Oxyacyl resins

Hydroxy linkers bearing an electron-withdrawing group such as an a-carbonyl (oxyacyl resins, phenacyl type-linkers or glycolic acid derivatives) are also suitable for the nucleophilic release of ester bound compounds. The glycolamidic ester linker 10 has been successfully used to synthesize peptides by the Fmoc/tBu strategy. It is compatible with the repetitive piperidine treatment but peptides can be cleaved with dilute NaOH solutions, ammonia or alkoxides [9], Esters bound to oxyacyl resins 8 have been reported to be cleavable by thiolysis, saponification, ammonia, hydrazine and potassium cyanide (complexed with dicyclohexyl-18-crown-6) [10, 11],... 

The concept of naked anions, i.e. anions solubilized in non-solvating media by the crown complexation of their counter-cations, has been applied further this year. Naked fluoride ion has been used as a catalyst for Michael additions,such as the cyanoethylation of active methylene compounds, and also as a base to mediate the acylation (and protection) of the indole nitrogen of tryptophan in peptides. The selective cleavage of protected amino-acids from oxyacyl resins [equation (18)] is a... 

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See also in sourсe #XX -- [ ]

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