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Asymmetrische Synthesen mit chiralen 1,4‐Oxazin‐2,5‐dionen: Darstellung enantiomerenreiner 2‐substituierter Pipecolinsäurederivate
Author(s) -
Wanner Klaus Th.,
Stamenitis Stamatios
Publication year - 1993
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199319930179
Subject(s) - chemistry , stereocenter , electrophile , alkylation , stereochemistry , enantioselective synthesis , chiral auxiliary , deprotonation , hydrolysis , pipecolic acid , nucleophile , amino acid , organic chemistry , catalysis , ion , biochemistry
Asymmetric Synthesis with Chiral 1,4‐Oxazine‐2,5‐diones: Preparation of Enantiomerically Pure 2‐Substituted Pipecolic Acid DerivativesHerrn Prof. Dr. H.‐D. Stachel mit den besten Wünschen zum 65. Geburtstag gewidmet. A new asymmetric synthesis of α‐amino acids is presented. This synthesis is based on the chiral 1,4‐oxazine‐2,5‐diones 5 and 14 relying on the α‐hydroxy acid 12 as a chiral auxiliary. A base‐mediated alkylation of these chiral amino acid building blocks ( 5, 12 ) with different alkyl halides proceeds, after deprotonation with sec ‐butyllithium, with high yields and excellent d.s. (up to 99.5/0.5). As exemplified by the synthesis of 15 (in comparison to that of 7a ) the absolute configuration of the stereocenter in the amino acid unit is determined by the sequence the substituents are introduced. In the enolate 6 and in that of 14 the electrophile adds consistently to the re face of the prochiral carbon. From the alkylation products the corresponding 2‐substituted pipecolic acid derivatives are obtained in good yields upon hydrolysis under basic or acidic conditions.