Strategies convergent

The retrosynthetic analysis described above outlines a triply convergent strategy towards the synthesis of zaragozic acid A (1). The most pleasing aspect of the retrosynthetic strategy is the rapid and enantioselective manner in which the two-dimensional molecule... 

Examine the tetracycline synthesis on page 432 Does It follow a linear or convergent strategy ... 

Thorough analyses of linear and convergent strategies for tetraene (3) are given by Corey. His approach is for computer-based synthetic design but the logic is helpful to humans. This would be a good example to look... 

Coupling of aryl fluoride 8 and hydroxypyridine 9 provided a highly convergent strategy that allowed parallel preparation of the two fragments. 

A short and practical synthesis of glucokinase activator 1 was developed utilizing a convergent strategy involving an SNAr coupling of the activated aryl fluoride 11 with hydroxypyridine 9. 

Moss and Liao [182,183] reported a metallo-dendrimer built by a convergent strategy. An approach similar to that of Frechet was used to synthesize a fourth generation dendrimer containing 48 peripheral ruthenium atoms. 

In our group, several dendrimers based on ( R)-3-hydroxybutanoic acid (HB) have been prepared [56-58]. The dendrimers were synthesized by the convergent strategy. Trimesic acid has been used as core unit and the benzyl esters of the dimer and the tetramer of HB as elongation units. In such a way dendrimers of 1st and 2nd generation (27-30) have been constructed (Fig. 13). Since poly(.R)-3-hydroxybutanoic acid (PHB) is known to be biodegradable [59, 60] the stability of the dendrimers 27-30 was tested in the presence of PHB-de-... 

In continuing efforts, the same authors constructed tris(galactoside)-modified DAB dendrimers by the accelerated convergent strategy. In this particular approach, the saccharides were connected first to a small TRIS branching derivative to form a cluster which served as a building block, once suitably functionalized.417 N-Succini-midyl-activated ester 561 was then coupled onto G(l) and G(2)-PPI dendrimers with... 

SCHEME 64. Convergent strategy for the construction of glucosylated dendrimers using TRIS as the branching component.229... 

Especially, the divergent and convergent strategies have been applied to many dendrimer syntheses. Nowadays, there are dendrimers with branching units which are based on silicon, phosphorus and other heteroatoms,1101 dendrimers which are built up supramolecularly (rather than covalently)1111 and even pure hydrocarbon dendrimers.112,131 A dendrimer of the tenth generation with 3072 gold ions at its periphery, which is 15 nanometers in diameter, has been prepared successfully by Majoral et al.1101... 

The main efforts in the field of synthetic carbohydrate chemistry have been focusing on the development of new glycosylation methodologies and convergent strategies for... 

Many examples of the convergent strategy (b) can be found in contemporary approaches to natural products synthesis. Usually the routes to target molecules (e.g. I) are derived by retro-synthesis from the final product [6]. This involves transformation of the target molecule to lower molecular weight precursors (e.g. A-F). 

While the convergent strategy, as described above, has been exceptionally successful, a considerable amount of effort has been devoted to improving its speed and synthetic efficiency. The remainder of this chapter reviews the major methodological developments and improvements in the accelerated, covalent, convergent synthesis of dendrimers. Dendrimers constructed via self-assembly and noncovalent interactions, as well as inorganic dendrimers [25], are beyond the scope of this brief chapter. 

Hydroaminomethylation is also be used for the construction of den-drimers [64], Here divergent and convergent strategies with wide variabilities can be used. A selected example is shown in Scheme 17. 

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