Multifunctional Linkers for Combinatorial Solid Phase Synthesis

Acid-Stable Ester Linkers for the Solid-Phase Synthesis of Immobilized Peptides

A series of N-terminally Fmoc-protected linkers of the general formula Fmoc-X-CO-O-Y-COOH have been prepared, where X is -NH-CH₂ -CH₂ - or -p-(aminomethyl)phenyl- and Y is -(CH₂ )_n - (n is 1 or 4) or -p-(methyl)phenyl-. These linkers can easily be covalently attached via their C-terminal carboxyl group to a resin bearing a free amino group. After cleavage of the N-terminal Fmoc group, the linkers can be extended by standard solid-phase peptide synthesis techniques. These ester linkers are acid-stable and resistant to the base-mediated diketopiperazine formation that often occurs during the synthesis of ester-bound peptides; they are stable at neutral pH in aqueous buffers for days but can be effectively cleaved with 0.1 m NaOH or aq. ammonia within minutes or hours, respectively. These properties make these ester handles well suited for use as linkers for the solid-phase peptide synthesis of immobilized peptides when the stable on-resin immobilization of the peptides and the testing of their biological properties in aqueous buffers at neutral pH are necessary.

Solid phase syntheses of S,N-substituted 2-mercaptobenzoimidazoles

2-Mercaptobenzoimidazoles are an important class of heterocycles showing biological activity in diverse therapeutic applications.

Asymmetric solid-phase alkylation of ketones immobilized via SAMP hydrazone analogue linkers

The preparation and application of new solid supports with chiral linkers, analogues of SAMP hydrazine on solid-phase, are described. The supports were used for immobilization of ketones (diethylketone, cyclohexanone, 4- tert-butylcyclohexanone), and diastereoselective alkylation of formed chiral ketone hydrazones. The enantiomeric purities of cleaved alpha-alkylated chiral ketones ranged from 10 to 73%. The use of chiral lithium amides for metalation of hydrazones of t-butylcyclohexanone increased the enantiomeric excess of the alkylated product by 25-47%.