A quinonoid naphthopyranone as a model for the synthesis of the pigment xylindein: Photochemical formation of the lactone ring

3-Propyl-3,4,5,10-tetrahydronaphtho[2,3-c]pyran-1,5,10(1 H)- trione (5) has been synthesized with a view to determining a satisfactory pathway to its 7,9-dihydroxy-analogue (4), which it is hoped will ultimately provide a route to the extended quinonoid pigment, xylindein. A key step in the reaction sequence is the photo-rearrangement of 1,4-dimethoxy-frans- 3-pent-1 -enylnaphthalene-2-carboxylic acid (11) into the related δ-lactone (12) having the required ring system. Subsequent silver(li) oxide oxidative demethylation affords the target quinone (5)

Modeling tidal sand wave dynamics in response to dredging interventions

Tidal sand waves are large scale bed forms observed in many tidally dominates sandy shallow seas, such as the North Sea. They often interfere with offshore human activities, such as navigation, because they are dynamic, are frequently surveyed and dredged. For both, surveying frequencies and dredging strategies, knowledge on sand wave recovery is required.<br/

Alkylation of quinones: Formation of cyclopropyl-1,4 naphthoquinones and related compounds

Alkylation of 1,4-naphthoquinone with cyclopropyl carboxylic acid in the presence of ammonium peroxodisulphonate and silver nitrate afforded a mixture of 2-cyclopropyl- and 2,3- dicyclopropyl-1,4-naphthoquinones. In reactions directed at the synthesis of 5-deoxyjuglomycins A and B, a substituted cyclopropyl-1,4-naphthoquinone was also obtained

Modeling wave and wind climate effects on tidal sand wave dynamics:A North Sea case study

To obtain site-specific wave and wind climate averaged sand wave dynamics, we combine an idealized linear stability model with 20 years of wave and wind data taken from the Euro Platform in the North Sea. The model output results in a wave and wind climate-averaged growth and migration rate. The results show that waves and wind affect particularly migration and to a much smaller extent the growth rate. Seasonal variations in wave and wind conditions during winter and summer periods result in seasonal variations in sand wave dynamics, in particular during winter the migration rate is larger, the growth rates are lower and the preferred wavelength is larger compared to summer. Medium wave and wind conditions are responsible for two thirds of the migration rate, while these conditions occur roughly only one third of the time. Extreme wave and wind conditions result in only a moderate contribution to the migration rate. Furthermore, we see a seasonal variation in migration as well as reasonable correlation with observed migration rates for the intervals between surveys in the period 1996–2010. Our work shows that storms are able to affect sand wave migration, and cause variability in migration rate

Stable quinonoid derivatives of isobenzofuran and isoindole

The syntheses of quinonoid derivatives of Isobenzofuran and isoindole, via the quinones (6) and (12), are described

Models for the syntheses of the naphthoquinonoid antibiotics, the juglomycins A and B

No abstract availabl

Diastereoselective addition of imidazolidin-2-one controlled enolates to activated imines

Ephedrine-based imidazolidin-2-one chiral auxiliaries afford good syn stereoselectivity in the addition of their derived titanium enolates with an activated imine system. This provides entry into β-amino acid systems

Synthesis of novel C2-symmetric ligands based on (R,R)- and (S,S)-diphenyl-1,3-propanediol

A range of novel C2-symmetric dioxygen and dinitrogen ligands can readily be obtained through the interconversion of the parent 1,3-diphenyl- 1,3-propanediol enantiomers which are, in turn, accessed in good yields via a Sharpless asymmetric epoxidative resolution