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Use in Natural Product Synthesis

Nickel-catalyzed couplings of alkynes and a, 3-unsaturated carbonyls have been applied in the total synthesis of several complex natural products. For many of these examples, the use of nickel-catalyzed alkylative coupling offers a straightforward means of synthesis. For each of the following examples the general synthetic plan is briefly described, followed by the key nickel-catalyzed coupling step that is critical for the construction of the overall structural motif of the natural product in question. [Pg.189]


Cleavage of silyloxiranes (e.g. 55) by methanol, leading to aldehydes or ketones (e.g. 56 Scheme 48), has found use in natural products synthesis (8UA1831, 80JA5004). [Pg.110]

The coupling of carboxylic acids has been profitably used in natural product synthesis. Kolbe electrolysis of 10 is part of a (+) x-onocerin synthesis [120], the dimerization of il leads to a pentacyclosqualene [121], the electrolysis of 12 afforded a dime-with two quaternary carbon atoms [122], and 2,6,10,15,19,23-hexamethyltetracontane has been synthesized from 13 [123]. [Pg.101]

The Suzuki reaction has proved extremely versatile and has found extensive use in natural product. synthesis. " Arylboronic acids [ArB(OH)2 are the usual substrates in this reaction together with arylhalides or triflates (Ar X, X = halogen... [Pg.208]

The domino process probably involves the chiral enamine intermediate 2-817 formed by reaction of ketone 2-813 with 2-815. With regard to the subsequent cy-doaddition step of 2-817 with the Knoevenagel condensation product 2-816, it is interesting to note that only a normal Diels-Alder process operates with the 1,3-bu-tadiene moiety in 2-817 and not a hetero-Diels-Alder reaction with the 1-oxa-l,3-butadiene moiety in 2-816. The formed spirocydic ketones 2-818/2-819 can be used in natural products synthesis and in medidnal chemistry [410]. They have also been used in the preparation of exotic amino adds these were used to modify the physical properties and biological activities of peptides, peptidomimetics, and proteins... [Pg.175]

A number of nitro compounds used in natural product synthesis have been prepared by the nitration of alkyl halides. Some recent examples are summarized in Table 2.4. [Pg.20]

The Diels-Alder reaction of nitroalkenes followed by the Nef reaction is frequently used in natural product synthesis.7 For example, Scheme 8.3 shows an elegant synthesis of rf/-mesem-brane starting from the Diels-Alder reaction of 1-arylnitroethene with l,3-butadiene.7a... [Pg.232]

The use of vinylallenes as the diene component in Diels-Alder reactions is very common, thus resulting in their ubiquitous use in natural product synthesis. A vinylal-lene has even been proposed by Schreiber and Kiessling [10] as a biogenetic intermediate in the synthesis of the skeleton of esperamicin A (32 —> 33). Their synthetic approach to esperamicin A (34) was modeled after this biogenetic proposal in which a Type II intramolecular Diels-Alder cycloaddition was used to gain access to the highly unsaturated bicyclic core of 34 (Scheme 19.8) [10]. [Pg.1046]

Lichtenthaler, F. W. Building blocks from sugars and their use in natural product synthesis, in R. Scheffold, Ed., Modern Synthetic Methods, Vol. 6, VCH, Weinheim, 1992, pp. 273-376. [Pg.58]

Metathesis reactions are now widely used in natural product synthesis. Novel retrosynthetic analyses were developed because a carbon-carbon single bond can be formed after hydrogenation of a double bond constructed by metathesis. Although many types of metathesis are now known, the reaction is classified by olefin, enyne, and alkyne metatheses in this chapter. [Pg.154]

This strategy has already been found useful in natural product synthesis. In the course of a synthesis of V-ATPase inhibitor oximidine HI, John Porco of Boston University has described (Angew. Chem. Ini. Ed. 2004,43, 3601) the cyclization of 7 to 8. In the absence of the pententyl director, the initial complexation of the Ru catalyst was with the 1,3-diene, leading to allylidene complex and so effectively killing the catalyst. In this case, the Hoveyda catalyst 8 provided a cleaner product than G2 did. [Pg.183]

It became apparent early on that compounds of the 1,2-disubstituted cyclohexenes allow exploitation of a wide range of synthetic opportunities, leading to their frequent use in natural product synthesis the application of chemo-synthetic routes for selected monoterpenoid indole alkaloid alone are summarised here [86]. [Pg.80]

Stoichiometric palladium-mediated cyclization was used in natural product synthesis by Boger a number of years ago, as was noted in the introduction. More recently, an intramolecular palladium-catalyzed amination of a heteroaromatic halide has been used as a step in the synthesis of an a-carboline natural product analog [146]. As discussed above, the diphenylhydrazone arylation can also be used for nitrogen heterocycle synthesis [140]. [Pg.228]

Organozinc reagents have been coupled with halides in the synthesis of dienes and other conjugated systems to form new carbon-carbon bonds such reactions have been reviewed477-479. In particular, the reaction of alkynyl zinc reagents with vinyl halides has been used in natural product synthesis, usually catalyzed by palladium complex catalysts. [Pg.730]

Several fully saturated heterocyclic systems which have been formed by cycloaddition reactions have found use in natural product synthesis. Cycloadducts (27) and (28) were prepared as part of an investigation into the synthesis of the benzoxocin fragment of the antitumor anthracycline nogalomycin <9lJOCl364> and cycloadducts (245) and (248) were intermediates in the synthesis of amino sugar derivatives <84JA5598>. [Pg.140]

The capacity of the method to generate nitrile oxides bearing diverse substituents, which has led to its recent use in natural product synthesis, e.g. of ergot alkaloids such as... [Pg.422]

A concentrated solution of LiCl04 in EtzO is effective in the allylation of silyl enolates with allyl alcohols and acetates.310 The LiClCL-promoted reaction with silyl enolates enables ring opening of 8-oxabicyclo[3.2.1]octa-2,6-dienes to highly functionalized 1,4-cycloheptadienes, which can be further manipulated for use in natural product synthesis (Equation (83)).311... [Pg.327]

Biologically Significant Reactions of Co2(CO)6 (li2-RC=CR). Many dicobalt carbonyls with complexed alkynes have been used in natural product synthesis. In one... [Pg.853]

The Ti(OCHMe2)4 and diethyl tartrate can be present in catalytic amounts (15-10mol%) if molecular sieves are present. Polymer-supported catalysts have also been reported.Both (-I-) and (—) diethyl tartrate are readily available, so either enantiomer of the product can be prepared. The method has been successful for a wide range of primary allylic alcohols, including substrates where the double bond is mono-, di-, tri-, and tetrasubstituted, " and is highly useful in natural product synthesis. The mechanism of the Sharpless epoxidation is believed to involve attack on the substrate by a compound formed from the titanium alkoxide and the diethyl tartrate to produce a complex that also contains the substrate and the f-BuOOH.i 2 ... [Pg.1177]

The alkynylation reactions have been applied to polyfiuictionalized molecules (Scheme n), " and have proved to be quite useful in natural product synthesis. [Pg.343]

With a phenylsulfonyl group as X (Scheme 41) the intermediate, after rearrangement, will decompose directly to an aldehyde function, which reacts wiA excess alkyllithium to form an unsaturated alcohol. The often efficient transfer of chirality from C-1 of an optically active allylic alcohol to the newly created stereogenic centers at C-3 and/or C-4 is another valuable aspect of the 2,3-Wittig rearrangement which has already found extensive use in natural product synthesis. ... [Pg.852]

Overman, L. E. New reactions for forming heterocycles and their use in natural products synthesis. Aldrichimica Acta 1995, 28,107-120. [Pg.659]

The reagents 128—130 are stable crystalline compounds which form anions easily with BuLi. Addition to aldehydes or ketones give protected (3,7-unsaturated carbonyl compounds, e. g. 131, after completion of the Homer-Wittig reaction, and hence the ketones 132 themselves. These methods have not yet been used in natural product synthesis. [Pg.19]


See other pages where Use in Natural Product Synthesis is mentioned: [Pg.329]    [Pg.208]    [Pg.89]    [Pg.147]    [Pg.147]    [Pg.614]    [Pg.19]    [Pg.422]    [Pg.30]    [Pg.729]    [Pg.68]    [Pg.729]    [Pg.168]    [Pg.564]    [Pg.623]    [Pg.147]    [Pg.412]    [Pg.432]    [Pg.647]    [Pg.412]    [Pg.432]    [Pg.227]    [Pg.258]   


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