Cascade double

Reverse flow Cross- flow Double pass Cascade double pass... 

Reverse Flow Cross Flow Double Pass Cascade Double-Pass... 

Four cationic palladium intermediates in the Pd(0)-catalysed three-component cascade double addition-cyclization of organic halides, 2-(2,3-allenyl)malonates, and imines have been characterized by the high-resolution ESI-FTMS technology.84... 

Kumar, K. (2012) Stereoselective cascade double-annulations provide diversely ring-fused tetracyclic benzopyrones. Org. Lett, 14, 5924-5927. 

Synthesis of 1,2-disubstituted indole frameworks 257 via a formal 4 - - 1 cydoaddition between a 4-carbon unit and a primary amine was recently developed by Ackermann (Scheme 9.90) [242]. Reactive intermediates, 2-(o-haloaryl)enam-ines 256 were generated via the Cu(I)-catalyzed hydroamination of the orfHo-halo-substituted phenylacetylenes 254 with primary amines 255. A subsequent Cu(I)-catalyzed intramolecular enamine arylation reaction gave the corresponding indoles 257 in good yields. The authors demonstrated that alkynyl chlorides 254 could also participate in this cascade double amination process, albeit with a substantially diminished efHdency. 

Figure 30 Chemical structure of PDFD, schematics of a TGA (thioglycolic acid)-capped CdTe QD and of the PDFD/QD/dye-labeled DNA (IRD700-labeled ds-DNA) complex used to detect DNA hybridization through a cascaded double FRET. Upon optical excitation of PDFD and QDs, energy transfer takes place from the PDFD to the QDs (FRET 1) and from the QDs to the dye-labeled DNA (FRET 2).

In studies toward the synthesis of the antibacterial natural product pleuromutilin (Scheme 25.66), Procter et al. reported a cascade double annulation process using Sml2 to generate an initial ketyl radical from 137. After a subsequent cyclization, the resulting new ketyl radical was reduced to form the organosamarium (III) intermediate 138, which in turn promoted a diastereoselective intramolecular aldol reaction to give 139. ° ... 

The cascade double Michael addition of R02CCH2C(X H=C(C02R)2 to enals R CH=CHCH=0, catalysed by (5)-(325), and producing polysubstituted cyclopen-tanones, has been investigated by the DPT method. The calculations support the expected mechanism and correctly predict the dr and ee values. ... 

Detailed accounts of the biosynthesis of the prostanoids have been pubUshed (14—17). Under normal circumstances arachidonic acid (AA) is the most abundant C-20 fatty acid m vivo (18—21) which accounts for the predominance of the prostanoids containing two double bonds eg, PGE2 (see Fig. 1). Prostanoids of the one and three series are biosynthesized from dihomo-S-linolenic and eicosapentaenoic acids, respectively. Concentrations ia human tissue of the one-series precursor, dihomo-S-linolenic acid, are about one-fourth those of AA (22) and the presence of PGE has been noted ia a variety of tissues (23). The biosynthesis of the two-series prostaglandins from AA is shown ia Eigure 1. These reactions make up a portion of what is known as the arachidonic acid cascade. Other Hpid products of the cascade iaclude the leukotrienes, lipoxins, and the hydroxyeicosatetraenoic acids (HETEs). Collectively, these substances are termed eicosanoids. 

Tower Diam- Cross Double Cross Double Cascade End... 

The second part of lanosterol biosynthesis is catalyzed by oxidosqualene lanosterol cyclase and occurs as shown in Figure 27.14. Squalene is folded by the enzyme into a conformation that aligns the various double bonds for undergoing a cascade of successive intramolecular electrophilic additions, followed by a series of hydride and methyl migrations. Except for the initial epoxide protonation/cyclization, the process is probably stepwise and appears to involve discrete carbocation intermediates that are stabilized by electrostatic interactions with electron-rich aromatic amino acids in the enzyme. 

In the synthesis of the squalenoid glabrescol (72 originally attributed structure), containing five adjacent (all cis) THF rings, the necessary precursor of the polyepoxide cascade, the pentaepoxide 71, was achieved by epoxidation of each of the trisubstituted double bonds of the known (R)-2,3-dihydroxy-2,3-dihydrosqualene (70) by the Shi epoxidation approach (Scheme 8.18) [34]. Treatment of 71 with CSA at 0 °C and subsequent purification by column chromatography provided the pure polycyclic ether 72 by a cascade process reasonably initiated by the free secondary alcohol functionality [35a]. 

The antiviral state induced by different types of IFNs is mediated by various IFN-induced proteins. The best-known antiviral effectors produced as a result of IFN cascade induction are shown in Table 2. They include 2 -5 oligoadenylate synthetase (2 -5 OAS), double-stranded RNA activated protein kinase (PKR), and myxovirus (Mx) proteins. Additional effectors include RNA-specific adenosine deaminase 1 (ADARl), the 20-kDa ISG product (ISG20), ISG54 and ISG56, and IFN-stimulated micro RNAs (Pedersen et al. 2007). 

SEE extraction pressures of 500 bar at 80 to lOO C combined with countercurrent cascading mode of extraction using four extraction vessels, the rate of oleoresin extraction doubles again rate of oleoresin extraction under these conditions is four times that of traditional batch extraction at 300 bar and 60°C... 

Assuming the contribution of the potential energy curves which have not been taken into account to be almost constant with the collision energy, such calculations could provide a relative estimate of the variation of the double capture cross-sections with the collision energy. The results presented in Fig. 7 seem to be coherent with this hypothesis and to corroborate a cascade effect for the double electron capture process. 

The disassembly pathway of molecular probe 39 is initiated by catalytic cleavage of phenylacetic acid by PGA, elimination of azaquinone methide, decarboxylation, and cyclization to release dimethylurea derivative and phenol 40 (Fig. 5.38). The latter rapidly undergoes double quinone methide elimination to release the two reporter units and by-product 41. The output of these cascade... 

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