Knorr resin

Rink- acetic acid -amide, Knorr resin... 

Reductive alkylation of RAM resin 7c using aldehydes or ketones provides a route to resin-bound secondary amines that is an alternative to the reductive amination of aldehyde resins discussed in Section III. After acylation, secondary amides can be cleaved from the support using TFA-CH2CI2 (1 19) [284]. Ileductive alkylation of the Knorr resin by aldehydes has also been reported. The products were further alkylated and the resulting tertiary amines could be cleaved directly from the support using TFA-CH2CI2 (1 1) [285]. 

Needing 2,5-dimethylfuran as a masked 1,4-dicarbonyl equivalent, Scott and Naples found that the ion-exchange resin Amberlyst 15 is extremely effective in catalyzing the cyclization of hexane-2,5-dione to this compound.31 Some unusual Paal-Knorr reactions have been described. In one, phos-phorus(V) sulfide gave none of the expected thiophene when it acted upon the diketoester 3, the thioester 4 being obtained instead.32 Against all... 

O-o-V"1 gA° R X.H.C R 0 NH2 [52] Amides of different types are produced to form peptido-mimetics and/or peptoids. Not only condensation reactions but also alkylation and substitution reactions are described. Resins/linkers used Wang, Rink amide, Knorr TenlaGel. Phosphoramides were prepared on Pore glass, 3 split-pool libraries. [21] [50-57]... 

A wide range of benzhydryl-based linkers bearing additional electron-donating functionalities has also been developed for Fmoc SPPS of peptide amides, the most popular of which are the eponymous Rink amide (7) [13] and Knorr linkers 24 [65]. Primary amides prepared on this resin can be cleaved with TFA in the same manner as previously described for the PAL linker. 

Because of the origins of solid phase chemistry in peptide synthesis, amide formation is historically one of the most important reactions on solid supports. The most pubUc resins are the Rink amide linker 123 [146,147] and its derivatives that are formed by addition of the Knorr hnker [148] to polystyrene-derived resins. 

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