Asymmetric PTC C-Alkylation Catalyzed by Chiral Derivatives of Tartaric Acid and Aminophenols. Synthesis of (R)- and (S)-α-Methyl Amino Acids
- 22 September 2000
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 65 (21) , 7041-7048
- https://doi.org/10.1021/jo000719p
Abstract
A new type of efficient chiral catalyst has been elaborated for asymmetric C-alkylation of CH acids under PTC conditions. Sodium alkoxides formed from chiral derivatives of tartaric acid and aminophenols (TADDOL's 2a−e and NOBIN's 3a−h) can be used as chiral catalysts in the enantioselective alkylation, as exemplified by the reaction of Schiff's bases 1a−e derived from alanine esters and benzaldehydes with active alkyl halides. Acid-catalyzed hydrolysis of the products formed in the reaction afforded (R)-α-methylphenylalanine, (R)-α-naphthylmethylalanine, and (R)-α-allylalanine in 61−93% yields and with ee 69−93%. The procedure could be successfully scaled up to 6 g of substrate 1b. When (S,S)-TADDOL or (R)-NOBIN are used, the (S)-amino acids are formed. A mechanism rationalizing the observed features of the reaction has been suggested.Keywords
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