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...

Within-stand variation in understory species composition and biomass was studied in 16 even-aged stands of mixed Red Alder Sitka Spruce Western Hemlock (Alnus rubra Picea sitchensis Tsuga heterophylla) forest. The sites were upland sites, and the stands were 28-39 years old. We compared understory within three categories of microsite types: Red Alder-dominated, conifer-dominated, and mixed alde...

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 ...

alder (alnus subcordata subsp. subcordata) is one of the most important tree species in northern forests of iran and is economically considered as the fourth commercial tree. a leaf spot disease of alder caused by xanthomonas sp. has been reported from several forest regions of mazandaran province (rahimian et al. 1383. 16th iran. plant protec. cong., 439). according to a recent genomic study, ...

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...