Protection cyclopentyl esters

Cyclopentyl ester [50715-28-1]. Cyclopentyl chloroformate. /V-Protecting reagent for amino acids. Bp25 69-70.5 . 

The cyclopentyl (cPe) ester group was introduced by Blake for the protection of carboxy groups. The ester bond is stable against TFA and readily cleaved with HF at 0 °C. This ester is 14 times more stable than the corresponding benzyl ester when exposed to 55% TFA in dichloromethane. However, there is little difference in the extent of HF-catalyzed succini-mide formation between peptidyl-resins containing benzyl- or cyclopentyl-protected aspartyl residues, although the latter protection reduces base-catalyzed succinimide formation. 

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