Über Brom- und Methoxyderivate des Indigos

A tunable synthesis of indigoids: targeting indirubin through temperature

The spontaneous conversion of 3-indoxyl to indigo is a well-established process used to produce indigo dyes. It was recently shown that some indoles, when reacted with molybdenum hexacarbonyl and cumyl peroxide, proceed through an indoxyl intermediate to produce significant amounts of indirubin through a competing mechanism. Modulation of this system to lower temperatures allows for careful tuning, leading to selective production of indirubins in a general process. A systematic assay of indoles show that electron deficient indoles work well when substituted at the 5 and 7 positions. In contrast, 6-substituted electron rich indoles give the best results whereas halogeno indoles work well in all cases. This process shows broad functional group tolerance for generally reactive carbonyl-containing compounds such as aldehydes and carboxylic acids.

Continuous Flow Synthesis of Heterocycles: A Recent Update on the Flow Synthesis of Indoles

Indole derivatives are among the most useful and interesting heterocycles employed in drug discovery and medicinal chemistry. In addition, flow chemistry and flow technology are changing the synthetic paradigm in the field of modern synthesis. In this review, the role of flow technology in the preparation of indole derivatives is showcased. Selected examples have been described with the aim to provide readers with an overview on the tactics and technologies used for targeting indole scaffolds.

Mass spectrometry imaging reveals new biological roles for choline esters and Tyrian purple precursors in muricid molluscs

Despite significant advances in chemical ecology, the biodistribution, temporal changes and ecological function of most marine secondary metabolites remain unknown. One such example is the association between choline esters and Tyrian purple precursors in muricid molluscs. Mass spectrometry imaging (MSI) on nano-structured surfaces has emerged as a sophisticated platform for spatial analysis of low molecular mass metabolites in heterogeneous tissues, ideal for low abundant secondary metabolites. Here we applied desorption-ionisation on porous silicon (DIOS) to examine in situ changes in biodistribution over the reproductive cycle. DIOS-MSI showed muscle-relaxing choline ester murexine to co-localise with tyrindoxyl sulfate in the biosynthetic hypobranchial glands. But during egg-laying, murexine was transferred to the capsule gland, and then to the egg capsules, where chemical ripening resulted in Tyrian purple formation. Murexine was found to tranquilise the larvae and may relax the reproductive tract. This study shows that DIOS-MSI is a powerful tool that can provide new insights into marine chemo-ecology.

Are the Traditional Medical Uses of Muricidae Molluscs Substantiated by Their Pharmacological Properties and Bioactive Compounds?

Marine molluscs from the family Muricidae hold great potential for development as a source of therapeutically useful compounds. Traditionally known for the production of the ancient dye Tyrian purple, these molluscs also form the basis of some rare traditional medicines that have been used for thousands of years. Whilst these traditional and alternative medicines have not been chemically analysed or tested for efficacy in controlled clinical trials, a significant amount of independent research has documented the biological activity of extracts and compounds from these snails. In particular, Muricidae produce a suite of brominated indoles with anti-inflammatory, anti-cancer and steroidogenic activity, as well as choline esters with muscle-relaxing and pain relieving properties. These compounds could explain some of the traditional uses in wound healing, stomach pain and menstrual problems. However, the principle source of bioactive compounds is from the hypobranchial gland, whilst the shell and operculum are the main source used in most traditional remedies. Thus further research is required to understand this discrepancy and to optimise a quality controlled natural medicine from Muricidae.

Regioisomeric control of charge transport polarity for indigo-based polymers

Two regioisomeric conjugated polymers containing indigo units connected at 5,5′- and 6,6′-positions exhibit opposite charge transport polarity.

Mass spectrometry imaging on porous silicon: investigating the distribution of bioactives in marine mollusc tissues

Desorption/ionization on porous silicon-mass spectrometry (DIOS-MS) is an attractive alternative to conventional matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) for the analysis of low molecular weight compounds. Porous silicon (pSi) chips are also suitable as support for mass spectrometry imaging (MSI). Here, we report an implementation of DIOS-MSI using the biosynthetic organs of a marine mollusc for proof of principle. The tissue section is stamped onto a fluorocarbon-functionalized pSi chip, which extracts and traps small hydrophobic molecules from the tissue under retention of their relative spatial distribution. The section is subsequently removed and the chip is imaged without any remaining tissue. We apply this novel tissue contact printing approach to investigate the distribution of biologically active brominated precursors to Tyrian purple in the hypobranchial gland of the marine mollusc, Dicathais orbita, using DIOS-MSI. The tissue contact printing is also compatible with other types of desorption/ionization surfaces, such as nanoassisted laser desorption/ionization (NALDI) targets.

A simple, safe and efficient synthesis of Tyrian purple (6,6'-dibromoindigo)

6,6’-Dibromoindigo is a major component of the historic pigment Tyrian purple, arguably the most famous dye of antiquity. Over the last century, chemists have been interested in developing practical syntheses of the compound We describe herein a new, reasonably simple and efficient synthesis of Tyrian purple which opens the way to the production of large quantities of the dye with minimal hazards and at low cost.

Preparation of Tyrian purple (6,6'-dibromoindigo): past and present

Over the past century, various synthetic approaches have been suggested to the most famous dye of antiquity, Tyrian purple (6,6′-dibromoindigo). These synthetic routes have been exhaustively surveyed and critically evaluated from the perspective of convenience, cost, safety and yield.

Substitution and chemical environment effects on the absorption spectrum of indigo

The UV/visible spectra of a series of indigo derivatives have been evaluated by using ab initio methods. The combination of the Polarizable continuum model for estimating bulk solvent effects with the TD-B3LYP6-311 + G(2d,p)B3LYP6-311G(d,p) level of approximation, leads to an accurate description of the wavelength of maximum absorption of indigoids compounds. Using this procedure, we have assessed the effects of both the surroundings (solvent and solid state) and the substitution pattern. For the latter, we obtained a mean absolute deviation of only 7 nm (0.02 eV) compared to experiment, for a set of 86 molecules/solvents.

Tyrian Purple: 6,6’-Dibromoindigo and Related Compounds

The genesis of the purple dye from shellfish, its composition, origin, intermediates, analysis and synthesis of the components, 6,6’-dibromoindigo, 6-bromoindigo and 6,6’-dibromoindirubin are reviewed