41041-70-7Relevant academic research and scientific papers
Oxidation-induced Acyl group transfer from hydroquinone esters to nucleophiles
Reischl, Gerald,El-Mobayed, Medhat,Bei?wenger, Rudolf,Regier, Klaus,Maichle-M?ssmer, C?cilia,Rieker, Anton
, p. 765 - 773 (2007/10/03)
Bivalent oxidation of 3,5-di-tert-butyl-hydroquinone monoesters leads to phenoxenium ions, which can transfer an acyl group to nucleophiles. Based on this principle, dipeptides, glyco-amino acids and N-sulfonyl-amino acids were synthesized from hydroquino
Transesterifications with 1,8-Diazabicycloundec-7-ene/Lithium Bromide (DBU/LiBr) - Also Applicable to Cleavage of Peptides from Resins in Merrifield Syntheses
Seebach, Dieter,Thaler, Adrian,Blaser, Denis,Ko, Soo Y.
, p. 1102 - 1118 (2007/10/02)
A mixture of the amidine base 1,8-diazabicycloundec-7-ene (DBU) and LiBr (preferably 0.5 and 5 equiv., resp.) turns out to be a highly efficient catalyst (at 0-25 deg C) for saponifications (in THF/H2O) and transesterifications (in ROH).The scope and limitations of the method are determined using ca. two dozens of different ester/alcohol combinations (Schemes 2 and 3).The investigation is focused on peptides as substrates.Under carefully controlled conditions, no epimerization occurs with N-Boc- and N-Z-protected peptide esters, when methyl, ethyl, isopropyl, or allyl esters are the products, as shown for peptides containing up to six amino acids, with Ala, Leu, MeLeu, Asp(OEt), or Tyr at the C-terminus (Scheme 3 and Tables 1 and 2).Hydrolytic and transesterifying detachments of Boc-Leu-Ala-Gly-Val-OR and Boc-Leu-Ala-Gly-Phe-OR (R = H, Me) from PAM and Wang resins (1-8 h at 0-25 deg C, 2 equiv. of DBU, 5 equiv. of LiBr) can be achieved by this method without epimerization of the C-terminal stereogenic center; a comparison with other methods (HF, Ti(OR)4) is given (Schemes 4 and 5).Possible protecting-group strategies involving the DBU/LiBr method are discussed (Table 3).Extensive experimental details are given.
ENANTIOSELECTIVE SYNTHESIS OF PEPTIDES USING (1R)-3-HYDROXY-1,8,8-TRIMETHYL-3-AZABICYCLOOCTANE-2,4-DIONE ((+)-N-HYDROXYCAMPHORIMIDE) AN ACTIVE ESTER GROUP
Takeda, Kazuyoshi,Tsuboyama, Kanoko,Suzuki, Akira,Ogura, Haruo
, p. 2545 - 2548 (2007/10/02)
The enantioselective coupling reaction of N-protected amino acid (+)-N-hydroxycamphorimide esters (-OCamp) with racemic amino acid esters is discussed.The coupling reaction of several amino acids showed high enantioselectivity.Keywords-enantioselective synthesis; (+)-N-hydroxycamphorimide; peptide, active ester; coupling reaction
