Allylic alkylations catalyzed by the couple palladium complexes-alumina
作者:D. Ferroud、J.P. Genet、J. Muzart
DOI:10.1016/s0040-4039(01)81443-x
日期:1984.1
Using both palladium complexes and alumina, nucleophilic substitution of allyl acetate by various nucleophiles (pKa = 5–13) are realized with good yields at room temperature without preformation of the corresponding carbanions.
Sterically Hindered <i>C</i><sup>α</sup><sup>,</sup><sup>α</sup>-Disubstituted α-Amino Acids: Synthesis from α-Nitroacetate and Incorporation into Peptides
作者:Yanwen Fu、Lars G. J. Hammarström、Tod J. Miller、Frank R. Fronczek、Mark L. McLaughlin、Robert P. Hammer
DOI:10.1021/jo015809o
日期:2001.10.1
demanding C(alpha,alpha)-dibenzylglycine (Dbg) has been incorporated into a peptide using solid-phase synthesis. It was found that once sterically congested Dbg is at the peptide N-terminus, further chain extension becomes very difficult using uronium or phosphonium salts (PyAOP, PyAOP/HOAt, HATU). However, preformed aminoacid symmetrical anhydride couples to N-terminal Dbg in almost quantitative yield
Without prior activation of allyl alcohols, allylation of a variety of active methylene compounds with allyl alcohols proceeds smoothly at rt-50degreesC in the presence of catalytic amounts of Pd(OAc)(2) (1-10mol%), Et3B (30-240 mol%), a phosphine ligand (1-20 mol%), and a base (0 to 50-60 mol%). (C) 2003 Elsevier Ltd. All rights reserved.
Facile Synthesis of α,α-Diisobutylglycine and Anchoring Its Derivatives onto PAL-PEG-PS Resin
作者:Yanwen Fu、Marcus A. Etienne、Robert P. Hammer
DOI:10.1021/jo034885j
日期:2003.12.1
alpha,alpha-Diisobutylglycine has been synthesized using a Pd-mediated dialkylation of ethyl nitroacetate as a key first step. The free alphaalphaAA is N-alpha-protected and has been applied to the assembly of conformationally constrained peptide analogues. Mixed anhydrides from BOP-Cl and Fmoc-alphaalphaAA-OH are used for anchoring alphaalphaAAs onto a trialkoxybenzyl linker on PEG-PS grafted support, upon which a beta-strand mimic with difficult sequence is assembled in a superior quality.