3275-37-4Relevant articles and documents
Asymmetric synthesis of α-methyl-α-amino acids via diastereoselective alkylation of (1s)-(+)-3-carene derived tricyclic iminolactone
Lu, Ta-Jung,Lin, Cheng-Kun
experimental part, p. 1621 - 1633 (2011/06/17)
A novel carene-based alanine-equivalent tricyclic iminolactone 16 has been synthesized via stereoselective dihydroxylation of the double bond, IBX oxidation of the secondary alcohol, esterification of the tertiary alcohol, deprotection of the resulting ester, and subsequent cyclization from commercially available (1S)-(+)-3-carene in 79% overall yield. The iminolactone 16 demonstrated high reactivity toward alkylation with a wide range of electrophiles at room temperature under phasetransfer catalysis conditions. The alkylated products were produced with excellent diastereoselectivities (>98% de) in good isolated yields (86-94%). High yields (83-91%) of optically pure (S)-R-methyl-R-substituted-R-amino acids were obtained by basic hydrolysis of the dialkylated iminolactones with the recovery of the chiral auxiliary 15 (78-87%).
Stereoselective Alkylation of Dianions derived from Chiral Half-Esters of Monosubstituted Malonic Acids: Asymmetric Synthesis of α-Alkyl α-Amino Acids and Key Synthetic Intermediates for Hunteria and Aspidosperma Indole Alkaloids
Ihara, Masataka,Takahashi, Masanobu,Taniguchi, Nobuaki,Yasui, Ken,Niitsuma, Hiroko,Fukumoto, Keiichiro
, p. 525 - 535 (2007/10/02)
Substitution of the chiral half-esters of monosubstituted malonic acids with halides leads to the formations of mixtures of the diastereomeric alkyl- or benzyl-malonic half-esters.The (R)-isomers (13A and 15A-22A) were obtained from the phenylmenthyl half-ester 14 of methylmalonic acid in high diastereoisomeric excess.The same stereoisomers were also produced by reaction of the half-esters 9, 23 and 24 with methyl iodide.Their absolute configurations were determined by transforming the major products into the known α-alkyl α-amino acid derivatives 30, 33 and 35.The major product 43, prepared by allylation of the half-ester 9, was converted into two lactones 41 and 42, key intermediates for synthesis of indole alkaloids of the Hunteria and Aspidosperma types.The mechanism of the above alkylation is discussed.
