Selective Enzymatic Removal of Protecting Groups from Phosphopeptides: Chemoenzymatic Synthesis of a Characteristic Phosphopeptide Fragment of the Raf-1 Kinase
N-protected α-amino acids are readily coupled with α-aminoacyl esters by polystyryl diphenylphosphine-iodine complex in very high yields and without detectable racemization. Protecting groups of general use for both amine and carboxyl functions, as well as the common side-chain-function protecting groups, are well tolerated under our experimental conditions. The workup is very easy since the only byproduct formed is a polymer-linked phosphine oxide that is simply filtered off to achieve the coupling product.
The effect of various alcohols as vehicles on skin permeability was compared for unmodified ibuprofen (IBU) and ion pairs of ibuprofen with L-valine alkyl esters [ValOR][IBU], in which the alkyl chain R was changed from C1 to C8. In vitro permeation experiments were conducted in a Franz cell with porcine skin. Methanol, ethanol, and isopropanol solutions of 70% (v/v) were chosen as vehicles for penetrants
Selective Enzymatic Removal of Protecting Groups from Phosphopeptides: Chemoenzymatic Synthesis of a Characteristic Phosphopeptide Fragment of the Raf-1 Kinase
作者:Dagmar Sebastian
DOI:10.1055/s-1997-1306
日期:1997.9
Base-labile biologically relevant phosphopeptides can advantageously be synthesized under very mild conditions and without undesired side reactions by employing the heptyl (Hep) ester as C-terminal or the phenylacetamide (PhAc) as N-terminal enzyme-labile protecting group. The lipase-mediated saponification of the heptyl ester blocking function was successfully applied in the construction of a characteristic selectively phosphorylated hydroxyamino acid fragment of Raf-1 kinase, an important member of the so-called Ras signal transduction pathway.