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Practical Synthesis of Natural Amino Acid Derivatives: Hf(OTf)4-Catalyzed Mannich-Type Reaction of Ketene Silyl Acetals or Enol Silyl Ethers with N,O-Acetals as a Glycine Cation Equivalent

Norio Sakai*, Asuka Sato, Takeo Konakahara

*Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science (RIKADAI), Noda, Chiba 278-8510, Japan, Email:

N. Sakai, A. Sato, T. Konakahara, Synlett, 2009, 1449-1452.

DOI: 10.1055/s-0029-1216743


The Hf(OTf)4-catalyzed Mannich-type reaction of an enol silyl ether or a ketene silyl acetal with an N,O-acetal allows the preparation of amino acid derivatives. In particular, use of the N,O-acetal having a bis(trimethylsilyl)amino group directly produced N-unprotected aspartic acid derivatives after a standard aqueous workup.

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Key Words

Mannich-type reaction, N,O-acetals, α-amino acids, β-amino acids, hafnium triflate

ID: J60-Y2009-1670