Many isoprenylated flavonoids have been isolated from mulberry trees and related plants (Moraceae). Among them, kuwanons G (13) and H (14) were the first isolated active substances exhibiting a hypotensive effect from the Japanese Morus root bark. These compounds are considered to be formed through an enzymatic Diels-Alder reaction of a chalcone (15) and dehydro-kuwanon C (16) or its equivalent...

This paper describes the use of a substituent effects study to understand the mechanistic basis for an interfacial Diels-Alder reaction that does not proceed with standard second-order kinetics. Cyclopentadiene (Cp) undergoes a Diels-Alder reaction with a chemisorbed mercaptobenzoquinone to yield an immobilized Diels-Alder adduct. The pseudo-first-order rate constants are not linearly related t...

Constraints on nitrogen fixation are the ultimate causes of N limitation of primary production, but hypotheses concerning limitations to N2 fixation remain largely untested in natural terrestrial ecosystems. We examined limitations to N2 fixation by thinleaf alder (Alnus tenuifolia) in two stages of primary forest succession on the Tanana River floodplain (interior Alaska, USA) and focused on t...

Abstract The Diels–Alder reaction has long been established as an extremely useful procedure in the toolbox of natural product chemists. It tolerates a wide spectrum building blocks different complexity and degrees derivatization, enables formation six-membered rings with well-defined stereochemistry. In recent years, many total syntheses products have reported that rely, at some point, on use ...

The furan heterocycle is a dienic reagent particularly suitable for the Diels-Alder reaction and maleimides represent a typical family of complementary reagents because of their strong dienophilic character. This paper reviews critically the studies devoted to the exploitation of the Diels Alder reaction between those moieties to synthesise macromolecular materials possessing different structur...

ABSTRACT The Diels-Alder reaction between methyl (Z)-2-nitro-3-(4-nitrophenyl)-2-propenoate and cyclopentadiene yields a mixture of carbodiene Diels-Alder adducts. B3LYP/6-31G(d) simulations indicate that the conversion of addends into methyl (1R*,2S*,3S*,4R*)-2-nitro-3-(4-nitrophenyl)-bicyclo[2.2.1]hept-5-ene-2-carboxylate occurs via two-stage heterodiene Diels-Alder reaction and (in a second ...

The Diels-Alder reaction is a cornerstone in organic synthesis, forming two carbon-carbon bonds and up to four new stereogenic centers in one step. No naturally occurring enzymes have been shown to catalyze bimolecular Diels-Alder reactions. We describe the de novo computational design and experimental characterization of enzymes catalyzing a bimolecular Diels-Alder reaction with high stereosel...

In order to construct the functionalized AB ring system of clifednamide, member of the class of macrocyclic tetramic acid lactams, a synthesis was developed which utilized an Ireland-Claisen rearrangement and an intramolecular Diels-Alder reaction. Starting from di-O-isopropylidene-d-mannitol the allyl carboxylate precursor for the sigmatropic rearrangement was prepared. This rearrangement proc...

PURPOSE Aeroallergens are important causative factors of allergic diseases. Previous studies on aeroallergen sensitization rates investigated patients groups that had visited pediatric allergy clinics. In contrast, we investigated sensitization rates in a general population group of elementary school to teenage students in Incheon, Jeju, and Ulsan. METHODS After obtaining parental consent, sk...