Synthesis general methodology

The authors developed two general methodologies for the synthesis of these monodisperse, defined oligomers. They can be built up stepwise, e. g. via additon of organometallic species to cyclohexan-1,4-dione, followed by aromatization to the oligoarylene (e.g. for 21). 

Wender, P.A., Schaus, J.M., White, A.M. (1980) General Methodology for cis-Hydroisoquinoline Synthesis Synthesis of Reserpine. Journal of the American Chemical Society, 102, 6157-6159. 

This chapter briefly describes the general methodology for making both series of ARCAs and describes in detail the synthesis of two representative compounds P1-guanosine-5/ P3-(7,3/-0-dimethylguanosine-5/) triphosphate (Fig. 11.1, compound 2) and P1-guanosine-5/ P3-(7,3/-0-dimethyl-guanosine-5 ) /by- methylene-triphosphate (Fig. 11.1, compound 5). 

Synthesis of p-lactam antibiotics from sugars (either as chiral auxiliary or chiron), describing the general methodology developed in 1990s by Chmielewski and based on [2 + 2] cycloaddition of isothiocyanides to sugar olefins, was also comprehensively reviewed.5... 

Asymmetric synthesis can refer to any process which accesses homochiral products. We will focus on asymmetric synthesis from racemic or prochiral starting materials in the presence of an enantioselective catalyst (enzyme). There are four general methodologies commonly applied kinetic resolution, dynamic kinetic resolution, deracemization and... 

These macromolecule-based purification methods isolate polymer-bound products from soluble impurities, but do not generally purify the product from other polymer-bound byproducts. Such byproducts arise from incomplete reactions or side reactions and in classical solution chemistry, similar byproducts are removed during product purification at each step of a multi-step synthesis. Support-based methodologies, while removing the multiple, laborious purification steps of a classical synthesis, generally do not provide a method for the purification of intermediates. Instead, these methodologies demand that reaction conditions be optimized such that reactions are driven to completion to avoid a complicated final mixture of products. However, some developed liquid-phase methods achieve high purity of products without quantitative reaction yields [21-26]. 

The Erlenmeyer synthesis usually proceeds with a very high degree of stereoselectivity to favor the thermodynamically more stable (Z) isomer that is easily isolated by recrystallization. In some cases, the (Z) isomer is the only product obtained. This general methodology has been used extensively to prepare of a wide variety of unsamrated oxazolones. 

In 1962, solid-phase peptide synthesis was introduced, and described in detail in 1963.1171 This new synthetic principle was developed with the hope that it would simplify and accelerate the synthesis of peptides. The idea was to covalently anchor the C-terminal residue of a peptide to an insoluble support and then to assemble the remaining amino acids in a stepwise manner with activated amino acids while the peptide was in the insoluble solid phase, and finally to cleave the peptide from the solid support and liberate it into solution. The general methodology is shown in Scheme 6. 

The same general methodology, the reaction of the ditellurolate dianion 68 with tetrachloroethylene, was employed for the synthesis of the thiophene-annelated TTeF. Compound 69 was obtained in 75% yield (83MI1 84JA8303 85MI2). No formation of the possible six-membered ring derivative was reported. 

A general methodology for the construction of quaternary carbon atoms at the carbonyl carbon of ketones has been successfully exploited for the facile synthesis of ( )-lycoramine (299) (Scheme 30) (165). Thus, the O-allylated o-vanillin 322 was allowed to react with vinyl magnesium bromide followed by Jones oxidation, and the acid-catalyzed addition of benzyl IV-methylcarbamate to the intermediate a,(3-unsaturated ketone furnished 323. Wadsworth-Emmons olefination of 323 with the anion derived from diethyl[(benzylideneami-no)methyl]phosphonate (BAMP) provided the 2-azadiene 324. The subsequent regioselective addition of n-butyllithium to 324 delivered a metalloenamine that suffered alkylation with 2-(2-bromoethyl)-2-methyl-l,3-dioxolane to give, after acid-catalyzed hydrolysis of the imine and ketal moieties, the 8-keto aldehyde 325. Base-catalyzed cycloaldolization and dehydration of 325 then provided the 4,4-disubstituted cyclohexenone 326. The entire sequence of reactions involved in the conversion of 323 to 326 proceeded in very good overall yield and in one pot. 

To overcome the difficulty in the crossover step a general methodology has been developed in our laboratory for the synthesis of block copolymers when the second monomer is more reactive than the first one. It involves the intermediate capping reaction with non-(homo)polymerizable monomers such as i) 1,1-diphenylethylene (DPE) and its derivatives and ii) 2-substitut-ed furans. 

Kuisle, O., Quinoa, E., and Riguera, R., (1999) A general methodology for automated solid-phase synthesis of depsides and depsipeptides. Preparation of a valinomycin analogue. J. Org Chem. 64, 8063-8075. 

The reversible [2+2] cycloaddition of metal alkylidyne or Fischer-type metal carbyne complexes remains the only general methodology for the synthesis of metallacyclobutadiene complexes. Recent literature revolves principally around the heavier group 6 metals and the investigation of intermediates in catalytic alkyne metathesis (Scheme 25 Equation 45) <1996CHEC-II(lb)887> (W <2005OM4684>, Mo <2003JOM56>). 

Our laboratory developed a new synthetic approach to (l-2)-iS-thiodisaccharides (26) utilizing the reactivity of conjugated system of isolevoglucosenone. This synthetic approach (scheme 11) constitutes a general methodology, similar to our previously reported synthesis of (1-4)-iS,-3-deoxythidosacharides (27-28). 

Star polymers of chemically different arms are usually called miktoarm stars. Although there are several individual methods for the synthesis of miktoarm stars four general methodologies have been developed. Three of them are based on anionic polymerization and the fourth on cationic polymerization. In all of them the use of appropriate linking agents is necessary. 

V K. Singh, B. Thomas, Recent Developments in General Methodologies for the Synthesis of Linear Tri-quinanes, Tetrahedron 1998, 54, 3647-3692. 

This chapter presents an updated overview of the current status of the controlled polymer syntheses via the modem generation of cationic polymerizations that are mostly living or controlled what and how one can design and eventually synthesize novel polymers with well-defined structures and functionalities. Thus, the following sections are devoted to each of these classes of polymers (Fig. 2), with emphasis on the general methodologies and specific examples. The last section (Section VII) briefly covers the experimental procedures in living cationic polymerization and related polymer synthesis. 

In this section only the direct synthesis of 2,3-unsaturated sugars, in which the double bond is created will be presented. Numerous syntheses of these valuable compounds have been described in the literature. One of the most important classes of such derivatives are 2/3 -dideoxy-2, 3 -didehydronucleosides which possess a broad spectrum of biological activity. Two different approaches to 2, 3 -dideoxy-2, 3 -didehydro-thymidine (d4T) illustrate the general methodology of their preparation. 

The first case of an mrramolecular C-H carbenoid insertion was reported by Cane and Thomas in 1984 [12], with the special diazoacetate 17 forming the spirocyclic 5-lactone 18 in 45 % yield according to eq. (8). Doyle et al. recognized that this is a general methodology for the synthesis of y-butyrolactones [16], The reactivity of the C-H bond toward carbene insertion is increased in the vicinity of an ether functionality. Thus, the 3(2H)-furanone 20, as a useful building block in the total synthesis of (+)-muscarine, results in 40% yield from the diazo precursor compound 19 [17],... 

Tan, L., Yasuda, N., Yoshikawa, N., et al. (2005) Stereoselective syntheses of highly functionalized bicycle[3.1.0]hexanes A general methodology for the synthesis of potent and selective mGluR2/3 agonists. Journal of Organic Chemistry, 70, 8027-8034. 

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