Theoretical evidence for pyramidalized bicyclic serine enolates in highly diastereoselective alkylations.
A new chiral serine equivalent and its enantiomer have been synthesized from (S)- and (R)-N-Boc-serine methyl esters (Boc: tert-butyloxycarbonyl). The use of these compounds as chiral building blocks has been demonstrated in the synthesis of alpha-alkyl alpha-amino acids by diastereoselective potassium enolate alkylation reactions and subsequent acid hydrolyses. Theoretical studies were performed to elucidate the stereochemical outcome of both the formation of five-membered cyclic N,O-acetals and the subsequent alkylation process, which occurs with total retention of configuration. This feature could be explained in terms of the high degree of pyramidalization of enolate intermediates.
Aydillo
Carlos
C
Departamento de Química, Universidad de La Rioja, UA-CSIC, 26006 Logroño, Spain.
Jiménez-Osés
Gonzalo
G
Busto
Jesús H
JH
Peregrina
Jesús M
JM
Zurbano
María M
MM
Avenoza
Alberto
A
D000080:Acetals / Q000138:chemical synthesis / Q000737:chemistry; D000478:Alkylation; D000596:Amino Acids / Q000138:chemical synthesis / Q000737:chemistry*; D001643:Bridged Bicyclo Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry*; D006868:Hydrolysis; D015394:Molecular Structure; D010080:Oxazoles / Q000138:chemical synthesis / Q000737:chemistry*; D012694:Serine / Q000031:analogs & derivatives / Q000737:chemistry; D013237:Stereoisomerism
D000080:Acetals; D000596:Amino Acids; D001643:Bridged Bicyclo Compounds; D004952:Esters; D010080:Oxazoles; D012694:Serine; C429009:serine methyl ester