Attempted Diels-Alder Reactions on Vindoline Derivatives

The Diels-Alder reaction of vindoline and methyl vinyl ketone resulted in a Friedel-Crafts reaction product. In the reaction between the ortho-quinone derivative of vindoline and N-phenylmaleimide, two anomalous products were obtained, a vindoline dimer, and a condensed vindoline derivative

Self-Managed Belief as Part of the “Scientific Method”: Part II—Examples From Published Scientific Work

As argued in part I [1], our scientific descriptions of the world inevitably contain some subjective “beliefs” weaved into the “knowledge” that stems from what we consider to be “objective experimental evidence”hence our off-the-wall term “beliefedge” introduced therein. Besides being important drivers of science, our hidden or “unmanaged” beliefs are also a major source of the “mental traps” that can all too easily derail human judgment even in the most eminent minds [2]. Indeed, despite the solidor apparently solidand well-accepted theoretical foundations of natural sciences, there are a number of traps that notoriously and secretly keep hijacking scientists' reasoning when designing and running experiments as well as during data processing and interpretation. In part II we aim to illustrate these ideas, with a touch of personal flair, through a few examples that we deem to be instructive and relevant in various fields of analytical nuclear magnetic resonance (NMR), magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) or functional magnetic resonance imaging (fMRI) applications. First, we shall consider some basic steps to ensure that data quality is sufficient for reliable scientific work employing magnetic resonance (MR)based measurement techniques. When discussing various examples in some detail below, we shall also mention related artifacts and how to avoid or reduce them. We will finish by summarizing some important aspects of practical belief-management.(VLID)470479

Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B

Starting from racemic naringenin ((±)-1), a mixture of dracocephin A stereoisomers 6-(2”-pyrrolidinone-5”-yl)naringenin (±)-2a–d and its regioisomer, dracocephin B 8-(2”-pyrrolidinone-5”-yl)naringenin (±)-3a–d originally isolated from Dracocephalum rupestre, have been synthesized in a one-pot reaction. The separation of 2a–d and 3a–d was achieved by preparative HPLC. The four stereoisomers of each natural product were separated by analytical chiral HPLC and their absolute configuration was studied by the combination of HPLC–ECD measurements and TDDFT–ECD calculations. The synthesized flavonoid alkaloids were further characterized by physicochemical and in vitro pharmacological studies