Synthesis double-stage convergent

Recently, new methods such as orthogonal synthesis, double-stage convergent method, double-exponential method, hypermonomer method, and click chemistry have been disclosed for synthesis of dendrimers [5]. 

H. Ihre, A. Hult, J. M. J. Frechet, and I. Gitsov, Double-stage convergent approach for the synthesis of functionalized dendritic aliphatic polyesters based on 2,2-bis(hydroxymethyl)propionic acid, Macromolecules, 31 (1998) 4061 1068. 

Scheme 5.4. Synthesis of dendritic wedges to be used in double stage convergent growth .

Figure 33.5 Double-stage convergent strategy for dendrimer synthesis.

Polyphenolic dendrimers A double stage convergent synthesis is described a hypercore based on 4,4- bis(4 -hydroxyphenyl)pentanol. [134]... 

S.M. Weinreb and co-workers were surprised to find that the convergent stereoselective synthesis of marine alkaloid lepadiformine resulted in a product that gave a totally different NMR spectra than the natural product. This finding led to the revision of the proposed structure of lepadiformine. In the final stages of the synthesis, they exposed a tricyclic piperidone intermediate to Ciemmensen conditions to remove the ketone functionality. Under these conditions the otherwise minor elimination product (alkene) was formed predominantly however, it was possible to hydrogenate the double bond to give the desired alkane. 

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