A novel and convenient approach, the domino retro Diels-Alder/Diels-Alder reaction sequence for highly stereo- and regioselective synthesis of various bicyclo[2.2.2]octenone and bicyclo[2.2.2]octadienone derivatives is presented. Thus, the masked o-benzoquinones (MOBs) 2a-e generated by the pyrolysis of the respective dimers 3a-e participated in this novel synthetic strategy with a variety of o...

The Diels-Alder cycloadditions of cyclopentadiene and 2,3-dimethyl-1,3-butadiene to a range of 2-thio-3-chloroacrylamides under thermal, catalytic and microwave conditions is described. The influence of reaction conditions on the outcome of the cycloadditions, in particular the stereoselectivity and reaction efficiency, is discussed. While the cycloadditions have been attempted at the sulfide, ...

Background Oral Allergy Syndrome (OAS) is an IgE-mediated allergic response to fresh fruits, nuts and vegetables caused by cross-reactivity between pollen allergens and structurally similar food proteins. Alder pollen is a prominent allergen in coastal British Columbia, present at high levels from FebruaryApril. We hypothesized that this exposure may lead to increased prevalence of Alder pollen...

Initially, lasubin II was synthesized diastereoselectively in racemic form [3]. Asymmetric syntheses of lasubin II were achieved based on stereoselective transformations of enantiomerically pure substrates [4] or, for example, via a diastereoselective aza-Diels-Alder reaction using a resolved chiral arylaldehyde tricarbonylchromium complex [5]. Recently, an enantioselectively catalyzed aza-Diel...

Studies toward the enantiospecific total synthesis of rhodexin A via a very hindered inverse electron demand Diels-Alder reaction are described. The C8-diastereomer of the fully elaborated tetracyclic core of rhodexin A, 23, was prepared in good yield and excellent selectivity using as the key step the stepwise Diels-Alder reaction of the very hindered dienone 3 and the silyl enol ether 4 catal...

Two catalysts, Me(2)AlNTf(2) and MeAl(NTf(2))(2), derived from the mixing of trimethylaluminum with triflimide, proved to be highly effective catalysts in hindered Diels-Alder reactions, generating the desired Diels-Alder cycloadducts from both hindered 2-silyloxydienes and hindered dienophiles. Thus reaction of 1 with 2 afforded the hindered cycloadduct 4 in excellent yield in 0.5-1.5 h at -40...

Understanding relations between climate and pollen production is important for several societal and ecological challenges, importantly pollen forecasting for pollinosis treatment, forensic studies, global change biology, and high-resolution palaeoecological studies of past vegetation and climate fluctuations. For these purposes, we investigate the role of climate variables on annual-scale varia...

Parasite damage strongly affects dynamics of boreal forests. Damage levels may be affected by climate change, either directly or indirectly through changes in properties of host trees. We examined how herbivore and pathogen damage in Alnus viridis subsp. fruticosa (Rupr.) Nym. depend on leaf morphology and chemistry, tree size, and tree neighborhood. Damage and tree properties were measured in ...

Annual renewable resource potential of medicinal plant materials in the Republic Belarus - Black alder leaves and Gray has been studied. It was found that average annual supply black for last 6 years 7845898,5 tons gray 733257,5 tons. The stock is almost 10 times as high leaves. During storing wood from 2015 to 2019, on 65,623,8 dry were unused by-product. Annually sylvulas are created forest f...

ABSTRACT Knoevenagel condensation of barbituric acids with aromatic aldehydes containing one or two formyl groups was carried out. 5-Arylidenebarbituric acids underwent smooth hetero-Diels-Alder (HDA) reactions with enol ethers to afford cis and trans diastereoisomers of pyrano[2,3-d]pyrimidine-2,4-diones and 5,5'-(1,4-phenylene)bis[2H-pyrano[2,3-d]pyrimidine-2,4(3H)-dione] derivatives in excel...