Asymmetric Synthesis of .alpha.-Amino Acids by Copper-Catalyzed Conjugate Addition of Grignard Reagents to Optically Active Carbamatoacrylates
作者:Peter A. Lander、Louis S. Hegedus
DOI:10.1021/ja00097a020
日期:1994.9
Optically active ene carbamates were alpha-lithiated by lithium tetramethylpiperidide in the presence of trialkylstannyl chlorides to produce alpha-stannylated compounds. These underwent facile palladium-catalyzed couplings with acid chlorides to produce alpha-keto ene carbamates in good yield. Treatment of the alpha-stannyl ene carbamates with butyllithium followed by quenching with carbon dioxide and esterification gave optically active carbamatoacrylates. Copper-catalyzed addition of tert-butyl-, 1-naphthyl-, 2-propenyl-, p-methoxyphenyl-, (trimethylsilyl)methyl-, cyclohexyl-, 1-adamantyl-, and isopropyl Grigard reagents followed by quenching at -10 to 25 degrees C and removal of the protecting groups gave the corresponding alpha-amino acids in 70-90% yield and 73-97% ee. Quenching the reaction at low temperature resulted in little if any asymmetric induction.
Asymmetric syntheses of α-amino acids from α-halogenated 10-sulfonamido-isobornyl esters.
Synthesis and Biological Properties of Enkephalin-like Peptides Containing Adamantylalanine in Position 4 and 5
作者:Kim Quang Do、Robert Schwyzer
DOI:10.1002/hlca.19810640713
日期:1981.11.4
show pronounced morphine-like activities in certain bioassays, whereas those with X = Ada were most inactive. The analogues were used to explore the influence of steric, electronic, and hydrophobic properties of the side chains of X and Y on opioid activity (see [14]).