cyclopropane-1,1-dicarboxylic acid was developed involving sequential iodocarbocyclization, azidation, saponification and reduction of dimethyl 2-allylmalonate. The developed synthetic pathway avoids reactions such as ring opening of the cyclopropane ring toward acyclic delta-amino carboxylic acid derivatives or lactamisation toward bicyclic methyl 3-aza-2-oxobicyclo[3.1.0]hexane-1-carboxylates which ...

Marine bacteria contribute substantially to nutrient cycling in the oceans and can engage in close interactions with microalgae. Many microalgae harbor characteristic satellite bacteria, many of which participate in N-acyl homoserine lactone (AHL) mediated quorum sensing. In the diffusion-controlled phycosphere, AHLs can reach high local concentrations, with some of them transforming into tetramic acids, compounds with a broad bioactivity. We ...

2-Azidocyclopropane-1,1-dicarboxylic esters were transformed into orthogonally N-protected alkyl 1-amino-2-azidocyclopropanecarboxylates via stereoselective monosaponification and subsequent Curtius reaction. Following deprotection of the ester function or the Boc-protected amino group, the first derivatives of a novel class of conformationally constrained cyclopropane alpha,beta-diamino carboxylic acids were made accessible.

A variety of different N-[2-chloro-4-(chloromethyl)pent-4-enylidene]amines and N-(2,6-dichlorohex-4-enylidene)amines was prepared for the first time, and their reactivity as eligible building blocks for the synthesis of biologically relevant nitrogen-containing heterocyclic compounds was studied. In this way, a convenient entry into functionalized 1-azabicyclo[3.1.0]hexanes, piperidines, pyridines, pyrroles, and tetrahydroindoles was developed, ...

Several natural products containing a 1,4-oxazepane-2,5-dione-core are known. One example is serratin, isolated from Serratia marcescens. Because of the presence of a carboxylic amide, which has a preference for a trans conformation, and the presence of a labile lactone in this core, many synthetic methodologies commonly used for the cyclization toward medium-sized heterocycles cannot be applied. As N-acyl amino acids lacking a third substituent ...